Huafeng Sun

The progress of silver nanoparticles in the antibacterial mechanism, clinical application and cytotoxicity.

Nanotechnology is a highly promising field, with nanoparticles produced and utilized in a wide range of commercial products. Silver nanoparticles (AgNPs) has been widely used in clothing, electronics, bio-sensing, the food industry, paints, sunscreens, cosmetics and medical devices, all of which increase human exposure and thus the potential risk related to their short- and long-term toxicity. Many studies indicate that AgNPs are toxic to human health. Interestingly, the majority of these studies focus on the interaction of the nano-silver particle with single cells, indicating that AgNPs have the potential to induce the genes associated with cell cycle progression, DNA damage and mitochondrial associated apoptosis. AgNPs administered through any method were subsequently detected in blood and were found to cause deposition in several organs. There are very few studies in rats and mice involving the in vivo bio-distribution and toxicity, organ accumulation and degradation, and the possible adverse effects and toxicity in vivo are only slowly being recognized. In the present review, we summarize the current data associated with the increased medical usage of nano-silver and its related nano-materials, compare the mechanism of antibiosis and discuss the proper application of nano-silver particles.

The roles of knitted mesh-reinforced collagen-chitosan hybrid scaffold in the one-step repair of full-thickness skin defects in rats.

Full-thickness skin defects represent a significant and urgent clinical problem. Dermal substitutes serving as a regenerative template to induce dermal reconstruction provide a promising method to treat serious skin defects. Although collagen-chitosan dermal scaffolds display good biocompatibility and a suitable porous structure for angiogenesis and tissue regeneration, their poor mechanical properties compromise their application. To develop a well-supported dermal substitute, a poly(l-lactide-co-glycolide) (PLGA) knitted mesh was fabricated and integrated with collagen-chitosan scaffold (CCS) to obtain a PLGA knitted mesh-reinforced CCS (PLGAm/CCS). The morphology of this PLGAm/CCS was investigated in vitro. To characterize the tissue response, specifically angiogenesis and tissue regeneration, the PLGAm/CCS was transplanted in combination with thin split-thickness autografts to repair full-thickness skin wounds using a one-step surgical procedure in Sprague-Dawley rats. These results were then compared with CCSs. At weeks 2, 4 and 8 after the operation, the healing wounds were imaged to analyse wound changes, and tissue specimens were harvested for histology, immunohistochemistry, real-time quantitative polymerase chain reaction and Western blot analysis. The results demonstrated that collagen-chitosan sponge in the PLGAm/CCS remained porous, interconnected and occupied the openings of PLGA mesh, and the incorporation of the PLGA knitted mesh into CCS improved the mechanical strength with little influence on its mean pore size and porosity. Following transplantation, PLGAm/CCS inhibited wound contraction, and effectively promoted neotissue formation and blood vessel ingrowth. In conclusion, the mechanical strength of the scaffolds plays an important role in the process of tissue regeneration and vascularization. The ability of PLGAm/CCS to promote angiogenesis and induce in situ tissue regeneration demonstrates its potential in skin tissue engineering.

Fabrication and characterization of poly(L-lactide-co-glycolide) knitted mesh-reinforced collagen-chitosan hybrid scaffolds for dermal tissue engineering.

Mechanical properties are essential considerations for the design of porous scaffolds in the field of tissue engineering. To develop a well-supported hybrid dermal substitute, poly(L-lactide-co-glycolide) (PLGA) yarns were knitted into a mesh with relative fixed loops, followed by incorporation into collagen-chitosan scaffolds (CCS) to obtain PLGA knitted mesh-reinforced CCS (PLGAm/CCS). The morphology and tensile strength in both the dry and wet state of PLGAm/CCS were investigated in vitro. To characterize the tissue response, specifically angiogenesis and tissue regeneration, PLGAm/CCS was embedded subcutaneously in Sprague-Dawley rats and compared with two control implants, i.e., PLGA mesh (PLGAm) and CCS. At weeks 1, 2, and 4 post surgery, tissue specimens were harvested for histology, immunohistochemistry, real-time quantitative PCR and Western blot analysis. These results demonstrated that the incorporation of PLGA knitted mesh into CCS can improve the mechanical strength with little influence on its mean pore size and porosity. After implantation, PLGAm/CCS can resist contraction and promote cell infiltration, neotissue formation, and blood vessel ingrowth, effectively. In conclusion, the mechanical strength of scaffolds can play a synergetic role in tissue regeneration and vascularization by maintaining its 3D microstructure. The ability of PLGAm/CCS to promote angiogenesis and induce in situ tissue formation demonstrates its strong potential in the field of skin tissue engineering.

Applications of knitted mesh fabrication techniques to scaffolds for tissue engineering and regenerative medicine.

Knitting is an ancient and yet, a fresh technique. It has a history of no less than 1,000 years. The development of tissue engineering and regenerative medicine provides a new role for knitting. Several meshes knitted from synthetic or biological materials have been designed and applied, either alone, to strengthen materials for the patching of soft tissues, or in combination with other kinds of biomaterials, such as collagen and fibroin, to repair or replace damaged tissues/organs. In the latter case, studies have demonstrated that knitted mesh scaffolds (KMSs) possess excellent mechanical properties and can promote more effective tissue repair, ligament/tendon/cartilage regeneration, pipe-like-organ reconstruction, etc. In the process of tissue regeneration induced by scaffolds, an important synergic relationship emerges between the three-dimensional microstructure and the mechanical properties of scaffolds. This paper presents a comprehensive overview of the status and future prospects of knitted meshes and its KMSs for tissue engineering and regenerative medicine.

Topically applied rhGM-CSF for the wound healing: A systematic review

The process of wound healing involves a complex interplay of cells, mediators, growth factors and cytokines. GM-CSF has been shown to be involved in a number of processes essential in this event. Topically applied rhGM-CSF has been reported to successfully treat wounds with diverse etiology, including burns, chronic venous leg ulcers, pressure ulcers, and leprosy ulcers, both in animal experiments and clinical studies. To evaluate the effect of the rhGM-CSF on wound healing, 8 RCT studies and 23 clinical studies and case reports are collected for analysis of the evidence. The overall effects of rhGM-CSF on the healing of wound are diverse. Topically applied rhGM-CSF is beneficial for deep partial-thickness burn wounds, chronic leg ulcers, and leprosy ulcers. rhGM-CSF may have a positive effect on other type of chronic ulcers such as pressure ulcers and cancer related ulcers, but the evidence is not sufficient for generalised use at present. rhGM-CSF is suggested have no accelerating effect on the healing of healthy wounds or surgical incisions.

Promotion of angiogenesis by sustained release of rhGM-CSF from heparinized collagen/chitosan scaffolds.

A novel dermal substitute of combining recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) with a porous heparinized collagen/chitosan scaffolds was developed, considering the inadequate angiogenesis during repair of full-thickness skin defects. The physicochemical properties of heparinized collagen/chitosan scaffolds were examined and in vitro release pattern of rhGM-CSF from scaffolds was measured by ELISA. Four groups of composite scaffolds (heparinized or unheparinized scaffolds loaded with or without rhGM-CSF) were fabricated for subcutaneous implantation in young adult male Sprague-Dawley (SD) rats. Tissue specimens were harvested at different time points after implantation for histopathological, immunohistochemical observation, and Western blotting analysis. The heparinized scaffolds (H(1)E) showed slower biodegradation and sustained release of rhGM-CSF in vitro, although no significantly different release pattern was observed between the H(1)E and unheparinized scaffolds (H(0)E). In vivo investigation revealed that the heparinized scaffolds loaded with rhGM-CSF (H(1)E/rhGM-CSF) had the best cellular adhesion and migration, new vessel formation, and highest expression of VEGF and TGF-β1, indicating promoted angiogenesis. This study demonstrated that composite dermal substitute of combining rhGM-CSF with a porous heparinized collagen/chitosan scaffolds could be a potential therapeutic agent for full-thickness skin defects because of its sustained delivery of rhGM-CSF.

Epidermal cells delivered for cutaneous wound healing

Abstract Re-epithelialization is the first and most important step in cutaneous wound healing. The vital role of epidermal cells, or keratinocytes, in accelerating wound healing has long been established. The technique of delivering the cultured and uncultured epidermal cells to the wound bed takes a variety of forms including cultured epithelial autografts (CEAs), tissue-engineered skin equivalent, epidermal suspension and microbead-loaded composite. These techniques, together with the keratinocyte culturing method and scaling up equipment, are still the ongoing research. Application of these techniques also bears direct impact on the outcome of the wounded patients. Best understanding of the delivery technique and its relationship with the culturing method and delivery vehicle could benefit not only the wounded patient but also the development of tissue-engineered skin equivalent.