Ultrasmall pH-responsive silicon phthalocyanine micelle for selective photodynamic therapy against tumo

Targeted photodynamic therapy(TPDT)based on the photosensitizers responsive for tumor micr oenvironment is promising because of the better anti-tumor effect and less phototoxicity against normal tissue than the traditional PDT.Nanoparticle based stimuli responsive photo-sensitizers have been widely explored for TPDT.Based on the acidic microenvironments in solid tumors,an ultrasmall pH-responsive silicon phthalocyanine nanomicelle(PSN)(smaller than 10 nm)was designed for selective PDT of tumor.PSN had high drug loading efficacy(more than 28%)and exhibited morphological transitions,enhanced fuorescence and improved singlet∞x-ygen yield under acidic environments.PSN was renal dlearable and could rapidly accumulate and be retained at tumor sites,achieving a tumor-inhibiting ffect better than phthalocyanine micelle without pH response.Tumors of mice treated with PSN for PDT were completely ablated without recurrence.Thus,we have developed a phthalocyanine-based pH responsive micelle with excellent tumor targeting ability,which is expected to realize the selective PDT of tumor.

Evaluation of Silicon Phthalocyanine 4 Photodynamic Therapy against Human Cervical Cancer Cells in Vitro and in Mice

Background: Cervical cancer is the second most common cancer in women worldwide [1]. Photodynamic therapy has been used for cervical intraepithelial neoplasia with good responses, but few studies have used newer phototherapeutics. We evaluated the effectiveness of photodynamic therapy using Pc 4 in vitro and in vivo against human cervical cancer cells. Methods: CaSki and ME-180 cancer cells were grown as monolayers and spheroids. Cell growth and cytotoxicity were measured using a methylthiazol tetrazolium assay. Pc 4 cellular uptake and intracellular distribution were determined. For in vitro Pc 4 photodynamic therapy, cells were irradiated at 667 nm at a fluence of 2.5 J/cm2 at 48 h. SCID mice were implanted with CaSki and ME-180 cells both subcutaneously and intracervically. Forty-eight hours after Pc 4 photodynamic therapy was administered at 75 and 150 J/cm2. Results: The IC50s for Pc 4 and Pc 4 photodynamic therapy for CaSki and ME-180 cells as monolayers were, 7.6 μM and 0.016 μM and >10 μM and 0.026 μM;as spheroids, IC50s of Pc 4 photodynamic therapy were, 0.26 μM and 0.01 μM. Pc 4 was taken up within cells and widely distributed in tumors and tissues. Intracervical photodynamic therapy resulted in tumor death, however mice died due to gastrointestinal toxicity. Photodynamic therapy resulted in subcutaneous tumor death and growth delay. Conclusions: Pc 4 photodynamic therapy caused death within cervical cancer cells and xenografts, supporting development of Pc 4 photodynamic therapy for treatment of cervical cancer. Support: P30-CA47904, CTSI BaCCoR Pilot Program.

Synthesis, Photophysical Properties and DNA-Photocleavage Activity of Silicon Phthalocyanine Derivatives

Silicon phthalocyanine derivatives 1a and 1b were synthesized and characterized by UV, 1H-NMR and MS. The photophysical properties of the compounds in DMSO were investigated. The maximum absorption peaks of compounds 1a and 1b at the Q-band are 681 nm. With ZnPc (ΦF = 0.20, ΦΔ = 0.67) as a reference, the fluorescence quantum yield (ΦF) of 1a and 1b are 0.20 and 0.31 respectively, and the singlet oxygen quantum yield (ΦΔ) are 0.66 and 0.59 respectively. The DNA-photocleavage activities of compounds 1a and 1b were studied by gel electrophoresis. Compounds 1a and 1b possess good photocleavage activity to pBR322 DNA. The results demonstrate that compounds 1a and 1b are potential photosensitizers for tumor therapy.

Synchrotron radiation studies of the orientation of thin silicon phthalocyanine dichloride film on HOPG substrate

Thin silicon phthalocyanine dichloride films on HOPG were prepared and the sample was heated in the vacuum with laser. The thickness of the thin sample on HOPG was checked by X-ray photoemission spectroscopy. The orientation of the molecules in respect to the substrate plane was investigated by measuring the silicon K-edge near edge X-ray absorption fine structure （NEXAFS）. In the NEXAFS spectra of the thin sample, two clear peaks which were assigned to Is → σ^＊Si-N and 1s→ σ^＊Si-Cl appeared around 1847.2 eV and 1843.1 eV respectively. The intensities of the resonance peaks showed strong polarization dependence. A quantitative analysis of the polarization dependence revealed that the Si-N bond tended to lie down while the Si-Cl bond was out of the molecular plane.