Optimizing Dermal Delivery of Linezolid for Treating Skin and Soft Tissue Infections: NLC-Based Gel Formulation Using Taguchi Design

Abstract

Background: Uncomplicated skin and soft tissue infections account for approximately 200 million visits to ambulatory care settings annually. Linezolid (LNZ) is an oxazolidinone that has proven its effectiveness in combating skin and soft tissue infections caused by gram-positive pathogens. LNZ is administered via oral suspension, tablets, or an intravenous route in most in-stances. However, its extended therapy leads to undesirable side effects like diarrhoea, thrombo-cytopenia, myelosuppression, lactic acidosis, etc. and even life-threatening complications. The dermal administration of LNZ offers an alternative route, ensuring localized and sustained release at the site of infection. This approach may reduce systemic exposure and allow for lower doses compared to oral ingestion, which can decrease the risk of adverse effects. Objective: This research aimed to develop a nanostructured lipid carrier (NLC)-based gel for de-livering LNZ via the dermal route to treat uncomplicated skin and soft tissue infections. Methods: NLC were developed by high-shear homogenisation and sonication method using glyc-eryl trimyristate as a solid lipid and neem oil as a liquid lipid. The Taguchi design was employed to optimize NLCs using surfactant concentration (mg), drug-to-lipid ratio, and sonication time (sec) as independent variables. Their effect on particle size, zeta potential, and entrapment effi-ciency was studied. The optimized nanocarriers were developed into a gel product and evaluated for drug release, permeation, and antibacterial activity. Results: The optimised process parameters to attain outcomes were 2% surfactant, 1:1 drug-to-lipid ratio and 300 seconds of sonication. The resulting NLC had an average size of 191.2 ± 2.76 nm, a zeta potential of -30.7 ± 4.50 mV, and 84.89 ± 2.76% drug entrapment. NLC-based gel dis-played anomalous transport with a 90.16 % drug release. The gel showed a strong antibacterial effect against Staphylococcus aureus with a 7.57 ± 0.12 cm mean zone of inhibition. Ex-vivo skin permeation studies revealed 24.19 ± 0.19 % drug permeation and 64.46 ± 0.58% cutaneous depo-sition. NLC-based gel demonstrated a significant decrease in colony-forming units in infected an-imal models. Conclusion: The ex-vivo investigations demonstrated the presence of LNZ at the infection site, enhancing therapeutic effectiveness. In vitro and in-vivo findings illustrated the substantial anti-bacterial efficacy of LNZ NLC-based gel. The adoption of NLC-based gel exhibits promising po-tential as a carrier for dermal delivery of LNZ.