Functionalization of nanoparticles for biological applications

Functionalization of metal oxide nanoparticles enables their use in biological applications via hybridization of biological molecules and modification of surface properties. This Ph.D. research is aimed at increasing knowledge of the process of metal oxide nanoparticle functionalization for biological applications. The achievements presented in this dissertation can be divided into three categories: (i) a fluorescence-based quantitative evaluation of surface coverage and bio-activity of antibodies immobilized on magnetic nanoparticles (MNPs), (ii) differential functionalization of SiO2/TiO 2 mixed nanoparticles via preferential binding of phosphonic acids to TiO2 and subsequent trimethyl silyl group binding to the remaining surface, and (iii) X-ray scattering (XRS)-mediated detection of peak shifts of a biological substrate, Escherichia coli ( E. coli), as a function of applied magnetic field strength and magnetic nanoparticle concentration in a cell growth medium.; In a study of MNP surface modification, quantitative evaluation of anti-mouse IgG binding on MNPs and bioactivity on MNPs was conducted via fluorescence assays. Nanosize gamma-Fe2O3 particles were hybridized with anti-mouse IgG via silane chemistry with 3-aminopropyltriethoxy silane and glutaraldehyde activation. A chemisorption isotherm via fluorescence assays demonstrated that immobilization of anti-mouse IgG can be stoichiometrically controlled with the surface coverage at saturation corresponding to 36% of the theoretical limit. The immobilized anti-IgG retains ∼50% of its bioactivity at saturation.; Differential functionalization of SiO2/TiO2 mixed nanoparticles was demonstrated via aqueous-phase preferential binding of phosphonic acids to TiO2 and subsequent binding of trimethyl silyl group to the remaining surface. SiO2/TiO2 mixed nanoparticles with three different mole ratios of Si/Ti together with pure SiO2 and TiO2 nanoparticles were used in comparative XPS study of differential functionalization. Differential functionalization of metal oxide-metal oxide mixed nanoparticles demonstrated herein adds a route to multifunctional nanoparticles.; An in situ XRS study of E. coli in applied magnetic fields up to 423 mT was performed. Two peaks, a sharp peak at q = 0.528 A-1 (1.189 nm) and a diffuse peak at q = 0.612 A-1 (1.027 nm), were detected in XRS of MNP-absent E. coli culture. The presence of SiO2/gamma-Fe 2O3 MNPs at 40 mg/L in E. coli growth medium changes the sharp peak to the lower side of q as a function of applied magnetic field strength, while the position of the diffuse peak is invariable. 362 mT was found to be a critical magnetic field strength, at which the sharp peak disappears. This study demonstrates magnetic field-assisted interactions between E. coli cell membranes and MNPs.