pH-sensitive liposomes bearing a chemotherapeutic agent and a natural apoptosis modulator for effective intracellular delivery to the solid tumor.

The intracellular delivery of the drug to the solid tumor is a major challenge in the treatment of solid tumors. This project aims to increase cytosolic drug delivery using the endosomal escape of drugs. Topotecan (TPT) and capsaicin were used for the treatment of solid tumors. The pH-dependent conversion of active lactone form to inactive carboxylic form is a major problem of TPT that limits its therapeutic use. Liposomal encapsulation of TPT improved the stability of active lactone form and increased the therapeutic efficacy of TPT. Endosomal degradation of liposomes may reduce the content in the target cells. To solve these problems, pH-sensitive liposomes (pSLPs) were developed which improved the intracellular drug delivery by the endosomal escape of drugs. The liposomes (LPs) bearing the drug(s) were prepared using the cast film method and optimized for various formulation and process variables using the Design-Expert 7 software by employing the Box-Behnken design (BBD). The developed hyaluronic acid (HA)-conjugated pSLPs (HA-pSLPs) displayed a vesicle size of 166.5 ± 2.31 nm, zeta potential - 30.53 ± 0.91, and entrapment efficiency of 44.39 ± 1.78%, and 73.48 ± 2.15% for TPT and CAP, respectively. HA-pSLPs displayed better cytotoxicity in comparison to free drugs either single or in combination on the MCF-7 cell line. The apoptosis and cellular uptake of HA-pSLPs were increased ⁓ 4.45-fold and ⁓ 6.95-fold as compared to unconjugated pSLPs, respectively. The pharmacokinetic studies in Balb/c mice demonstrated that HA-pSLPs increased the half-life, MRT, and AUC in comparison to the free drug solution. The HA-pSLPs formulation has shown remarkable tumor regression as compared to PpSLPs, pSLPs, and free drug combinations. These results demonstrated that TPT- and CAP-loaded HA-pSLPs offer a potential platform for targeted drug delivery to solid tumors.