Papers by Keyword: Enzymatic Degradation

Abstract: Oral colon targeted drug delivery system can be divided into pH dependent, time-dependent, enzymatic degradation etc. according to the ways of drug delivery. Mechanism of drug delivery, preparation method and application of oral colon targeted drug delivery system were introduced. In addition, it previewed the research direction of colon targeted drug delivery in the future, to provide a reference for the targeted new dosage form.

Abstract: Guar gum was subjected to degradation in high concentration aqueous solution by enzymatic treating to obtain high concentration low molecular weight guar gum for fracturing. The study indicates that the high concentration guar gum aqueous solution can be degraded effectively by enzymatic treating. The enzymatic treating conditions were investigated and the optical enzymatic treating pH, temperature and enzyme add amount are respectively 6, 50°C and 0.1g/L, and various of low molecular weight guar gum with different molecular weight can be obtained by controlling the enzymatic treating time.

Abstract: To investigate the biodegradability of PBS, films made of PBS were subjected to enzymatic degradation. The declining thermal stability and XRD diagrams showed that the crystallinity of PBS was reduced after degradation. SEM results confirmed that the mode of enzymatic degradation was surface corrosion. In addition, the weight loss of the material did not experience the so-called acclimation period, but showed a typical linear growth process.

Abstract: In order to confirm the feasibility of porous rice starch granules and PBAT blends as biodegradable composites, their degradability were carried out. Enzymatic degradability evaluation showed that α-amylase degradation of starch increased as the starch content in the blend increased. Burial test of the blends for 1-4 months was carried out and the rate of degradation of the PBAT/porous starch blend was confirmed to be slower than those of PBAT/native rice starch blend. Observation of the film blends structure by scanning electron microscope revealed that the starch was dispersed in a PBAT matrix. Furthermore, changes in the film surface after enzyme treatments were observed. The results obtained from the degradability of the porous starch granules and PBAT blends showed that this bio-composite was relatively slow, regarding as controllable degradation material.

Abstract: Lipase Novozym 435 was used as catalyst to degrade P(BS-co-DGS), which was a kind of PBS-based copolyester modified with diethylene glycol (DEG), in a THF/toluene mixed solvent system. P(BS-co-DGS) copolyesters were synthesized by copolymerization and characterized by ¹H NMR. GPC and TGA were used to investigate average molecular weight and thermal property before and after degradation, respectively. After degraded by N435 for 30 h, the M_n of P(BS-co-DGS)10 (DEG content 10%) decreased from 8.33×10⁴ to 3.52×10⁴ g·mol^-1 with some yellow oil droplets of oligomers appearing. And the initial decomposition temperature (the temperature at 5% mass loss) of P(BS-co-DGS)10 changed from 300.6 to 178.9. MALDI-TOF-MS results showed that none of DEG oligomers appeared in P(BS-co-DGS)10 degradation products. However, when the DEG content increased to 20%, there were the DEG circle oligomers as well as linear oligomers in the degradation products.

Abstract: A porcine ADM was prepared by the means of combined treatments with alkali, enzymes, sodium lauryl sulfate (SDS) and NaCl solution. Concentration and process time of enzymes were varied respectively, and their effects on properties of ADM were evaluated, such as porosity, mechanical properties, enzymatic degradation. The composition of ADM was detected with an amino acid analyzer, and its microstructure was observed under SEM. To estimate its cytocompatibility, cells proliferation tests were performed by MTT assay, and cells distribution was viewed under CLSM. With increase of enzymes concentration and process time, the porosity of ADM was enhanced, but its ultimate tensile strength was weakened. And enzymatic process time affected the degradation rate of ADM in collagenase solution greatly. The obtained ADM framework had interconnected pores at about 100 μm in diameter. The MTT assay and CLSM image indicated that cells cultured on ADM proliferated well and distributed evenly. The prepared ADM has good microstructure, high mechanical properties, controlled enzymatic stability and good cell compatibility, and it has great potential use in the tissue engineering for further study.

Abstract: Ether based polyurethane film was synthesized and those were undergone curing process and membrane thickness was measured. The membrane was sliced in 2×2cm. Swelling study of the membrane was compared in water, tetrahydrofuran solvent and simulated body fluid. Membranes were set for biodegradation in simulated body fluid for three months. Besides that films were also degraded by esterase enzyme. Result of the two types of degradation was compared. After biodegradation characterization by FTIR-ATR mode, XRD was done for the degraded membranes and the characterization result was compared with that of no degraded membranes. To perform drug release study with antibiotic-ciprofloxacin, the membrane was first loaded with ciprofloxacin by placing in a drug solution of known concentration and then drug release pattern was verified periodically by estimating optical density (OD) of the different solutions of released drug by UV-VIS spectrophotometer. Then antibiotic assay was performed with ciprofloxacin with the S. aureus strain and the obtained zone of inhibition was compared with the control sample. The drug release results were compared with antibiotics assay results. Besides that drug release was correlated with the degradation study results.

Abstract: Enzymatic degradation tests of polymer in form of nanoparticle (NP) were used to study the biodegradation of two different types of polymers polytetramethylene adipitate (SP4/6) and polybutylene isophthalate (PBI) by two commercially available lipases. The two lipases, which are from the yeast Candida cylindracea (CcL) and Pseudomonas species (PsL) respectively, exhibited sufficient degradation activities both for the aliphatic model polyester SP4/6 and the aromatic model polyester PBI and the use of polyester NPs has dramatically shortened the duration of enzymatic degradation tests. It has also been noticed that the degradation percentage of the polyesters was in the range of 35-50%, probably due to the formation of low molecular weight intermediates that are not accessible to the enzymes. Since biodegradation of polymers is a surface process, the adsorption of lipases on the surface of polyester NPs may play an important role. In order to gain some insights into the adsorption process of enzymes on polymer NPs, the adsorption of CcL and PsL lipases on two hardly degradable polyesters polybutylene terephthalate (PBT) and polyethylene terephthalate (PET) was investigated in this work. The adsorption of lipases on these polyester NPs showed a fast kinetic. Langmuir isotherms were found to be generally suitable to describe the adsorption of lipases on polyester NPs, especially at low lipase concentration under the experimental conditions. However, significant derivations from Langmuir isotherms were observed at high lipase concentrations.

Abstract: Konjac glucomannan with different molecular weights/poly(acrylic acid) hydrogels were prepared in this paper. The structure of the IPN hydrogels was characterized by FT-IR and SEM. The swelling ratio of these hydrogels showed they had pH-sensitive properties and the enzymatic degradation tests showed the hydrogels retain the enzymatic degradation character of KGM. Furthermore, hydrogel composed of native KGM degraded sharply in enzymatic degradation test and it had bigger swelling ratio and weight loss ratio than those hydrogels which composed of lower molecular weights KGM. Therefore, hydrogels composed of lower molecular weight might release drug more stable when they were used as drug carrier.

Abstract: A nonapeptide, which is sensitive to enzymatic digestion by collagenase, was modified by the covalent attachment of an acrylamido group at the terminal positions. The functionalized peptide was used as a crosslinking agent during polymerization of 2-hydroxyethyl methacrylate (HEMA). Reversible addition-fragmentation chain transfer (RAFT) method was used to obtain a polymer (PHEMA) with an average theoretical molecular weight of 4000 Da, containing enzymatically labile peptide crosslinks. The functionalized peptide was analyzed in detail by 1H and 13C nuclear magnetic resonance (NMR) spectrometry. The polymerization reaction was monitored by near infrared spectrometry, while the resulting polymer was analyzed by size exclusion chromatography and solid NMR spectrometry. The peptide-crosslinked PHEMA was subjected to an in-vitro degradation assay in the presence of collagenase. At the highest concentration of enzyme used in the study, a weight loss of 35% was recorded after 60 days of incubation in the collagenolytic medium. This suggests that crosslinking with enzymatically degradable peptides is a valid method for inducing biodegradability in polymers that otherwise are not degradable.