An In Vitro Study of the Effects of Mechanical and Enzymatic Isolation of Stromal Vascular Fraction on Wound Healing.

ABSTRACT: The adipose-derived stromal vascular fraction (SVF) is considered to be an attractive source of stem cells in cell therapy. Besides stem cells, it also contains functional cells, such as macrophages, precursor cells, somatic stem cells, and pericytes. Collagenase digestion is the most frequently used method to isolate SVF, but it is time-consuming and costly and has some problems, such as infectious agents and immune reactions. In this research, we compared the yield, cell population ratios, and cell viability when isolating SVF by the ultrasonic physics (U-SVF) method and traditional enzymatic method (E-SVF). Then, we isolated exosomes from U-SVF and E-SVF, respectively, and cocultured them with fibroblasts to investigate the potential of applying this cell secretion in wound repair. The results showed that there was no significant difference between the ultrasonic method and enzymatic method in terms of cell viability, cell numbers, or the expression of CD markers of stem cells. However, exosome analysis identified a greater number and smaller size of exosome particles obtained by U-SVF. In terms of cell proliferation efficiency, although the proliferation efficiency of U-SVF was lower than that of E-SVF. Trilineage differentiation experiments revealed that both E-SVF and U-SVF had good differentiation ability, owing to high stem cell content. Finally, E-SVF and U-SVF exosomes were cocultured with fibroblasts. The efficiency of fibroblast migration increased in the SVF exosome treated groups, and the expression of related genes (integrin α5ß1) was slightly upregulated; however, the expression of FAK, AKT, ERK, and RhoA was significantly upregulated at 24 hours. From the abovementioned experiments, we found that there was no significant difference in stem cell-related characteristics between SVF isolated by ultrasonic cavitation and SVF isolated by the enzymatic method. In addition, exosomes secreted by SVF may have excellent therapeutic effect on skin injuries, which provides a new viewpoint and therapeutic strategy for soft tissue repair.

Beneficial Effects of Astragaloside IV-Treated and 3-Dimensional-Cultured Endothelial Progenitor Cells on Angiogenesis and Wound Healing.

INTRODUCTION: Astragaloside IV (AS-IV) is a natural herb extract and a popular compound used in traditional Chinese medicine because of its effect on multiple biological processes, such as promotion of cell proliferation, improvement in cardiopulmonary and vascular function, and promotion of angiogenesis around wounds, leading to accelerated wound healing. Vascular regeneration primarily results from the differentiation of endothelial progenitor cells (EPCs). Biomedical acceleration of angiogenesis and differentiation of EPCs around the wound remain challenging. MATERIALS AND METHODS: In this study, we treated human umbilical cord blood-derived EPCs with AS-IV and cultured them on 2-dimensional (tissue culture polystyrene) and 3-dimensional culture plates (3DPs). These cultured cells were then combined with human blood plasma gel and applied on the skin of nude mice in an attempt to repair full-thickness skin defects. RESULTS: The results show that using 3DP culture could increase vascular-related gene expression in EPCs. Furthermore, 12.5 µg/mL AS-IV-treaded EPCs were combined with plasma gels (P-3DP-EPC12.5) and showed enhanced vascular-related protein expression levels after 3 days of culture. Finally, P-3DP-EPC12.5s were used to repair full-thickness skin defects in nude mice, and we could register a wound healing rate greater than 90% by day 14. CONCLUSIONS: Based on these results, we concluded that we have developed a potential therapeutic approach for wound healing using plasma gel containing 3-dimensional surface-cultured AS-IV-treated EPCs.

Evaluation of Polycaprolactone/Gelatin/Chitosan Electrospun Membrane for Peritoneal Adhesion Reduction.

In this study, a novel antiadhesion membrane made of polycaprolactone, gelatin, and chitosan was fabricated using the electrospinning technique. A series of polycaprolactone/gelatin/chitosan (PGC) electrospun membranes with different amounts of chitosan (0%, 0.5%, 1%, and 2% in weight percentage) was synthesized. The physicochemical properties and biocompatibility of the fabricated membranes were examined and compared with the aim to select an effective antiadhesion membrane. Scanning electron microscopy showed that these 4 electrospun membranes had similar fiber diameter and pore area, with no statistical differences between them. Furthermore, the contact angle decreased with increased chitosan content, indicating that chitosan may contribute to increased hydrophilic properties. The in vitro degradation test revealed that the higher chitosan content corresponded to a lower degradation rate in PGC membranes within 7 days. All PGC membranes exhibited similar cell proliferation; however, cell proliferation was lower than tissue culture polystyrene (P < 0.05). To compare antiadhesion ability, the adhesion between the cecum and abdominal wall was created in a rat model. Assessment after implantation of electrospun membranes revealed that PGCs with higher chitosan content (PGC2) had better antiadhesion effects, as evaluated by an adhesion score at day 14 postsurgery. Thus, PGC2 was effective in reducing the formation of tissue adhesion. Therefore, PGC electrospun membrane may provide a potential peritoneal antiadhesion barrier for clinical use.

A gelatin/collagen/polycaprolactone scaffold for skin regeneration.

BACKGROUND: A tissue-engineered skin substitute, based on gelatin ("G"), collagen ("C"), and poly(ε-caprolactone) (PCL; "P"), was developed. METHOD: G/C/P biocomposites were fabricated by impregnation of lyophilized gelatin/collagen (GC) mats with PCL solutions, followed by solvent evaporation. Two different GC:PCL ratios (1:8 and 1:20) were used. RESULTS: Differential scanning calorimetry revealed that all G/C/P biocomposites had characteristic melting point of PCL at around 60 °C. Scanning electron microscopy showed that all biocomposites had similar fibrous structures. Good cytocompatibility was present in all G/C/P biocomposites when incubated with primary human epidermal keratinocytes (PHEK), human dermal fibroblasts (PHDF) and human adipose-derived stem cells (ASCs) in vitro. All G/C/P biocomposites exhibited similar cell growth and mechanical characteristics in comparison with C/P biocomposites. G/C/P biocomposites with a lower collagen content showed better cell proliferation than those with a higher collagen content in vitro. Due to reasonable mechanical strength and biocompatibility in vitro, G/C/P with a lower content of collagen and a higher content of PCL (GCLPH) was selected for animal wound healing studies. According to our data, a significant promotion in wound healing and skin regeneration could be observed in GCLPH seeded with adipose-derived stem cells by Gomori's trichrome staining. CONCLUSION: This study may provide an effective and low-cost wound dressings to assist skin regeneration for clinical use.

Melanocyte Differentiation From Induced Pluripotent Stem Cells Derived From Human Adipose-Derived Stem Cells.

The pigment melanin is produced by melanocytes, is primarily responsible for skin color, and protects it against ultraviolet rays that can cause the destruction of genetic material within the keratinocytes. To elucidate the mechanisms of many diseases associated with melanocytes, such as melanoma and albinism, or burns with uneven pigment distribution, the disease model needs to be established first. In this study, we aimed to construct the melanocyte model from patients in a short period.Sandai virus vector containing 4 stemness genes (Oct4, Sox2, Klf4, c-Myc) was transfected into human adipose-derived stem cells to produce induced pluripotent stem cells (iPSCs). Immunofluorescence staining was used to confirm the expression of specific proteins for iPSCs, including Tra-1-60, Tra-1-81, Oct-4, Sox-2, and Nango. polymerase chain reaction results also showed that specific genes of iPSCs with the ability to cause the differentiation of cells into the 3 germ layers were expressed. In our in vivo experiments, iPSCs were subcutaneously injected into nude mice to induce teratoma formation for 2 months. The morphology of the 3 germ layers was confirmed by hematoxylin and eosin staining. Furthermore, melanocytes were purified by serial induction medium, and their presence was confirmed by flow cytometry and the expression of different markers for melanocytes.

Development of a Novel Pre-Vascularized Three-Dimensional Skin Substitute Using Blood Plasma Gel.

Skin substitutes with existing vascularization are in great demand for the repair of full-thickness skin defects. In the present study, we hypothesized that a pre-vascularized skin substitute can potentially promote wound healing. Novel three-dimensional (3D) skin substitutes were prepared by seeding a mixture of human endothelial progenitor cells (EPCs) and fibroblasts into a human plasma/calcium chloride formed gel scaffold, and seeding keratinocytes onto the surface of the plasma gel. The capacity of the EPCs to differentiate into a vascular-like tubular structure was evaluated using immunohistochemistry analysis and WST-8 assay. Experimental studies in mouse full-thickness skin wound models showed that the pre-vascularized gel scaffold significantly accelerated wound healing 7 days after surgery, and resembled normal skin structures after 14 days post-surgery. Histological analysis revealed that pre-vascularized gel scaffolds were well integrated in the host skin, resulting in the vascularization of both the epidermis and dermis in the wound area. Moreover, mechanical strength analysis demonstrated that the healed wound following the implantation of the pre-vascularized gel scaffolds exhibited good tensile strength. Taken together, this novel pre-vascularized human plasma gel scaffold has great potential in skin tissue engineering.

High correlation between skin color based on CIELAB color space, epidermal melanocyte ratio, and melanocyte melanin content.

BACKGROUND: To treat skin color disorders, such as vitiligo or burns, melanocytes are transplanted for tissue regeneration. However, melanocyte distribution in the human body varies with age and location, making it difficult to select the optimal donor skin to achieve a desired color match. Determining the correlations with the desired skin color measurement based on CIELAB color, epidermal melanocyte numbers, and melanin content of individual melanocytes is critical for clinical application. METHOD: Fifteen foreskin samples from Asian young adults were analyzed for skin color, melanocyte ratio (melanocyte proportion in the epidermis), and melanin concentration. Furthermore, an equation was developed based on CIELAB color with melanocyte ratio, melanin concentration, and the product of melanocyte ratio and melanin concentration. The equation was validated by seeding different ratios of keratinocytes and melanocytes in tissue-engineered skin substitutes, and the degree of fitness in expected skin color was confirmed. RESULTS: Linear regression analysis revealed a significant strong negative correlation (r =  - 0.847, R2 = 0.717) between CIELAB L* value and the product of the epidermal melanocyte ratio and cell-based melanin concentration. Furthermore, the results showed that an optimal skin color match was achieved by the formula. DISCUSSION: We found that L* value was correlated with the value obtained from multiplying the epidermal melanocyte ratio (R) and melanin content (M) and that this correlation was more significant than either L* vs M or L* vs R. This suggests that more accurate prediction of skin color can be achieved by considering both R and M. Therefore, precise skin color match in treating vitiligo or burn patients would be potentially achievable based on extensive collection of skin data from people of Asian descent.

Efficacy of Lyophilised Platelet-Rich Plasma Powder on Healing Rate in Patients With Deep Second Degree Burn Injury: A Prospective Double-Blind Randomized Clinical Trial.

Platelet-rich plasma (PRP) is a kind of plasma that is rich in platelets after processing. It includes various growth factors and cytokines, which speed up the process of wound healing and hemostasis. The PRP solution used in this study is diluted from lyophilized PRP powder, which decreased the possibility of contamination, facilitated the storage, and prolonged the storage life. From in vitro fibroblast proliferation testing, the numbers of PRP supplement were performed for 1, 4, and 7 times by continuous replacement of culture medium each day. Four times of lyophilized PRP supplement was selected for clinical study due to sufficient promotion of fibroblast proliferation. Next, 27 patients of deep second-degree burn wound were included in this study. Patients were assigned to two groups: PRP group (n = 15) and control group (n = 12). A concentration of 1.0 × 10 platelets/cm (wound area) according to wound size was sprayed on the wound evenly. Function was mainly assessed by the percentage of wound closure and bacteria picking out rate in 2 and 3 weeks. The wound closure at 3 weeks showed a significant difference in PRP group (P < 0.05). The healing rate of PRP group reached nearly 80% and made a breakthrough of 90% in 3 weeks, showing a significant difference compared with the control group (P < 0.05). Lyophilized PRP can be considered as an effective treatment to increase healing rate in patients with deep second-degree burn injury.

Restoration of skin pigmentation after deep partial or full-thickness burn injury.

Significant skin pigmentation changes occur when patients suffer deep burn injuries. These pigmentation disorders may cause not only cosmetic and psychological issues, but more importantly it increases the risk of skin cancer or photoaging. Severe burns significantly effect on the process of repigmentation as the pigmentation is tightly regulated by cell proliferation and differentiation of melanocytes and melanocyte stem cells which are housing in the epidermis and hair follicles of the skin. In the present review, we discuss the possible mechanisms to replenish the melanocytes from the healthy epidermis and hair follicles surrounding burn wounds. The molecular mechanisms of skin repigmentation following healing of burn injuries includes the differentiation of melanoblasts into melanocytes, the distribution and responses of melanocytes and melanocyte stem cells after burn injury, and the regulation of melanin production. We also reviewed advanced therapeutic strategies to treat pigmentation disorders, such as convectional surgery, laser, UV treatment and emerging concepts in skin tissue-engineering.

A Biodegradable Hemostatic Gelatin/Polycaprolactone Composite for Surgical Hemostasis.

Massive bleeding is the leading cause of battlefield-related deaths and the second leading cause of deaths in civilian trauma centers. One of the challenges of managing severe wounds is the need to promote hemostasis as quickly as possible, which can be achieved by using hemostatic dressings. In this study, we fabricated 2 kinds of gelatin/polycaprolactone composites with 2 ratios of gelatin/polycaprolactone, 1:1 and 2:1 (GP11 and GP21, respectively). Scanning electron microscopy revealed that the GP11 composite exhibited rougher and more porous structure than the GP21 composite did. Furthermore, both composites showed similar biocompatibility as that of tissue culture polystyrene. Moreover, both GP composites tended to show a gradual decrease in contact angle to zero within 40 minutes. The in vitro blood plasma coagulation assay revealed that the prothrombin time was significantly longer for the GP composites than it was for the Quikclot composite, whereas the activated partial thromboplastin time of the GP11 composite was significantly shorter than that of the gauze. Furthermore, the GP11 had the largest platelet adsorption of all the composites. The in vivo coagulation test showed an obvious shortening of the bleeding time with the Quikclot and GP21 compared with gauze sample. In conclusion, the GP composites showed superior biocompatibility and hemostasis to the gauze and comparable effects with the Qickclot composite. Therefore, the GP composites have the potential for development as biodegradable surgical hemostatic agents.

Probabilistic integrated risk assessment of human exposure risk to environmental bisphenol A pollution sources.

Environmental bisphenol A (BPA) exposure has been linked to a variety of adverse health effects such as developmental and reproductive issues. However, establishing a clear association between BPA and the likelihood of human health is complex yet fundamentally uncertain. The purpose of this study was to assess the potential exposure risks from environmental BPA among Chinese population based on five human health outcomes, namely immune response, uterotrophic assay, cardiovascular disease (CVD), diabetes, and behavior change. We addressed these health concerns by using a stochastic integrated risk assessment approach. The BPA dose-dependent likelihood of effects was reconstructed by a series of Hill models based on animal models or epidemiological data. We developed a physiologically based pharmacokinetic (PBPK) model that allows estimation of urinary BPA concentration from external exposures. Here we showed that the daily average exposure concentrations of BPA and urinary BPA estimates were consistent with the published data. We found that BPA exposures were less likely to pose significant risks for infants (0-1 year) and adults (male and female >20 years) with <10(-6)-fold increase in uterus weight and immune response outcomes, respectively. Moreover, our results indicated that there was 50 % risk probability that the response outcomes of CVD, diabetes, and behavior change with or without skin absorption would increase 10(-4)-10(-2)-fold. We conclude that our approach provides a powerful tool for tracking and managing human long-term BPA susceptibility in relation to multiple exposure pathways, and for informing the public of the negligible magnitude of environmental BPA pollution impacts on human health.

Evaluation of Wound Healing Efficacy of an Antimicrobial Spray Dressing at Skin Donor Sites.

INTRODUCTION: Autologous skin transplantation is a common treatment for patients with full-thickness burns. Postoperative wound care is essential for skin graft donor and recipient sites, but traditional wound dressings such as cotton and gauze do not form an effective barrier to bacteria, and patients can feel uncomfortable when replacing dressings. MATERIALS AND METHODS: The goal of this study was to evaluate the use of an antimicrobial spray dressing (JUC Spray Dressing, NMS Technologies Co Ltd, Nanjing, China), with respect to its antimicrobial efficiency and the degree of pain experienced by patients. RESULTS: The authors found the antimicrobial spray can reduce pain during the recovery period, while providing equivalent antibacterial protection to the control treatment (AQUACEL Hydrofiber Wound Dressing, ConvaTec, Bridgewater, NJ) based on skin culture tests. The spray did not adversely affect the wound site recovery. No significant side effects were present during the treatment period. CONCLUSION: This antimicrobial spray could potentially be used in wound dressing applications.

Fast isolation and expansion of multipotent cells from adipose tissue based on chitosan-selected primary culture.

Adipose-derived adult stem cells (ASCs) have gained much attention because of their multipotency and easy access. Here we describe a novel chitosan-based selection (CS) system instead of the conventional plastic adherence (PA) to obtain the primary ASCs. The minimal amount of adipose tissue for consistent isolation of ASCs is reduced from 10 mL to 5 mL. The selection is based on the specific interaction between cells and chitosan materials, which separate ASCs by forming spheroids during primary culture. The primary culture period was reduced from 4 days to one day and more ASCs (ten-fold expansion) were achieved in a week. The average duration for obtaining 1 × 10(7) cells takes about seven days from 5 mL of adipose tissue, compared to 14 days using the conventional PA method from 10 mL of adipose tissue. The replicative senescence of CS-ASCs is not evident until the fifteenth passage (vs. eighth for the PA-ASCs). The obtained ASCs (CS-ASCs) have less doubling time for the same passage of cells and show greater stemness than those obtained from the conventional PA method (PA-ASCs). Moreover, CS-ASCs undergo trilineage differentiation more effectively than PA-ASCs. The greater differentiation potential of CS-ASCs may be associated with the enrichment and maintenance of CD271 positive cells by chitosan selection of primary culture.

Histochemical and functional improvement of adipose-derived stem cell-based tissue-engineered cartilage by hyperbaric oxygen/air treatment in a rabbit articular defect model.

Cartilage is exposed to compression forces during joint loading. Therefore, exogenous stimuli are frequently used in cartilage tissue engineering strategies to enhance chondrocyte differentiation and extracellular matrix (ECM) secretion. In this study, human adipose-derived stem cells were seeded on a gelatin/polycaprolactone scaffold to evaluate the histochemical and functional improvement of tissue-engineered cartilage after hyperbaric oxygen/air treatment in a rabbit articular defect model. Behavior tests showed beneficial effects on weight-bearing and rear leg-supporting capacities after treatment of tissue-engineered cartilage with 2.5 ATA oxygen or air. Moreover, positron emission tomography images and immunohistochemistry staining demonstrated hydroxyapatite formation and increased ECM synthesis, respectively, at the tissue-engineered cartilage graft site after high pressure oxygen/air treatment. Based on these results, we concluded that hyperbaric oxygen and air treatment can improve the quality of tissue-engineered cartilage in vivo by increasing the synthesis of ECM.

The effects of microenvironment on wound healing by keratinocytes derived from mesenchymal stem cells.

Embryonic stem cells (ESCs) are pluripotent cells that can differentiate into various cell types, including keratinocyte-like cells, within suitable microniches. In this study, we aimed to investigate the effects of culture media, cell coculture, and a tissue-engineering biocomposite on the differentiation of mouse ESCs (MESCs) into keratinocyte-like cells and applied these cells to a surgical skin wound model. MESCs from BALB/c mice (ESC26GJ), which were transfected using pCX-EGFP expressing green fluorescence, were used to track MESC-derived keratinocytes. Weak expression of the keratinocyte early marker Cytokeratin 14 (CK-14) was observed up to 12 days when MESCs were cultured in a keratinocyte culture medium on tissue culture plastic and on a gelatin/collagen/polycaprolactone (GCP) biocomposite. MESCs cocultured with human keratinocyte cells (HKCs) also expressed CK-14, but did not express CK-14 when cocultured with human fibroblast cells (HFCs). Furthermore, CK-14 expression was observed when MESCs were cocultured by seeding HKCs or HFCs on the same or opposite side of the GCP biocomposite. The highest CK-14 expression was observed by seeding MESCs and HKCs on the same side of the GCP composite and with HFCs on the opposite side. To verify the effectiveness of wound healing in vivo, adipose-derived stem cells were applied to treat surgical wounds in nude mice. An obvious epidermis multilayer and better collagen deposition during wound healing were observed, as assessed by Masson staining. This study demonstrated the potential of keratinocyte-like differentiation from mesenchymal stem cells for use in promoting wound closure and skin regeneration.

Characterization and biocompatibility of chitosan nanocomposites.

Chitosan nanocomposites were prepared from chitosan and gold nanoparticles (AuNPs) or silver nanoparticles (AgNPs) of ∼5 nm size. Transmission electron microscopy (TEM) showed the NPs in chitosan did not aggregate until higher concentrations (120-240 ppm). Atomic force microscopy (AFM) demonstrated that the nanocrystalline domains on chitosan surface were more evident upon addition of AuNPs (60 ppm) or AgNPs (120 ppm). Both nanocomposites showed greater elastic modulus, higher glass transition temperature (T(g)) and better cell proliferation than the pristine chitosan. Additionally, chitosan-Ag nanocomposites had antibacterial ability against Staphylococcus aureus. The potential of chitosan-Au nanocomposites as hemostatic wound dressings was evaluated in animal (rat) studies. Chitosan-Au was found to promote the repair of skin wound and hemostasis of severed hepatic portal vein. This study indicated that a small amount of NPs could induce significant changes in the physicochemical properties of chitosan, which may increase its biocompatibility and potential in wound management.

Chondrogenesis from human placenta-derived mesenchymal stem cells in three-dimensional scaffolds for cartilage tissue engineering.

Human placenta-derived mesenchymal stem cells (hPMSCs) represent a promising source of stem cells. The application of hPMSCs in cartilage tissue engineering, however, was less reported. In this study, hPMSCs were grown in a three-dimensional (3D) environment for cartilage tissue formation in vitro. To select proper scaffolds for 3D culture of mesenchymal stem cells (MSCs), rat adipose-derived MSCs were initially employed to optimize the composition and condition of the 3D environment. The suitability of a poly(D,L-lactide-co-glycolide) (PLGA) precision scaffold previously developed for seeding and culture of primary chondrocytes was tested for MSCs. It was established that MSCs had to be embedded in alginate gel before seeded in the PLGA precision scaffold for cartilage-like tissue formation. The inclusion of nano-sized calcium-deficient hydroxyapatite (nCDHA) and/or a recombinant protein containing arginine-glycine-aspartate (RGD) into the alginate gel enhanced the chondrogenesis for both rat adipose-derived MSCs and hPMSCs. The amount of extracellular matrix such as glycosaminoglycan and type II collagen accumulated during a period of 21 days was found to be the greatest for hPMSCs embedded in the alginate/nCDHA/RGD gel and injected and cultivated in the precision scaffold. Also, histological analyses revealed the lacunae formation and extracellular matrix production from the seeded hPMSCs. Comparing human bone marrow-derived MSCs (hBMSCs) and hPMSCs grown in the previous composite scaffolds, the secretion of glycosaminoglycan was twice as higher for hPMSCs as that for hBMSCs. It was concluded that the alginate/nCDHA/RGD mixed gel in the aforementioned system could provide a 3D environment for the chondrogenesis of hPMSCs, and the PLGA precision scaffold could provide the dimensional stability of the whole construct. This study also suggested that hPMSCs, when grown in a suitable scaffold, may be a good source of stem cells for building up the tissue-engineered cartilage.

Sciatic nerve regeneration by microporous nerve conduits seeded with glial cell line-derived neurotrophic factor or brain-derived neurotrophic factor gene transfected neural stem cells.

Neurotrophic factors such as the glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) promote nerve cell survival and regeneration, but their efficacy in repairing a longer gap defect of rat sciatic nerve (15 mm) has not been established. In this study, two recombinant mammalian vectors containing either rat GDNF gene or BDNF gene were constructed and each was transfected into neural stem cells (NSCs). It was found that the transfection of GDNF or BDNF gene into NSCs led to significantly enhanced expression of GDNF or BDNF mRNA. The amount of GDNF or BDNF protein secreted from the transfected NSCs showed a 3.3-fold or 2.5-fold increase than that from nontransfected NSCs, respectively. The regeneration capacity of rat sciatic nerve in a poly(D,L-lactide) conduit seeded with GDNF or BDNF-transfected NSCs was evaluated by the histology, functional gait, and electrophysiology after 8 weeks of implantation. It was observed that the degree of myelination and the size of regenerated tissue in the conduits seeded with GDNF- and BDNF-transfected NSCs were higher than those seeded with the nontransfected NSCs. Conduits seeded with GDNF-transfected NSCs had the greatest number of blood vessels. The functional recovery assessed by the functional gait and electrophysiology was significantly improved for conduits seeded with GDNF or BDNF-transfected NSCs. It was concluded that the genetically modified NSCs may have potential applications in promoting nerve regeneration and functional recovery.

Antibacterial properties of silver nanoparticles in three different sizes and their nanocomposites with a new waterborne polyurethane.

Silver nanoparticles (AgNPs) are strong bactericidal agents but they are also cytotoxic. Embedding them in a polymer matrix may reduce their cytotoxic effect. In the present study, AgNPs in three average sizes were tested for their antibacterial activities and cytotoxicity. Nanocomposites from a new waterborne polyetherurethane (PEU) ionomer and AgNPs were prepared without the use of any crosslinker. It was observed that the antibacterial activity of AgNPs against Escherichia coli started at the effective concentration of 0.1-1 ppm, while that against Staphylococcus aureus started at higher concentrations of 1-10 ppm. Cytotoxicity of AgNPs was observed at the concentration of 10 ppm. AgNPs with smaller average size showed greater antibacterial activity as well as cytotoxicity. The PEU synthesized in this study showed high tensile strength, and the addition of AgNPs at all sizes further increased its thermal stability. The delicate surface features of nanophases, however, were only observed in nanocomposites with either small-or medium-sized AgNPs. PEU-Ag nanocomposites had a strong bacteriostatic effect on the growth of E. coli and S. aureus. The proliferation of endothelial cells on PEU-Ag nanocomposites was enhanced, whereas the platelet adhesion was reduced. The expression of endothelial nitric oxide synthase gene was upregulated on PEU-Ag containing small-sized AgNPs (30 ppm) or medium-sized AgNPs (60 ppm). This effect was not as remarkable in nanocomposites from large-sized AgNPs. Overall, nanocomposites from the PEU and 60 ppm of the medium-sized (5 nm) AgNPs showed the best biocompatibility and antibacterial activity. Addition of smaller or larger AgNPs did not produce as substantial an effect in PEU, especially for the larger AgNPs.

The effect of laser preexposure on seeding endothelial cells to a biomaterial surface.

OBJECTIVE: In this study, the possible effect of low-level laser (LLL) on improving the adhesion of endothelial cells (ECs) to a biomaterial substrate was evaluated. BACKGROUND DATA: Despite the numerous studies regarding the effects of LLL on biologic systems, the influence of LLL on the binding between cells and materials was rarely investigated. MATERIALS AND METHODS: A low-power He-Ne laser apparatus with a continuous wavelength of 632.8 nm (a maximum power output of 50 mW) was used. The average irradiation energy on cells was 1.18 J/cm(2). Cell morphology and the concentrations of nitric oxide and calcium after laser exposure were measured. Biomedical grade poly(carbonate)urethane (PU) was synthesized and used to prepare microporous vascular grafts. ECs exposed to laser were harvested and seeded on the PU grafts. No further exposure was given. RESULTS: LLL could change the morphology and increase the matrix secretion of ECs, and such effects persisted when preexposed cells were harvested and seeded to another substrate. The number of ECs attached on the biomaterial substrate was not affected. Preexposed ECs on the PU graft, however, were, on average, more resistant to flushing (i.e., greater cell retention). CONCLUSION: ECs were pretreated with LLL before being seeded onto the PU biomaterial vascular grafts. The retention of LLL-preexposed ECs on the graft surface was enhanced, but not as significantly as that of ECs preexposed to low-intensity ultrasound.