Covalent immobilization and characterization of penicillin G acylase on amino and GO functionalized magnetic Ni0.5Zn0.5Fe2O4@SiO2 nanocomposite prepared via a novel rapid-combustion process

Enhanced catalytic performance of penicillin G acylase by covalent immobilization onto functionally-modified magnetic Ni0.4Cu0.5Zn0.1Fe2O4 nanoparticles

With the emergence of penicillin resistance, the development of novel antibiotics has become an urgent necessity. Semi-synthetic penicillin has emerged as a promising alternative to traditional penicillin. The demand for the crucial intermediate, 6-aminopicillanic acid (6-APA), is on the rise. Enzyme catalysis is the primary method employed for its production. However, due to certain limitations, the strategy of enzyme immobilization has also gained prominence. The magnetic Ni0.4Cu0.5Zn0.1Fe2O4 nanoparticles were successfully prepared by a rapid-combustion method. Sodium silicate was used to modify the surface of the Ni0.4Cu0.5Zn0.1Fe2O4 nanoparticles to obtain silica-coated nanoparticles (Ni0.4Cu0.5Zn0.1Fe2O4-SiO2). Subsequently, in order to better crosslink PGA, the nanoparticles were modified again with glutaraldehyde to obtain glutaraldehyde crosslinked Ni0.4Cu0.5Zn0.1Fe2O4-SiO2-GA nanoparticles which could immobilize the PGA. The structure of the PGA protein was analyzed by the PyMol program and the immobilization strategy was determined. The conditions of PGA immobilization were investigated, including immobilization time and PGA concentration. Finally, the enzymological properties of the immobilized and free PGA were compared. The optimum catalytic pH of immobilized and free PGA was 8.0, and the optimum catalytic temperature of immobilized PGA was 50°C, 5°C higher than that of free PGA. Immobilized PGA in a certain pH and temperature range showed better catalytic stability. Vmax and Km of immobilized PGA were 0.3727 μmol·min-1 and 0.0436 mol·L-1, and the corresponding free PGA were 0.7325 μmol·min-1 and 0.0227 mol·L-1. After five cycles, the immobilized enzyme activity was still higher than 25%.

Immobilization and property of penicillin G acylase on amino functionalized magnetic Ni0.3Mg0.4Zn0.3Fe2O4 nanoparticles prepared via the rapid combustion process

Penicillin G acylase plays an important role in the biocatalytic process of semi-synthetic penicillin. In order to overcome the disadvantages of free enzymes and improve the catalytic performance of enzymes, it is a new method to immobilize enzymes on carrier materials. And magnetic materials have the characteristics of easy separation. In the present study, the Magnetic Ni0.3Mg0.4Zn0.3Fe2O4 nanoparticles were successfully prepared by a rapid-combustion method and calcined at 400°C for 2 h. The surface of the nanoparticles was modified with sodium silicate hydrate, and the PGA was covalently bound to the carrier particles through the cross-linking of glutaraldehyde. The results showed that the activity of immobilized PGA reached 7121.00 U/g. The optimum pH for immobilized PGA was 8 and the optimum temperature was 45°C, the immobilized PGA exhibited higher stability against changes in pH and temperature. The Michaelis–Menten constant (Km) values of the free and immobilized PGA were 0.00387 and 0.0101 mol/L and the maximum rate (Vmax) values were 0.387 and 0.129 μmol/min. Besides, the immobilized PGA revealed excellent cycling performance. The immobilization strategy presented PGA had the advantages of reuse, good stability, cost saving and had considerable practical significance for the commercial application of PGA.

Comparative study of poly tannic acid functionalized magnetic particles before and after modification for immobilized penicillin G acylase

In this work, Fe₃O₄ nanoparticles (NPs) was synthesized by inverting microemulsion method. After that, based on the physical and chemical properties of tannic acid (TA), poly tannic acid (PTA) was coated on Fe₃O₄ NPs surface. Fe₃O₄ NPs coated with PTA, on the one hand, was used to immobilize Penicillin G acylase (PGA) by physical adsorption. On the other hand, it was modified by glutaraldehyde (GA). GA grafting rate (G_r-GA) was optimized, and the G_r-GA was 30.0% under the optimum conditions. Then, through the Schiff base reaction between the glutaraldehyde group and PGA amino group, this covalent immobilization of PGA was further realized under mild conditions. Finally, the structures of every stage of magnetic composites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibration magnetometer (VSM) and transmission electron microscopy (TEM), respectively. The results indicated that the enzyme activity (EA), enzyme activity recovery (EAR) and maximum load (ELC) of the immobilized PGA were 26843 U/g, 80.2% and 125 mg/g, respectively. Compared to the physical immobilization of PGA by only coating PTA nanoparticles, further modified nanoparticles by GA showed higher catalytic stability, reusability and storage stability.

Immobilized penicillin G acylase with enhanced activity and stability using glutaraldehyde-modified polydopamine-coated Fe3 O4 nanoparticles

In this work, Fe₃ O₄ nanoparticles (NPs) were coated with polydopamine (PDA) to structure Fe₃ O₄ @PDA NPs by the spontaneous oxygen-mediated self-polymerization of dopamine (DA) in an aqueous solution of pH = 8.5. The fabricated Fe₃ O₄ @PDA NPs were grafted by glutaraldehyde to realize the immobilization of penicillin G acylase (PGA) under mild conditions. The carriers of each stage were characterized and investigated by transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and vibrating sample magnetometry. To improve the catalytic activity and stability of immobilized PGA, the immobilization conditions were investigated and optimized. Under the optimal immobilization conditions, the enzyme loading capacity, enzyme activity, and enzyme activity recovery of immobilized PGA were 114 mg/g, 26,308 U/g, and 78.5%, respectively. In addition, the immobilized PGA presented better temperature and pH stability compared with free PGA. The reusability study ensured that the immobilized PGA showed an excellent repeating application performance. In particular, the recovery rate of immobilized PGA could reach 94.8% and immobilized PGA could retain 73.0% of its original activity after 12 cycles, indicating that the immobilized PGA exhibited a high operation stability and broad application potential in the biocatalysis field.

Immobilization and Evaluation of Penicillin G Acylase on Hydroxy and Aldehyde Functionalized Magnetic α-Fe2O3/Fe3O4 Heterostructure Nanosheets

Magnetic α-Fe2O3/Fe3O4 heterostructure nanosheets were fabricated via hydrothermal calcination. The activity of penicillin G acylase (PGA), which was covalently immobilized onto silica-decorated heterostructure nanosheets, achieved the highest activity of 387.03 IU/g after 18 h of incubation with 0.1 ml of PGA. In contrast, the activity of free PGA reached the highest level when the temperature was 45°C with a pH of 8.0. However, the activity of free PGA changed more dramatically than immobilized PGA as the relative conditions changed. Moreover, the Michaelis-Menten constant (Km) and reusability of immobilized PGA were also explored. The results showed that free PGA Km and maximum rate (Vmax) were 0.0274 M and 1.167 μl/min, respectively. Km and Vmax values of immobilized PGA were 0.1082 M and 1.294 μl/min, respectively. After 12 cycles of repetitive use, immobilized PGA remained approximately 66% of its initial activity, indicating that the PGA immobilized onto the heterostructure nanosheets showed better stability and reusability than free PGA.

Surface Modulation of Graphene Oxide for Amidase Immobilization with High Loadings for Efficient Biocatalysis

As a type of important and versatile biocatalyst, amidase immobilization on solid materials has received broad attention with its relatively easy procedure and available reusability. However, current porous supports have suffered from limited loadings, and it is highly desired to develop a new type of material with abundant space so as to ensure a high loading of amidase. Here, graphene oxide was adopted as the support for amidase immobilization, which showed the highest loading capacity for amidase (~3000 mg/g) to date. To the best of our knowledge, it is the first case of amidase immobilized on graphene oxide. Through surface modulation via reducing the contents of oxygen-containing functional groups, activity recovery of immobilized amidase increased from 67.8% to 85.3%. Moreover, surface-modulated graphene oxide can efficiently uptake amidase under a wide range of pH, and the maximum loading can reach ~3500 mg/g. The resultant biocomposites exhibit efficient biocatalytic performance for asymmetric synthesis of a chiral amino acid (i.e., L-4-fluorophenylglycine, an intermediate of aprepitant).

Magnetic thermosensitive polymer composite carrier with target spacing for enhancing immobilized enzyme performance

A novel magnetic thermosensitive polymer composite carrier with target spacing was developed. In this strategy, thermosensitive polymer grafted on magnetic Fe₃O₄ for enhancing immobilized penicillin G acylase (PGA) performance and introduce immobilized target spacing into magnetic carriers for the first time. Fe₃O₄ nanoparticles were synthesized by a reverse microemulsion method. The modifier used was the silane coupling agent γ-methylacryloxypropyl trimethoxysilane (KH570) and then reacting with a reversible-adaptive fragmentation chain transfer (RAFT) reagent, 2-cyano-2-propyldodecyl trithiocarbonate (CPDTC). The thermo-sensitive nanoparticle-composite carrier of Fe₃O₄-grafted-poly N, N-diethyl acrylamide-block-poly β-Hydroxyethyl methacrylate-block-random copolymer of glycidyl methacrylate and methyl methacrylate (Fe₃O₄-g-PDEA-b-PHEMA-b-P(MMA-co-GMA)) were synthesized by RAFT polymerization technique that used N, N-diethyl acrylamide (DEA), β-Hydroxyethyl methacrylate (HEMA), Glycidyl methacrylate (GMA) and Methyl methacrylate (MMA) as monomer, then which were employed as functional carriers for the immobilization of PGA. Within the carrier, the epoxy group of GMA segment was a target immobilization site for PGA and the introduction of MMA reflected the target space of immobilized PGA to improve catalytic activity and catalytic activity recovery rate of the immobilized PGA. Characterizations demonstrated that the triblock copolymers grafted Fe₃O₄ nanoparticles were successfully fabricated by the structure design. Besides, under these circumstances the enzyme activity (EA), enzyme loading capacity (ELC) and catalytic activity recovery ration (CAR) reached 31235 U/g, 128.39 mg/g and 93.32 %, respectively. The catalytic activity of immobilized PGA maintained 87.4 % of initial value and the recovery ratio (R) of immobilized PGA reached 96.22 % after recycling 12 times. Furthermore, the immobilized PGA exhibited advantages of low temperature homogeneous catalysis and magnetic separation, which indicated broad application prospects in the biocatalysts' field.

Improved delivery system for celastrol-loaded magnetic Fe3O4/α-Fe2O3 heterogeneous nanorods: HIF-1α-related apoptotic effects on SMMC-7721 cell

Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods were prepared by a rapid combustion method with α-FeOOH nanorods as precursors. Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods with a saturation magnetization of 33.2 emu·g^-1 were obtained using 30 mL of absolute ethanol at a calcination temperature of 300 °C. Their average length was around 140 nm, and average diameter was about 20 nm. To improve the dispersion characteristics of the Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods in aqueous solution, citric acid and PEG were applied to modify the nanorod surface via the Mitsunobu reaction. The results showed that the hydrodynamic size range of Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol was 250-500 nm, the surface potential was -15 mV, and the saturation magnetization was approximately 23 emu·g^-1. The drug loading capacity of Fe₃O₄/α-Fe₂O₃/CA-PEG was larger than the non-PEG modified version. Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol had slow-release characteristics and was sensitive to changes in pH. Application of a magnetic field significantly promoted the inhibition of SMMC-7721 human liver cancer cell growth after treatment with Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol. Celastrol and Fe₃O₄/α-Fe₂O₃/CA-PEG-celastrol increased the production of reactive oxygen species in SMMC-7721 cells and promoted apoptosis and apoptosis-related proteins (p53, Bax, Bcl-2) were also changed. In addition, the expression of hypoxia-inducible factor 1α (HIF-1α) was enhanced. We may conclude that celastrol-loaded magnetic Fe₃O₄/α-Fe₂O₃ heterogeneous nanorods may be applied in the chemotherapy of human cancer with good biocompatibility and delivery.

Delivery of apigenin-loaded magnetic Fe2O3/Fe3O4@mSiO2 nanocomposites to A549 cells and their antitumor mechanism

This study introduces a mesoporous magnetic nano-system for the delivery of apigenin (API). A targeted therapeutic drug delivery system was prepared based on Fe₂O₃/Fe₃O₄@mSiO₂-HA nanocomposites. Magnetic Fe₂O₃/Fe₃O₄ heterogeneous nanoparticles were first prepared via the rapid-combustion process. The effects of solvent type, solvent volume, calcination temperature, and calcination time on the crystal size and magnetism of the Fe₂O₃/Fe₃O₄ heterogeneous nanoparticles were investigated. The mesoporous silica shell was deposited on the Fe₂O₃/Fe₃O₄ heterogeneous nanoparticles using an improved Stöber method. HA was exploited as the targeting ligand. The specific surface area of the Fe₂O₃/Fe₃O₄@mSiO₂ nanocomposites was 369.6 m²/g, which is 19 times higher than that of the magnetic Fe₂O₃/Fe₃O₄ heterogeneous nanoparticle cores. Drug release properties from the Fe₂O₃/Fe₃O₄@mSiO₂-HA nanocomposites were studied, and the result showed that API-loaded nano-system had sustained release effect. Prussian blue staining and electrochemical performance variation showed that an external magnetic field facilitated cell uptake of Fe₂O₃/Fe₃O₄@mSiO₂-HA nanocomposites. MTT assays showed that the cell inhibition effect of API-Fe₂O₃/Fe₃O₄@mSiO₂-HA was stronger than that of free API at the same drug dose under a magnetic field and Fe₂O₃/Fe₃O₄@mSiO₂-HA nanocomposites showed good biocompatibility. Fluorescence imaging, flow cytometry, western blot, reactive oxygen species (ROS), Superoxide dismutase (SOD) and malondialdehyde (MDA) kits verified that the enhanced therapeutic action was due to the promotion of apoptosis, lipid peroxidation, and ferroptosis. The magnetic nano-system (Fe₂O₃/Fe₃O₄@mSiO₂-HA) showed good magnetic targeting and active hyaluronic acid targeting, and has the potential to provide a targeted delivery platform for many antitumor drugs.

Immobilization and characterization of cellulase on hydroxy and aldehyde functionalized magnetic Fe2O3/Fe3O4 nanocomposites prepared via a novel rapid combustion process

In this work, magnetic Fe₂O₃/Fe₃O₄ nanocomposites were prepared via a novel rapid combustion process. The silica was precipitated on the surface of Fe₂O₃/Fe₃O₄ nanocomposites. The silica-coated magnetic nanocomposites were cross-linked with glutaraldehyde, on which cellulase was covalently immobilized. The morphology, composition, and property of the prepared nanomaterials were characterized by the scanning electron microscopy (SEM), the energy dispersive spectrometry (EDS), the X-ray diffraction (XRD), the vibrating sample magnetometer (VSM), and the Fourier transform infrared (FTIR) spectroscopy. The immobilization conditions were optimized by varying operating parameters and determined to be 0.05 mL of 0.5% cellulase solution for 2 h. The catalytic stabilities of the immobilized cellulase were evaluated. The results showed that the immobilized cellulases performed higher apparent activity at pH 4.5 and exhibited good thermal stability compared with their free counterparts. The Michaelis-Menten equation showed that K_m and V_max of free cellulase were 3.46 mol·L^-1 and 0.53 mol·min^-1, respectively. The immobilized cellulase had higher K_m and V_max (18.99 mol·L^-1 and 0.59 mol·min^-1). The retained activity of the immobilized cellulase maintained over 71% of the initial activity after being used for five cycles.