Interactions between loaded drugs and surfactant molecules in micellar drug delivery systems: A critical review

Efficacy of drug is often challenged by their premature degradation, low solubility, side effect, and rapid clearance from circulatory system. Consequently, about 60% of newly developed drugs demonstrate declined bioactivity and are of limited use. Hence, enhancing solubility of poorly soluble drugs and protecting them from early degradation are formidable tasks. Here, surfactants play pivotal role to solubilize a wide variety of drug molecules via micellization in physiologically relevant fluids. Higher micellar stability, ease of formation, and low maintenance expenses often present surfactants as promising materials over various conventionally used liposomes and phospholipid-based formulations. Furthermore, they can encapsulate both the hydrophobic and hydrophilic drugs and minimize their excretion. There are several interaction parameters that influence critical micelle concentration (cmc) of surfactants. Such interactions between drug and carrier materials can also impact loading efficacy, drugs’ lifetime, and targeted delivery. There are several review articles on carrier structures, designing methods, and targeted delivery, however, efforts to review interactions between loaded drugs and carrier materials along with their impact on micellization remained underrepresented. This review presents a critical analysis of interactions between loaded drugs and surfactants in micellar delivery systems. Finally, future direction of in-depth understanding of drug surfactant interactions has been highlighted.