Synthesis And In Vitro Anti-tumour Activity Of Polymeric Nanoparticles Encapsulated Silicon (Ⅳ) Phthalocyanine Bearing Poly(Aryl Benzyl Ester)Dendritic Substitutions

In this paper, three novel benzyl ester dendritic functionalities with different terminal groups (methoxycarbonyl, cyano and benzophenone) were firstly synthesized. Three novel silicon (IV) phthalocyanines bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities have been synthesized. They were di-[3-methoxycarbonyl-5-(4-methoxycarbonyl benzyloxy) phenoxy] silicon (IV) phthalocyanine (SiPc-E-E), di-[3-methoxycarbonyl-5-(cyano benzyloxy) phenoxy] silicon (IV) phthalocyanine (SiPc-E-CN), di-[3-methoxycarbonyl-5-(4-benzoyl-benzyloxy) phenoxy] silicon (IV) phthalocyanine(SiPc-E-BP). The di-(3-methoxycarbonyl-5-oxhydryl phenoxy) silicon (IV) phthalocyanine (SiPc-OH) was synthesized and regarded as control compound. The structures of ligands and phthalocyanines were characterized by IR,1H NMR, and ESI-MS methods.The UV/Vis spectra of silicon (IV) phthalocyanine bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities (SiPc-E-E, SiPc-E-CN, SiPc-E-BP and SiPc-OH) were studied by UV/Vis. It was found that this series of silicon (IV) phthalocyanine mainly existed as monomer in DMF. The natue of terminal functionalities has a certain effect on maximum absorption peak intensity, position, and molar absorption coefficient of this series of silicon (IV) phthalocyanine. The electron withdrawing group ability of different terminal functionalities is in the order:cyano> benzophenone> methoxycarbonyl. The stronger ability of electron withdrawing group is, the smaller the electronic density of Si-O of phthalocyanine ring, and the smaller red shift of the Q band. Compared with SiPc-OH, the maximum fluorescence emissions of SiPc-E-E, SiPc-E-CN and SiPc-E-BP were significantly enhanced and red shifted. This may be due to the conjugate system between benzyl substitutions and benzene ring, making π electron easy to be stimulated, and causing fluorescence intensity enhanced. Compared with SiPc-OH, the fluorescent lifetimes and fluorescence quantum yields of SiPc-E-E, SiPc-E-CN and SiPc-E-BP significantly enhanced. The above results may also due to the formation of π conjugate system between poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities and benzene ring. However, the natures of terminal functionalities have no significant influence on the fluorescent lifetimes of SiPc-E-E, SiPc-E-CN and SiPc-E-BP.The photoinduced electron transfer of this series of silicon (IV) phthalocyanine bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities were studied by UV/Vis and steady state fluorescence spectroscopic methods. Compared with SiPc-OH, the quenching constant of SiPc-E-E, SiPc-E-CN and SiPc-E-BP significantly enhanced. This also may because of the π conjugate system between the dendritic substitutions and benzene ring. The electrons could be transported from phthalocyanine to benzoquinone via this π conjugate system. The electrochemical behaviour of this series of silicon (IV) phthalocyanine bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities was studied by cyclic voltammetry (CV) method. The oxidation potential of denditic phthalocyanines were smaller than that of benzoquinone, which further demonstrated that electrons were transported from phthalocyanine to benzoquinone from thermodynamics.Four amphiphilic block copolymers with different hydrophilic and hydrophobic proportions were chosen as carriers to load a series of silicon (IV) phthalocyanine bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities, respectively. The polymeric nanoparticles loaded with dendritic phthalocyanines were prepared using water/DMF as co-solvent. The morphologies and particle sizes distribution of polymeric nanoparticles were studied by TEM and laser particle analyzer. They were sphere with diameters about50～100ran. The photophysical chemical properties of polymeric nanoparticles loaded with dendritic silicon (IV) phthalocyanines were studied by UV/Vis spectra, steady-state fluorescence and time-resolved fluorescence spectroscopic method. Comparing with free phthalocyanine, nanoparticles exhibited lower intensity in UV/Vis absorption and fluorescence emission, and shorter fluorescent lifetimes. The nanoparticles using amphiphilic block copolymer MPEG-PCL2with hydrophilic and hydrophobic proportions ca.1:3as carrier exhibited the highest drug load capacity and fluorescence intensity as well as the longest lifetime. Therefore, MPEG-PCL2was selected as an excellent drug carrier.The singlet oxygen generation rate, singlet oxygen generation rate constant and singlet oxygen quantum yields of a series of silicon (IV) phthalocyanines bearing poly (aryl benzyl ester) dendritic substitutions with different terminal functionalities and their corresponding polymeric nanoparticles were mearsured. The singlet oxygen generation rate, singlet oxygen generation rate constant and singlet oxygen quantum yields of a series of silicon (IV) phthalocyanines follow this order:SiPc-E-E> SiPc-E-CN> SiPc-OH> SiPc-E-BP. The singlet oxygen generation rate, singlet oxygen generation rate constant and singlet oxygen quantum yields of polymeric nanoparticles were significantly greater than the corresponding free phthalocyanines. This may because the formation of polymer nanoparticles, weakening the fluorescence intensity, increasing the intersystem conversion, accelerating the singlet oxygen generation rate. Therefore, the polymeric nanoparticles loaded with dendritic phthalocyanines exhibit excellent performance as the third generation photosensitizer.The glioma cell line U251was used to study the time-dependent pharmacokinetics of nanoparticles loaded with silicon (IV) phthalocyanine bearing poly (aryl benzyl ester) dendritic substitutions (SiPc-E-E/MPEG-PCL2). The results show that the maximum incubation time of SiPc-E-E/MPEG-PCL2was ca.4h. SiPc-E-E/MPEG-PCL2itself has no obviously toxicity effect on U251human glioma cells. In the SiPc-E-E/MPEG-PCL2-mediated PDT for U251human glioma cells, the optimum laser dosage is200J/cm2. In the the inhibition rate of U251human glioma cells increases as the SiPc-E-E/MPEG-PCL2concentration increases. The half maximal inhibitory concentration (IC50) is0.18mmol/L. SiPc-E-E/MPEG-PCL2-mediated PDT can achieve the antineoplastic therapeutic effect by inducing apoptosis.