Construction And Preliminary Application Of A Near-infrared Light Responsive Temperature Sensitive Hydrogel Drug Delivery System

Research background According to the global cancer statistics in 2020,liver cancer is the sixth most common cancer in the world and the third most common cause of cancer-related death.There are 910000 new cases and 830000 deaths every year,accounting for 8.3% of all cancers[1],of which hepatocellular carcinoma(HCC)accounts for about 90% of primary liver cancer.The incidence rate of liver cancer is increasing worldwide.Between 1990 and 2015,the incidence of new liver cancer increased by 75%.China’s incidence rate and mortality rate still remain at a high level [2],which brings heavy burden to the society and families.Therefore,how to improve the therapeutic effect of liver cancer is of great significance.In clinical,ablation and TACE are common methods for the treatment of HCC,which have the advantages in less toxic and side effects and high treatment efficiency.Intratumoral injection,represented by percutaneous absolute ethanol injection,had been highly expected.It has the advantages of high efficiency,high cost-effectiveness and low technical difficulty.However,due to the uneven distribution,poor retention of drugs in the tumor,and spreading to the surrounding tissues and systemic circulation quickly,it gradually fades out of the ranks of the mainstream treatment methods.However,with the integration of materials science and medicine over the years,more and more clinical problems have been solved.The intelligent sustained release drug delivery platform represented by hydrogel is expected to overcome the problem of drug distribution and retention in intratumoral injection.Cisplatin adrenaline hydrogel(CDDP-EPI)has carried out clinical trials to prove its good drug release effect,drug safety and anti-tumor effect [3-5].At the same time,by giving different combination elements of the hydrogel system,it is possible to achieve the combination of two or more treatment methods,greatly improving the therapeutic effect.The combination of chemotherapy and photothermal therapy(CT-PTT)is an efficient synergistic treatment.Increasing the temperature can kill tumor cells and increase the sensitivity of tumor cells to chemotherapeutic drugs.The aim of this study is to construct an intelligent drug delivery platform based on the temperature sensitive intelligent hydrogel loading doxorubicin and gold nanoparticles.It can slow release doxorubicin at body temperature and solve the defects of drug distribution and retention in intratumoral administration;Under the irradiation of near-infrared light,the gold nano cage plays the role of photothermal therapy and promotes the release of doxorubicin,so as to realize the synergistic treatment of photothermal and chemotherapy.Based on clinical problems and previous research in materials science,We construct an intelligent drug delivery platform(Gel-GNC-Dox).It is a temperature sensitivity hydrogel loaded with doxorubicin and gold nano-cage.It can slow the release of doxorubicin at body temperature,and solve the defects of drug distribution and retention in intratumoral injection.Under near-infrared light,the gold nano-cage can act as photothermic therapy and promote the release of doxorubicin at the same time,achieve photothermal and chemotherapy combined treatment.Object We want to construct an intelligent temperature-sensitive drug-loading platform(Gel-GNC-Dox)to improve the shortcomings of intratumoral injection and combine photothermotherapy and chemotherapy to enhance the anti-tumor ability..Methods A temperature-sensitive hydrogel drug-loading system(Gel-gnc-dox)controlled by near-infrared(NIR)light was developed.Firstly,PLGA-PEG-PLGA(Gel)was synthesized by ring-opening polymerization,and characterized by 1H-NMR,molecular weight and distribution,and its temperature sensitivity was tested.Then GNC was synthesized and characterized by absorption spectra,zeta potential and particle size distribution.We explore the factors affecting the photothermal conversion ability.Finally,the gold nano-cage and doxorubicin were mixed into the hydrogel solution to form Gel-GNC-Dox.Then,we study the photo-thermal conversion ability of drug-loaded platform,the release of drug by near-infrared light,and the sustained release of drug by drug-loaded platform at body temperature.To study the anti-tumor activity and safety of Gel-GNC-Dox.In vitro,PBS,GNC and PLGA-PEG-PLGA were added to hepatoma cells for a period of time,then the cell viability was measured and the biosecurity of the main components of gel-GNC-dox was evaluated.Then,the groups of Group PBS,Group DOX,Group GNC + laser,Group GNC + DOX + laser and Group gel-GNC-Dox + laser were established respectively,the antitumor effects of single chemotherapy,single photothermic therapy,combined chemotherapy and photothermic therapy were compared.The laser is near infrared light,which is used to excite the heat of GNC.The photothermal effect of Gel-GNC-Dox in vivo was first verified.To compare the warming effect of laser on normal tissue and tumor tissue after administration,dynamic imaging under thermal imaging instrument is convenient for monitoring.Then,we studied the anti-tumor effect of Gel-GNC-Dox in nude mice.Group PBS,Group Dox,Group Dox,Group GNC + laser,Group Dox,Group DOX + laser,Group Gel-GNC-Dox and Group Gel-GNC-Dox + laser were established,the tumor volume,tumor weight,apoptosis and destruction of tumor tissue structure were used as anti-tumor criteria,and the weight of nude mice was used as safety criteria.Finally,we evaluated the drug storage in the Gel-GNC-Dox tumor by studying the residual amount of gold in the tumor.Results we have successfully constructed a Gel-GNC-Dox.It has good temperature sensitivity,good fluidity under 25 °C,convenient for intratumor injection,gel state at 37 °C,convenient for storing medicine and effective for preventing early drug escape.Under the condition of body temperature,the drugs in the hydrogel were released slowly through the pores due to the concentration difference between the inside and outside of the hydrogel.The GNC could activate the heating and control the explosive release of the drugs under the irradiation of near-infrared light to avoid the drug concentration being too low.The combined treatment of chemotherapy and photothermal therapy is realized simultaneously.In vitro,PLGA-PEG-PLGA(Gel)and GNC,the main components of Gel-GNC-Dox,were found to have good biosecurity and cytotoxicity of less than 10%.However,under the irradiation of laser,GNC caused intense tumor killing effect.Gel-GNC-Dox + laser group had the strongest anti-tumor effect,and the activity of tumor cells decreased significantly in vitro,about 36.7%.In vivo,we found that Gel-GNC-Dox + laser group had the smallest tumor volume and tumor weight.DAPI staining showed apoptosis and HE staining showed vacuolar necrosis.There was no significant change in body weight of nude mice in each group,which indicated that Gel-GNC-Dox and its components had better biological safety.Finally,the gold content in the tumor was 61.6%,indicating that Gel-GNC-Dox had a strong drug storage capacity.Conclusion we have developed an intelligent drug delivery system.It has the advantages of controlled drug release and overcomes the disadvantage of short drug retention time of intratumoral injection.At the same time,it has the synergistic effect of photothermal therapy and chemotherapy,and has a good anti-tumor effect.