ABSTRACT
The accurate quantification of proteins at low concentrations over a wide dynamic range is needed to identify biological toxins and biomarkers associated with diseases and proteins captured by high-throughput microarrays used in proteomics. In this chapter, we describe an ultrasensitive and quantitative generic assay format called liposome-polymerase chain reaction (LPCR). LPCR uses liposomes with ganglioside or antibody (Ab)-binding receptors on their outer surface that bind biological toxins and antigens (Ags), respectively. These liposomes encapsulate DNA templates to serve as analyte surrogates that can be quantified by real-time polymerase chain reaction (PCR). Ganglioside-based
LPCR (gLPCR) assays for cholera and botulinum toxins were several orders of magnitude more sensitive than current detection methods. Likewise, Ab-based LPCR (immunoliposome-PCR or ILPCR) detected carcinoembryonic antigen (CEA), HIV-1 p24 core protein, and plasminogen activator inhibitor type-1 (PAI-1) with greatly improved sensitivities and dynamic ranges compared to current assays for these analytes.
