5-fluorouracil was combined with peanut agglutinin by a water-soluble carbodiimide to prepare the tumor target conjugate of 5-fluorouracil-peanut agglutinin and the ratio of drug to conjugate was determined by the modified trinitrobenzenesulfonic acid method (TNBS). The ratio of drug to conjugate was 76.33%. The result showed that 5-fluorouracil could link to the peanut agglutinin by EDC/NHS crosslinking with high drug ratio.
Antineoplastic Agents ; chemistry ; Cross-Linking Reagents ; chemistry ; Fluorouracil ; chemistry ; Peanut Agglutinin ; chemistry

OBJECTIVETo investigate the influence of cross-linking agents genipin and glutaraldehyde on the composite bio-sponge.

METHODSThe composite bio-sponge was prepared with the technology of lyophilization. The degree of cross linking was determined using absorptiometry of trinitrobenzenesulfonic acid; the cytotoxicity was tested by MTT assay; the degradation rate in vitro was valuated by lysozyme degradation.

RESULTS(1) The degree of cross linking of composite bio-sponge crosslinked using genipin and glutaraldehyde increased with the crosslinking time, and reached 26.43% and 54.63% respectively after crosslinking 3 d. (2) The water absorption rate of composite bio-sponge crosslinked using genipin was better than that of crosslinked using glutaraldehyde. (3) In the initial stage of cells incubation, all extracts of composite bio-sponges crosslinked using genipin and glutaraldehyde inhibited the growth of the cells, and the inhibition decreased with the incubation time; but the cytotoxicity of composite bio-sponge crosslinked using glutaraldehyde was higher than that of crosslinked using genipin. (4) After soaking in saline for 4 weeks, the degradation rate of composite bio-sponge crosslinked using genipin or glutaraldehyde was 32.1%, 28.4%, respectively; however, after soaking in saline containing lysozyme for 40 h, the degradation rate of composite bio-sponge was 36.7%, 31.2%, respectively.

CONCLUSIONCompared with the composite bio-sponge crosslinked using glutaraldehyde, the degree of cross linking and the cytotoxicity of the composite bio-sponge crosslinked using genipin decreased; however, the water absorption rate and the degradation rate increased.

OBJECTIVETo review the current crosslinking strategies for acelluar matrix scaffold, laying the foundation for subsequent experiment.

DATA SOURCESData were mainly obtained from recent papers published in PubMed or indexed by Web of Science, with keyword like crosslinking.

RESULTSVarious crosslinking strategies, including chemical, physical and biological methods, have been introduced to facilitate the performance of fresh acellular matrix. Chemical crosslinking reagents, involved in synthetic and naturally derived agents, need to be eliminated before implantation in case of their potential biotoxicity, although several crosslinking agents with less toxicity and specific characteristics have been developed. Physical crosslinking methods present to be safe, additive-free and relatively controllable for rapid surface functionalization with no consideration of remaining radioactivity. Biological crosslinking strategies have attracted great interest, and have been demonstrated to enhance collagen-based crosslinking since their preparations do not need toxic or potentially biologically contaminated substances and can be carried out under physiological conditions.

CONCLUSIONSKinds of crosslinking methods with its potential advantages have been developed to modify raw acelluar matrix, of which the performance are promising after being crosslinked by several crosslinking treatments. Further preclinical and clinical evaluations should be taken to vertify their safety and efficacy for the tissues and organs substitutes in tissue and regenerative medicine.

We studied the effect of calcium ion on particle size and pore structure of cross-linked enzyme aggregates (CLEAs) of glucose oxidase, with activity and stability of the enzyme as evaluation criteria. With calcium ion to prepare CLEA significantly decreased particle sizes of CLEAs whilst the pore structures of CLEAs gradually disappeared with the increase of calcium concentration. When glucose oxidase was precipitated at 0.1 mmol/L Ca²⁺, glucose oxidase in CLEA showed the definitive pore structure. Moreover, glucose oxidase activity in CLEA with Ca²⁺ was 1.69 times higher than that without Ca²⁺. Even at Ca²⁺ as high as 1.0 mmol/L, glucose oxidase activity in CLEA was 42% higher than that of CLEA without Ca²⁺. Furthermore, CLEA prepared with 0.1 mmol/L Ca²⁺ not only exhibited higher substrate conversion and operational stability, but also increased the maximum reaction speed. Therefore, calcium ion improved the performance of glucose oxidase in CLEAs.
Calcium ; chemistry ; Cross-Linking Reagents ; Enzyme Stability ; Enzymes, Immobilized ; Glucose Oxidase ; chemistry ; Oxidation-Reduction ; Particle Size

OBJECTIVETo prepare pravastatin sodium-loaded chitosan microspheres to allow sustained drug release.

METHODSThe drug-loaded chitosan microspheres were prepared by using genipin as the cross-linker. The influences of molecular weight of chitosan, volume ratio of oil and water, reaction temperature, and stirring speed on the formation of chitosan microspheres were investigated. The morphology of the microspheres was observed using scanning electron microscopy. The encapsulation efficiency, swelling ratio under different pH conditions, and in vitro drug release were measured.

RESULTSThe in vitro release of pravastatin sodium could last for at least 31 days. The drug release rate varied with the reaction condition. The drug entrapment efficiency of the microsphere was 54.7%. The optimal processing conditions were as follows: chitosan viscosity of 200-400 mPa·s, oil-water proportion of 10:1, stirring speed of 850 r/min, and reaction temperature at 40 degrees celsius;.

CONCLUSIONThe pravastatin sodium-loaded microspheres show good sustained drug release property, and the drug release rate can be modified by controlling the cross-linking time.

In this study, we prepared various matrices of hydrogel patches and studied their cross-linking mechanism by observing their rheological properties, which could provide theoretical basis and deep technical support for further industrial development of hydrogel patch. Rheology method was used to do the amplitude scanning and single-frequency scanning for various hydrogel matrix, under the condition of oscillation mode of the rheometer. Then the linear viscoelastic region, composite modulus value, as well as changes in slope with time of the composite modulus and phase angle of various hydrogel matrix were analyzed in detail. The results showed that the stability of matrix was mainly determined by hydrogel frame; only in acidic environment, the cross-linking reaction between cross-linker and hydrogel frame can occur; elasticity of matrix can be decreased by organic acid and the effect level was related to the ratio of the number of carboxyl and hydroxyl (-COO(-)/-OH) in adjusters: if the ratio was not equal, the higher -COO(-)/-OH in adjusters would be the less elasticity of matrix decreased; the cross-linking speed of matrix was determined by adjuster, the cross-linking speed of matrix contain different adjusters was ranged in following order: matrix containing tartaric acid > matrix containing lactic acid > matrix containing malic acid > matrix containing citric acid; the cross-linking speed of matrix was not uniform in the whole cross-linking process.
Citric Acid ; chemistry ; Cross-Linking Reagents ; chemistry ; Hydrogels ; chemistry ; Lactic Acid ; chemistry ; Malates ; chemistry ; Rheology ; Tartrates ; chemistry ; Viscosity

In this study, using ethylene carbonate and ethanolamine, we synthesized a novel diol chain-extender, bis-hydroxylethyl carbomate (EC-AE), which contains carbomate structure. The polyurethanes, PUA25 and PUB25, with different extenders, EC-AE and BDO, were synthesized by one-step polymerization, respectively. Their structures were characterized by using FT-IR and DSC. The results indicated that the microphase separation degree of PUA25 was less than that of PUB25, in other words, the amount of hydrogen bonding between hard segments and soft segments in PUA25 was superior to that in PUB25. And the formation of physically crosslinked hydrogels prepared by PUA25 and PUB25 were studied in detail. It was found that only PUA25 can form hydrogel in situ from solution state by cooling. And this kind of hydrogels showed the transition cycle of "gel-sol-gel" under "cooling-heating-cooling" thermal cycles, respectively. The results suggested that the physically crosslinked polyurethane hydrogels were easily possessed in high degree of phase mixing.
Biocompatible Materials ; Cross-Linking Reagents ; chemistry ; Hydrogel, Polyethylene Glycol Dimethacrylate ; chemical synthesis ; chemistry ; Polyurethanes ; chemical synthesis ; chemistry

A novel crosslinkable coating for biomedical device was prepared by copolymerization of the constituent monomers via a free radical method. 1H-NMR and IR results indicated it had desirable structure. Surface characterization revealed that surface reorganization occurred in aqueous environment and a polyethylene oxied (PEO) enrichment surface was developed on coated surface. The in-vitro platelet-adhesion test and the plasma recalcification time(PRT) determination showed that the coated surface could resist the blood coagulation effectively.
Blood Coagulation ; Coated Materials, Biocompatible ; chemistry ; Cross-Linking Reagents ; chemistry ; Materials Testing ; Platelet Adhesiveness ; Polyethylene Glycols ; chemistry ; Surface Properties

Lipase (EC3.1.1.3) from Candida sp. 99-125 was immobilized on chitosan by chemical covalence. Lipase was first immobilized to chitosan beads by activating its hydroxyl groups with carbodiimide followed by cross-linking more lipase to the amino groups with glutaraldehyde. In this article, different factors that influenced the immobilization were investigated, and the optimum conditions were ascertained. Comparative studies of organic solvent and thermal stability between free lipase and immobilized lipase were conducted. Immobilization enhanced the lipase stability against changes of temperature and organic solvent. Immobilization lipase can be reused in the synthesis system of palmitate hexadecyl. Operational stability tests indicated that the immobilized lipase occurs after 16 consecutive batches, the conversion rate remained 85%. Such results revealed good potential for recycling under esterification system.
Candida ; enzymology ; Carbodiimides ; chemistry ; Chitosan ; chemistry ; Cross-Linking Reagents ; Enzyme Stability ; Enzymes, Immobilized ; Lipase ; metabolism ; Palmitates ; chemistry

OBJECTIVE: To compare the effects of three different crosslinkers on the biocompatibility, physical and chemical properties of decellularized small intestinal submucosa (SIS) porous scaffolds. METHODS: The SIS porous scaffolds were prepared by freeze-drying method and randomly divided into three groups, then crosslinked by glutaraldehyde (GA), 1-ethyl-3-(3-dimethylaminopropyl) carbodi-imide (EDC) and procyanidine (PA) respectively. To evaluate the physicochemical property of each sample in different groups, the following experiments were conducted. Macroscopic morphologies were observed and recorded. Microscopic morphologies of the scaffolds were observed using field emission scanning electron microscope (FESEM) and representative images were selected. Computer software (ImageJ) was used to calculate the pore size and porosity. The degree of crosslinking was determined by ninhydrin experiment. Collagenase degradation experiment was performed to assess the resistance of SIS scaffolds to enzyme degradation. To evaluate the mechanical properties, universal mechanical testing machine was used to determine the stress-strain curve and compression strength was calculated. Human bone marrow mesenchymal cells (hBMSCs) were cultured on the scaffolds after which cytotoxicity and cell proliferation were assessed. RESULTS: All the scaffolds remained intact after different crosslinking treatments. The FESEM images showed uniformed interconnected micro structures of scaffolds in different groups. The pore size of EDC group[(161.90±13.44) μm] was significantly higher than GA group [(149.50±14.65) μm] and PA group[(140.10±12.06) μm] (P < 0.05). The porosity of PA group (79.62%±1.14%) was significantly lower than EDC group (85.11%±1.71%) and GA group (84.83%±1.89%) (P < 0.05). PA group showed the highest degree of crosslinking whereas the lowest swelling ratio. There was a significant difference in the swelling ratio of the three groups (P < 0.05). Regarding to the collagenase degradation experiment, the scaffolds in PA group showed a significantly lower weight loss rate than the other groups after 7 days degradation. The weight loss rates of GA group were significantly higher than those of the other groups on day 15, whereas the PA group had the lowest rate after 10 days and 15 days degradation. PA group showed better mechanical properties than the other two groups. More living cells could be seen in PA and EDC groups after live/dead cell staining. Additionally, the proliferation rate of hBMCSs was faster in PA and EDC groups than in GA group. CONCLUSION The scaffolds gained satisfying degree of crosslinking after three different crosslinking treatments. The samples after PA and EDC treatment had better physicochemical properties and biocompatibility compared with GA treatment. Crosslinking can be used as a promising and applicable method in the modification of SIS scaffolds.
Biocompatible Materials/chemistry* ; Cross-Linking Reagents/chemistry* ; Humans ; Porosity ; Tissue Engineering/methods* ; Tissue Scaffolds/chemistry* ; Weight Loss