Abstract
Purpose: :
We previously reported the detection of bacterial antigen with immunoaffinity reactions using laser optoacoustic spectroscopy and antibody-coupled gold nanorods (Ab-NR) as a contrast agent specifically targeted to the antigen of interest. This method has been adapted to detect Herpes Simplex Virus 1 and 2 (HSV-1 and HSV-2) antigens in clinical samples.
Methods: :
A commercial monoclonal antibody, recognizing both HSV-1 and HSV-2, was conjugated to thiol-activated gold nanorods (NR) to produce a targeted contrast agent with a strong optoacoustic signal. Following a protocol approved by the UTHSCSA IRB, corneal swabs were obtained from University Eye Clinic patients with suspected herpetic keratitis, and eluates from these swabs were adsorbed in standard microtiter wells. Wells were probed with the Ab-NR detection reagent using a modified ELISA procedure. Optoacoustic responses (generated from the bound Ab-NR) were elicited from each well by a pulsed laser beam, and recorded optically and with a pressure transducer. Results of the assay were compared to the standard diagnostic technique employed at our hospital’s microbiology laboratory.
Results: :
A positive optoacoustic response was obtained from samples containing authentic HSV-1 and HSV-2. Only background optoacoustic signals were generated from micro-wells containing albumin or saline blanks. Preliminary results from four patient samples demonstrated agreement with the standard microbiological diagnosis. The optoacoustic response generated from the gold NR was a wideband signal, and was directly proportional to the concentration of viral protein.
Conclusions: :
These findings indicate that optoacoustic sensing of HSV-1 and HSV-2 with specific NR contrast enhancement can be useful for practical ophthalmic diagnosis. There is a very good signal to noise ratio in HSV-containing samples. The targeted contrast agents are specific, and, at least in the preliminary patient data set, the technique has been accurate. The proportionality of the optoacoustic signal with target antigen concentration reasonably indicates that the NR labeling technique may be useful in quantifying the number of infectious agents present.
Keywords: clinical laboratory testing • herpes simplex virus