Protein attachment onto silica surfaces – a survey of molecular fundamentals, resulting effects and novel preventive strategies in CE

Abstract

This review addresses the fundamentals governing the adsorption of individual protein molecules onto the surface of fused-silica capillaries, the protein aggregation to adsorbate clusters and their final accretion to monolayers with subsequent stratification to protein multilayers. The attention in CE protein separation has primarily been focused on (i) tuning the BGE including the buffer type, ionic strength, pH and additives, (ii) tailored post-rinse procedures to detach adhered protein residues and (iii) the optimization of capillary wall shielding in order to reduce protein attachment. Improvements in protein separation as well as related adverse effects are mainly discussed on the basis of parameters known to become deteriorated in case of protein adhesion, e.g. repeatability of the EOF and of migration times, peak width, theoretical plate numbers, resolution and asymmetry factor. However, knowledge of the molecular principles controlling protein adsorption onto silica surfaces is indispensable for separation optimization. Furthermore, it facilitates troubleshooting and the interpretation of undesired concomitant phenomena. This review comprehensively discusses protein adsorption models derived from surface chemistry primarily in terms of their relevance for CE, clearly showing that the adsorption process in its complexity is only partially revealed by models, which address single or binary protein solutions. In a further section theoretical concepts and surface models are related to surface phenomena encountered in CE. The final part of the review surveys recent concepts for prevention of protein adhesion, thereby addressing capillary treatment, favorable buffer types, dynamic and adhesive semi-permanent coating strategies covering the literature from 2000-2008.

Modeling colloid deposition on a protein layer adsorbed to iron-oxide-coated sand

“…The outcome of these studies implies that protein adsorption conformation might be controlling the function of protein on colloid deposition. On the other hand, protein conformation was universally recognized to be influenced by its adsorption concentration (density) (Urano and Fukuzaki, 2000;Nakanishi et A , 2001;Stutz, 2009). Our recent study conducted with distinct protein adsorption concentrations showed that a single type of protein, Bovine Serum Albumin (BSA), may act either as colloid deposition site or inhibitor, depending on the adsorbed conformation (Flynn et al, 2012).…”

“…It is widely accepted that when adsorbed, BSA may first take a side-on conformation, at low adsorbed concentrations, which then change gradually to an end-on conformation, as more BSA masses adsorbed and lateral repulsion between adjacent BSA molecules became significant (Ramsden, 1995;Nakanishi et al, 2001;Stutz, 2009). In the absence of direct observation, the conformation of an adsorbed BSA could be estimated by comparing the adsorbed concentration with the limiting values proposed for a full side-on BSA layer and for a full end-on BSA layer, respectively (Revilla et al 1996;Nakanishi et al 2001;Terashima and Tsuji 2003;Tencer et al 2007;Togashi et al 2009: see Figure 4).…”

“…Experimental analysis above implies that end-on BSA may function as microsphere deposition sites. Ramsden (1995) and Stutz (2009) noted that end-on BSA may be generated by conformation change of side-on BSA, under the action of lateral compression. Our previous study suggested that deposition of…”

Sum Frequency Generation Spectroscopy in Biosensors Technology

“…First of all, the active biomolecule (protein, antibody or nucleic acid) must be immobilised onto the selected surface at the appropriate surface density while maintaining its activity. The way they are immobilised (physical adsorption Ekblad & Liedberg, 2010;Kidoaki & Matsuda, 2002;Nakanishi et al, 2001) versus covalent binding (Brady & Jordaan, 2009;Frasconi et al, 2010;Gandhiraman et al, 2009;Stutz, 2009)) and the surface substrate properties (wettability, roughness… (Gandhiraman et al, 2010a)) are, amongst others, parameters affecting biomolecule density and activity. Also, once proteins are attached to surfaces, different factors are affecting their biomolecular recogition (specific binding), i.e.…”

“…Characterisation techniques more easily applicable to a larger range of proteins were developped by Castner's (Xia et al, 2002;Wagner et al, 2003Wagner et al, , 2004Belu et al, 2003;H. Wang et al, 2004;Cheng et al, 2006;Baugh et al, 2010;Liu et al, 2010) and Aoyagi's (Aoyagi et al, 2008a, 2008b, 2009Okada et al, 2008) groups. They successfully adapted time-of-flight secondary ion mass spectroscopy (ToF-SIMS) in order to discriminate protein orientation by precisely probing ionised fragments peaks associated to particular amino acids (by using principal component analysis).…”