Immobilization of DNA/RNA, onto various metal and metal oxide surfaces is of great importance for the development of future microarray, gene mapping, DNA sequencing, nanoparticle targeting, and sensor applications. Attachment of DNA to solid interfaces typically occurs through either electrostatic interactions or covalent bonds to functional groups introduced to nucleic acid termini. Previously, we and others have demonstrated that alkanephosphates and terminal phosphate groups present on nucleic acids play an important role in the interaction with group IV metal oxides such as zirconium and hafnium, providing a stable linkage to the surface. Titanium dioxide (TiO2), which is frequently employed in various nanoscale applications, belongs to the same group and similar interactions with phosphate are expected. Various adsorption studies have demonstrated binding of nucleic acids to TiO2 surfaces, although the influence of terminal phosphate versus electrostatic interaction (via the DNA/RNA backbone) on the surface interaction is unclear. The research presented here investigates the effect of nucleic acid length, presence of terminal phosphates, and differences between dsDNA and ssDNA on their binding to TiO2 nanoparticles. TiO2 nanoparticles (20 nm) were used to study the adsorption of Lambda DNA (˜48 kbp), and shorter (21 bp) ssDNA and dsDNA oligonucleotides with and without a 5’ phosphate group. Initial adsorption of DNA to nanoparticles was calculated via UV absorption. Results showed that all types of nucleic acids (Lamda DNA, ssDNA and dsDNA) initially bind to nanoparticles, independent of molecular weight single/double strandedness, or phosphorylation state. The total amount of DNA initially adsorbed to nanoparticles (ng/particle) differs between ssDNA and dsDNA, as well as the length of the DNA used. These results show that nucleic acid interactions with TiO2 nanoparticles are not dependent upon the presence of a terminal phosphate group. These results provide valuable data for future applications based on DNA-nanoparticle constructs including nanoelectronics, photovoltaics, and biotemplated synthesis of semiconducting materials.

Emulating the ECM microenvironment of natural tissue and understanding how such an environment affects integrin function is a major goal of regenerative medicine and tissue engineering. In this work we have combined laser and aerosol techniques to create nanoengineered substrates comprising calcium phosphate nanoparticles of well controlled size on atomically flat SiO2 layers. In our process, gas suspended calcium phosphate nanoparticles are generated by ablation of solid a hydroxyapatite target inside a tube furnace at 800-900°C in presence of Argon/H2O flow using a KrF excimer laser and deposited on a silicon substrate via electrostatic precipitation.

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and titanium dioxide (TiO2, titania) are of interest for bone-interfacing implant applications, because of their demonstrated osteoconductive properties. They were coated on the titanium implants using hydro-processes and investigated the in vivo performance. HAp coatings were formed on cp-titanium plates or rods by the thermal substrate method in an aqueous solution included 0.3 mM Ca(H2PO4)2 and 0.7 mM CaCl2. In the formation of carbonate apatite coating, CaHCO3 was added to the solution, and in HAp/gelatin and HAp/collagen composite coatings, acid-soluble collagen (Type I) was added. The coating experiments were conducted at 313-433 K and pH = 8 for 15 or 30 min. Titania films were formed on the titanium implants by anodizing at < 100 V in 0.1 M H2SO4, H3PO4, and NaOH aqueous solutions at 298 K. The properties for the coated samples were studied using XRD, EDX, FT-IR, and SEM. And the surface roughness of titania coatings was measured. In in vivo evaluations, the coated rod specimens were implanted in rats femoral for 2 weeks, the osteoconduction on them was evaluated. Two weeks postimplantation, new bone formed on the coated and non-coated titanium rods in the cancellous bone and cortical bone, respectively. Bone-implant contact ratio, RB-I, which was used for the evaluation of new bone formation, was significantly depended on the compound formed on titanium implants, and also the coating processes.

Electrophoretic deposition (EPD) coating of medical grade Ti-6Al-4V substrate with a novel silica-calcium phosphate nano-composite (SCPC) in the particle size range 50 nm-5 μm has been described. The influence of EPD parameters and thermal treatment on the coating homogeneity, thickness and adhesion strength has been studied. SEM analyses showed that EPD carried out in 5% (w/v) SCPC/ethanol suspension at 50 V produced a homogeneous coating on passivated Ti alloy discs. Tensile tests carried out to evaluate the adhesion strength at the ceramic/metal interface showed that the SCPC coating layer developed adhesion strength of 47 ± 4 MPa with Ti alloy after thermal treatment at 800 °C for 1 hr. SEM – EDX analyses of the fracture surface revealed that the presence of SCPC layer on the surface of the Ti alloy indicating high interfacial stability. Upon immersion of the SCPC-coated Ti alloy substrate in PBS, a surface biological hydroxyapatite layer was deposited suggesting bone bonding ability. The successful coating of SCPC on the Ti-6Al-4V has the potential to stimulate rapid fixation and lower stress shielding by enhancing the bone bonding ability of the implant.

Selective biomolecular functionalization of our all-(111) surface silicon nanowire (SiNW) biosensors using covalently linked alkyl- monolayers is demonstrated. Monolayers were made using a commercially available six member carbon precursor N-(5-Hexynyl) phthalimide and UV based hydrosylilation reaction. Contact angle and x-ray photoelectron spectroscopy (XPS) measurements were used to characterize the monolayer at different stages on planar Si (111) samples. Terminal amine groups on the monolayer surface were used for further conjugation with (+)-Biotin N-hydroxysuccinimide ester after deprotection of the phthalimide group with a methylamine solution. Selective biofunctionalization was demonstrated by reacting the SiNW-monolayer-biotin surface with 5 nm gold nanoparticles conjugated with streptavidin and subsequent high resolution scanning electron microscopy imaging.