pH Dependence and Protein Selectivity of Poly(ethyleneimine)/Poly(acrylic acid) Multilayers Studied by in Situ ATR-FTIR Spectroscopy

Abstract

The selective interaction between polyelectrolyte multilayers (PEM) consecutively adsorbed from poly(ethyleneimine) (PEI) and poly(acrylic acid) (PAC) and a binary mixture containing concanavalin A (COA) and lysozyme (LYZ) based on electrostatic interaction is reported. The composition and structure of the PEM and the uptake of proteins were analyzed by in situ attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy, and the morphology and thickness were characterized by atomic force microscopy (AFM) and ellipsometry. The PEM dissociation degree and charge state and the protein adsorption were shown to be highly dependent on the outermost layer type and the pH in solution. High protein uptake was obtained under electrostatically attractive conditions. This was used to bind selectively one protein from a binary mixture of LYZ/COA. In detail it could be demonstrated that six-layered PEM-6 at pH = 7.3 showed a preferential sorption of positively charged LYZ, while at PEM-5 and pH = 7.3 negatively charged COA could be selectively bound. No protein sorption from the binary mixture was observed at pH = 4.0 for both PEM, when COA, LYZ, and the outermost PEI layer of PEM-5 were positively charged or the outermost PAC layer of PEM-6 was neutral. Furthermore, from factor analysis of the spectral data the higher selectivity was found for PEM-5 compared to PEM-6. Increasing the ionic strength revealed a drastic decrease in the selectivity of both PEM. Evidence was found that the proteins were predominantly bound at the surface and to a minor extent in the bulk phase of PEM. These results suggest possible working regimes and application fields of PEI/PAC multilayer assemblies related to the preparative separation of binary and multicomponent protein mixtures (biofluids, food) as well as to the design of selective protein-resistant surfaces.

Cast adhesive polyelectrolyte complex particle films of unmodified or maltose-modified poly(ethyleneimine) and cellulose sulphate: fabrication, film stability and retarded release of zoledronate

“…drugs, polyelectrolytes, proteins) at and in thin films, whose thickness is not exceeding around 300 nm [21,[27][28][29][30]. In the Figure 5 typical ATR-FTIR spectra recorded during ZOL release from thin PEC films of ZOL/CS/PEI-M-25 K-0.9-1:5 (a) and ZOL/CS/PEI-750 K-0.9-1:5 (b) for the initial (black) and end dry state (red) and for the contact to release medium (blue) after 5-1200 min (≈1 day) are shown.…”

Nanostructured Complexes of Polyelectrolytes and Charged Polypeptides

“…[15,16] attachment operated by the single-beam-sample-reference (SBSR) concept [17] (OPTISPEC, Zü rich, Switzerland) was used. The ATR-FTIR attachment was installed on the IFS 55 Equinox FTIR spectrometer (BRUKER-Optics GmbH, Ettlingen, Germany) equipped with globar source and MCT detector.…”

“…[16] Human serum albumin (HSA) adsorption at PEM-6 and PEM-7 films of PDADMAC/PLG was performed using 1 mg mL À1 HSA in 0.001 M MgCl 2 solution and measured during 1 h. MYO adsorption at PEM films was realized by injecting 1 mg mL À1 protein in PBS buffer (1 mg mL À1 ) above PEM-9 of PLL-289 000/PSS-70 000 and above PEM-9 of PDL-300 000/PSS-70 000, respectively. Both PEM films were stabilized by glutaraldehyde (GA) treatment as it was described therein.…”

Polyelectrolyte Complex Nanoparticles of Poly(ethyleneimine) and Poly(acrylic acid): Preparation and Applications

“…Thirdly, PEI is expected to have advantageous properties concerning drug uptake due to its high functional group density. Finally, we have been working for a long time also on PEL multilayers (PEM), composed of PEI/PAC, which serve as an interesting platform to study charge driven protein adsorption [20][21][22]. Interesting correlations between protein and drug interaction at PEM and at PEC systems are expected in the future.…”