Chlorin/Camptothecin Carrier-Free Nanoparticles:Preparation And Photo-Chemotherapy Synergistic Antitumor Evaluation

Photodynamic therapy(PDT)is a relatively new and non-invasive method for cancer treatment.The combination of PDT with chemotherapy based on nano-technology could achieve a synergetic antitumor effect and eradicate the tumor without recurrence caused by monotherapeutic modality such as chemotherapy only.In order to overcome most of the safety concerns from nano-carriers and improve the chemo-photodynamic synergistic antitumor efficacy,chlorin e6(Ce6)-a photosensitizer with porphyrin ring structure,and camptothecins(CPTs)-an insoluble anti-cancer drugs with polyphenyl ring structure,were co-assembled into novel carrier-free dual-functional nanoparticles in this project.Firstly,the driving forces for the self-assembly process of the carrier-free nanoparticles were studied to explore the self-assembly mechanism of nano drug delivery system(NDDS).Besides,the physiochemical properties of nanoparticles including particle size,morphology,stability,and ROS generation ability were evaluated.Finally,both the in vitro and in vivo combined chemo-photodynamic synergistic antitumor efficacy were assessed.The research contents in detail are as follows:(1)The preparation,in vitro and in vivo study of 10-hydroxyporphin(HCPT)/Ce6carrier-free nanorods(HCPT/Ce6 NRs):Firstly,the results from isothermal titration calorimeter(ITC)and molecular dynamics(MD)simulations verified that the number of binding sites of HCPT on Ce6 was exhibited as 3 on average,and the typical driving forces for the binding of two molecules include hydrophobicity and electrostatic interactions.Hence,combined with the results of ITC,MD and stability,the NRs with the molar ratio3:1(HCPT/Ce6=3:1)was selected as the optimum formula.The DLC(%)of the prepared HCPT/Ce6 NRs were HCPT 75.18%and Ce6 24.12%(the molar ratio of HCPT to Ce6was around 3:1)with size of around 165.9 nm and zeta potential of about-29 m V,together with uniform rods.The HCPT/Ce6 NRs showed good stability both in aqueous solution/at lyophilized state.Besides,the release rate of NRs in PBS was significantly slower than that of HCPT/Ce6 injections;High cellular uptake efficiency was obtained against 4T1 cell lines;Both in test-tube and intracellular singlet oxygen(¹O₂)generation capacity of the NRs were significantly enhanced compared to Ce6 injections.Finally,the dual-functional HCPT/Ce6 NRs exhibited an excellent in vitro/in vivo synergistic antitumor efficacy than those without laser and injections due to combined chemo-photodynamic therapy,while no potential systemic toxicity was detected.(2)The preparation,in vitro and in vivo study of 7-Ethyl-10-hydroxycamptothecin(SN38)/Ce6 carrier-free nanoparticles(SN38/Ce6 NPs):Firstly,the solid data and visual images obtained by chemical thermodynamic method and MD simulations supplied that the binding of SN38 and Ce6 in carrier-free nanoparticles was a static quenching process of complex formationas and the driving forces for self-assembly process of the NPs were primary hydrophobic interactions(?-?stacking)and subordinate hydrogen bonds.Besides,carrier-free SN38/Ce6 NPs were prepared via simple antisolvent precipitation method and exhibited relatively uniform morphology with a particle size of around 154.8 nm and a zeta potential of about-30 m V,together with good stability both in aqueous solution/at freeze-dried state.Furthermore,under laser irradiation,the in vitro cytotoxicity of NPs on4T1 cells was significantly enhanced compared with its injection and non-light nanoparticles;High cellular uptake efficiency was obtained against 4T1 cell lines;Both in test-tube and intracellular singlet oxygen(¹O₂)generation capacity of the NPs were significantly enhanced compared to Ce6 injections.Finally,a?85%inhibition rate of SN38/Ce6 NPs with laser was measured against 4T1 bearing BALB/c mice,which was prominently higher(P<0.05)than those without laser(?65%)and injections(less than20%),verified the excellent synergistic antitumor efficacy of the nanoparticles with minimal systemic toxicity.Therefore,as a promising therapeutic strategy,self-assembled Ce6/CPTs NPs are expected to maximize the anti-tumor efficacy of photo-chemotherapy.