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1.
The purpose of this work was to develop and optimize gliclazide-loaded alginate–methyl cellulose mucoadhesive microcapsules
by ionotropic gelation using central composite design. The effect of formulation parameters like polymer blend ratio and cross-linker
(CaCl2) concentration on properties of gliclazide-loaded alginate–methyl cellulose microcapsules like drug encapsulation efficiency
and drug release were optimized. The optimized microcapsules were subjected to swelling, mucoadhesive, and in vivo studies. The observed responses coincided well with the predicted values from the optimization technique. The optimized microcapsules
showed high drug encapsulation efficiency (83.57 ± 2.59% to 85.52 ± 3.07%) with low T
50% (time for 50% drug release, 5.68 ± 0.09 to 5.83 ± 0.11 h). The in vitro drug release pattern from optimized microcapsules was found to be controlled-release pattern (zero order) with case II transport
release mechanism. Particle sizes of these optimized microcapsules were 0.767 ± 0.085 to 0.937 ± 0.086 mm. These microcapsules
also exhibited good mucoadhesive properties. The in vivo studies on alloxan-induced diabetic rats indicated the significant hypoglycemic effect that was observed 12 h after oral
administration of optimized mucoadhesive microcapsules. The developed and optimized alginate–methyl cellulose microcapsules
are suitable for prolonged systemic absorption of gliclazide to maintain lower blood glucose level and improved patient compliance. 相似文献
2.
Natdanai Fafaungwithayakul Pranithi Hongsprabhas Parichat Hongsprabhas 《Food biophysics》2011,6(3):407-415
This study investigated physicochemical properties of soy soluble polysaccharide (SSP) and pectinase-hydrolysed soy soluble
polysaccharide (PH-SSP) from okara, the residue from soy milk production, and their influences when used as a fibre source
in oil-in-water (o/w) emulsions. Although pectinase hydrolysed only the carbohydrate fraction in SSP, it resulted in the self-association
of PH-SSP to the large-size aggregates. When PH-SSP was added to liquid emulsion containing 3.33% (w/v) rice bran oil and 3.75% (w/v) heated soy protein, it regulated the contents of protein in serum phase, sediment phase and at oil–water interface. The
types and contents of soy proteins in the serum phase and sediment phase could be manipulated by pre-heating of soy proteins
at 80 °C for 30 min and the addition of PH-SSP. The presence of PH-SSP (0–6% w/v) induced different distribution of proteins to the sediment phase and subsequent in vitro protein digestion in the emulsion.
Overall, this study proposed the means to design the distributions of proteins in different phases of o/w emulsion for different
degrees of oil release, emulsion stability and protein-polysaccharide coacervation during the course of in vitro peptic and
tryptic digestion. 相似文献
3.
The aim of this work was to develop a procedure for encapsulation of diltiazem HCl by spray coagulation. Factors affecting
the formulations such as the effect of NaCl on the solubility of diltiazem in alginate solution, surface tension, pH, viscosity
of the coagulation medium, and the effect of drug load on drug release were studied. The drug load was increased substantially
from 10 up to 320 mg/mL by adding 1.2% w/v NaCl in 1% w/v alginate solution. More stable microcapsules were obtained at pH 4.6 (acetate buffer) than at a pH 2.8 (lactic acid), and
the microencapsulation process was favored by the type of chitosan that produced low turbidity and viscosity in the coagulation
medium. A dose of 50 mg/mL of diltiazem HCl, 1.2% w/v NaCl, and chitosan CS allowed higher amount of drug to be encapsulated. The high water solubility of diltiazem HCl leads
to fast release from the microcapsules. 相似文献
4.
Synthesis of cyanophycin (multi-l-arginyl-poly-l-aspartic acid, CGP) in recombinant organisms is an important option to obtain sufficiently large amounts of this polymer
with a designed composition for use as putative precursors for biodegradable technically interesting chemicals. Therefore,
derivates of CGP, harbouring a wider range of constituents, are of particular interest. As shown previously, cyanophycin synthetases
with wide substrate ranges incorporate other amino acids than arginine. Therefore, using an organism, which produces the required
supplement by itself, was the next logical step. Former studies showed that Pseudomonas putida strain ATCC 4359 is able to produce large amounts of l-citrulline from l-arginine. By expressing the cyanophycin synthetase of Synechocystis sp. PCC 6308, synthesis of CGP was observed in P. putida ATCC 4359. Using an optimised medium for cultivation, the strain was able to synthesise insoluble CGP amounting up to 14.7 ± 0.7%
(w/w) and soluble CGP amounting up to 28.7 ± 0.8% (w/w) of the cell dry matter, resulting in a total CGP content of the cells of 43.4% (w/w). HPLC analysis of the soluble CGP showed that it was composed of 50.4 ± 1.3 mol % aspartic acid, 32.7 ± 2.8 mol % arginine,
8.7 ± 1.6 mol % citrulline and 8.3 ± 0.4 mol % lysine, whereas the insoluble CGP contained less than 1 mol % of citrulline.
Using a mineral salt medium with 1.25 or 2% (w/v) sodium succinate, respectively, plus 23.7 mM l-arginine, the cells synthesised insoluble CGP amounting up to 25% to 29% of the CDM with only a very low citrulline content. 相似文献
5.
Onanong Nuchuchua Usawadee Sakulku Napaporn Uawongyart Satit Puttipipatkhachorn Apinan Soottitantawat Uracha Ruktanonchai 《AAPS PharmSciTech》2009,10(4):1234-1242
The nanoemulsions composed of citronella oil, hairy basil oil, and vetiver oil with mean droplet sizes ranging from 150 to
220 nm were prepared and investigated both in vitro and in vivo. Larger emulsion droplets (195–220 nm) shifted toward a smaller size (150–160 nm) after high-pressure homogenization and
resulted in higher release rate. We proposed that thin films obtained from the nanoemulsions with smaller droplet size would
have higher integrity, thus increasing the vaporization of essential oils and subsequently prolonging the mosquito repellant
activity. The release rates were fitted with Avrami’s equations and n values were in the same range of 0.6 to 1.0, implying that the release of encapsulated limonene was controlled by the diffusion
mechanism from the emulsion droplet. By using high-pressure homogenization together with optimum concentrations of 5% (w/w) hairy basil oil, 5% (w/w) vetiver oil (5%), and 10% (w/w) citronella oil could improve physical stability and prolong mosquito protection time to 4.7 h due to the combination of
these three essential oils as well as small droplet size of nanoemulsion. 相似文献
6.
Sustained release mucoadhesive amoxicillin tablets with tolerance to acid degradation in the stomach were studied. The sustained-release
tablets of amoxicillin were prepared from amoxicillin coated with ethyl cellulose (EC) and then formulated into tablets using
chitosan (CS) or a mixture of CS and beta-cyclodextrin (CD) as the retard polymer. The effects of various (w/w) ratios of EC/amoxicillin, the particle sized of EC coated amoxicillin and the different (w/w) ratios of CS/CD for the retard polymer, on the amoxicillin release profile were investigated. The physicochemical properties
of the EC coated amoxicillin particles and tablets were determined by scanning electron microscopy, Fourier-transform infrared
spectroscopy, X-ray diffraction, and differential scanning calorimetry. The result showed that the release profiles of amoxicillin
were greatly improved upon coating with EC, while the inclusion of CD to the CS retardant additionally prolonged the release
of the drug slightly. Overall, a sustained release of amoxicillin was achieved using amoxicillin coated with EC at a (w/w) ratio of 1:1 and a particle size of 75–100 μm. Therefore, the tablet formulation of amoxicillin may be an advantageous alternative
as an orally administered sustained-release formulation for the treatment of peptic ulcers. 相似文献
7.
The purpose of this study was to investigate physicochemical characteristics and in vitro release of zidovudine from monolithic film of Eudragit RL 100 and ethyl cellulose. Films included 2.5% or 5% (w/w) zidovudine of the dry polymer weight were prepared in various ratios of polymers by solvent evaporation method from methanol/acetone
solvent mixture. The release studies were carried out by vertical Franz cells (2.2 cm2 area, 20 ml receptor fluid). Ex vivo studies were done on Wistar rat skin within the films F6 (Eudragit RL100) and F7 (Eudragit RL100/Ethylcellulose, 1:1) consisting
5% (w/w) zidovudine in comparison with the same amount of free drug. Either iontophoresis (0.1 and 0.5 mA/cm2 direct currents, Ag/AgCl electrodes) or dimethyl sulfoxide (pretreatment of 1% and 5%, w/w, solutions) were used as enhancers. Films consisting of ethyl cellulose under the ratio of 50% (w/w) gave similar release profiles, and the highest in vitro cumulative released amount was achieved with F6 film which gave the closest results with the free drug. This result could
be due to the high swelling capacity and re-crystallization inhibition effect of RL 100 polymer which also influenced the
film homogenization. All the films were fitted to Higuchi release kinetics. It was also observed that both 0.5-mA/cm2 current and 5% (w/w) dimethyl sulfoxide applications significantly increased the cumulative permeated amount of zidovudine after 8 h; however,
the flux enhancement ratio was higher for 0.5-mA/cm2 current application, especially within F6 film. Thus, it was concluded that Eudragit RL100 film (F6) could be further evaluated
for the transdermal application of zidovudine. 相似文献
8.
In this study, we have formulated chitosan-coated sodium alginate microparticles containing meloxicam (MLX) and aimed to investigate
the correlation between in vitro release and in vivo absorbed percentages of meloxicam. The microparticle formulations were prepared by orifice ionic gelation method with two
different sodium alginate concentrations, as 1% and 2% (w/v), in order to provide different release rates. Additionally, an oral solution containing 15 mg of meloxicam was administered
as the reference solution for evaluation of in vitro/in vivo correlation (ivivc). Following in vitro characterization, plasma levels of MLX and pharmacokinetic parameters [elimination half-life (t
1/2), maximum plasma concentration (C
max), time for C
max (t
max)] after oral administration to New Zealand rabbits were determined. Area under plasma concentration–time curve (AUC0–∞) was calculated by using trapezoidal method. A linear regression was investigated between released% (in vitro) and absorbed% (in vivo) with a model-independent deconvolution approach. As a result, increase in sodium alginate content lengthened in vitro release time and in vivo t
max value. In addition, for ivivc, linear regression equations with r
2 values of 0.8563 and 0.9402 were obtained for microparticles containing 1% and 2% (w/v) sodium alginate, respectively. Lower prediction error for 2% sodium alginate formulations (7.419 ± 4.068) compared to 1%
sodium alginate formulations (9.458 ± 5.106) indicated a more precise ivivc for 2% sodium alginate formulation. 相似文献
9.
Dlugokenski RE Sella SR Guizelini BP Vandenberghe LP Woiciechowski AL Soccol CR Minozzo JC 《Applied microbiology and biotechnology》2011,90(2):713-719
A novel low-cost medium was developed from by-products and wastes from the ethanol agro-industry to replace commercial media
in the production of a steam sterilization biological indicator (BI). Various recovery media were developed using soybean
or sugarcane molasses and vinasse to prepare a self-contained BI. Media performance was evaluated by viability and heat resistance
(D
121 °C value) according to regulatory standards. A medium produced with a soybean vinasse ratio of 1:70 (1.4%) (w/v) produced the results, with D
121 °C = 2.9 ± 0.5 min and Usk = 12.7 ± 2.1 min. The addition of 0.8% (w/v) yeast extract improved the germination of heat-damaged spores. The pH variation from 6.0 to 7.3 resulted in a gradual increase
in the D
121 °C value. The absence of calcium chloride resulted in a decrease in germination, while no significant differences were observed
with starch addition. Soybean vinasses may thus be used as the main component of a culture medium to substitute for commercial
media in the production of self-contained biological indicators. The use of ethanol production waste in this biotechnological
process realized a reliable performance, minimized the environmental impact, and decreased BI production costs while producing
a high quality product. 相似文献
10.
The benefits of controlling water activity, a
w, during enzymatically catalysed synthesis reactions, such as reverse-hydrolytic reactions promoted by lipases, are now well
recognized. Numerous techniques for controlling a
w in the laboratory and their implementation in continuous reactors have been discussed in the published literature. However,
in enzymatic interesterification reactions, such as acidolysis and transesterification, it is not appropriate merely to maintain
the a
w of the reaction system at one value since the two stages of the reaction, namely the cleavage of the original acyl bond and
the formation of a new one, are best carried out at different levels of water activity – the former at a high a
w and the latter at a lower one. The use of a continuous packed-bed hollow-fibre reactor has been described in this article
for carrying out solvent-free acidolysis of ethyl laurate with octanoic acid with in situ a
w control, using air that has been pre-equilibrated with saturated salt solutions to the desired a
w. At a single optimum (a
w = 0.54), the highest steady-state conversion to ethyl octanoate was 32%. However, it is possible to obtain a steady-state
conversion of 46% by operating the reactor with a step change in the water activity, from an initial value of unity to 0.23.
Received: 10 February 1998 / Received revision: 2 June 1998 / Accepted: 7 June 1998 相似文献
11.
In this study an attempt was made to prepare mucoadhesive microcapsules of gliclazide using various mucoadhesive polymers
designed for oral controlled release. Gliclazide microcapsules were prepared using sodium alginate and mucoadhesive polymer
such as sodium carboxymethyl cellulose (sodium CMC), carbopol 934P or hydroxy propylmethyl cellulose (HPMC) by orifice-ionic
gelation method. The microcapsules were evaluated for surface morphology and particle shape by scanning electron microscope.
Microcapsules were also evaluated for their microencapsulation efficiency, in vitro wash-off mucoadhesion test, in vitro drug release and in vivo study. The microcapsules were discrete, spherical and free flowing. The microencapsulation efficiency was in the range of
65–80% and microcapsules exhibited good mucoadhesive property in the in vitro wash off test. The percentage of microcapsules adhering to tissue at pH 7.4 after 6 h varied from 12–32%, whereas the percentage
of microcapsules adhering to tissue at pH 1.2 after 6 h varied from 35–68%. The drug release was also found to be slow and
extended for more than 16 h. In vivo testing of the mucoadhesive microcapsules in diabetic albino rats demonstrated significant antidiabetic effect of gliclazide.
The hypoglycemic effect obtained by mucoadhesive microcapsules was for more than 16 h whereas gliclazide produced an antidiabetic
effect for only 10 h suggesting that mucoadhesive microcapsules are a valuable system for the long term delivery of gliclazide. 相似文献
12.
Theodoros Goulas Athanasios Goulas George Tzortzis Glenn R. Gibson 《Applied microbiology and biotechnology》2009,82(3):471-477
A genomic library of Bifidobacterium bifidum (NCIMB 41171) DNA was constructed in Escherichia coli RA11r (melA−B+) and one α-galactosidase encoding gene was isolated. Conceptual translation combined with insertional mutagenesis analysis
indicated an open reading frame (ORF) of 759 amino acid (aa) residues encoding an α-galactosidase (named as MelA) of 82.8 kDa.
Partial purification and characterisation showed that the enzyme had an apparent native molecular mass of ≈243 kDa and a subunit
size of ≈85 kDa. The enzyme belongs to glycosyl hydrolases 36 family with high aa sequence similarities (≈73%) to other known
α-galactosidases of bifidobacterial origin. Under optimum pH conditions for activity (pH 6.0) and high melibiose concentration
(40% w/v), the enzyme was able to form oligosaccharides with degree of polymerisation (DP) ≥3 at higher concentration than DP = 2,
with a total yield of 20.5% (w/w). 相似文献
13.
T. Dennis Thomas 《In vitro cellular & developmental biology. Plant》2009,45(5):591-598
Protoplast culture and plant regeneration of an important medicinal plant Tylophora indica were achieved through callus regeneration. Protoplasts were isolated from leaf mesophyll cells and cultured at a density
of 5 × 105 protoplasts per gram fresh weight, which is required for the highest frequency of protoplast division (33.7%) and plating
efficiency (9.3%). The first division was observed 2 d after plating and the second division after 4 d. Culture medium consists
of Murashige and Skoog (MS) liquid medium with 4 μM 2,4-D, 0.4 M mannitol and 3% (w/v) sucrose with pH adjusted to 5.8. After 45 d of culture at 25°C in the dark, protoplasts formed colonies consisting of about
100 cells. The protoplast-derived microcalli were visible to the naked eye within 60 d of culture and reached a size of 0.2–0.4 mm
in diameter after 90 d. Calli of 0.2–0.4-mm size were transferred to MS medium supplemented with 2,4-D (4 μM), 3% (w/v) sucrose and 0.8% (w/v) agar, formed friable organogenic calli (7-8 mm size) after 8 wk under incubation in normal light period supplemented with
200 μmol m−2 S−1 of day light fluorescent illumination. The calli were transferred to MS medium supplemented with thidiazuron (TDZ) (1–7 μM)
and naphthalene acetic acid (NAA) (0.2–0.4 μM) for regeneration. The calli developed shoot buds after 3–4 wk, and the frequencies
of calli-forming shoots varied from 5% to 44%. Optimum shoot regeneration occurred on MS medium supplemented with 5 μM TDZ
and 0.4 μM NAA. On this medium, 44% cultures responded with an average number of 12 shoots per callus. Whole plants were recovered
following rooting of shoots in 1/2 MS medium supplemented with 3 μM indole 3-butyric acid. 相似文献
14.
S. A. Webster S. A. Mitchell W. A. Gallimore L. A. D. Williams M. H. Ahmad 《In vitro cellular & developmental biology. Plant》2008,44(2):112-118
A procedure for producing somatic embryos enriched with dibenzyl trisulfide (DTS) using a hormone-dependent culture system
is reported for Petiveria alliacea L. (Guinea hen weed). Leaf explants were cultured on a Murashige and Skoog medium supplemented with a range of naphthaleneacetic
acid (NAA) concentrations and a fixed concentration of benzyladenine (BAP) at 11.0 μM and sucrose or glucose at 30 g l−1. Leaf explants cultured on all media types started to form callus at the cut surfaces of the discs 10–14 d after initiation.
The type of sugar used influenced average fresh weight, the propensity to form roots, as well as the embryogenic response.
The highest mean fresh weight (337.7 ± 26.18 mg) and mean root number (23.7 ± 1.69) was produced on media enriched with sucrose
and supplemented with 53.7 μM NAA and 11.0 μM BAP. An ethanol extract of rhizogenic/embryogenic callus or somatic embryos
was subjected to high-performance liquid chromatography analysis, which revealed the presence of DTS in both extracts. UV
spectral analysis and the use of standard quantitation procedures showed that the quantity of DTS in the somatic embryo extract,
at 0.16% (w/v), was approximately 30-fold higher than in rhizogenic/embryogenic callus (0.0055% w/v) of similar fresh weight. These results indicate that it is possible to biosynthesize approximately 6 mg of natural DTS from
3,808 mg of fresh somatic embryos within 10 wk from less than three leaf explants. 相似文献
15.
Héctor Guzmán Doan Van-Thuoc Javier Martín Rajni Hatti-Kaul Jorge Quillaguamán 《Applied microbiology and biotechnology》2009,84(6):1069-1077
The paper reports a study involving the use of Halomonas boliviensis, a moderate halophile, for co-production of compatible solute ectoine and biopolyester poly(3-hydroxybutyrate) (PHB) in a
process comprising two fed-batch cultures. Initial investigations on the growth of the organism in a medium with varying NaCl
concentrations showed the highest level of intracellular accumulation of ectoine (0.74 g L−1) at 10–15% (w/v) NaCl, while at 15% (w/v) NaCl, the presence of hydroxyectoine (50 mg L−1) was also noted. On the other hand, the maximum cell dry weight and PHB concentration of 10 and 5.8 g L−1, respectively, were obtained at 5–7.5% (w/v) NaCl. A process comprising two fed-batch cultivations was developed—the first culture aimed at obtaining high cell mass
and the second for achieving high yields of ectoine and PHB. In the first fed-batch culture, H. boliviensis was grown in a medium with 4.5% (w/v) NaCl and sufficient levels of monosodium glutamate, NH4+, and PO43−. In the second fed-batch culture, the NaCl concentration was increased to 7.5% (w/v) to trigger ectoine synthesis, while nitrogen and phosphorus sources were fed only during the first 3 h and then stopped
to favor PHB accumulation. The process resulted in PHB yield of 68.5 wt.% of cell dry weight and volumetric productivity of
about 1 g L−1 h−1 and ectoine concentration, content, and volumetric productivity of 4.3 g L−1, 7.2 wt.%, and 2.8 g L−1 day−1, respectively. At salt concentration of 12.5% (w/v) during the second cultivation, the ectoine content was increased to 17 wt.% and productivity to 3.4 g L−1 day−1. 相似文献
16.
Biotransformation of steriodal saponins in Dioscorea zingiberensis C. H. Wright to diosgenin by Trichoderma harzianum 总被引:1,自引:0,他引:1
Lin Liu Yue-Sheng Dong Shan-Shan Qi Hui Wang Zhi-Long Xiu 《Applied microbiology and biotechnology》2010,85(4):933-940
Diosgenin is an important starting material in the steroidal hormone industry. Traditionally, diosgenin is mainly produced
by acid hydrolysis of Dioscorea zingiberensis C. H. Wright (DZW) tubers. This method yields numerous byproducts that can cause serious pollution. In this study, diosgenin
was obtained by biotransformation of steroidal saponins in DZW afforded by Trichoderma harzianum CGMCC 2979. The medium was optimized for maximum diosgenin production. The addition of phosphate buffer, surfactant Tween-85,
and Fe2+ increased the yield of diosgenin by 50.28%, 33.35%, and 22.07%, respectively. The optimum medium obtained by response surface
methodology was composed of 60 mmol l−1 phosphate buffer, 0.07% (w/v) Tween-85, and 0.93 mmol l−1 Fe2+. Under these conditions, a maximum diosgenin yield of 30.05 ± 0.59 mg g−1 was achieved, which was slightly higher than that obtained from traditional acid hydrolysis. By hydrolyzing the un-transformed
steroidal saponins after biotransformation, the total diosgenin yield increased by 35% compared to traditional method. Moreover,
chemical oxygen demand and residual reduced sugar in the wastewater produced by this integrated process were only 3.72% and
0.3%, respectively, that of the traditional acid hydrolysis method. 相似文献
17.
Meloxicam gel was designed based on the matching of the solubility parameter (δ) of the drug with that of the polymer and subsequently with skin for improved dermal delivery of meloxicam. The δ of meloxicam (11.48 (cal/cm3)0.5) determined by solubility measurement was matched statistically to the solubility parameter of monomers, n-vinyl-2-pyrrolidone, polyvinyl alcohol (PVA), hydroxyl ethyl methacrylate, ethylene glycol methacrylate (EGMA) determined
by intrinsic viscosity measurement. Consequently gels were formulated by polymerization in selected solvent blend of water/ethyl
acetate (20:80) in which the drug showed maximum solubility. Thus, F1–F16 formulations designed were evaluated for physicochemical
properties, textural analysis, and in vitro drug release. On the basis of optimum characteristics, F2 (PVA, δ = 16.96 (cal/cm3)0.5) and F8 (EGMA, δ = 18.35 (cal/cm3)0.5) formulated by suspension polymerization were selected and subjected to skin irritation and topical anti-inflammatory studies.
The formulation F8 demonstrated significant (p < 0.05) of anti-inflammatory activity in comparison to marketed piroxicam gel and was free from irritation. 相似文献
18.
Valence M. K. Ndesendo Viness Pillay Yahya E. Choonara Lisa C. du Toit Eckhart Buchmann Leith C. R. Meyer Riaz A. Khan Uwe Rosin 《AAPS PharmSciTech》2010,11(2):793-808
The purpose of this study was to develop and evaluate the bioadhesivity, in vitro drug release, and permeation of an intravaginal bioadhesive polymeric device (IBPD) loaded with 3′-azido-3′-deoxythymidine
(AZT) and polystyrene sulfonate (PSS). Modified polyamide 6,10, poly(lactic-coglycolic acid), polyacrylic acid, polyvinyl
alcohol, and ethylcellulose were blended with model drugs AZT and PSS as well as radio-opaque barium sulfate (BaSO4) and then
compressed into caplet devices on a tableting press. One set of devices was coated with 2% w/v pentaerythritol polyacrylic acid (APE-PAA) while another remained uncoated. Thermal analysis was performed on the constituent
polymers as well the IBPD. The changes in micro-environmental pH within the simulated human vaginal fluid due to the presence
of the IBPD were assessed over a period of 30 days. Textural profile analysis indicated that the bioadhesivity of the APE-PAA-coated
devices (3.699 ± 0.464 N; 0.0098 ± 0.0004 J) was higher than that of the uncoated devices (1.198 ± 0.150 N; 0.0019 ± 0.0001 J).
In addition, BaSO4-facilitated X-ray imaging revealed that the IBPD adhered to pig vaginal tissue over the experimental period
of 30 days. Controlled drug release kinetics was obtained over 72 days. During a 24-h permeation study, an increase in drug
flux for both AZT (0.84 mg cm−2 h−1) and PSS (0.72 mg cm−2 h−1) was realized up to 12 h and thereafter a steady-state was achieved. The diffusion and dissolution dynamics were mechanistically
deduced based on a chemometric and molecular structure modeling approach. Overall, results suggested that the IBPD may be
sufficiently bioadhesive with desirable physicochemical and physicomechanical stability for use as a prolonged intravaginal
drug delivery device. 相似文献
19.
Four species of brown seaweeds, namely Sargassum baccularia, Sargassum binderi, Sargassum siliquosum and Turbinaria conoides, harvested from Port Dickson, Negeri Sembilan, Malaysia were analysed for ash content, alginate yield and alginate properties.
Seaweeds calcined at 450°C were found to have low amount of non-combustible residue as these were not contaminated by calcareous
animals. Alginate was extracted from these seaweeds by two methods: hot and cold. In the hot method, the storing time was
3 h and the processing temperature was 50°C, whilst in the cold method, the sample was stored overnight at room temperature.
Higher yield of alginate was obtained by the hot method compared to the cold method, but alginate extracted by the cold method
gave higher molecular weight. In the hot method, 49.9% of alginate was extracted from S. siliquosum, followed by T. conoides (41.4%), S. binderi (38.9%) and S. baccularia (26.7%). Alginate extracted from T. conoides has an average molecular weight, M
w, of 8.06 × 105 g mol−1, whereas alginate from S. siliquosum was the lowest in M
w (4.81 × 105 g mol−1) when the extraction was done at room temperature. Alginate extracted from S. baccularia was found to be very heat-sensitive. Its M
w has dropped more than 83%, from 7.52 × 105 to 1.23 × 105 g mol−1, when the extraction temperature was raised. The effect of heat on the extent of depolymerisation of the alginate molecule
of the other three brown seaweed species was less significant, with decrease in molecular weight ranging between 13% and 16%. 相似文献
20.
Mode of depolymerisation of hemicellulose by various mannanases and xylanases in relation to their ability to bleach softwood pulp 总被引:2,自引:0,他引:2
G. M. Gübitz D. Haltrich B. Latal W. Steiner 《Applied microbiology and biotechnology》1997,47(6):658-662
Endo-mannanases and endo-xylanases cleave different heteromannans and xylans yielding mainly dimers and trimers of the corresponding
sugars as end-products. However, in the early stages of hydrolysis, four purified mannanases and four xylanases from fungal
and bacterial origin, examined in this study, showed a different pattern of released oligomers (determined up to the pentamers).
Furthermore, some of these enzymes showed a preference for cleaving the polysaccharides in the middle of the chain while others
acted more at the end. When the increase in the specific fluidity of mannan and xylan solutions per reducing sugar released
(K
v) was measured against the bleaching effect of the enzymes on softwood kraft pulp, a correlation was found. A xylanase from
Penicillium simplicissimum (K
v = 0.15 l mPa−1s−1g−1) and a mannanase from Sclerotium rolfsii (K
v = 0.12 l mPa−1s−1g−1) applied in a O(QX)P bleaching sequence (O = oxygen delignification, X = treatment with hemicellulolytic enzymes, Q = chelation
of metals, P = treatment with hydrogen peroxide in alkaline solution) gave a high brightness increase of 3.0% and 1.9% ISO
respectively. A less significant brightness increase was obtained with enzymes showing lower K
v values, such as a xylanase from Schizophyllum commune (Kv = 0.051 l mPa−1s−1g−1, 0.2% ISO) and a bacterial mannanase (K
v = 0.061 l mPa−1s−1g−1,0.5% ISO).
Received: 19 December 1996 / Received revision: 20 February 1997 / Accepted: 22 February 1997 相似文献