PEGylated pH-Responsive Liposomes for Enhancing the Intracellular Uptake and Cytotoxicity of Paclitaxel in MCF-7...

This study aimed to develop paclitaxel (PTX)-loaded PEGylated (PEG)-pH-sensitive (SpH) liposomes to enhance drug delivery efficiency and cytotoxicity against MCF-7 breast cancer cells. PTX-loaded PEG-SpH liposomes were prepared using the thin film hydration method. ATR-FTIR compatibility studies revealed no significant interactions among liposome formulation components. TEM images confirmed spherical morphology, stability, and an ideal size range (180-200 nm) for improved blood circulation. At pH 5.5, liposomes exhibited increased size and positive zeta potential, indicating pH-sensitive properties due to CHEMS response to the acidic tumor microenvironment. Conversely, at pH 7.4, liposomes showed a slightly larger size (199.25 ± 1.64 nm) and a more negative zeta potential (-36.94 ± 0.32 mV), suggesting successful PEG-SpH surface modification, enhancing stability, and reducing aggregation. PTX-loaded PEG-SpH liposomes demonstrated high encapsulation efficiency (84.57 ± 0.92% w/w) and drug loading capacity (4.12 ± 0.26% w/w). In-vitro drug release studies revealed accelerated first-order PTX release at pH 5.5 and a controlled zero-order release at pH 7.4. Cellular uptake studies on MCF-7 cells demonstrated enhanced PTX uptake, attributed to mPEG-PCL incorporation prolonging circulation time and CHEMS facilitating PTX release in the tumor microenvironment. Furthermore, PTX-loaded PEG-SpH liposomes exhibited significantly improved cytotoxicity with an IC₅₀ value of 1.107 µM after 72-h incubation, approximately 90% lower than plain PTX solution. Stability studies confirmed the robustness of the liposomal formulation under various storage conditions. These findings highlight the potential of PEGylated pH-responsive liposomes as effective nanocarriers for enhancing PTX therapy against breast cancer.