Dados do Trabalho

Título

Easy-to-manufacture sustainable coatings based on chitosan/HPMC containing silver nanoparticles obtained via green chemistry for the potential antimicrobial control of Moniliophthora roreri in cocoa pods

Introdução

The productivity of cocoa crops in Colombia is preponderantly affected by the phytopathogenic fungus Moniliophthora roreri, which can lead to total crop loss.

Material e Métodos

In this study, seven (7) different types of silver nanoparticle (AgNP)-containing chitosan/hydroxypropyl methylcellulose (Chi/HPMC)-based coatings were proposed to mitigate the aforementioned issue. The AgNPs were synthesized via green chemistry using four (4) different plant extracts from Eucalyptus camaldulensis (E), Gliricidia sepium (commonly called Matarratón, M), Azadirachta indica (known as nim or neem in Latin America, N) and the epidermis of Aloe vera (also recognized as Sabila, S) for the potential antimicrobial control of M. roreri in cocoa pods. All coating formulations were developed by the casting methodology at room temperature (25 oC) containing glycerol as a plasticizer. The developed coating systems were labeled as Chi, HPMC, Chi/HPMC, Chi/HPMC+E, Chi/HPMC+M, Chi/HPMC+N, and Chi/HPMC+S. The AgNPs were characterized by attenuated total reflectance Fourier transform infrared (ATR/FTIR) spectroscopy, thermogravimetric analysis (TGA), and X-ray diffraction (XRD). Meanwhile, the coatings were analyzed in terms of ATR/FTIR, TGA, XRD, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), water contact angle (WCA), and opacity.

Resultados e Discussão

The results obtained demonstrated that the AgNPs synthesized utilizing M and N as reducing agents were coated by natural phytocomponents of the extracts, i.e. the AgNPs manufactured employing E and S were purer than those made as M or N. The most hydrophilic coating was HPMC. Nonetheless, the Chi/HPMC coating was the most superficially hydrophobic.

Conclusão

This was influenced by Chi-HPMC hydrogen bonding interactions, which led to higher thermal resistance of the materials. It should be noted that, despite the superficial physicochemical differences of the materials, morphologically all the coatings showed smooth surfaces without apparent changes between the samples. In contrast, all AgNP-containing coating systems were more opaque than those coating systems not containing nanoparticles.