Development of a based-chitin-chitinase nanostructured biosensor for the detection of fungal complex on papaya fruit during storage

Postharvest fungi significantly reduce the storage life of papaya fruit. Among the fungal cell wall components, chitin is an important biomolecule that could serve as a biomarker. This research aimed to develop a biosensor with immobilized chitinases on zinc oxide nanoparticles (ZnO-NPs) to recognize the chitin of phytopathogenic fungi of papaya fruit. The ZnO-NPs were less than 20 nm in size, as observed by TEM, and less than 1000 nm using DLS. In addition, flower-shaped structures were visualized with the use of SEM. Fourier transform infrared spectroscopy (FTIR) confirmed the main chitin and chitinase enzyme (NH and OH) functional groups and ZnO. The portable biosensor showed differences among papaya in terms of those with evident fungal growth (478 kHz), those without evident fungal growth (462 kHz), and papaya bought from a supermarket (464-481 kHz). Additionally, the presence of fungi in all treatments was confirmed, but the lowest incidence was in papaya without evident fungal growth. Thus, the biosensor could recognize fungi in papaya, an ability that could be implemented in the postharvest handling of this horticultural product in the future.