Functionalized magnetic nanomaterials for biomedical applications

Abstract

In recent, the progress in the development of magnetic nanoparticles-based therapies for various biomedical applications has drawn a great deal of interest due to their unique advantages. To be applied for biomedical application, the fabricated magnetic nanoparticles can be modified, or surface functionalized with other materials or functionalize groups including thiols, amines and carboxyls group for a wide range of applications. This thesis presented the functionalized magnetic nanomaterials with desired properties for the application in the biomedical field which can be attributed to the following sections. This thesis first introduced the amine-functionalized iron oxide silica (Fe2O3-SiO2) nanoparticles with core-shell structures and explore the application on enzyme immobilization. Size regulation of both the magnetic core and the porous shell was achieved, enabling the modulation of their magnetic properties and magnetic interactions. The amine-functionalized core-shell magnetic nanoparticles were immobilized on the gold surface, demonstrated the enhanced surface immobilization ability under the external magnetic field. The amine-functionalized iron oxide silica nanoparticles with core-shell structures could be effectively exploited to be applied in enzyme immobilization. Secondly, the thermosensitive magnetic nanomaterials with interpenetrating polymer network (IPN) structure. The Fe2O3-SiO2@poly (acrylamide-co-N, N-diethylacrylamide)/poly (N, N-diethylacrylamide) interpenetrating polymer network (IPN-pNIPAm@Fe2O3-SiO2) nanogels, possessing both magnetic and thermo-sensitive properties were successfully prepared. The preparation approach involved two steps, consisting of nanoparticle self-assembly and in-situ polymerization with monomers. This fabrication approach for IPN-pNIPAm@Fe2O3-SiO2 can provide a facile route for manufacturing the smart nanocomposite with long-term stability in aqueous solution and reversible swelling/deswelling stimuli-responsive property to achieve the multifunctional tasks in clinical therapy. Next, the thesis illustrated a sensitive and specific colorimetric analytical strategy for cancer cell detection based on folate-conjugated gold-iron oxide (Au-Fe2O3) composite nanoparticles. The synthesized Au-Fe2O3 composite nanoparticles demonstrated peroxidase-like activity and could catalyse the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of the hydrogen peroxide (H2O2). In this method, the Au-Fe2O3 composite nanoparticles were used as the signal transducer, and the conjugated folic acid (FA) acted as the tumour recognition tool. The generated colorimetric signals could be detected by the naked eye or via the UV-Vis spectrophotometer at an absorbance of 450 nm from the final yellow product. The folate-conjugated Au-Fe2O3 composite nanoparticles enabled the formation of a colorimetric-responsive multifunctional analysis platform with target recognition for cancer cell detection. Finally, the thesis reported a novel multifunctional nanoplatform based on cobalt ferrite (CoFe2O4)-graphene quantum dots (GQDs) for real-time monitoring of the drug delivery and fluorescence/MRI bimodal imaging of cancer cells. The DOX/GQD-CoFe2O4@SiO2/FA could use for real-time monitoring of drug release by detecting the Förster resonant energy transfer (FRET) signals, the GQDs served as the drug carrier and the donor in FRET model, while doxorubicin (DOX) served as the anticancer drug and the acceptor. The real-time monitoring of drug delivery via the corresponding changes in FRET was performed. Moreover, the MRI test of GQD-CoFe2O4@SiO2/FA was conducted. The fluorescence/MRI bimodal imaging could facilitate the transportation of drug delivery. Thus, the novel CoFe2O4/GQD could be a promising multifunctional nanoplatform for simultaneous diagnosis and therapy of cancer.