Formulation and Evaluation of Liposomal ?-Lipoic Acid (Ala) Cream and Stability Challenges: A Critical Review

Abstract

Alpha-lipoic acid (ALA), also known as thioctic acid, is a naturally occurring disulfide compound that exhibits strong amphipathic antioxidant properties, enabling it to function effectively in both aqueous and lipid biological environments. It plays a crucial role in mitochondrial energy metabolism and has been extensively studied for its wide range of pharmacological activities, including anti-aging, neuroprotective, anti-inflammatory, and dermatological benefits. In skin-related applications, ALA has demonstrated potential in reducing oxidative stress-induced damage, improving skin elasticity, and delaying visible signs of aging such as wrinkles and hyperpigmentation. Despite its significant therapeutic and cosmetic potential, the clinical application of ALA is severely constrained by several physicochemical and pharmacokinetic limitations. These include poor aqueous solubility, high susceptibility to oxidation, photodegradation under light exposure, thermal instability, and a relatively short biological half-life. Moreover, its limited permeability through the stratum corneum further reduces its effectiveness in topical delivery systems, necessitating advanced formulation strategies to enhance its stability and bioavailability. In recent years, liposomal drug delivery systems have emerged as a highly promising approach to address these challenges. Liposomes are vesicular carriers composed of phospholipid bilayers that can encapsulate both hydrophilic and lipophilic compounds, thereby improving drug stability, solubility, and controlled release characteristics. Liposomal incorporation of ALA significantly enhances its dermal penetration by facilitating fusion with skin lipid layers, improving retention within deeper epidermal structures, and protecting the active compound from environmental degradation. When formulated into cream-based semisolid systems, liposomal ALA enables sustained and localized delivery, making it highly suitable for dermatological and cosmeceutical applications. However, despite these advantages, liposomal formulations are inherently associated with several stability challenges that limit their long-term effectiveness and commercial scalability. These include oxidative degradation of phospholipids, hydrolytic breakdown, leakage of encapsulated drug from vesicles, aggregation and fusion of liposomes, changes in particle size distribution, phase separation within the cream matrix, and reduced entrapment efficiency over time. Environmental factors such as temperature fluctuations, light exposure, and oxygen availability further exacerbate these instability issues, leading to reduced shelf-life and compromised therapeutic performance.

Keywords

Alpha-lipoic acid (ALA); liposomes; topical drug delivery; antioxidant therapy; liposomal cream; dermatological formulation; cosmeceuticals; stability challenges; phospholipid vesicles; skin penetration enhancement; nanocarrier systems; controlled release.