Gold-coated polycarbonate membrane filter for pathogen concentration and SERS-based detection.

A SERS-based method for the concentration and detection of Giardia lamblia cysts in finished drinking water is reported. In this method, samples are concentrated with a membrane filter and then cysts captured on the filter surface are labeled with immunogold SERS labels and quantified via Raman spectroscopy. Anodisc((R)) membrane filters, silver membrane filters, and electroless gold-coated polycarbonate track etched (PCTE) membrane filters were investigated for their compatibility with the SERS based detection strategy. The largest pore size Anodisc((R)) membrane commercially available was too small for the proposed method because they led to physical retention of immunogold. When silver membrane filters were employed, cysts were difficult to distinguish from nonspecifically bound labels and cyst recovery from distilled water samples was only approximately 12.3%. With gold-coated PCTE membranes, however, cysts were readily detectable and cyst recovery was approximately 95%. This Raman based method simplifies Giardia detection and has potential to be extended to the simultaneous detection of numerous pathogenic organisms. To our knowledge, this is the first report coupling the use of membrane filters for the concentration and detection of organisms from water samples with a SERS based detection strategy.