The Synthesis And Biomedical Application Of The PH-Responsive Nanoparticles For The Intracellular Drug Delivery

In recent years,the rapid development of intelligent nanotechnology has given a tremendous impetus to the research of tumor-targeting agents.Among them,intelligent nanoparticles targeted at the tumor microenvironment have achieved good therapeutic effect in the targeting treatment of tumors.In this paper,a pH-sensitive intelligent nanocarrier was prepared by employing the tumor microenvironment's acidic property.By responding to the acidic pH,this nanocarrier could achieve the charge conversion and controllable penetration,thereby transporting the drug inside the tumor cells regularly and fixedly.The research contents are as follows:1.The traditional cell penetrating peptide Tat has a huge toxic on normal tissues due to its non-specificity.Therefore,we designed a PEG-grafted Tat-KK sequence(PEG-Tat-KK)by adding a long chain PEG and two lysine residues(KK)at the two terminals of Tat peptide,respectively,to solve this problem.Then,a pH-sensitive nanocarrier(DGL-PEG-Tat-KK-DMA)for the intracellular delivery of DOX was prepared by conjugating the designed sequence with the dendrigraft poly-L-lysine(DGL)and subsequently amidating it by 2,3-dimethylmaleic anhydride(DMA).In this nanocarrier,DGL acts as the skeleton and PEG-Tat-KK assists the nanocarrier to penetrate cell membrane.It's worth mentioning that DMA plays the most important role of reversible blocking agent.It can amidate the lysine residues in the Tat sequence(YGRKKRRQRRR)and the two additional lysine residues(KK)at the end of Tat.And,the amidation could further block the non-specific penetration of Tat and endow the nanoparticle with a negative shell,thus greatly improving the nanocarrier's targeting ability.In the tumor acidic microenvironment,the penetrating activity of Tat peptide and the positive charge of the nanoparticle could be recovered in time due to the fall off of DMA.After that,the nanocarrier could transport the drug inside the tumor cells.2.In the simulated physiological environment,this nanocarrier was spheric morphology and the particle size was ~120 nm-140 nm,which met the ideal size requirement of use in vivo.By investigating the drug loading efficiency and release behavior of the drug-loaded nanoparticles,itwas observed that this nanocarrier not only possessed high drug loading rate(74.6%),but also showed a pH-sensitive release performance.This performance could greatly reduce the drug's toxicity by avoiding its premature release during the process of delivery.Moreover,the zeta potential and cellular uptake changes of the nanocarrier in different p H verified that the pH-sensitive amide bonds could significantly improve the nanocarrier's targeting ability by controlling the surface charge and Tat's penetrating activity.The in vivo distribution and antitumor studies further manifested that the dual-targeting property of charge conversion and controllable penetration could greatly improve the specificity of the nanocarrier.Therefore,this nanocarrier could transport more drugs into the tumor site and efficiently inhibit the tumor growth.The above studies demonstrated that this nanocarrier possessed excellent physicochemical characteristics,as well as the dual-targeting property of charge conversion and controllable penetration.Furthermore,it could achieve the internalization on the basis of targeting,which enhanced the drug utilization to the maximum extent.Hence,this nanoparticle is an effective drug carrier for tumor targeting,and has great potential in the treatment of tumors.