MRI-Guided PHe-Activatable TAT Targeted Nanoparticle For Photodynamic Therapy In The Treatment Of Pancreatic Cancer

Objective Photodynamic therapy(PDT)had been applied in clinic for the treatment of a series of diseases,including skin carcinoma,carcinoma of esophagus,carcinoma of colon and so on.However,the sensitivity of pancreatic cancer,the effective effect of the therapy as well as the heterogeneity of tumor in patient undoubtedly pose a tremendous challenge to the further application of PDT in clinic.Nanoparticles simultaneously integrated the photosensitizers and diagnostic agents represent an emerging approach for imaging-guided photodynamic therapy(PDT).Based on this situation,we designed an extra-tumor cell acidity-activatable TAT targeting nanoparticle(DATAT-NP)which encapsulates the photosensitizer Chlorin e6(Ce6)and chelates Gd3+.This research may provide a new and an effective avenue for photodynamic therapy(PDT)in the precision treatment of pancreatic cancer in clinic.Methods We take the advantage of two di-block polymeric DATAT-PEG77-b-PCL25 and PCL45-b-PAEP35-Cya/DTPA that integrated the photosensitizer Ce6 and chelates diagnostic agent Gd3+ to form the nanoparticle(DATAT-NP),has successfully generated a tumor acidity-activatable TAT targeting nanoparticle which simultaneously for load the photosensitizers and diagnostic agents.According to the measurements of particle size and shape,characterizations of nanoparticles examined by methods of nuclear magnetic resonance(NMR),dynamic light scattering(DLS)and transmission electron microscope(TEM),respectively.We also detected the surface charge of nanoparticle in p H 7.4 or p H 6.5 condition with time variation.Furthermore,the profile of Ce6 releasement from nanoparticles in p H 7.4 or p H 6.5 PB buffer examined by HPLC.On the cellular level,we take the advantage of the methods as FACS,CLSM and HPLC for the evaluation of cellular uptake of such nanoparticles.Moreover,detection activator DCFH-DA which indicated the generation of ROS in cells after cellular uptake.MTT assay and Dead/Live staining assay were used for assessing the cytotoxic effect of photodynamic therapy in Bx PC-3 cell line.On animal level,HPLC and in vivo imaging methods for the observation of the blood circulation,pharmacokinetics and organ distribution,respectively.Mice were injected with different formulations,irradiated by 660 nm laser and the tumor size and the related parameters were recorded.Finally excised organs and tumors using H&E,TUNEL and PCNA assays for further analysis.Results We successfully developed a compact,spherical nanoparticle DATAT-NP which with particle size of approximate 100 nm,particle distribution of 0.22.Surface charge of nanoparticle is largely elevated at p H 6.5 and further bring about the promotion of cellular uptake of the nanoparticle and accordingly ROS raised after irradiation,cause a stronger cytotoxic effect.TAT modified with DA which could masking the positive group on TAT targeting ligand,could also efficiently avoids the rapid clearance by reticuloendothelial system(RES)in blood,resulting in the significantly prolonged circulation time in blood.Following the blood circulation,with the help of the EPR effect and slight acidic environment in tumor tissues,largely accumulation of PSs.On the other side,cationic groups on TAT has the greatest extent interaction with cells when DA detached from DATAT-NP,reaching the maximum of Ce6 and Gd3+ in cells and enlarged fluorescence and MR dual-modal imaging signals.As a result elevated the sensitivity in diagnosis and in vivo PDT therapeutic effect.This concept provides new avenues to design tumor acidity-activatable targeted nanoparticles for imaging-guided cancer therapy.Conclusion With the delivery by DATAT-NP,photosensitizer Ce6 and diagnostic agent Gd3+ has a good stability in blood circulation,showing the markedly promotion in pancreatic cells and a favorable safety profile to mice,has a powerful ability of inhibition in tumor growth.This research may provide a new and an effective avenue for photodynamic therapy(PDT)in the precision treatment of pancreatic cancer in clinic.This study provides new avenues for the fabrication of the next generation of nanomedicine for precisely and efficiently imaging-guided PDT treatment of cancer.