Use of poly(N-isopropylacrylamide) nanohydrogels for the controlled release of pimaricin in active packaging.

Unlabelled: We propose here a delivery drug-polymer system using poly(N-isopropylacrylamide) (PNIPA) nanohydrogels that enables pimaricin to be protected from hostile environments and allows the controlled release of the antifungal through environmental stimuli. We synthesized 2 nanohydrogels, 1 with 100% N-isopropylacrylamide (PNIPA(5)) and 1 with 80% N-isopropylacrylamide copolymerized and 20% acrylic acid (PNIPA-20AA(5)). Both were then, loaded with a pimaricin aqueous solution. The pimaricin release profiles of these 2 nanohydrogels were considerably different: PNIPA(5) released 10% and PNIPA-20AA(5) released 30% with respect to the free pimaricin release. Moreover, the diffusion experiments showed that pimaricin was released from the PNIPA-20AA(5) nanohydrogel for up to 3 times longer than free pimaricin. Therefore, incorporating acrylic acid as comonomer into the PNIPA nanohydrogel resulted in a slower but more continuous release of pimaricin. The highest pimaricin levels were reached when the most hydrophilic nanohydrogel was used. The bioassay results showed that the pimaricin-nanohydrogel system was highly effective in inhibiting the growth of the indicator strain in conditions of thermal abuse. The spoilage in acidified samples stored under fluorescent lighting was reduced by 80.94% ± 33.02% in samples treated with a pimaricin-loaded nanohydrogel, but only by 19.91% ± 6.68% in samples treated with free pimaricin. Therefore, 2 conclusions emerge from this study. One is that the nanohydrogel delivery system could impede the degradation of pimaricin. The other is that the inhibitory effect of the antifungal on yeast growth is more pronounced when it is added included into the nanohydrogel to the food, especially in an acidic environment.

Practical Application: This article presents relevant results on the use of nanohydrogels in food packaging. Nanohydrogels could provide protection so that the pimaricin remains active for a longer time. They also allow the controlled release of pimaricin, which thus regulates the unnecessary presence of the antifungal in the food.