Supercritical Impregnation of Olive Leaf Extract in Poly(L-lactic acid-co-caprolactone) Filaments: An Environmentally Friendly Approach to Obtaining Active Biomedical Materials

Abstract

The valorization of by-products in the olive sector has increasingly become the focus of business and research in the context of biorefineries. This work evaluates the recovery of bioactive compounds from olive leaves and their subsequent incorporation into poly(L-lactic- acid-co-caprolactone) (PLCL) filaments through supercritical impregnation. Obtaining an olive leaf extract (OLE) using enhanced solvent extraction at a high pressure (ESE with CO₂/ethanol 1:1 v/v) resulted in higher yields and concentrations of bioactives with high antioxidant and anti-inflammatory activity. No significant differences were found between the extracts obtained with different water regimes (irrigated and dry land). The supercritical impregnation of PLCL filaments showed that a low depressurization rate is essential to avoid material deformation, while the impregnation pressure and temperature influenced the OLE loading and antioxidant activity of the filaments. In vitro release studies showed the prolonged release of active compounds over 90 days, and the kinetics best fit the Korsmeyer-Peppas model, suggesting a diffusion mechanism. These results validate supercritical impregnation as a promising strategy for the development of OLE-active PLCL filaments with potential for biomedical applications requiring sustained therapeutic release.

Keywords: active compound delivery systems; olive leaf extract; poly(L-lactic-co-caprolactone) (PLCL); supercritical fluid.

Figure 1

Flow diagram of the extraction/impregnation system used (ABPR: automatic back pressure regulator, T: temperature, P: pressure, TIC: temperature integrated controller, PIC: pressure integrated controller).

Figure 2

DPPH antioxidant activity of the obtained OLE from lands of different water regimes (dry and irrigated). The results are presented as means and standard deviations (n = 3).

Figure 3

Anti-inflammatory capacity of the obtained OLE from lands of different water regimes (dry and irrigated). The results are presented as means and standard deviations (n = 3).

Figure 4

(a) Swelling and (b) external appearance of the impregnated filaments when operated at a high depressurization rate. The swelling results are presented as means and standard deviations (n = 3).

Figure 5

(a) Swelling and (b) external appearance of the impregnated filaments at low depressurization rate. The swelling results are presented as means and standard deviations (n = 3).

Figure 6

(a) OLE loading and (b) DPPH antioxidant activity on the impregnated filaments when operated at a low depressurization rate. The results are presented as means and standard deviations (n = 3).

Figure 7

Longitudinal section at 100× and 1000× magnification of control filament (a,b) and filament impregnated at 100 bar/75 °C (c,d); 250 bar/75 °C (e,f) and 400 bar/75 °C (g,h).

Figure 8

Cross section at 500× magnification of control filament (a) and filament impregnated at 100 bar/75 °C (b); 250 bar/75 °C (c) and 400 bar/75 °C ((d,e) (100×)).

Figure 9

(a) Cumulative release (%) of impregnated PCLC filaments at different operation conditions (the results are presented as means and standard deviations (n = 3)). Cumulative % bioactive compound release from filaments impregnated at (b) 100 bar, (c) 250 bar, and (d) 400 bar.

Figure 10

Anti-inflammatory capacity of the 60-day liberation chosen samples. The results are presented as means and standard deviations (n = 3).