Polylactic acid–based materials encapsulating carvacrol obtained by solvent casting and electrospinning

Abstract

Polylactic acid (PLA) dissolved (15 wt.%) in ethyl acetate (EtAc): dimethyl sulfoxide (DMSO) binary systems (0:1; 1:3, and 2:3 v/v) was used as carrier to obtain carvacrol (CA)-loaded (20 wt.% with respect to PLA) matrices by electrospinning, in comparison with solvent casting. Field emission scanning electron microscopy (FESEM) observations showed that CA-loaded electrospun fibers were thinner than the CA-free ones, and their encapsulating efficiency (EE) increased when EtAc was present in the solvent. The cast films had higher EE (up to 89%) than the electrospun mats (maximum 68%). Thermogravimetric analysis and differential scanning calorimetry revealed that CA-free matrices retain more solvent than the samples with CA; this effect is being more noticeable in fibers rather than in cast films. The thermal analysis revealed stronger retention forces of CA in the fibers than in the cast material and the CA plasticizing effect in the PLA matrices, in accordance with its retained amount.

Natural antimicrobials and antioxidants added to polylactic acid packaging films. Part I: Polymer processing techniques

“…Meanwhile, Tampau et al. (2020) observed that the incorporation of carvacrol at 20 wt% in a PLA solution resulted in thinner fibers than those obtained without AA (Tampau et al., 2020).…”

“…Regarding the solvent, Tampau et al. (2020) reported that the amount of carvacrol increased from 52% to 68% in PLA nanofibers when ethyl acetate/DMSO 2:3 was used instead of DMSO. This fact was attributed to the lower boiling point of the ethyl acetate that increased the solvent evaporation rate and enhanced the solidification of the fibers, entrapping the AA and preventing its evaporation (Tampau et al., 2020).…”

“…The casting-solvent procedure has gained interest for obtaining active materials because melting extrusion processes are very aggressive due to the high temperatures that can increase AA losses by evaporation or thermal degradation. In this context, encapsulation efficiencies (percentage of total extracted AA from the polymer with respect to the theoretical AA content) of 78%, 89%, and 76% have been reported incorporating carvacrol (20 wt% respect to PLA) in PLA solution (15 wt%) by casting using ethyl acetate:dimethyl-sulfoxide (DMSO) binary systems of 0:1, 1:3 and 2:3 v/v, respectively (Tampau et al, 2020). Meanwhile, Morelli et al (2015) reported a weight loss of copaiba oil between 16 and 65 wt% when its nominal content varied from 10 to 50 wt%, attributed to the AA volatilization during casting and a small oil exudation from the films.…”

“…For example, the amount of AITC into PLA nanofibers decreased from 95% to 45% when the AITC concentration in the solution increased from 5 to 25 wt% attributed to the phase separation of AITC and PLA during processing (Kara et al, 2016). Regarding the solvent, Tampau et al (2020) reported that the amount of carvacrol increased from 52% to 68% in PLA nanofibers when ethyl acetate/DMSO 2:3 was used instead of DMSO. This fact was attributed to the lower boiling point of the ethyl acetate that increased the solvent evaporation rate and enhanced the solidification of the fibers, entrapping the AA and preventing its evaporation (Tampau et al, 2020).…”

Effects of D-lactide content and molecular weight on the morphological, thermal, and mechanical properties of electrospun nanofiber polylactide mats

“…1,2 PLA and its compounds can be used in wide commodity and engineering applications due to its good mechanical, physical, and thermal properties. 3–6 In this context, PLA could also be employed for the production of nanofibers through electrospinning process with the potential use in the fields of tissue engineering, 7–11 drug delivery, 12–15 pH indicator, 16,17 filtration, 18,19 separation, 20,21 sensor application, 22 and food packaging. 23,24…”