Preparation And Application Of ATP Responsive Hydroxycamptothecin Nanoparticles

Stimuli-responsive drug delivery systems have always been a hot topic in the field of anti-tumor research.Nanoparticles based on degradable biopolymer materials and small-molecule chemotherapy drugs plays an important role in Stimuli-responsive drug delivery systems.Because of the specific biological and chemical environment of tumor site,a variety of stimuli-drug delivery system based on the characteristics of the tumor microenvironment and tumor cell attracted researchers’ a lot of interests.As a matter of fact,the metabolism is out of control in the tumor tissue,and the ATP concentration at tumor site is extremely higher than that of normal tissue.Therefore,we prepared an ATP-switchable drug delivery system.A series of characterization was evaluated with both in vivo and in vitro assay.In this system,10-hydroxycamptothecin(HCPT)was modified by glutaric anhydride into an HCPT intermediate with carboxyl groups,and further reacting with l-arginine methyl ester to form a guanidyl HCPT small molecular prodrug(HCPT-Arg).Meanwhile,we used succinic anhydride to modify some of glucan hydroxyl groups on the main chain of dextran into carboxyl groups.Then,by reacting with taurine(Tau),most of the carboxyl groups were transferred into sulfo groups.The rest of the carboxyl groups combined with Ethyl L-phenylalaninate(L-phe),forming a dextran-grafttaurine-Ethyl-L-phenylalaninate copolymer(Dex-Tau-L-phe).In aqueous solution,the guanidine and sulfonic groups are positively and negatively charged,respectively.The HCPT-Arg can form a salt bridge by electrostatic complexation with dex-tau-l-phe.Meanwhile,the aromatic groups of HCPT-Arg and the phenyl group of Ethyl Lphenylalaninate can form a hydrophobic core by means of π-π stacking interaction to stabilize the nanoparticles(NP).The force of salt bridges between different ions is different.The strong anionic groups can replace the weak anionic groups to form a new salt bridge by destroying the original one.The force is represented by Kassoc.The Kassoc of phosphate groups(PO43-)and guanidine groups(Gu+)is obviously greater than that of sulfonate group(SO32-)and Gu+.Therefore,in the presence of PO43-,the stable salt bridge between SO32-and Gu+ will be replaced by PO43-.The concentration of ATP(adenosine triphosphate)in the tumor tissues is significantly higher than that of normal tissues.There are three PO43-in a single ATP molecule,which could replace SO32-to form a salt bridge with Gu+,thus replacing the HCPT-Arg small molecule prodrug from the dex-tau-l-phe polymer chain to achieve the responsive release of small molecular drug.In the experiment of NP in vitro,we observed the cumulative release curve of NP at different ATP concentrations,and found that with the increase of ATP concentration,the release of small-molecule drug from NP was accelerated.Meanwhile,DLS data showed that the adding of ATP to the system could accelerate the dissociation of NP and the release of small-molecule drugs.The therapeutic effect and survival curve of in vivo subcutaneous tumor bearing mice were observed.Small molecule drugs,namely HCPT and HCPT-Arg,showed no significant difference from the control group of PBS after 16 days of continuous treatment.The therapeutic effect of NP was greatly improved without severe weight loss of mice,which was significantly different from that of the small-molecule drug group(***p < 0.001).Meanwhile,tissue sections also proved that NP was far more effective in killing tumor cells than small-molecule drugs.With the help of salt bridge,this system can accelerate the release of smallmolecule chemotherapists in a high concentration of ATP,and improving the water solubility of HCPT.The new drug delivery system has not only a certain application prospect,but also some references for the design of new ATP response system.