High-pressure gas-assisted absorption of protein within biopolymeric micro-patterned membrane

The loading of bio-molecules within polymeric matrices, such as particles, sponges or thin membranes, by completely solvent-free processes has an enormous interest in biomedical engineering applications, in particular, for the production of drug carriers and biomimetic scaffolds. In this research, we developed a process based on the use of high-pressure carbon dioxide (CO2) in order to absorb bioactive molecules within poly(lactic-co-glycolic acid) (PLGA). A dye, methylene blue, was used to optimize process conditions, whereas lysozyme was used to evaluate the protein-loading efficiency. The in situ UV–vis measurements of the gas-assisted absorption of methylene blue showed that the dye concentration within the polymer increased tenfold with respect to the control sample, after 35 min at a relatively low pressure of 2.0 MPa. Experimental measurements in the range of 0.1–6.7 MPa, and at 308 and 313 K, showed that the protein loading was highly enhanced by CO2 assisted absorption, whereas no detectable amount of protein was observed in the control. This gas-assisted technique is a completely solvent-free process, operates at mild temperature conditions (<313 K), and is particularly promising for the absorption of thermo-degradable molecules within PLGA membranes without affecting their morphology at macro- and micro-scale.