Rosane Michele Duarte Soares

Gelatin and galactomannan-based scaffolds: Characterization and potential for tissue engineering applications.

In this work, we produced gelatin films containing different concentrations of galactomannan by casting solutions. The films were crosslinked by immersion in 30mM solution of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC). The crosslinking of gelatin-containing films was confirmed by the reduction of free amine band intensity (3400-3200cm(-1)) in the GEL IR, as well as by the evaluation of its behavior when immersed in phosphate-buffer solution. The crosslinking of galactomannan film was confirmed by the formation of new ether bonds, as observed by increasing intensity of the band at 1148cm(-1), and the reduction of OH band intensity (3600-3200cm(-1)). The presence of galactomannan and the crosslinking mediated by EDC were responsible to improve elasticity in the gelatin-based films. The samples did not show cytotoxicity during 24h or 48h. In addition, rat mesenchymal stem cells adhered to the films regardless of galactomannan concentration. The results indicated that the gelatin/galactomannan films are potential biomaterials for use as scaffolds for tissue engineering.

Poly (lactic acid)/chitosan fiber mats: Investigation of effects of the support on lipase immobilization

The greatest challenge for biotechnological processes is to have immobilized enzymes acting as good green catalysts with high reusability rates. In this work, we have produced electrospun fibers from poly (lactic acid)/chitosan blends. Further, we evaluated the influence of these materials as support for lipase immobilization. The PLA/chitosan fiber mats were composed by non-woven nanofibers, with diameters ranging from 200 nm to 1.3 μm. The solvent (TFA) as well as the chitosan addition influenced morphology, hydrophobicity and mechanical properties of PLA nanofibers. It was observed that even for lower concentration of lipase (5 U) higher enzyme activity retention was detected in the PLA/chitosan blends. In addition, a remarkable improvement of lipase activity on pure PLA fiber mat was verified, indicating that most of the enzymes were probably in their active form.

A novel globular protein electrospun fiber mat with the addition of polysilsesquioxane.

The aim of this work has been to elaborate well defined gliadin nanofibers with incorporation of inorganic molecules, such as polyhedral oligomeric silsesquioxane (POSS). Nanofibers were obtained by electrospinning processing, controlling the relevant parameters such as tip-to-collector distance, voltage and feed rate. The fiber mats were characterized by SEM, confocal images, DSC, viscosity, FTIR and conductivimetry analysis. FTIR spectra showed characteristic absorption bands related to the presence of POSS-NH(2) within the matrices. SEM micrographs showed that gliadin fibers decreased their dimensions as the amount of POSS-NH(2) increased in the spinning solution. The electrical conductivity of gliadin solutions diminished as the concentration of POSS-NH(2) was increased. Besides, confocal micrographs revealed that POSS-NH(2) might be dispersed as nanocrystals into gliadin and gluten fibers. The dimension of gluten nanofibers was also affected by the POSS-NH(2) concentration, but conversely, this dependence was not proportional to the POSS-NH(2) amount. Somehow, the interaction between gliadin and POSS-NH(2) in aqueous TFE affected the solution viscosity and, as a consequence, higher jet instabilities and thinner fiber dimensions were obtained.

Structural analysis of chitosan hydrogels containing polymeric nanocapsules.

The incorporation of different concentrations of polymeric nanocapsule suspensions into chitosan hydrogels is proposed, in order to study the structure of a formulation with the properties of great tissue adhesion and controlled release of the nanoencapsulated drugs, represented here by capsaicinoids. The gels presented acceptable acid pH values and the nanoparticles were visually observed in the system. A transition from the micrometer to the nanometer scales suggested that the nanocapsules are initially agglomerated in the hydrogel. A sedimentation tendency of the nanocapsules in the system was observed and only physical interaction between the chitosan chains and polymeric nanocapsules was verified. The hydrogels, despite the presence of nanocapsules, presented shear-thinning properties and an elastic behavior under low and high frequencies, showing a very structured gel network. The observed variation in the elasticity of the hydrogels may arise from a decrease in the number of interactions and degree of entanglement between the chitosan chains, caused by the presence of nanoparticles.

Urinary iodine in 24 h is associated with natriuresis and is better reflected by an afternoon sample.

Aims: We aimed to assess the extent of variability in urinary iodine (UI) within a day, to determine the period of the day when UI was better associated with the UI in 24 h, and to study the relationship between UI and urinary sodium. Methods: This cross-sectional study included 60 volunteers. Four urine samples were collected from each participant (A: from breakfast to lunch; B: from lunch to dinner; C: from dinner to bedtime, and D: from bedtime to breakfast) and were compared with the 24-hour sample (calculated from samples A–D ). UI, creatinine and Na+ levels were measured in the partial samples and in the 24-hour sample. Results: The content of iodine and sodium in urine varied during the day (p < 0.001). The UI concentration from lunch to dinner was closest to the 24-hour UI concentration using the method of Bland and Altman. There were correlations between the UI content in the different periods of the day and in 24 h: A (r = 0.54; p < 0.000), B (r = 0.78; p < 0.000), C (r = 0.37; p = 0.004) and D (r = 0.77; p < 0.000). UI and urinary sodium content were strongly correlated in all periods of the day (samples A and B: r = 0.69, p < 0.000; sample C: r = 0.85, p < 0.000, and sample D: r = 0.78, p < 0.000). Conclusions: There was a within-day variation in UI content, which was strongly associated with urinary sodium content. Iodine concentration in the afternoon urine sample better reflected the 24-hour UI concentration. Therefore, urine collected in the afternoon is probably the best to evaluate iodine sufficiency in subjects with similar dietary habits.

Influence of glycerol on morphology and properties of polylactide/montmorillonite nanocomposites

The widespread use of polymers from renewable sources is currently unachievable, not only by economic constraints but by the limiting properties of this type of material. Several strategies have been developed to overcome this problem; one of the most extensively explored is the use of nanofillers to improve the biopolymer’s properties such as stiffness, impact strength and gas barrier, amongst others. However, several gaps in understanding the morphology formation of these systems still exist. This study evaluates the use of glycerol as an auxiliary additive during production of polylactide/montmorillonite nanocomposites. In this study, the presence of glycerol seems to influence the nanocomposites’ morphology, influencing the clay exfoliation in some cases, and the mechanical properties. On the other hand, the presence of glycerol seems to induce a greater molecular weight reduction during twin screw extrusion.

Synthesis and characterization of acetylated amylose and development of inclusion complexes with rifampicin

Amylose (AM) tends to form single helical inclusion complexes with suitable agents. These complexes are considered promising biomaterial carrier since the guest molecules can be released later, leading to many applications, especially in the pharmaceutical industry. Rifampicin (RIF) has long been recognized as an active drug against Mycobacterium tuberculosis, however, the administration of RIF in high dosages can originate unwanted side-effects. Due to the fact that the use of native amylose (AM) in the formation of complexes is limited by their low water solubility, it was acetylated with a medium degree of substitution (DS), allowing solubilizing (0.5gL-1) acetylated amylose (AMA) in water at neutral pH, in opposition to that observed with native amylose (trace solubility). The resulting acetylated amylose was characterized by means of Fourier Transform Infrared (FT-IR) spectroscopy and Scanning Electron Microscopy (SEM). FT-IR results indicated that the acetylation of anhydroglucose units of amylose corresponds to a low DS, whereas SEM results suggested that the smooth surfaces of amylose granules were changed into rougher surfaces after acetylation. Ultraviolet absorption spectroscopy (UV-vis) analysis confirmed the formation and allowed the quantification of both native (AM-RIF) and acetylated (AMA-RIF) amylose inclusion complexes. Their characterization in solution was performed by dynamic light scattering (DLS) and zeta potential (ZP) measurements. The average size of inclusion complexes as determined by DLS, ranged between 70 and 100nm. Besides, ZP analysis showed that both complexes are more stable in the presence of RIF. This study may lead to the development of an effective method for the preparation of amylose inclusion complexes, which is beneficial to their further application in drug delivery systems.

Derivation and culture of putative parthenogenetic embryonic stem cells in new gelatin substrates modified with galactomannan

Human embryonic stem cells (ESC) lines to be used for cell therapies must be created and maintained under strict conditions, excluding the use of undefined supplements. Two key steps in the creation of a new embryonic stem cell line are adherence to the substrate and derivation towards the formation of a primary colony. The bovine parthenote embryo model was used to test different matrices of gelatin nanofibers and gelatin/galactomannan films to be used for ESC derivation and culturing. Gelatin/galactomannan films were made in two concentrations of galactomannan, 0.1 and 0.3%, in an aqueous solution of gelatin and tested for gel cytotoxicity using cumulus cells (CCs). CCs showed normal cell morphology, with no sign of lysis or degeneration in any of the matrices tested. Inner cell masses of parthenote blastocysts (n=116) were placed onto the gel matrices for culture. There were three or four repeats for each matrix. Our results showed a good rate of inner cell mass (ICM) adherence on the gelatin/galactomannan films (41%–44%) and one derivative of the gel nanofiber (17% adherence to the substrate). These results encouraged us to try new gelatin formulations to increase the rates of derivation and cell proliferation under defined culture conditions to comply with good manufacturing practice directives for the potential therapeutic use of ESCs.

CuO Nanofibers Immobilized on Paraffin-Impregnated Graphite Electrode and its Application in the Amperometric Detection of Glucose

1-D nanostructures are promising materials for development of electrochemical devices offering benefits such as fast electron transfer rates and large surface areas. Copper oxide nanofibers (CuO-NFs) synthesized by electrospinning technique and subsequent thermal treatment, were used to modify paraffin-impregnated graphite electrode (PIGE) for a sensitive non-enzymatic glucose detection. The structure and morphology of CuO-NFs were characterized by scanning electron microscopy and transmission electron microscopy. The electrocatalytic activity towards glucose oxidation was evaluated by cyclic voltammetry and chronoamperometry. The results reveal a wide linear response to glucose ranging from 1.0 × 10-6 to 1.93 × 10-3mol L-1 (R2 = 0.9927). The limit of detection was 0.39 × 10-6 mol L-1 (LOD = 3σ/s). The high aspect ratio of the nanofibers arranged in a three-dimensional network structure significantly enhances the electron transfer process. The electrode preparation is simple and rapid execution, and more importantly the graphite rod is relative low-cost and easy to achieve surface renewal for reusability.

Electrospinning and electrospray of bio-based and natural polymers for biomaterials development

Over nearly 70 years, polymers have revolutionized the global economy, manufacturing and, mainly, the fields which require biocompatible materials, as food technology and packaging, controlled drug delivery, tissue engineering, regenerative medicine, wound dressing, anti-allergy textiles, and personal care. While new high-performance polymers were produced from fossil-based sources to meet the functional performance demands of new applications, Earth has been polluted by the operation of factories that released CO2 to the atmosphere during the production of synthetic polymers. At the same time, biocompatible and biodegradable alternatives were being required to meet specific needs of a range of applications. In this paper, we reviewed the use of electrospun/electrospray bio-based and natural polymers in the last ten years in food technology and smart packaging, food additives, antimicrobial packaging, enzyme immobilization, tissue engineering, drug delivery, wound dressing, anti-allergy fibers from milk, and faux meat. Also, we reviewed the use of ionic liquids and click chemistry techniques as alternatives for modification and functionalization of electrospun/electrospray bio-based and natural polymers.