Influence of Adsorption Incubation Time on the Desorption of Proteins

The first experiments on the desorption of proteins revealed the complexity of the adsorption-desorption process. In fact, adsorption is principally amplified when performed above the rWT [11]. Desorption was found to be effective by lowering of the incubation temperature. In addition, the desorbed protein was directly related to the incubation time during the adsorption process above the rVPT as reported below in the case of cationic thermally sensitive latexes (Fig. 9).

As evidenced in Fig. 6, total desorption (below the Tvpt) was observed when adsorption was performed over a short incubation time using, for example, amino-containing polystyrene core poly(NIPAM) shell, whereas only 80% of the adsorbed amount was released when the adsorption was conducted over 2 h. A similar tendency has also been confirmed by Kawaguchi et al. [11] using human gamma globulin (HGG) protein adsorption onto anionic poly(NIPAM) microgel particles. The observed behavior has been discussed on the basis of two phenomena: (1) the possible diffusion and mechanical entrapment of proteins in the loosely cross-linked parts and (2) the denaturation of adsorbed proteins during the adsorption above the Tvpt and in the contact of low hydrated (or dehydrated) colloidal particles. Until now, this problem wasn't totally clarified and more work is needed.

FIG. 9 Protein desorbed amount onto amino-containing polystyrene core poly(NIPAM) shell vs. adsorption incubation time. Conditions: adsorption at pH 6.1 in the phosphate buffer and at 40°C, and desorption at 20°C in the same buffer [32].

In order to control and to understand the adsorption-desorption mechanism, the desorption processes were investigated in systematic studies as a function of various physical parameters.

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