Design and Evaluation of Babchi Oil Co-Loaded with Tacrolimus NLC Gel for Improved Cutaneous Delivery

Abstract

This study focuses on the development and evaluation of a novel nanostructured lipid carrier (NLC) gel co-loaded with Tacrolimus and Babchi oil (Psoralea corylifolia) to enhance cutaneous drug delivery. Tacrolimus, a calcium channel blocker with vasodilatory properties, is limited in topical applications due to its poor aqueous solubility and susceptibility to photodegradation. Babchi oil, a traditional herbal remedy known for its antimicrobial and anti-inflammatory properties, was employed both as a functional therapeutic agent and as part of the lipid matrix to improve delivery performance. The NLCs were formulated using a 2³ factorial design, incorporating glyceryl monostearate as the solid lipid, and oleic acid along with Babchi oil as the liquid lipid phase. The optimized formulation demonstrated desirable physicochemical properties, with a particle size of 150 ± 5 nm, a polydispersity index (PDI) of 0.23 ± 0.02, a zeta potential of –30.1 ± 1.5 mV, entrapment efficiency of 78.5 ± 2.5%, and drug loading of 8.2 ± 0.6%. FTIR analysis confirmed the physicochemical compatibility of all formulation components. In vitro drug release studies conducted using Franz diffusion cells (pH 6.8, 32°C) revealed a sustained biphasic release pattern over 24 hours, with 82.6 ± 3.1% of Tacrolimus and 78.9 ± 2.8% of Babchi oil released. Kinetic modeling indicated that the release followed the Higuchi model (R² > 0.98), suggesting diffusion-controlled mechanisms. The NLC gel, formulated in a Carbopol 940 base, exhibited excellent spreadability (28.5 ± 2.3 g·cm/sec) and a skin-compatible pH (6.4 ± 0.1). Stability studies over three months confirmed the formulation's robustness at 4°C and 25°C, with only minor aggregation noted at 40°C. Overall, the co-loaded NLC gel effectively enhanced the stability, skin permeation, and sustained release of Tacrolimus, establishing its potential as a promising therapeutic platform for chronic dermatological conditions such as scleroderma, psoriasis, and vitiligo.