Photodynamic therapy(PDT)has emerged over the past decades as a very active field of research for medical applications.PDT can be defined as the administration of a nontoxic drug or dye known as a photosensitizers to a patient bearing a lesion,followed after some time by the illumination with visible light,which,with the presence of oxygen,leads to the generation of reactive oxygen species and consequently to cell death and tissue destruction [1].Among the basic elements such as light illumination and dissolved oxygen,photosensitizers play a key role in PDT treatment.Zinc(Ⅱ)phthalocyanine(ZnPc)has been suggested as the second-generation photosensitizer with the merits of high absorption in the red visible region,strong efficiency to produce singlet oxygen,ease of chemical modification,and low dark toxicity[2].However,the practical application of ZnPc is limited by poor insolubility,instability caused by the attachment from complex bioenvironments and nonspecific interaction with in vivo biomolecuels.As an alternative,encapsulation of photosensitizer molecules into nanoparticles(NPs)is very promising to circumvent the above shortcomings [3].In this work,ZnPc molecules were loaded into polymer/alkoxy silane hybrid NPs by previously developed reprecipitation-encapsulation method [4,5],which are further coated with poly-L-lysine(PLL)layers.Three types of polymer(polystyrene,poly(9-vinylcarbazole)and poly(9,9-dioctylfluorenyl-2,7-diyl)were utilized to optimize the loading capacity of NPs.Aggregation of ZnPc molecules in respective particles was studied,and influence on singlet oxygen quantum yield was investigated subsequently.The ZnPc-loaded NPs showed good biocompatibility and could be efficiently taken up by live cells.When applied to HepG2 cells,the ZnPc-loaded NPs exhibited high PDT efficacy.