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Published online by Cambridge University Press: 01 February 2011
Well established quartz crystal microbalance 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 octakishexylthiophthalocyanine [(C6S)8PcCu] surface. Modification of phthalocyanine surface by protein coating can be useful for photo dynamic therapy or in biomedical devices purpose in order to increase biocompatibility. The adsorption kinetics on vertically oriented molecular stacks of phthalocyanines were 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 which was increased with concentration from 10-80% for BSA and IgG whereas it decreased from 20-1% for Lysozyme. Variation of viscosity and shear elastic modulus with concentration is 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.