Self-emulsifying drug delivery systems: A comparison of dry and wet reverse micelles.

This study aimed to compare the performance of dry reverse micelles (dRMs) and wet reverse micelles (wRMs) in self-emulsifying drug delivery systems (SEDDS). Reverse micelles (RMs) were formed using cationic, amphoteric, and non-ionic surfactants with various model dyes incorporated into these RMs. Reverse critical micellar concentration (rCMC), entrapment efficiency (EE), and partition coefficients (logD) were determined. SEDDS were loaded with RMs, and their size distributions, polydispersity index (PDI), and zeta potential were evaluated. Cytotoxicity levels, cellular uptake, and membrane permeability of Caco-2 cells were tested. Furthermore, horseradish peroxidase (HRP) loaded SEDDS-RMs were administered to rats, and plasma HRP concentration and bioavailability were determined. Sorbitan monooleate-based dRMs exhibited an rCMC of 0.95 % and 0.6 % for wRMs, with R values of 4.7 and 43.2, respectively. The lower the hydrophilic lipophilic balance (HLB) of the oily phase, the lower the water uptake capacity of reverse micelles. Incorporating methylene blue into dRMs resulted in a logD of 1.56 and an EE of 97 %, compared to 0.59 and 74 % in wRMs. Cytotoxicity studies revealed over 90 % cell survival at concentrations up to 0.5 % for SEDDS-dRMs, while SEDDS-wRMs caused complete cell death at concentrations exceeding 0.4 %. Transwell diffusion studies showed that SEDDS-dRMs and SEDDS-wRMs enhanced membrane permeability by 7.5- and 13.5-fold, respectively. SEDDS containing HRP-loaded dry and wet reverse micelles provided an oral bioavailability of 11.2 % and 7.9 % in rats, respectively. Conclusion: Due to their ability to achieve higher logD, enhance encapsulation efficiency, and improve the oral bioavailability of a model protein, dRMs are favored over wRMs in SEDDS. STATEMENT OF SIGNIFICANCE: Although several strategies have been proposed to improve the bioavailability of peptide-based drugs, challenges related to stability and oral bioavailability still remain. Reverse micelles, which are nanoscale structures, have great potential with advantages such as high encapsulation efficiency, protection against enzymatic degradation, and increased permeability across biological membranes. This study presents a comparative evaluation of dry and wet reverse micelles in self-emulsifying drug delivery systems. The findings highlight that reverse micelles are a promising nanocarrier system for enhancing drug solubility, stability, and cellular permeability, ultimately contributing to more effective oral drug delivery strategies. This advancement could significantly pave the way for optimizing reverse micelle-based formulations for biomedical applications, especially in protein and peptide therapeutics.