The equipment of cellulose ultrathin films with BSA (bovine serum albumin) via cationization of the surface by tailor-made cationic celluloses is described. In this way, matrices for controlled protein deposition are created, whereas the extent of protein affinity to these surfaces is controlled by the charge density and solubility of the tailored cationic cellulose derivative. In order to understand the impact of the cationic cellulose derivatives on the protein affinity, their interaction capacity with fluorescently labeled BSA is investigated at different concentrations and pH values. The amount of deposited material is quantified using QCM-D (quartz crystal microbalance with dissipation monitoring, wet mass) and MP-SPR (multi-parameter surface plasmon resonance, dry mass), and the mass of coupled water is evaluated by combination of QCM-D and SPR data. It turns out that adsorption can be tuned over a wide range (0.6-3.9 mg dry mass m(-2)) depending on the used conditions for adsorption and the type of employed cationic cellulose. After evaluation of protein adsorption, patterned cellulose thin films have been prepared and the cationic celluloses were adsorbed in a similar fashion as in the QCM-D and SPR experiments. Onto these cationic surfaces, fluorescently labeled BSA in different concentrations is deposited by an automatized spotting apparatus and a correlation between the amount of the deposited protein and the fluorescence intensity is established.
The homogeneous conversion of cellulose dissolved in N-methyl-2-pyrrolidone/LiCl and 1-Nbutyl-3-methylimidazolium chloride with N-methyl-2-pyrrolidone, e-caprolactam, N-methyl-e-caprolactam, and N-methyl-2-piperidone in the presence of p-toluenesulphonic acid chloride was studied. Depending on the reaction conditions, novel cellulose esters with degree of substitution (DS) values ranging from 0.12 to 1.17 could be prepared. The structure of the amino group containing cellulose esters was elucidated by elemental analysis, FTIR-and NMR spectroscopy. NMR spectroscopy revealed an almost complete esterification of position 6 of the anhydroglucose unit at DS of 1. The conversion can be conducted between room temperature and 40°C, while side-reactions became predominant at 60°C. Starting with DS of 0.24, the samples were soluble both in water and dimethyl sulphoxide. The derivatives described are capable of forming polyelectrolyte complexes. The samples were stable at room temperature in aqueous solution at pH 2 and 7. Lower viscosities were found for samples with higher DS in aqueous solution at comparable molar mass.
Molecular assemblies, namely, polyelectrolyte complexes (PECs) composed of negatively charged xylan-based derivatives and a novel positively charged cellulose derivative (CN(+)), were used for interfacial modification of wood fibers by charge directed self-assembly. The adsorption process was studied using polyelectrolyte titration and elemental analysis. X-ray spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) were used as advanced techniques for the characterization of the modified fiber surfaces. The measurements revealed an intense interaction between the pulp fibers and PECs, and provided essential information for a better understanding of the adsorption process. The information gathered on this paper might contribute to the basis for the development of new value added products by the use of underutilized biomass.
The charging behavior of water‐soluble cellulose‐4‐[N‐methylamino]butyrate hydrochloride (CMABH) with different degree of substitution (DS) is investigated by polyelectrolyte titration at different pH values. Samples of high DS (0.92) and low DS (0.31) exhibit a decrease in positively charged groups from pH 2 (3.9 and 1.9 mmol g−1) to pH 9 (0.81 and 0.65 mmol g−1) due to the deprotonation of the ammonium groups. The stability of the ester linkage of CMABH is examined as a function of pH value and storage time (up to 28 d). A hydrolysis of the ester moiety is evident after 2 h at pH 8, which is also proved by ATR‐FTIR‐ and Raman spectroscopy.
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