Synthesis and characterization of Near-Infrared (NIR)-light triggerable upconverting nanoparticles to enhance activity of immobilized l-asparaginase

Abstract

In this study, PEG-L-ASNase enzyme was immobilized on UCNPs and its activity was improved by NIR. NaYF4: Yb3+, Er3+/PEI UCNPs were characterized to observe structural and morphological changes before/after enzyme immobilization. Additionally, optimum pH and optimum temperature values were determined for PEG-L-ASNase and NaYF4: Yb3+, Er3+/PEI-PEG-L-ASNase. While the optimum pH value was found to be 8.5 and 8 for PEG-L-ASNase and NaYF4: Yb3+, Er3+/PEI-PEG-L-ASNase, the optimum temperature values were determined as 40 oC and 45 oC, respectively. Also, after incubation at 50 °C for 6 hours, it was observed that PEG-L-ASNase and NaYF4: Yb3+, Er3+/ PEI-PEG-L-ASNase retained 28% and 59% of their initial activities, respectively. Moreover, the kinetic parameters (Km and Vmax) were calculated. These values for PEG-L-ASNase were found as 2.31 ± 0.04 mM and 140.85 ± 3.23 μmol/min, respectively. For NaYF4: Yb3+, Er3+/PEI-PEG-L-ASNase, the Km and Vmax values were calculated as 1.56 ± 0.06 mM and 138.89 ± 1.66 μmol/min, respectively. Finally, it was determined that the application of NIR at 800 mW, for 60 min at 1 cm increased the activity approximately 4 times compared to the PEG-L-ASNase. As a result, L-ASNase was successfully immobilized and the activity of the immobilized enzyme was increased approximately 4 times by using NIR light. Also, in this study is one of the pioneering studies in terms of the development of triggerable drug delivery systems.