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 within macroporous, supercritically dried silica sol–gel discs and signal induction was demonstrated by aerosolized virus particles. Escherischia coli (pET-gfp) bacteria-doped gels were used as an aerosol collector to detect bacteriophage. The bacteriophage (105 and 108 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 bacterial growth media for 4 h and green fluorescent protein (GFP) expression monitored. The induction of GFP indicated that both bacteriophage and bacteria survived the stressful desiccating conditions of the aerosol challenge. Scanning confocal laser microscopic (SCLM) analysis demonstrated that the bacteriophage contacted viable bacteria and induced expression of the GFP in 35–95% of the bacterial cells. These findings indicate that virus particles can penetrate the structure of macroporous silica gels and trigger a detectable 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.