Photodynamic therapy is a noninvasive type of phototherapy with a high capacity to boost specific antitumor immunity by causing immunogenic cell death. However, the photodynamic therapeutic potency toward solid tumors is dampened by tumor hypoxia that negatively impairs the generation of cytotoxic singlet oxygen and promotes the formation of tumor immunosuppression. Herein, fluorinated CaCO₃ (CaF) nanoparticles are prepared with the addition of dopamine-conjugated perfluorosebacic acid and ferric chloride into a calcium chloride ethanol solution via an ammonium bicarbonate-mediated gas-diffusion process. After being coated with commercial lipids and hexadecylamin conjugated chlorin e6 (hCe6) via a templated self-assembly process, the yielded PEGylated nanophotosensitizer (hCe6@CaF-PEG) exhibits an effective loading efficiency to perfluoro-15-crown-5-ether (PFCE), a model perfluorocarbon molecule, and thus oxygen molecules. Upon intravenous administration, the obtained PFCE/hCe6@CaF-PEG can alleviate tumor hypoxia by working as an oxygen nanoshuttle. Together with local light emitting diode light exposure, photodynamic treatment with PFCE/hCe6@CaF-PEG can suppress the growth of primary CT26 tumors and unirradiated distant tumors, particularly when synergized with anti-PD-1 (aPD-1) immunotherapy to collectively reverse tumor immunosuppression. This work presents an effective strategy to potentiate photodynamic immunotherapy by concurrently reversing tumor hypoxia and immunosuppression.

Construction of multifunctional stimuli-responsive nanotherapeutics enabling improved intratumoral penetration of therapeutics and reversal of multiple-drug resistance (MDR) is potent to achieve effective cancer treatment. Herein, we report a general method to synthesize pH-dissociable calcium carbonate (CaCO₃) hollow nanoparticles with amorphous CaCO₃ as the template, gallic acid (GA) as the organic ligand, and ferrous ions as the metallic center via a one-pot coordination reaction. The obtained GA-Fe@CaCO₃ exhibits high loading efficiencies to both oxidized cisplatin prodrug and doxorubicin, yielding drug loaded GA-Fe@CaCO₃ nanotherapeutics featured in pH-responsive size shrinkage, drug release, and Fenton catalytic activity. Compared to non- responsive GA-Fe@silica nanoparticles prepared with silica nanoparticles as the template, such GA-Fe@CaCO₃ confers significantly improved intratumoral penetration capacity. Moreover, both types of drug-loaded GA-Fe@CaCO₃ nanotherapeutics exhibit synergistic therapeutic efficacies to corresponding MDR cancer cells because of the GA-Fe mediated intracellular oxidative stress amplification that could reduce the efflux of engulfed drugs by impairing the mitochondrial-mediated production of adenosine triphosphate (ATP). As a result, it is found that the doxorubicin loaded GA-Fe@CaCO₃ exhibits superior therapeutic effect towards doxorubicin-resistant 4T1 breast tumors via combined chemodynamic and chemo-therapies. This work highlights the preparation of pH-dissociable CaCO₃-based nanotherapeutics to enable effective tumor penetration for enhanced treatment of drug-resistant tumors.