Construction And Functional Exploration Of Peptide-based Nanomaterials Targeting Mitochondria Of Tumor Cells

With the rapid development of society and economy,people’s material living standard is improving rapidly.Meanwhile,unhealthy diet and lifestyle are becoming more and more common.Food safety cannot be ignored.There is a close link between food and the occurrence of cancer,and about 30 percent of cancers are related to dietary factors.Cancer is one of the main causes of death of urban residents in China,which is a serious threat to the health of Chinese residents.Therefore,we urgently need advanced cancer treatment strategies to guarantee people’s healthy lives.In recent years,the field of nano-biomedicine has developed rapidly.Antitumor nanodrugs have special advantages such as good solubility,long blood circulation time and high bioavailability.However,the efficacy of nanodrugs in clinical trials is not significantly better than that of small molecule drugs.At present,the key problems of anti-tumor nanomedicine research mainly exist in two aspects:on the one hand,nanomedicine is difficult to cross the barrier of tumor pathology;on the other hand,the capacity of nanomedicine to kill tumor cells is limited.Mitochondria control the energy supply and redox balance of tumor cells.By destroying the mitochondria of tumor cells,tumor cells can be effectively killed.Peptide nanomaterials based on mitochondria targeted peptides have many advantages,such as good biocompatibility,strong mitochondrial binding force and significant anti-tumor effect,etc.Peptide nanomaterials have shown great potential in cancer treatment.Mitochondria-targeted peptide nanomaterials are highly lethal to tumor cells,but peptide nanomaterials are difficult to cross the barrier of tumor pathology.To address this problem,researchers need to develop more effective nanodrug delivery strategies.In recent years,the“in vivo self-assembly”strategy has attracted extensive attention,and its assembly-induced retention effect can significantly increase the accumulation and prolong the retention time of nanodrugs.By regulating the size and structure of nanomaterials,in vivo self-assembly strategy can make nanomaterials specifically reach tumor sites across the pathological barrier.In order to construct mitochondria-targeted anti-tumor peptide nanomaterials and enhance the accumulation of peptide nanomaterials in tumors,this paper made efforts from three aspects:active targeting enhancement of peptide nanomaterials,solid tumor penetration enhancement and in vivo assembly dynamic control.On the one hand,by combining targeted peptides with therapeutic nanomaterials,peptide nanomaterials with multilevel targeting ability were constructed.On the other hand,based on the strategy of"in vivo self-assembly",we designed two intelligently responsive peptide nanomaterials to achieve a better crossing of the pathological barrier,providing a new idea for efficient delivery of mitochondria-targeted peptide nanomaterials in tumors.The details are as follows:（1）Based on the mitochondrial targeting peptide CGKRK（CRK）and the pancreatic cancer cell targeting peptide PTPLLTK（PTP）,a biosignal processor（BSP）with the performance of photoacoustic imaging and mitochondrial targeted sonodynamic therapy was designed.The specific targeting ability of Panc-1 to pancreatic cancer cells was investigated.The binding ability of BSP to panc-1 cell mitochondria was investigated.Using tumor-bearing mice as a model,the mitochondrial targeted sonodynamic therapy and photoacoustic imaging performance of BSP were verified.（2）Based on mitochondrial targeted therapy peptide[KLAKLAK]₂,a nano-drug with mitochondrial targeted peptide with good permeability in solid tumors was developed.Pancreatic tumors are characterized by dense and impermeable stroma.We specifically developed a polymer-peptide conjugates PTPK with good permeability of solid tumors.In short,by linking functional peptide[KLAKLAK]₂,reactive oxygen response unit tk-PEG and molecular switch P18,a peptide nanomaterial PTPK with ultrasonic-responsive assembly ability was prepared.It self-assembled in situ at the tumor site through a cascade process under ultrasound so as to achieve deep penetration into the tumor tissue.The ultrasonic assembly capacity of PTPK was characterized by mass spectrometry and circular dichroism spectra in solution.The killing activity of PTPK tumor cells was investigated using Panc-1 cells as a model.Panc-1 cell clusters and subcutaneous tumor models in mice were established,and the permeability of tumor tissue was investigated by photoacoustic imaging in small animals.An orthotopic pancreatic cancer model was established to study its inhibitory effect on tumor growth.（3）Based on mitochondrial targeted therapy peptide[KLAKLAK]₂,"in vivo self-assembly"peptide nanomaterials with controllable assembly dynamics were developed.Specifically,PKK-S-PEG with in vivo self-assembly ability was prepared by linking functional peptide[KLAKLAK]₂,reduction-responsive unit PEG-SS-COOH,assembled peptide KLVFF and photothermal group Purpurin 18.The photothermal effect of Purpurin18 is activated by near infrared light,and the local temperature is changed to regulate the dynamic process of assembly and accelerate the process of self-assembly in vivo.The responsive assembly process of PKK-S-PEG in solution was studied by MALDI-TOF-MS,TEM,CD and FTIR.The kinetic process of PKK assembly was tracked by kinetic fitting.Hela cells were used as a model to study the killing ability of PKK-S-PEG on tumor cells.A mouse model of subcutaneous tumor was established,and the biological distribution and assembly dynamics of PKK-S-PEG were studied by in vivo fluorescence imaging and photoacoustic imaging.The antitumor activity of PKK-S-PEG was studied by monitoring the changes of tumor volume and tumor weight in tumor-bearing mice.