Patrícia Santiago de Oliveira Patrício

Hybrid layer-by-layer assembly based on animal and vegetable structural materials: multilayered films of collagen and cellulose nanowhiskers

Layer-by-layer (LBL) assembly was used to combine crystalline rod-like nanoparticles obtained from a vegetable source, cellulose nanowhiskers (CNWs), with collagen, the main component of skin and connective tissue found exclusively in animals. The film growth of the multilayered collagen/CNW was monitored by UV-Vis spectroscopy and ellipsometry measurements, whereas the film morphology and surface roughness were characterized by SEM and AFM. UV-Vis spectra showed the deposition of the same amount of collagen, 5 mg m−2, in each dipping cycle. Ellipsometry data showed an increment in thickness with the number of layers, and the average thickness of each bilayer was found to be 8.6 nm. The multilayered bio-based nanocomposites were formed by single layers of densely packed CNWs adsorbed on top of each thin collagen layer where the hydrogen bonding between collagen amide groups and OH groups of the CNWs plays a mandatory role in the build-up of the thin films. The approach used in this work represents a potential strategy to mimic the characteristics of natural extracellular matrix (ECM) which can be used for applications in the biomedical field.

Pharmaceutical acrylic beads obtained by suspension polymerization containing cellulose nanowhiskers as excipient for drug delivery

Direct compression is one of the most popular techniques to prepare tablets but only a few commercial excipients are well adapted for this process into controlled release formulations. In the last years, the introduction of new materials for drug delivery matrix tablets has become more important. This paper evaluated the physicochemical and flow properties of new polymeric excipient of ethyl acrylate, methyl methacrylate and butyl metacrylate, synthesized by suspension polymerization using cellulose nanowhiskers as co-stabilizer, to be used as direct compression for modified release tablets. Infrared spectroscopy (FTIR) confirmed the success of the copolymerization reaction. Scanning electron microscopy (SEM) showed that excipient was obtained how spherical beads. Thermal properties of the beads were characterized by thermogravimetric (TG) analysis. Particle size analysis of the beads with cellulose nanowhiskers (CNWB) indicated that the presence of the nanowhiskers led to a reduction of particle size and to a narrower size distribution. In vitro test showed that the nanowhiskers and beads produced are nontoxic. Parameters such as Hausner ratio, Carrs index and cotangent of angle α were employed to characterize the flow properties of CNWB beads. Furthermore, the beads are used to produce tablets by direct compression contained propranolol hydrochloride as model drug. Dissolution tests performed suggested that beads could be used as excipient in matrix tablets with a potential use in drug controlled release.

Efficacy of methotrexate-loaded poly(ε-caprolactone) implants in Ehrlich solid tumor-bearing mice.

Abstract Context: Methotrexate (MTX) is used in the treatment of malignancies; however, its clinical application is limited by its toxic dose-related side effects. An alternative to overcome the toxicity of the MTX in healthy tissues is the design of an implantable device capable of controlling the delivery of this drug for an extended period within the tumor site. Objective: To develop methotrexate-loaded poly(ε-caprolactone) implants (MTX PCL implants) and to demonstrate their efficacy as local drug delivery systems capable of inhibiting Ehrlich solid tumor bearing mice. Materials and methods: MTX PCL implants were produced by the melt-molding technique and were characterized by FTIR, WAXS, DSC and SEM. The in vitro and in vivo release of MTX from the PCL implants was also evaluated. The efficacy of implants in inhibiting tumor cells in culture and the solid tumor in a murine model was revealed. Results and discussion: The chemical and morphological integrity of the drug was preserved into the polymeric matrix. The in vitro and in vivo release processes of the MTX from the PCL implants were modulated by diffusion. MTX diffused from the implants revealed an antiproliferative effect on tumor cells. Finally, MTX controlled and sustained released from the polymeric implants efficiently reduced 42.7% of the solid tumor in mice paw. Conclusion: These implantable devices represented a contribution to improve the efficacy and safety of chemotherapy treatments, promoting long-term local drug accumulation in the targeted site.

Effect of tungsten doping on catalytic properties of niobium oxide

A novel material based on niobia (Nb2O5) was synthesized to oxidize an organic compound in aqueous medium in the presence of H2O2 after chemical modifications. Niobia was modified by doping with tungsten and also treating with H2O2 in order to maximize the oxidative properties of this oxide. The analysis of the products from methylene blue dye oxidation with electrospray ionization mass spectrometry (ESI-MS) showed that the dye was successively oxidized to different intermediate compounds. The successive hydroxylation during this oxidation strongly suggests that highly reactive hydroxyl radicals are generated involving H2O2 on the W-doped niobia grain surface. These results strongly suggest that the H2O2 can regenerate in situ the peroxo group remaining active the system.

Comparison of the effect of sol-gel and coprecipitation routes on the properties and behavior of nanocomposite chitosan-bioactive glass membranes for bone tissue engineering

Recent studies in tissue engineering have highlighted the importance of the development of composite materials based on biodegradable polymers containing bioactive glasses, in particular, composites for high load support and excellent cell viability for potential application in bone regeneration. In this work, hybrid composite films were obtained by combining chitosan with bioactive glass in solution form and in nanoparticle dispersion form obtained by the two different synthesis routes: the sol-gel method and coprecipitation. The bioactive glass served both as a mechanical reinforcing agent and as a triggering agent with high bioactivity. The results of in vitro assays with simulated body fluid demonstrated the formation of a significant layer of fibrils on the surface of the film, with a typical morphology of carbonated hydroxyapatite, reflecting induction of a favorable bioactivity. Maximum tensile stress increased from 42 to 80 MPa to the sample with 5% wt bioactive glass. In addition, samples containing 5% and 10% wt bioactive glass showed a significant increase in cell viability, 18 and 30% increase compared to the control group. The samples showed significant response, indicating that they could be a potential material for use in bone regeneration through tissue engineering.

Development and Evaluation of Sustained-Release Etoposide-Loaded Poly(ε-Caprolactone) Implants

Poly(ε-caprolactone) implants containing etoposide, an important chemotherapeutic agent and topoisomerase II inhibitor, were fabricated by a melt method and characterized in terms of content uniformity, morphology, drug physical state, and sterility. In vitro and in vivo drug release from the implants was also evaluated. The cytotoxic activity of implants against HeLa cells was studied. The short-term tolerance of the implants was investigated after subcutaneous implantation in mice. The original chemical structure of etoposide was preserved after incorporation into the polymeric matrix, in which the drug was dispersed uniformly. Etoposide was present in crystalline form in the polymeric implant. In vitro release study showed prolonged and controlled release of etoposide, which showed cytotoxicity activity against HeLa cells. After implantation, good correlation between in vitro and in vivo drug release was found. The implants demonstrated good short-term tolerance in mice. These results tend to show that etoposide-loaded implants could be potentially applied as a local etoposide delivery system.

Recycled collagen films as biomaterials for controlled drug delivery

The present study concerns an innovative technology for the extraction of chromium, which is present in leather industry wastes, to facilitate the application of chromium-free protein (collagen) as a slow-release drug carrier in skin treatment when there are burns, ulcers and infected wounds. The study focuses on the excavation of industrial landfills, which are currently saturated, to recycle residual wet blue leather to obtain purified collagen films. These films, as biocompatible materials, offer great potential as drug carriers. We test here the materials ability to retain/release silver sulfadiazine and its potential to impede the proliferation of various bacteria. The very promising results demonstrate that the material possesses a high capacity for delivery of the drug and great efficiency in inhibiting bacteria proliferation. The obtained results indicate that the treatment proposed for chromium removal is capable of generating a material rich in amino acids that can be transformed into films with no cellular incompatibility, therefore creating a new field of study from a material that presents a serious environmental liability.

Nanostructured oxyhydroxide niobium (NbO2OH) as UV radiation protector for polypropylene

In this study a novel approach for improving the photo-stabilization of polymers by incorporation of nanoparticles of a new niobium compound is reported. For the first time, this approach uses the electronic properties of niobium oxyhydroxide to absorb UV light efficiently to avoid the decomposition of the polymers. The innovative results of this work consist of preparing nanoparticles of niobium oxyhydroxide and its modification by treatment with hydrogen peroxide to alter their ability to absorb radiation and act as a photo-stabilizer for preventing polypropylene degradation. Synchrotron radiation was employed: (i) to explore the niobium nanoparticle form and (ii) to investigate the macromolecular structure of neat PP and PP/Nb compounds before and after degradation. The results from this research study using FTIR-ATR, DSC and microscopies, as TEM, SEM and OM, indicate that the incorporation of niobium oxyhydroxide nanoparticles into the PP matrix provides stability against the action of ultraviolet radiation.

3D nanocomposite chitosan/bioactive glass scaffolds obtained using two different routes: an evaluation of the porous structure and mechanical properties

Porous synthetic substrates are developed through tissue engineering technologies to grow new tissue, restoring the function of tissue or an organ. For bone regeneration, these scaffolds must support the dynamic load exerted on this tissue, achieved primarily by increasing their compression strength, as established in the literature. The aim of this paper was to incorporate an inorganic composite bioactive glass (60%SiO2 - 36%CaO - 4%P2O5) as a reinforcing agent in mechanical 3D scaffolds that must remain porous. Two strategies were adopted: a co-precipitation method to obtain a nanoparticulate dispersion of bioactive glass (BGNP) and a sol-gel method to combine a bioactive glass solution (BG) with a previously prepared chitosan polymer solution. Moreover, a lyophilization process was also used, generating highly porous scaffolds. Various aspects of the scaffold were evaluated, including the morphology, orientation and size of the pores, and mechanical strength, as obtained using the two synthetic methods. The data for compressive strength revealed increased strength after the incorporation of bioactive glass, which was more pronounced when utilizing the nanoscale bioactive glass.

Correlation between morphological properties and ionic conductivity in an electrolyte based on poly(vinylidene fluoride) and poly (2-hydroxyethyl methacrylate)

. MDSC results showed that the transition temperatures of the polymers shifted to higher temperatures for systems containing high concentrations of each polymer. SEM images indicated that there was some miscibility between the polymers especially for the 25 and 75 wt. % compositions. In terms of the electrical performance, the ionic conductivity level of the electrolyte could be controlled by changing the composition of the system.