Preparation and characterization of sugilite glass from basalt for α-amylase immobilization, statistical optimization of the immobilization process and description of free and immobilized enzyme.

Bacterial α-amylase was immobilized on sugilite from modified basalt rock as a new carrier. A set of glass compositions based on sugilite formula KNa2M2Li3Si12O30 (M = Al or Mn or Fe) were prepared. The glasses were prepared through melting-quenching technique and samples of glass were converted to glass ceramic. Among the tested glasses and glass ceramic only sugilite glass based on M = Fe (BSF) give promising results. The sugilite BSF glass was characterized using DSC analysis, FTIR absorption, and SEM. The sugilite glass revealed high thermal resistant till ∼770 °C. Under optimized conditions of the Central composite design, the immobilization yield improved by 4.7-fold. The affinity to starch increased after enzyme immobilization by 4.3-fold. The lower rate of deactivation constant and the increase of t ½ and D-value confirm the suitability of BSF and immobilization method in enhancing enzyme stability. The improvement in thermostability of immobilized α-amylase was judged by the change in thermodynamic parameters. In conclusion, the prepared sugilite BSF glass can be utilized as a new carrier suitable for stabilization of α-amylase enzyme by immobilization.

Catalytic, kinetic and thermodynamic properties of free and immobilized caseinase on mica glass-ceramics.

Bacillus megaterium 314 strain was able to utilize agricultural and industrial wastes for metallo-protease production. Orange peel and wheat bran were found as the most suitable carbon and nitrogen sources, respectively. Optimized production process enhanced the enzyme production by 5.1-folds. Glass and glass-ceramic with different particle sizes based on mica were used as inorganic carrier. Protease enzyme was immobilized by covalent bonding and physical adsorption methods on nanoparticle supports. Enzyme physically adsorbed on glass ceramic (particle size 0.71-1.0 mm) had the highest residual activity and the highest immobilization yield. Glass-ceramic was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Immobilized enzyme exhibited activation energy (E a ) and deactivation rate constant at 60 °C (k d ) about 1.29 and 1.46-times, respectively lower than free enzyme. Moreover, adsorbed enzyme had higher energy for denaturation (E d ), half-life (t 1/2 ), and decimal reduction time (D). The thermodynamic parameters of irreversible thermal denaturation for the protease enzyme indicate that immobilized enzyme had higher enthalpy (ΔH°), free energy (ΔG°), and entropy (ΔS°) than free one. There was a significant improvement in the maximum reaction velocity Vmax (2.5-fold), Michaelis constant Km (1.9-fold), and catalytic efficiency Vmax/Km (4.7-fold) values after immobilization indicating the efficiency and effectiveness of immobilization approach.

Cytotoxic effect of ferrimagnetic glass-ceramic nanocomposites on bone osteosarcoma cells.

This work pointed out the anti-cancer effect of ferrimagnetic glass ceramic nanocomposites (CaO-ZnO-Fe2O3-SiO2), which contain high amount of magnetite (∼60%), crystallite size <100nm, and different nucleating agents on bone cancer Saos-2 cells. The cell viability was inhibited by FH and FW to <50% and <25%, respectively, with/without magnetism, and both also reduced mitochondrial transmembrane potential (ΔYm), with/without magnetism (no influence of magnetism). Histone deacetylase (HDAC) activity was inhibited by FH, FW, and FHPNT, with/without magnetism. FHP3/magnetism resulted in HDAC inhibition. In absence of magnetism, FH and FW increased both necrotic and apoptotic cell death, while FW/magnetism induced late apoptosis. DNA fragmentation was increased by FH- and FW-treatment, with/without magnetism. At the same time, FW and FH/magnetism can efficiently induce the intrinsic apoptotic pathway in Saos-2 cells, whereas FW with/without magnetism and FH/magnetism enhanced cytochrome-C release. Similarly, caspase-7 activity was elevated by FH and FW, with/without magnetism. However, the presence of P2O5 in the composition of the nanocomposites inhibited their apoptotic properties and diminished their anti-cancer activity.

Effect of P2O5 and MnO2 on crystallization of magnetic glass ceramics.

This work pointed out the effect of adding P2O5 and/or MnO2 on the crystallization behavior of magnetic glass ceramic in the system Fe2O3·ZnO·CaO·SiO2·B2O3. The differential thermal analysis of the quenched samples revealed decrease in the thermal effects by adding P2O5 and/or MnO2 to the base sample. The X-ray diffraction patterns show the development of nanometric magnetite crystals in a glassy matrix. Heat treatment at 800 °C for 2 h, under reducing atmosphere, caused an increase in the amount of the crystallized magnetite with the appearance of minor hematite and Ca2SiO4. The transmission electron microscope revealed a crystallite size in the range 10-30 nm. Magnetic hysteresis cycles were analyzed with a maximum applied field of 25 kOe at room temperature. The prepared magnetic glass ceramics are expected to be useful for localized treatment of cancer.