Systems and methods for enhancing fluorescent detection of target molecules in a test sample

FIELD OF THE INVENTION

The present invention relates generally to the field of fluorescent detection, and more particularly, to systems and methods for enhancing fluorescent detection of target molecules in a test sample.

BACKGROUND OF THE INVENTION

Biomolecular assays may typically have required a readout signal to determine the success or failure of the experiment. Typically, for example, in prior art biomolecular sandwich assays, the analytes or target molecules to be detected may have been bound between biorecognition molecules (BRMs) and marker molecules. In the past, a positive result (and thus detection of the presence of the target molecule) may have been determined by detection of the readout signal, which in some cases may have been a fluorescent signal. The fluorescent signal may heretofore have been produced by excitation of a fluorophore bound to the marker molecule, such that the fluorophore emitted photons in the visible spectrum (i.e., as the fluorescent signal). <nplcit id="ncit0001" npl-type="s"><text>Marti et al Tetrahedron (2007) vol.63 pg 3591-3600</text></nplcit> describes fluorescent labeled oligonucleotide probes. <patcit id="pcit0001" dnum="US6340588B"><text>US6340588</text></patcit> describe matrices incorporating fluorescent labels.

Exemplary prior art biomolecular sandwich assays may have included genomic assays, where the BRMs may have been single-stranded DNA immobilized on the surface of a substrate (e.g., a microbead). Similarly, the marker molecules may have included single-stranded marker DNA bound to one or more fluorophores. In operation, such prior art genomic assays may have involved a first hybridization reaction between the BRMs and the target molecules, if present. (The target molecules may have included single-stranded target DNA of interest in the experiment.) Thereafter, such prior art genomic assays may have involved a second hybridization reaction between the marker molecules and the target molecules, if present.

Other exemplary prior art biomolecular sandwich assays may have included immunoassays, where the BRMs may heretofore have been first antibody molecules immobilized on a substrate. Similarly, the marker molecules may heretofore have been second antibody molecules (alternately, "marker antibodies") bound to one or more fluorophores. In operation, such prior art immunoassays may have involved a first reaction between the BRMs and the target molecules, if present. (The target molecules may have included target antigen molecules, or analytes, of interest in the experiment.) Thereafter, such prior art immunoassays may have involved a second reaction between the marker antibodies and the target antigen molecules, if present.

In the past, it may generally have been thought that molecular fluorophores can provide useful and/or sensitive methods for the detection of binding events in biomolecular assays. Such molecular fluorophores may heretofore have been used, when bound, to provide a fluorescent readout signal. It may generally have been thought that suitable molecular fluorophores might include, for example, fluorescein, rhodamine dyes, or ALEXA FLUOR® series dyes (such as those manufactured by Molecular Probes, Inc. of Eugene, Oregon). More recently, quantum dots (QDs) may have been considered for potential uses as fluorophores. <nplcit id="ncit0002" npl-type="s"><text>Neogi et al, Meter. Res. Soc. Symp. Proc vol.959(1) 2007 pg 202-207</text></nplcit> describe the use of quantum dot based system for FRET analysis. <nplcit id="ncit0003" npl-type="s"><text>Bakalova et al Journal of the American Chemical Society (2005) vol. 127 pg 11328-11335</text></nplcit> describes RNA strands conjugated with a quantum dot for use as a hybridization probes.

It may heretofore have been generally thought that assay sensitivity, and the ability to detect fluorescent readout signals, depends on an ability to observe an emission from a chosen marker fluorophore. Accordingly, much assay sensitivity research to date may have been largely aimed at increasing the ability to observe emissions from chosen marker fluorophores. Related developments may heretofore have, therefore, included highly sensitive photomultiplier tubes, more efficient photon collection optics, and/or the use of microfluidic systems. One or more of these developments may have sought to maximize detection sensitivity for very low fluxes of photons, possibly as might be emitted from a small area in a microarray or microbead biomolecular assay.

It may now be believed (though it is not essential to the working of the present invention) that the sensitivity in detecting fluorescent readout signals, and indeed assay sensitivity as a whole, may also depend upon an ability to excite the chosen marker fluorophores. Assay detection sensitivity may, therefore, yet be improved by improving the ability to excite the chosen marker fluorophores. Accordingly, it may be desirable to provide an improved method and system for local excitation of specific fluorophores.

It may be thought, though it may not be essential to the working of the present invention, that fluorescent molecules or QDs enter an electronically "excited state" before they are capable of emitting one or more detectable photons in the visible spectrum. It is also believed, though it is not essential to the working of the present invention, higher percentages of excited molecules in a population may lead to a higher absolute number of (detectable) photons being emitted. Although not necessary to the working of the present invention, it may be thought that an increase in the total number of electronically excited fluorophore molecules may directly increase the assay's detection sensitivity to that population of molecules.

Various techniques may heretofore have been used to produce molecular excitation, including the use of thermal energy (heat), electrical stimulation, and/or light absorption. When an emission of a fluorescent signal is the desired effect, the use of light absorption may be a particularly efficient method for exciting molecular fluorophores.

Previously, lasers may have been used to excite fluorophores. Lasers can be relatively intense sources of light and may, therefore, be efficient at exciting molecular dyes. Lasers may, however, emit very narrow bandwidths of visible light, having a specific single polarization. As such, lasers may not be as efficient at exciting random orientations of molecular fluorophores as might be desired.

Now, in biomolecular sandwich assays, it may be advantageous for both the microbeads and the marker molecules to emit fluorescent readout signals in a test positive scenario. In such a contemplated situation, multiple wavelengths of incident light might heretofore have been required to adequately excite both the microbead fluorophores and the marker fluorophores.

Accordingly, there may be a need to provide an improved ability to excite bound fluorophores, and/or to provide for increased numbers of excited bound fluorophores.

There may also be a need to provide an improved ability to excite fluorophores, and/or to provide for increased numbers of excited fluorophores, bound at various orientations.

There may also be a need to provide for an enhanced emission from fluorophores by controllable localized excitation.

It is an object of a preferred embodiment according to the present invention to provide a system and/or method for enhancing fluorescent detection of target molecules.

It is an object of one preferred embodiment according to the present invention to provide a system and/or method for enhancing fluorescent detection of target molecules in a microbead assay.

It is an object of a preferred embodiment according to the present invention to provide a system and/or method which excites the BRM or marker fluorophores (preferably, the marker fluorophores) via a fluorescent signal emitted from the other (preferably, from the BRM fluorophores).

It is also an object of one preferred embodiment according to the present invention to provide a system and/or method which advantageously tailors an emission profile and/or an intensity of one or more QDs to provide for, and/or control, localized excitation of one or more other immobilized fluorophores in the assay.

It is an object of the present invention to obviate or mitigate one or more of the aforementioned disadvantages associated with the prior art, and/or to achieve one or more of the aforementioned objects of the invention.

SUMMARY OF THE INVENTION

According to the invention, there is disclosed a method of enhancing fluorescent detection of target molecules in a test sample. The method is for use with an irradiating device. The method includes a step of (a) providing one or more first fluorophores operatively adapted for absorption of electromagnetic frequency (EMF) radiation, and for emission of a first fluorescent signal following absorption of the EMF radiation wherein the first fluorophores are bound by microbeads and the first fluorophores are characterized by a first fluorophore emission profile corresponding to the first fluorescent signal. The method also includes a step of (b) providing biorecognition molecules (BRMs) adapted to operatively bind with the microbeads and the target molecules, so as to secure the first fluorophores relative to the target molecules if present in the test sample. The method also includes a step of (c) providing one or more second fluorophores bound to marker molecules; wherein the marker molecules are adapted to operatively bind with the target molecules, so as to secure the second fluorophores relative to the target molecules if present in the test sample and wherein the second fluorophores are operatively adapted for absorption of a first incident portion of the first fluorescent signal, and for emission of a second fluorescent signal following absorption of the first incident portion. The second fluorescent signal is distinguishable from the first fluorescent signal. The second fluorophores are characterized by a second fluorophore absorption profile which substantially overlaps with the first fluorophore emission profile. The first fluorophores and the second fluorophores are adapted for operative combination with the test sample, and for securement relative to the target molecules, if present in the test sample, so as to secure the first fluorophores relative to the second fluorophores. Following operative irradiation of at least the first fluorophores with the EMF radiation via the irradiating device, the first fluorophores emit the first fluorescent signal. If the target molecules are present in the test sample, the second fluorophores absorb the first incident portion of the first fluorescent signal and emit the second fluorescent signal. Thus, the first spectral signal is operatively detectable, together with the second spectral signal if the target molecules are present in the test sample.

According to an aspect of one preferred embodiment of the invention, preferably in step (a), the first fluorophore emission profile may preferably, but need not necessarily, be characterized by a peak intensity at a wavelength of about 580 nanometers (nm).

According to an aspect of one preferred embodiment of the invention, preferably in step (a), the first fluorophores may preferably, but need not necessarily, be characterized by a first fluorophore absorption profile, preferably substantially corresponding to the EMF radiation. Preferably in step (c), the second fluorophores may preferably, but need not necessarily, be characterized by a second fluorophore emission profile, preferably corresponding to the second fluorescent signal, which may preferably be substantially removed from the first fluorophore absorption profile.

According to an aspect of one preferred embodiment of the invention, preferably in step (b), the BRMs may preferably, but need not necessarily, include one or more antibody molecules.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, be for detection of one or more single-stranded target DNA molecules as the target molecules. Preferably in step (b), the BRMs may preferably, but need not necessarily, include one or more single-stranded biorecognition DNA molecules complementary to, and/or adapted to operatively hybridize with, the target DNA molecules.

According to an aspect of one preferred embodiment of the invention, preferably in step (a), the first fluorophores may preferably, but need not necessarily, include quantum dots of one or more quantum dot types.

According to an aspect of one preferred embodiment of the invention, preferably in step (a), the intensity of the first spectral signal may preferably, but need not necessarily, be dependent upon the number of the quantum dots bound by each of the microbeads.

According to an aspect of one preferred embodiment of the invention, preferably in step (a), the color of the first spectral signal may preferably, but need not necessarily, be dependent upon the size of the quantum dot types bound by each of the microbeads.

According to an aspect of one preferred embodiment of the invention, preferably in step (c), the marker molecules may preferably, but need not necessarily, include one or more antigen molecules.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, be for detection of one or more single-stranded target DNA molecules as the target molecules. Preferably in step (c), the marker molecules may preferably, but need not necessarily, include one or more single-stranded marker DNA molecules complementary to, and/or adapted to operatively hybridize with, the target DNA molecules.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, be for use with a laser as the irradiating device. Preferably in step (a), the EMF radiation may preferably, but need not necessarily, have a wavelength of about 488 nanometers (nm).

According to an aspect of one preferred embodiment of the invention, preferably following operative combination of the first fluorophores and/or the second fluorophores with the test sample, the target molecules, if present in the test sample, may preferably secure the second fluorophores within a predetermined maximum range of the first fluorophores. A radiative flux of the first spectral signal may preferably, but need not necessarily, be substantially unabated over the predetermined maximum range.

According to an aspect of one preferred embodiment of the invention, the predetermined maximum range may preferably, but need not necessarily, be dependent upon the first fluorophores, preferably as provided in step (a). The predetermined maximum range may preferably, but need not necessarily, be less than about 10 micrometers (µm).

According to an aspect of one preferred embodiment of the invention, preferably in step (c), the second fluorophores may also preferably, but not necessarily, be operatively adapted for absorption of the EMF radiation, and/or for emission of the second fluorescent signal following absorption of the EMF radiation.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, also include step (e), preferably after step (c), of operatively combining the first fluorophores with the test sample and/or the second fluorophores.

According to an alternate aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, include alternate step (e), preferably after step (c), of operatively combining the microbeads with the BRMs, the test sample, and/or the second fluorophores.

According to another alternate aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, include another alternate step (e), preferably after step (c), of operatively combining the first fluorophores with the test sample, the marker molecules, and/or the second fluorophores.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, also include step (f), preferably after step (e), of operatively irradiating at least the first fluorophores with the EMF radiation, preferably via the irradiating device.

According to an aspect of one preferred embodiment of the invention, preferably in step (b), the second fluorophores may also preferably, but not necessarily, be operatively adapted for absorption of the EMF radiation, and/or for emission of the second fluorescent signal following absorption of the EMF radiation. According to this aspect of the invention, the method may preferably, but need not necessarily, also include alternate step (f), preferably after step (e), of operatively irradiating the first fluorophores and/or the second fluorophores with the EMF radiation, preferably via the irradiating device.

According to an aspect of one preferred embodiment of the invention, the method may preferably, but need not necessarily, also include step (g), preferably after step (f), of operatively detecting the first spectral signal, preferably together with the second spectral signal if the target molecules are present in the test sample.

According to the invention, there is also disclosed a system for enhancing fluorescent detection of target molecules in a test sample. The system is for use with an irradiating device. The system includes one or more first fluorophores operatively adapted for absorption of electromagnetic frequency (EMF) radiation, and for emission of a first fluorescent signal following absorption of the EMF radiation wherein the first fluorophores are bound by microbeads and are characterized by a first fluorophore emission profile corresponding to the first fluorescent signal. The system also includes one or more second fluorophores operatively adapted for absorption of a first incident portion of the first fluorescent signal, and for emission of a second fluorescent signal following absorption of the first incident portion. The second fluorescent signal is distinguishable from the first fluorescent signal. The second fluorophores are characterized by a second fluorophore absorption profile which substantially overlaps with the first fluorophore emission profile. The system also includes biorecognition molecules (BRMs) adapted to operatively bind with the microbeads and the target molecules, so as to secure the first fluorophores relative to the target molecules if present in the test sample. The system also includes marker molecules adapted to operatively bind with the second fluorophores and the target molecules, so as to secure the second fluorophores relative to the target molecules if present in the test sample. The first fluorophores and the second fluorophores are adapted for operative combination with the test sample, and for securement relative to the target molecules, if present in the test sample, so as to secure the first fluorophores relative to the second fluorophores. Following operative irradiation of at least the first fluorophores with the EMF radiation via the irradiating device, the first fluorophores emit the first fluorescent signal and, if the target molecules are present in the test sample, the second fluorophores absorb the first incident portion of the first fluorescent signal and emit the second fluorescent signal. Thus, the first spectral signal is operatively detectable, together with the second spectral signal if the target molecules are present in the test sample.

According to an aspect of one preferred embodiment of the invention, the first fluorophore emission profile may preferably, but need not necessarily, be characterized by a peak intensity at a wavelength of about 580 nanometers (nm).

According to an aspect of one preferred embodiment of the invention, the first fluorophores may preferably, but need not necessarily, be characterized by a first fluorophore absorption profile, preferably substantially corresponding to the EMF radiation. The second fluorophores may preferably, but need not necessarily, be characterized by a second fluorophore emission profile, preferably corresponding to the second fluorescent signal, which may preferably be substantially removed from the first fluorophore absorption profile.

According to an aspect of one preferred embodiment of the invention, the BRMs may preferably, but need not necessarily, include one or more antibody molecules.

According to an aspect of one preferred embodiment of the invention, the system may preferably, but need not necessarily, be for detection of one or more single-stranded target DNA molecules as the target molecules. The BRMs may preferably, but need not necessarily, include one or more single-stranded biorecognition DNA molecules complementary to, and/or adapted to operatively hybridize with, the target DNA molecules.

According to an aspect of one preferred embodiment of the invention, the first fluorophores may preferably, but need not necessarily, include quantum dots of one or more quantum dot types.

According to an aspect of one preferred embodiment of the invention, the intensity of the first spectral signal may preferably, but need not necessarily, be dependent upon the number of the quantum dots bound by each of the microbeads.

According to an aspect of one preferred embodiment of the invention, the color of the first spectral signal may preferably, but need not necessarily, be dependent upon the size of the quantum dot types bound by each of the microbeads.

According to an aspect of one preferred embodiment of the invention, the marker molecules may preferably, but need not necessarily, include one or more antigen molecules.

According to an aspect of one preferred embodiment of the invention, the system may preferably, but need not necessarily, be for detection of one or more single-stranded target DNA molecules as the target molecules. The marker molecules may preferably, but need not necessarily, include one or more single-stranded marker DNA molecules complementary to, and/or adapted to operatively hybridize with, the target DNA molecules.

According to an aspect of one preferred embodiment of the invention, the second fluorophores may preferably, but need not necessarily, be adapted to be operatively secured substantially adjacent to distal end portions of the marker DNA molecules.

According to an aspect of one preferred embodiment of the invention, the second fluorophores may preferably, but need not necessarily, include one or more fluorescent dyes.

According to an aspect of one preferred embodiment of the invention, the fluorescent dyes may preferably, but need not necessarily, include Cyanine-5 (Cy5) molecular dyes.

According to an aspect of one preferred embodiment of the invention, the system may preferably, but need not necessarily, be for use with a laser as the irradiating device. The EMF radiation may preferably, but need not necessarily, have a wavelength of about 488 nanometers (nm).

According to an aspect of one preferred embodiment of the invention, preferably following operative combination of the first fluorophores and/or the second fluorophores with the test sample, the target molecules, if present in the test sample, may preferably secure the second fluorophores within a predetermined maximum range of the first fluorophores. A radiative flux of the first spectral signal may preferably, but need not necessarily, be substantially unabated over the predetermined maximum range.

According to an aspect of one preferred embodiment of the invention, the predetermined maximum range may preferably, but need not necessarily, be dependent upon the first fluorophores. The predetermined maximum range may preferably, but need not necessarily, be less than about 10 micrometers (µm).

According to an aspect of one preferred embodiment of the invention, the predetermined maximum range may preferably, but need not necessarily, be in the order of about 300 nanometers (nm).

According to an aspect of one preferred embodiment of the invention, the method and/or system may preferably, but need not necessarily, be for detection of infectious diseases.

According to an aspect of one preferred embodiment of the invention, the method and/or system may preferably, but need not necessarily, be for detection of cancer.

According to an aspect of one preferred embodiment of the invention, the method and/or system may preferably, but need not necessarily, be for detection of cystic fibrosis.

According to an aspect of one preferred embodiment of the invention, the method and/or system may preferably, but need not necessarily, be for use in a biomolecular assay.

According to an aspect of one preferred embodiment of the invention, the method and/or system may preferably, but need not necessarily, be for use in a sandwich assay as the biomolecular assay.

According to an aspect of one preferred embodiment of the invention, the second fluorophores also may preferably, but need not necessarily, be operatively adapted for absorption of the EMF radiation, and/or for emission of the second fluorescent signal following absorption of the EMF radiation.

According to an aspect of one preferred embodiment of the invention, the microbeads may preferably, but need not necessarily, be operatively combined with the BRMs, the test sample, and/or the second fluorophores.

According to an aspect of one preferred embodiment of the invention, the first fluorophores may preferably, but need not necessarily, be operatively combined with the test sample, the marker molecules, and/or the second fluorophores.

According to an aspect of one preferred embodiment of the invention, the second fluorophores also may preferably, but need not necessarily, be operatively adapted for absorption of the EMF radiation, and/or for emission of the second fluorescent signal following absorption of the EMF radiation. The first fluorophores and/or the second fluorophores may preferably, but need not necessarily, be operatively irradiated with the EMF radiation, preferably via the irradiating device.

According to the invention, there is additionally disclosed a fluorophore, quantum dot and/or fluorescent dye for use as one of the first or second fluorophores in the method and/or system described above.

According to the invention, there are additionally disclosed microbeads, biorecognition molecules, and/or marker molecules for use in the method and/or system described above.

Other advantages, features and/or characteristics of the present invention, as well as methods of operation and/or functions of the related elements of the method and system, and/or the combination of steps, parts and/or economies of manufacture, will become more apparent upon consideration of the following detailed description and the appended claims with reference to the accompanying drawings, the latter of which are briefly described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features which are believed to be characteristic of the system and method according to the present invention, as to their structure, organization, use, and/or method of operation, together with further objectives and/or advantages thereof, may be better understood from the following drawings in which presently preferred embodiments of the invention will now be illustrated by way of example. It is expressly understood, however, that the drawings are for the purpose of illustration and description only, and are not intended as a definition of the limits of the invention. In the accompanying drawings:

<figref idref="f0001"><b>Figure 1</b></figref> is a graph of the absorption and emission profiles for a first fluorophore according to a preferred embodiment of the present invention;

<figref idref="f0001"><b>Figure 2</b></figref> is a graph of the emission profile for the first fluorophore represented in <figref idref="f0001">Figure 1</figref>, and the absorption profile for a second fluorophore according to the preferred embodiment of the present invention;

<figref idref="f0002"><b>Figure 3</b></figref> is a graph of the absorption and emission profiles for the second fluorophore represented in <figref idref="f0001">Figure 2</figref>;

<figref idref="f0002"><b>Figure 4</b></figref> is a graph of the emission profiles for the first and second fluorophores represented in <figref idref="f0001">Figures 1 and 2</figref>, respectively;

<figref idref="f0003"><b>Figure 5</b></figref> is an illustrative representation of a system including the first and second fluorophores, shown in conjunction with target molecules, according to the preferred embodiment of the present invention;

<figref idref="f0004"><b>Figure 6</b></figref> is a graph of various first fluorophore doping percentages in microbeads against the first fluorescent signal intensity according to the preferred embodiment of the present invention;

<figref idref="f0005"><b>Figure 7A</b></figref> is an illustrative representation of the system of <figref idref="f0003">Figure 5</figref>, shown without the target molecules, marker molecules and second fluorophores;

<figref idref="f0005"><b>Figure 7B</b></figref> is an illustrative representation of the system of <figref idref="f0005">Figure 7A</figref> shown in conjunction with the target molecules;

<figref idref="f0005"><b>Figure 7C</b></figref> is an illustrative representation of the system of <figref idref="f0005">Figure 7B</figref>, shown in conjunction with the marker molecules and the second fluorophores;

<figref idref="f0006"><b>Figure 8</b></figref> is a graph of various first fluorescent signal intensities against the median second fluorescent signal intensity according to the preferred embodiment of the present invention, and showing a median fluorescent emission signal for a molecular FAM dye for comparison purposes;

<figref idref="f0007"><b>Figure 9</b></figref> is a graph of various median first fluorescent signal intensities against the enhancement factor for the second fluorescent signal according to the preferred embodiment of the present invention; and

<figref idref="f0008"><b>Figure 10</b></figref> is an illustrative representation, similar to <figref idref="f0003">Figure 5</figref>, of an alternate system including the first and second fluorophores, shown in conjunction with target molecules, according to an alternate preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008">Figures 1-10</figref> of the drawings, there are represented methods and systems for fluorescent detection of target molecules 60 according to the present invention. The methods and systems according to the present invention are adapted to test for the presence of the target molecules 60 in a test sample (not shown).

Generally, and as best seen in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7C</figref> and <figref idref="f0008">10</figref>, the system includes a microbead 20 and biorecognition molecules (BRMs) 50. Each microbead 20 contains first fluorophores 26. The BRMs 50 bind the target molecules 60 (if present in the test sample), which in turn are bound to marker molecules 70 bearing second fluorophores 76.

Use of the present invention in biomolecular assays may advantageously provide for an internal volume of the microbead 20 to be used as a localized compartment to hold numerous ones of the first fluorophores 26. Since, as may be described in considerably greater detail elsewhere herein, the first fluorophores 26 are preferably highly customizable quantum dots (QDs), each microbead 20 may contain thousands, or even millions, of the first fluorophores 26. Additionally, and as may also be described in considerably greater detail elsewhere herein, because the QDs may be tailored and/or customized to have various predetermined and/or selected emission energies, the first fluorophores 26 may be chosen and embedded within the microbead 20, such that the fluorescence emission properties of the first fluorophores 26 will preferably overlap only with another specific fluorophore.

As best seen in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7A</figref> and <figref idref="f0008">10</figref>, the BRMs 50 are bound to a surface 22 of the microbead 20. More specifically, and as best seen in <figref idref="f0008">Figure 10</figref>, proximal end portions 52 of the BRMs 50 (being those portions most closely situated towards the microbead 20) are preferably bound to functional groups 24 provided on the surface 22 of the microbead 20.

In one preferred embodiment according to the present invention, and as best seen in <figref idref="f0003">Figures 5</figref> and <figref idref="f0005">7A-7C,</figref> the BRMs 50 may be provided as one or more single-stranded biorecognition DNA (BRM-ssDNA) molecules. When the BRMs 50 are operatively bound to the microbead 20, they together form a microbead/BRM-ssDNA substrate (as best seen in <figref idref="f0005">Figure 7A</figref>).

The microbead/BRM-ssDNA substrate may then preferably be added to a solution (e.g., a plasma/PCR product). Preferably, the microbead/BRM-ssDNA substrate will then diffuse through the solution, while searching for and/or scavenging, via hybridization, the target molecules 60.

In one preferred embodiment according to the present invention, and as best seen in <figref idref="f0005">Figure 7B</figref>, the target molecules 60 may be one or more target strands of a nucleic acid sequence complementary to at least one of the BRM-ssDNA molecules. The target molecules 60 operatively bind with the BRMs 50 as shown in <figref idref="f0005">Figure 7B</figref>, and have unbound distal end portions 62 - preferably at least one each. The distal end portions 62 are those portions of the target molecules 60 which, in an operatively bound configuration (as shown in <figref idref="f0005">Figure 7B</figref>), are furthest removed from the surface 22 of the microbead 20. When the target molecules 60 are operatively bound to the microbead/BRM-ssDNA substrate, they together form a microbead/BRM-ssDNA/target substrate (as best seen in <figref idref="f0005">Figure 7B</figref>).

Subsequently, the marker molecules 70 are preferably added to the microbead/BRM/target substrate shown in <figref idref="f0005">Figure 7B</figref>. A second hybridization reaction will preferably take place to form the test positive end product shown in <figref idref="f0005">Figure 7C</figref>. The second fluorophores 76 are preferably operatively bound to distal end portions 72 of the marker molecules 70 (as best seen in <figref idref="f0005">Figure 7C</figref>). The distal end portions 72 are those portions of the marker molecules 70 which, in an operatively bound configuration (as shown in <figref idref="f0005">Figure 7C</figref>), are furthest removed from the surface 22 of the microbead 20. Preferably, the marker molecules 70 operatively bind to the distal end portions 62 of the target molecules 60 (as best seen in <figref idref="f0005">Figure 7C</figref>).

In an alternate preferred embodiment, and as shown in <figref idref="f0008">Figure 10</figref>, the BRMs 50 may be provided as one or more BRM antibody molecules, the target molecules 60 may be provided as one or more target antigen molecules, and the marker molecules 70 may be provided as one or more marker antibody molecules. The BRM antibody molecules and the marker antibody molecules are operatively bound to the target antigen molecules. The second fluorophores 76 are preferably operatively bound to distal end portions 72 of the marker antibodies.

Preferably, and as best seen in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7C</figref> and <figref idref="f0008">10</figref>, when the target molecules 60 are present in the test sample (not shown), they operatively secure the first fluorophores 26 relative to the second fluorophores 76.

With further reference to <figref idref="f0003">Figure 5</figref>, the first fluorophores 26 will be seen to operatively emit a first fluorescent signal 34 after absorption of electromagnetic frequency (EMF) radiation 40. The first fluorescent signal 34 preferably radiates outward from the surface 22 of the microbead 20.

As best seen in <figref idref="f0003">Figure 5</figref>, a first incident portion 34A of the first fluorescent signal 34 is preferably incident upon one or more of the second fluorophores 76, and a second detectable portion 34B of the first fluorescent signal 34 radiates further outward from the microbead 20.

The second fluorophores 76 are adapted for operative absorption of the first incident portion 34A of the first fluorescent signal 34. After absorption of the first incident portion 34A, the second fluorophores 76 operatively emit a second fluorescent signal 84 (as shown in <figref idref="f0003">Figure 5</figref>). As may be best appreciated from <figref idref="f0002">Figure 4</figref>, and as may be described in considerably greater detail elsewhere herein, the second fluorescent signal 84 is preferably readily distinguishable from the first florescent signal 34.

As shown in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7C</figref> and <figref idref="f0008">10</figref>, the target molecules 60 secure the first fluorophores 26 relative to the second fluorophores 76. As such, the first incident portion 34A of the first fluorescent signal 34 selectively excites the second fluorophore 76, and enhances emission of the second fluorescent signal 84, preferably only if the target molecules 60 are present in the test sample (not shown). Without intending to be bound by theory, the aforementioned effect is believed to occur only when the target molecules 60 are present in the test sample, since the target molecules 60 operatively secure the first fluorophores 26 and the second fluorophores 76 relative to each other. In this manner, the target molecules 60 enable greater absorption of the first fluorescent signal 34 by the second fluorophores 76. This selective excitation of the second fluorophores 76 by the first fluorophores 26 when the target molecules 60 are present in the test sample (not shown) is believed - again, without intending to be bound by theory - to impart sensitivity, and selectivity, to the assay because unbound second fluorophores 76 (or molecular dyes of other energies) may show little or no enhancement of their respective emission spectral signals.

More particularly, and as best seen in <figref idref="f0003">Figure 5</figref>, the first fluorophores 26 will preferably emit photons (in the form of the first fluorescent signal 34) in all directions from the surface 22 of the microbead 20. In this manner, enhancement of the second fluorescent signal 84 is dependent upon the second fluorophores 76 being located within a predetermined maximum range (as indicated generally by dimension "D" in <figref idref="f0003">Figure 5</figref>) from the first fluorophores 26. Where, as here, the first fluorophores 26 may be bound substantially at the surface 22 of the microbead 20, it may be possible to measure the predetermined maximum range "D" from the surface 22 of the microbead 20. The predetermined maximum range "D" defines a region 36 of substantially unabated radiative flux (or high photon flux) for the first fluorescent signal 34. In this region 36, similar photon densities (e.g., within 10%) may be observed at the surface 22 of the microbead 20 and at the predetermined maximum range "D" from the surface 22. Without intending to be bound by theory, it is believed that the efficiency of the assay is negligibly diminished when the second fluorophores 76 are bound within the predetermined maximum range "D" from the surface 22 of the microbead 20. Although not essential to the working of the present invention, it may be generally believed that, according to one preferred embodiment and by way of non-limiting example only, when the microbead 20 is provided with a diameter of about five micrometers (5 µm), the predetermined maximum range "D" may be in the approximate order of about 300 nanometers (nm).

In one preferred embodiment, and as best seen in <figref idref="f0003">Figures 5</figref> and <figref idref="f0005">7A-7C</figref>, the first fluorophores 26 embedded within the microbead 20 may be provided in the form of QDs adapted to emit photons centered at about 580 nanometers (nm) - i.e., generally in the yellow range of the visible light spectrum. These QDs may serve as a source of excitation energy for the second fluorophores 76, which preferably may be provided in the form of a Cyanine-5 (Cy5) molecular dye - more preferably, a Cyanine-5.5 (Cy5.5) molecular dye - that absorbs yellow light strongly and emits photons having a wavelength generally situated towards the red end of the visible light spectrum.

As may be appreciated from a consideration of <figref idref="f0002">Figure 3</figref>, when the second fluorophores 76 are provided in the form of the Cy5 molecular dye, they may be excited, <i>inter alia,</i> by incident radiation 90 (e.g., coherent light from a laser) having a wavelength of about 635 nanometers (nm) - i.e., provided that the incident coherent radiation 90 lies within a second fluorophore absorption profile 78 (as best seen in <figref idref="f0002">Figure 3</figref>) characteristic of the Cy5 molecular dye. Thereafter, the CY5 molecular dye is adapted to operatively emit the second fluorescent signal 84. The second fluorescent signal 84 corresponds to a second fluorophore emission profile 80 (best seen in <figref idref="f0002">Figure 3</figref>) characteristic of the Cy5 molecular dye. Although not essential to the working of the present invention, the intensity of the second fluorescent signal 84 emitted by the Cy5 molecular dye may depend generally upon the amount of the incident radiation 90 absorbed thereby.

Although not necessary to the operation of the invention, in one preferred embodiment, the region 36 of substantially unabated radiative flux (best seen in <figref idref="f0003">Figure 5</figref>) may be dependent upon the concentration and/or quantum yield of the QDs bound within the microbead 20. By way of a non-limiting example only, when microbeads 20 are doped (i) with an arbitrary 100% QD concentration, and (ii) with a relative 10% QD concentration (i.e., one tenth of the QD concentration), the predetermined maximum range "D" for the 100% QD-doped microbead may be in the approximate order of between about three and about five (∼3 to ∼5) times higher than that for the 10% QD-doped microbead. In addition, and still by way of example, if the 10% QD-doped microbead provides for a predetermined maximum range "D" of about 300 nanometers (nm), then the 100% QD-doped microbead might provide for a predetermined maximum range "D" of about one micrometer (∼1 µm) or more. The predetermined maximum range "D" for any particular microbead 20 may be dependent upon the volume of photon flux within the region 36, and the QD-doping concentration in the microbead 20.

Reference will now be made, briefly, to the method of enhancing fluorescent detection of the target molecules 60 in the test sample (not shown) according to one or more preferred embodiments of the present invention. The method is for use with an irradiating device (not shown) and is, preferably, for use with the system shown in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7A-7C</figref> and <figref idref="f0008">10. </figref>It should, of course, be appreciated that, according to the present invention, the methods may be employed independent of the system described elsewhere herein.

Now, according to the present invention, the method may preferably include steps (a), (b), (c), (d), (e), (f) and/or (g).

In step (a), one or more of the first fluorophores 26 (as shown in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7A-7C </figref>and <figref idref="f0008">10</figref>) are provided. The first fluorophores 26 are adapted for absorption of the EMF radiation 40. The first fluorophores 26 are additionally adapted for emission of the first fluorescent signal 34 following absorption of the EMF radiation 40. As shown in <figref idref="f0001">Figure 1</figref>, the first fluorophores 26 are characterized by a first fluorophore absorption profile 28 (substantially encompassing the wavelength(s) of the EMF radiation 40), and by a first fluorophore emission profile 30 (substantially corresponding to the first fluorescent signal 34). The first fluorophore emission profile 30 is itself preferably characterized by a peak intensity 32 at a wavelength of about 580 nanometers (nm).

In step (a), and as best seen in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7A</figref> and <figref idref="f0008">10</figref>, the first fluorophores 26 are bound by microbead 20. In a preferred embodiment, the first fluorophores 26 are provided in the form of the QDs of one or more QD types. For example, in <figref idref="f0008">Figure 10</figref>, the QDs are of two different QD types, 26A and 26B. The intensity of the first spectral signal 34 is preferably dependent on the number of QDs bound by the microbead 20. The color of the first spectral signal 34 is preferably dependent upon the size of the QD types, 26A and 26B, bound by the microbead 20.

As may be appreciated from a consideration of <figref idref="f0001">Figure 1</figref>, when the first fluorophores 76 are provided in the form of the QDs having their peak intensity 32 at about 580 nanometers (nm), they may be excited, <i>inter alia,</i> by the EMF radiation 40 at a wavelength of about 488 nanometers (nm) - i.e., provided that 488 nm lies, as it preferably does, within the first fluorophore absorption profile 28 characteristic of the first fluorophores 76 (as best seen in <figref idref="f0001">Figure 1</figref>).

In step (b), one or more of the second fluorophores 76 (best seen in <figref idref="f0003">Figures 5</figref>, <figref idref="f0005">7C</figref> and <figref idref="f0008">10</figref>) are provided. The second fluorophores 76 are adapted for absorption of the first incident portion 34A of the first fluorescent signal 34. The second fluorophores 76 are additionally adapted for emission of the second fluorescent signal 84 after absorption of the first fluorescent signal 34 (as may be best appreciated from a consideration of <figref idref="f0001">Figures 2</figref> and <figref idref="f0002">3</figref>).

As best seen in <figref idref="f0002">Figure 3</figref>, the second fluorophores 76 are characterized by a second fluorophore absorption profile 78, and by a second fluorophore emission profile 80 (corresponding to the second fluorescent signal 84). As shown in <figref idref="f0001">Figure 2</figref>, the second fluorophore absorption profile 78 substantially overlaps with the first fluorophore emission profile 30, to define an overlap region 100. In this context, and for the purposes of this application, "substantially overlaps" means to a degree sufficient for excitation of the affected fluorophores. That is, the first fluorophore emission profile 30 is operative, in its overlap region 100 (with the second fluorophore absorption profile 78), to excite the second fluorophores 76.

As shown in <figref idref="f0002">Figure 4</figref>, the second fluorophore emission profile 80 (and the second fluorescent signal 84) is distinguishable from the first fluorophore emission profile 30 (and the first fluorescent signal 34). Preferably, and as may be appreciated from a consideration of <figref idref="f0001">Figures 1</figref> and <figref idref="f0002">4</figref>, the second fluorophore emission profile 80 (best seen in <figref idref="f0002">Figure 4</figref>) is substantially removed from - i.e., it does not substantially overlap with - the first fluorophore absorption profile 28 (best seen in <figref idref="f0001">Figure 1</figref>). As may be described in considerably greater detail elsewhere herein, the first fluorescent signal 34 and the second fluorescent signal 84 are operatively detectable within the same visible light spectrum (i.e., if the target molecules 60 are present in the test sample).

Step (c) is preferably performed after step (a). In step (c), the BRMs 50 are provided. Preferably, and as best seen in <figref idref="f0008">Figure 10</figref>, the BRMs 50 are adapted to operatively bind with the microbeads 20 and the target molecules 60 (if present in the test sample), so as to secure the first fluorophores 26 relative to the target molecules 60.

Preferably, step (d) is performed after step (b). In step (d), the marker molecules 70 are provided. As best seen in <figref idref="f0008">Figure 10</figref>, the marker molecules 70 are adapted to operatively bind with the second fluorophores 76 and the target molecules 60 (if present in the test sample). In this manner, the marker molecules 70 secure the second fluorophores 76 relative to the target molecules 60 (if present in the test sample).

Step (e) is preferably performed after at least one, and preferably all, of steps (b) through (d). As may be best appreciated from a consideration of <figref idref="f0008">Figure 10</figref>, in step (e), the microbeads 20 containing the first fluorophores 26 are operatively combined with the BRMs 50, the test sample (not shown) potentially containing the target molecules 60, the marker molecules 70, and/or the second fluorophores 76.

Preferably, step (f) is performed after step (e). In step (f), and as shown in <figref idref="f0003">Figure 5</figref>, at least the first fluorophores 26 are operatively irradiated with the EMF radiation 40 via the irradiating device (not shown). Preferably, the second fluorophores 76 may also be operatively irradiated with the EMF radiation 40.

Step (g) is preferably performed after step (f). In step (g), and as may be best appreciated from a consideration of <figref idref="f0002">Figures 4</figref> and <figref idref="f0003">5</figref>, the first spectral signal 34 is operatively detected, together with the second spectral signal 84 (if the target molecules 60 are present in the sample).

In one preferred embodiment, and with further reference to <figref idref="f0008">Figure 10</figref>, the microbeads 20 may be doped with the first fluorophores 26 in the form of two different QD types, 26A and 26B, to create a specific emission spectrum ("barcode") uniquely identifying a particular one of the microbeads 20 with a specific set of the BRMs 50 bound thereto. The overall intensity and color of the microbead 20 is preferably determined by the amounts, sizes and/or ratios of the different QD types, 26A and 26B, used in the doping process.

<figref idref="f0004">Figure 6</figref> shows the median intensity of emitted wavelengths produced from a series of synthetic microbeads 20 in which the percentage doping with the QDs (i.e., the first fluorophores 26) was varied between about 10% and about 100% of a stock concentrated QD solution. In <figref idref="f0004">Figure 6</figref>, the average emission intensity for the series of microbead 20 samples is displayed as measured on a FACSCalibur flow cytometer.

In one preferred embodiment according to the present invention, the microbeads 20 are doped with the QDs (i.e., the first fluorophores 26) which emit the first fluorescent signal 34 with a wavelength centered roughly about 580 nanometers (nm) - such that these microbeads may alternately herein be referred to as QD580 doped microbeads 20. The QD580 doped microbeads 20 may be used, for example, as a substrate in a sandwich nucleic acid or genomic assay (as shown in <figref idref="f0003">Figures 5</figref> and <figref idref="f0005">7A-7C</figref>) or in a sandwich immunoassay according to one or more preferred methods of the present invention. Preferably, the QDs (i.e., the first fluorophores 26) are thus operative to sensitize and/or enhance the emission intensity for the second fluorophores 76 (e.g., Cy5 molecular dyes).

Preferably, and as may be best appreciated from a consideration of <figref idref="f0001">Figure 1</figref>, a 488 nm laser (not shown) may be used to excite the QD580 doped microbeads 20. As shown in <figref idref="f0003">Figure 5</figref>, the QD580 doped microbeads 20 may be bound to the target molecules 60, which are in turn bound to the marker DNA molecules (i.e., the marker molecules 70). Each of the marker DNA molecules may preferably bear one or more Cy5.5 molecular dyes (DNA-Cy5.5) which provide for an emission towards the red end of the visible light spectrum. <figref idref="f0006">Figure 8</figref> graphs the median dye intensity for the Cy5.5 molecular dyes in conjunction with the median QD intensity of the QD580 doped microbeads.

On excitation with the 488 nm laser, the QDs are selectively excited, and the DNA-Cy5.5 emission is enhanced (with a concomitant increase in its median QD intensity), as may be appreciated from a consideration of <figref idref="f0006">Figure 8</figref>.

Compared against this reference line, <figref idref="f0006">Figure 8</figref> also graphs the median dye intensity for FAM molecular dyes (DNA-FAM) bound in conjunction with the marker DNA molecules, the target molecules 60, and the QD580 doped microbeads. The FAM molecular dyes provide for an emission substantially within the green range of the visible light spectrum. Perhaps notably, the FAM molecular dyes are situated generally in the blue (higher energy) direction from the generally yellow-emitting QD580 doped microbeads.

In <figref idref="f0006">Figure 8</figref>, the intensity of the DNA-Cy5.5 emission is compared to the intensity of the DNA-FAM emission over a range of median QD intensities. As may be appreciated from a consideration of <figref idref="f0006">Figure 8</figref>, the represented data fails to demonstrate a corresponding enhancement and excitation of surface-bound DNA-FAM by QD580-doped microbeads.

The prior art may heretofore have been largely based on the use of second fluorophores 76 situated generally towards the "blue" end of the spectrum relative to the QDs (i.e., the first fluorophores 26). As such, in the prior art, the second fluorophores 76 may have been effectively quenched, with the second fluorescent signal 84 being diminished by the first fluorophore absorption profile 28 and/or the first fluorophore emission profile 30 (shown in <figref idref="f0001">Figure 1</figref>) of the QD-doped microbead 20.

In order to provide for enhancement of the second fluorescence signal 84 (and not the previously known opposite quenching effect), it may be generally thought preferable - though perhaps not essential to the working of the present invention - for the second fluorophore emission profile 80 (and thus the second fluorescent signal 84 emitted by the second fluorophores 76) to be located towards the "red" end of the visible light spectrum - i.e., relative to the first fluorescent signal 34 emitted by the first fluorophores 26. It may also be preferable for the first fluorophore emission profile 30 (and thus the first fluorescent signal 34 of the first fluorophores 26) to be located in the yellow range of the visible light spectrum.

It may be appreciated that the graph shown in <figref idref="f0007">Figure 9</figref> illustrates the second fluorophores 76 (preferably, the Cy5 molecular dyes) as being adapted to emit the enhanced second fluorescent signal 84 as a function of QD-doping within the microbeads 20. Preferably, the Cy5 emission intensity may increase to become in the approximate order of over about 200 times brighter when compared to a blank (non-doped) microbead 20 sample. (A lack of controls - e.g., blank microbeads - in prior experiments may have made their results and/or procedures substantially unsuitable for any testing or exploitation of the enhancement effect described herein.) Although not essential to the working of the present invention, it may be believed that the intensity generated by use of the microbead 20 emission, alone, may be about as great as (or greater than) that generated by use of the laser alone.

It is believed that overall fluorescent detection sensitivity may be substantially increased by enhancement of the second fluorophores 76, thus enabling the second fluorophores 76 (whether they be dye molecules or QDs) to be used in conjunction with larger and more intense emission molecules, such as the microbeads 20 referred to herein.

Other modifications and alterations may be used in the design and manufacture of other embodiments according to the present invention without departing from the spirit and scope of the invention, which, is limited only by the accompanying claims of this application. For example, while the above method and system have, in one preferred embodiment, been presented in the context of an immunoassay and a genomic assay, the method and system may be equally applicable to other types of assays (and/or for the detection of other types of target molecules, possibly in other types of test samples).

Additionally, the method and system according to the present invention may preferably be used for a variety of <i>in vitro</i> biomolecular assays including genomic and/or proteomic identification of markers for infectious diseases, cancer, cystic fibrosis and other human veterinary or environmental aliments. Similarly, the method and system according to the present invention may preferably be used for detection of cardiac symptoms and/or detection of biomarkers for cardiac conditions and/or predispositions. The method and system according to the present invention are also preferably adapted for use in medical imaging and other <i>in vivo</i> applications.

In view of all of the foregoing, it is perhaps worthwhile to once again note that the foregoing description has been presented for the purpose of illustration and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many further modifications and/or variations are possible in light of the teachings herein, as may be apparent to those skilled in the art. It is intended that the scope of the present invention be limited not by this description but only by the accompanying claims.