Near-infrared inducible supports in bio-catalysts design: A useful and versatile tool in enhancement of enzyme activity

Abstract

Immobilized enzymes have encountered two main challenges: Reduced enzyme activity compared to free enzymes and exhausted immobilized enzymes due to reusability. Herein, we suggested a promising activity enhancement strategy to overcome these challenges. The emission from upconversion nanoparticles (UCNPs) under near-infrared (NIR) excitation can increase the activity of PEG-l-ASNase due to Förster Resonance Energy Transfer. For this purpose, UCNPs were initially synthesized using the hydrothermal method. Subsequently, these UCNPs were functionalized with a polycationic polymer, branched polyethyleneimine (PEI), and the immobilization of PEG-l-ASNase was achieved through adsorption. We preliminarily explored the parameters such as enzyme concentration, incubation time, pH, temperature, reusability, storage stability, and kinetic study, etc. Further, the in vitro biocompatibility, hemolytic behavior, and anticancer activity of the produced UCNPs were also analyzed as crucial parameters. The results showed the pH durance, thermal and storage stability of the immobilized PEG-l-ASNases were enhanced. The immobilized PEG-l-ASNases maintained their activity to ≥55 % after 20 cycles. Enzyme immobilization led to a decrease in Km and Vmax compared to PEG-l-ASNase. In vitro assays revealed that immobilized enzyme further reduced the proliferation of human leukemia cell line (HL-60) upon NIR irradiation exposure but did not cause toxicity. This research may provide a new strategy to promote the catalytic activity of l-ASNase and demonstrates its potential application on human leukemia cells. Finally, these outcomes are valuable for the use of NIR induction in enzymatic reactions.