Xinlei Hu

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.

AGEs and chronic subclinical inflammation in diabetes: disorders of immune system

Chronic subclinical inflammation represents a risk factor of type 2 diabetes and several diabetes complications, including neuropathy and atherosclerosis including macro‐vasculopathy and micro‐vasculopathy. However, the inflammatory response in the diabetic wound was shown to be remarkably hypocellular, unregulated and ineffective. Advanced glycation end products (AGEs) and one of its receptors, RAGE, were involved in inducing chronic immune imbalance in diabetic patients. Such interactions attracts immune cell into diffused glycated tissue and activates these cells to induce inflammatory damage, but disturbs the normal immune rhythm in diabetic wound. Traditional measurements of AGEs are high‐performance liquid chromatography and immunohistochemistry staining, but their application faces the limitations including complexity, cost and lack of reproducibility. A new noninvasive method emerged in 2004, using skin autofluorescence as indicator for AGEs accumulation. It had been reported to be informative in evaluating the chronic risk of diabetic patients. Studies have indicated therapeutic potentials of anti‐AGE recipes. These recipes can reduce AGE absorption/de novo formation, block AGE–RAGE interaction and arrest downstream signaling after RAGE activation. Copyright

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.

Endostatin inhibits hypertrophic scarring in a rabbit ear model.

ObjectiveThe present study was designed to use an in vivo rabbit ear scar model to investigate the efficacy of systemic administration of endostatin in inhibiting scar formation.MethodsEight male New Zealand white rabbits were randomly assigned to two groups. Scar model was established by making six full skin defect wounds in each ear. For the intervention group, intraperitoneal injection of endostatin was performed each day after the wound healed (about 15 d post wounding). For the control group, equal volume of saline was injected. Thickness of scars in each group was measured by sliding caliper and the scar microcirculatory perfusion was assessed by laser Doppler flowmetry on Days 15, 21, 28, and 35 post wounding. Rabbits were euthanatized and their scars were harvested for histological and proteomic analyses on Day 35 post wounding.ResultsMacroscopically, scars of the control group were thicker than those of the intervention group. Significant differences between the two groups were observed on Days 21 and 35 (p<0.05). Scar thickness, measured by scar elevation index (SEI) at Day 35 post wounding, was significantly reduced in the intervention group (1.09±0.19) compared with the controls (1.36±0.28). Microvessel density (MVD) observed in the intervention group (1.73±0.94) was significantly lower than that of the control group (5.63±1.78) on Day 35. The distribution of collagen fibers in scars treated with endostatin was relatively regular, while collagen fibers in untreated controls were thicker and showed disordered alignment. Western blot analysis showed that the expressions of type I collagen and Bcl-2 were depressed by injection of endostatin.ConclusionsOur results from the rabbit ear hypertrophic scar model indicate that systemic application of endostatin could inhibit local hypertrophic scar formation, possibly through reducing scar vascularization and angiogenesis. Our results indicated that endostatin may promote the apoptosis of endothelial cells and block their release of platelet-derived growth factor (PDGF) and fibroblast growth factor (FGF), thereby controlling collagen production by fibroblasts. Blood vessel-targeted treatment may be a promising strategy for scar therapy.

In vitro evaluation of Panax notoginseng Rg1 released from collagen/chitosan-gelatin microsphere scaffolds for angiogenesis

BackgroundThe emergence of skin substitutes provides a new approach for the treatment of wound repair and healing. The consistent and steady release of angiogenic factors is an important factor in the promotion of angiogenesis in skin substitutes, which usually lack, yet need, a vascular network.MethodsIn this study, ginsenoside Rg1, a natural compound isolated from Panax notoginseng (PNS), was incorporated into a collagen/chitosan-gelatin microsphere (CC-GMS) scaffold. The cumulative release kinetics were evaluated, and the effects of the released Rg1 on human umbilical vein endothelial cells (HUVECs) behavior, including proliferation, migration, tube formation, cell-cycle progression, cell apoptosis, and vascular endothelial growth factor (VEGF) secretion, were investigated. Additionally, HUVECs were cultured on the CC-GMS scaffold to test its biocompatibility. Standard Rg1 and VEGF were used as positive controls.ResultsThe results indicated that the CC-GMS scaffold had good release kinetics. The Rg1 released from the CC-GMS scaffold did not lose its activity and had a significant effect on HUVEC proliferation. Both Rg1 and VEGF promoted HUVEC migration and tube formation. Rg1 did not induce HUVEC apoptosis but instead promoted HUVEC progression into the S and G2/M phases of the cell cycle. Rg1 significantly increased VEGF secretion compared with that in the control group. HUVEC culture on the CC-GMS scaffold indicated that this scaffold has good biocompatibility and that CC-GMS scaffolds containing different concentrations of Rg1 promote HUVEC attachment in a dose- and time-dependent manner.ConclusionsRg1 may represent a new class of angiogenic agent that can be encapsulated in CC-GMS scaffolds to exert angiogenic effects in engineered tissue.

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.

Elevated serum uric acid after injury correlates with the early acute kidney in severe burns.

OBJECTIVE Early acute kidney injury (AKI) is one of the most serious and common complications in the early stage of severe burns, but the pathological mechanisms still need to be elucidated. High uric acid (UA) has been found to be correlated with renal dysfunction in some experimental and clinical studies; however, the study of the dynamic correlation between AKI and UA in severe burns is still lacking. METHODS The diagnosis and classification of AKI were performed according to RIFLE criteria, UA, serum creatinine (Scr), estimated glomerular filtration rate (eGFR), C-reactive protein (CRP) and lactic acid (LA) were dynamically monitored within 2 days after injury in 59 severely burned patients. RESULTS Within 2 days after injury, AKI occurred in 23 of 59 patients (risk in 12 cases, injury in seven cases and failure in four cases), UA level in AKI patients was significantly higher than that in No-AKI patients, and referring to the cutoff level of UA (375.5 μmol/l) from ROC curve for predicting AKI, the abnormal increase of UA levels was earlier than acute deterioration of renal function in most of the AKI patients after injury. Among AKI patients, the Scr/eGFR levels were closely related to UA levels for 2 days after injury. Moreover, UA level in cases with severe grade of AKI was significantly higher than that in those with less severe grade of AKI. Furthermore, there was a positive correlation between UA and CRP for 2 days after injury in AKI patients, and a significant correlation between CRP and Scr/eGFR was found 1 day after injury. The positive correlation was also found between LA and UA after injury in AKI patients. CONCLUSION The results suggest that elevated serum UA after injury due to hypoxia is closely correlated with early AKI after severe burns, and UA-related aberrant inflammation also appears to be one of the pathogenic factors, providing the useful information for potential therapy.