Recent developments in novel drug delivery systems for wound healing

Introduction: Complete regeneration and restoration of the skin’s structure and function with no or minimal scarring remains the goal of wound healing research. Novel pharmaceutical carriers have the potential to deliver wound healing drugs such as antibiotics, antimicrobials, human EGFs, and so on. Thus, offering a potential platform to overcome the limitations of conventional wound dressings.

Areas covered: This review will describe various techniques such as microspheres, nanoparticles, liposomes, solid lipid nanoparticles, nano and microemulsions, sponges and wafers, and so on, that are successfully applied as carriers for wound healing drugs. Results of various studies including in vitro and in vivo experiments are also discussed.

Expert opinion: Controlled and localized delivery of wound healing drugs to the wounds is more convenient than systemic administration as higher concentrations of the medication are delivered directly to the desired area in a sustained manner. They are also capable of providing optimum environmental conditions to facilitate wound healing while eliminating the need for frequent changes of dressings. As the number of people suffering from chronic wounds is increasing around the world, controlled delivery of wound healing agents have enormous potential for patient-friendly wound management.     

Hyaluronic acid and chitosan-based nanosystems: a new dressing generation for wound care

ABSTRACT

Introduction: The main goal in the management of chronic wounds is the development of multifunctional dressings able to promote a rapid recovery of skin structure and function, improving patient compliance.

Areas covered: This review discusses the use of nanosystems, based on hyaluronic acid and chitosan or their derivatives for the local treatment of chronic wounds. The bioactive properties of both polysaccharides will be described, as well as the results obtained in the last decade by the in vitro and in vivo evaluation of the wound healing properties of nanosystems based on such polymers.

Expert opinion: In the last decades, there has been a progressive change in the local treatments of chronic wounds: traditional inert dressings have been replaced by more effective bioactive ones, based on biopolymers taking part in wound healing and able to release the loaded active agents in a controlled way. With the advance of nanotechnologies, the scenario has further changed: nanosystems, characterized by a large area-to-volume ratio, show an improved interaction with the biological substrates, amplifying the activity of the constituent biopolymers. In the coming years, a deeper insight into wound healing mechanisms and the development of new techniques for nanosystem manufacturing will results in the design of new scaffolds with improved performance.     

Bilayer hydrogel dressing with lysozyme-enhanced photothermal therapy for biofilm eradication and accelerated chronic wound repair

Biofilms are closely associated with the tough healing and dysfunctional inflammation of chronic wounds. Photothermal therapy (PTT) emerged as a suitable alternative which could destroy the structure of biofilms with local physical heat. However, the efficacy of PTT is limited because the excessive hyperthermia could damage surrounding tissues. Besides, the difficult reserve and delivery of photothermal agents makes PTT hard to eradicate biofilms as expectation. Herein, we present a GelMA-EGF/Gelatin-MPDA-LZM bilayer hydrogel dressing to perform lysozyme-enhanced PTT for biofilms eradication and a further acceleration to the repair of chronic wounds. Gelatin was used as inner layer hydrogel to reserve lysozyme (LZM) loaded mesoporous polydopamine (MPDA) (MPDA-LZM) nanoparticles, which could rapidly liquefy while temperature rising so as to achieve a bulk release of nanoparticles. MPDA-LZM nanoparticles serve as photothermal agents with antibacterial capability, could deeply penetrate and destroy biofilms. In addition, the outer layer hydrogel consisted of gelatin methacryloyl (GelMA) and epidermal growth factor (EGF) promoted wound healing and tissue regeneration. It displayed remarkable efficacy on alleviating infection and accelerating wound healing in vivo. Overall, the innovative therapeutic strategy we came up with has significant effect on biofilms eradication and shows promising application in promoting the repair of clinical chronic wounds.     

Metronidazole and Pentoxifylline films for the local treatment of chronic periodontal pockets: preparation,in vitro evaluation and clinical assessment

Objective: Periodontitis is one of the most important chronic inflammatory dental diseases arising from the destructive actions caused by a variety of pathogenic organisms presented in the oral cavity. The aim of this study is the preparation and in vitro evaluation of films for the local treatment of periodontal pockets.

Methods: The prepared films contained either metronidazole (Mtr), for its antimicrobial effect in periodontal diseases, using a mixture of polymers namely hydroxypropyl methyl cellulose, Carbopol 934 or locally applied Pentoxifylline (PTX), for its anti-inflammatory activity, using chitosan. All films were prepared using solvent casting technique and were evaluated for their physical characteristics, drug content uniformity, surface pH, swelling behavior, mechanical properties and in vitro release. Further characterization was done on the selected formulations using differential scanning calorimetry and scanning electron microscopy for surface structure. Clinical evaluation tests were also performed.

Result: Appropriate physical characteristics and mechanical properties for most formulations and their suitability for periodontal application were observed. In vitro drug release from most films showed a burst release rate for both Mtr and PTX during the first 2 h after which the release rate was markedly decreased. Clinical trials on patients revealed the advantageous use of Mtr and PTX as an adjunct treatment with traditionally used dental techniques.

Conclusion: The effectiveness of the co-therapy of either drug could add benefit in the eradication of chronic periodontal hazards.     

Could rusalatide acetate be the future drug of choice for diabetic foot ulcers and fracture repair?

Rusalatide acetate (Chrysalin^®) is an investigational drug being evaluated for treatment of chronic wounds and fractures. Rusalatide acetate interacts with cell surface receptors to stimulate a cascade of cellular and molecular wound healing events, including activation of nitric oxide signaling. Rusalatide acetate significantly accelerated healing of diabetic foot ulcers and distal radius fractures in Phase I/II clinical trials. Subsequently, in one of the largest Phase III fracture studies to date, rusalatide acetate showed significant acceleration of distal radius fracture healing radiographically but failed to meet its primary clinical endpoint – time to removal of immobilization – within the intent-to-treat population. Subset analysis showed that rusalatide acetate met this primary clinical endpoint and significantly accelerated radiographic healing in osteopenic women. Rusalatide acetate may therefore show its greatest efficacy in healing-impaired patients.     

OM‐LV20, a novel peptide from odorous frog skin,accelerates wound healing in vitro and in vivo

The healing of chronic wounds remains a considerable challenge in clinical trials and imposes severe financial and physiological burdens on patients. Many works are being tried to find ideal clinical promoting wound healing biomaterials. Small bioactive peptides with low cost and easy production, store and transfer become excellent candidates. Here, we identified a novel peptide (named OM‐LV20) from skin secretions of odorous frog Odorrana margaretae. The peptide had an amino acid sequence of “LVGKLLKGAVGDVCGLLPIC,” contained an intramolecular disulfide bridge at the C‐terminus, and was produced by post‐translational processing of a 71‐residue prepropeptide. Our results showed that OM‐LV20 had no direct microbe‐killing effects, hemolytic activity, or acute toxicity, but did exhibit weak antioxidant activity. OM‐LV20 promoted wound healing against human keratinocytes (HaCaT) and human skin fibroblasts (HSF) in both time‐ and dose‐dependent manners. In addition, it induced the proliferation of HaCaT but not HSF cells. Of note, OM‐LV20 showed strong wound healing‐promoting activity in a mice model of full‐thickness skin wound. Our research indicates the cellular and animal level wound healing potential of OM‐LV20, and thus provides a novel bioactive peptide template for the development of wound healing agents and medicine.     

三维重组皮肤模型在体外替代遗传毒性评价中的应用

三维（3D）重组皮肤模型已证实在模拟体内代谢条件、给药浓度及反应靶器官毒性特点方面具有突出优势。近年来已有多家公司构建3D重组人工皮肤模型,且一些制药公司已将3D细胞模型应用于药物的早期毒性筛选。我国动物实验替代方法的研究仍处于起步阶段,利用3D重组皮肤模型进行体外安全性评价成为目前替代方法的研究热点之一。综述人3D重组皮肤模型在遗传毒性评价中体外微核试验和彗星试验的研究进展,并对该模型在外用药物体外替代遗传毒性评价中的应用前景进行探讨。     

Evaluation of a tiered in vitro testing strategy for assessing the ocular and dermal irritation/corrosion potential of pharmaceutical compounds for worker safety

Introduction: Irritation reactions are a frequently reported occupational illness. The potential adverse effects of pharmaceutical compounds (PCs) on eye and skin can now be assessed using validated in vitro methods.

Objectives: Our overall aim is to reduce animal testing by replacing the historically utilized in vivo test methods with validated in vitro test methods which accurately determine the ocular and dermal irritation/corrosion potential of PCs to inform worker safety within the pharmaceutical space. Bristol–Myers Squibb (BMS) and the Institute for In Vitro Sciences (IIVS) have therefore conceptualized and internally qualified a tiered in vitro testing strategy to inform occupational hazards regarding eye and skin irritation and corrosivity of PCs. For the small scale pre-qualification phase, we paired historical in vivo and newly generated in vitro data for 15 PCs to determine the predictive capacity of in vitro assays already validated for the eye and skin irritation/corrosion endpoints and accepted for certain regulatory submissions. During the post-qualification phase, a group of 24 PCs were subjected exclusively to the developed tiered testing strategy, which is based on three Organisation for Economic Co-operation and Development (OECD) in vitro methods.

Materials and methods: The qualified in vitro testing strategy utilizes the Corrositex^® assay for the corrosivity (OECD TG 435), the Bovine Corneal Opacity and Permeability (BCOP) assay for ocular irritation (OECD TG 437), and the EpiDerm? tissue model-based Skin Irritation Test (SIT) for dermal irritation (OECD TG 439). In the first step, the pH of each PC was determined. For compounds with pH extremes ≥11 or ≤2, the Corrositex^® assay was generally conducted first. For compound(s) that were incompatible with or were negative in the Corrositex^® assay or had pH values between 2 and 11, the BCOP assay and SIT were performed first.

Results: The results of the tiered testing strategy’s qualification phase demonstrated that the BCOP assay is sensitive enough to identify a wide range of eye irritation/corrosion potentials and its over-prediction rate was considered acceptable to inform occupational hazards and ensure the proper handling practices of PCs. The SIT correctly predicted the skin irritation potential of 14 out of the 15 PCs included in the qualification phase, only over-predicting one PC. In the post-qualification phase, four PCs out of four tested were predicted corrosive by the Corrositex^® assay and thus no further testing was needed or conducted. The rest of the PCs were evaluated in the BCOP assay (both neat and as a 20% dilution), with the higher response being used for hazard classification. Four PCs were determined to be severe eye irritants, 1 a moderate irritant, 8 were mild irritants, and 8 were non-irritants. The same set of PCs was evaluated using the SIT and were classified as non-irritants to skin. These results are consistent with the BMS historical in vivo results showing a very low number of PCs as skin irritants.

Conclusions: This tiered in vitro testing strategy, which replaces the use of animal studies, was found to be reasonably accurate in its predictive capacity when compared to historical in vivo results and represents a conservative and reliable platform that can be utilized for the prediction of ocular and dermal irritation/corrosion potential of PCs and for subsequent GHS classification and worker safety hazard communications.     

The discovery and development of topical medicines for wound healing

Introduction: Chronic, nonhealing skin wounds claim >3% of the health-care budget in industrialized countries, and the incidence is rising. Currently, two parallel trends influence innovations within the field of wound healing: the need to reduce spread of antibiotic resistance and the emerging use of health economy and value-based models.

Areas covered: This review focuses on the discovery of drug candidates and development of treatments aiming to enhance wound healing in the heterogeneous group of patients with nonhealing wounds.

Expert opinion: Nonhealing wounds are multifaceted and recognized as difficult indications. The majority of products currently in use are medical device dressings, or concepts of negative pressure or hyperbaric oxygen treatment. Global best practice guidelines for the treatment of diabetic foot ulcers recommend debridement, redressing, as well as infection control, and are critical to the lack of coherent clinical evidence for many approved products in active wound care. To accelerate wound healing, there is an emerging trend toward biologics, gene therapy, and novel concepts for drug delivery in research and in the pipeline for clinical trials. Scientific delineation of the therapeutic mechanism of action is, in our opinion, vital for clinical trial success and for an increased fraction of medical products in the pharmaceutical pipeline.     

Advances in the treatment of chronic wounds: a patent review

Introduction: About 2% of the Western world population suffer from chronic wounds, resulting from underlying disorders (e.g., diabetes, excessive pressure, vascular insufficiencies and vasculitis), with a significant adverse effect on Quality of Life. Despite high incidence and economic burden, management of chronic wounds is still far from effective and novel therapies are in urgent need. Wound healing is a dynamic process of transient expression, function and clearance of mediators, enzymes and cell types. Failure to initiate, terminate or regulate leads to pathologic wound healing.

Areas covered: The present review discusses patents of the seven most promising classes of biological agents, mostly published in 2009 – 2014 (CYP11B1 inhibitors, peptide growth factors, prolyl-4-hydroxylase and matrix metalloproteinase inhibitors, bone marrow-derived mesenchymal stem cells, elastase and connexin43 inhibitors). Relevant information from peer-reviewed journals is also presented.

Expert Opinion: The aforementioned biological agents have different mechanisms of action, and considering the multifactorial pathogenesis of chronic wounds, they hold promise in treating chronic wounds. However, as administration of a certain biological agent may be beneficial in an early phase, it may slow down wound healing in a later phase. Basic and clinical research on chronic wound healing should therefore investigate the efficacy of these agents, alone and in concert, during the consecutive phases of wound healing.     

Transdermal atenolol releasing system: An approach towards its development

A polymer matrix system for transdermal delivery of atenolol was developed for its prolonged and controlled release using different ratios of ethylcellulose and hydroxypropyl methylcellulose. These polymeric matrix films were characterized for thickness, tensile strength, moisture content and drug content. They were also studied for in vitro drug release and in vitro drug skin permeation. The drug release from the films was found to be Fickian diffusion type and exhibiting linear relationship between drug release (Q) vs. square root of time (t^0.5). The in vitro skin permeation of drug from transdermal drug delivery system (TDDS) was evaluated using dermatomed pig skin. The product which shows in vitro drug skin permeation near to 64 mcg/h/ml was selected for in vivo studies. The in vivo studies revealed that Ma EC HPMC 46 is most effective among the other polymeric matrix TDDS. The AUC_0–28 with Ma EC HPMC 46 was better than orally administered conventional doses at twelve hours interval (AUC_0–28 1587 ng h/ml) as well as no trough and peaks in drug plasma level was recorded with TDDS. Hence, it could be concluded that the designed polymeric matrix TDDS of atenolol could be used successfully for effective and prolonged delivery of atenolol. However, it further demands exploration in clinic, an insight vision towards the development of TDDS for commercial use.     

Evaluation of wound healing effect of chitosan-based gel formulation containing vitexin

Acute or chronic wounds are one of the most common health problems worldwide and medicinal drugs or traditional remedies are often used in wound healing. Further studies regarding wound treatment are rapidly continuing. Vitexin is a phenolic compound, which is found in many medicinal plants, has different pharmacological effects such as anti-inflammatory, analgesic and antioxidant. In the present study, it is aimed to investigate the wound healing effect of formulation prepared as chitosan-based gel with vitexin in vivo and in vitro. Cytotoxicity and wound healing assays were used for in vitro and excisional wound model is used for in vivo studies. Extracted tissues from wound area were histologically examined. Wound healing process was monitored on 7, 14 and 21st days. When wound construction was evaluated, chitosan-based gel formulation containing vitexin demonstrated significant effect compared to control group. Histological examinations demonstrated that skin regeneration was promoted by vitexin formulation. Significant cell proliferation was observed with vitexin/chitosan dispersion in the wound healing assay performed with NIH 3T3 and HaCaT cells. In conclusion, our test substance chitosan-based gel formulation containing vitexin significantly accelerated wound healing both in vivo and in vitro.     

Pharmaceutical application of frog skin on full-thickness skin wound healing in mice

Abstract

Context: It has been proved that fresh frog skin is efficient in the wound healing process.

Objective: The purpose of study is to introduce a formulation of frog skin powder for evaluation of wound repair where fresh frog skin is not available.

Materials and methods: Rana ridibunda (Ranidae) skins were lyophilized, and a powder was prepared. The powder (0.0005?g) was then mixed with ointment (0.0065?g) for treating each wound. Formulation was used on full-thickness wounds on mice (FO group) and compared to positive and negative controls. In order to study the wound healing process, wound contraction, inflammation, number of fibroblast cells, neovascularization and collagen density were evaluated on days 2, 4 and 6 following the injury. Moreover, CFU measurement was performed for the evaluation of wound contamination.

Results: Acceleration in wound contraction in the FO group compared to control groups was significant (p?<?0.001) on days 4 and 6. Results showed that FO treatment considerably decreased inflammatory cells during the study. On day 4, FO treatment was significantly effective in increasing the number of fibroblast cells and collagen density (p?<?0.01 and p?<?0.05, respectively). On day 6 the number of fibroblast cells (p?<?0.001), collagen density (p?<?0.05) and neovascularization (p?<?0.05), were higher in the FO group than the control groups. Results of CFU measurement demonstrated significant reduction of wound contamination in FO treated wounds on days 2 (p?<?0.05) and 4 (p?<?0.01).

Discussion and conclusion: Our findings indicated that the pharmaceutical form of frog skin used in this study has considerable healing and antibacterial effects on wounds.     

Compritol 888 ATO: a multifunctional lipid excipient in drug delivery systems and nanopharmaceuticals

Introduction: Compritol® 888 ATO is a lipid excipient that is generally used in cosmetic industry as a surfactant, emulsifying agent and viscosity-inducing agent in emulsions or creams. Based on its chemical composition, Compritol 888 ATO is a blend of different esters of behenic acid with glycerol.

Areas covered: Recently, there has been great interest in the multiple roles that Compritol 888 ATO plays in various pharmaceutical delivery systems. Accordingly, this review aimed at summarizing the current and potential applications of Compritol 888 ATO in various drug delivery areas.

Expert opinion: Different researches have highlighted the feasibility of using Compritol 888 ATO as a lubricant or coating agent for oral solid dosage formulations. It has also been explored as a matrix-forming agent for controlling drug release. At present, the most common pharmaceutical application of Compritol 888 ATO is in lipid-based colloidal drug delivery system such as solid lipid microparticles, solid lipid nanoparticles and nanostructured lipid carriers. Although, Compritol 888 ATO has acceptable regulatory and safety profiles and although the number of articles that emphasize on its applicability as an innovative excipient in pharmaceutical technology is continuously increasing, it is not widely used in the pharmaceutical market products and its use is limited to its sustain release ability in extended release tablets.     

Topical gels of etofenamate: in vitro and in vivo evaluation

Abstract

Non-steroid anti-inflammatory drugs (NSAIDs), such as etofenamate, are among the most prescribed drugs used for their analgesic, anti-rheumatic, antipyretic and anti-inflammatory properties. Topical formulations have the main advantage of targeted delivery. However, drugs must overcome the skin due to its role as a physical and chemical barrier against the penetration of chemicals and microorganisms. This barrier must be altered to allow the permeation of drugs at a suitable rate to the desired site of activity. Permeation modulators can intercalate the skin outer layers causing structure disruption, opening an energetically favourable route for the drug to diffuse through. The aim of this work was the development of hydroalcoholic gels containing 5.0% (w/w) of etofenamate for topical administration with anti-inflammatory activity and enhanced drug delivery. The physical and chemical characterization, in vitro release and permeation studies and in vivo anti-inflammatory activity were assessed. The gel with 30% ethanol showed in vivo anti-inflammatory activity with suitable physical chemical and microbiologic characteristics. In vitro release and permeation studies revealed that the different amounts of ethanol used influenced the release profiles of etofenamate. Moreover, it was demonstrated that this formulation is an adequate vehicle for the etofenamate skin permeation.     

壳聚糖对临床手术创面修复的Meta分析

目的评价壳聚糖对临床手术创面修复的有效性及安全性。方法检索Cochrane图书馆临床对照试验资料库（CCTR）,Medline、Embase、PubMed数据库,中国期刊全文数据库（CNKI）、万方数字化期刊全文库、中文科技期刊全文数据库（VIP）和中文生物医学期刊文献库（CMCC）,收集壳聚糖修复手术创面的随机对照临床试验,使用RevMan 5.0软件进行Meta分析。结果共纳入16项研究,3 414例患者。Meta分析结果显示：壳聚糖对手术创面修复的愈合时间明显短于对照组[WMD=-0.64,95%CI（-0.69~-0.59）,P<0.000 01],且能更好地促进切口愈合[RR=1.03,95%CI（1.01~1.04）,P=0.0002];明显减轻术后疼痛[WMD=-3.49,95%CI（-5.07~-1.91）,P<0.000 1];减少术后感染[RR=0.49,95% CI：0.33~0.71,P=0.000 2]。结论壳聚糖能缩短术后伤口愈合时间,更好地促进伤口愈合,减轻疼痛,减少感染;但纳入的研究质量均不高,仍亟需更多高质量的临床试验进一步验证壳聚糖对临床手术后创面修复的有效性和安全性。     

The potential adverse effects of aromatase inhibitors on wound healing: in vitro and in vivo evidence

Background: Estrogens and several other endogenous substances are recognised as being important in the process of wound healing. However, the effect of aromatase and aromatase inhibition in the wound healing process has yet to be fully defined. Objective: A review of the in vitro and in vivo evidence on the effect of aromatase inhibition on wound healing. Methods: The primary medical search engines used for the study were Ovid MEDLINE (1950 – March 2009) and EMBASE (1980 – March 2009) databases. Results/conclusion: The delayed healing of cutaneous wounds in aged individuals may in part reflect the decline in circulating levels of dehydroepiandrosterone (DHEA) and estrogens. The beneficial response on wound healing that DHEA and estrogen exert may be blocked by aromatase inhibition. Based on animal models, aromatase inhibitors may adversely affect cutaneous wound healing in the acute setting. So far, there have been no clinical trials investigating the adverse affect of aromatase inhibitors on the process of cutaneous wound healing in humans. Postmenopausal patients who take aromatase inhibitors as an adjunct to breast cancer therapy may, therefore, be at increased risk of delayed wound healing. Further studies are necessary to assess the extent of the effects on the wound healing process.     

Skin substitutes to enhance wound healing

Biologically-based skin substitutes have developed as commercial products over the last 5 years. The first generation includes the collagen-based synthetic device, Integra, and Alloderm, which is based on devitalised and cross-linked human dermis. These are used as dermal replacements for third degree burns. Within the last year, the tissue-engineered product, Dermagraft-TC^®, has become available. While originally intended as a temporary covering for severe burns, Dermagraft-TC^® has proved to markedly improve the healing of deep second degree burns. The earliest living skin substitutes used autologous keratinocytes expanded in vitro. Two new products containing living cells, Dermagraft^® and Apligraf, are expected to be approved shortly for diabetic foot ulcers and venous stasis ulcers, respectively. Dermagraft^® is produced by growing human fibroblasts on a three-dimensional scaffold. The cells actively proliferate and lay down extracellular matrix to generate a papillary dermis-like device that shows a combination of angiogenic, growth factor and cell adhesion properties that enhance healing in diabetic foot ulcers. The production of Apligraf includes casting human fibroblasts in collagen, in order to generate a dermal equivalent on which is grown an epidermis. The structure is akin to a skin graft and is so applied. Despite Dermagraft^® and Apligraf being of allogeneic origin, rejection has not been an issue in clinical trials and possible contamination by pathogens has been eliminated as a concern through extensive testing. These developments represent a new concept and are expected to revolutionise wound care. They may also provide a platform for gene therapy applications.     

Novel microstructured sildenafil dosage forms as wound healing promoters

Purpose: Study the possible benefit of combining biodegradable polymers with sildenafil citrate (SC) in wound healing.

Method: Biodegradable micronized powdered formulations of SC were prepared by spray drying using chitosan (P₁) or chitosan/gum Arabic (P₂). Powders were characterized by differential scanning calorimetry, Scanning electron microscope, particle size analysis, flow and swelling behavior. The powders were also incorporated into microstructured gels and in vitro SC release from powders and gels was tested. In vivo wound healing acceleration was tested by measuring area contraction of excision wounds and histologically. Post-healing tensile strength (TS) for incision wounds in rats receiving powder formulations was tested.

Results: The powders were in the micron-size range showing no SC–polymers interaction. Powders had poor flow with angle of repose (θ) of 41 – 48°, and high moisture uptake reaching 107% for placebo powder P_o1. Good excision wound healing was seen with P₁ and G₁ formulations showing 98.4 and 98.5% reduction in wound area, respectively, compared with 83% for the control. Incision wounds were improved with P₁ showing TS value of 6.9 compared with 3.7 kg/cm² for control. Histological examinations supported.

Conclusion: Spray-dried chitosan/SC powder (P₁) and its gel form (G₁) could be promising wound healing promoters as supported by the histological examinations.