Polyherbal Liposomal Gel for Topical Drug Delivery: A Review on Formulation Strategies, Carrier Optimization, and Therapeutic Potential

Abstract

Topical drug delivery remains an attractive route for both local and systemic therapy, offering the advantage of avoiding hepatic first-pass metabolism and gastrointestinal degradation while enabling site-specific action. However, conventional topical herbal formulations are frequently limited by poor skin permeability, instability of phytoconstituents, and inconsistent therapeutic outcomes. Liposomes, as biocompatible vesicular carriers composed of phospholipid bilayers, have emerged as a promising strategy to overcome these limitations by improving drug solubilization, protecting labile actives from degradation, enhancing skin permeation, and enabling sustained release. This review examines the current literature on liposomal and liposomal-gel delivery systems, with particular focus on formulation variables such as lipid-to-cholesterol ratio, hydration conditions, sonication parameters, and gelling agent selection, and their influence on vesicle size, entrapment efficiency, zeta potential, and drug release behaviour. The pharmacological evidence supporting three widely studied phytoconstituents relevant to polyherbal topical formulations- curcumin (Curcuma longa), Nigella sativa, and Piper longum- is also reviewed, along with comparative literature on their incorporation into liposomal and gel-based carriers. The review identifies a clear research gap regarding standardized polyherbal (multi-extract) liposomal gel systems, as most existing studies address single-extract or single-drug liposomal formulations, and highlights avenues for future research including in-vivo permeation studies, advanced characterization, and scale-up strategies for polyherbal liposomal topical products.