(325d) Production of Nanoporous Materials (Aerogels) From Natural Polymers for Life Science Applications Using Supercritical Fluid Technology

Natural
polymers and derivatives are attractive feedstocks
for life science applications (e.g., pharmaceutics, tissue engineering, cosmetics, food, biotechnology, agriculture) because of their usual biodegradability,
biocompatibility, stability, availability and renewability. Moreover, the
portfolio of existing natural polymers presents a large variety of functional
groups (e.g., carboxylic, sulfonic, hydroxyl, amino
groups), ionic behaviors (anionic, cationic, non-ionic)
and biodegradation profiles. This set of properties
is a promising starting point for the development of tailor-made materials
for controlled release of active substances in different administration routes.
Aerogel technology based on gel extraction with supercritical fluids is herein
presented as a robust processing approach to obtain lightweight dry nanoporous materials (ρ=0.05-0.3 g/cm³) from
natural polymers with outstanding surface area (S_a=100-700 m²/g), open
porosity (ε=90-99 %) and loading capacity of compounds. Natural polymers can undergo gelation by different external stimulii
(temperature, counterions, covalent cross-linkers) using sol-gel technology.
Then, these wet gels can be turn into an aerogel by using a drying technology
able to preserve the original nanoporous structure of the said gel in a dry
form. In this work, the preparation of aerogels from natural
polymers by using gel extraction with supercritical fluids is presented. Materials engineering and step-by-step process optimization
allowed the development of a generic processing approach
to get aerogels from natural polymers with customized morphologies (cylinders,
beads and microspheres) and textural properties (surface area, mesoporosity). The technology was implemented for polysaccharides with different gelation mechanisms (ionotropic, thermotropic) with excellent results: polysaccharides with
the highest reported internal surface area were obtained. The
thus obtained materials were tested for their use as active agents carriers by
supercritical CO₂-assisted impregnation, showing the ability to
adsorb a large amount of API (up to 20 wt%) and the
ability to stabilize them in the amorphous form. Such materials are especially
promising as drug carriers for dry powder inhalation, since their flowability and aerodynamic diameter are significantly
improved by the supercritical drying.