Collagen adsorption kinetics

Figure 7 shows typical adsorption kinetics of mucin and collagen on polyethylene and mica surfaces followed by displacement of the protein solution by a buffer solution. It may be noted that collagen adsorption on polyethylene is five times higher than that of mucin and that the initial adsorption rates are protein diffusi-vity dependent. The diffusion coefficients for mucin and collagen were reported by us previously. At a protein solution concentration of 0.05 mg/ml they are respectively equal to 1.5 x 10"13 m. sec l and 1.0 x 10 12 m. sec l Uy ). 

Figure 7. Adsorption kinetics for mucin (Mu) and collagen (Col) on polyethylene (PE) and mica (Mi). Protein solution concentration 0.05 mg/ml. Temp. 20 C. Collagen adsorption from 0.2 M NaCl - 0.1 M CH3COOH buffer at pH = 2.75. Mucin adsorption from 10 3 M phosphate buffer with 0.15 M NaCl at pH = 7.2. Dotted lines and arrows indicate desorption and the amount after desorption.

However, not only the kinetics but also the morphology of precipitated HAp nanocrystals will be modified by structure-mediated (epitaxial) adsorption of organic constituents such as poly(amino acids) at prominent lattice planes of HAp. For example, adsorption of poly(l-lysine) on (0 0 1) planes causes formation of polycrystalline nanocrystals of HAp whereas adsorption of poly(l-glutamic acid) leads to precipitation of large flat micron-sized single crystals of HAp (Stupp and Braun, 1997). Similar relations have been found in experiments involving adsorption of recombinant human-like collagen (Zhai and Cui, 2006) and bovine serum albumin (BSA) (Liu et al., 2003) on hydroxyapatite surfaces. 

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