Preparation of collagen-based materials for wound dressing.

OBJECTIVE: To describe the methods which were used to develop collagen-based materials for wound dressing. METHODS: Fresh frozen bovine tendon was treated with 0.05 mol/L acetic acid at pH 3.2 for 48-72 hours, homogenized, filtered, mixed with 8% chondroitin sulphate, for creating a deaerated 1.5%-2.5% collagen solution. The solution was lyophilized in either a pre-frozen or non-pre-frozen mould. The collagen sponge was then cross-linked with 0.25% glutaraldehyde for 24 hours. Three other types of wound dressings were developed using a similar method: collagen membrane with a polyurethane membrane onlay, polyurethane-coated collagen membrane and collagen membrane on gauze. RESULTS: It was demonstrated that the use of frozen bovine tendon was stable, and that the prepared collagen sponge contained pores of 50-400 microm in diameter. CONCLUSIONS: Collagen could be used as wound dressing.

[Study on combined implantation of pig dermis and autologous skin in rats].

In this study the treatment effect of combined implantation of autologous skin on pig dermis in injured rats was observed. Twenty-one Wistar rats were used, and the wounds were formed by excising a piece of full thickness skin on the back. After the pig dermis was implanted, the autologous skin was grafted on the dermis at 0.7 and 10 days. In the group with perforated pig dermis, the autograft skin was implanted on the day when the pig dermis was implanted. The healing effect was evaluated by measuring wound area, and by observing the growth of the autograft skin. Two weeks after the autograft skin was implanted, the skin securely adhered to the dermis, and the edge of autograft skin expanded clearly. The wound of the autograft skin implanted in the perforation of the dermis healed completely after 3 weeks, but the other 3 groups had remnant small wound. The autograft skin merged with the dermis and its surrounding tissue, but a clear dividing line still existed between autograft skin and dermis after implantation. The area of the implanted dermis and autograft skin varied from 51.8% to 65.9% compared to its original size. The results suggested that the time and the way of autologous skin grafting on xenogenous dermis may influence wound contraction and healing time.

[Development of a freezing drier for lyophilization of biomaterials].

To observe and assess the performance and effect of our self-made FD-1 freezing drier on biomaterials. R502 compressor and R502 refrigerating agent were adopted. In the experiment, FD-1 lyophilized collagen sponge, strain and defibrinogenase. The evaporating-condenser temperature reached -45 degrees C and the small icebox temperature reached -30 degrees C under the loading or free-loading circumstances in the lyophilizing box. The lyophilized collagen sponge had many pores in the structure, and the strain and the defibrinogenase were lyophilized and maintained satisfactorily. This freezing drier is suitable for lyophilizing some biomaterial samples in small or medium batches.

Silver nanoparticle/bacterial cellulose gel membranes for antibacterial wound dressing: investigation in vitro and in vivo.

Bacterial cellulose (BC) has attracted increasing attention as a novel wound dressing material, but its antimicrobial activity, which is one of the critical skin-barrier functions in wound healing, is not sufficient for use in practical applications. To overcome such a deficiency, silver nanoparticles were generated and self-assembled on the surface of BC nanofibers, forming a stable and evenly distributed Ag nanoparticle coated BC nanofiber (AgNP-BC). The performance of AgNP-BC was systematically studied in terms of antibacterial activities, cytocompatibility and effects on wound healing. The results showed that AgNP-BC exhibited significant antibacterial activity against Staphylococcus aureus. Moreover, AgNP-BC allowed attachment, and growth of rat fibroblasts with low cytotoxicity emerged. Based on these advantages, AgNP-BC samples were applied in a second-degree rat wound model. Wound flora showed a significant reduction during the healing. The fresh epidermal and dermis thicknesses with AgNP-BC samples were 111 and 855 µm respectively, higher than 74 and 619 µm for BC groups and 57 and 473 µm for untreated control wounds. The results demonstrated that AgNP-BC could reduce inflammation and promote scald wound healing.

In situ synthesis of silver-nanoparticles/bacterial cellulose composites for slow-released antimicrobial wound dressing.

Bacterial cellulose has attracted increasing attention as a novel wound dressing material, but it has no antimicrobial activity, which is one of critical skin-barrier functions in wound healing. To overcome such deficiency, we developed a novel method to synthesize and impregnate silver nanoparticles on to bacterial cellulose nanofibres (AgNP-BC). Uniform spherical silver nano-particles (10-30 nm) were generated and self-assembled on the surface of BC nano-fibers, forming a stable and evenly distributed Ag nanoparticles coated BC nanofiber. Such hybrid nanostructure prevented Ag nanoparticles from dropping off BC network and thus minimized the toxicity of nanoparticles. Regardless the slow Ag(+) release, AgNP-BC still exhibited significant antibacterial activities with more than 99% reductions in Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Moreover, AgNP-BC allowed attachment and growth of epidermal cells with no cytotoxicity emerged. The results demonstrated that AgNP-BC could reduce inflammation and promote wound healing.

Research of PDGF-BB gel on the wound healing of diabetic rats and its pharmacodynamics.

BACKGROUND: One of the leading causes of impaired wound healing is diabetes mellitus. In diabetic patients, a minor skin wound often leads to serious complications. Many experiments had demonstrated that the expression of platelet-derived growth factor (PDGF) and its receptor was decreased in wounds of healing-impaired diabetic mice, indicating that a certain expression level of PDGF is essential for normal repair. MATERIALS AND METHODS: The diabetic rats was induced by a single i.p. injection of streptozotocin and a 1.8 cm diameter full-thickness wound was made on each side of the rat mid-back. Then the rats were randomly divided into five groups, with eight animals in each group as follows: blank control, vehicle control, 3.5 microg PDGF-BB/cm(2) treatment group, 7 microg PDGF-BB/cm(2) treatment group and 14 microg PDGF-BB/cm(2) treatment group for either 7 or 14 consecutive days after wounding. Re-epithelialization area was measured by computerized planimetry, percentage wound closure and percentage wound contraction was calculated, granulation tissue and collagen formation was assessed by Masson trichrome, cell proliferation (proliferating cell nuclear antigen staining) and angiogenesis (Factor VIII related antigen staining) was assessed by immunohistological methods. RESULTS: PDGF-BB treatment improved healing quality, enhanced angiogenesis, cell proliferation and epithelialization, and formed thicker and more highly organized collagen fiber deposition in full-thickness excisional wound of diabetic rats. The effects of topically applied PDGF-BB were dose-dependent. CONCLUSIONS: PDGF-BB is an important future clinical tool, particularly for stimulating soft tissue repair in patients with an impaired capacity for wound healing.