Development and evaluation of dipalmitoyl phosphatidylcholine (DPPC) liposomal gel: rheology and in vitro drug release properties

Liposomes have emerged as pivotal entities in the field of therapeutics, particularly in the domain of protein and vaccine administration. Hence, the development of novel liposomal formulations has garnered considerable interest. Liposomal delivery systems are considered advantageous as medication carriers, especially in the field of dermatology, owing to their moisturizing and restorative characteristics. Nevertheless, a significant drawback in the utilization of liposomes in topical applications is the inherent fluidity of the formulation, which might result in leakage following delivery to the skin surface. The use of liposomes inside the gel matrix, while maintaining the integrity of the vesicles, presents a potentially appealing method for topical administration. The primary objective of this work is to develop a liposomal-loaded gel formulation and assess its in vitro release characteristics as well as its rheological profile, including viscoelastic properties and flow behaviour. This study incorporated two different types of drugs, namely hydrophilic (specifically diphenhydramine hydrochloride) and hydrophobic (namely curcumin), inside its formulations. A liposome, composed of a long alkyl chain lipid such as DPPC with a chain length of 16, was synthesized using the thin film hydration process and subsequently integrated into a carbopol gel. It is noteworthy that the introduction of diphenhydramine hydrochloride (DPH) resulted in a substantial decrease in the elastic modulus and cohesiveness of the liposomal gel. Conversely, the incorporation of curcumin-loaded liposomal gel led to an increase in critical strain and cohesiveness when compared to the plain liposomal gel. In contrast, the liposomal gel containing DPH and curcumin demonstrated a reduced release rate compared to the plain liposomal gel, spanning a duration of 48 h. The in vitro release studies offer the potential for the utilization of liposomal gels as a sustained delivery system.