Rapid Detection of Escherichia coli by Using Antibody-Conjugated Silver Nanoshells

Silver shells of 20 nm thickness have been deposited on silica particles of 200 nm diameter with narrow size distribution. Silver nanoshells dispersed in water exhibit a strong surface plasmon resonance band at 443 nm. This band was found to be very sensitive to rabbit immunoglobulin G antibodies, which were anchored on the nanoshells. These in turn could be utilized to detect the presence of small (≈5) to large numbers (≈109) of Escherichia coli in water. The protocol presented here proves to be a specific, rapid, reliable, and inexpensive method to detect E. coli. Drinking water test: Escherichia coli, which is a normal inhabitant of the intestine, has been accepted as an indicator organism for the detection of the potability of water (see SEM image). A very sensitive technique has been developed by using silver nanoshells for the rapid detection of E. coli. The technique makes use of changes in the surface plasmon resonance in the presence of an analyte associated with silver nanoshells.