In vitro biocompatibility of transferosomes, ethosomes and transethosomes
Lipid nanocarriers (LN) for transdermal drug delivery, have gained more interest in recent years, due to their rapid penetration into the skin. Liposomes were investigated in the past with the goal of transdermal drug delivery, yet studies confirmed they were not able to achieve transdermal delivery, and should rather be considered for topical delivery. Focus moved to the ultradeformable lipid carriers due to their ability to penetrate the skin barrier without compromising the skin structure. Transferosomes are ultradeformable vesicles (UDV), which consist of a lipid and edge activator, and are the first generation of the elastic LN. Ethosomes are UDVs consisting of a lipid and ethanol, which acts as a membrane modulator, whereas transethosomes consist of a lipid and both an edge activator and ethanol. LN resemble cell organelles due to their dimensions and content, therefore, a risk of potential cytotoxicity occurs. The first step in determining the biocompatibility of these UDVs was to prepare and optimize LN formulations, including the UDVs (transferosomes, ethosomes and transethosomes) and liposomes as a control. After preparation of these vesicles, each system was characterized utilizing the standardized method of dynamic light scattering (DLS), measuring vesicle diameter, PDI and zeta potential. Quantitative image analysis, utilizing specific shape and size parameters have not been established for LN, due to being mainly used to characterize powder particles in the past. The size and shape parameters of each LN were established by means of image analysis with the Malvern Morphologi G3, including intensity mean, diameter of an equivalent circle (CE diameter), solidity, elongation, convexity, circularity and aspect ratio. The LN were fairly solid, and low levels of elongation were observed, as well as high levels of convexity. The circularity of the LN, however, were varied. It was concluded that elongation, convexity and circularity were parameters that could be utilized for characterization, complementary to DLS. The stability of each system was also observed for 90 days. The next step in determining the in vitro biocompatibility of the UDVs was to observe the effects they had on cells, by means of Thiazolyl blue tetrazolium bromide (MTT) and Trypan Blue dye exclusion assays, utilizing human malignant melanoma cells (A375) and primary epidermal keratinocytes (HaCat). Previous studies have suggested interference of the lipid content in liposomes with absorbance values as determined by the MTT assay, and it was investigated in this study whether this problem also occurred with UDVs. The effects of vesicle concentration on cell viability was investigated by means of MTT assay. A correlation between lipid content and high absorbance values was observed, therefore, confirming the interference of lipid content of the UDV with accurate cell viability results. The effects of treatment time on cell viability was also investigated, this time utilizing MTT, as well as Trypan Blue dye exclusion assay. No toxicity was observed for the A375 cells, even after the 48 h treatment period, however, cytotoxicity was observed when the HaCat cells were treated for periods longer than 48 h. Both the MTT and Trypan Blue method showed accurate results when determining cell viability, despite having different mechanisms through which they determine viability. The in vitro biocompatibility was therefore confirmed for the UDVs, although longer treatment periods may lead to cytotoxicity.
- Health Sciences