ABSTRACT
The usage of conjugated materials for the fabrication of foams intended to be used as therapeutic scaffolds is gaining relevance these days, as they hold certain properties that are not exhibited by other polymer types that have been regularly used until the present. Hence, this work aims to design a specific supercritical CO2 foaming process that would allow the production of porous polymeric devices with improved conductive properties, which would better simulate matrix extracellular conditions when used as therapeutic scaffolds (PLGA-PEDOT:PSS) systems. The effects of pressure, temperature, and contact time on the expansion factor, porosity, mechanical properties, and conductivity of the foam have been evaluated. The foams have been characterized by scanning electron and atomic force microscopies, liquid displacement, PBS degradation test, compression, and resistance to conductivity techniques. Values close to 40% porosity were obtained, with a uniform distribution of polymers on the surface and in the interior, expansion factors of up to 10 orders, and a wide range of conductivity values (2.2 × 10-7 to 1.0 × 10-5 S/cm) and mechanical properties (0.8 to 13.6 MPa Young's modulus in compression test). The conductive and porous scaffolds that have been produced by supercritical CO2 in this study show an interesting potential for tissue engineering and for neural or cardiac tissue regeneration purposes due to the fact that electrical conductivity is a crucial factor for proper cell function and tissue development.
ABSTRACT
Plant leaves, such as those from Mangifera indica, represent a potential utilization of waste due to their richness in bioactive compounds. Supercritical CO2 allows these compounds to be incorporated into various matrices by impregnation. Combined with its ability to generate polymeric scaffolds, it represents an attractive strategy for the production of biomedical devices. For this purpose, conjugated polymeric scaffolds of biodegradable PLGA (poly(lactic-co-glycolic acid)) and PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)), generated in situ by foaming, were employed for the supercritical impregnation of ethanolic mango leaves extract (MLE) in tissue engineering as a potential application. The extraction of MLE was performed by Enhanced Solvent Extraction. The effects of pressure (120-300 bar), temperature (35-55 °C), and depressurization rate (1-50 bar/min) on the physical/conductive properties and the impregnation of MLE were studied. The scaffolds have been characterized by liquid displacement, scanning electron microscope, resistance to conductivity techniques, measurements of impregnated load, antioxidant capacity and antimicrobial activity. Porosity values ranging 9-46% and conductivity values between 10-4-10-5 S/cm were obtained. High pressures, low temperatures and rapid depressurization favored the impregnation of bioactive compounds. Scaffolds with remarkable antioxidant activity were obtained (75.2-87.3% oxidation inhibition), demonstrating the ability to inhibit S. aureus bacterial growth (60.1 to 71.4%).
ABSTRACT
Artificially contaminated soil with four different polynuclear aromatic hydrocarbons (acenaphthene, phenathrene, anthracene and fluoranthene) has been separately treated by two different processes: (A) concentrated hydrogen peroxide at mild conditions of temperature (343-393 K) and pressure (0.5 MPa) and (B) hot water extraction at relatively high temperature (523-657 K) and pressure (10 MPa). Both methods achieve acceptable PAH removal percentages from soil. Acenaphthene (the most soluble PAH) is completely removed with treatment A regardless of the operating conditions used. Under optimum conditions, the rest of PAHs are also eliminated to a high extent with both technologies. Temperature and hydrogen peroxide amount seem to play a major role in process A. Similarly, temperature and water flowrate are the most influencing parameters in process B. In the latter case, a post-stage for the extracting water cleaning is required.
