ICTON-MW'09 Fr2A.3

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Aspects of Correlation Between Structures, Properties and Bioapplications of TiO2 Nanotubes

Ioana Demetrescu1, Daniela Ionita1, Cristian Pirvu1, Diana Portan1, Claudiu Manole1 Florin Miculescu1 and Anisoara Cimpan2

1 University Politehnica Bucharest,polizu 1 Street Bucharest Romania 2 University Bucharest, Romania

Tel: (4021) 402 39 30 , e-mail: i_demetrescu@chim.upb.ro

ABSTRACT The present study is focussed on fabrication and characterization of TiO2 nanotubes as a function of anodizing conditions. The correlation between electrochemical stability and biocompatibility is based on the effect of fluoride existing in the anodizing electrolyte and revealed size dependent properties of nanotubes. Keywords: TiO2 nanotubes, (SEM), (AFM), biocompatibility.

1. INTRODUCTION The successful formation of TiO2 nanotubes using a nonsofisticated anodizing procedure, stimulated in the last decade a lot of studies[1-3] aims to potential applications of such nanotubes as a function of their geometry, which is a result anodizing conditions as various mixture of electrolytes, voltage, and time of procedure. More recently, controversies [2] regarding cell response to nanotubes structures.

2. EXPERIMENTAL PART Nanotubes elaboration. TiO2 self organized nanotubes structure was realized in inorganic mixtures of fluoride electrolytes as NaF, NH4, F HF, (NH4)2 SO4. etc., and in a hybrid organic- inorganic structure as floride-glycerol. Monitoring a large variety of voltage values between 6 and 80 and the time of anodizing procedures (2 – 5 hours), nanotubes with diameter from 40 to 400 nm were obtained.

Nanotubes characterization. Surface analysis including scanning electronic microscopy (SEM) atomic force microscopy (AFM), and contact angle were performed in order to obtain nanotubes diameter, roughness and hydrophilic/hydrophobic balance. Electrochemical stability in bioliquids was tested in physiologic serum and Hank solutions. Regarding biocompatibility of TiO2 nanotubes FT-IR and SEM analysis evaluated ability to built phosphate and fibroblast cell culture quantified the cell proliferation.

3. RESULTS and DISCUSSION A model of nanotubes growth was proposed and discussed based on fluoride effect under controlled voltage and time of anozing procedures. The surface features as roughness and hydrophilic/hydrophobic balance were compared for each obtained nanotube diameter. The roughness values were not very different, but for contact angle values despite the fact that all angles are under 90 º, a large variety of value were obtained from close to hydrophobic, to very hydrophilic, around 10 º. With the increase in voltage, the ordered structures shift from nanotubular aspect towards a porous distribution over the surface. Starting at 20 V applied voltage with an ordered aspect for nanotubes, the nanotubes are incorporated by porous structures of the same diameter at higher voltage. The electrochemical stability evaluated from cyclic voltametry indicated a size dependent stability in tested biliquids, the higher stability corresponding to smallest diameter. Potential bioapplications were discussed as a function of ability to built phosphate stratum, from MTT viability and actin cytoskeleton organization.)

4. CONCLUSIONS The biocompatibility results indicated a preference in terms of cell survival and adhesion for nanostructure TiO2 with a more hydrophilic character and for a specific diameter, corresponding to an optimum amount of fluoride amount, able to contribute to nanotube formation. The electrochemical data revealed that such features are connected with better stability and such conclusion open doors for cell use in various treatment..

REFERENCES [1] J.M. Macak, K. Sirotna, P. Schmuki: Anodic growth of self-organized anodic TiO2 nanotubes in viscous

electrolytes, Electrochim. Acta, vol. 52. pp. 1258-1264, 2006. [2] K.S. Brammer, O. Seunghan, C.J. Cobb, L.M. Bjursten, H. van der Heyde, Sungho Jin: Improved bone-

forming functionality on diameter-controlled TiO2 nanotube surface, Acta Biomater., in press. [3] D. Portan, D. Ionita, I. Demetrescu: Monitoring TiO2 nanotubes elaboration condition, a way for obtaining

various characteristics of nanostructures Key Engineering Materials, vol. 415, pp. 9-12, 2009.