Novel protein-repellent and antimicrobial polysaccharide multilayer thin films

Abstract

Nanostructured and bio-active polysaccharide-based thin films were manufactured by means of subsequent spin-coated deposition of a regenerated cellulose (RC) layer and a 2,2,6,6-Tetramethylpiperidine-1-oxyl radical (TEMPO) oxidised cellulose nanofibril (TOCN) layer. The bio-activity of the bilayer was achieved by addition of chitosan (CS). The chitosan was either mixed with the TOCN (TOCN+CS) and deposited on the RC layer by spin-coating, or deposited on the RC and TOCN bilayer by pumping its aqueous solution with various pH over the surface of the bilayer. The water content of the thin films and the CS interactions with the bilayer during deposition were studied in situ by means of a quartz crystal microbalance with dissipation (QCM-D). The pH dependent charging behaviour of the TOCN, TOCN+CS and CS dispersions was evaluated by pH-potentiometric titrations. The surface morphology of the thin films was characterised by atomic force microscopy (AFM). The bio-activity of the thin films was evaluated by studying their protein-repellent properties in situ with a continuous flow of bovine serum albumin (BSA) by means of QCM-D and by evaluating their antibacterial properties in vitro against Staphylococcus aureus and Escherichia coli. These polysaccharide-based thin films are high value-added products because of their multifunctionality, high water absorbance capacity, protein-repellence and antimicrobial activity, and have the potential for medical application as a wound dressing material.

Influence of Different Pretreatments on the Antibacterial Properties of Chitosan Functionalized Viscose Fabric: TEMPO Oxidation and Coating with TEMPO Oxidized Cellulose Nanofibrils

“…The latter could be explained as a consequence of the oxidation process, which results in an efficient immobilization surface offering anchoring points for an enhanced attachment of CS molecules. In the case of TOCN coated viscose (Figure 3c), TOCN formed a thin polymer film embedding the fibers in a polymer coating, as we discussed in our previous work [14]. However, patches of polymer coatings detached from the fiber surfaces can be seen.…”

“…The best washing durability was evident for the TEMPO CV/CS sample; after three washing cycles, the total decrease in the chitosan content was about 48%, which left 0.92 g of chitosan/100 g cellulose, with no changes with further washings. The observed decrease in the chitosan content could be explained by the fact that a certain amount of chitosan was reversibly bound onto the cellulose surface [14].…”

“…The most likely cellulose–chitosan intermolecular interactions are based on H-bonds and Van der Waals forces. However, for more intense and irreversible binding between cellulose and CS, it is necessary to introduce carboxyl and/or aldehyde groups into/onto the cellulose, which are then potential anchoring sites for CS molecules [14]. Carboxylic groups of cellulose as host material can provide electrostatic attraction between them and CS as adsorbate, while aldehyde groups are an excellent choice because they can allow covalent binding of CS by forming a Schiff base [1].…”

“…Carboxylic groups of cellulose as host material can provide electrostatic attraction between them and CS as adsorbate, while aldehyde groups are an excellent choice because they can allow covalent binding of CS by forming a Schiff base [1]. These bounds, when present at the same time, may serve as a starting point for irreversible binding of CS onto cellulose [14].…”

“…Furthermore, biodegradability/biological stability and hydrophilic/hydrophobic properties of fibrous TEMPO oxidized cellulose and TOCN can be tailored by controlling carboxyl group content and their counterions [18,21]. In view of these facts, TOCN makes a very favorable substrate for coating textile materials based on cellulose, allowing the introduction of a high amount of functional groups (carboxyl and aldehyde) on their surface without deterioration of mechanical properties, and thereafter providing a stable CS adsorption [14,21,22,23]. According to a detailed literature review and the best of our knowledge, the pretreatments such as TEMPO oxidation as well as coating of viscose materials with TOCN followed by functionalization with CS and characterization of the product were not reported until now.…”