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Zinc(II) phthalocyanines are favorable candidates as photosensitizers (PSs) for photodynamic therapy (PDT). However, zinc(II) phthalocyanines also suffer from poor water solubility and low tumor-targeting ability. In this study, a novel zinc(II) phthalocyanine tetra-substituted with sulphonates using “sulfur bridge” as the linkages was developed (ZnPc3), which exhibits high water-solubility and natural tumor targeting. Furthermore, ZnPc3 possesses red-shifted absorption and fluorescence spectra as compared to the unsubstituted zinc(II) phthalocyanine. In vivo fluorescence imaging indicates that ZnPc3 possesses an excellent tumor selectivity after intravenous injection without any help of targeting ligands or extra nanomaterials. The results of in vivo phototherapy evaluation suggest that ZnPc3-induced PDT could effectively inhibit the tumor growth in a mouse model.

To develop highly efficient photosensitizers for photodynamic therapy, herein a zinc(II) phthalocyanine-folate conjugate (PcN-FA) used to construct an activatable nanophotosensitizer (NanoPcN-FA) through a facile self-assembly. The self-assembled nanophotosensitizer (NanoPcN) without folate-modification was used as a negative control. After self-assembly, the photoactivities of NanoPcN-FA was quenched. The in vitro studies showed that NanoPcN-FA could be taken in by folate-receptor (FR)-positive SKOV3 cells and activated in the cells. It also exhibited slightly higher photocytotoxicity against SKOV3 cells than NanoPcN. Moreover, the competitive assay confirmed that the cellular uptake of NanoPcN-FA was through a FR-mediated process. Finally, the in vivo results indicated that NanoPcN-FA could target tumor tissue of S180 rat ascitic tumor-bearing mice due to the folic acid (FA) ligand, leading to a highly efficient antitumor photodynamic efficacy with the tumor inhibition rate of 95%.

Development of a photosensitizer that can achieve tumor specificity, improve therapeutic efficacy, and reduce side effects remains a challenge for photodynamic therapy (PDT). In this work, a pH-sensitive activatable nanophotosensitizer (SMSN–ZnPc1) has been elaborately designed, which could be readily prepared by using a functionalized zinc(II) phthalocyanine (ZnPc) to conjugate with stellate mesoporous silica nanoparticles (SMSNs) through an acid-sensitive hydrazone bond. Meanwhile, a non-activatable analogue SMSN–ZnPc2 has also been prepared as a negative control. The fluorescence emission and singlet oxygen generation of the photosensitizer are essentially quenched in the intact nanophotosensitizer. However, these properties of SMSN–ZnPc1 can be restored greatly both in acidic solutions and at the cellular level. More importantly, after intravenous administration, SMSN–ZnPc1 can also be selectively activated at the tumor site and exhibit efficient tumor growth inhibition in S180 rat ascitic tumor-bearing KM mice with negligible systemic toxicity. It thus may serve as a promising nanoplatform for cancer diagnosis and targeted PDT.

The interactions of bovine serum albumin (BSA) with five novel silicon (N) phthalocyanines(SiPcl-5) axially modified by nucleosides (cytidine, 5-N-cytidine, methyl cytidine, uridine and methyl uridine) derivatives were studied by fluorescence spectroscopy. The results show that there are strong interactions between these silicon phthalocyanines and BSA with a binding constant of (4.90-83.18) x 10(5) mol(-1) x L. Therefore, the non-covalent BSA conjugate of bis(2', 3'-O-isopropyl-cytidine-oxy) phthalocyaninatosilicon(IV) (SiPc1) was further been prepared. The molar ratio of phthalocyanine to albumin was found to be 1:1 for the obtained SiPcl-BSA conjugate. The absorption spectra of SiPc1 and SiPc1-BSA in the visible region have no significant difference, both showing an Q-band maximum at about 686 nm. It indicates that the spectroscopic characteristics of SiPc1 are not affected by binding to albumin. The SiPcl-BSA conjugate exhibits high photodynamic activity against human hepatoma cell line HepG2 with an IC50 value of 3.0 x 10(-7) mol x L(-1). By comparsion, SiPc1-BSA has a higher photodynamic activity than SiPc1 (in PBS formation, IC50 = 7.0 x 10(-7) mol x L(-1)), which can be attributed to its higher cellular uptake.