Rapid point-of-care detection of Trichomonas Vaginalis - Project Summary
The goal of this project is to demonstrate feasibility of a system for the point-of-care (POC) detection of
Trichomonas vaginalis (TV) in human vaginal swab samples that integrates our patented detector of pathogens
based on identification of species-specific, nucleic acid (NA) sequences. The detector relies on a novel
electromechanical signal transduction mechanism that enables the low-cost, optics-free and amplification-free
(e.g., no PCR) detection of DNA/RNA at ultralow concentration (~10-19 M). A compelling need persists for rapid
(minutes), cost effective, POC NA detection devices for infectious disease diagnostics so as to facilitate prompt,
well-informed therapies and counseling and to avoid potentially harmful actions including the inappropriate
prescription of antibiotics. In earlier work, we demonstrated the detection of Neisseria gonorrhoeae (NG) with
sensitivity of ~98% and specificity of ~100%. Trichomoniasis, the most common curable, sexually transmitted
disease in the US, is often tested for in parallel with NG and Chlamydia trachomatis (CT) infections and is
therefore a logical target for us to address. A key feature of the patented detector is the use of peptide nucleic
acid (PNA) capture probes, which are uncharged polyamide analogs to NAs that share the same base chemistry.
Since bead-PNA conjugates are designed to be charge neutral, they do not exhibit electrophoretic movement in
the presence of a DC electric field. However, the substantial negative charge acquired upon capture of a target
NA sequence makes the hybridized conjugate mobile. Electrophoresis of the bead-PNA conjugate with
hybridized target NA to the mouth of a smaller diameter glass pore causes a significant increase in pore
resistance, thereby resulting in a strong, sustained drop in measured ionic current. Nonspecifically bound NA is
removed from the bead conjugate in the strong electric field at the pore mouth resulting in no sustained signal.
Further, the opposing electroosmotic flow through the glass pore sweeps PNA-bead conjugates without
hybridized target away from the pore mouth. In such a way, this simple conductometric device gives a highly
selective (no observed false positives), binary response signaling the presence or absence of the target NA (and
associated pathogen). This project focuses on two Aims: 1) Demonstration of the detection of TV in remnant
vaginal swab samples from the UCLA Clinical Microbiology Laboratory with competitively high sensitivity (≥95%)
and specificity (≥95%) and 2) Development and feasibility testing of key steps in an integrated and robust
laboratory prototype device for rapid (<5 mins) pathogen detection based on the relatively inexpensive lateral
flow assay (LFA) format. Successful achievement of these Aims will result in a device concept ready for
manufacturable prototype development that is capable of NG and TV testing with competitive accuracy and likely
with significant advantages of cost, rapidity, power and robustness. Further research and development work is
envisioned to expand sampling capabilities to other pathogens, including CT, and to other complex sample media
including blood and sputum.
