14 research outputs found
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
Hybrid silica-metalloporphyrin nanomaterials exhibiting intensive absorption of light in the red-region
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 ÂșC 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 â 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 (4â11 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 (18â24 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
ĂttĂ©tes vesedaganatos betegek kabozantinibterĂĄpiĂĄjĂĄnak multicentrikus magyarorszĂĄgi eredmĂ©nyei
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