Photocrosslinkable chitosan hydrogel containing fibroblast growth factor-2 stimulates wound healing in healing-impaired db/db mice

Application of ultraviolet light (UV-) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution including fibroblast growth factor-2 (FGF-2) resulted within 30s in an insoluble, flexible hydrogel. About 20% of the FGF-2molecules were released from the FGF-2-incorporated chitosan hydrogel into phosphate buffered saline (PBS) within 1 day, after which no further significant release occurred under in vitro non-degradation conditions of the hydrogel. The FGF-2molecules retained in the chitosan hydrogel remained biologically active, and were released from the chitosan hydrogel upon the in vivo biodegradation of the hydrogel. In order to evaluate its accelerating effect on wound healing, full thickness skin incisions were made on the back of healing-impaired diabetic (db/db) mice and their normal (db/+) littermates. Application of the chitosan hydrogel significantly induced wound contraction and accelerated wound closure in both db/db and db/+ mice. However, the addition of FGF-2 in the chitosan hydrogel further accelerated wound closure in db/db mice, although not in db/+ mice. Histological examination also has demonstrated an advanced granulation tissue formation, capillary formation and epithelialization in wounds treated with FGF-2-incorporated chitosan hydrogels in db/db mice.     

The interaction of chitosan with fibroblast growth factor-2 and its protection from inactivation

Application of ultraviolet light (UV) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution including fibroblast growth factor-2 (FGF-2) results within 30s in an insoluble, flexible hydrogel. The retained FGF-2 molecules in the chitosan hydrogel remain biologically active, and are released from the chitosan hydrogel upon the in vivo biodegradation of the hydrogel. In view of these findings, we here tested the interaction of chitosan with FGF-2, thereby modifying and stabilizing the FGF-2 activity from inactivations. The photocrosslinkable chitosan hydrogel has a low affinity for FGF-2 (Kd = 6.12 x 10(-7) M). Soluble chitosan (CH-LA; Az-CH-LA without photocrosslinkable azide group) substantially prolonged the biological half-life time of FGF-2. Furthermore, CH-LA could protect the FGF-2 activity from inactivation, such as heat, proteolysis, and acid. The effect of chitosan on the FGF-2 activity is of a protective nature, since it had no effect of modifying the FGF-2 activity directly on growth of human umbilical vein endothelial cells (data not shown). Thus, one of the ways by which the chitosan potentiated the FGF-2 activity could be through protecting it from inactivations by the interaction between FGF-2 and chitosan molecules.     

Chitosan hydrogel as a drug delivery carrier to control angiogenesis

An aqueous solution of photocrosslinkable chitosan containing azide groups and lactose moieties (Az-CH-LA) incorporating paclitaxel formed an insoluble hydrogel within 30 s of ultraviolet light (UV) irradiation. The chitosan hydrogel showed strong potential for use as a new tissue adhesive in surgical applications and wound dressing. The fibroblast growth factor (FGF)-2 molecules retained in the chitosan hydrogel and in an injectable chitosan/IO₄-heparin hydrogel remain biologically active, and were gradually released from the hydrogels as they biodegraded in vivo. The controlled release of biologically active FGF-2 molecules from the hydrogels caused induction of angiogenesis and collateral circulation occurred in healing-impaired diabetic (db/db) mice and in the ischemic limbs of rats. Paclitaxel, which is an antitumor reagent, was also retained in the chitosan hydrogel and remained biologically active as it was released on degradation of the hydrogel in vivo. The chitosan hydrogels incorporating paclitaxel effectively inhibited tumor growth and angiogenesis in mice. The purpose of this review is to describe the effectiveness of chitosan hydrogel as a local drug delivery carrier for agents (e.g., FGF-2 and paclitaxel) to control angiogenesis. It is thus proposed that chitosan hydrogel may be a promising new local carrier for drugs such as FGF-2 and paclitaxel to control vascularization.     

Controlled release of fibroblast growth factors and heparin from photocrosslinked chitosan hydrogels and subsequent effect on in vivo vascularization

Application of ultraviolet (UV) irradiation to a photocrosslinkable chitosan (Az-CH-LA) aqueous solution resulted within 10 s in an insoluble, flexible hydrogel. A low molecular weight acidic molecule like trypan blue and various high molecular weight molecules such as bovine serum albumin (BSA), heparin and protamine were all retained within the hydrogel, while a low molecular weight basic molecule like toluidine blue was rapidly released from the hydrogel. In the present work, we examined the retaining capability of the chitosan hydrogel for growth factors and controlled release of growth factors from the chitosan hydrogel in vitro and in vivo. Fibroblast growth factor-1 (FGF-1), fibroblast growth factor-2 (FGF-2), vascular endothelial growth factor(165) (VEGF(165)), heparin-binding epidermal growth factor (HB-EGF) in phosphate buffered saline (PBS) were mixed with Az-CH-LA aqueous solution to form growth factor-incorporated chitosan hydrogels. About 10-25% of the growth factor was released from a growth factor-incorporated chitosan hydrogel into PBS within the first day, after which no further substantial release took place. The growth factors interacted with Az-CH-LA molecules poly-ion complexation, and probably were unable to be released after the first day under the in vitro nondegradation conditions of the hydrogel. Although the FGF-1, FGF-2, and VEGF(165)-incorporated chitosan hydrogels on a culture plate significantly stimulated HUVEC growth, the stimulating activity of the growth factor-incorporated chitosan hydrogel was completely cancelled out by washing the hydrogel with PBS solution for 3 days or more. The stimulating activity on the HUVEC growth were however highly recovered by treating the washed growth factor-incorporated chitosan hydrogel during 7 days with chitinase and chitosanase to partly degrade the hydrogel, strongly suggesting that the growth factors within the hydrogel retained their biologically active forms. The chitosan hydrogel (100 microl) when implanted into the back of a mouse was biodegraded in about 10-14 days. When FGF-1- and FGF-2-incorporated chitosan hydrogels were subcutaneously implanted into the back of a mouse, significant neovascularization was induced near the implanted site of the FGF-1- and FGF-2-incorporated chitosan hydrogels. Furthermore, addition of heparin with either FGF-1 or FGF-2 into the hydrogel resulted in a significantly enhanced and prolonged vascularization effect. These results indicate that the controlled release of biologically active FGF-1 and FGF-2 with heparin is caused by biodegradation of the chitosan hydrogel, and subsequent induction of vascularization.     

Wound healing properties of PVA/starch/chitosan hydrogel membranes with nano Zinc oxide as antibacterial wound dressing material

In this work, hydrogel membranes were developed based on poly vinyl alcohol (PVA), starch (St), and chitosan (Cs) hydrogels with nano Zinc oxide (nZnO). PVA/St/Cs/nZnO hydrogel membranes were prepared by freezing-thawing cycles, and the aqueous PVA/St solutions were prepared by dissolving PVA in distilled water. After the dissolution of PVA, starch was mixed, and the mixture was stirred. Then, chitosan powder was added into acetic acid, and the mixture was stirred to form a chitosan solution. Subsequently, Cs, St and PVA solutions were blended together to form a homogeneous PVA/St/Cs ternary blend solution. Measurement of Equilibrium Swelling Ratio (ESR), Water Vapor Transmission Test (WVTR), mechanical properties, scanning electron microscopy (SEM), MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide] assay, antibacterial studies, in vivo wound healing effect and histopathology of the hydrogel membranes were then performed. The examination revealed that the hydrogel membranes were more effective as a wound dressing in the early stages of wound healing and that the gel could be used in topic applications requiring a large spectrum of antibacterial activity; namely, as a bandage for wound dressing.     

Photocrosslinkable chitosan as a biological adhesive

A photocrosslinkable chitosan to which both azide and lactose moieties were introduced (Az-CH-LA) was prepared as a biological adhesive for soft tissues and its effectiveness was compared with that of fibrin glue. Introduction of the lactose moieties resulted in a much more water-soluble chitosan at neutral pH. Application of ultraviolet light (UV) irradiation to photocrosslinkable Az-CH-LA produced an insoluble hydrogel within 60 s. This hydrogel firmly adhered two pieces of sliced ham with each other, depending upon the Az-CH-LA concentration. The binding strength of the chitosan hydrogel prepared from 30-50 mg/mL of Az-CH-LA was similar to that of fibrin glue. Compared to the fibrin glue, the chitosan hydrogel more effectively sealed air leakage from pinholes on isolated small intestine and aorta and from incisions on isolated trachea. Neither Az-CH-LA nor its hydrogel showed any cytotoxicity in cell culture tests of human skin fibroblasts, coronary endothelial cells, and smooth muscle cells. Furthermore, all mice studied survived for at least 1 month after implantation of 200 microL of photocrosslinked chitosan gel and intraperitoneal administration of up to 1 mL of 30 mg/mL of Az-CH-LA solution. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new tissue adhesive in medical use.     

Effect of chitosan film containing basic fibroblast growth factor on wound healing in genetically diabetic mice

Basic fibroblast growth factor (bFGF) has been shown to stimulate wound healing. However, consistent delivery of bFGF has been problematic. We studied the stability of bFGF incorporated into a chitosan film as a delivery vehicle for providing sustained release of bFGF. The therapeutic effect of this system on wound healing in genetically diabetic mice was determined as a model for treating clinically impaired wound healing. A chitosan film was prepared by freeze-drying hydroxypropylchitosan (a water-soluble derivative of chitosan) acetate buffer solution. Growth factor was incorporated into films before drying by mixing bFGF solution with the hydroxypropylchitosan solution. bFGF activity remained stable for 21 days at 5 degrees C, and 86.2% of activity remained with storage at 25 degrees C. Full-thickness wounds were created on the backs of diabetic mice, and chitosan film or bFGF-chitosan film was applied to the wound. The wound was smaller in after 5 days in both groups, but the wound was smaller on day 20 only in the bFGF-chitosan group. Proliferation of fibroblasts and an increase in the number of capillaries were observed in both groups, but granulation tissue was more abundant in the bFGF-chitosan group. These results suggest that chitosan itself facilitates wound repair and that bFGF incorporated into chitosan film is a stabile delivery vehicle for accelerating wound healing.     

Water-soluble chitin as a wound healing accelerator.

Water-soluble chitin (WSC) was prepared by controlling degree of deacetylation (DD) and molecular weight of chitin through alkaline and ultrasonic treatment. Its accelerating effect on wound healing in rats was compared with those of chitin and chitosan. Full-thickness skin incision was made on the backs of the rats and then three kinds of powders (chitin, chitosan, WSC) and an aqueous solution of WSC were embedded in the wounds. The tensile strength and the hydroxyproline content of the wounded skins were measured and histological examination was performed. The WSC was found to be more efficient than chitin or chitosan as a wound-healing accelerator. The wound treated with WSC solution was completely reepithelialized, granulation tissues in the wound were nearly replaced by fibrosis and hair follicles were almost healed at 7 days after initial wounding. Also, the WSC-solution-treated skin had the highest tensile strength and the arrangement of collagen fibers in the skin was similar to normal skins. The WSC solution is considered to be a suitable wound-healing agent due to its easy application and high effectiveness.     

Medium (DMEM/F12)-containing chitosan hydrogel as adhesive and dressing in autologous skin grafts and accelerator in the healing process

Autologous skin grafts are considered necessary for the treatment of extensive skin defects. However, skin graft by suturing is a time-consuming medical handling and rather stressful event for recipients. To that end, tissue adhesives have been suggested in skin grafts. Chitosan hydrogel is well known as a wound dressing and tissue adhesive material showing biocompatibility, anti-infective activity, and the ability to accelerate wound healing. In this report, we evaluated the application of the chitosan hydrogel as a tissue adhesive in skin grafts. Although chitosan hydrogel shortened the operation time and resulted in a high graft absorption rate in comparison with suturing, wound epithelization was rather retarded. On the other hand, chitosan hydrogel was found more biocompatible than the commonly used tissue adhesive octyl-2-cyanoacrylate. When the chitosan hydrogel was premixed with a serum-free tissue culture medium DMEM/F12, it was found to easily degrade and promote wound epithelization. Histological examination revealed that the medium (DMEM/F12)-containing chitosan hydrogel was associated with the accumulation of polymorphonuclear leukocytes and neovascularization. In addition, immunohistochemical staining showed that the vascular endothelial growth factor (VEGF) was localized in the chitosan hydrogel degraded matrices. And infiltration of leukocytes determined the degradation activity with the D-glucose in the medium (DMEM/F12) suggested to play a central role in chitosan hydrogel degradation. Therefore, the medium (DMEM/F12)-containing chitosan hydrogel may become commonly accepted as a beneficial wound dressing and tissue adhesive in extensive wound management and skin grafts.     

超快动态交联的可注射壳聚糖-透明质酸水凝胶及促创伤愈合研究

可注射动态水凝胶是近年研究的热点,而制备无催化剂体系的快速交联的可注射动态水凝胶是研究的难点之一。以甲基丙烯酰化壳聚糖(CHMA)和醛基化透明质酸(ALHA)为原料,利用CHMA分子上的氨基与ALHA分子上的醛基和羧基,分别形成可逆动态席夫碱键和静电相互作用,可快速制备一种水凝胶。通过动态流变分析仪表征其凝胶化速率、剪切变稀行为和自愈合特征,通过体外细胞三维培养实验评估其细胞相容性,并通过急性全层皮肤创伤修复实验对其创伤愈合速率进行评估。结果表明,只需5 s,CHMA和ALHA的混合溶液就能形成凝胶。此外,该凝胶具有剪切变稀和快速自愈合的可注射特征,当扫描频率从10^-1 s^-1增加至10² s^-1时,其复数黏度由0.4 kPa降低至8 Pa;当应变在1%~1000%之间交替变化时,储能模量与损耗模量的大小能够迅速切换,且模量没有显著性地降低。同时,体外细胞三维培养实验表明,该水凝胶还具有优异的细胞相容性(细胞存活率高于95%),并且在雄性ICR小鼠急性全层皮肤缺损模型实验中,水凝胶组的创伤愈合时间相比空白对照组缩短5～7 d,表现出较快的创伤愈合速率。综上可见,这种可注射壳聚糖-透明质酸水凝胶在生物医药、组织功能、临床医学等领域具有广阔的应用前景。     

Effects of bFGF incorporated into a gelatin sheet on wound healing

Basic fibroblast growth factor (bFGF) is well known to promote the proliferation of almost all cells associated with wound healing. However, as the activation duration of bFGF is very short in vivo, we incorporated bFGF into an acidic gelatin hydrogel and studied the sustained release of bFGF in vivo. In addition, we investigated the effects of the acidic gelatin sheet containing bFGF on wound healing. To distinguish wound contraction from neoepithelialization, we measured both the wound area and neoepithelium length. Other histological parameters such as thickness of granulation tissue and number of capillaries were also determined as indices of wound healing. Fibrous tissue was assessed using an Elastica van Gieson and Azan stain. A skin defect (1.5 x 1.5 cm) of full thickness was created on the back of each test mouse and the wound was covered with an acidic gelatin hydrogel, referred to as a gelatin sheet in this study (2 x 2 cm), with bFGF (100 microg/site) (A) or without bFGF (B). 1, 2, 3, 5, 7 and 14 days after covering, mice were killed and an enzyme-linked immunosorbent assay (ELISA) was performed to estimate the concentration of bFGF in the plasma. In another experiment, each wound was covered with (A), (B) or a hydrogel dressing (control group, C) and the wound area was measured 1 or 2 weeks postoperatively with a computer planimeter. The histological parameters, as mentioned above, were assessed using a light microscope. Sustained release of bFGF from the gelatin sheet was observed and the gelatin sheet containing bFGF promoted neoepithelialization, granulation, neovascularization and wound closure. This gelatin sheet containing bFGF was concluded to be effective for wound healing and promising for clinical use.     

Vascularization in vivo caused by the controlled release of fibroblast growth factor-2 from an injectable chitosan/non-anticoagulant heparin hydrogel

Addition of various heparinoids to the lactose-introduced, water-soluble chitosan (CH-LA) aqueous solution produces an injectable chitosan/heparinoid hydrogel. In the present work, we examined the capability of the chitosan/non-anticoagulant heparin (periodate-oxidized (IO(4)-) heparin) hydrogel to immobilize fibroblast growth factor (FGF)-2, as well as the controlled release of FGF-2 molecules from the hydrogel in vitro and in vivo. The hydrogel was biodegraded in about 20 days after subcutaneous injection into the back of a mouse. When the FGF-2-incorporated hydrogel was subcutaneously injected into the back of both mice and rats, a significant neovascularization and fibrous tissue formation were induced near the injected site. These results indicate that the controlled release of biologically active FGF-2 molecules is caused by biodegradation of the hydrogel, and that subsequent induction of the vascularization occurs.     

Facile and large-scale synthesis of curcumin/PVA hydrogel: effectively kill bacteria and accelerate cutaneous wound healing in the rat

The complicated synthesis procedure and limited preparation size of hydrogel inhibit its clinical application. Therefore, a facile preparation method for large-size hydrogel is required. In this study, a series of curcumin (Cur)/polyvinyl alcohol (PVA) hydrogel in a large size with different Cur concentrations is prepared by a facile physical-chemical crosslinking. The physicochemical properties, antibacterial performance and accelerating wound healing ability are evaluated with the aim of attaining a novel and effective wound dressing. The results show that the as-prepared hydrogel with the optimal Cur to PVA volume ratio of 1:5 (20% Cur/PVA) exhibits the best antibacterial abilities to E. coli (85.6%) and S. aureus (97%) than other hydrogels. When the volume ratio of Cur to PVA is 1:10 (10% Cur/PVA), the hydrogel can significantly accelerate the wound healing in rats, and successfully reconstruct intact and thickened epidermis during 14 day of healing of impaired wounds after histological examination. In one word, the present approach can shed new light on designing new type of hydrogels with promising applications in wound dressing.     

组织工程生物绷带及敷料在创伤修复领域中的应用

背景：医用敷料作为伤口处的覆盖物,在伤口愈合过程中,可以替代受损的皮肤起到暂时性屏障作用,避免或控制伤口感染,提供有利于创面愈合的环境。如何既能快速固定、有效止血,又可以减轻或避免止血后对伤肢血循环造成的不利影响,加快伤口愈合、减轻伤痛是创伤急救医学亟待解决的难题。 目的：文章综述了医用生物敷料在创伤修复领域中的应用现状及研究进展,揭示其发展前景,为其在创伤修复过程中的应用提供理论基础。 方法：应用计算机检索CNKI和PubMed数据库中1998-01/2008-12关于医用生物敷料的文章,在标题和摘要中以“医用敷料;生物材料,壳聚糖,水凝胶,组织工程”或“medical dressing,chitosan”为检索词进行检索。选择文章内容与创伤修复相关,同一领域文献则选择近期发表或发表在权威杂志文章。初检得到146篇文献,中文107篇,英文39篇,根据纳入标准选择38篇文章进行综述。 结果与结论：就目前临床使用及研究的医用敷料,根据其所用的材料将其分成了天然材料和合成高分子,无机材料和复合材料,并对敷料类产品质量控制中出现的问题进行了讨论,展望了敷料类产品的未来发展方向。为医用敷料类产品的研发提供理论依据。     

Sequential antibiotic and growth factor releasing chitosan-PAAm semi-IPN hydrogel as a novel wound dressing

The aim of this study is to prepare a novel wound dressing material which provides burst release of an antibiotic in combination with sustained release of growth factor delivery. This might be beneficial for the prevention of infections and to stimulate wound healing. As a wound dressing material, the semi-interpenetrating network (semi-IPN) hydrogel based on polyacrylamide (PAAm) and chitosan (CS) was synthesized via free radical polymerization. Ethylene glycol dimethacrylate was used for cross-linking of PAAm to form semi-IPN hydrogel. The hydrogel shows high water content (～1800%, in dry basis) and stable swelling characteristics in the pH range of the wound media (～4.0–7.4). The antibiotic, piperacillin–tazobactam, which belongs to the penicillin group was loaded into the hydrogel. The therapeutic serum dose of piperacillin–tazobactam for topic introduction was reached at 1st hour of the release. Additionally, in order to increase the mitogenic activity of hydrogel, epidermal growth factor (EGF) was embedded into the CS–PAAm in different amounts. Cell culture studies were performed with L929 mouse fibroblasts and the simulated cell growth was investigated by 3-(4,5-dimethylthiazol-2-yl)-diphenyltetrazolium bromide assay. The successful sustained release behavior of CS–PAAm hydrogel for EGF maintained the presence of EGF in the culture up to 5?days and the highest mitochondrial activities were recorded for the 0.4?μg EGF-loaded/mg of hydrogel group. In conclusion, CS–PAAm semi-IPN hydrogel loaded with piperacillin–tazobactam and EGF could be proposed for an effective system in wound-healing management.     

Wound pH-Responsive Sustained Release of Therapeutics from a Poly(NIPAAm-co-AAc) Hydrogel

Wound pH strongly influences residence time and activity of various growth factors during wound healing. Hence, a pH-responsive sustained release growth factor delivery system could be beneficial for effective treatment of wound. In this context, an effort was made to evaluate the potential of a poly(N-isopropylacrylamide-co-acrylic acid) hydrogel as pH-sensitive sustained release system for wound-pH-dependent therapeutics delivery. The polymer was synthesized via radical copolymerization and influence of pH on lower critical solution temperature (LCST), microarchitechture and swelling of the hydrogel was evaluated. Results showed a pH-dependent variation in the physical properties of the hydrogel within the wound pH range. Fluorescence recovery after photobleaching (FRAP) analysis endorsed a pH dependent restricted diffusion of the BSA in the hydrogel. Later, release of bovine serum albumin (BSA), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) (each 5%, w/v) from the hydrogel within the range of wound pH (pH 6.7–7.9) were examined. Analysis showed non-Fickian release of therapeutics from the hydrogel with a significant variation in release rate and cumulative release with the increase in pH. Retention of the bioactivity of the released EGF was confirmed by studying murine dermal fibroblast cell proliferation in vitro. Finally, a growth factor (EGF or VEGF)-loaded hydrogel was applied on a murine excisional wound model and showed augmentation of wound healing in comparison to conventional sustained release growth factor therapy.     

Oxidized dextrins as alternative crosslinking agents for polysaccharides: Application to hydrogels of agarose–chitosan

Hydrogel networks that combine suitable physical and biomechanical characteristics for tissue engineering scaffolds are in demand. The aim of this work was the development of hydrogel networks based on agarose and chitosan using oxidized dextrins as low cytotoxicity crosslinking agents, paying special attention to the study of the influence of the polysaccharide composition and oxidation degree of the dextrins in the final characteristics of the network. The results show that the formation of an interpenetrating or a semi-interpenetrating polymer network was mainly dependent on a minimum agarose content and degree of oxidation of dextrin. Spectroscopic, thermal and swelling analysis revealed good compatibility with an absence of phase separation of polysaccharides at agarose:chitosan proportions of 50:50 and 25:75. The analysis of atomic force microscopy images showed the formation of a fibrillar microstructure whose distribution within the crosslinked chitosan depended mainly on the crosslinker. All materials exhibited the viscoelastic behaviour typical of gels, with a constant storage modulus independent of frequency for all compositions. The stiffness was strongly influenced by the degree of oxidation of the crosslinker. Cellular response to the hydrogels was studied with cells of different strains, and cell adhesion and proliferation was correlated with the homogeneity of the samples and their elastic properties. Some hydrogel formulations seemed to be candidates for tissue engineering applications such as wound healing or soft tissue regeneration.     

Wound pH-responsive sustained release of therapeutics from a poly(NIPAAm-co-AAc) hydrogel

Wound pH strongly influences residence time and activity of various growth factors during wound healing. Hence, a pH-responsive sustained release growth factor delivery system could be beneficial for effective treatment of wound. In this context, an effort was made to evaluate the potential of a poly(N-isopropylacrylamide-co-acrylic acid) hydrogel as pH-sensitive sustained release system for wound-pH-dependent therapeutics delivery. The polymer was synthesized via radical copolymerization and influence of pH on lower critical solution temperature (LCST), microarchitechture and swelling of the hydrogel was evaluated. Results showed a pH-dependent variation in the physical properties of the hydrogel within the wound pH range. Fluorescence recovery after photobleaching (FRAP) analysis endorsed a pH dependent restricted diffusion of the BSA in the hydrogel. Later, release of bovine serum albumin (BSA), vascular endothelial growth factor (VEGF) and epidermal growth factor (EGF) (each 5%, w/v) from the hydrogel within the range of wound pH (pH 6.7-7.9) were examined. Analysis showed non-Fickian release of therapeutics from the hydrogel with a significant variation in release rate and cumulative release with the increase in pH. Retention of the bioactivity of the released EGF was confirmed by studying murine dermal fibroblast cell proliferation in vitro. Finally, a growth factor (EGF or VEGF)-loaded hydrogel was applied on a murine excisional wound model and showed augmentation of wound healing in comparison to conventional sustained release growth factor therapy.     

Arginine-based polyester amide/polysaccharide hydrogels and their biological response

An advanced family of biodegradable cationic hybrid hydrogels was designed and fabricated from two precursors via a UV photocrosslinking in an aqueous medium: unsaturated arginine (Arg)-based functional poly(ester amide) (Arg-UPEA) and glycidyl methacrylate chitosan (GMA-chitosan). These Arg-UPEA/GMA-chitosan hybrid hydrogels were characterized in terms of their chemical structure, equilibrium swelling ratio (Q_eq), compressive modulus, interior morphology and biodegradation properties. Lysozyme effectively accelerated the biodegradation of the hybrid hydrogels. The mixture of both precursors in an aqueous solution showed near non-cytotoxicity toward porcine aortic valve smooth muscle cells at total concentrations up to 6 mg ml⁻¹. The live/dead assay data showed that 3T3 fibroblasts were able to attach and grow on the hybrid hydrogel and pure GMA-chitosan hydrogel well. Arg-UPEA/GMA-chitosan hybrid hydrogels activated both TNF-α and NO production by RAW 264.7 macrophages, and the arginase activity was also elevated. The integration of the biodegradable Arg-UPEA into the GMA-chitosan can provide advantages in terms of elevated and balanced NO production and arginase activity that free Arg supplement could not achieve. The hybrid hydrogels may have potential application as a wound healing accelerator.     

Tissue regeneration using macrophage migration inhibitory factor-impregnated gelatin microbeads in cutaneous wounds

Migration inhibitory factor (MIF) responds to tissue damage and regulates inflammatory and immunological processes. To elucidate the function of MIF in cutaneous wound healing, we analyzed MIF knockout (KO) mice. After the excision of wounds from the dorsal skin of MIF KO and wild-type (WT) mice, healing was significantly delayed in MIF KO mice compared to WT mice. Lipopolysaccharide treatment significantly increased [(3)H]thymidine uptake in WT mouse fibroblasts compared to MIF KO mouse fibroblasts. Furthermore, there was a significant reduction in fibroblast and keratinocyte migration observed in MIF KO mice after 1-oleoyl-2-lysophosphatidic acid treatment. We subsequently examined whether MIF-impregnated gelatin slow-release microbeads could accelerate skin wound healing. Injection of more than 1.5 microg/500 microl of MIF-impregnated gelatin microbeads around a wound edge accelerated wound healing compared to a single MIF injection without the use of microbeads. MIF-impregnated gelatin microbeads also accelerated skin wound healing in C57BL/6 mice and diabetic db/db mice. Furthermore, incorporating MIF-impregnated gelatin microbeads into an artificial dermis implanted into MIF KO mice accelerated procollagen production and capillary formation. These findings suggest that MIF is crucial in accelerating cutaneous wound healing and that MIF-impregnated gelatin microbeads represent a promising treatment to facilitate skin wound healing.