Laser-mediated fixation of collagen-based scaffolds to dermal wounds

In Vitro Feasibility Analysis of a New Sutureless Wound-Closure System Based on a Temperature-Regulated Laser and a Transparent Collagen Membrane for Laser Tissue Soldering (LTS)

For the post-surgical treatment of oral wounds and mucosal defects beyond a certain size, the gold standard is still an autologous skin or mucosal graft in combination with complex suturing techniques. A variety of techniques and biomaterials has been developed for sutureless wound closure including different tissue glues or collagen patches. However, no wound covering that enables for sutureless fixation has yet been introduced. Thus, a new system was developed that allows for sutureless wound covering including a transparent collagen membrane, which can be attached to the mucosa using a specially modified 2λ laser beam with integrated temperature sensors and serum albumin as bio-adhesive. The sutureless wound closure system was tested for its applicability and its cytocompatibility by an established in vitro model in the present study. The feasibility of the laser system was tested ex vivo on a porcine palate. The in vitro cytocompatibility tests excluded the potential release of toxic substances from the laser-irradiated collagen membrane and the bio-adhesive. The results of the ex vivo feasibility study using a porcine palate revealed satisfactory mean tensile strength of 1.2–1.5 N for the bonding of the membrane to the tissue fixed with laser of 980 nm. The results suggest that our newly developed laser-assisted wound closure system is a feasible approach and could be a first step on the way towards a laser based sutureless clinical application in tissue repair and oral surgery.

Light-Activated Tissue-Integrating Sutures as Surgical Nanodevices

Sutures are typically the primary means of soft tissue repair in surgery and trauma. Despite their widespread use, sutures do not result in immediate sealing of approximated tissues, which can result in bacterial infection and leakage. Nonabsorbable sutures and staples can be traumatic to tissue, and the trauma can be exacerbated by their subsequent removal. Use of cyanoacrylate glues is limited because of their brittleness and toxicity. In this work, laser-activated tissue-integrating sutures (LATIS) are described as novel nanodevices for soft tissue approximation and repair. Incorporation of gold nanorods within fibers generated from collagen result in LATIS fibers which demonstrate robust photothermal responses following irradiation with near infrared laser light. Compared to conventional sutures, LATIS fibers result in greater biomechanical recovery of incised skin in a mouse model of skin closure after spine surgeries. Histopathology analyses show improved repair of the epidermal gap in skin, which indicate faster tissue recovery using LATIS. The studies indicate that LATIS-facilitated approximation of skin in live mice synergizes the benefits of conventional suturing and laser-activated tissue integration, resulting in new approaches for faster sealing, tissue repair, and healing.

Non-invasive tracking of injected bone marrow mononuclear cells to injury and implanted biomaterials

Biomaterial scaffolds enhancing the engraftment of transplanted bone-marrow mononuclear cells (BM-MNC) have enormous potential for tissue regeneration applications. However, development of appropriate materials is challenging given the precise microenvironments required to support BM-MNC engraftment and function. In this study, we have developed a non-invasive, real-time tracking model of injected BM-MNC engraftment to wounds and implanted biomaterial scaffolds. BM-MNCs, encoded with firefly luciferase and enhanced GFP reporter genes, were tail vein injected into subcutaneously wounded mice. Luciferase-dependent cell bioluminescence curves revealed our injected BM-MNCs homed to and engrafted within subcutaneous wound sites over the course of 21days. Further immunohistochemical characterization showed that these engrafted cells drove functional changes by increasing the number of immune cells present at early time points and remodelling cell phenotypes at later time points. Using this model, we subcutaneously implanted electrospun polycaprolactone (PCL) and PCL/Collagen scaffolds, to determine differences in exogenous BM-MNC response to these materials. Following BM-MNC injection, immunohistochemical analysis revealed a high exogenous BM-MNC density around the periphery of PCL scaffolds consistent with a classical foreign body response. In contrast, transplanted BM-MNCs engrafted throughout PCL/Collagen scaffolds indicating an improved biological response. Importantly, these differences were closely correlated with the real-time bioluminescence curves, with PCL/Collagen scaffolds exhibiting a∼2-fold increase in maximum bioluminescence compared with PCL scaffolds. Collectively, these results demonstrate a new longitudinal cell tracking model that can non-invasively determine transplanted BM-MNC homing and engraftment to biomaterials, providing a valuable tool to inform the design scaffolds that help augment current BM-MNC tissue engineering strategies.

STATEMENT OF SIGNIFICANCE

Tracking the dynamic behaviour of transplanted bone-marrow mononuclear cells (BM-MNCs) is a long-standing research goal. Conventional methods involving contrast and tracer agents interfere with cellular function while also yielding false signals. The use of bioluminescence addresses these shortcomings while allowing for real-time non-invasive tracking in vivo. Given the failures of transplanted BM-MNCs to engraft into injured tissue, biomaterial scaffolds capable of attracting and enhancing BM-MNC engraftment at sites of injury are highly sought in numerous tissue engineering applications. To this end, the results from this study demonstrate a new longitudinal tracking model that can non-invasively determine exogenous BM-MNC homing and engraftment to biomaterials, providing a valuable tool to inform the design of scaffolds with implications for countless tissue engineering applications.

Ointment of Brassica oleracea var. capitata Matures the Extracellular Matrix in Skin Wounds of Wistar Rats

Wound healing is a complex process that aims to restore damaged tissue. Phytotherapeutics, such as cabbage, Brassica oleracea var. capitata (Brassicaceae), and sunflower, Helianthus annuus L. (Asteraceae) oil, are used as wound healers. Five circular wounds, each 12 mm in diameter, were made in the dorsolateral region of each rat. The animals were divided into four groups: balsam (B. oleracea); ointment (B. oleracea); sunflower oil (Helianthus annuus); control (saline solution 0.9%). These products were applied daily for 20 days and every four days the tissues of different wounds were removed. The wound contraction area, total collagen, types I and III collagen, glycosaminoglycans, and tissue cellularity were analyzed. In the groups that received ointment and balsam there was reduction in the wound area on days 4, 8, 12, and 20. Throughout the trial period, the balsam and ointment groups showed a higher amount of total collagen, type I collagen, and glycosaminoglycan compared to the others groups. The rats in the groups treated with B. oleracea var. capitata showed a higher number of cells on days 8, 16, and 20. B. oleracea was effective in stimulating the maturation of collagen and increasing the cellularity, as also in improving the mechanical resistance of the newly formed tissue.

Decellularized scaffolds containing hyaluronic acid and EGF for promoting the recovery of skin wounds

There is no effective therapy for the treatment of deep and large area skin wounds. Decellularized scaffolds can be prepared from animal tissues and represent a promising biomaterial for investigation in tissue regeneration studies. In this study, MTT assay showed that epidermal growth factor (EGF) increased NIH3T3 cell proliferation in a bell-shaped dose response, and the maximum cell proliferation was achieved at a concentration of 25 ng/ml. Decellularized scaffolds were prepared from pig peritoneum by a series of physical and chemical treatments. Hyaluronic acid (HA) increased EGF adsorption to the scaffolds. Decellularized scaffolds containing HA sustained the release of EGF compared to no HA. Rabbits contain relatively large skin surface and are less expensive and easy to be taken care, so that a rabbit wound healing model was use in this study. Four full-thickness skin wounds were created in each rabbit for evaluation of the effects of the scaffolds on the skin regeneration. Wounds covered with scaffolds containing either 1 or 3 μg/ml EGF were significantly smaller than with vaseline oil gauzes or with scaffolds alone, and the wounds covered with scaffolds containing 1 μg/ml EGF recovered best among all four wounds. Hematoxylin-Eosin staining confirmed these results by demonstrating that significantly thicker dermis layers were also observed in the wounds covered by the decellularized scaffolds containing HA and either 1 or 3 μg/ml EGF than with vaseline oil gauzes or with scaffolds alone. In addition, the scaffolds containing HA and 1 μg/ml EGF gave thicker dermis layers than HA and 3 μg/ml EGF and showed the regeneration of skin appendages on day 28 post-transplantation. These results demonstrated that decellularized scaffolds containing HA and EGF could provide a promising way for the treatment of human skin injuries.

The effect of laser diode irradiation on wound healing of rat skin

BACKGROUND

Light amplification by stimulated emission of radiation (LASER) diode irradiation (LDI) has some beneficial effects on the wound healing. However, little is known about the biochemical effect of LDI on wound healing. We have performed animal study to clarify the effect of LDI on wound healing based on microscopic findings.

METHODS

Eight-month-old male rats (NTacSam:SD, SamtakoBioKorea), weighting 250-300 g, were used. Round blade, of 1 cm diameter, was penetrated through the skin and subcutaneous level after elevating the skin just above the thoracic spine of the rats. Laser diode of 655, 785, and 850 nm wavelengths were irradiated to the skin wound for 9 days, 20 min a day. Eight rats were used in each four groups including non-irradiated group. Immunochemical staining was carried out to evaluate pan-cytokeratin and actin, and Masson's trichrome staining was carried to evaluate the cellular and protein components relating to wound healing. Wound size was measured on 9th postoperative day with computer system.

RESULT

Collagen formation was graded as 2+, 3+, and 4 + in the order of non-radiation group, 655, 785, and 850 nm irradiation groups, respectively. Myofibroblast was formed more abundantly in LDI group than in non-irradiated group. The mean values of proliferating cell nuclear antigen (PCNA) were 67.8 ± 5.0, 84.0 ± 4.6, 78.0 ± 6.8, and 74.2 ± 4.0 nm in the order of non-radiation group, 655, 785, and 850 nm irradiation groups, respectively. Mean values of defect size were 2,840 ± 124 um, 1,689 ± 125 um, 1,254 ± 94 um, and 1,423 ± 113 in the order of non-radiation group, 65, 785, and 850 nm groups, respectively.

CONCLUSION

LDI has beneficial effects on the formation of fibroblast and collagen, and results in better wound healing.

Comparative study of the effects of laser photobiomodulation and extract of Brassica oleracea on skin wounds in wistar rats: A histomorphometric study

The objective of this study was to investigate the effect of a photobiomodulation laser and Brassica oleracea on tissue morphology in skin wounds. The parameters analyzed were type I and III collagen fibers, and thickness and surface density of the epithelial tissue, as well as how quickly the wound closed. Five skin wounds 12mm in diameter were made on the backs of the animals, which were randomized into four groups (8 animals each). Saline Group: 0.9% saline solution; Ointment Group (extract of Cabbage, B. oleracea, 10% lanolin); Balsam Group (10% glycolic extract of B. oleracea emulsion oil); L60 Group (laser GaAsAl 60J/cm(2)). The applications were made daily during a 20-day treatment, and every 4 days tissue from different wounds was removed. The reduction in the size of the wounds on the 4th, 8th, 12th and 16th days was significantly greater in the treated groups compared to the control group. At all the time points analyzed, there was a greater proportion of collagen in the Balsam and L60 groups (p<0.05). There was also a greater proliferation of epithelial cells in the L60 and Balsam groups after 20 days of treatment (p<0.05). The healing extract and laser 60j/cm(2) exerted a great effect on collagen proliferation in stimulating scar tissue maturation.

Development of ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffolds for accelerated healing of full-thickness wounds

Silk sericin has been recently reported for its advantageous biological properties to promote wound healing. In this study, we established that the ethyl alcohol (EtOH) could be used to precipitate sericin and form the stable sericin/polyvinyl alcohol (PVA) scaffolds without the crosslinking. The sericin/PVA scaffolds were fabricated via freeze-drying and subsequently precipitating in various concentrations of EtOH. The EtOH-precipitated sericin/PVA scaffolds showed denser structure, higher compressive modulus, but lower water swelling ability than the non-precipitated scaffolds. Sericin could be released from the EtOH-precipitated sericin/PVA scaffolds in a sustained manner. After cultured with L929 mouse fibroblasts, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed the highest potential to promote cell proliferation. After applied to the full-thickness wounds of rats, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed significantly higher percentage of wound size reduction and higher extent of type III collagen formation and epithelialization, compared with the control scaffolds without sericin. The accelerated wound healing by the 70 vol% EtOH-precipitated sericin/PVA scaffolds was possibly due to (1) the bioactivity of sericin itself to promote wound healing, (2) the sustained release of precipitated sericin from the scaffolds, and (3) the activation and recruitment of wound healing-macrophages by sericin to the wounds. This finding suggested that the EtOH-precipitated sericin/PVA scaffolds were more effective for the wound healing, comparing with the EtOH-precipitated PVA scaffolds without sericin.