Development of folate-grafted poly-3-hydroxybutyrate nanoparticles-embedded chitosan thermosensitive hydrogel for sustained and targeted delivery of epirubicin.

Epirubicin (EPR) is a first-line chemotherapeutic agent for breast cancer. However, EPR is associated with significant side effects, including systemic toxicity, cardiotoxicity, and gastrointestinal complications. In this study, EPR-loaded folate-grafted, poly-3-hydroxybutyrate nanoparticles (FPB2) were prepared. These nanoparticles were subsequently incorporated into an injectable thermosensitive chitosan (CS) hydrogel to obtain the CSNG nanocomposite hydrogel. Scanning electron microscopy confirmed the formation of a cross-linked three-dimensional hydrogel network. Drug release studies revealed fivefold higher EPR release (44.16 ± 0.57%) at pH 5.5 compared with physiological pH 7.4, indicating pH-responsive drug release behavior. The CSNG nanocomposite hydrogel also exhibited pH-responsive swelling and accelerated hydrolytic degradation under acidic conditions. Hemolysis studies showed <4% hemolysis, indicating excellent hemocompatibility. Cytotoxicity evaluation against MCF-7 breast cancer cells demonstrated enhanced anticancer activity, with an IC₅₀ value of 0.9 μg/mL at 24 h, representing approximately 10.9-fold higher cytotoxicity compared with the EPR-loaded CS hydrogel. Morphological observations further confirmed apoptosis in treated cells. Overall, the developed CSNG nanocomposite hydrogel represents a promising platform for the targeted delivery of hydrophilic chemotherapeutic agents.