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Compartmentalized- Bimetal Nanoclusters and Conducting Nanostructures for Functional Biophotonics and Drug Delivery Systems

Compartmentalized- Bimetal Nanoclusters and Conducting Nanostructures for Functional Biophotonics and Drug Delivery Systems
Other Titles
Ahmed Ali
Dong Woo Lim
Issue Date
This work focused on design, synthesis and evaluation of compartmentalized bimetal nanoclusters for SERS based biosensing and compartmentalized conducting nanostructures for electric-field responsive drug delivery systems. Compartmentalized anisotropic nanostructures combine different physical- and chemical features like chemical composition, charge, polarity, optical and magnetic properties on different compartments, and have the distinct properties at each compartment as well as collective physiochemical properties. Due to the diversity of their properties, these anisotropic nano-architectures are superior to isotropic micro- and nanoparticles and have several possible applications. However, it is still challenging to incorporate dissimilar physiochemical features into individual compartment where each is distinctly reactive to external stimuli, such as pH, temperature and electric field. Moreover, they can exhibit directional interactions between individual compartment for selective self-assembly, that could lead to superstructures with extraordinary properties and functions. To meet these challenges, we synthesized a series of plasmonic and compartmentalized nanostructures. We prepared a series of plasmonic composite nanostructures composed of two-dimensional graphene-polymer hybrids and metallic nanoparticles for SERS-based biosensing applications. We hypothesized that different surface modifications of nanoscale graphene with various polymer architectures could be useful to have plasmonic organic-inorganic composite nanostructures as advanced SERS nanoprobes for biosensing. Nanoscale graphene (NG) with poly(ethylene glycol) conjugates induced metal nanoparticle (MNP) clustering and an effect of concentration of Raman reporter, graphene, graphene size on SERS intensity was studied with excellent control on clustered nanostructures. Furthermore, graphene with stimuli-responsive polymer brushes controlled the loading density and clustering degree of MNPs on the graphene, resulting in stimuli-triggered enhancement of SERS signal. As a proof of concept that graphene-based plasmonic composite nanostructures would be usefulness as SERS nanoprobes, we showed the formation of sandwich-type immunocomplexes, which were composed of antibody-conjugated SERS nanoprobes and magnetic beads (MBs) as magnetic field-based separation agent in the presence of antigen. There was a linear correlation between Raman intensity and antigen concentration with minimal batch to batch variability. We also prepared a series of bimetallic Ag-Au nanostructures including (1) Ag-Au-Ag tri-compartmentalized nanorods (II) Au@Ag nanowires, (III) Asymmetric Au@Ag core shell nanoparticles, (IV) Au@Ag nanostars and (V). Thermoresponsive gold nanorods (GNRs) and thermoresponsive gold nanoparticles (GNPs) shaped tailored nanostructures. Bimetallic Ag-Au-Ag nanorods were prepared through directed overgrowth from either functionalized gold- decahedrons or gold nanorod. Directional clustering was achieved by covalent interaction through selective surface modification of the bimetallic Ag-Au-Ag nanorods compartments. On the other hand, shape-tailored nanostructure assemblies were composed of positively charged thermoresponsive GNRs and negatively charged thermoresponsive GNPs via non-covalent electrostatic interactions for biophotonics. Two different diblock copolymers composed of negatively charged poly(AAc) or positively charged poly(DMAEMA) and thermo-responsive poly(NIPAM) were prepared by RAFT polymerization, followed by aminolysis to have thiol end group of each the diblock copolymer. These diblock copolymers bearing thiol-end were attached to GNRs and GNPs via thiol bonding to form negatively charged GNPs-poly(AAc-b-NIPAM) and positively charged GNRs-poly(DMAEMA-b-NIPAM). The complexed nanostructures composed of GNPs-poly(AAc-b-NIPAM) and GNRs-poly(DMAEMA-b-NIPAM) showed highly enhanced physicochemical and optical performance as compared to those of the individual GNPs-poly(AAc-b-NIPAM) and GNRs-poly(DMAEMA-b-NIPAM), potentially due to the enhancement of the electromagnetic field at the interstices between the GNPs and GNRs. In final section, we describe how compartmentalized conducting nanostructures can be useful for electric field responsive dual drug delivery applications. One compartment was composed of positively charged polypyrrole (PPY), nanoparticles, while the other compartment comprised of negatively charged poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles. We used easy single-step emulsion polymerization method to encapsulate drug in these nanoparticles. These Oppositely charged conducting polymer nanoparticles (CP NPs) were separately encapsulated within the individual compartments of the biodegradable triblock copolymers, poly(l-lactide)-poly(ethylene glycol)-poly(l-lactide) (PLLA-PEG-PLLA) by electrohydrodynamic (EHD) co-jetting for dual drug release. The drug-encapsulated CP NPs within the anisotropic nano-architectures showed electric signal-responsive, decoupled drug release because CPs have an ability to display reversible redox in response to low electric signal. Moreover, the use of CP NPs was beneficial as they have a high surface-to-volume ratio, thus showing both excellent loading efficiency and stimuli-sensitive release profile. The drug release was found to be finely-controlled as a function of the number and strength of applied stimulus as well as size of CP NPs. Extension of this work involves preparation of thermoresponsive conducting nanostructure for dual stimuli drug release. A new class of compartmental anisotropic nanoarchitectures with selective incorporation of drug-loaded CP NPs into both compartments could be promising for advanced electrical stimulus-responsive therapeutic applications.
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GRADUATE SCHOOL[S](대학원) > BIONANOTECHNOLOGY(바이오나노학과) > Theses (Master)
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