Fabrication Of Nanocomposites And Their Applications In Bioanalysis

Unique characteristics of nanomaterials including small size effect, surface and interface effect, quantum size effect, as well as macroscopic quantum tunnel effect result in specific optical, thermal, electrical, magnetic, and mechanical properties. Many researchers concentrate their efforts on design and fabrication of multifunctional nanocomposites with magnetic, optical, electrical, catalytic properties for various applications in biomedicine, environmental science, food safety and other fields. This thesis focuses on the fabrication and functionalization of nanocomposites and investigates their potential applications in bioanalysis. The thesis is divided into the following six parts:1. Literature review. First, properties and applications of nanomaterials are briefly introduced. Second, fabrication and surface modification of three nanomaterials (carbon nanotubes, CdTe quantum dots and Fe3O4magnetic nanoparticles) involved in this thesis are summarized one by one. In addition, the applications of these nanomaterials-based nanocomposites in biomedical diagnosis, environment science, and criminal detection are reviewed in detail.2. Title:microarray biosensor based on carbon nanotubes/chitosan/polymer nanocomposites. It is very challenging to fabricate bioarrays to electronically high-throughput detect multiple analytes. This work innovatively fabricates an integrated printed circuit board (PCB)-based array sensing chip to simultaneously detect lactate and glucose in a biological sample, providing high sensitivity, high specificity and reproducibility. The novelty of the chip relies on a concept demonstration of inexpensive high-throughput electronic biochip, a chip design for high signal to noise ratio and high sensitivity by construction of positively charged chitosan/redox polymer Polyvinylimidazole-Os (PVI-Os)/carbon nanotube (CNT) composite sensing platform, in which the positively charged chitosan/PVI-Os is mediator and electrostatically immobilizes the negatively charged enzyme, while CNTs function as an essential cross-linker to network PVI-Os and chitosan due to its negative charged nature. The nanocomposite has a porous network structure with large specific surface area, which may contribute to the high loading capacity of enzymes. The developed sensing biochip possesses the following advantages:(1) low cost and easy for mass production;(2) the network structured carbonanotubes and biocompatible chitosan synergistically improve the performance of sensors, resulting from high enzyme loading capacity, good stability and high activity of immobilized enzyme.(3) Additional electrodes on the chip with the same sensing layer but without enzymes were prepared to correct the interferences to achieve high specificity and selectivity;(4) multiple analytes can be simutaneously detected with a single chip in high-throughput format. The developed sensing chip shows high sensitivity, good selectivity and reproducibility, providing great potential applications in biomedical diagnosis.3. Title:(CdTe QDs/PLL) layer-by-layer multilayer film and its antibacterial properties. CdTe quantum dots have many unique properties such as adjustable size-dependent fluorescence emission, broad excitation and narrow emission spectra, as well as good photochemical stability. In this thesis CdTe quantum dots are synthesized via hydrothermal approach with mercaptosuccinic acid, which contains negatively charged carboxyl groups, as protection ligands to improve the dispersability and stability.(CdTe QDs/PLL) multilayer films are then prepared via electrostatic layer-by-layer assembly of the nagtively charged QDs and positively charged polycation electrolyte (PLL). The thickness, fluorescence intensity and antibacterial activity of the film can be simply adjusted by controlling assembly layer numbers. The absorbance and emission of the film can be also tailored by changing QDs with various sizes. Using this method, the prepared (CdTe QDs/PLL) multilayer films have good photoluminescence and exciting antibacterial properties. It may have potential application as an antibacterial decoration coating.4. Title:Coprecipitation preparation of superparamagnetic iron oxide nanoparticles and their nanotoxicity Due to the easy manipulation with an external magnetic field and unique physiochemical properties, SPINOs have offered broad biomedical applications including high-resolution magnetic resonance imaging (MRI), in vitro bioseparation, magnetic targeted drug delivery, and hyperthermia therapy, In this work SPIONs were synthesized via chemical coprecipitation method with polyethylene glycol (PEG) as surfactant. The resultant nanoparticles were characterized with field emission scanning electron microscope (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). Results show that as-prepared nanocrystals are roughly spherical with reasonably uniform size from10nm to16nm in diameter; high saturation magnetization intensity (68.6emu/g) and zero coercivity and remanence. SPIONs-induced nanotoxicity and its molecular pathways were further investigated by protein microarrays with assistance of conventional methods. The experimental results reveal that<50μg/mL SPIONs don’t induce significant nanotoxicity, providing valuable information for biomedical applications. 5. Title:Fabrication of functional Fe3O4@SiO2-Au nanocomposites for latent fingerprints enhancement. Magnetic nanoparticles can be easily manipulated with an external magnetic field, providing a great potential for applications in latent fingerprint detection. In this work, magnetic Fe3O4nanoparticles were synthesized via coprecipitation method. A thin layer of SiO2was coated on surface of Fe3O4nanoparticlesto obtain Fe3O4@SiO2nanospheres. Gold nanoparticles were then attached onto the surface of aminated Fe3O4@SiO2nanoparticles, followed by reduction with formaldehyde to prepare Fe3O4@SiO2-Au nanocomposites. The as-prepared nanocomposites were employed for latent fingerprint detection, showing many advantages:(1) the small size of the prepared multifunctional nanoparticles gives better performance in comparison with conventional reagents;(2) SiO2coating significantly improve the dispensability and stability;(3) gold nanoparticles not only have good optical properties, but also provide favorable surfaces for amino acid and protein attachments;(4) Redundant magneticic nanoparticles can be easily removed by magnet brush, reducing their toxicity to operator;(5) The as-prepared nanocomposite can be universally used for latent fingerprinting detection on different substrates including glass, paper, plastic, etc.6. Title:Fabrication of magnetic and luminescent bi-functional Fe3O4@SiO2/FITC/Au nanocomposite for latent fingerprints enhancement. Luminescent magnetic nanoparticles with unique optical and magnetic properties have been widely used in biomedical fields, In this project, a novel Fe3O4@SiO2/FITC/Au luminescent magnetic bi-functional nanocomposite was prepared for latent fingerprinting detection. The bi-functional nanoparticles have the following advantages:(1) the luminescent feature can improve the detection performance especially on substrates with dark background;(2)(2) Amino acid and protein can be effectively adsorbed onto the surface of nanoparticles via gold nanoparticles as linker;(3) The nanocomposite has low toxicity and can be removed by magnet brush. The developed Fe3O4@SiO2/FITC/Au as a new fluorescent material shows superior performance for latent fingerprinting detection as compared with conventional magnetic powder and fluorescent materials, providing a great potential not only in penal investigation, but also in biomedicine and environmental science.