Viscoelastic property and hydration level variations of proteins multilayer adsorbed on liquid crystal phthalocyanine th
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Viscoelastic property and hydration level variations of proteins multilayer adsorbed on liquid crystal phthalocyanine thin film Sharmistha Paul1, Tamara Basova2, and Asim K. Ray1 1 School of Engineering & Materials Science, Queen Mary College, University of London, Mile End road, London, E1 4NS, United Kingdom 2 Department of Coordination Compounds, Nikolaev Institute of Inorganic Chemistry, Lavrentiev pr., 3, Novosibirsk, 630090, Russian Federation ABSTRACT Well established quartz crystal micro balance with dissipation (QCM-D) monitoring technique has been applied here for investigation the adsorption kinetics of three different proteins (BSA, IgG, Lysozyme) on thin film of liquid crystal copper octakishexylthiophalocyanine [(C6S)8PcCu] surface. Modification of phthalocyanine surface by protein coating can be useful for photodynamic therapy or in biomedical device purpose in order to increase biocompatibility. The adsorption kinetics on vertically oriented molecular stacks of phthalocyanines was different for three proteins. Lysozyme reached to saturation quickly compare to BSA and IgG. Changes in resonance frequency and dissipation for three overtones were fitted with the Voigt viscoelastic model to calculate the shear viscosity and shear elastic modulus for the adsorbed proteins. Sauerbrey equation was used to calculate approximate adsorbed mass directly from frequency change. Adsorbed mass calculated from Voigt model was different from Sauerbrey equation. Hydration level of adsorbed protein layer was calculated from the difference in mass based on above two methods. It increased with concentration from 1080% for BSA and IgG whereas it decreased from 20-1% for Lysozyme. Variation of viscosity and shear elastic modulus with concentration was opposite for BSA, IgG than Lysozyme. Depending on the hydration levels, adsorbed BSA and IgG formed soft (viscoelastic) layer compare to rigid layer of Lysozyme on (C6S)8PcCu surface. INTRODUCTION The interaction occurring between proteins from aqueous solutions and solid surfaces are basic phenomena in different research area such as implant, biosensor, and biomedical application. Adsorbed proteins on artificial surface is expected to maintain good biofunctionality which depends on specific arrangement, conformation, hydration of proteins as well as surface chemistry, topography, and charge interaction [1]. Phthalocyanine based disk-like mesogens have been investigated for their potential use as dye, semiconductor, non linear optical materials, photodynamic therapy sensitive compound, chemical sensor. Disk like mesogen contains a flat rigid aromatic core substituted with relatively long and flexible peripheral chains. Due to cofacial stacking of aromatic ring cores, disk like molecules self organise into one dimensional supramolecular column [2]. Phthalocyanine with supramolecular organisation can be useful by protein coating for good biocompatibility or cell adhesive material in biomedical devices. Spin cast films of octakishexylthiophalocyanine [(C6S)8PcCu] ar
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