Viswanadham Garimella

Universal Biotin-PEG-Linked Gold Nanoparticle Probes for the Simultaneous Detection of Nucleic Acids and Proteins.

Novel biotin-polyethylene glycol (biotin-PEG) gold nanoparticle probes have been synthesized and used as universal constructs for the detection of protein (prostate-specific antigen, PSA) and nucleic acid targets (microRNAs) from a single sample. Microarray assays based upon these probes enabled sensitive detection of biomarker targets (50 fM for nucleic acid targets and 1 pg/μL for the PSA target). Ways of detecting biomarkers, including nucleic acids and proteins, are necessary for the clinical diagnosis of many diseases, but currently available diagnostic platforms rely primarily on the independent detection of proteins or nucleic acids. In addition to the economic benefits associated with the use of a single platform to detect both classes of analytes, studies have shown that the simultaneous identification of multiple classes of biomarkers in the same sample could be useful for the detection and management of early stage diseases, especially when sample amounts are limited. Therefore, these new probes and the assays based upon them open the door for high-sensitivity combination-target assays for studying and tracking biological pathways and diseases.

Diagnostic Detection Systems Based on Gold Nanoparticle Probes

The development of a nanoparticle based detection methodology for DNA microarray applications is described. Originally reported by Mirkin and co-workers, the technology utilizes gold nanoparticles derivatized with thiol-modified oligonucleotides that are designed to bind complementary DNA targets. A glass surface with arrays of immobilized DNA capture sequences is used to capture DNA targets, which are then detected via hybridization to the gold nanoparticle probes. For maximum signal strength a layer of silver is deposited onto the gold nanoparticles, providing for highly sensitive and specific detection of target sequences using low cost optical detection systems. The relative optical detection limits for silver amplified gold nanoparticle probes and Cy3 based fluorescence have been tested. Furthermore, we report progress towards the direct detection of non-amplified genomic DNA from infectious agents and single nucleotide polymorphisms (SNP) in human genomic DNA based on nanoparticle technology.