| Objective:A personalized and long-acting local therapeutic platform combining photothermal therapy?PTT?and chemotherapy for the treatment of multidrug-resistant?MDR?colon tumor was developed.The system is designed to convert the hydrogel formed by poloxamer F127/F68 from a solution state to a gel state after injection of the drug into the tumor site,forming a three-dimensional structure drug depot,and then the photothermal agent polyethylene glycol?PEG?-coated gold nanorods?PEG-GNRs?and chemotherapeutic agent polyethylene glycol 1000 vitamin E succinate?TPGS?-coated paclitaxel?PTX?nanocrystals?TPGS-PTX NC?were immobilized in the three-dimensional structure.Under the irradiation of 808 nm near-infrared?NIR?laser,PEG-GNRs can exert quick local photothermal effect to kill MDR CRC in a short period of time,and avoid damage to surrounding healthy tissues;TPGS-PTX NC later provides a long-term sustained release of PTX to reduce the risk of local recurrence along with the P-gp inhibitor TPGS to reverse the drug resistance.Content:In this paper,the construction and characterization of the drug delivery system?GNRs-TPGS-PTX NC-gel?were completed,and the system was studied at the cellular level and animal level.The biosafety of the system was evaluated at the same time.Methods:Preparation of the system:Cetyltrimethylammonium bromide?CTAB?-coated GNRs?CTAB-GNRs?were synthesized by a seed-mediated growth method.To reduce the toxicity of GNRs,we replaced the CTAB surface of the GNRs with mPEG-SH.The TPGS-PTX NC was prepared by the nanocrystal stabilization method,and finally the GNRs-TPGS-PTX NC-gel was prepared by the cold method.Characterization of the system:The formation of PEG-GNRs was confirmed by the change of the maximum absorption wavelength in their UV-Vis-NIR spectra and the inversion of zeta potential,and the stability of PEG-GNRs was verified.The morphologies of the CTAB-GNRs,PEG-GNRs,TPGS-PTX NC,and GNRs-TPGS-PTX NC-gel were observed by transmission electron microscopy?TEM?.The gel formation temperature?GFT?and gelation time?GT?of the gel system were also investigated;the rheological behavior of the gel system was investigated by rheometer.The photothermal conversion effect of PEG-GNRs the in vitro release of PTX in the gel system and the in vitro erosion of the system were all investigated.Evaluation of the system at the cellular level:The cell killing capability of the GNRs-TPGS-PTX NC-gel system and their MDR reverse toward the resistant SW620 AD300 cells were both investigated by MTT assays.Evaluation of the system at the animal level:The SW620 AD300 tumor-bearing nude mice were used as animal models to investigate the anti-tumor effect of GNRs-TPGS-PTX NC-gel system by pharmacodynamic experiments.Systemic toxicity was evaluated by animal weight loss and the histological variations of the main organs?heart,liver,spleen,lung,and kidney?after treatment.Results:1.Construction and characterizations of the system.The maximum absorption wavelengths of CTAB-GNRs and PEG-GNRs in the UV-Vis-NIR spectra were 795nm and 802 nm,respectively.Compared with CTAB-GNRs,the maximum absorption wavelength of PEG-GNRs was slightly red-shifted.The zeta potentials of the CTAB-GNRs and PEG-GNRs in pure water were 29.2±4.2 mV and-14.6±0.9 mV,respectively.The TEM images showed that they were rod-like structures,and it can be seen that there was a thin film on the surface of PEG-GNRs,which is mPEG-SH polymer.The above results showed that CTAB was successfully replaced with PEG.The average length and average diameter of PEG-GNRs calculated by Nano Measure software were 45±5 nm and 12±2 nm,respectively,and the aspect ratio?length/diameter?is 4-5.Stability experiments showed that PEG-GNRs had good stability in 10%serum.TEM image of the TPGS-PTX NC also showed they had rod-like structures with a length of about 150-300 nm and a width of about 40 nm.The rheological experiment showed that the phase transition temperatures of blank gel,F127-PTX NC-gel,TPGS-PTX NC-gel,and GNRs-TPGS-PTX NC-gel were approximately 31.5oC,29.0oC,29.4oC,and 27.6oC,respectively.The gel time?GT?of the GNRs-TPGS-PTX NC-gel was approximately 50 s,and that of the other three groups were about 70-80 s.The results were almost identical to that from the tube inversion method.Drug release experiments showed that PTX can be released slowly and sustainably,and there is no burst effect.The cumulative release rate of PTX from the GNRs-TPGS-PTX NC-gel reaches about 40%at 144 h.PEG-GNRs showed good photothermal conversion effect under laser irradiation,but not affect the release of the drug.Gel erosion experiments showed that the GNRs-TPGS-PTX NC-gel system had a slow-erosion property,allowing the drug to be released slowly.2.Evaluation of the system at the cellular level.The results of MTT assay showed that the resistance index of PTX for SW620 AD300 cells was about 107 after treatment for 72 hours;the IC500 of GNRs-TPGS-PTX NC-gel decreased to 178-folds compared with that of free PTX toward to drug-resistant SW620 AD300 cells.These results demonstrated that the combination of photothermal therapy and chemotherapy from GNRs-TPGS-PTX NC-gel exhibited a strong synergistic cytotoxic effect against SW620 AD300 cells and reversed the MDR of PTX.3.Evaluation of the system at the animal level.In the in vivo pharmacodynamics experiments,after NIR laser irradiation,the mice treated with the GNRs-TPGS-PTX NC-gel showed similar tumor volume inhibition compared with that treated with GNRs-gel at the beginning.However,after 14 days,the tumor volume of the mice treated with GNRs-gel quickly increased,while that of the mice treated with GNRs-TPGS-PTX NC-gel remained controllable due to the long-term chemotherapeutic effect of TPGS-PTX NC.The mice treated with GNRs-TPGS-PTX NC-gel also showed no weight loss and obvious organ damages and lesions during the treatment,indicating a low systemic side effect profile and a good biocompatibility of GNRs-TPGS-PTX NC-gel.Conclusions:Overall,the GNRs-TPGS-PTX NC-gel may serve as a promising local therapeutic patch against MDR CRC with one-time dosing to achieve a long-term tumor control.The doses of PEG-GNRs and TPGS-PTX NC can be easily adjusted before use according to patient-specific characteristics potentially making it a personalized therapeutic platform. |
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