Cerium Oxide Nanoparticle-Papain Enzyme Bioconjugate: Synthesis, Characterization and Optical Absorption Study for Biomedical Applications

Abstract

Objective: Here, we synthesize cerium oxide nanoparticles, successfully characterize them, and study the interaction between enzymes and cerium oxide nanoparticles (CeO2 NPs) using a simple optical spectroscopic technique. Method: CeO2 was fabricated by chemical method. Characterizations were done using UV-Vis absorption spectra, FESEM images, and XRD data. For the biomolecular study, papain was used as a model enzyme. Two different concentrations of CeO2, namely a small concentration range (0.05810 to 0.40670 mM) and a large concentration range (0.58100 to 0.92961 mM), were taken to study the interaction with the papain. UV-Vis absorption spectra were recorded to study bioconjugate formation. Findings: The CeO2 NPs have an intense absorption peak at 352 nm and a band gap of 3.78 eV. The XRD pattern showed the unit cell is cubic with an average particle size of 41.36 nm. The binding of papain with CeO2 NPs resulted in a red shift in its absorption peak. The apparent association constant (Kapp) was calculated for the bioconjugate and found to be 0.747 × 103 M-1 for small concentrations and 0.278 × 103 M-1 for large concentrations. In large concentrations, aggregation occurs instead of corona formation. Novelty: To the best of our knowledge, this may be the first study of the interaction of papain enzyme with CeO2 NPs. This study contributes to the application of NPs in the field of biomedicine. Keywords: Cerium oxide, Papaya proteinase (PP), Absorption spectra, Bioconjugate, Association constant