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Thymol-loaded PLGA nanoparticles (TH-NPs) were incorporated into different semi-solid formulations using variable gelling agents (carbomer, polysaccharide and poloxamer). The formulations were physicochemically characterized in terms of size, polydispersity index and zeta potential. Moreover, stability studies were performed by analyzing the backscattering profile showing that the gels were able to increase the nanoparticles stability at 4 °C. Moreover, rheological properties showed that all gels were able to increase the viscosity of TH-NPs with the carbomer gels showing the highest values. Moreover, the observation of carbomer dispersed TH-NPs under electron microscopical techniques showed 3D nanometric cross-linked filaments with the NPs found embedded in the threads. In addition, cytotoxicity studies showed that keratinocyte cells in contact with the formulations obtained cell viability values higher than 70 %. Furthermore, antimicrobial efficacy was assessed against C. acnes and S. epidermidis showing that the formulations eliminated the pathogenic C. acnes but preserved the resident S. epidermidis which contributes towards a healthy skin microbiota. Finally, biomechanical properties of TH-NPs dispersed in carbomer gels in contact with healthy human skin were studied showing that they did not alter skin properties and were able to reduce sebum which is increased in acne vulgaris. As a conclusion, TH-NPs dispersed in semi-solid formulations and, especially in carbomer gels, may constitute a suitable solution for the treatment of acne vulgaris., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

Clotrimazole (CLT) was formulated in a multiple W/O/W emulsion (ME) with the aim of evaluating its potential as topical anticandidal agent and comparing with marketed products. A previously evaluated CLT-ME was selected and physicochemically characterized. The in vitro release behavior and the ex vivo permeation profiles were assessed using Franz diffusion cells using three different types of biological membranes: human skin and porcine buccal, sublingual and vaginal mucosae. The antifungal activity against Candida strains was also tested. Results showed CLT-MEs sizes of 29.206 and 47.678 μm with skin compatible pH values of 6.47 and 6.42 exhibiting high zeta potential values of -55.13 and -55.59 mV with dependence on the pH variation. The physicochemical stability was kept for a period of 180 days of storage at room temperature. CLT-MEs exhibited pseudoplastic behavior with hysteresis areas and viscosities of 286 and 331 mPa⋅s showing higher spreadability properties than commercial counterparts. An improved CLT release pattern was supplied by the ME system following a hyperbolic model. Likewise, ME system gave higher skin permeation flux of CLT than commercial reference. CLT amounts retained in the skin and mucosae were also higher than commercial references, which coupled with the higher antimycotic efficacy make CLT-MEs a great tool for clinical investigation of topical candidiasis treatments., (Copyright © 2018 Elsevier B.V. All rights reserved.)