Enzyme nanoparticles and their biosensing applications: A review.

Enzyme nanoparticles (ENPs) are the aggregates of enzymes in the nano scale (10-100 nm). These ENPs have been characterized by transmission electron microscopy (TEM), fourier transformation infrared spectroscopy (FTIR), UV-Visible spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Enzymes are the biocatalysts exhibiting substrate specificity, catalytic activity, regulator of various metabolic reactions under mild conditions and hence, used as industrial catalysts efficiently. Due to these extraordinary properties of enzymes, they have been used for the diagnosis and treatment of various diseases. However, direct application to enzymes has increased the chances of degradation and thus lowers the performance of analytical devices. Therefore these limitations have been overcome by synthesizing the nanoparticles (NPs) of enzyme. As ENPs have exhibited extraordinary properties such as large surface to volume ratio, unique optical, thermal and chemical than native enzymes. ENPs based biosensor work optimally within 2-300s, pH range 5.0-6.0 and temperature 3.5-45°C. The linear range of ENPs based biosensor varies between 0.0001 and 100000 μM and detection limit 0.0002-550 μM. These biosensors have been used for the diagnosis of various diseases such as cardiovascular diseases, renal disorders, diabetes, environment monitoring, and biochemical engineering and reused up to 8-200 times over a period of 60-240 days while stored dry at 4°C. Therefore, the future research should be focused to understand the interaction of ENPs with their analyte and further improvement and commercialization of ENPs based biosensor are discussed. Present review article deciphers the various methods of ENPs preparation, their characterization and ENPs based biosensors.