Affibody conjugation onto bacterial cellulose tubes and bioseparation of human serum albumin

We attached anti-human serum albumin (anti-HSA) affibody ligands on bacterial cellulose (BC) by EDC–NHS-mediated covalent conjugation and physical adsorption and demonstrate their application for tubular biofiltration of blood proteins. The BC fibrils were first modified by carboxymethyl cellulose (CMC) by incorporation of CMC in the BC culture medium, producing in situ a CMC–BC tubular network that was used as biofilter. Alternatively, BC carboxylation was carried out by alkaline TEMPO–NaBr–NaClO oxidation. The BC and modified BC, grown in the form of tubes or flat films, were characterized by using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and conductometric titration. Anti-HSA affibody conjugation onto carboxylated cellulose thin film was verified from sensogram data obtained by surface plasmon resonance (SPR). The HSA specific binding capacity of the carboxylated cellulose conjugated with anti-HSA via EDC–NHS was approximately eight-fold larger when compared to the carboxylated cellulose surface carrying physically adsorbed anti-HSA (81 compared to 10 ng cm⁻², respectively). Further proof of protein binding via anti-HSA affibody conjugated on tubules of CMC- and TEMPO-oxidized BC was obtained by fluorescence imaging. Specific binding of tagged HSA resulted in a linear increase of fluorescence intensity as a function of tagged HSA concentration in the contacting solution.