Nanometre-thin membranes, prepared by directed assembly within lipid bilayers, are capable of unhindered transport of ions while being impermeable to medium sized molecules.

Adsorption of human serum albumin (HSA) onto conducting polypyrrole powders, doped with chloride (PPyCl), dodecyl sulfonate (PPyDS), and tosylate (PPyTS), has been monitored in 0.1 M phosphate buffer saline (PBS) and pH 7.4 using UV-visible spectroscopy in conjunction with the depletion method. The decreasing trend of adsorption was PPyTS > PPyDS > PPyCl and was interpreted in terms of hydrophobic interactions. Electrochemically synthesized PPyCl, PPyDS, and PPyTS films were used as model surfaces for contact angle measurements. Both static, advancing, and receding water contact angle (θW) suggested that the PPyTS is the most hydrophobic polymer among the three under test. The simple measure of θW permitted qualitative interpretation of the adsorption trend in terms of hydrophobic protein-PPy interactions. The van Oss-Good-Chaudhury (VOGC) method was further used to determine the dispersive, acidic, and basic components of the surface free energy (γS d , γS + , and γS -, respectively) of the conducting polypyrroles. These components show that polypyrrole generally behaves as a strong Lewis acid. The three surface free energy components were subsequently used to assess the absolute hydrophobicity of the substrates (∆G1W1), that is, the PPy-PPy interaction in water, the trend of which is that of protein adsorption. More importantly, the VOGC theory permitted determination of ∆G1W2, the free energy of protein-PPy in water, that is, the extent of hydrophobic interaction forces. The decreasing trend of ∆G1W2 values (absolute) was found to be PPyTS > PPyDS > PPyCl. This is a quantitative evidence for the role of hydrophobic interactions at the protein-PPy interface. In the case of PPyTS and PPyDS, the acid-base force contribution was much more important than the van der Waals one. In contrast, for the HSA-PPyCl system, the van der Waals forces predominantly contributed to ∆G1W2.

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Polymer microspheres are used in diagnostics as “reagents” and as elements of diagnostic devices. In this paper we compare properties of microspheres with aldehyde, carboxyl and hydroxyl groups in their surface layers. Microspheres with aldehyde groups were obtained by radical emulsion copolymerization of styrene and acrolein and in sequential redox polymerization of pyrrole followed with radical polymerization of acrolein. Microspheres with hydroxyl groups were synthesized by radical emulsion copolymerization of styrene and α‐t‐butoxy‐ω‐vinylbenzyl‐polyglycidol macromonomer.­Microspheres with hydroxyl and carboxyl groups were synthesized by radical emulsion copolymerization of methylmethacrylate, acrylic acid and 2‐hydroxyethylmethacrylate. X‐Ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) revealed that microspheres had the core–shell morphology with surface layers enriched in polymeric units with reactive groups. The above mentioned microspheres were used as supports for adsorption and covalent immobilization of human and animal proteins–human serum albumin (HSA), gamma globulins (γG; human, rabbit and goat), human fibrinogen (Fb), and enzymes: glucose oxidase (GOD) and urease (Urs). The applicability of microspheres with attached antigens and/or antibodies (γG) for turbidimetric aggregation tests and for a new type of test based on changes of electrophoretic mobility of microspheres is discussed. Potential applications of microspheres with immobilized enzymes for the construction of biosensors are described. Copyright © 2003 John Wiley & Sons, Ltd.

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