Aerogels as biosensors: viral particle detection by bacteria immobilized on large pore aerogel

A proof-of-principle study is reported in which bacteria were immobilized w ithin macroporous, supercritically dried silica sol-gel discs and signal in duction was demonstrated by aerosolized virus particles. Escherischia coli (pET-gfp) bacteria-doped gels were used as an aerosol collector to detect b acteriophage. The bacteriophage (10(5) and 10(8) plaque forming units/ml) ( pfu/ml) were aerosolized through the discs for 10 min, at a flow rate of 1. 75 l/min and aerosol humidity of 70%. The discs were then incubated in bact erial growth media for 4 h and green fluorescent protein (GFP) expression m onitored. The induction of GFP indicated that both bacteriophage and bacter ia survived the stressful desiccating conditions of the aerosol challenge. Scanning confocal laser microscopic (SCLM) analysis demonstrated that the b acteriophage contacted viable bacteria and induced expression of the GFP in 35-95% of the bacterial cells. These findings indicate that virus particle s can penetrate the structure of macroporous silica gels and trigger a dete ctable response in immobilized bacteria. The goal is to use microorganisms immobilized within these materials to facilitate the detection of chemicals and organisms within the environment. (C) 2001 Elsevier Science B.V. All r ights reserved.