Sustainable hydroxypropyl methylcellulose/xyloglucan/gentamicin films with antimicrobial properties.

Hydroxypropyl methylcellulose (HPMC) and xyloglucan (XG) crosslinked with citric acid over a range of HPMC/XG weight ratios formed sustainable blend films characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, tensile tests, circular dichroism and determination of inhibitory activity against Staphylococcus aureus and Escherichia coli. Both in solution and in the crosslinked films, HPMC chains lost the original ordered conformation upon interacting with XG, giving rise to an entropic gain. The highest values of tensile strength (25MPa) and Young's modulus (689MPa) occurred for the 50:50 HPMC/XG blend films. In vitro loading of gentamicin sulfate (GS) in the films amounted to 0.18±0.05 -0.37±0.05g of GS per g polymer. At pH 7.4 and 37°C, the GS release kinetics from the films fitted with the Korsmeyer-Peppas model revealed a non-Fickian release mechanism with diffusional coefficient n∼0.7. The cross-linked films of HPMC, XG and their blends loaded with GS showed outstanding antibacterial activity against Staphylococcus aureus and Escherichia coli, disclosing their potential for novel biomedical applications.

Hydrophilicity improvement of mercerized bacterial cellulose films by polyethylene glycol graft.

In this work, polyethylene glycol (PEG), of tree distinct molar masses (200, 300 and 400 g mol(-1)), was grafted onto mercerized bacterial nanocellulose (BNCm) and applied to produce nanofilms (BNCm-PEG). The products BNCm-PEG were characterized by NMR and thermal analysis. Solid-state NMR and X-ray diffraction analyses exhibited no significant differences in index of BNCm-PEG derivatives compared to BNCm, indicating that grafting reaction did not modify the BNCm crystalline structure. The apparent contact angle of the films showed that BNCm-PEG films exhibited a pronounced increase in the polar components (BNCm: 8.1 mN m(-1) vs BNCm-PEG400: 29.4 mN m(-1)), and a decrease in dispersive components (BNCm: 41.7 mN m(-1) vs BNCm-PEG400: 35.2 mN m(-1)) of the surface free energy. The BNCm-PEG films were more hydrophilic than BNCm and retained the biocompatibility with L929 fibroblast cells culture.

Preparation of cellulose II and IIII films by allomorphic conversion of bacterial cellulose I pellicles.

The structural changes resulting from the conversion of native cellulose I (Cel I) into allomorphs II (Cel II) and IIII (Cel IIII) have usually been studied using powder samples from plant or algal cellulose. In this work, the conversion of Cel I into Cel II and Cel IIII was performed on bacterial cellulose films without any mechanical disruption. The surface texture of the films was observed by atomic force microscopy (AFM) and the morphology of the constituting cellulose ribbons, by transmission electron microscopy (TEM). The structural changes were characterized using solid-state NMR spectroscopy as well as X-ray and electron diffraction. The allomorphic change into Cel II and Cel IIII resulted in films with different crystallinity, roughness and hydrophobic/hydrophilicity surface and the films remained intact during all process of allomorphic conversion.

Electrospinning of commercial guar-gum: Effects of purification and filtration.

Guar gums of two different commercial sources were successfully electrospun on both mica and copper tape at several concentrations starting from 1% (w/w). The electrospun fibers formed with the raw materials were not uniform and presented aggregates and beads within the fibers. Two different purification procedures and a filtration sequence with different pore size membranes were applied to enhance galactomannan solution homogeneity and solubility. The consequence was improved fiber morphology. We observed that the precipitation step, within the purification procedure, produced changes in the molar mass distribution and yielded different fiber diameter. Furthermore, spherical aggregates between fibers and within them disappeared after the sequential filtration. The resulting electrospun fiber diameter decreased with membrane pore diameter reduction. We conclude that the filtration process is responsible for molecular disentanglement, as well as disaggregation, which leads to improved electrospun galactomannan fiber morphology.

AFM characterization of spin coated carboxylated polystyrene nanospheres/xyloglucan layers on mica and silicon.

Self-assembled nano-arrays have a potential application as solid-phase diagnostics in many biomedical devices. The easiness of its production is directly connected to manufacture cost reduction. In this work, we present self-assembled structures starting from spin coated thin films of carboxylated polystyrene (PSC) and xyloglucan (XG) mixtures on both mica and silicon substrates. AFM images showed PSC nanospheres on top of a homogeneous layer of XG, for both substrates. The average nanosphere diameter fluctuated for a constant speed and it was likely to be independent of the component proportions on the mixture within a range of 30-50% (v/v) PSC. It was also observed that the largest diameters were found at the center of the sample and the smallest at the border. The detected nanospheres were also more numerous at the border. This behavior presents a similarity to spin coated colloidal dispersions. We observed that the average nanosphere diameter on mica substrates was bigger than the nanosphere diameters obtained on top of silicon substrates, under the same conditions. This result seems to be possibly connected to different mixture-surface interactions.

Dewetting pattern and stability of thin xyloglucan films adsorbed on silicon and mica.

Thin polysaccharide films prepared with xyloglucan (XG), a neutral polysaccharide extracted from the seeds of Guibourtia hymenifolia were prepared by spin-coating and drop deposition under pH3, pH5 and pH12, on silicon and mica substrates. Atomic force microscopy (AFM) images show flat nanoporous matrices with additional grain-like structures on both mica and silicon for pH 3 and pH 5. However, X-ray photoelectron spectroscopy (XPS) and Auger spectra of these adsorbed biopolymers prepared under alkaline condition (pH 12) reveal that Na(+) ions from the solution interact with the mica substrate surface and with XG forming chemical bonds. Both XPS and Auger results suggest XG depolymerisation during adsorption, caused by an alkaline ss-base catalyzed degradation mechanism, which is consistent with the more basic character of the mica surface under these conditions. Thus, the polysaccharide diffusion is inhibited during dewetting due to the surface bonding. On the other hand, the interaction of Na(+) in solution with the silicon surface is weaker, favoring its interaction with the polysaccharide, conserving the overall polymer structure of XG and allowing the biopolymer to slip and diffuse during dewetting, forming the final branched fractal structure.

Characterization and potential uses of Copaifera langsdorfii seeds and seed oil.

Copaifera langsdorfii (Desf.) Kuntze (copaiba) seeds are abundantly produced and have not yet been characterized. The seed oil presents a characteristic odor of coumarin (250.1+/-6.57 mg/g determined through LC). The fatty acid composition of the oil was determined through CG/FID, being 45.3% linoleic acid, 32.3% monounsaturated, and 22.4% saturated fat. For the lipid-free seeds, the total carbohydrate, protein and moisture were 75.4%, 6.8% and 14.8%, respectively. The C. langsdorfii xyloglucan had an intrinsic viscosity of 804 mL/g, and the average molar mass (Mw) was 7.82 x 10(5)g/mol and Rg of 65 nm. The degree of polydispersion was 1.7, indicating the polydisperse family of polysaccharides. Its homogeneity, low degree of polymer contaminants and high intrinsic viscosity and molecular mass, represent good potential as a thickening agent. The presence of coumarin and xyloglucan as major components of C. langsdorfii seeds denotes its potential for use in the cosmetic or pharmaceutical industries.