Targeted elimination of CD44+ prostate cancer stem cells using hyaluronic acid-coated selenium nanoparticles co-loaded with apigenin.

Castration-resistant prostate cancer is sustained by CD44+ prostate cancer stem cells (PCSCs), motivating targeted strategies that eliminate this resistant subpopulation. Here, we developed a CD44-targeted delivery system consisting of hyaluronic acid-coated selenium nanoparticles co-loaded with apigenin (HA-SeNP-Api) and evaluated its physicochemical performance, release behavior, and anti-PCSC activity. Dynamic light scattering revealed medium-dependent colloidal behavior: the hydrodynamic size in PBS (pH 7.4) increased from 169.8 nm (day 0) to 263.9 nm (72 h), remained comparatively stable in acidic PBS (pH 6.0; 223.6 to 231.8 nm), and markedly increased in PBS containing 10% FBS (192.4 to 542.5 nm). Zeta potential was strongly negative in PBS (∼-27.8 mV) but decreased in acidic PBS (∼-4.2 to -1.2 mV) and remained intermediate in PBS containing 10% FBS (∼-12.1 to -13.5 mV), consistent with medium-driven charge screening. The formulation exhibited sustained apigenin release over 72 h at pH 6.0 and pH 7.4, supported by Korsmeyer-Peppas fitting of the initial phase. In CD44+ PCSCs, HA-SeNP-Api produced the strongest cytotoxicity in the MTT assay (14.61% viability), exceeding the effects of apigenin, enzalutamide, SeNP, and non-targeted SeNP-Api (HA-). Flow cytometry confirmed pronounced apoptosis (71.67% total apoptosis) and a marked G2/M arrest (20.59%). Consistently, HA-SeNP-Api upregulated pro-apoptotic markers (BAX, CASP3, CASP8), reduced BCL2 expression, and suppressed pluripotency-associated genes (SOX2, OCT3/4, NANOG). Intracellular ROS profiling further indicated redox modulation by SeNP-containing formulations, with partial attenuation by NAC, supporting a ROS-linked contribution to the observed apoptotic response. Collectively, HA-SeNP-Api integrates CD44-mediated targeting with redox-driven stress signaling to achieve potent anti-PCSC activity, supporting further preclinical evaluation.