Liposomal Drug Delivery Systems: A Comprehensive Review

Abstract

Liposomal drug delivery has emerged as one of the most successful nanotechnology-based approaches for improving the therapeutic performance of conventional drugs. Liposomes are spherical vesicular systems composed mainly of phospholipid bilayers surrounding an aqueous core. Their unique structure allows them to encapsulate both hydrophilic and lipophilic therapeutic agents, protect drugs from premature degradation, modify pharmacokinetics, improve drug accumulation at desired sites, and reduce systemic toxicity. Since the approval of the first liposomal formulation, Doxil® (liposomal doxorubicin), liposomal systems have progressed from experimental carriers to clinically established drug-delivery platforms. Recent developments include PEGylated, ligand-targeted, stimuli-responsive, immunoliposomes, and novel zwitterionic systems such as PMPCylated liposomes. These technologies aim to overcome limitations including rapid clearance, drug leakage, poor tissue penetration, manufacturing variability, and immune recognition. This review discusses the structure, composition, classification, preparation methods, drug-loading approaches, mechanisms of drug delivery, advantages, limitations, pharmaceutical applications, marketed products, evaluation parameters, recent advances, and future perspectives of liposomal drug delivery.