Dermal Penetration Analysis of Curcumin in an ex vivo Porcine Ear Model Using Epifluorescence Microscopy and Digital Image Processing

Abstract

<b><i>Introduction:</i></b> Curcumin is a promising drug candidate, but its use for dermal application is limited due to its poor aqueous solubility. Thus, formulations that increase the solubility of curcumin are needed to fully exploit the therapeutic potential of curcumin. Various previous studies address this issue, but a comparison of the efficacy between these formulations remains difficult. The reason for this is a missing standard formulation as benchmark control and an easy-to-use skin penetration model that allows for a fast discrimination between different formulations. <b><i>Objective:</i></b> Thus, the aims of this study were the development of a curcumin standard formulation and a screening tool that allows for a fast discrimination between the dermal penetration efficacies of curcumin from different formulations. <b><i>Methods:</i></b> Ethanolic curcumin solutions were selected as simple and easy to produce standard formulations, and the ex vivo porcine ear model, coupled with epifluorescence microscopy and subsequent digital image analysis, was utilized to determine the dermal penetration efficacy of curcumin from the different formulations. <b><i>Results:</i></b> Results show that the utilized skin penetration model is a suitable and versatile tool that enables not only a fast determination of the dermal penetration efficacy of curcumin from different formulations but also a detailed and mechanistic information on the fate of chemical compounds after dermal penetration. Ethanolic solutions containing 0.25% curcumin were found to be the most suitable standard formulation. <b><i>Conclusions:</i></b> Results of the study provide a new, effective screening tool for the development of dermal formulations for improved dermal delivery of curcumin.

Hair Follicle Targeting and Dermal Drug Delivery with Curcumin Drug Nanocrystals—Essential Influence of Excipients

“…In this study the amount of penetrated curcumin was assessed by analyzing the fluorescence intensity of each image after the autofluorescence of the skin was fully extracted from the original image by means of an automated threshold algorithm. Hence, the detected fluorescence intensity corresponded to the amount of penetrated curcumin [16]. Results obtained from this analysis (Figure 5) substantiate the observations from the visual inspection of the microscopic images and from the analysis of the penetration depth (Figures 2 and 3).…”

“…Digital image analysis was used to measure the mean penetration depth (MPD) of curcumin into and through the skin as well as the penetration depth of the curcumin nanocrystals into the hair follicles. In addition, it was used to quantify the mean grey value (MGV) of each image as a surrogate for the total amount of penetrated curcumin into the skin [16]. In addition, changes in stratum corneum thickness caused due to the treatment of the skin with the different formulations were also analyzed.…”

“…The passive, dermal penetration efficacy of curcumin from the different formulations, i.e., MPD and MGV, were determined according to a previously established protocol [16] with ImageJ software [17][18][19]. For this, all images were subjected to an automated threshold protocol in order to eliminate the autofluorescence of the skin.…”

“…However, a clear picture can only be obtained by subjecting the images to a digital image analysis which enables the transfer of the observations into exact numbers. Digital processing enables to exactly measure the penetration depth of curcumin and to estimate the total amount of dermally penetrated curcumin [16].…”

Are lipid nanoparticles really superior? A holistic proof of concept study

“…Digital image analysis was performed with "ImageJ" software [20,21], and the epifluorescence images with 200-fold magnification were used for this. The penetration efficacy was assessed by determination of the total amount of penetrated dye (TAP) and by assessing the mean penetration depth (MPD) [22]. TAP and MPD were determined from the images after subjecting each image to an automated threshold algorithm (supplementary material Sect.…”