3.4 Sensors
Sensors are used in a wide range of areas including environmental and disease monitoring to detect and quantify selected analytes from complex dirty solutions. Effective sensors must have high selectivity, sensitivity, and structural stability over the range of environmental conditions they are likely to experience. Selectivity for a specific analyte in mixed samples is achieved by functionalizing the viral surface with metals, enzymes and/or other chemicals. For example, palladium-coated TMV rapidly and reversibly detects hydrogen at room temperatures [47]. Similarly, gold coated nanowires conjugated with folic acid via coupling agents can interact with the folate receptors on tumor cells to detect cancers with high sensitivity [19]. Additionally, TMV may be decorated with biotin to enable binding of enzymes to detect penicillin [61]. Other desirable sensor properties such as sensitivity and stability arise from the nature of viral biotemplates themselves. TMV’s high surface area to volume ratio allows for more contact with analytes, amplifying signal generation and improving device sensitivity [62]. Similarly, TMV structure is very stable in high temperatures and over a wide range of pHs (Table 1) that may be encountered in the analysis of complex mixtures, making biosensors derived from TMV more durable and rugged.