RESUMEN

In this work, scaffolds based on poly(hydroxybutyrate) (PHB) and micronized bacterial cellulose (BC) were produced through 3D printing. Filaments for the printing were obtained by varying the percentage of micronized BC (0.25, 0.50, 1.00, and 2.00%) inserted in relation to the PHB matrix. Despite the varying concentrations of BC, the biocomposite filaments predominantly contained PHB functional groups, as Fourier transform infrared spectroscopy (FTIR) demonstrated. Thermogravimetric analyses (i.e., TG and DTG) of the filaments showed that the peak temperature (Tpeak) of PHB degradation decreased as the concentration of BC increased, with the lowest being 248 °C, referring to the biocomposite filament PHB/2.0% BC, which has the highest concentration of BC. Although there was a variation in the thermal behavior of the filaments, it was not significant enough to make printing impossible, considering that the PHB melting temperature was 170 °C. Biological assays indicated the non-cytotoxicity of scaffolds and the provision of cell anchorage sites. The results obtained in this research open up new paths for the application of this innovation in tissue engineering.

RESUMEN

Poly(3-hydroxybutyrate), PHB, is a hydrophobic biopolymer with good mechanical and barrier properties. However, neat PHB is a semicrystalline polymer with a relative high degree of crystallinity and poor film properties. In this work, this biopolymer was plasticized with glycerol tributyrate and functionalized with copper (II) sulfate, allowing us to obtain biodegradable antimicrobial flexible films. Films with the minimum inhibitory concentration (MIC) of copper (II) sulfate presented a higher roughness than neat PHB films. The presence of plasticizer significantly improved the copper sulfate diffusion process, which was evidenced by a greater inhibition halo for plasticized materials compared to unplasticized ones, at the same salt concentration. Plasticized PHB with 2.5% copper (II) sulfate inhibited both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomona aeruginosa) bacteria, as determined by the bacterial inhibition halo. In addition, neat PHB films and PHB containing copper (II) sulfate did not show in vitro cytotoxicity in the L-929 cell line. Thus, plasticized PHB functionalized with copper (II) sulfate can be used as biodegradable antimicrobial flexible films for different applications.

RESUMEN

This work aimed to produce porous poly-hydroxybutyrate (PHB) pellets in order to evaluate the pellets as a support for immobilization of the metagenomic lipase, LipG9. Four types of pelletized PHB particles with different morphological characteristics were obtained using the double emulsion and solvent evaporation technique (DESE). The micropores of these PHB pellets had similar average diameters (about 3 nm), but the pellets had different specific surface areas: 11.7 m2 g-1 for the PHB powder, 8.4 m2  g-1 for the control pellets (Ø < 0.5 mm, produced without the pore forming agent), 10.0 m2  g-1 for the small pellets (Ø < 0.5 mm), 9.5 m2  g-1 for the medium pellets (0.5 < Ø < 0.8 mm) and 8.4 m2  g-1 for the large pellets (Ø > 1.4 mm). Purified LipG9 was immobilized by adsorption on these pellets, and the results were compared with those obtained with PHB powder. The highest immobilization yield (83%) was obtained for the medium PHB pellets, followed by large (76%) and small (55%) PHB pellets. The activity of LipG9 immobilized on the pellets, for the synthesis of ethyl oleate in n-hexane, was highest for the medium pellets (22 U g-1 ). The immobilization yield was high for PHB powder (99%) but the esterification activity was slightly lower (20 U g-1 ). These results show that pelletized PHB beads can be used for the immobilization of lipases, with the advantage that pelletized PHB will perform better than PHB powder in large-scale enzyme bioreactors.

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RESUMEN

Fully bio-based poly(lactic acid) (PLA) and poly(3-hydroxybutyrate) (PHB) blends plasticized with tributyrin (TB), and their nanocomposite based on chitin nanoparticles (ChNPs) was developed using melt mixing followed by a compression molding process. The combination of PHB and ChNPs had an impact on the crystallinity of the plasticized PLA matrix, thus improving its oxygen and carbon dioxide barrier properties as well as displaying a UV light-blocking effect. The addition of 2 wt% of ChNP induced an improvement on the initial thermal degradation temperature and the overall migration behavior of blends, which had been compromised by the presence of TB. All processed materials were fully disintegrated under composting conditions, suggesting their potential application as fully biodegradable packaging materials.

RESUMEN

The overall migration behavior and the disintegration under composting conditions of films based on plasticized poly(lactic acid)/poly(3-hydroxybutyrate) (PLA-PHB) blends were studied, with the main aim of determining the feasibility of their application as biodegradable food packaging materials. The role of composition in the disintegration process was evaluated by monitoring the changes in physical and thermal properties that originated during the degradation process. PLA and PHB were blended in two weight ratios with 15 wt% of tributyrin, using a Haake mixer and then compression molded into ~150 µm films. We found that the migration level of all of the studied blends was below check intended meaning retained in non-polar simulants, while only plasticized blends could withstand the contact with polar solvents. The disintegration of all of the materials in compost at 58 °C was completed within 42 days; the plasticized PHB underwent the fastest degradation, taking only 14 days. The presence of the TB plasticizer speeded up the degradation process. Different degradation mechanisms were identified for PLA and PHB. To evaluate the annealing effect separately from bacteria degradation, the influence of temperature on materials in the absence of a compost environment was also studied. With the increasing time of degradation in compost, both melting temperature and maximum degradation temperature progressively decreased, while the crystallinity degree increased, indicating that the samples were definitely degrading and that the amorphous regions were preferentially eroded by bacteria.

RESUMEN

In this study, poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(l-lactide) (PLA) microspheres containing ibuprofen were prepared with the aim of prolonging the drug release. The oil-in-water (O/W) emulsion solvent evaporation technique was used, varying the polymer ratio. All formulations provided spherical particles with drug crystals on the surface and a porous and rough polymeric matrix when PHBV was used and smooth external surface when prepared with PLA. The in vitro dissolution profiles show that the formulation containing PHBV/PLA at the proportion of 30/70 presented the best results in terms of prolonging the ibuprofen release. The analysis of the concentration of ibuprofen in the blood of rats showed that maximum levels were achieved at between one and two hours after administration of the immediate-release form (pure drug), while the prolonged microspheres led to a small amount of the drug being released within the first two hours and reached the maximum level after six hours of administration. It was concluded that it is possible to prolong the release of ibuprofen through its incorporation into PHBV/PLA microspheres.

No presente estudo foram preparadas microesferas de poli(hidroxibutirato-co-hidroxivalerato) (PHBV) e poli(ácido láctico) (PLA) com o objetivo de prolongar a liberação do ibuprofeno, utilizado como fármaco modelo. Empregou-se o método de emulsificação e evaporação do solvente óleo em água (O/A), variando-se a proporção entre os polímeros. Todas as formulações originaram partículas esféricas com cristais de fármaco aderidos à superfície externa. As microesferas apresentaram superfície rugosa e porosa, quando o PHBV foi utilizado, e superfície externa lisa, quando preparadas com o PLA. Os perfis de dissolução in vitro evidenciaram que a formulação que continha PHBV/PLA na proporção de 30/70 apresentou melhores resultados para prolongar a liberação do ibuprofeno. Através da análise da concentração de ibuprofeno no plasma de ratos, após administração oral, verificou-se que os níveis máximos ocorreram entre 1 e 2 horas após a administração de ibuprofeno não encapsulado, enquanto o fármaco presente nas microesferas atingiu um pico máximo após 6 horas da administração. Conclui-se, portanto, que é possível prolongar a liberação do ibuprofeno após a sua incorporação às microesferas preparadas com os polímeros PHBV e PLA, especialmente na proporção de 30/70.

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