PCL microspheres based functional scaffolds by bottom-up approach with predefined microstructural properties and release profiles.

Advanced tissue engineering approaches rely upon the employment of biomaterials that integrate biodegradable scaffolds with growth factor delivery devices to better guide cellular activities and enhance tissue neogenesis. Along these lines, here we proposed a bottom-up approach for the realization of bioactive scaffolds with controllable pore size and interconnection, combined with protein-loaded polymeric microcarriers acting as local chrono-programmed point source generation of bioactive signals. Bioactive scaffolds are obtained through the thermal assembly of protein activated poly(epsilon-caprolactone) (PCL) microspheres prepared by double emulsion and larger protein free PCL microspheres obtained by single emulsion. It is shown that the pore dimension, interconnectivity and mechanical properties in compression of the scaffold could be predefined by an appropriate choice of the size of the protein-free microparticles and process conditions. Protein-loaded microparticles were successfully included within the scaffold and provided a sustained delivery of a model protein (BSA). These matrices offer the possibility to concurrently modulate and control the size and extension of the porosity, mechanical properties and the spatial-temporal distribution of multiple bioactive signals.

Engineering of poly(epsilon-caprolactone) microcarriers to modulate protein encapsulation capability and release kinetic.

Drug delivery applications using biodegradable polymeric microspheres are becoming an important means of delivering therapeutic agents. The aim of this work was to modulate the microporosity of poly(epsilon-caprolactone) (PCL) microcarriers to control protein loading capability and release profile. PCL microparticles loaded with BSA (bovine serum albumin) have been de novo synthesized with double emulsion solvent evaporation technique transferred and adapted for different polymer concentrations (1.7 and 3% w/v) and stabilizer present in the inner aqueous phase (0.05, 0.5 and 1% w/v). SEM (scanning electron microscope) and CLSM (confocal laser scanning microscope) analysis map the drug distribution in homogeneously distributed cavities inside the microspheres with dimensions that can be modulated by varying double emulsion process parameters. The inner structure of BSA-loaded microspheres is greatly affected by the surfactant concentration in the internal aqueous phase, while a slight influence of polymer concentration in the oil phase was observed. The surfactant concentration mainly determines microspheres morphology, as well as drug release kinetics, as confirmed by our in-vitro BSA release study. Moreover, the entrapped protein remained unaltered during the protein encapsulation process, retaining its bio-activity and structure, as shown through a dedicated gel chromatographic analytical method.