A Positive Effect of Magnetic Field on the Catalytic Activity of Immobilized L-Asparaginase: Evaluation of its Feasibility

Design of near-infrared light induced functionalized upconverting nanoparticles as support in enzyme immobilization: Enhanced biocatalyst activity and stability

In this study, we hypothesized that the emission of upconverted nanoparticles (UCNP) can trigger PEG-L-ASNase (P-Lase) activity through Förster Resonance Energy Transfer under near-infrared (NIR) irradiation. To enhance stability and activity of P-Lase, it was immobilized on functionalized NaYF4:Yb3+, Er3+, Nd3+. Upon immobilization, the obtained NaYF4:Yb3+, Er3+, Nd3+/GPTMS-P-Lase exhibited excellent pH stability, thermal stability, metal ions or organic solvent tolerance, and storage stability. The relative activity of NaYF4:Yb3+, Er3+, Nd3+/GPTMS-P-Lase had about 65 % after 20 cycles and maintained 68 % and 59 % at +4 and 25 °C, respectively, after 4 weeks. Furthermore, in vitro cytotoxicity and hemolysis tests confirmed that the synthesized UCNPs were biocompatible. Most importantly, the activity of P-Lase was enhanced ≥4-fold under suitable NIR irradiation. It is reasonable to believe that this investigation may supply a novel technique to trigger the catalytic efficiency of P-Lase and may have promising application in leukemia treatment.

Improved L-Asparaginase Properties and Reusability by Immobilization onto Functionalized Carbon Xerogels

Enzyme immobilization can offer a range of significant advantages, including reusability, and increased selectivity, stability, and activity. In this work, a central composite design (CCD) of experiments and response surface methodology (RSM) were used to study, for the first time, the L-asparaginase (ASNase) immobilization onto functionalized carbon xerogels (CXs). The best results were achieved using CXs obtained by hydrothermal oxidation with nitric acid and subsequent heat treatment in a nitrogen flow at 600 °C (CX-OX-600). Under the optimal conditions (81 min of contact time, pH 6.2 and 0.36 g/L of ASNase), an immobilization yield (IY) of 100 % and relative recovered activity (RRA) of 103 % were achieved. The kinetic parameters obtained also indicate a 1.25-fold increase in the affinity of ASNase towards the substrate after immobilization. Moreover, the immobilized enzyme retained 97 % of its initial activity after 6 consecutive reaction cycles. All these outcomes confirm the promising properties of functionalized CXs as support for ASNase, bringing new insights into the development of an efficient and stable immobilization platform for use in the pharmaceutical industry, food industry, and biosensors.

Enhancement of enzyme activity by laser-induced energy propulsion of upconverting nanoparticles under near-infrared light: A comprehensive methodology for in vitro and in vivo applications

If the appropriate immobilization method and carrier support are not selected, partial decreases in the activity of enzymes may occur after immobilization. Herein, to overcome this challenge, an excitation mechanism that enables energy transfer was proposed. Modified upconverting nanoparticles (UCNPs) were constructed and the important role of near-infrared (NIR) excitation in enhancing the catalytic activity of the enzyme was demonstrated. For this purpose, UCNPs were first synthesized via the hydrothermal method, functionalized with isocyanate groups, and then, PEG-L-ASNase was immobilized via covalent binding. UCNPs with and without PEG-L-ASNase were extensively characterized by different methods. These supports had immobilization yield and activity efficiency of >96 % and 78 %, respectively. Moreover, immobilized enzymes exhibited improved pH, thermal, and storage stability. In addition, they retained >65 % of their initial activity even after 20 catalytic cycles. Biochemical and histological findings did not indicate a trend of toxicity in rats due to UCNPs. Most importantly, PEG-L-ASNase activity was triggered approximately 5- and 2-fold under in vitro and in vivo conditions, respectively. Overall, it is anticipated that this pioneering work will shed new light on the realistic and promising usage of NIR-excited UCNPs for the immobilization of enzymes in expensive and extensive applications.