Carbon Dots And Graphene Oxide-Iron Oxide Composite For Drug Delivery And Imaging

Carbon-based nanomaterials were considered to have great potential in thebiomedicine with the features of environment-friendly composition, low toxicity, andgood stability. Carbon dots and graphene are carbon-based nanomaterials discovered inrecent years With great potential in biomedicine.In this thesis, we investigate the biomedical applications of carbon dots andmagnetic nano-graphene for bioimaging and drug delivery.Oxidization of carbon nanotubes by a mixed acid has been utilized as a standardmethod to functionalize carbon nanomaterials for years.Here,the products obtained fromcarbon nanotubes and graphite after a mixed-acid treatment are carefully studied.Nearlyidentical carbon dot(Cdot)products with diameters of3–4nm are produced using thisapproach from a variety of carbon starting materials,including single-walled carbonnanotubes,multiwalled carbon nanotubes,and graphite.These Cdots exhibit strongyellow fluorescence under UV irradiation and shifted emission peaks as the excitationwavelength is changed.In vivo fluorescence imaging with Cdots is then demonstrated inmouse experiments,by using varied excitation wavelengths including some in thenear-infrared(NIR)region.Furthermore,in vivo biodistribution and toxicology of thoseCdots in mice over different periods of time are studied;no noticeable signs of toxicityfor Cdots to the treated animals are discovered.This work provides a facile method tosynthesize Cdots as safe non-heavy-metal-containing fluorescent nanoprobes,promisingfor applications in biomedical imaging.Two-dimensional graphene and its composite nanomaterials offer interestingphysical/chemical properties and have been extensively explored in a wide range offields in recent years.In this work,we synthesize a multi-functional superparamagneticgraphene oxide–iron oxide hybrid nanocomposite(GO–IONP),which is thenfunctionalized by a biocompatible polyethylene glycol(PEG)polymer to acquire high stability in physiological solutions.A chemotherapy drug,doxorubicin(DOX),was loadedonto GO–IONP–PEG,forming a GO–IONP–PEG–DOX complex,which enablesmagnetically targeted drug delivery.GO–IONP–PEG also exhibits strong opticalabsorbance from the visible to the near-infrared(NIR)region,and can be utilized forlocalized photothermal ablation of cancer cells guided by the magneticfield.Moreover,for the first time,in vivo magnetic resonance(MR) imaging oftumor-bearing mice is also demonstrated using GO–IONP–PEG as the T2contrastagent.Our work suggests the promise of using multifunctional GO-basednanocomposites for applications in cancer theranostics.In summary, our results show the promising of using fluorescent Cdots andmagnetic nano-graphene composites for bioimaging and drug delivery, and encouragefurther exploration of those low-dimensional carbon nanomaterials in biomedicine.