Preparation of polymeric particles in CO₂ medium using non-toxic solvents: discussions on the mechanism of particle formation

Abstract

13The aim of this work was to develop a novel formulation method, termed modified-PGSS (modified-14Particle from Gas Saturated Solution), for the encapsulation of protein into polymeric microparticles in 15 CO 2 media. In this study, the isosorbide dimethyl ether (DMI), a non-toxic water-miscible solvent, was 16 used for the formulation and lysozyme was chosen as a model protein for encapsulation into PLGA 17 microparticles. Firstly, the mechanism of particle formation has been extensively studied and was 18 discussed in detail. Phase behavior was investigated by measuring the solubility of CO 2 in DMI and 19 volumetric expansion of DMI saturated in CO 2 . Here, we demonstrated the consistency of the 20 experimental values with the data obtained from the mathematical (such as the neural network) and 21 thermodynamic (such the Peng-Robinson equation of state) models. These models were built to develop 22 predictive tools in the chosen experimental space for microparticles formulation. Furthermore, these 23 microparticles were characterized in terms of size and zeta potential. The morphology and protein 24 distribution within PLGA microparticles were determined using scanning electron microscopy and 25 confocal microscopy respectively. High encapsulation efficiency (65%) was obtained as confirmed by 26 lysozyme quantification using a specific bioassay (M. lysodeikticus). Moreover, the in vitro protein release 27 profile from loaded microparticles was presented. In this study, we reported an innovative and green 28 process for lysozyme encapsulation into PLGA microparticles. Thus, this process could be applied to the 29 encapsulation of therapeutic proteins requiring protection and controlled release such as growth factors for 30 regenerative medicine. 31 32

Sustained release of TGF-β1 from biodegradable microparticles prepared by a new green process in CO2 medium

“…Encapsulation of TGF-b1 into PLGA microparticles was adapted from an emulsification/extraction process in CO 2 medium developed in our previous work ( Fig. 1) (Tran et al, 2014). Briefly, 0.4 mL of the suspension of TGF-b1 precipitates in polymer solution was introduced into a 14 mL view-cell (1), which was kept at the operating temperature (26 AE 0.1 C) by a thermostated water bath…”

“…It should be noted that the encapsulation process is performed under mild conditions of pressure and temperature (60 bar, 26 C) thanks to the modeling of CO 2 solubility in DMI presented in our previous work (Tran et al, 2014). During the emulsification step, the pH of dispersing phase was buffered to be near to the protein isoelectric point pI = 8.6).…”

“…Therefore, the development of halogenated solvent-free encapsulation methods is of great interest. From this point of view, protein encapsulation into PLGA particles using supercritical or compressed CO 2 -based processes emerges as a promising technology to completely eliminate these solvents or at least to minimize their use (Jordan et al, 2010;Tran et al, 2014;Tran et al, 2013).…”

Polymer-Based Protein Delivery Systems for Loco-Regional Administration

“…Generally, they are formed by removing the solvent from a polymer solution that leads to the precipitation of the polymer molecules. Methods that have been employed to produce porous scaffolds include freeze-drying (86), particulate leaching (87) and gas foaming (88). In the first method, a polymer solution is initially frozen at a sub-zero temperature inside an airtight chamber.…”

“…Traditionally, the gas bubbles can be formed in situ by adding into the polymer phase a foaming agent such as ammonium bicarbonate, which generates inert gas such as CO2 when the pH of the system is decreased. A porous scaffold is formed upon removal of the dispersed gas bubbles from the polymer phase (88). Recently, supercritical fluids have been used as an alternative foaming agent.…”