The objective of this investigation was to develop nanostructured lipid carriers (NLCs) of tacrolimus by the hot homogenization technique by sonication. NLCs are commonly prepared by emulsification and lyophilization. The feasibility of fabricating tacrolimus-loaded NLCs was successfully demonstrated in this study. The developed NLCs were characterized in terms of their particle size, zeta potential, entrapment efficiency (EE) of tacrolimus, and morphology. Studies were conducted to evaluate the effectiveness of the NLCs in improving the penetration rate through hairless mouse skin. Tacrolimus-loaded NLCs were found to have an average size of 123.4 ± 0.3 nm, a zeta potential of −24.3 ± 6.2 mV, and an EE of 50%. In vitro penetration tests revealed that the tacrolimus-loaded NLCs have a penetration rate that is 1.64 times that of the commercial tacrolimus ointment, Protopic ® .

For the prolonged delivery and sustained release rates of low molecular weight drugs, poly(lactic-co-glycolic acid) (PLGA) microparticles containing the drug SKL-2020 have been investigated. On increasing polyvinyl alcohol (PVA) concentration (from 0.2% to 5%), the size of microparticles decreased (from 48.02 µm to 10.63 µm) and more uniform size distribution was noticeable due to the powerful emulsifying ability of PVA. A higher drug loading (from 5% to 20%) caused a larger concentration gradient between 2 phases at the polymer precipitation step; this resulted in decreased encapsulation efficiency (from 34.19% to 25.67%) and a greater initial burst (from 61.71% to 70.05%). SKL-2020-loaded PLGA microparticles prepared with different fabrication conditions exhibited unique release patterns of SKL-2020. High PVA concentration and high drug loading led to an initial burst effect by rapid drug diffusion through the polymer matrix. Since PLGA microparticles enabled the slow release of SKL-2020 over 1 week in vitro and in vivo, more convenient and comfortable treatment could be facilitated with less frequent administration. It is feasible to design a release profile by mixing microparticles that were prepared with different fabrication conditions. By this method, the initial burst could be repressed properly and drug release rate could decrease.

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