SIMPLE ENTRAPMENT OF ALCALASE IN DIFFERENT SILICA XEROGELS USING THE TWO STEPS SOL-GEL METHOD

The present study has focused on the entrapment of Alcalase in different xerogels obtained by using various molar ratios of methyltriethoxysilane, dimethyldietoxisilane and tetraethoxysilane. Silica and their derivatives were characterized with regard to specific surface area (nitrogen adsorbtion), chemical composition (Fourier transform infrared spectroscopy (FT-IR)), weight loss upon heating (thermogravimetric analysis (TGA)) and catalytic activity

Entrapment of glucoamylase by sol-gel technique in PhTES/TEOS hybrid matrixes

Mesoporous silica particles were prepared by the sol-gel method from different alkoxysilane precursors and used as a host matrix for encapsulation of glucoamylase, an enzyme widely used in fermentative industry. The aim was to investigate the physico-chemical properties of the different silica powders and their effect on the enzyme kinetics. The encapsulated enzymes followed Michaelis-Menten kinetics. The Michaelis constant (KM) and the maximum rate of starch hydrolysis reaction (Vmax) were calculated according to the Michaelis-Menten and Lineweaver-Burke plots. The values of the Michaelis constant (KM) of the encapsulated enzymes were higher than those of the free enzyme. The temperature and pH infl uence on the activity of free and immobilized glucoamylase were also compared. The results of this study show that the enzymes immobilized in organic/inorganic hybrid silica matrixes (obtained by the sol-gel method), allowing the entrapped glucoamylase to retain its biological activity, are suitable for many different applications, (medicinal, clinical, analytical)

PRELIMINARY STUDY FOR USING VINYLTRIACETOXYSILANE AS PRECURSOR IN ENZYME IMMOBILIZATION BASED ON SOL-GEL METHOD

During the last years, sol-gel technology has become a well-established method for the preparation of catalytic active monoliths, bulk, particles and thin films. One reason for the increasing research activities in this field is the opportunity to obtain versatile hybrid materials by incorporation of different molecules, like dyes, enzymes, whole cells, chemicals and drugs. The aim of this research was to evaluate the suitability of vinyltriacetoxysilane (VTAS) as precursor in sol-gel enzyme immobilization and the physicochemical characterization of the final products (silica xerogels)

Performance of immobilized bacterial alpha-amylases in methyltriethoxsilane / tetraetoxysilane sol-gel matrices

The large number of studies related to the field of biomolecules encapsulation in sol-gel hosts clearly indicates that this approach can be considered as a powerful alternative to traditional encapsulation procedures involving biopolymer hosts. In this study, α-amylase was immobilized, by using the sol-gel technique, in silica particles obtained from hydrolysis and polycondensation of tetraethoxysilane (TEOS) and a mixture of methyltriethoxysilane (MTES) and tetraethoxysilane. The influence of the pH and temperature of free and immobilized α-amylase were compared. It was shown that the relative activities of immobilized enzymes are higher than those of free enzymes over broader pH and temperature ranges. The Michaelis constant and the maximum rate of starch hydrolysis reaction were calculated by fitting the experimental data to the Michaelis-Menten equation. It was found that KM and Vmax values of the immobilized enzyme were smaller than those of the free enzyme

Pore ordering in mesoporous matrices induced by different directing agents

Mesoporous silica particles of MCM - 41 type were synthesized by sol - gel method fr om tetraethyl orthosilicate (TEOS) in 2 - methoxyethanol and deionized water mixture in base conditions at room temperature. Ammonia or sodium hydroxides were used as catalysts and cetyl - trimethylammonium bromide (CTAB) and n - dodecyl - trimethylammonium bromid e (DTAB) as structure directing agents. The porosities and the ordered structure have been analyzed using transmission and scanning electron microscopy, small angle neutron and X - ray diffraction, nitrogen adsorption, thermal analysis and FTIR spectroscopy. The samples consist of spherical particles of sub - micrometer size, with radially arranged pores. The comparison of the effect of the different surfactants and catalysts shows that by varying the surfactant type and their proportion, the pore sizes can be controlled. As compared to the commonly used ammonia catalyst, the use of NaOH as catalyst results in a much smaller porosity of the as - prepared materials. These materials are not resisting to the heat treatment at 700 ºC used for the template removal, and the ordered porous structure is completely lost. Keywords: mesoporous silica, MCM - 41, hexadecyl - trimethylammonium bromide, dodecyl - trimethyl ammonium bromide

Gelatin content governs hydration induced structural changes in silica-gelatin hybrid aerogels – Implications in drug delivery

Silica-gelatin hybrid aerogels of varying gelatin content (from 4 wt.% to 24 wt.%) can be conveniently impregnated with hydrophobic active agents (e.g. ibuprofen, ketoprofen) in supercritical CO2 and used as drug delivery systems. Contrast variation neutron scattering (SANS) experiments show the molecular level hybridization of the silica and the gelatin components of the aerogel carriers. The active agents are amorphous, and homogeneously dispersed in these porous, hybrid matrices. Importantly, both fast and retarded drug release can be achieved with silica-gelatin hybrid aerogels, and the kinetics of drug release is governed by the gelatin content of the carrier. In this paper, for the first time, a molecular level explanation is given for the strong correlation between the composition and the functionality of a family of aerogel based drug delivery systems. Characterization of the wet aerogels by SANS and by NMR diffusiometry, cryoporometry and relaxometry revealed that the different hydration mechanisms of the aerogels are responsible for the broad spectrum of release kinetics. Low-gelatin (4–11 wt.%) aerogels retain their open-porous structure in water, thus rapid matrix erosion dictates fast drug release from these carriers. In contrast to this, wet aerogels of high gelatin content (18–24 wt.%) show well pronounced hydrogel-like characteristics, and a wide gradual transition zone forms in the solid-liquid interface. The extensive swelling of the high-gelatin hybrid backbone results in the collapse of the open porous structure, that limits mass transport towards the release medium, resulting in slower, diffusion controlled drug release

Áttétes vesedaganatos betegek kabozantinibterápiájának multicentrikus magyarországi eredményei

The aim of our analysis was to evaluate the efficacy of cabozantinib in patients with metastatic renal cell carcinoma. Cabozantinib therapy initiated between 01/01/2019 and 31/12/2022 was evaluated based on a retrospective review of data from 14 renal centers in Hungary. The starting dose was 60 or 40 mg. Physical examinations and laboratory tests were performed every 4 weeks and imaging studies 3-monthly. Tumor response was assessed according to RECIST 1.1, and toxicity according to NCI CTCAE 4.0. A total of 230 patient records were evaluated, 201 (87.4%) of them had clear cell RCC. Cabozantinib was administered as third, second and first-line treatment in 48.7%, 38.3% and <5% of cases, respectively. Dose reductions occurred in 62.6% and treatment interruption in 6.5%. Duration of therapy was 10.03 months, which was independent of dose reduction. Overall tumor response rate was 39.2% and clinical benefit was 82.8%. The duration of first-, second-, third- and fourth-line treatment was 11.47, 8.03, 11.57 and 10.13 months, respectively. Overall survival from the start of therapy was 22.0 months. Cabozantinib therapy in daily practice was more beneficial than according to registry study results. Dose reduction did not affect efficacy