56    International Journal of Biology Research ISSN: 2455-6548, Impact Factor: (RJIF 5.22) www.biotechjournals.com Volume 1; Issue 1; March 2016; Page No. 56-59 Kinetic study of the effect of Titanium Dioxide Nanoparticles on salivary peroxidase activity 1 Eaman A.S.Al-Rubaee, 2 Zainab A. Salman, 3 Suha T. Abd M.Sc, 4 Rasha A. Aziz M.Sc. 1 Assistant Professor, Biochemistry, Basic Science Dep., College of Dentistry, University of Baghdad. 2 Master student, Biochemistry, Basic Science Dep., College of Dentistry, University of Baghdad. 3 Assistant lectural, Oral physiology, Basic Science Dep., College of Dentistry, University of Baghdad. 4 Lectural, Basic Science Dep., College of Dentistry, University of Baghdad. Abstract Recently, understanding of the interaction of proteins with various nanomaterials has grown. The protein corona can detect not only how nanoparticles interact with cells but their biological effects and toxicity too. Structural and optical properties of the titanium dioxide nanoparticles (TiO2NPs) have been investigated using (UV-Vis) spectroscopy and Scanning Electron Microscope (SEM). The effect of TiO 2 NPs on salivary peroxidase activity was studied kinetically. The results in this study indicated that salivary peroxidase activated by TiO 2 NPs. the Vmax and Km for enzyme activity without nanoparticles were (133.33)U/L, and (0.133)mol/L respectively, and (714.3)U/L, (0.357)mol/L in the presence of TiO2NPs. Keywords: Peroxidase activity, TiO2 NPs, Saliva, and Kinetic study. 1. Introduction Over the past decade, nanotechnology has experienced rapid growth with its broad application in drug delivery, imaging and diagnosis [1-3] . Nanoparticles (NPs) are materials at sub micrometer scales (1-100 nm), so they may produce other advantages to the biomedical field through increased biocompatibility [4] . Metal oxide nanoparticles are safe for applications because they are more stable and have salient properties [5] . Titanium dioxide (TiO2) and ZnO are widely used as UV blockers in cosmetic lotions. TiO 2 nanoparticles are produced universal for multiplicity of bioengineering uses. They are also consumed as a material for orthopedic implants, and as a powder TiO 2 is commonly used as a whitener in toothpastes [6, 7] . Near 4.6 million tons of pigmentary TiO 2 are used yearly, this number is increasing as application continues to rise [8] . TiO2 NPs produced oxidative stress and apoptosis in animal cells [9] . Most of biological effects of NPs seem due to their interactions with proteins. The interaction of lysozyme with TiO2 NPs has been described [10] , the effect of TiO2 NPs on salivary ALP activity on gingivitis has been studied too [11] . Peroxidase (EC: 1.11.1.7; hydrogen peroxide oxidoreductase) is widely distributed in the living world and participated in several physiological processes. It's a hemeprotien catalyzing the oxidation by hydrogen peroxide of large number of compounds, including phenols, aromatic amines, thiosanisoles, halide and thyocianate ions, and fatty acids [12] . In human body, peroxidase founds in several body fluids; plasma, tears, and saliva in addition to other parts of cells acting as scavenger of free radicals in presence of hydrogen peroxide. The most important enzyme in the salivary antioxidant system, peroxidase, is represented in two peroxidase enzymes in saliva: salivary peroxidase secreted from the major salivary glands, mainly the parotid gland contributes 80% of oral peroxidase activity, and myeloperoxidase produced by leukocytes in inflammatory regions of the oral cavity contributes the remaining 20%of the oral peroxidase activity [13, 14] . Although the function of peroxidases is seen mainly in terms of causing the conversion of toxic H2O2 to H2O, their participation in other reactions, such as cell wall formation, lignification, the protection of tissues from pathogenic microorganisms, suberization, axing catabolism, defense, stress, etc., should be noted [12] . Until nowadays, there is no study about the effect of TiO2 NPs on salivary peroxidase activity kinetically. Then, it is very important to investigate the effect of these nanoparticles on salivary total peroxidase activity. Materials and Methods 1. Nanoparticles solution Titanium dioxide nanoparticles have been obtained from Hongwunanmter, china. TiO2 NPs solution was prepared by dissolving TiO2 Nano powder in 25% ethanol and 75% deionized water as a solvent. Absorbance spectra of NPs stock solution were measured by UV- VIS spectrophotometer. Structure and Nano size measurement of ZnO NPs powder were identified by the Scanning Electron Microscope SEM (Electronic Microscope Centre- College of applied Science, University of Technology, Iraq). 2. Salivary Total peroxidase assay Peroxidase activity was determined colorimetrically. Wide variety of hydrogen donors have been utilized in peroxidase assay systems. In this study an improved assay was adopted using 4- aminoantipyrine as hydrogen donor [15] . The activity is determined by measuring the increase in absorbance at nµ= 510 nm resulting from the decomposition of hydrogen peroxide per time of incubation. After adding 1.4 ml of (4— aminoantipyrine (2.5 mM) with phenol (0.17 M)) solution to 1.5 ml of (hydrogen peroxide (1.7Mm) in phosphate buffer (0.2 M) pH 7.0) solution, the reaction was initiated by addition of (100µl) of saliva with mixing. The increasing in the absorbance at 510nm, was calculated for 5 minutes, to obtain (∆A/min). One unit of enzyme activity represent the