Preparazione di microcapsule in polimero non biodegradabile tramite tecnologia vibrazionale ad alta efficienza

Purpose Poly(methyl methacrylate) (PMMA) is a biocompatible and non-biodegradable polymer currently widely used as biomedical material. Recently its application as carrier to encapsulate live mammalian cells for treatment of a variety of diseases is of particular interest. The goal of this work is to set up the suitable microencapsulation condition and process parameters in order to achieve a standardized protocol for the encapsulation of viable cell in to PMMA beads by “High efficiency vibrational technology” giving reproducible resuts. Methods PMMA microcapsules were made using Encapsulator B-395 Pro (BUCHI GmBH). Final set up provided PMMA 10% w/w solution in CH2Cl2 extruded through concentric nozzle (400 and 200 μm) under imposed vibration for breaking down the laminar jet into equal size droplets. The droplets were recovered into a biphasic solution made of organic solvent (dodecane) and phosphate buffer saline (PBS), polyvinyl-alcohol 2% (PVA) and Pluronic-127 2% w/w aqueous solution to allow the polymer precipitation and the microcapsules formation. Polymer concentrations tested were between 5 and 15% w/w; polymer to aqueous phases ratios was tested between 1:10 and 1:50. Process parameters such as vibration (frequency and amplitude), electrostatic dispersion (voltage), light intensity of the stroboscope lamp, syringe pump (pump speed and calibration) and stirring/ shaking were optimized in order to obtain homogeneous beads. The microcapsules have been characterized for their morphology (SEM), cytocompatibility and cell proliferation (MTT test), mechanical properties and osmotic resistance. Results The optimize process conditions were polymer concentraction 10% , polymer : aqueous phases ratio 1:50, frequency vibration 2000Hz and 350 V, pump speed 10.5 ml/min. Microcapsules with narrow size distribution in the range 500-800 μm have been obtained with yield process about 60%. The Microcapsules were stable to mechanical and osmotic stresses. MTT test results showed good microcapsules cytocompatibility for PMMA: cells ratio lower than 10 mg/20.000 cells. Morphology characterization by SEM showed smooth microcapsules surface with regular spherical shape. Conclusions The microencapsulation process confirmed to be reproducible and to control bead formation. Future perspectives involve set up of manufacturing process under sterile conditions and process scale-up.