Making microporous nanometre-scale fibrous PLA aerogels with clean and reliable supercritical CO2 based approaches

•Microporous nanoscale fibrous PLA aerogels are fabricated.•A clean approach based on phase separation and supercritical CO2 drying is proposed.•PLA aerogels have porosity and surface area up to 95% and 95 m2/g.•The fabrication of multi-scaled porous scaffolds for tissue engineering is discussed.

Polylactic acid (PLA) aerogels, with a multiscale structure consisting of nanometre-scale fibres and interconnected micropores, were here fabricated by a novel thermal induced phase separation (TIPS) approach. The developed process is based on a biocompatible route combining ethyl lactate (EL) as a non-toxic solvent for PLA and supercritical CO2 (scCO2) as a clean drying agent. First, PLA was dissolved in EL to prepare homogeneous solutions with a polymer concentration ranging from 3 to 5.5 wt%. Subsequently, TIPS was generated by the controlled decrease of the temperature down to a temperature lower than the solution gelation point. Finally, solvent exchange, alcogel formation and scCO2 drying allowed the manufacture of the desired nanometre-scale fibrous PLA aerogels. In particular, PLA aerogels with homogeneous morphology and constituted by an overall porosity in the range of 90–95% and a specific surface area in the range of 70–95 m2/g were manufactured by modulating polymer concentration in the starting EL solution, gelation temperature and EL extraction conditions. The obtained aerogels possessed a bimodal structure of fibres with a mean length of 100–200 nm coupled with nanopores of a mean diameter down to 2 nm. Finally, the combination of TIPS with gas foaming and porogen leaching techniques was explored as a suitable strategy to obtain multifunctional micro- and nano-sized fibrous PLA materials, suitable of providing biomimetic three-dimensional platforms for tissue engineering scaffolds.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slide