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 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.

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 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.

Glutaraldehyde clinically is the most commonly accepted crosslinking reagent for bioprosthetic valves preparation. Glutaraldehyde-treated tissue is stable against chemical and enzymatic degradation; however, its calcification and cytotoxicity are severe. Dye-mediated photooxidation is an alternative tissue preservation method that oxidizes the protein with visible light in the presence of a suitable photosensitizer. This article reviews chemical mechanism, research progress, clinical applications future development of these two methods.
Animals ; Bioprosthesis ; Calcinosis ; Cross-Linking Reagents ; Glutaral ; Heart Valve Prosthesis ; Heart Valve Prosthesis Implantation ; Humans ; Photochemistry

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.

The effect of parasitic ions on the results of ultraviolet A (UVA) cross-linking in iontophoresis was still not clear. In this work, the porcine sclera was cross-linked by riboflavin lactate Ringer's solution (group A) and riboflavin normal saline (group B)
Animals ; Collagen ; Cross-Linking Reagents ; Ions ; Iontophoresis ; Permeability ; Photosensitizing Agents/pharmacology* ; Riboflavin ; Sclera ; Swine ; Ultraviolet Rays

China is the country with high incidence of high myopia in the world. High myopia can cause severe vision impairment. So far, there is no effective treatment for high myopia in clinic. Scleral collagen cross-linking surgery has been proven to be effective in preventing animal eye axial elongation
Animals ; Collagen ; Cross-Linking Reagents ; Finite Element Analysis ; Photosensitizing Agents ; Riboflavin ; Sclera

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