Connections between cohesion and properties that related to safety and effectiveness of the hyaluronic acid dermal fillers: A comparative study of the cohesive and non-cohesive gels.

BACKGROUND: Although the importance of the cohesion of a hyaluronic acid (HA) filler has been recognized, the relationship between the cohesion and the other performance that related to safety and effectiveness, as well as the underlying mechanism is barely studied. Much efforts need to be made on this subject to provide guidance for clinical practice. MATERIALS AND METHODS: Two types of the HA fillers (cohesive and particulate gels) were selected for the comparison of the cohesion and the other key physicochemical properties. RESULTS: Hyalumatrix, with significantly higher cohesion, was homogeneously smooth and showed a linearly oriented morphology, whereas Matrifill and Restylane were particulate and showed obvious boundaries between particles. The high cohesion of Hyalumatrix is beneficial to the properties that related to safety and effectiveness, including recovery under shear stress, injectability, tissue integration and in vitro resistance to enzymolysis. The underlying reason was that the strong internal interactions of the cohesive gel protect the network structure from collapse and keep the gel as an intact whole when the gel was subjected to the stress. The homogeneously smooth morphology further improved the tissue compliance and injectability. The G' of Hyalumatrix is in the middle level of the commercially available HA fillers. CONCLUSION: Hyalumatrix is a rare HA filler product to possess good cohesion and intermediate G' simultaneously. More clinical practice is needed to verify the connection between the cohesion of Hyalumatrix and the clinical performance.

Effect of a New Hyaluronic Acid Hydrogel Dermal Filler Cross-Linked With Lysine Amino Acid for Skin Augmentation and Rejuvenation.

BACKGROUND: Hyaluronic acid (HA) fillers are the most popular filler agents for skin rejuvenation. Although 1,4-butanediol diglycidyl ether is regarded as a relatively safe cross-linker, it still exhibits certain cytotoxicity. OBJECTIVES: We presented here an amino acid-cross-linked HA (ACHA) which was obtained by an amidation reaction with lysine and HA. This study aimed to investigate ACHA's efficacy and safety for skin augmentation and rejuvenation. METHODS: Rheology, compressive tests, and swelling experiments were conducted to investigate ACHA's mechanical and viscoelastic properties. The effects of ACHA on the human keratinocytes (HaCaT) cells and the human dermal fibroblast (HDF) were investigated by Transwell and wound healing assays. Its impacts on the epithelial thickness and collagen synthesis were further examined in a mouse experimental model. We recruited 50 patients with moderate to severe nasolabial folds (NLFs). The patients were randomly allocated to receive ACHA or Restylane injections. The resulting retention rates of HA and the Wrinkle Severity Rating Scale and Global Aesthetic Improvement Scale outcomes were evaluated and compared. RESULTS: ACHA exhibited good viscoelasticity. It not only promoted migration and proliferation of HaCat and HDF and secretion of various growth factors but also increased skin thickness and promoted the generation of collagen. Patients who received ACHA had more residual volume 12 months after treatment. ACHA exhibited a promising augmentation effect in NLF correction with few adverse reactions. CONCLUSIONS: ACHA has shown promise as a biomaterial with excellent biocompatibility and viscoelastic characteristics in both research and the clinic.See the abstract translated into Hindi, Portuguese, Korean, German, Italian, Arabic, Chinese, and Taiwanese online here: https://doi.org/10.1093/asj/sjad169.

A paintable ophthalmic adhesive with customizable properties based on symmetrical/asymmetrical cross-linking.

In situ and efficient incision sealing for ophthalmic surgery remains unresolved. Current commercially available gel adhesives often suffer from unsuitable gelation time, difficulty in micro-delivery, and mismatched degradation period, leading to difficulties for application in ocular tissue areas. Herein, a novel hydrogel adhesive was developed based on the simultaneous crosslinking of poly(lysine) (PLL) and lysine (Lys) with an end-modified active ester multi-arm polyethylene glycol (PEG) via the amidation reaction, where the residual terminal active ester of PEG can also bond to amino groups on tissue to provide strong adhesion. Due to the different molecular structures around their amino groups, PLL and Lys can crosslink with 4-arm-PEG-NHS (active ester) respectively, to form symmetrical and asymmetrical crosslinking networks, which exhibit various mechanical properties. Therefore, just by adjusting PLL/Lys ratios, the PEG-PLL-Lys hydrogel can easily possess a suitable gelation time, appropriate mechanical properties and matched degradation rate. As a result, a paintable, readily accessible and biocompatible ophthalmic tissue adhesive (sealant) is prepared for sealing ocular tissue incision. Considering the simple strategy and outstanding performance, the PEG-PLL-Lys hydrogel is promising for clinical transformation.

A nano chitosan membrane barrier prepared via Nanospider technology with non-toxic solvent for peritoneal adhesions' prevention.

Peritoneal adhesion is one of the most common postsurgical complications and can cause bowel obstruction, pelvic pain, and infertility. Setting up a physical barrier directly between the injured site and surrounding tissues is an effective solution for preventing this adverse situation. This study investigated a chitosan electrospun membrane (CSEM) as a potent anti-adhesion barrier, which was prepared by a needleless technology called Nanospider. Scanning electron microscopy revealed that CSEM is a laminated nanofiber with good mechanical properties. The fiber is uniform with the diameter distributing in the range of 100-120 nm. The tensile strength can reach 27.45 ± 6.30 MPa with a maximum elongation at break of 18.50 ± 1.44%, which makes it stick easily to damaged parts but not to be easily damaged by tissue friction. The growth of S. aureus on CSEM was 59.18% lower than the control at 10 h, which indicates its better antibacterial property. In addition, CSEM has good coagulant and biocompatibility characteristics. It can perform hemostatic function within 10 min and the L929 mouse fibroblast viability on it was 92.18% ± 1.08% on the seventh day. In vivo experiments indicated that CSEM significantly prevented peritoneal adhesions within four weeks after surgery with wound surface coverage. These results indicate that CSEM is a promising anti-adhesion barrier material.

An in situ mechanical adjustable double crosslinking hyaluronic acid/poly-lysine hydrogel matrix: Fabrication, characterization and cell morphology.

Cell fate and morphologies are influenced by the mechanical property of matrix. However, the relevant works about the dynamic adjustable of matrix mechanical property is rare and most of them need extra stimulation, such as the controllable of the degradation. In this study, double crosslinking (DC) hydrogels are fabricated by sequential covalent crosslinking and electrostatic interactions between hyaluronic acid and poly-lysine. Without any extra stimulation or treatment, the compressive stress of DC-hydrogels increases from 22.4 ± 9.4 kPa to 320.1 ± 6.6 kPa with the elongation of incubation time in DMEM solution. The change of compressive stress of matrix induced the morphology of L929 fibroblast cells adjusted from the distributed round shape to spheroid cell clusters and finally to spread shape. RNA sequence analysis also demonstrated that the differentially gene expression and GO enrichment between the cells seeded on the DC-hydrogel with different incubation time. In addition, by increasing the electrostatic interactions ratio of the hydrogel, the biodegradation, compressive stress and energy dissipation of the DC-hydrogels were also significantly improved. Therefore, our study provides new and critical insights into the design strategy to achieve DC-hydrogels which can in situ alter cells morphology and open up a new avenue for the application of disease therapy.

[A green route for the fabrication of thermo-sensitive chitosan nerve conduits and their property evaluation].

OBJECTIVE: To explore a green route for the fabrication of thermo-sensitive chitosan nerve conduits, improve the mechanical properties and decrease the degradation rate of the chitosan nerve conduits. METHODS: Taking advantage of the ionic specific effect of the thermo-sensitive chitosan, the strengthened chitosan nerve conduits were obtained by immersing the gel-casted conduits in salt solution for ion-induced phase transition, and rinsing, lyophilization, and 60Co sterilization afterwards. The nerve conduits after immersing in NaCl solutions for 0, 4, 12, 24, 36, 48, and 72 hours were obtained and characterized the general observation, diameters and mechanical properties. According to the above results, the optimal sample was chosen and characterized the microstructure, degradation properties, and cytocompatibility. The left sciatic nerve defect 15 mm in length was made in 20 male Sprague Dawley rats. The autologous nerves (control group, n=10) and the nerve conduits (experimental group, n=10) were used to repair the defects. At 8 weeks after operation, the compound muscle action potential (CMAP) was measured. The regenerated nerves were investigated by gross observation and toluidine blue staining. The gastrocnemius muscle was observed by HE staining. RESULTS: With the increased ionic phase transition time, the color of the conduit was gradually deepened and the diameter was gradually decreased, which showed no difference during 12 hours. The tensile strength of the nerve conduit was increased gradually. The ultimate tensile strength showed significant difference between the 48 hours and 12, 24, and 36 hours groups ( P<0.05), and no significant difference between the 48 hours and 72 hours groups ( P>0.05). As a result, the nerve conduit after ion-induced phase transition for 48 hours was chosen for further study. The scanning electron microscope (SEM) images showed that the nerve conduit had a uniform porous structure. The degradation rate of the the nerve conduit after ion-induced phase transition for 48 hours was significantly decreased as compared with that of the conduit without ion-induced phase transition. The nerve conduit could support the attachment and proliferation of rat Schwann cells on the inner surface. The animal experiments showed that at 8 weeks after operation, the CMAPs of the experimental and control groups were (3.5±0.9) and (4.3±1.1) m/V, respectively, which showed no significant difference between the two groups ( P<0.05), and were significantly lower than that of the contralateral site ï¼»(45.6±5.6 m/V), P>0.05ï¼½. The nerve conduit of the experimental group could repair the nerve defect. There was no significant difference between the experimental and control groups in terms of the histomorphology of the regenerated nerve fibers and the gastrocnemius muscle. CONCLUSION: The green route for the fabrication of thermo-sensitive chitosan nerve conduits is free of any toxic reagents, and has simple steps, which is beneficial to the industrial transformation of the chitosan nerve conduit products. The prepared chitosan nerve conduit can be applied to rat peripheral nerve defect repair and nerve tissue engineering.

[Experimental study on crosslinked-chitosan in treatment of knee osteoarthritis in rabbits].

Objective: To study the effect of intraarticular injection of crosslinked-chitosan in the treatment of knee osteoarthritis in rabbits. Methods: Thirty-two New Zealand white rabbits were randomly divided into 4 groups (groups A, B, C, and D; 8 rabbits in each group). The knee osteoarthritis models were prepared by anterior cruciate ligament transection in the left hind in groups A, B, and C. At 4 weeks after operation, the rabbits were received intraarticular injection of 0.6 mL crosslinked-chitosan in group A, 0.3 mL chitosan (once per 2 weeks, for twice) in group B, and 0.3 mL saline (once per 2 weeks, for twice) in group C. The rabbits in group D were treated with sham operation in the left hind, and received intraarticular injection of 0.3 mL saline (once per 2 weeks, for twice). At 8 weeks, the macroscopic observation, histological examination (HE staining, Safranin-fast green double staining, and Mankin score), scanning electron microscopy (SEM) observation, and immunohistochemical staining of collagen type Ⅱ were performed. Results: Macroscopic and SEM observations showed that the cartilage in group D was basically the same as normal and better than that in groups A and B, and the abrasion of cartilage in group C was the most serious. The histological observation results in groups A and B were slightly similar and better than those in group C, but not up to the structure of group D. The macroscopic score and Mankin score of groups B and C were significantly higher than those of group D ( P<0.05), and there was no significant difference between group A and group B ( P>0.05). Immunohistochemical staining results showed that the collagen type Ⅱ positive percentage of chondrocytes was significantly higher in group D than that in groups B and C, and no significant difference was found between group A and group B ( P>0.05). Conclusion: The crosslinked-chitosan can significantly improve the osteoarthritis of the rabbit knee, delay the pathological changes of osteoarthritis, and decrease the frequency of injection.

Treatment of dry eye by intracanalicular injection of a thermosensitive chitosan-based hydrogel: evaluation of biosafety and availability.

Chitosan has been increasingly considered for the design of implant materials in the field of translational medicine. However, implant properties addressing the complexity of the desired tissue still need to be developed. The focus of this study lies in the evaluation of a thermosensitive chitosan-based hydrogel for intracanalicular injection. Hydroxybutyl chitosan (HBC) solution was prepared, and its cytocompatibility was investigated by the CCK-8 assay using primary human corneal epithelial cells (HCEpiCs). Minimal cytotoxicity was seen in cultures with the HBC-extracting solution at a concentration of 0.2 g ml-1 for up to 72 h incubation. The biocompatibility and effectiveness, based on both a rabbit model and a human pilot study, were evaluated anatomically and functionally. The flow flux significantly decreased after HBC injection, with 76.9% of the flow flux occurring 10 min after HBC injection. Tear secretion significantly improved in the rabbit model. The density of PAS-positive cells gradually increased in the animal model. Various clinical indicators, which include the ocular surface disease index (OSDI) and tear break up time, have been improved greatly. Thermosensitivity promotes greater suitability for HBC intracanalicular injection to obstruct the lacrimal drainage system at body temperature. These results demonstrate that the thermosensitive chitosan-based hydrogel is suitable as a liquid plug for tear flow blockage and thus represents a promising candidate for translational medicine.

Chitosan inhibits inflammation and adipogenesis of orbital fibroblasts in Graves ophthalmopathy.

Purpose: The aim of this study was to investigate the roles of chitosan in inflammation and adipogenesis of primary cultured orbital fibroblasts in Graves ophthalmopathy (GO). Methods: Cell viability, apoptosis, and cell cycle were determined with the Cell Counting Kit-8 (CCK-8), the Annexin V-FITC/PI kit, and flow cytometry, respectively. Inflammation of orbital fibroblasts was stimulated by interleukin-1 beta (IL-1ß). The levels of IL-6 and prostaglandin E-2 (PGE-2) were measured using an enzyme-linked immunosorbent assay (ELISA). The expression of cyclooxygenase-2 (COX-2) was measured with real-time PCR and western blot assay. Phosphorylation of c-Jun N-terminal kinase (JNK) was evaluated with western blot assay. An inhibitor of JNK was used to investigate the signal transduction pathway of cytokine production. Orbital fibroblasts differentiated to adipose cells in differentiation medium. Adipose cells were dyed with Oil Red O. FABP4, adiponectin, C/EBPα, PPAR-γ, and phosphorylation of AKT were evaluated with western blot assay. Results: The results showed that IL-1ß statistically significantly increased the expression of IL-6, PGE-2, and COX-2 in orbital fibroblasts. Phosphorylation of JNK was promoted by IL-1ß. IL-6 and PGE-2 were modulated by the JNK signaling pathway as determined with the inhibition experiments. Chitosan downregulated expression of IL-1ß-stimulated IL-6, COX-2, and PGE-2 and downregulated phosphorylation of JNK. Chitosan inhibited the production of adipose cells dyed by Oil Red O. Chitosan statistically significantly decreased the protein levels of FABP4, adiponectin, C/EBPα, and PPAR-γ with downregulation of AKT phosphorylation during adipocyte differentiation. Conclusions: Chitosan statistically significantly inhibits inflammation and adipogenesis, as well as related signaling pathways, of orbital fibroblasts in GO. This indicates a possible therapeutic effect of chitosan on Graves ophthalmopathy.

Fabrication of Multiple-Layered Hydrogel Scaffolds with Elaborate Structure and Good Mechanical Properties via 3D Printing and Ionic Reinforcement.

A major challenge in three-dimensional (3D) printing of hydrogels is the fabrication of stable constructs with high precision and good mechanical properties and biocompatibility. Existing methods typically feature complicated reinforcement steps or use potentially toxic components, such as photocuring polymers and crosslinking reagents. In this study, we used a thermally sensitive hydrogel, hydroxybutyl chitosan (HBC), for 3D-printing applications. For the first time, we demonstrated that this modified polysaccharide is affected by the specific ion effect. As the salt concentration was increased and stronger kosmotropic anions were used, the lower critical solution temperature of the HBC decreased and the storage modulus was improved, indicating a more hydrophobic structure and stronger molecular chain interactions. On the basis of the thermosensitivity and the ion effects of HBC, a 25-layered hydrogel scaffold with strong mechanical properties and an elaborate structure was prepared via a 3D-printing method and one-step ionic post-treatment. In particular, the scaffold treated with 10% NaCl solution exhibited a tunable elastic modulus of 73.2 kPa to 40 MPa and excellent elastic recovery, as well as biodegradability and cytocompatibility, suggesting the potential for its applications to cartilage tissue repair. By simply controlling the temperature and salt concentrations, this novel approach provides a convenient and green route to improving the structural accuracy and regulating the properties of 3D-printed hydrogel constructs.

Tissue-engineered conduit promotes sciatic nerve regeneration following radiation-induced injury as monitored by magnetic resonance imaging.

PURPOSE: To observe the longitudinal changes in peripheral nerve repaired with chitosan conduits in a rat model of radiation-induced neuropathy. MATERIALS AND METHODS: Four months after 40 Gy radiation to the right lower limbs, forty-two rats were divided randomly into three groups. Chitosan conduits were implanted with (group A, n=12) or without (group B, n=12) mesenchymal stem cells (MSCs), and untreated controls (group C, n=12). Following sciatic nerve MR imaging (including T2WI and Gd-DTPA enhanced T1WI), functional evaluation and electrophysiological exam were performed two-monthly, final histological assessments were done at the end of one year. The differences among the experimental and control groups were statistically analysed with Fisher's PLSD or t-test. RESULTS: The compound muscle action potentials (CMAPs) and sciatic function index (SFI) had declined since 4 months after radiation injury. The focal nerve enlargement and hyperintensity, the perineurium and connecting muscle enhancement were demonstrated by MR neurography images. After chitosan tube implantation, the normalized signal intensities (SIs) in group A were declined more rapidly than SIs in other groups. The histological assessments indicated that group A had better remyelination, combined with higher CMAPs amplitude and SFI score than other groups. CONCLUSION: A single fraction dose of 40 Gy can be used to establish a rat model of sciatic nerve injury. Longitudinal electrophysiological examination and MR neurography are useful to evaluate the post-irradiation sciatic neuropathy. The rats with tissue-engineered conduits implantation showed some improvement of lower limb function, accompanied by a normalization of (T1W/T2W) MR signal.

[Experimental study on hemostasis of thermosensitive chitosan hemostatic film].

OBJECTIVE: To investigate the hemostasis of thermosensitive chitosan hemostatic film. METHODS: Fifty adult Sprague Dawley rats, male or female and weighing 190-210 g, were made the models of liver injury. The models were randomly divided into 5 groups (n=10) depending on different hemostatic materials. The incision of the liver was covered with the hemostatic materials of 2.0 cm x 1.0 cm x 0.5 cm in size: thermosensitive chitosan hemostatic film (group A), chitosan hemostatic film (group B), cellulose hemostatic cotton (group C), gelatin sponge (group D), and no treatment (group E), respectively. The bleeding time and bleeding amount were recorded. After 4 weeks, the incisions of the liver were observed with HE staining. RESULTS: Gross observation showed better hemostatic effect and faster hemostatic time in groups A, B, and C; group D had weaker hemostatic effect and slower hemostatic time; group E had no hemostatic effect. The bleeding time and bleeding amount of groups A, B, C, and D were significantly lower than those of group E (P < 0.05). The bleeding time and bleeding amount of groups A, B, and C were significantly lower than those of group D (P < 0.05), but no significant difference was found among groups A, B, and C (P > 0.05). The liver cells of group A had milder edema and ballooning degeneration than other 4 groups through histological observation. CONCLUSION: The thermosensitive chitosan hemostatic film has good hemostasis effect on the liver incision of rats.

[An experimental study on effect of chitosan/polyvinyl alcohol nerve conduits on peripheral nerve regeneration in macaques].

OBJECTIVE: To investigate the effects of chitosan/polyvinyl alcohol (PVA) nerve conduits for repairing radial nerve defect in Macaques. METHODS: Twelve adult Macaques weighing 3.26-5.35 kg were made the models of radial nerve defect (2 cm in length) and were randomly divided into 3 groups according to nerve grafting, with 4 Macaques in each group. Chitosan/PVA nerve conduit, non-graft, and autografts were implanted in the defects in groups A, B, and C, respectively. And the right radial nerves were used as normal control. At 8 months postoperatively, the general observation, electrophysiological methods, and histological examination were performed. RESULTS: At 8 months postoperatively, the regenerated nerve bridged the radial nerve defect in group A, but no obvious adhesion was observed between the tube and the peripheral tissue. The regenerated nerve had not bridged the sciatic nerve defect in group B. The adhesions between the implanted nerve and the peripheral tissue were significant in group C. Compound muscle action potentials (CMAP) were detected in group A and group C, and no CMAP in group B. Peak amplitude showed a significantly higher value in normal control than in groups A and C (P < 0.05), but there was no significant difference between groups A and C (P > 0.05). Nerve conduction velocity and latency were better in normal control than in groups A and C, and in group C than in group A, all showing significant differences (P < 0.05). The density of myelinated fibers in groups A and C was significantly lower than that in normal control (P < 0.05), but there was no significant difference between groups A and C (P > 0.05). The diameter and the myelin sheath thickness of the myelinated fibers in normal control were significantly higher than those in groups A and C, and in group C than in group A, all showing significant differences (P < 0.05). CONCLUSION: The chitosan/PVA nerve conduits can promote the peripheral nerve regeneration, and may promise alternative to nerve autograft for repairing peripheral nerve defects.

[Experimental study on hemostasis of a new chitosan hemostatic powder].

OBJECTIVE: To study hemostasis of a new chitosan hemostatic powder. METHODS: Twenty-four adult SD rats were made the models of liver injury, male or female, and weighing 210-240 g. They were divided into three groups randomly (n = 8) depending on different hemostatic powders. The incision of the liver was treated with 300 mg Yunnan baiyao (group A1), chitosan hemostatic powder of pH 6.5 (group B1) and pH 7.5 (group C1), respectively. The bleeding time and bleeding amount were recorded. In vitro, with the modified Ree-White method, 2 mL artery blood from New Zealand white rabbit was added into the 0.2 mL solution of Yunnan baiyao, chitosan hemostatic powder of pH 6.5 and pH 7.5 (concentration of 0.2 mg/mL), respectively. The blood coagulation time was recorded. The chitosan blood clots of group B2 and group C2 were observed with scanning electron microscopy (SEM). RESULTS: The bleeding time of group A1, group B1 and group C1 was (292 +/- 31), (261 +/- 23), and (224 +/- 28) s, respectively, the bleeding amount was (1.63 +/- 0.21), (1.47 +/- 0.18), and (1.18 +/- 0.17) g, respectively, showing statistically significant differences between groups B1, C1, and group A1 (P < 0.05), between group C1 and group B1 (P < 0.05). The blood clotting time of group A2, group B2, and group C2 was (653 +/- 41), (255 +/- 20), and (202 +/- 11) s, respectively, showing statistically significant differences between groups B2, C2, and group A2 (P < 0.05), between group C2 and group B2 (P < 0.05). The SEM showed that the blood cells of group B2 and group C2 gathered around the chitosan. CONCLUSION: Chitosan hemostatic powder of pH 7.5 has good hemostasis.

A thermosensitive chitosan-based hydrogel barrier for post-operative adhesions' prevention.

Post-operative peritoneal adhesions are common and serious complications for surgeons. They can cause pelvic pain, infertility, and potentially lethal bowel obstruction. We synthesized injectable hydrogels that formed by chemical modification through grafted hydrobutyl groups to chitosan chains. Gelation of hydroxybutyl chitosan (HBC) occurs in less than 60 s. Once formed, it can also be recovered completely. The residue time of hydrogels can extend to 4 weeks in Kunming mice. HBC hydrogels showed mild cytotoxicity to mice fibroblast cell (L929) and human vascular endothelial cell (ECV-304) in vitro and were biocompatible in the murine muscles, causing no adhesions for 4 weeks. HBC gels can form a durable barrier between defected cecum and abdominal wall. In a mice sidewall defect-bowel abrasion model, HBC gels showed significant efficacy in reducing adhesion formation.

[Experimental study of the effect of chitosan/alginate dressings on wound immersed in seawater].

OBJECTIVE: To observe the effect of chitosan/alginate (CTS/ALG) dressings on wound immersed in seawater. METHODS: Twenty-five healthy SD rats weighing 250-300 g were used to establish skin wound model through cutting 1.8 cm circle-shaped wound along spine bilaterally. The left side served as experimental group, and the right side as control group. The wounds were immersed in the prepared artificial seawater for 1 hour, then the experimental group was treated with CTS/ALG dressings, while the control group was treated with sterile gauze. Gross observation was performed and wound healing time was recorded. At 3, 5, 7, 10 and 12 days after operation, 2 cm x 2 cm skin tissues including the wounds were removed and underwent HE staining and immunohistochemistry staining using Envision method. Histological change of wound and expression of EGF receptor (EGFR) and bFGF were observed. RESULTS: In the experimental group, wound inflammatory response was slight and incrustation shrinked faster, while the incrustation in the control group shrinked slowly. The wound healing time of the experimental group and the control group was (11.68 +/- 0.57) and (12.51 +/- 0.54) days, respectively, suggesting there was a significant difference between two groups (P < 0.05). In the experimental group, granulation tissue proliferation, cell infiltration, collagen tissue proliferation, wound shrinkage and epithelization appeared at 3 days after operation; regularly lined collagen tissue, complete epithelization and occurrence of skin appendages were observed at 10 days after operation; complete wound healing was noted at 12 days after operation; while in the control group, at the corresponding time point, late cell infiltration and epithelization were observed and granulation tissue with ulcer was noted. Immunohistochemistry observation: high expression of bFGF in vascular endothelial cells and interstitial fibroblasts and high expression of EGFR in vascular endothelial cells were observed in the experimental group at 3 and 5 days after operation, and their expressions were low at 7, 10 and 12 days after operation; while in the control group, there were no or low expression of bFGF and EGFR at the same time point. CONCLUSION: CTS/ALG dressings can promote the healing of wound immersed in seawater, but its mechanism needs further study.

[Prevention effect of hydroxybutyl chitosan on peritoneal adhesion in rats].

OBJECTIVE: To explore the effect of hydroxybutyl chitosan on the prevention of postoperative peritoneal adhesion in rats. METHODS: Ninety SD rats (half males and half females) weighing 250-280 g underwent laparotomy with subsequent cecal wall abrasion and peritoneal adhesion. Rats were randomized into 3 groups (n = 30 per group): group A, injection of 2 mL hydroxybutyl chitosan solution (2%); group B, injection of 2 mL sodium hyaluronate solution (2%); group C, the abdomen of rat was exposed for 30 seconds and served as control group. The general condition of the rats was observed after operation. The rats were killed 2 and 4 weeks after operation, 15 rats per group at a time, to undergo gross and histology observation. The degree of adhesion was evaluated by double-blind method. The microstructure of injured electroscope cecal wall in groups A and C was observed with transmission electroscope 4 weeks after operation. RESULTS: All rats survived till the end of experiment. At 2 weeks after operation, the adhesion and the hyperplasia of fibrous connective tissue and collagen in groups A and B were slight while the adhesion in group C was serious with severe hyperplasia of fibrous connective tissue. According to the measurement classification by Nair histological grading, the difference between groups A and B and group C was significant (P < 0.05), while no significant difference was evident between group A and group B (P > 0.05). At 4 weeks after operation, the adhesion in group A was mild, and the hyperplasia of fibrous connective tissue and collagen were slight; the adhesion and the hyperplasia of fibrous connective tissue and collagen in group C were serious. The levels of group B were between group A and group C. The differences among three groups were significant (P < 0.05). Transmission electroscope showed inactive fibroblasts and loose thin collagen fibers in group A, and active fibroblasts and closely collagen fibers arranged in a disorderly manner in group C. CONCLUSION: Hydroxybutyl chitosan can decrease the hyperplasia of fibrous connective tissue and inhibit the activity of fibroblasts significantly, and has a long-term role of preventing peritoneal adhesion.

[Preparation of carboxymethyl-chitosan with different molecular weight and its effects on proliferation of skin fibroblasts and keratinocytes].

Effects of carboxymethyl-chitosan (CM-Chitosan) with different molecular weight on the proliferation of skin fibroblasts and keratinocytes were examined in vitro; bFGF and EGF, as controls, were seperately used for comparison. Chitosan with different molecular weight was prepared by acid degradation and oxidation degradation; CM-Chitosan with different molecular weight was synthesized from corresponding Chitosan. Microscopy and MTT method were applied to evaluate the different effects. The results demonstrated that CM-Chitosan with different molecular weight promoted the proliferation of skin fibroblasts and keratinocytes at 1-1000 ppm, and the concentration at 100 ppm had the strongest effects. The effects of low molecular weight CM-Chitosan were greater than those of high molecular weight CM-Chitosan. CM-Chitosan (Mn= 3KD) had the strongest promotive effects on skin fibroblasts and keratinocytes; it had equivalent effects when compared with bFGF and EGF.