Sol-gel encapsulated anti-trinitrotoluene antibodies in immunoassays for TNT

Antibodies to trinitrotoluene (TNT) were encapsulated in optically transpar ent sol-gel derived silica glasses and retained their ability to bind TNT. Both competitive and displacement immunoassays were successfully performed using sol-gel immobilized antibodies. TNT concentrations on the order of pp m were detected. In competitive immunoassays using the sol-gel immobilized antibodies, a logarithmic decrease in fluorescence signal as a function of TNT concentration was observed, similar to competitive immunoassays perform ed in solution. When encapsulated in the sol-gel. silica matrix, the antibo dies retained their ability to differentiate between TNT and trinitrobenzen e (TNB), an analogue. In displacement immunoassays, the rate of displacemen t was dependent upon pore morphology, with aged gels exhibiting faster rate s than that of xerogels. The relative stability of antibodies was better fo r sol-gel encapsulated antibodies than for antibodies immobilized using sur face attachment. After exposure to HCl, methanol, or 60 degrees C, the sol- gel immobilized antibodies experienced essentially no loss in ability to bi nd TNT whereas the surface immobilized antibodies showed as much as 30% los s in ability to bind TNT.