Kollidon® SR–Stearic Acid Based Thermoresponsive Solid Lipid Nanoparticles for Dual Cisplatin–Epirubicin Delivery: Formulation Development and In-Vitro Evaluation

Abstract

Purpose

Conventional chemotherapy is limited by premature drug leakage, systemic toxicity, and inefficient intracellular co-delivery, leading to reduced therapeutic efficacy and the development of drug resistance. To address these limitations, thermoresponsive solid lipid nanoparticles (TR-SLN) were developed for controlled co-delivery of cisplatin (CIS) and epirubicin (EPI) by integrating a sustained-release Kollidon^® SR matrix with a PEG-functionalized stearic acid lipid core.

Methods

Nine formulations were prepared using a modified hot homogenization technique and systematically characterized. Drug-polymer interactions were studied by Fourier transform Infrared Spectroscopy. Particle size, PDI and zeta potential were determined using dynamic light scattering measurements. Morphology of nanoparticles was assessed by Scanning electron microscopy. Thermal behavior of nanoformulations was investigated using DSC and TGA. XRD studies were performed to assess physical state of drugs in nanoparticles. The cytotoxic effects of the formulations were evaluated in-vitro using the MCF-7 human breast cancer cell line.

Results

The optimized formulation, TR-SLN-9, exhibited high entrapment efficiency (CIS 93.4 ± 2.2%, EPI 80.8 ± 3.4%), favorable drug loading, nanoscale particle size (263 ± 1.8 nm), and narrow polydispersity. Solid-state analysis confirmed amorphous drug dispersion within the lipid matrix, supporting improved physical stability. In vitro release studies demonstrated minimal drug leakage at 37 °C and accelerated release under mild hyperthermia (40 to 42 °C) and acidic pH, indicating stimuli-responsive diffusion-controlled behavior. Cytotoxicity evaluation in MCF-7 breast cancer cells showed significantly enhanced anticancer activity of TR-SLN compared to free drugs, confirming synergistic intracellular co-delivery.

Conclusion

These results indicate that PEG-mediated thermoresponsive SLNs offer a promising platform for improving combination chemotherapy delivery in breast cancer.

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Mehmood, F., Khan, M.I., Ahmad, Z. et al. Kollidon^® SR–Stearic Acid Based Thermoresponsive Solid Lipid Nanoparticles for Dual Cisplatin–Epirubicin Delivery: Formulation Development and In-Vitro Evaluation. J Pharm Innov 21, 526 (2026). https://doi.org/10.1007/s12247-026-10739-z