Three approaches to detection of biological agents based on biological processes will be presented. The first example
demonstrates the use of dendrimers to deliver a membrane-impermeable fluorescent dye into live bacteria, similar to
viral infection and delivery of DNA/RNA into a bacterial cell. The second example mimics collection and capture of
airborne biological particles by the respiratory mucosa through the use of a hygroscopic sensing membrane. The third
example is based on the use of multiple fluorescent probes with diverse functionalities to detect airborne biological
agents in a manner similar to the olfactory receptors in the nasal tract.
A new approach is presented for real-time detection of bacterial aerosols using a sensing film configured on optical fibers. The sensing film contains nucleic acid-reactive fluorophores immobilized in hydrophilic polymers such as carboxymethylcellulose. Detection is based on changes in the fluorescence emission as a function of cell number deposited on the sensor. The sample is introduced using a nebulizer and the fiber probe, with the sensing film was placed directly inside a bioaerosol chamber. The sensor shows real-time responses to pulses of aerosolized bacteria such as Pseudomonas aeruginosa. The signals from the sensor are dependent on the humidity in the chamber. We have demonstrated that at lower humidities the ithegrated intensity does not provide a clear indication of the presence of bacterial aerosol. However, ftirther analysis shows that the intensity ratio at different wavelengths, for example I525/I560 or I505/I560, does correlate with bacteria concentration. The present detection limit for aerosolized bacteria is 3000 cells/mm2. To our knowledge, there are no previous reports of real-time detection of bacterial aerosols using the sensing film described here. The sensing film remains stable after storage under desiccation and in the dark for extended periods. The sensor also remains stable at room temperature for many hours after removal from the package.