This dissertation focuses on the development of assays that could potentially be used in Point-Of-Care (POC) diagnostics.

The first chapter provides an overview of the stringent requirement of POC diagnostics and recent interesting developments in this field. The second chapter focuses on the development of assays to detect small molecule therapeutics, which can be a challenge unless one resorts to sophisticated instrumentation such as Mass spectroscopy and/or HPLC. In brief, an “add, mix, and measure” assay was developed to detect AZT within minutes. Three different probes designed to release fluorophores when samples containing AZT are added were synthesized and characterized. This simple and rapid point-of-care test could potentially be used by clinicians and health care workers to monitor the presence of AZT in low resource settings.

In the third chapter, the principle is based on the “cap and release” mechanism. Introduction of an analyte opens the “cap”, exposing the contents of the nanomaterial to the environment. Here, we designed a simple, inexpensive, and user-friendly platform that can be readily applied to detect HIV and other analytes. Highly stable and uniform palladium nanoparticles covered with mesoporous silica (Pd@mSiO₂) were generated and characterized extensively using physical methods. Next, Human Serum Albumin (HSA) protein or ssDNA specific to the HIV gag region was capped onto the Pd@mSiO₂ electrostatically. In the presence of target anti-HSA antibodies or complementary sequence (HIV gag), HSA protein or DNA “caps” dissociated from the surface of Pd@mSiO₂-NH₂ through the specific antigen-antibody reaction or hybridization, allowing the Pd to turn on the non-fluorescent probes.

In the fourth and final chapter, a universal amplification method was developed to lower the limits of detection for different analytes. This strategy was applied to HIV. Briefly, we describe an amplification technique based on fluorescent silica nanoparticles coupled with bioorthogonal chemistries for the femtomolar detection of HIV-1 p24 antigen and HIV gag. We developed a magnetic bead-based assay, wherein we used fluorescent dye-encapsulated silica nanoparticles as reporters.

The strengths, weaknesses and future directions of these assays are provided at the end of each chapter.