Synthesis And Application Of Tertiary Amine N-oxide Based Hypoxia Responsive Carriers

Macromolecular anticancer drugs or gene carriers have been extensively explored for cancer therapy.However,their actual therapeutic efficacies are not as good as expected.The main underlying reason is that they can hardly penetrate in the tumor,and particularly,can not reach the hypoxic regions in the tumor,where host highly aggressive tumor cells characteristic of low metabolism rate,insensitivity to the anticancer drugs.Therefore,the key challenge is how to design hypoxia-philic carriers.Tertiary amine N-oxide is a kind of electroneutral hydrophilic functional group with low interaction to the proteins.More importantly,it can be reduced in the hypoxia into tertiary amine,with a remarkable change in the hydrophilia and other properties.Thus a tertiary amine N-oxide containing polymer was synthesized.It was found that this polymer could penetrate to the hypoxic regions of tumor.So this polymer could deliver drugs to the hypoxic regions of tumor,thus could achieve better anti-tumor activity.In the first part we synthesized poly[2-(N,N-diethyl)ethyl methacrylate N-Oxide](OPDEMA)as a macromolecular drug carrier.The in vivo blood clearance results showed that OPDEMA had a long blood circulation the same as PEG.Endocytosis experiments showed that OPDEMA could enter the cell by micropinocytosis pathway like TAT(Trans-Activator of Transcription).In both in vitro tumor spheroid model and in vivo solid tumor model,OPDEMA exhibited hypoxia-targeting property.The in vivo anti-tumor experiments showed that the anti-tumor activity of OPDEMA-drug conjugate was higher than that of PEG conjugate.In the second part,N-oxide nitrogen mustard group was introduced into branched polyethylenimine(BPEI),forming a new kind of artificial macromolarcular drug.N-oxide nitrogen mustard group was stable in normoxic condition,while could be reduced to nitrogen mustard group,which is of high toxicity and anti-tumor activity in the tumor hypoxic region.In the third part,we developed a new macromolecular gene carrier by oxidizing the tertiary amine groups in the BPEI.BPEI is the golden standard in the non-viral gene carriers;however it has high toxicity because of its positive charges.The results showed that by oxidizing the tertiary amines in the BPEI,the electropositivity was greatly shielded.Thus,the toxicity of this carrier was greatly reduced,much lower than bPEI.In vitro transfection experiments showed that the transfection activity of oxidized bPEI was not greatly affected.In vivo transfection experiments showed that the oxidized bPEI had a higher transfection activity than bPEI in the tumor.