In the fields of medical and pharmaceutical research, aerogels are attaining great attention, both for tissue regeneration and/or drug delivery, because they afford good properties for this purpose: provide mechanical support, allow cellular interactions, are biodegradable and can also be used to deliver active compounds to the area of the implant. Besides, they must be formulated from natural, non-toxic products and green processes to avoid introducing toxic substances in the human body.
In this context, supercritical fluid processes offer a good alternative in the formation of aerogels, because it is possible to obtain controlled porosity and pore size at mild operating conditions with small changes of pressure and temperature. Also, these techniques do not require high quantities of organic solvents and they are easily removed when the system is decompressed. Besides, by supercritical fluid processes, impregnation of active compounds into the matrix can be done at the same time than its synthesis.
In this work, which was developed in the 3B’s research group of the University of Minho under the supervision of Ana Rita C. Duarte and Rui L. Reis, β-glucan scaffolds were produced by supercritical drying and foaming of hydrogels with supercritical CO2. For the sake of comparison, aerogels are also obtained by a conventional process, i.e. freeze-drying. Biopolymers are widely used for tissue engineering, however very few works study the potential of β-glucans in these applications. Barley and yeast β-glucans were chosen in this work because they could be processed by different techniques due to their different solubility in water, and thus distinct product properties were attained with each one. Also, dexamethasone was introduced into the scaffold as a model active compound, due to its ability to differentiate stem cells towards osteogenic lineage.
Characterization of the scaffolds produced by any of the aforementioned methods was performed studying their morphology by SEM (Fig. 1) and X-ray microtomography, their strength by compression tests, and their degradation rate on simulated physiological fluids.