Selective adsorption of surface-modified ferritin on a phase-separated polymer blend.

We compare the adsorption behavior of wild and surface-modified ferritin on a homopolymer blend of poly(desaminotyrosyl tyrosine dodecyl ester carbonate) (PDTD) and poly(epsilon-caprolactone) (PCL). Wild ferritin was alkylated by zero length cross-linking to surface carboxylate groups activated by water soluble carbodiimide (EDC). Modification was confirmed by anion exchange chromatography. All the adsorption experiments were done using deionized water (pH 5.8) and ultramicrotomed thin polymer films of thickness approximately 100 nm. Transmission electron microscopy shows a clear selectivity of alkylated ferritin adsorption onto the PCL phase while wild ferritin predominantly adsorbs onto the PDTD phase. We attribute these differences to the nature of the electrostatic interaction between the two types of ferritin and the polymer surface.