Microwave non-thermal effect reduces ELISA timing to less than 5 minutes

Abstract

This report demonstrates that microwave-mediated ELISA, which occurs in less than 5 minutes, is due to a microwave non-thermal or a microwave-specific effect rather than the microwave heating effect. To decipher the non-thermal effect, we have designed a system that mimics the time-dependent temperature rise of a reaction mixture or buffer in the wells of a polystyrene microtiter plate similar to that of microwave exposure. This system is used as an alternative to the microwave thermal effect (microwave-thermal-alternate or MTA). We have carried out ELISA for the detection of human IgG in a time-dependent manner under microwave irradiation in a microwave oven, and by thermal incubation by a specially designed MTA. ELISA results carried out by microwave exposure in 4 min 40 s are akin to 18 h conventional ELISA, whereas no significant ELISA values are obtained by microwave-thermal-alternate, illustrating the predominance of the microwave non-thermal effect over the microwave thermal effect in microwave-mediated ELISA. We postulate that the microwave specific effect is a microwave catalytic effect acting by lowering the activation energy of reactants.