Development and Efficacy of Enzyme-Responsive Squalene-Chidamide Nanoparticles for Pancreatic Cancer.

Here, we present a protocol to address the limited intratumoral penetration of small-molecule drugs caused by the dense extracellular matrix (ECM) of pancreatic ductal adenocarcinoma (PDAC). Prodrugs offer great potential to overcome this challenge by enhancing drug penetration and tumor-killing efficacy. Squalene (SQ), a natural precursor for cholesterol biosynthesis with excellent biosafety and biocompatibility, can improve the membrane compatibility of hydrophilic drugs and enhance their cellular uptake when conjugated to chemotherapeutic agents or bioactive small molecules. In this study, we developed a novel lipophilic SQ-based prodrug system: the hydrophilic anticancer drug chidamide (CHI) was conjugated to SQ via an amide bond -- a linkage responsive to pancreatin and cathepsin B (key enzymes overexpressed in the PDAC microenvironment). This conjugation yielded an amphiphilic SQ-CHI prodrug, which was further self-assembled into folate (FA)-modified nanoparticles (FA-SQ-CHI NPs). The optimized NPs exhibited a uniform hydrodynamic diameter of 173.3 ± 1.5 nm, a polydispersity index (PDI) of 0.181 ± 0.18, a high drug loading capacity of 59.0% ± 0.77%, and a stable Zeta potential of -13.10 ± 0.86 mV. In vitro release studies showed that the NPs achieved 80.2% ± 4.22% cumulative drug release within 72 h in the presence of 0.25% pancreatin, while only 33%-38% release was observed in pH-adjusted buffers (pH 4.5 or 7.4) without enzymes. Cellular uptake assays confirmed that FA modification significantly enhanced intracellular delivery efficiency, with 1.8-2.3-fold higher fluorescence intensity in PDAC cells (PSN-1 and CFPAC-1) compared to non-targeted NPs at 12-24 h. The current protocol provides a comprehensive methodology for the synthesis and characterization of the prodrug, in vitro evaluation of enzyme-responsive release kinetics, and comparative analyses of therapeutic efficacy and tissue penetration, highlighting the nanocarrier's core advantages of targeted delivery, high drug loading, and enzyme-triggered controlled release.