Imaging Guided PTT-PDT Combination Therapy of Prostate Cancer Utilizing Ag2S-Fe3O4 Hybrid Nanoparticles and 5-ALA

Superparamagnetic iron oxide nanoparticles (SPIONs) and luminescent semiconductor quantum dots (QDs) have been at the center of biomedicinal research in the last decades, utilized for imaging, diagnostics, and therapy. SPIONs are known and utilized for magnetic resonance imaging (MRI), magnetic hyperthermia and photothermal therapy (PTT) and drug delivery [1, 2]. QDs, on the other hand, are very well established in the bioimaging and theranostics as an alternative to organic fluorophores due to their unique properties such as narrow emission bands, size-tunable and strong fluorescence and excellent photostability [3, 4]. Light-induced localized therapies, namely photodynamic therapy (PDT) and PTT, emerge as an alternative and/or complementary treatments along with conventional chemotherapy in the field of cancer therapeutics [5, 6]. Hybrid nanoparticles composed of magnetic-luminescent properties are highly appealing as they provide dual-imaging ability and enhanced photothermal properties, along with being excellent drug delivery vehicles [7]. In this study, luminescent-superparamagnetic Ag2S-Fe3O4 (AS-SPION) hybrid nanoparticles were developed via a simple ligand exchange method using 2-mercaptopropionic acid (2-MPA) coated AS QDs replacing lauric acid (LA) coating on SPIONs. Synthesis of both particles and the hybrids were previously reported [8, 9]. Final hybrids were then loaded with 5-aminolevulinic acid (5-ALA), which is an FDA approved natural precursor of PDT agent protoporphyrin IX (PPIX), to achieve imaging guided enhanced PDT-PTT combination therapy on prostate cancer cells. By loading 5-ALA to nanoparticles, its bioavailability and the efficiency of the combination therapy can be increased. The hydrodynamic size of the hybrids were less than 100 nm and they had strong emission in the medical imaging window (850-900 nm). The comparative PTT potential of the QDs vs. hybrids were initially investigated in the solution by irradiating the samples at 640 nm (215 mW) and 808 nm (400 mW) at different Ag concentrations. After determining the optimal PTT conditions in the solution, followed by in-vitro dark cytotoxicity of AS-2MPA QDs, AS-SPION hybrids, free ALA, and AS-SPION-ALA particles for LnCap, PC3 and Du145 cell lines, best treatment parameters were defined. Additionally, L929 cells were used to prove the non-toxic nature of the particles. PDT-PTT combination therapy was applied via co-irradiation of the cells with 640 and 808 nm laser at 300 mW and 700 mW power, respectively, for 5 minutes and cell death was evaluated with standard MTT assay. Additionally, cell death mechanisms were investigated in terms of ROS generation, apoptosis/necrosis and live/dead imaging. This study was focused on the determination of advantages of having hybrid nanoparticles providing dual-modality, enhanced phototherapy effect and the difference generated from combination therapy in comparison to monotherapies in the treatment of prostate cancer.