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

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.

Chitosan ; Cross-Linking Reagents ; Delayed-Action Preparations ; Iridoids ; Microscopy, Electron, Scanning ; Microspheres ; Pravastatin ; chemistry

OBJECTIVETo investigate the biocompatibility and degradation rate of crosslinking sodium hyaluronate gel with different ratio of molecular weight, so as to choose the effective, safe and totally degraded hyaluronate gel for aesthetic injection.

METHODS(1) Compound colloid was formed by cross-linking the divinyl sulphone and sodium hyaluronate with different molecular weight (4 x 10(5), 8 x 10(5), 10 x 10(5), 12 x 10(5)). (2) Healthy level KM mice was randomly divided into two groups to receive hyaluronic acid gel or liquid injection. Each group was subdivided into three subgroup to receive hyaluronic acid with different molecular weight. The biocompatibility and degradation rate, of hyaluronate were observed at 7, 90, 180 days after injection. At the same time, different molecular weight of sodium hyaluronate gel is sealed or exposed respectively under the low temperature preservation to observe its natural degradation rate. (3) The most stable colloid was selected as aesthetic injector for volunteers to observe the aesthetic effect.

RESULTSThe sodium hyaluronate gel with molecular of 4 x 10(5) was completely degraded 90 days later. The sodium hyaluronate gel with molecular of 8 x 10(5) was completely degraded 180 days later. The sodium hyaluronate gel with molecular of 10 x 10(5) was degraded to 90.0% after 180 days. The sodium hyaluronate liquid can be degraded completely within 7 days. The colloid could be kept for at least 12 months when sealed under low temperature, but was totally degraded when exposed for I d. Sodium hyaluronate gel with molecular 10 x 10(5) was confirmed to be kept for at least 6 months in animal experiment and clinical trials.

CONCLUSIONSUnder the same condition of material ratio, the higher the molecular weight is, the lower the degradation rate is. But the liquidity of gel is not good for injection when molecular weight is too large. It suggests that Sodium hyaluronate gel with molecular 10 x 10(5) maybe the best choice in cosmetic injections.

Animals ; Cross-Linking Reagents ; administration & dosage ; chemistry ; Hyaluronic Acid ; administration & dosage ; chemistry ; Injections, Subcutaneous ; Mice ; Molecular Weight ; Random Allocation

The core-crosslinked polymeric micelles were used as a new drug delivery system, which can decrease the premature drug release in blood circulation, improve the stability of the micelles, and effectively transport the drug into the therapy sites. Then the drug bioavailability increased further, while the side effect reduced. Most drugs were physically entrapped or chemically covalent with the polymer in the internals of micelles. Based on the various constitutions and properties of polymeric micelles as well as the special characteristics of body microenvironment, the environment-responsive or active targeting core-crosslinked micelles were designed and prepared. As a result, the drug controlled release behavior was obtained. In the present paper, the research progress of all kinds of core-crosslinked micelles which were published in recent years is introduced. Moreover, the characteristic and application prospect of these micelles in drug delivery system are analyzed and summarized.
Animals ; Antineoplastic Agents ; administration & dosage ; chemistry ; therapeutic use ; Cross-Linking Reagents ; chemistry ; metabolism ; Drug Carriers ; chemistry ; metabolism ; Humans ; Micelles ; Molecular Structure ; Neoplasms ; drug therapy ; Particle Size ; Pharmaceutical Preparations ; administration & dosage ; Polyethylene Glycols ; chemistry ; metabolism ; Polymers ; chemistry ; metabolism

Collagen (Coll), as the basic material of matrix scaffolds for cell growth, has been widely used in the field of tissue engineering and regenerative medicine. In this study, collagen protein was modified by L-lysine (Lys), and cross-linked by genipin (GN) to prepare the L-lysine-modified collagen (Lys-Coll-GN) scaffolds. Microstructure, pore size, porosity, stability and biocompatibility of Lys-Coll-GN scaffolds were observed. The results showed that the bond between L-lysine and collagen protein molecule was formed by generating amide linkage, and mouse embryo fibroblasts proliferation was not inhibited in the Lys-Coll-GN scaffolds. In the multiple comparisons of Coll-scaf- folds, Coll-GN scaffolds and Lys-Coll-GN scaffolds, Coll-scaffolds was the worst in mechanical characteristics while the highest in biodegradation rate. Compared to Coll-GN scaffolds, Lys-Coll-GN scaffolds had more fiber structure, higher interval porosity (P<0. 01). Although the tensile stress of Lys-Coll-GN scaffolds reduced significantly, its e- longation length extended when the scaffolds was fractured (P<0. 01). The percentage of Lys-Coll-GN scaffolds residual weight was lower than that of Coll-GN scaffolds after all the scaffolds were treated by collagenase for 5 days (P<0. 01). This study suggested that Lys-Coll-GN scaffold had good biocompatibility, and it improved the mechanical property and degradation velocity for collagen-based scaffold. This study gave a new predominant type of tissue engineering scaffold for the regenerative medicine.
Animals ; Biocompatible Materials ; chemistry ; Cell Proliferation ; Collagen ; chemistry ; Cross-Linking Reagents ; Fibroblasts ; cytology ; Iridoids ; chemistry ; Lysine ; chemistry ; Mice ; Porosity ; Tissue Engineering ; Tissue Scaffolds

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.

Biocompatible Materials ; chemistry ; Cross-Linking Reagents ; Humans ; Tissue Engineering ; methods ; Tissue Scaffolds ; chemistry

The objective of this investigation was to study the characteristics and biocompatibility of collagen/polyvinyl alcohol (PVA) membrane crosslinked by UV-riboflavin. Membranes that were made into complex ones with different mass ratios of collagen to PVA (1:1 and 2:1) were synthesized, and crosslinked with UV-riboflavin. The surface characteristics were analyzed using the omnipotent materials instrument, IR, SEM, water absorption test, gas permeability test, and degradation test, respectively. The biocompatibility of membrane complex and rat bone marrow mesenchymal stem cells (BMSCs) was evaluated after 7 d and 14 d, respectively. The collagen/PVA complex membranes showed good homogeneity, mechanical property, degradation ratio, water absorption, gas permeability, etc. The biocompatibility of the collagen/PVA (2:1) complex membrane crosslinked with UV-Riboflavin was higher than that of without crosslinking and collagen/PVA (1:1) membrane. It could be well concluded that collagen/PVA complex membranes crosslinked with UV-riboflavin would have a potential application in biomedicine.
Animals ; Biocompatible Materials ; chemistry ; Collagen ; chemistry ; Cross-Linking Reagents ; chemistry ; Materials Testing ; Membranes, Artificial ; Mesenchymal Stromal Cells ; cytology ; drug effects ; Polyvinyl Alcohol ; chemistry ; Rats ; Riboflavin ; chemistry ; Tissue Engineering ; methods ; Ultraviolet Rays

In order to investigate the feasibility of the modified chitosan-gelatin crosslinked membrane (MC-Gel) and chitosan-gelatin crosslinked membrane (CS-Gel) to be a potential biomaterial for corneal regeneration, we evaluated their physicochemical properties and intraocular biocompatibility in this study. White light transmission and permeability of these membranes were detected. Results showed that white light transmission of both membranes was above 90% at 500 nm, which was similar to that of human cornea. The glucose, tryptophan and NaCl permeability of MC-Gel membrane and CS-Gel membrane was better than or similar to those of human cornea. The methylthiazol tetrazolium (MTT) assay was used to assess cell viability and proliferation. Also, interlamellar corneal transplantation was carried out to evaluate ophthalmic biocompatibility of MC-Gel membrane and CS-Gel membrane. Results indicated that MC-Gel membranes could support the proliferation of HCEC and displayed good intraocular biocompatibility when implanted into rabbits. No severe inflammatory reaction occurred after transplantation and the implanted MC-Gel membrane degraded completely 16 weeks post-operation. Due to its good physicochemical properties and biocompatibility, MC-Gel membrane could be a promising candidate material for corneal regeneration.
Animals ; Biocompatible Materials ; chemistry ; Cells, Cultured ; Chitosan ; chemistry ; Cornea ; cytology ; Corneal Injuries ; Cross-Linking Reagents ; Epithelium, Corneal ; cytology ; physiology ; surgery ; Gelatin ; chemistry ; Guided Tissue Regeneration ; methods ; Humans ; Membranes, Artificial ; Rabbits ; Regeneration ; Tissue Engineering ; methods ; Tissue Scaffolds

The aim of this study was to obtain the alginate gels which could have proper compressive strength and excellent permeability for cell proliferation and could have more promising potentials in the application of tissue engineering. Through the reaction of the carboxyl of the alginate and the amino of methacrylic acid, methylacrylic was generated into alginate long chain which could be enhanced by the polymerization of double bond under thermal reaction condition. And then alginate gel beads were prepared using the mixture of calcium chloride and barium chloride solution as cationic crosslinker, and the compressive modulus and permeability of the prepared alginate gel beads were investigated. When the ratio of barium ions to calcium ions was 5:5, the compression modulus was 189.7 kPa, and it showed the best permeability for trypsin with molecular weight of 24 kDa and entrapment effect for bovine serum albumin with molecular weight of 67 kDa. Compared to compositions of other ratios, the alginate gel beads made in 5:5 mixture indicated excellent compressive modulus and permeability. These results indicated that the alginate hydrogel beads with the ratio of barium ions to calcium ions being 5:5 have a potential application in tissue engineering as a support material and encapsulating materials in cell culture.
Alginates ; chemistry ; Barium Compounds ; chemistry ; Calcium Chloride ; chemistry ; Cations ; Cell Culture Techniques ; Cell Proliferation ; Chlorides ; chemistry ; Cross-Linking Reagents ; chemistry ; Gels ; chemistry ; Metals ; Polymethacrylic Acids ; chemistry ; Tissue Engineering