Functionalization of polycaprolactone/hydroxyapatite scaffolds with Usnea lethariiformis extract by using supercritical CO2

Investigation of an integrated supercritical fluid extraction and supercritical solvent impregnation process for fabrication of microporous polycaprolactone-hydroxyapatite (PCL-HA) scaffolds with antibacterial activity is presented. The HA content and particle size as well as the operating conditions of the integrated process is optimized regarding the amount of impregnated antibacterial agent (Usnea lethariiformis extract) in the PCL-HA matrix, scaffold morphology and antibacterial activity against methicillin resistant Staphylococcus aureus (MRSA) strains. High pressure differential scanning calorimetry (HP-DSC) assay reveals that an increasing amount of HA results in decreasing melting temperature as well as crystallinity at an operating pressure of 17 MPa. The PCL-HA composites with micrometric sizes of the HA particles are convenient for being processed by the integrated process due to the simple preparation, a good interaction between the PCL matrix and filler and the advantageous impact on sorption. The scaffold obtained from PCL-HA with 20% of the HA shows the highest impregnation yield at 17 MPa and 35 degrees C (5.9%) and subsequently also the best bactericidal effect on the tested MRSA strains at an initial bacterial inoculum of 2 x 10(-4) CFU/m

Development of polycaprolactone scaffold with antibacterial activity by an integrated supercritical extraction and impregnation process

The present study is aimed to develop a process for production of functionalized scaffolds impregnated with natural compounds extracted from Patagonian Usnea lichen. A setup for an integrated supercritical CO2 extraction of natural compounds with posterior impregnation on solid matrices (polycaprolactone, PCL) is developed and presented here. In order to establish optimized operating conditions, supercritical extraction of Usnea as well as sorption kinetics and resulting material properties have been studied separately first. Usnea extracts isolated by supercritical carbon dioxide at 30 MPa and 40 degrees C have shown strong antibacterial activity with values of the minimum inhibitory concentration (MIC) ranging from less than 1.25 mu g/mL to 320 mu g/mL against Listerin innocua and Methicillin-resistant Staphylococcus (MRS) strains. Useful scaffolds of PCL for tissue engineering containing a porous structure with pore diameters between 150 and 340 pm can be obtained when PCL is exposed to carbon dioxide at 35 degrees C and 15 MPa. The degree of crystallinity of functionalized PCL was shown to be influenced by the incorporated antibacterial agent. The presented results showed that the impregnated PCL samples are promising bactericidal compounds against L innocua. Screening of antibacterial activity of functionalized PCL against a Methicillin-resistant Staphylococcus aureus (MRSA) strain showed a higher activity when a low bacterial inoculum level (2 x 10(4) Colony-forming Units/mL [CFU/mL]) was assayed

Biomimetic Mg-substituted hydroxyapatite: from synthesis to in vivo behaviour

The incorporation of magnesium ions (in the range 5-10 mol% in respect to Ca) into the hydroxyapatite structure, which is of great interest for the developing of artificial bone, was performed using magnesium chloride, calcium hydroxide and phosphoric acid, as reactants. Among the synthesized powders, the synthetic HA powder containing 5.7% Mg substituting for calcium was selected, due to its better chemico-physical features, and transformed into granules of 400-600 microm, for biocompatibility tests (genotoxicity, carcinogenicity, toxicity, in vitro cytotoxicity and in vivo skin irritation-sensitization tests). In vivo tests were carried out on New Zealand White rabbits using the granulate as filling for a femoral bone defect: osteoconductivity and resorption were found to be enhanced compared to commercial stoichiometric HA granulate, taken as control