One of the major current scientific challenges is to identify the function and expression of human genes. A better appreciation of such function and expression contributes to an enhanced understanding of human health, provides for a more accurate diagnosis of human diseases as well as providing for a more targeted design of medical therapies. Accordingly, the area of gene detection has witnessed a tremendous amount of research activity in recent years.
DNA and RNA samples are usually isolated from cellular material in very small quantities, calling upon techniques for signal enhancement. However, while many DNA detection methods have been designed, the various difficulties associated with signal enhancement remain unresolved.
To date, techniques for signal enhancement of gene detection have typically relied upon the enzymatic amplification of the analyte. The polymerase chain reaction (PCR) has become a standard technique in almost every molecular biology laboratory for the amplification of targeted DNA or RNA sequences. However, PCR techniques can be time consuming and may not preserve all the information contained within the DNA or RNA sequences to be analyzed.
Detecting minute concentrations of physiological or aberrant proteins is essential for correlation with pathologic state, diagnosing disease or monitoring disease progression. For proteins, however, in vitro methods allowing for signal amplification of the detection event are not readily available.
Organic chromophores, which are commonly used in biological assays, often undergo self-quenching, severely limiting their use as signal amplification systems. Ruthenium tris-bipyridine, a luminescent and redox active transition metal complex, does not exhibit significant self-quenching because of its large Stokes shift (i.e., its absorption and emission spectra do not overlap).
Several systems have been reported to affect signal amplification of biomolecules. In one method, dendrimers containing as many as eight ruthenium centers have been described, and in two systems, the dendrimers have been covalently attached to a protein, or to progesterone.1 Amplification in both the luminescence and the electrochemiluminescence signals was detected.
Another system reported by Bard et al. describes the encapsulation of free ruthenium tris-bipyridine complexes in polystyrene microspheres. The microspheres are labeled with single stranded DNA (analyte). These microspheres were then used to capture magnetic particles labeled with probe complementary DNA. Redissolution of these microspheres liberated the ruthenium centers, which were detected with electrochemiluminescence.2 However, physically entrapping the ruthenium centers within the reported microspheres raises the possibility of premature leaking, which in turn can interfere with the specificity of the biological recognition event.
In yet another method, polyacrylonitrile nanospheres were doped with ruthenium bipyridine units, and their luminescence studied. However, these doped nanospheres have not been used for biological assays.3 
Silica nanoparticles doped with ruthenium bipyridine units have been reported, and have been used for DNA and protein assays.4 However, such silica based nanoparticle systems have significant limitations. While a certain number of chromophores may be physically entrapped within the silica particles, there is little control over: (i) how many ruthenium centers may be encapsulated; (ii) the location of the ruthenium centers within the particle; and (iii) if more than one type of chromophore is used, there is limited control over the ratio. Moreover, the particles cannot be subsequently opened and the ruthenium bipyridine centers cannot be liberated for electrochemiluminescence, thus limiting signal amplification to mere luminescence.
An ultrasensitive assay, using both gold and magnetic particles labeled with DNA, as well as a multistep method involving silver enhancement has also been reported.5 
Ruthenium bipyridine-containing polymers have recently been the subject of increasing interest, due to their numerous potential applications (i.e. photoconductive materials, photocatalysts, solar energy conversion materials, sensors, and supramolecular building blocks). 6-14 Ruthenium bipyridine complexes present additional unique photophysical properties which distinguish them from their organic counterparts, including their long excited-state lifetimes, chemical inertness and photostability, tunability of their photophysical characteristics, large Stokes shifts and resistance to photobleaching.15-17 The incorporation of many of these chromophores into a polymeric backbone provides one way of amplifying a luminescence signal triggered by the recognition of a biological molecule.18 
To achieve an even greater degree of luminescence amplification, block copolymers comprising repeating ruthenium (II) bipyridine chromophore units have been constructed.19 Self-assembly of these copolymers yields luminescent nanoscale micellar aggregates, containing a large number of ruthenium (II) chromophores.
There thus remains a need for methods allowing for the rapid and highly sensitive detection of specific biomolecules in a sample through signal amplification. Moreover, there remains a need for compositions and articles of manufacture useful in such a method.
The present invention seeks to meet these needs and other needs.
The present description refers to a number of documents, the content of which is herein incorporated by reference in their entirety.