pH regulated lactose inspired fabrication of zinc oxide nanoparticles for insulin sensing by LSPR absorption

Nanostructured metal oxide particles with diversified morphologies are in high demand in nanotechnology. The particle size, shape, and overall geometry mainly depend on the fabrication method. This study reports synthesis of zinc oxide nanoparticles (ZnO NPs) from zinc nitrate hexahydrate [Zn(NO₃)₂.6H₂O] precursor in aqueous media at 65 °C by using lactose from cow milk as a reducing agent and regulating pH from 6 to 10. UV-visible absorption gave maximum absorbance (λ_max) at 371-375 nm in ethanol for localized surface plasmon resonance (LSPR), FTIR exhibited bands at ca. 439-481 cm^-1 for stretching mode Zn-O bonds, and XRD peaks at 2 $$ values at 31.8, 34.45, and 36.28° confirmed the fabricated ZnO NPs. The XRD spectra also indicated that the ZnO crystallite (20-30 nm) has a hexagonal wurtzite structure. The average particle sizes measured by DLS were ca. 50-837 nm, and SEM microphotographs demonstrated the morphology of ZnO NPs with a hexagonal, rod-shaped, or spike-like structure. The ZnO NPs were used to investigate the LSPR absorption at various concentrations of insulin, ranging from 2.5 μM to 50 μM. The ZnO NPs fabricated at pH 7 and 10 showed better insulin sensing performance with high precision. The synthesis approach of ZnO NPs with variable morphologies would play a significant function in biomedical science especially real time monitoring of glucose for efficient management of diabetes.