Novel hybrid fibrous membranes with potential application on the biomedical field were successfully developed via electrospinning of blend solutions of two biocompatible and biodegradable polymers, poly (3-hydroxybutyrate-co-hydroxyvalerate) [PHBV] and chitosan. The effect of solvent, using different proportions of trifluoracetic acid (TFA) and 1,1,1,3,3,3-hexafluoro-2-isopropanol (HFIP), PHBV/chitosan ratio, and chitosan molecular weight on solution spinnability, fiber morphology and size, and in vitro degradation were investigated. Continuous nanofiber structures were obtained from pristine PHBV to a PHBV/chitosan ratio of 2:3 (w/w), at 10% (w/v) total polymer concentration. In general, main fiber average diameters increased as chitosan content and molecular weight increased and decreased with the decrease of HFIP content in the solvent. In vitro dissolution tests revealed that the hybrid fibers show much higher degradation rates than the neat PHBV.

The purpose of this study was to evaluate hybrid poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/chitosan nanofibrous mats as scaffolds for skin engineering. In vitro studies were carried out to test the potential of the scaffolds for fibroblasts adhesion, viability, and proliferation (L929 cell line). The in vivo performance was also studied in a full-thickness wound healing model. PHBV/chitosan 4:1 w/w exhibited a higher in vitro biocompatibility and a better ability for cell adhesion and growth, compared to PHBV/chitosan 2:3 w/w. The in vivo assay also revealed the better performance of this scaffold, improving the wound healing process in rats.

O objetivo deste trabalho é estudar o efeito da incorporação de resíduos vegetais obtidos a partir da produção da tradicional bebida valenciana, horchata, em filmes PHBV (poli(3-hidroxibutirato-co 3-hidroxivalerato)). Estes biocompósitos (definidos como compostos biocompatíveis e/ou amigos do ambiente) foram analisados de acordo com a sua utilidade como materiais para a embalagem de produtos alimentares em termos de teor de água, solubilidade e espessura, propriedades mecânicas e térmicas e microestrutura, capacidade antioxidante, teor fenólico total e possibilidade de termo selagem. O interesse da incorporação desta matéria-prima na conceção de filmes poliméricos tem em conta e remete para uma perspetiva sustentável, no que diz respeito à biodegradabilidade e à redução do seu custo de produção, além de promover o conceito de economia circular. Os resultados mostraram que a incorporação do resíduo vegetal nos filmes PHBV resultou numa deterioração significativa das propriedades mecânicas e térmicas, bem como num maior teor de água. O declínio das propriedades mecânicas deveu-se principalmente à fraca e/ou débil aderência entre o polímero altamente hidrofóbico e o resíduo hidrofílico. Além disso, as partículas maiores (fibras) atuam como obstáculos e/ou falhas na matriz do polímero. Considerando os resultados obtidos, uma das melhorias essenciais a implementar é estabelecer uma compatibilidade adequada entre o resíduo lignocelulósico e o material polimérico, quer pela utilização de plastificantes ou aditivos, quer pela utilização de técnicas de funcionalização para aumentar a componente hidrofóbica dos componentes do resíduo. A capacidade antioxidante dos filmes, que provou ser mais elevada em relação ao resíduo puro, deve ser considerada por ser um parâmetro interessante no desenvolvimento de materiais de embalagem ativos para o sector alimentar.

ABSTRACT: The encapsulation of progesterone in poly (hydroxybutirate-co-hydroxyvalerate) (PHBV), poly (ε-caprolactone) (PCL), poly (L-lactic acid) (PLLA) nanoparticles and PHBV/PCL and PHBV/PLLA blend nanoparticles was investigated in this research. Nanoparticles were produced by miniemulsion/solvent evaporation technique with lecithin as surfactant and were characterized regarding to z-average diameter (Dz) and polydispersity (PDI), progesterone recovery yield and encapsulation efficiency. Possible interactions between progesterone and the polymer matrices were investigated by Fourier Transform Infrared Spectroscopy (FTIR). High recoveries (up to 102.43±1.80% for the PHBV/PLLA blend) and encapsulation efficiencies (up to 99.53±0.04% for PCL) were achieved and the nanoparticles presented narrow size distribution (0.12±0.03 for PLLA). PCL nanoparticles (217.5±2.12nm) presented significant difference with the Dz from all the other formulations (P<0.05). The most evident interaction between progesterone and the nanoparticles polymeric matrix was found to PHBV/PCL due to the increase in the intensity of the band located in 1631 cm-1.

In recent years, 5-(oxiran-2-ylmethyl)-1,3-benzodioxole or safrole oxide (SO) has been widely studied due to its concentration dependent properties, such as cellular apoptosis inducing activity and cell transdifferentiation. Coprecipitation of SO with a biodegradable and biocompatible polymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), were performed using solution enhanced dispersion by supercritical fluids technique (SEDS). A 2(4-1) factorial design was carried out to investigate the effect of processing parameters (pressure, solution flow, anti-solvent flow and concentrations of PHBV and SO) on the process efficiency and microparticle morphology. Both fibrous and spherical shapes were observed for coprecipitated SO/PHBV, which were dependent on the experimental-processing conditions. Controlled release mechanisms of SO to spherical materials were different from fibrous materials. Thermal analysis showed a decrease in the temperature of maximum weight loss rate (Tmax) of PHBV, attributed to the presence of SO and sample morphology.

Poly(3-hydroxybutirate-co-3-hydroxyvalerate) (PHBV) microparticles containing a water-soluble model drug, metformin hydrochloride (MH), were obtained by a double emulsion/solvent evaporation technique. Several formulations were prepared in order to investigate the influence of each composition on the encapsulation efficiency (EE). The highest value of EE (9.76%) was obtained using simultaneously pH alkalinization and NaCl addition in the external water phase of the formulation. SEM study revealed a spherical morphology and a rough surface. The crystalline diffraction intensities for the MH-loaded microparticles were lower than that verified for the physical mixture. FTIR results suggested that no chemical bond between the polymer and the drug was formed. Also thermal analyses indicated a favorable interaction between MH and PHBV. In vitro drug release demonstrated the influence of the PHBV on the dissolution profile of MH.

Melt blending of 1:1 poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and glycerol-plasticized starch (TPS) was performed in the presence of an organically-modified montmorillonite, incorporated at 2.5, 5, 7.5 and 10 wt% amounts. Scanning electron micrographs (SEM) revealed the role of the organoclay as a compatibilizing agent for the immiscible blend. The blends were also characterized by X-ray diffraction (XRD), tensile tests, humidity absorption and soil burial biodegradation tests. The results indicated improved properties of the hybrid materials in relation to TPS alone, with a faster biodegradation rate than PHBV.

Films of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) - PHBV with polyethylene glycol (PEG) were prepared by casting solvent evaporation. The thermal behavior, morphology, crystallinity and molecular weight of these films were studied by the following techniques: differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD), size exclusion chromatography (SEC). Mixtures of PHBV/PEG showed a high crystallinity degree, measured by XRD, with values ranging between 60 and 90% according to the concentration of PEG. The melting temperature of PHBV decreased with increasing addition of plasticizer (PEG) in the mixture. SEM results showed that the mixtures were uniform, except for the composition 50/50 which proved to be heterogeneous, as evidenced by the presence of two phases. PHBV had molar mass (Mw = 206000 g mol-1), while the introduced PEG molar mass (Mw = 1350 to 1650 g mol-1). The addition of PEG caused the crystallinity of the polymer films to increase owing to the high crystallinity of PEG. The melting point of the PHBV/PEG mixtures also diminished. In addition, SEC analysis of the blends indicated a reduced molar mass for the mixtures in comparison to pure PHBV (100/0).

ABSTRACT In this work, nanobiocomposites of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced with cellulose nanofibrils (CNFs) were produced by electrospinning and solution casting process. CNFs were obtained by sulfuric acid hydrolysis from Imperata brasiliensis fibers. Nanocomposites loaded with 1 (wt. %) of CNFs were prepared using a mixture of solvents chloroform (CHCl3): N, N-dimethylformamide (DMF), in the ratio of 78:22 with 30 h of solubilization. Films by solution casting were obtained in a petri dish, at 50 °C for 1 hour, using drying casting temperature of 153 °C. Mats by electrospinning were obtained with a needle 20x10, drum collector rotation 27 rpm, and working distance of 10 cm. Films and mats were characterized by Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Differential Scanning Calorimetry (DSC). It was possible to conclude that for nanobiocomposites obtained by solution casting, the addition of CNFs did not affect the transparency of the films, but provided a significant increase in the crystallization rate as observed by DSC analysis, while for electrospinning nanobiocomposites a considerable improvement in process increasing electrospinning time and quality of the mats manufactured, were observed.

A crescente utilização de materiais poliméricos bioreabsorvíveis em medicina, tem estimulado pesquisadores na área ortopédica na busca de soluções mais biológicas, substituindo artefatos tais como fios, hastes e placas metálicas por polímeros bioreabsorvíveis no tratamento de fraturas. Para tanto, resolveu-se estudar implantes da blenda de PLLA/PHBV (dois polímeros bioreabsorvíveis) moldados em uma mini-injetora. Esses implantes foram utilizados para recuperação de fraturas de fêmur de coelhos e avaliados em comparação ao fio de Steinmann (aço inox, usado comercialmente). Após eutanásia com 6, 12 e 24 semanas de implantação dos artefatos, os ossos foram estudados com radiografias, exame histológico e ensaio mecânico, enquanto os implantes poliméricos foram submetidos a microscopia eletrônica de varredura (SEM), ensaio mecânico e calorimetria diferencial de varredura modular (MDSC). As radiografias mostraram calos ósseos bem formados, tanto com o uso da haste de polímero como com o controle metálico. O estudo histológico mostrou ausência de reações inflamatórias ou osteólise. O ensaio mecânico mostrou que a consolidação óssea ocorreu nos dois grupos. Tanto no ensaio mecânico como na calorimetria observou-se que a haste polimérica apresentou sinais de degradação progressiva no tempo estudado. Com os dados obtidos neste estudo, podemos afirmar que o implante PLLA/PHBV demonstrou ser efetivo na reparação de fraturas do fêmur de coelhos quando comparado com o controle metálico.