Preparation And Biological Application Of Responsive Nanomaterials

Responsive nanomaterials can undergo structural and property changes under stimulating conditions,which can be further used for controllable drug delivery,specific detection and diagnosis,and other biomedical research fields.In the biological application of responsive nanomaterials,responsive nanomaterials can be divided into biological endogenous stimuli(enzymes,redox,pH,hypoxic environment,etc.)responsive nanomaterials and exogenous stimuli(light magnetic field,ultrasound,etc.)responsive nanomaterials.Existing methods for preparing responsive nanomaterials include functionalization of nanoparticles and assembly of amphiphilic molecules..Although many responsive nanomaterials have been developed for fields such as imaging and drug delivery,there is still a great research gap in the preparation of "smart" responsive nanomaterials with better biocompatibility according to clinical needs.This thesis is dedicated to develope new types of responsive nanomaterials with different functions,confirm its response performance and evaluate its application potential in the fields of tumor imaging and drug loading through research.It includes the following three parts:(1)Caspase 3/7(Casp3/7)responsive nanomaterials were developed for proton(1H)magnetic resonance imaging(MRI)of apoptotic tumors.By using the method of solid phase peptide synthesis(SPPS),small molecules Ac-Asp-Glu-Val-Asp-Cys(StBu)-Lys-CBT that can respond to Casp3/7 were prepared(1).The small molecule sequence has an amino group on the Lys side chain that can participate in the reaction,and the small molecules were modified onto biscarboxyl polyethylene glycol(COOH-PEG-COOH)functionalized ferric oxide nanoparticles(Fe3O4)through an amide condensation reaction,thus preparing monodisperse nanomaterials Fe3O4@1 NPs with enzyme responsiveness.When Fe3O4@1 NPs were taken up by cells with high expression of Casp3/7 enzyme,under the combined action of reduced glutathione(GSH),inducing Fe3O4 NPs to form cross-linked aggregates,thereby greatly reducing the lateral relaxation time(T2)of protons(1H)in the surrounding water and enhancing magnetic resonance imaging effect.The response performance of Fe3O4@1 NPs was verified by the enzyme digestion experiment in the designed solution,and the responsive nanomaterials were prepared by establishing a cell model that highly expressed Casp3/7 and mouse apoptotic tumor models to further explorethe performance of magnetic resonance imaging of the prepared responsive nanomaterials.(2)Furin responsive nanomaterials were developed for accurate dual-mode(1H and 19F)magnetic resonance imaging of tumors.On the basis of the research in the previous work,by introducing 19F-containing 4-(trifluoromethyl)benzoic acid(TFMB)into the short peptide structure,and then according to the characteristics of the enzyme-cut substrate,the Furin-responsive molecule TFMB-Arg-Val-Arg-Arg-Cys(StBu)-Lys-CBT(1)can be prepared,the molecule was further modified on dicarboxylated polyethylene glycol(COOH-PEG-COOH)functionalized iron oxide nanoparticles(IONP)to prepare IONP@1 nanomaterials with Furin responsiveness.Due to the presence of the paramagnetic relaxation enhancement(PRE)effect,the 19F signal of the nanomaterials was initially on the "off" state.After being taken up by cancer cells which had high level of Furin,Furin induced IONP aggregation and enhancing the T2 signal of 1H MRI,simultaneously sheared the 19F-containing peptide away from IONP,the PRE effect was weakened,thereby "turning on" the 19F NMR/MRI signal.We then applied IONP@1 to detect the activity of Furin by constructing enzyme-digestion models in vitro and cell models that highly expressing Furin.In addition,zebrafish tumor models were constructed to confirm that IONP@1 can achieve accurate dual-mode(1H and19F)MR imaging of the tumor.(3)Degradable nanomicelles capable of releasing nitric oxide in response to light were developed for loading doxorubicin(DOX)to achieve synergistic anti-cancer.The reaction product was obtained by reacting o-nitrobenzaldehyde with bromoethanol,and the product was reacted with p-phenylenediamine to synthesize Schiff base,which was subsequently reduced by sodium borohydride(NaBH4)and nitrosated with sodium nitrite(NaNO2)to obtain the material(NORM)that could release nitric oxide(NO).Using NORM as a building block,a triblock copolymer of PEG-b-PNORM-b-PEG was successfully synthesized through a polycondensation reaction in the presence of hexamethylene diisocyanate(HDI)and polyethylene glycol monomethyl ether(mPEG-OH).Light responsiveness of N,N'-two nitroso para-phenylene diamine(DNP)derivatives has been integrated into three amphiphilic block copolymer in the middle of the block,so to get three block copolymer can be used as a macromolecular NO donor,PEG-b-PNORM-b-PEG three block copolymer with light responsive,PEG and light mediated NO release process will DNP into quinone diamine(QDI)derivatives,due to the spontaneous hydrolysis QDI part,make the polymer degradation.In vitro and in vivo experiments were designed to demonstrated that the NO release process could be activated under visible light irradiation.In addition,the micelles loaded with DOX was prepared,and the NO release-mediated micelle decomposition process was experimentally verified,and the synergistic anticancer performance of the responsive nano assembly in visible light was verified by simultaneously releasing NO and DOX.