The understanding of the adsorption process of biomolecules is very important for biological and engineering applications. Enolase is an enzyme of glycolytic pathway that catalyses a reversible conversion of 2-phosphoglycerate to phosphoenolpyruvate. In this work the adsorption behavior of enolase (2-phospho-D-glycerayte hydrolyase) onto hydrophilic silicon wafers and amino-terminated surfaces (APS) and onto hydrophobic polymer polystyrene (PS) was studied by means of null-ellipsometry. The adsorption kinetics of enolase onto these substrates presented three distinct regions: (i) a diffusion-controlled one; (ii) an adsorption plateau; (iii) continuous, irreversible, and asymptotic increase of the adsorbed amount with time. Atomic force microscopy (AFM) showed that well-packed entities formed an enolase biofilm, which might correspond to the monolayer formation. With increase of the adsorption time, aggregates appeared on the surface, suggesting multilayer formation. The early stages might be predicted by the random sequential adsorption model (RSA), while the cooperative sequential adsorption (CSA) model seems to describe regions ii and iii. No significant influence of ionic strength was observed on the adsorption behavior of enolase onto the present substrates. The adsorption isotherms show that enolase has no preferential adhesion onto hydrophilic or hydrophobic substrates. Contact angle measurements showed that PS surfaces became hydrophilic and silicon surfaces turned hydrophobic after the formation of the enolase biofilm. The study of the influence of pH on the enolase adsorption on silicon and APS surfaces showed that the higher adsorbed amount occurs when pH is close to enolase pI. Far from pI the enzyme solubility decreases and some repulsive forces come out, leading to a decrease in the adsorbed amount.

The influence of relative humidity (RH) during the film preparation on the surface morphology and on the material distribution of the resulting technical polymer blend films consisting of poly (methyl methacrylate) (PMMA) and poly (vinyl butyral) (PVB) is investigated by atomic force microscopy. Both pure polymers and polymer blends with different compositions of PVB/PMMA dissolved in tetrahydrofuran (THF) were used. Polymer films prepared under dry conditions (RH < 20%) are compared with those that have the same polymer composition but were prepared under increased humidity conditions (RH > 80%). The films consisting of the pure polymers showed a nonporous surface morphology for low-humidity preparation conditions, whereas high-humidity preparation conditions lead to porous PVB and PMMA films, respectively. These pores are explained as the result of a breath figure formation. In the case of the polymer blend films containing both polymers, porous or phase-separated surface structures were observed even at low-humidity conditions. A superposition of the effects of phase separation and breath figure formation is observed in the case of polymer blend films prepared under high-humidity conditions. Atomic force microscopy (AFM) images taken before and after the treatment with ethanol as a selective solvent for PVB indicate that PMMA is deposited on top of a PVB layer in the case of the low-humidity preparation process whereas for high-humidity conditions the silicon substrate is covered with a PMMA film.

Surfaces of pure titanium and Ti coated with cellulose acetate propionate (CAP) have been characterized by means of scanning electron microscopy X ray coupled with elemental microanalysis (SEM-EDS), ellipsometry, atomic force microscopy (AFM) and contact angle measurements. Coating Ti surfaces with CAP ultrathin films reduced original surface roughness. Surface energy and wettability of CAP covered Ti surfaces pure Ti surfaces were similar. The adsorption of lysozyme (LYZ), an antibacterial protein, onto Ti and CAP-coated Ti surfaces has been studied by means of ellipsometry and atomic force microscopy (AFM). The adsorption of LYZ was mainly driven by hydrophobic interaction between protein hydrophobic residues and CAP propyl groups. Pure Ti and CAP coated Ti surfaces presented no cytotoxicity effect and proved to be adequate substrates for cell adhesion. The biocompatibility of CAP coated Ti surfaces was attributed to the surface enrichment in glucopyranosyl residues and short alkyl side groups

Polymer blends are of increasing interest in the field of surface technology because they can be used to change or tailor the properties of surfaces for special application. In most cases not only the chemical nature of the components is important for the physical properties of the blend but also the components distribution on the blend surface. This distribution is strongly dependent on the adsorption energy of the polymers onto the substrate. According to the Flory-Huggins theory, the criterion for polymer miscibility in blends is that the average interaction parameter for a binary mixture of polymers, 12, must be less than a critical value cri, which is calculated from weight-average degrees of polymerization of the two polymers [1]. This parameter also describes the difference of the interaction energies between similar and different monomers. During the spin coating process the system tries to reach a state of low energy, indicating that the substrate surface and the vapor phase influence the wetting and dewetting of the substrate by the resulting polymer films. However, one should notice that spin-coated film structure may not correspond to the equilibrium one due to the rapid solvent evaporation during the spin coating process and to solvent effects [2].

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com quem tive o prazer de trabalhar. À Profa. Dra. Maria Cecília Salvadori pelo início do meu aprendizado em AFM Ao Prof. Dr. Thommas Schimmel pela oportunidade de estagiar nas instalações do Forchungszentrum Karlsruhe (Alemanha). Aos colegas deste mesmo grupo, Hartmut Gliemman, Stephan Wangheim e Mathias Müller, pelas dicas em AFM, sem as quais teria deixado de obter boa parte das imagens aqui apresentadas. Aos professores br. Michael Bruns (Forchungszentrum Karlsruhe, Alemanha) e Dr. Paul Rouxhet (Université Catolique, Bélgica) pelas análises em XP5. C) Ao Prof. Dr. Yoshio Kawano (IQ/USP) pelas análises de PAS. À Prof. Dra. Olga Zazuco Higa (IPEN/CNEN-5P) pelas irradiações das sluções poliméricas e imagens de MEV.