Improvement of dermal burn healing by combining sodium alginate/chitosan-based films and low level laser therapy

Release of insulin from PLGA-alginate dressing stimulates regenerative healing of burn wounds in rats

Burn wound healing involves a complex set of overlapping processes in an environment conducive to ischaemia, inflammation and infection costing $7.5 billion/year in the U.S.A. alone, in addition to the morbidity and mortality that occur when the burns are extensive. We previously showed that insulin, when topically applied to skin excision wounds, accelerates re-epithelialization and stimulates angiogenesis. More recently, we developed an alginate sponge dressing (ASD) containing insulin encapsulated in PLGA [poly(D,L-lactic-co-glycolic acid)] microparticles that provides a sustained release of bioactive insulin for >20 days in a moist and protective environment. We hypothesized that insulin-containing ASD accelerates burn healing and stimulates a more regenerative, less scarring healing. Using heat-induced burn injury in rats, we show that burns treated with dressings containing 0.04 mg insulin/cm(2) every 3 days for 9 days have faster closure, a higher rate of disintegration of dead tissue and decreased oxidative stress. In addition, in insulin-treated wounds, the pattern of neutrophil inflammatory response suggests faster clearing of the burned dead tissue. We also observe faster resolution of the pro-inflammatory macrophages. We also found that insulin stimulates collagen deposition and maturation with the fibres organized more like a basket weave (normal skin) than aligned and cross-linked (scar tissue). In summary, application of ASD-containing insulin-loaded PLGA particles on burns every 3 days stimulates faster and more regenerative healing. These results suggest insulin as a potential therapeutic agent in burn healing and, because of its long history of safe use in humans, insulin could become one of the treatments of choice when repair and regeneration are critical for proper tissue function.

Smart Dressings Based on Nanostructured Fibers Containing Natural Origin Antimicrobial, Anti-Inflammatory, and Regenerative Compounds

A fast and effective wound healing process would substantially decrease medical costs, wound care supplies, and hospitalization significantly improving the patients' quality of life. The search for effective therapeutic approaches seems to be imperative in order to avoid the aggravation of chronic wounds. In spite of all the efforts that have been made during the recent years towards the development of artificial wound dressings, none of the currently available options combine all the requirements necessary for quick and optimal cutaneous regeneration. Therefore, technological advances in the area of temporary and permanent smart dressings for wound care are required. The development of nanoscience and nanotechnology can improve the materials and designs used in topical wound care in order to efficiently release antimicrobial, anti-inflammatory and regenerative compounds speeding up the endogenous healing process. Nanostructured dressings can overcome the limitations of the current coverings and, separately, natural origin components can also overcome the drawbacks of current antibiotics and antiseptics (mainly cytotoxicity, antibiotic resistance, and allergies). The combination of natural origin components with demonstrated antibiotic, regenerative, or anti-inflammatory properties together with nanostructured materials is a promising approach to fulfil all the requirements needed for the next generation of bioactive wound dressings. Microbially compromised wounds have been treated with different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring antimicrobial, anti-inflammatory, and regenerative components but the available evidence is limited and insufficient to be able to draw reliable conclusions and to extrapolate those findings to the clinical practice. The evidence and some promising preliminary results indicate that future comparative studies are justified but instead of talking about the beneficial or inert effects of those natural origin occurring materials, the scientific community leads towards the identification of the main active components involved and their mechanism of action during the corresponding healing, antimicrobial, or regenerative processes and in carrying out systematic and comparative controlled tests. Once those natural origin components have been identified and their efficacy validated through solid clinical trials, their combination within nanostructured dressings can open up new avenues in the fabrication of bioactive dressings with outstanding characteristics for wound care. The motivation of this work is to analyze the state of the art in the use of different essential oils, honey, cationic peptides, aloe vera, plant extracts, and other natural origin occurring materials as antimicrobial, anti-inflammatory and regenerative components with the aim of clarifying their potential clinical use in bioactive dressings. We conclude that, for those natural occurring materials, more clinical trials are needed to reach a sufficient level of evidence as therapeutic agents for wound healing management.

Alginate hydrogels coated with chitosan for wound dressing

In this work, a coating of chitosan onto alginate hydrogels was realized using the water-soluble hydrochloride form of chitosan (CH-Cl), with the dual purpose of imparting antibacterial activity and delaying the release of hydrophilic molecules from the alginate matrix. Alginate hydrogels with different calcium contents were prepared by the internal setting method and coated by immersion in a CH-Cl solution. Structural analysis by cryo-scanning electron microscopy was carried out to highlight morphological alterations due to the coating layer. Tests in vitro with human mesenchymal stromal cells (MSC) were assessed to check the absence of toxicity of CH-Cl. Swelling, stability in physiological solution and release characteristics using rhodamine B as the hydrophilic model drug were compared to those of relative uncoated hydrogels. Finally, antibacterial activity against Escherichia coli was tested. Results show that alginate hydrogels coated with chitosan hydrochloride described here can be proposed as a novel medicated dressing by associating intrinsic antimicrobial activity with improved sustained release characteristics.

Thymosin β4 has a major role in dermal burn wound healing that involves actin cytoskeletal remodelling via heat-shock protein 70

Rapid vascular remodelling of damaged dermal tissue is required to heal burn wounds. Thymosin β4 (Tβ4) is a growth factor that has been shown to promote angiogenesis and dermal wound repair. However, the underlying mechanisms based on Tβ4 function have not yet been fully investigated. In the present study, we investigated how Tβ4 improves dermal burn wound healing via actin cytoskeletal remodelling and the action of heat-shock proteins (HSPs), which are a vital set of chaperone proteins that respond to heat shock. Our in vitro results achieved with the use of human umbilical vein endothelial cells (HUVECs) revealed a possible signal between Tβ4 and HSP70. Moreover, we confirmed that remodelling of filamentous actin (F-actin) was regulated by Tβ4-induced HSP70 in HUVECs. Based on these in vitro results, we confirmed the healing effects of Tβ4 in an adapted dermal burn wound in vivo model. Tβ4 improved wound-healing markers, such as wound closure and vascularization. Moreover, Tβ4 maintained the long-term expression of HSP70, which is associated with F-actin regulation during the wound-healing period. These results suggest that an association between Tβ4 and HSP70 is responsible for the healing of burn wounds, and that this association may regulate F-actin remodelling. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of red laser, infrared, photodynamic therapy, and green LED on the healing process of third-degree burns: clinical and histological study in rats

The aim of this study was to evaluate the effects of red laser, infrared, photodynamic therapy, and green light-emitting diode (LED) on the healing process of skin burns through clinical and histopathologic analysis in rats. For this, 100 animals were randomly divided into five groups: G1-untreated control (CTR), G2-red laser (LVER), G3-infrared (LINF), G4-photodynamic therapy (PDT), and G5-green LED. Burn was induced on the dorsum of the rat and the treatment of the experimental groups was red light (10 J/cm(2), 10 s, 40 mW, and λ660 nm), infrared (10 J/cm(2), 10 s, 40 mW, and λ780 nm), green LED irradiation (60 J/cm(2), 10 s, λ520, and 550 nm), and photodynamic therapy (10 J/cm(2), 40 mW, and λ660 nm), the latter combined with methylene blue photosensitizer at concentration 0.5 μg/mL. Applications were performed daily until day prior to sacrifice of the animal at 3, 7, 14, and 21 days with intraperitoneal anesthetic overdose. The specimens collected were clinically examined and soon after processed and stained with hematoxylin-eosin and Picrosirius for analysis under light and polarized light microscopy, respectively. Animals treated with LVER, LINF, PDT (p < 0.001), and LED (p < 0.05) stimulated production and maturation of collagen, and increased the consumption of food and water compared to the CTR (p < 0.001). Laser λ660 nm and λ780 nm showed the largest wound reductions in all groups (p = 0.001). In conclusion, red laser, infrared, photodynamic therapy, and green LED favored the healing process of third-degree burns in rats.

Effect of laser therapy on the inflammatory response induced by endodontic medications implanted into the subcutaneous tissue of rats

INTRODUCTION: Endodontic medications contain toxic components that cause varying degrees of inflammation.OBJECTIVE: This study evaluated the effect of laser therapy on the inflammatory response induced by intracanal medications implanted into the subcutaneous tissue of rats using a quantitative analysis of mast cells.MATERIAL AND METHOD: Polyethylene tubes containing the medications were implanted in the dorsum of 60 rats divided into six groups, including HS (P.A. calcium hydroxide paste), HL (P.A. calcium hydroxide paste and laser therapy), HPS (P.A. calcium hydroxide paste with camphorated paramonochlorophenol), HPL (P.A. calcium hydroxide paste with camphorated paramonochlorophenol and laser therapy), IS (iodoform with saline) and IL (iodoform with saline and laser therapy). The animals were euthanized eight or fifteen days after surgery, and samples were removed and embedded in paraffin. Histological sections were stained with 0.2% toluidine blue for the quantification of mast cells. Analysis of variance (ANOVA) and Tukey's post-hoc test were applied to determine significant differences in the number of mast cells between groups (p<0.05).RESULT: There was a decrease in mast cells for the HL, HPL and IL groups when compared with the HS, HPS and IS groups at both time points. There was no statistically significant difference between the HPS and HPL groups at the eight-day time point.CONCLUSION: Laser therapy was effective at modulating the inflammatory response induced by endodontic medications by significantly reducing the number of mast cells.

Evaluating the effect of low-level laser therapy on healing of tentomized Achilles tendon in streptozotocin-induced diabetic rats by light microscopical and gene expression examinations

Tendon healing is impaired in individuals diagnosed with diabetes mellitus (DM). According to research, there is considerable improvement in the healing of surgically tenotomized Achilles tendons following low-level laser therapy (LLLT) in non-diabetic, healthy animals. This study uses light microscopic (LM) and semi-quantitative reverse transcription PCR (RT-PCR) analyses to evaluate the ability of LLLT in healing Achilles tendons from streptozotocin-induced diabetic (STZ-D) rats. A total of 88 rats were randomly divided into two groups, non-diabetic and diabetic. DM was induced in the rats by injections of STZ. The right Achilles tendons of all rats were tenotomized 1 month after administration of STZ. Laser-treated rats were treated with a helium-neon (He-Ne) laser that had a 632.8-nm wavelength and 7.2-mW average power. Experimental group rats received a daily dose of 0.014 J (energy density, 2.9 J/cm(2)). Control rats did not receive LLLT. Animals were sacrificed on days 5, 10, and 15 post-operatively for semi-quantitative LM and semi-quantitative RT-PCR examinations of transforming growth factor-beta1 (TGF-β1) gene expression. The chi-square test showed that LLLT significantly reduced inflammation in non-diabetic rats compared with their non-diabetic controls (p = 0.02). LLLT significantly decreased inflammation in diabetic rats on days 5 (p = 0.03) and 10 (p = 0.02) compared to the corresponding control diabetic rats. According to the student's t test, LLLT significantly increased TGF-β1 gene expression in healthy (p = 0.000) and diabetic (p = 0.000) rats compared to their relevant controls. The He-Ne laser was effective in altering the inflammatory reaction and increasing TGF-β1 gene production.

Polymeric films loaded with vitamin E and aloe vera for topical application in the treatment of burn wounds

Burns are serious traumas related to skin damage, causing extreme pain and possibly death. Natural drugs such as Aloe vera and vitamin E have been demonstrated to be beneficial in formulations for wound healing. The aim of this work is to develop and evaluate polymeric films containing Aloe vera and vitamin E to treat wounds caused by burns. Polymeric films containing different quantities of sodium alginate and polyvinyl alcohol (PVA) were characterized for their mechanical properties and drug release. The polymeric films, which were produced, were thin, flexible, resistant, and suitable for application on damaged skin, such as in burn wounds. Around 30% of vitamin E acetate was released from the polymeric films within 12 hours. The in vivo experiments with tape stripping indicated an effective accumulation in the stratum corneum when compared to a commercial cream containing the same quantity of vitamin E acetate. Vitamin E acetate was found in higher quantities in the deep layers of the stratum corneum when the film formulation was applied. The results obtained show that the bioadhesive films containing vitamin E acetate and Aloe vera could be an innovative therapeutic system for the treatment of burns.

Natural and synthetic polymers for wounds and burns dressing

In the last years, health care professionals faced with an increasing number of patients suffering from wounds and burns difficult to treat and heal. During the wound healing process, the dressing protects the injury and contributes to the recovery of dermal and epidermal tissues. Because their biocompatibility, biodegradability and similarity to macromolecules recognized by the human body, some natural polymers such as polysaccharides (alginates, chitin, chitosan, heparin, chondroitin), proteoglycans and proteins (collagen, gelatin, fibrin, keratin, silk fibroin, eggshell membrane) are extensively used in wounds and burns management. Obtained by electrospinning technique, some synthetic polymers like biomimetic extracellular matrix micro/nanoscale fibers based on polyglycolic acid, polylactic acid, polyacrylic acid, poly-ɛ-caprolactone, polyvinylpyrrolidone, polyvinyl alcohol, polyethylene glycol, exhibit in vivo and in vitro wound healing properties and enhance re-epithelialization. They provide an optimal microenvironment for cell proliferation, migration and differentiation, due to their biocompatibility, biodegradability, peculiar structure and good mechanical properties. Thus, synthetic polymers are used also in regenerative medicine for cartilage, bone, vascular, nerve and ligament repair and restoration. Biocompatible with fibroblasts and keratinocytes, tissue engineered skin is indicated for regeneration and remodeling of human epidermis and wound healing improving the treatment of severe skin defects or partial-thickness burn injuries.

Evaluation of skin regeneration after burns in vivo and rescue of cells after thermal stress in vitro following treatment with a keratin biomaterial

Thermal burns typically display an injury pattern dictated by the transfer of the thermal energy into the skin and underlying tissues and creation of three zones of injury represented by a necrotic zone of disrupted cells and tissue, an intermediate zone of injured and dying cells, and a distant zone of stressed cells that will recover with proper treatment. The wound healing capabilities of a keratin biomaterial hydrogel were studied in two pilot studies, one using a chemical burn model in mice and the other a thermal burn model in swine. In both studies, keratin was shown to prevent enlargement of the initial wound area and promote faster wound closure. Interestingly, treating thermally stressed dermal fibroblast in culture demonstrated that soluble keratin was able to maintain cell viability and promote proliferation. Separation of so-called alpha and gamma fractions of the keratin biomaterial had differential effects, with the gamma fraction producing more pronounced cell survival and recovery. These results suggest that the gamma fraction, composed essentially of degraded alpha keratin proteins, may facilitate cell rescue after thermal injury. Treatment of burns with gamma keratin may therefore represent a potential therapy for wounds with an intermediate zone of damaged tissue that has the potential to contribute to spontaneous healing.

All-natural composite wound dressing films of essential oils encapsulated in sodium alginate with antimicrobial properties

We present natural polymeric composite films made of essential oils (EOs) dispersed in sodium alginate (NaAlg) matrix, with remarkable anti-microbial and anti-fungal properties. Namely, elicriso italic, chamomile blue, cinnamon, lavender, tea tree, peppermint, eucalyptus, lemongrass and lemon oils were encapsulated in the films as potential active substances. Glycerol was used to induce plasticity and surfactants were added to improve the dispersion of EOs in the NaAlg matrix. The topography, chemical composition, mechanical properties, and humidity resistance of the films are presented analytically. Antimicrobial tests were conducted on films containing different percentages of EOs against Escherichia coli bacteria and Candida albicans fungi, and the films were characterized as effective or not. Such diverse types of essential oil-fortified alginate films can find many applications mainly as disposable wound dressings but also in food packaging, medical device protection and disinfection, and indoor air quality improvement materials, to name a few.

Evaluation of anti-nociceptive and anti-inflammatory activity of low-level laser therapy on temporomandibular joint inflammation in rodents

The aim of this study was to investigate the analgesic and anti-inflammatory activity of low-level laser therapy (LLLT) on the nociceptive behavioral as well as histomorphological aspects induced by injection of formalin and carrageenan into the rat temporomandibular joint. The 2.5% formalin injection (FRG group) induced behavioral responses characterized by rubbing the orofacial region and flinching the head quickly, which were quantified for 45 min. The pretreatment with systemic administration of diclofenac sodium-DFN group (10 mg/kg i.p.) as well as the irradiation with LLLT infrared (LST group, 780 nm, 70 mW, 30 s, 2.1 J, 52.5 J/cm(2), GaAlAs) significantly reduced the formalin-induced nociceptive responses. The 1% carrageenan injection (CRG group) induced inflammatory responses over the time-course of the study (24 h, and 3 and 7 days) characterized by the presence of intense inflammatory infiltrate rich in neutrophils, scanty areas of liquefactive necrosis and intense interstitial edema, extensive hemorrhagic areas, and enlargement of the joint space on the region. The DFN and LST groups showed an intensity of inflammatory response that was significantly lower than in CRG group over the time-course of the study, especially in the LST group, which showed exuberant granulation tissue with intense vascularization, and deposition of newly formed collagen fibers (3 and 7 days). It was concluded that the LLLT presented an anti-nociceptive and anti-inflammatory response on the inflammation induced in the temporomandibular joint of rodents.

Potentiated anti-inflammatory effect of combined 780 nm and 660 nm low level laser therapy on the experimental laryngitis

Reflux laryngitis is a common clinic complication of nasogastric intubation (NSGI). Since there is no report concerning the effects of low level laser therapy (LLLT) on reflux laryngitis, this study aimed to analyze the protective effect of single and combined therapies with low level laser at the doses of 2.1J and 2.1+1.2 J with a total irradiation time of 30s and 30+30 s, respectively, on a model of neurogenic reflux laryngitis. NSGI was performed in Wistar rats, assigned into groups: NGI (no treatment), NLT17.5 (single therapy), and NLT17.5/10.0 (combined therapy, applied sequentially). Additional non-intubated and non-irradiated rats were use as controls (CTR). Myeloperoxidase (MPO) activity was assessed by colorimetric method after the intubation period (on days 1, 3, 5, and 7), whereas paraffin-embedded laryngeal specimens were used to carry out histopathological analysis of the inflammatory response, granulation tissue, and collagen deposition 7 days after NSGI. Significant reduction in MPO activity (p<0.05) and in the severity of the inflammatory response (p<0.05), and improvement in the granulation tissue (p<0.05) was observed in NLT17.5/10.0 group. Mast cells count was significantly decreased in NGI and NLT17.5 groups (p<0.001), whereas no difference was observed between NLT17.5/10.0 and CTR groups (p>0.05). NLT17.5/10.0 group also showed better collagenization pattern, in comparison to NGI and NLT17.5 groups. This study suggests that the combined therapy successfully modulated the inflammatory response and collagenization in experimental model of NSGI-induced neurogenic laryngitis.

Anti-inflammatory and cicatrizing activities of thymol, a monoterpene of the essential oil from Lippia gracilis, in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Lippia gracilis Schauer (Verbenaceae) has long been recognized in folk medicine as a medicinal plant. The essential oil of Lippia gracilis has antimicrobial activity and is used externally to treat cutaneous diseases, burns, wounds, and ulcers. Recently, our research group demonstrated that the essential oil of Lippia gracilis leaves possesses antinociceptive and anti-inflammatory actions and its major component identified was thymol. The objective of this study was to assess the anti-inflammatory and wound healing activities of thymol in rodents.

MATERIALS AND METHODS

For the anti-inflammatory analysis the paw oedema and peritonitis models were used, followed by the assessment of the mieloperoxidase (MPO) activity, total cell counting, and histological analysis. The animals were treated (i.p., n=6/group) with thymol (10, 30, and 100 mg/kg), dexamethasone (2 mg/kg), or vehicle (1% Tween 80). In order to assess the wound healing potential, thymol was vehiculated into collagen-based dressing films and a biological wound healing test was conducted. The retraction index of the wounds and histological analysis were performed on the 3rd, 7th, 14th, and 21th days, split into three groups: undressed wounds (CTR), dressed with collagen-based films (COL), and dressed with collagen-based containing thymol (COLTHY) films.

RESULTS

Thymol reduced significantly the oedema (100 mg/kg, P<0.001) and, besides, diminished the influx of leukocytes to the injured area (10, 30, and 100 mg/kg), according to the assessment of MPO activity (P<0.001), total cell count (P<0.05), and histological analysis. Wounds dressed with COLTHY films showed significantly bigger wound retraction rates (7 and 14 day, P<0.05) and improved the granulation reaction, as well provided better collagenization density and arrangement during wound healing.

CONCLUSIONS

This study suggests that thymol is a promising compound to be used in treatment of inflammatory processes as well as wound healing. The pharmacological actions of Lippia gracilis in popular medicine practices may be related, at least in part, to the presence of thymol in the essential oil.