Matej Bračič

Adsorption of Carboxymethyl Cellulose on Polymer Surfaces: Evidence of a Specific Interaction with Cellulose

The adsorption of carboxymethyl cellulose (CMC), one of the most important cellulose derivatives, is crucial for many scientific investigations and industrial applications. Especially for surface modifications and functionalization of materials, the polymer is of interest. The adsorption properties of CMC are dependent not only on the solutions state, which can be influenced by the pH, temperature, and electrolyte concentration, but also on the chemical composition of the adsorbents. We therefore performed basic investigation studies on the interaction of CMC with a variety of polymer films. Thin films of cellulose, cellulose acetate, deacetylated cellulose acetate, polyethylene terephthalate, and cyclo olefin polymer were therefore prepared on sensors of a QCM-D (quartz crystal microbalance) and on silicon substrates. The films were characterized with respect to the thickness, wettability, and chemical composition. Subsequently, the interaction and deposition of CMC in a range of pH values without additional electrolyte were measured with the QCM-D method. A comparison of the QCM-D results showed that CMC is favorably deposited on pure cellulose films and deacetylated cellulose acetate at low pH values. Other hydrophilic surfaces such as silicon dioxide or polyvinyl alcohol coated surfaces did not adsorb CMC to a significant extent. Atomic force microcopy confirmed that the morphology of the adsorbed CMC layers differed depending on the substrate. On hydrophobic polymer films, CMC was deposited in the form of larger particles in lower amounts whereas hydrophilic cellulose substrates were to a high extent uniformly covered by adsorbed CMC. The chemical similarity of the CMC backbone seems to favor the irreversible adsorption of CMC when the molecule is almost uncharged at low pH values. A selectivity of the cellulose CMC interaction can therefore be assumed. All CMC treated polymer films exhibited an increased hydrophilicity, which confirmed their modification with the functional molecule.

Antifouling coating of cellulose acetate thin films with polysaccharide multilayers

In this investigation, partially deacetylated cellulose acetate (DCA) thin films were prepared and modified with hydrophilic polysaccharides with the layer-by-layer (LbL) technique. As polysaccharides, chitosan (CHI) and carboxymethyl cellulose (CMC) were used. DCA thin films were manufactured by exposing spin coated cellulose acetate to potassium hydroxide solutions for various times. The deacetylation process was monitored by attenuated total reflectance-infrared spectroscopy, film thickness and static water contact angle measurements. A maximum of three bilayers was created from the alternating deposition of CHI and CMC on the DCA films under two different conditions namely constant ionic strengths and varying pH values of the CMC solutions. Precoatings of CMC at pH 2 were used as a base layer. The sequential deposition of CMC and CHI was investigated with a quartz crystal microbalance with dissipation, film thickness, static water contact angle and atomic force microscopy (AFM) measurements. The versatility and applicability of the developed functional coatings was shown by removing the multilayers by rinsing with mixtures containing HCl/NaCl. The developed LbL coatings are used for studying the fouling behavior of bovine serum albumin (BSA).

Antimicrobial and antioxidant functionalization of viscose fabric using chitosan–curcumin formulations:

The purpose of this work was to develop new additive combinations between chitosan and curcumin in solutions as a fiber-coating. Diverse additive combinations between chitosan and curcumin in solutions were adsorbed onto viscose fabrics in order to reach the essential antimicrobial and antioxidant functionalization for medical textiles. The goal of this paper was to examine the adsorption of these two compounds as an additive formulation on viscose textile material as well as to analyze the desorptions of both substances from the fabric surface. Finally, the antimicrobial and antioxidant properties of viscose fabrics functionalized by chitosan–curcumin formulations were respectively examined. Curcumin as an adsorbate for textiles in combination with chitosan represents an added-value because of its anti-oxidative properties, and showing the potential to enhance existing antimicrobial performance of chitosan when applied using the preferred procedure.

Preparation of PDMS ultrathin films and patterned surface modification with cellulose

In this investigation, polydimethylsiloxane (PDMS) ultrathin films are prepared on a variety of solid surfaces by a simple and fast spin coating method, and patterned with the natural biopolymer cellulose via lithographic methods. Two surface patterning methods are developed to create coatings of hydrophilic cellulose, regenerated from trimethylsilyl cellulose (TMSC) on the PDMS thin films. In method 1, spin coated TMSC films on PDMS are covered with a lithographic mask and exposed to vapors of hydrochloric acid, which results in spatially separated cellulose pads surrounded by TMSC. Subsequent selective dissolution of TMSC with organic solvents results in a direct anchoring of cellulose pads on the PDMS. In method 2, PDMS thin films covered with a lithographic mask are exposed to UV/ozone, spray coated with TMSC and regenerated to give cellulose. The conversion of hydrophobic TMSC into hydrophilic cellulose coatings is confirmed by wettability and fluorescence measurements. The developed structures are highly transparent and stable in aqueous solutions (pH 3–9) and organic solvents. The surface properties of the polymer films are characterized using a quartz crystal microbalance with dissipation (QCM-D), ellipsometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact angle and streaming potential measurements.

A novel synergistic formulation between a cationic surfactant from lysine and hyaluronic acid as an antimicrobial coating for advanced cellulose materials

Abstract In this investigation, a novel coating for viscose fabric surface modification was developed using a synergistic formulation between a natural antimicrobial cationic surfactant from lysine (MKM) and a biopolymer hyaluronic acid (HA). The interaction between MKM and HA in aqueous solutions, as well as the interactions between their synergistic formulation (HA-MKM) and viscose fabric (CV) were studied using pH-potentiometric titrations’, turbidity measurements, the Kjeldahl method for the determination of nitrogen amounts, attenuated total reflectance fourier transform infrared spectroscopy, and scanning electron microscopy. The hydrophilic and antimicrobial properties of the functionalised CV were examined in order to evaluate its usages for medical applications. The results of the interaction studies showed that MKM and HA interact with each other by forming a precipitate when the binding sites of HA are saturated. The precipitate has a slightly positive charge at neutral pH due to excess binding of the MKM to HA. The excess positive charge was also detected on CV coated with HA-MKM. This was proven to be very beneficial for the antimicrobial properties of the functionalised CV. The antimicrobial tests showed exceptional antimicrobial activity of the functionalised CV against Escherichia Coli, StaphylococcusAureus, StreptococcusAgalactiae, Candida Albicans, and Candida Glabrata, making the CV fabric highly interesting for potential use in medicine.

Interaction of Sodium Hyaluronate with a Biocompatible Cationic Surfactant from Lysine: A Binding Study

Mixtures of natural and biodegradable surfactants and ionic polysaccharides have attracted considerable research interest in recent years because they prosper as antimicrobial materials for medical applications. In the present work, interactions between the lysine-derived biocompatible cationic surfactant N(ε)-myristoyl-lysine methyl ester, abbreviated as MKM, and the sodium salt of hyaluronic acid (NaHA) are investigated in aqueous media by potentiometric titrations using the surfactant-sensitive electrode and pyrene-based fluorescence spectroscopy. The critical micelle concentration in pure surfactant solutions and the critical association concentration in the presence of NaHA are determined based on their dependence on the added electrolyte (NaCl) concentration. The equilibrium between the protonated (charged) and deprotonated (neutral) forms of MKM is proposed to explain the anomalous binding isotherms observed in the presence of the polyelectrolyte. The explanation is supported by theoretical model calculations of the mixed-micelle equilibrium and the competitive binding of the two MKM forms to the surface of the electrode membrane. It is suggested that the presence of even small amounts of the deprotonated form can strongly influence the measured electrode response. Such ionic-nonionic surfactant mixtures are a special case of mixed surfactant systems where the amount of the nonionic component cannot be varied independently as was the case for some of the earlier studies.

Characterization of viscose fibers modified with 6-deoxy-6-amino cellulose sulfate

Cellulose viscose fibres were functionalized by novel amino cellulose sulfates (ACS), namely 6-deoxy-6-(ω-aminoethyl) amino cellulose-2,3(6)-O-sulfate (AECS), and 6-deoxy-6-(2-(bis-N′,N′-(2-aminoethyl)aminoethyl)) amino cellulose-2,3(6)-O-sulfate (BAECS). In this way an amphoteric characteristics were introduced onto cellulose viscose fibers which is extremely important by fiber applications. Whilst cellulose fibers possess only negligible carboxyl groups’ content, the coating of fibers by AECS and BAECS, respectively, introduces new functional groups to the fibers; as positively-charged amino groups and negatively-charged sulfate groups. The typical functional groups within the non-coated fibers, as well in the ACS-coated fibers, were characterized by means of X-ray photoelectron spectroscopy, conductometric-, potentiometric and polyelectrolyte titrations, as well as conventionally by the spectroscopic methylene-blue method. The electro-kinetic behavior was evaluated by measuring the zeta-potential of the fibers as a function of pH. The amounts of the positive-charges (introduced protonated amino groups) determined by potentiometric titration agreed with the amounts of the positive charges determined by conductometric titration. The total amounts of negatively-charged fiber groups (sulfate and carboxyl) determined by polyelectrolyte titration were 38.8 and 32.1 mMol kg−1 for AECS-Vis and BAECS-Vis, respectively, and these results were in accordance with the conventional methylene-blue method.

Protein-repellent and antimicrobial nanoparticle coatings from hyaluronic acid and a lysine-derived biocompatible surfactant

Biofilm formation triggered by uncontrolled protein adsorption, on medical devices is the leading cause of catheter-associated urinary tract infections (CAUTI) during implantation. Herein, we report a water-based, green and one-step strategy to functionalize surfaces of silicone catheters, poly(dimethylsiloxane) (PDMS), with antifouling and antimicrobial substances to avoid uncontrolled protein adsorption and microbial attachment. A novel synergetic formulation consisting of an anionic glycosaminoglycan (hyaluronic acid, HA) and a lysine-derived biocompatible cationic surfactant (Nε-myristoyl-lysine methyl ester, MKM) was prepared, resulting in the formation of nanoparticles (NPs, ca. 100-250 nm). Besides their high stability and long-lasting hydrophilicity in ambient and aqueous environments for 60 days, the nanometric layers (48 ± 3 nm) of HA-MKM NPs on PDMS showed no adsorption of BSA and lysozyme and substantially lower adsorption of fibrinogen as revealed by a quartz crystal microbalance with dissipation (QCM-D). In vitro antimicrobial test with S. aureus, E. coli, P. aeruginosa, P. mirabilis, C. albicans microbes under dynamic conditions revealed that the microbial growth was hampered by 85% compared with unmodified PDMS. Given the multiple functionalities, charges and diverse physiochemical properties of polysaccharide-lysine-based surfactant mixtures, this approach can be easily extended to the development of novel coatings on other silicone-based materials, thereby broadening potential applicability of PDMS-based biomaterials/devices in microfluidics, diagnostic biosensors and others.

Antimicrobial efficiency evaluation by monitoring potassium efflux for cellulose fibres functionalised by chitosan

Abstract As there is a large gap in the field of fibre microbiological testing, the successful establishment of appropriate techniques is extremely appreciated. Antimicrobials prevent bacterial cell division by damaging the cell wall or affecting the permeabilities of cells’ membranes; they denature proteins, block enzyme activity, prevent cell survival, etc. Intracellular potassium cations are released by the inhibitions of pathogenic micro-organisms. Their quantitative determination enables monitoring of the bactericidal effect regarding antimicrobials. It can be used as an alternative technique for determining the inhibition of micro-organisms in contact with antimicrobial agents. Chitosan, a biodegradable natural polymer, possesses antimicrobial characteristics that depend on a number of factors such as the protonated amino groups’ quantities, degree of acetylation, molecular weight, solvents, etc. Over recent years chitosan has become extremely attractive for fibre functionalization usage. The aim of this paper was to apply spectrophotometry and potentiometry using potassium ion-selective electrode, respectively, for the quantitative analysis of potassium efflux, resulting from the degradation of micro-organisms’ membranes in contact with chitosan itself, as well as with cellulose fibres functionalised by chitosan.

Film formation of ω-aminoalkylcellulose carbamates – A quartz crystal microbalance (QCM) study

The film formation of novel ω-aminoalkylcellulose carbamates on gold surface was studied by means of quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). The influence of the pH value of the buffer solution, the concentration, the degree of polymerization, and the structure (spacer length) of the polymers on the coating was investigated. The layer formation was explained based on the pKa value and the degree of substitution of the ω-aminoalkylcellulose carbamates determined by potentiometric titration. This work provides novel supporting materials that might be applied in field of immobilization of biomolecules.