Abstract
Thymoquinone is a natural bioactive with significant therapeutic activity against multiple ailments including wound healing. The poor aqueous solubility and low skin permeability limit its therapeutic efficacy. The present investigation aimed to improve the biopharmaceutical attributes of thymoquinone to enhance its topical efficacy in wound healing. A nanoemulsion-based hydrogel system was designed and characterized as a nanotechnology-mediated drug delivery approach to improve the therapeutic efficacy of thymoquinone, utilizing a high-energy emulsification technique. The black seed oil, as a natural home of thymoquinone, was utilized to improve the drug loading capacity of the developed nanoemulsion system and reduced the oil droplet size to <100 nm through ultrasonication. The influence of formulation composition, and the ultrasonication process conditions, were investigated on the mean globule size and polydispersity index of the generated nanoemulsion. Irrespective of surfactant/co-surfactant ratio and % concentration of surfactant/co-surfactant mixture, the ultrasonication time had a significant (p < 0.05) influence on the mean droplet size and polydispersity index of the generated nanoemulsion. The developed nanoemulgel system of thymoquinone demonstrated the pseudoplastic behavior with thixotropic properties, and this behavior is desirable for topical application. The nanoemulgel system of thymoquinone exhibited significant enhancement (p < 0.05) in skin penetrability and deposition characteristics after topical administration compared to the conventional hydrogel system. The developed nanoemulgel system of thymoquinone exhibited quicker and early healing in wounded Wistar rats compared to the conventional hydrogel of thymoquinone, while showing comparable healing efficacy with respect to marketed silver sulfadiazine (1%) cream. Furthermore, histopathology analysis of animals treated with a developed formulation system demonstrated the formation of the thick epidermal layer, papillary dermis along with the presence of extensive and organized collagen fibers in newly healed tissues. The outcome of this investigation signifies that topical delivery of thymoquinone through nanoemulgel system is a promising candidate which accelerates the process of wound healing in preclinical study.
Highlights
Physical injury to the skin that leads it to break and open is known as a wound [1]
Thymoquinone (TMQ) is a biologically active plant therapeutic, obtained from black seed (Nigella sativa), that has been shown to have multifunction properties, including antimicrobial [5,6], anti-inflammatory [7], anti-allergic [8], anti-oxidant [9], anti-neoplastic [10], anti-diabetic [11], and many more desirable properties [12,13] that have been demonstrated in different investigations
Ethyl oleate, castor oil, isopropyl myristate, isopropyl alcohol, sesame oil, PEG 400, tween 20, tween 80, and Kolliphor EL, Solutol HS were purchased from Sigma Aldrich (Hamburg, Germany), Black seed oil was purchased from Amazing Herbs, (Buford GA, USA)
Summary
Physical injury to the skin that leads it to break and open is known as a wound [1]. Wound healing is one of the most complex physiological processes, which involve the events of clotting, coagulation, inflammation, and generation of new tissue [1,2]. The wound healing properties of TMQ have been attributed due to its anti-microbial, resistance-modifying, anti-oxidant, and anti-inflammatory properties [5,6,7,8,9,10,16]. The therapeutic application of TMQ, as a woundhealing agent, has resulted in an enhanced anti-inflammatory response, diminished oxidative stress, better fibroblast formation, increased granular tissue production, augmented wound contraction, and re-epithelization [15,16]. Despite its multifunction activity and varied promising medical application, the therapeutic effectiveness of TMQ is restricted because of poor water solubility and low skin penetrability that result in low systemic availability [11,18]. An easy way for solving the associated stability and systemic availability issue of TMQ for better efficacy in wound healing is to assure its protection from photo-degradation, first-pass metabolism, and to enhance its targetability through topical administration. Topical delivery of TMQ can improve its local concentrations at the disease area, and control the drug release for improved efficacy of TMQ in wound healing
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