Gabriela Hitruc

Cationic curdlan: Synthesis, characterization and application of quaternary ammonium salts of curdlan.

Water-soluble curdlan derivatives containing quaternary ammonium groups with a degree of substitution up to 0.15 were synthesized using different cationic agents in alkaline medium. The chemical structure of curdlan derivatives was confirmed by FTIR, (13)C and (1)H NMR spectroscopy. The influence of some reaction conditions (temperature, time, and molar ratio) on the degree of substitution and the viscosimetic behaviour were studied. The degree of substitution increased with the amount of the cationization agent per anhydroglucose unit and was higher when the glycidyl reagents were used, compared with the case when the reagents contained chloro-hydroxypropyl groups. The viscosity behaviour of these new derivatives of curdlan in aqueous solutions and the values of intrinsic viscosities calculated using different semi-empirical equations denote a high hydrodynamic dimension of the macromolecular coils. The interaction of these cationic curdlan derivatives with an anionic curdlan (monobasic curdlan phosphate) was studied in situ by turbidimetric measurements and after 24h by optical density and dynamic light scattering. The formation of polyelectrolyte complexes was influenced by the degree of substitution, the nature of the quaternary substituent, and by the ionic strength of the aqueous solution. The morphology of the polyelectrolyte complexes particles in dry state was examined by atomic force microscopy.

Effect of the lignin type on the morphology and thermal properties of the xanthan/lignin hydrogels.

This paper reports the morphological and thermal characterization of xanthan/lignin hydrogels. It has been emphasized the effect of the lignin type on the hydrogel properties. The hydrogels described here were obtained by chemical crosslinking, in the presence of epichlorohydrine as a cross-linker agent. The obtained materials were analyzed by AFM, TG/DTG, DSC, and FT-IR spectroscopy. It has been established that hydrogels have a porous morphology. The lignin type influences the hydrogel morphology which is either fibrilar as in case of hydrogel containing aspen wood lignin (which has the highest content of COOH groups and lowest content of phenolic OH groups) or smooth surface for other hydrogels. The specific intermolecular interactions are stronger in the case of 70 xanthan (X)/30 aspen wood lignin (AWL) hydrogel. The thermal properties of the hydrogels also depend on lignin type, the lowest thermal stability being found for the hydrogel containing lignin with the highest content of functional groups (AWL).

Hybrid Nanostructures Containing Sulfadiazine Modified Chitosan as Antimicrobial Drug Carriers

Chitosan (CH) nanofibrous structures containing sulfadiazine (SDZ) or sulfadiazine modified chitosan (SCH) in the form of functional nanoparticles attached to nanofibers (hybrid nanostructures) were obtained by mono-axial and coaxial electrospinning. The mono-axial design consisted of a SDZ/CH mixture solution fed through a single nozzle while the coaxial design consisted of SCH and CH solutions separately supplied to the inner and outer nozzle (or in reverse order). The CH ability to form nanofibers assured the formation of a nanofiber mesh, while SDZ and SCH, both in form of suspensions in the electrospun solution, assured the formation of active nanoparticles which remained attached to the CH nanofiber mesh after the electrospinning process. The obtained nanostructures were morphologically characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SDZ release profiles and kinetics were analyzed. The SDZ or SCH nanoparticles loosely attached at the surface of the nanofibers, provide a burst release in the first 20 min, which is important to stop the possible initial infection in a wound, while the SDZ and SCH from the nanoparticles which are better confined (or even encapsulated) into the CH nanofibers would be slowly released with the erosion/disruption of the CH nanofiber mesh.

Surface characterization and drug release from porous microparticles based on methacrylic monomers and xanthan.

Porous crosslinked microparticles based on glycidyl methacrylate and xanthan were prepared by suspension polymerization and used for loading theophylline, a bronhodilatator drug, in order to obtain new drug delivery systems. The surface morphologies observed by means of SEM and AFM analysis demonstrated that microparticles show a spherical shape and are characterized by a porous structure. The presence of xanthan in the structure of microparticles leads to a decrease of surface roughness and pore diameters as well as to an increase of hydrophilicity degree compared to the micropaticles based only on glycidyl methacrylate. To analyze the in vitro release data various mathematical models were used, such as, first order, Higuchi model, Korsmeyer-Peppas model and Baker-Lonsdale model. Based on the highest values of the correlation coefficient, the analysis of the kinetic data indicate that drug release from G1 and X1 porous microparticles fits similarly well to the first order and Higuchi models and diffusion was the dominant mechanism of drug release.

Preparation and characterization of block copolymers containing cinnamate groups with end-capped ZnO

ZnO-poly(2-cinnamoyloxyethyl methacrylate) and ZnO-poly(2-cinnamoyloxyethyl methacrylate)-b-poly[(poly(ethylene glycol) methyl ether methacrylate] have been prepared by atom transfer polymerization initiated through a 2-bromoisobutyryl or bromoethyl group linked onto the ZnO nanoparticle surface (ZnO-BIBB, ZnO-BEI). The structure and morphology of the hybrids were characterized using Fourier transform infrared, proton nuclear magnetic resonance, fluorescence and UV spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron (TEM) and atomic force microscopy. The existence of nanoparticles with diameters varying between 40 and 100 nm was evident in the TEM images of the pure ZnO, ZnO-PCEMA-Br-2 and the diblock copolymer. Under an excitation of 340 nm, these materials exhibit a broad emission band at around 390 nm, which was associated with the presence of ZnO in the organic matrix.Graphical abstract

Plasma-activated fibrinogen coatings onto poly(vinylidene fluoride) surface for improving biocompatibility with tissues

CO2, N2, and N2/H2 radiofrequency plasma exposure was used for functionalization of poly(vinylidene fluoride) surface aiming the fibrinogen immobilization. Fibrinogen was immobilized onto poly(vinylidene fluoride) surface using both simple plasma activation and covalent coupling. The modified surfaces have been characterized by X-ray photoelectron spectroscopy, attenuated total reflectance–Fourier transform infrared spectroscopy, near infrared–chemical imaging, atomic force microscopy, and wettability measurements, and the obtained materials were tested as supports for fibroblast cell cultures. The plasma type and the immobilization procedure have influenced the fibrinogen attachment onto the poly(vinylidene fluoride) surface, which was achieved mainly through amide bonds when using coupling agents. Covalent immobilization of fibrinogen onto poly(vinylidene fluoride) surface leads to a more stable protein-modified polymer surface. Non-cytotoxic plasma-based coating technology has the ability to covalently immobilize bioactive molecules for surface modification of some biomaterials that mainly could be achieved by the immobilization of proteins such as fibrinogen that triggers desirable cellular responses. The fibrinogen-modified poly(vinylidene fluoride) materials showed increased cell viability of fibroblasts. Cell viability was enhanced by plasma-activated fibrinogen coatings onto poly(vinylidene fluoride) surface, this being more significant if coating was linked further by a coupling reaction. Hence, they could be good candidates for biomedical applications.

Antioxidant/Antibacterial Electrospun Nanocoatings Applied onto PLA Films

Polylactic acid (PLA) films were coated by coaxial electrospinning with essential and vegetable oils (clove and argan oils) and encapsulated into chitosan, in order to combine the biodegradability and mechanical properties of PLA substrates with the antimicrobial and antioxidant properties of the chitosan–oil nanocoatings. It has been established that the morphology of the electrospun nanocoatings mainly depend on the average molecular weight (MW) of chitosan. Oil beads, encapsulated into the main chitosan nanofibers, were obtained using high-MW chitosan (Chit-H). Oil encapsulated in chitosan naoparticles resulted when low-MW chitosan (Chit-L) was used. The coating layer, with a thickness of 100 ± 20 nm, had greater roughness for the samples containing Chit-H compared with the samples containing Chit-L. The coated PLA films had higher antibacterial activity when the nanocoating contained clove oil rather than when argan oil was used, for both types of chitosan. Nanocoatings containing Chit-H had higher antibacterial activity compared with those containing Chit-L, for both types of oil tested, due to the larger surface area of the rougher nanoscaled morphology of the coating layer that contained Chit-L. The chitosan–clove oil combination had higher antioxidant activity compared to the simple chitosan nanocoating, which confirmed their synergistic activities. The low activity of systems containing argan oil was explained by big differences between their chemical composition and viscosity.