Biomedical Engineering Reference
In-Depth Information
Fig. 2
Structural formula of employed bioactive substances and polymeric biomaterials
˙
(for films) and 250
m (for foams). After drying, polymeric samples were
cut in rectangular pieces of approximately 10
15
5 mm and weighing approximately
˙
˙
3
1 mg, for foams and films, respectively.
The supercritical impregnation apparatus used in this work was already described
in the literature [
44
,
63
-
65
]. A schematic representation of its main components is
given in Fig.
3
. In general terms, it is comprisedofacompressedair-operatedCO
2
liquid pump, a visual high-pressure stainless steel impregnation cell, a thermostatic
controlled water bath and a magnetic stirring plate as an auxiliary tool to dissolve
and to homogenize the high pressure mixture (bioactive compounds plus scCO
2
/co-
solvent).The procedure consists in placing weighed samples of CBC (or AGA)
foams or films into the high-pressure cell that already contained known amounts
of quercetin and/or thymol. The amounts of employed bioactive compounds were
established by taking into account the available cell volume and the compounds
solubility in scCO
2
(at the tested experimental conditions) and by using amounts
that corresponded to 10% of the saturation solubility limit. Ethanol (EtOH), 10%
v/v, was used as the co-solvent for the quercetin system and in order to increase
its solubility in scCO
2
. The system is then closed and pressurized up to the
pre-established operational pressure and after bath temperature stabilization. Two
different operational conditions (10 MPa/303 K and 20 MPa/323 K) were tested
in order to study their influence on the amounts of loaded bioactive compounds.
The system is then maintained in static conditions for 3 h allowing the diffusion of
the solvent (pressurized CO
2
or CO
2
/co-solvent mixture), saturated with quercetin
and/or thymol, through the polymeric matrix. After this period, the solvent is
removed by slow depressurization (1 MPa.min
1
) in order to not alter or damage
the processed polymeric samples.
0.5mgand5
