pH-Responsive Apalutamide-Loaded ZIF-8 Nanoparticlesfor Zinc-Enhanced Dual Cytotoxicity in Prostate Cancer

Abstract Apalutamide (APA) is a recently FDA-approved androgen receptor inhibitor for the treatment of nonmetastatic castration-resistant prostate cancer. Herein, we report a pH-responsive, dual-acting nanocarrier system based on zeolitic imidazolate framework-8 (ZIF-8) to enhance the therapeutic efficacy of APA. APA was successfully encapsulated into ZIF-8 nanoparticles with an encapsulation efficiency of 69.4% and a drug loading capacity of 47.8% (APA@ZIF-8). The structural and physicochemical properties of ZIF-8 and APA@ZIF-8 were comprehensively characterized using FTIR, SEM, STEM, DLS, EDX, PXRD, TGA, and BET analyses. Drug release studies demonstrated a pronounced pH-dependent behavior, with a faster release at pH 5.0 (93% over 120 h) compared to pH 7.4 (62% over 120 h), indicating suitability for the acidic tumor microenvironment. Biocompatibility assessments, including hemolysis and serum protein binding assays, confirmed the hemocompatible nature of both ZIF-8 and APA@ZIF-8 nanoparticles. The biological effects of APA, ZIF-8, and APA@ZIF-8 were evaluated through cell viability, cell cycle progression, reactive oxygen species generation, apoptosis, and androgen receptor transcriptional activity in prostate cancer and healthy cell lines. The results reveal that the pH-triggered biodegradation of ZIF-8 leads to zinc ion release, which, together with APA, contributes to enhanced cytotoxic effects in prostate cancer cells, highlighting the potential of APA@ZIF-8 as a zinc-enhanced dual cytotoxic nanotherapeutic platform.