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    Near-infrared inducible supports in bio-catalysts design: A useful and versatile tool in enhancement of enzyme activity
    (Elsevier, 2024) Noma, Samir Abbas Ali; Dik, Gamze; Gurses, Canbolat; Kurucay, Ali; Topel, Seda Demirel; Ulu, Ahmet; Asiltuerk, Meltem
    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 Forster 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.
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    Preparation, characterization of upconverting nanoparticles for uricase immobilization and controlled manipulation of uricase activity by near-infrared light
    (Elsevier, 2024) Dik, Gamze; Noma, Samir Abbas Ali; Ulu, Ahmet; Topel, Seda Demirel; Asiltuerk, Meltem; Ates, Burhan
    In recent years, studies on the external stimulation of biotechnological enzyme drugs and their use in the treatment of diseases have gradually increased. Herein, for the first time, the near-infrared (NIR) was used as an external stimulant to manipulate the catalytic activity of the uricase (UOx) enzyme, which is used in the treatment of hyperuricemia, in a controlled manner. For this purpose, NaYF4: Yb3+, Er3+ upconverting nanoparticles (UCNPs) were synthesized by hydrothermal synthesis method and functionalized with diethylaminoethyldextran (DEAE-D) to facilitate UOx immobilization. The obtained materials were characterized in detail by various methods to confirm the preparation of UCNPs and immobilization of UOx. In addition, the biochemical parameters such as optimum pH, optimum temperature, thermal stability, and reusability were preliminarily investigated for free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx. Moreover, a sequential experimental method was monitored to assess the effects of NIR excitation intensity, induction distance, and exposure time on the UOx activity. While the optimum pH value was found to be 6.0 for both enzyme forms, the optimum temperature value was recorded as 45 and 50 degrees C for free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx, respectively. The activation energy (Ea) values of free UOx and NaYF4: Yb3+, Er3+/DEAE-D/UOx were calculated to be 7.59 and 2.98 kJ/mol, respectively, implying that the NaYF4: Yb3+, Er3+/DEAE-D/UOx was less temperature sensitive. After thermal incubation for 3 h at 55 degrees C, the NaYF4: Yb3+, Er3+/DEAE-D/UOx retained 54.68 % of its initial activity, while the free UOx retained 32.94 % of its initial activity at 50 degrees C. In addition, the findings from the reusability experiments revealed that NaYF4:Yb3+, Er3+/DEAE-D/UOx retained 57.94 % of its initial activity even after 10 reuse cycles. The most striking point in this study was the positive manipulation of UOx activity by NIR. Accordingly, it was observed that when the NIR power was 1500 mW, the UOx activity increased about 2 times compared to the control. Additionally, the UOx activity increased in parallel with the increase in NIR application time and the ideal application distance was 3 cm. In conclusion, this pioneering study provides valuable insights into the controlled manipulation of enzyme activity, showcasing the effectiveness of NIR in enhancing enzyme activity. The outcomes suggest that NIR holds great promise as an efficient, sustainable, and versatile approach applicable to various enzymatic catalysis scenarios.