Acidochromic Free-Standing Multilayered Chitosan-Pyranoflavylium/Alginate Membranes toward Food Smart Packaging Applications


Food smart packaging has emerged as a promising technology to address consumer concerns regarding food conservation and food safety. In this context, we report the rational design of azide-containing pyranoflavylium-based pH-sensitive dye for subsequent click chemistry conjugation toward a chitosan-modified alkyne. The chitosan-pyranoflavylium conjugate was characterized by infrared (ATR-FTIR), ultraviolet–visible (UV–vis), nuclear magnetic resonance (NMR) spectroscopies, and dynamic light scattering (DLS), as well as its thermodynamic parameters related to their pH-dependent chromatic features. The fabrication of thin-films through electrostatic-driven layer-by-layer (LbL) assembly technology was first screened by quartz crystal microbalance with dissipation monitoring (QCM-D) onto gold substrates, and then free-standing (FS) multilayered membranes from polypropylene substrate were obtained using a homemade automatic dipping robot. The membranes’ characterization included morphology analysis and thickness evaluation, assessed by scanning electron microscopy (SEM), pH-responsive color change performance tests using buffer solutions at different pH levels, and biogenic amines-enriched model solutions, demonstrating the feasibility and effectiveness of the chitosan-pyranoflavylium/alginate biomembranes for food spoilage monitoring. This work provides insights toward the development of innovative pH-responsive smart biomaterials for advanced and sustainable technological packaging solutions, which could significantly contribute to ensuring food safety and quality, while reducing food waste.


Mariana Cunha, Victor de Freitas, João Borges, João F. Mano, João M. M. Rodrigues, Luís Cruz

nossos autores


The authors thank Dr. Zélia Azevedo for the MS analysis and Dr. Mariana Andrade for the NMR analysis. This work was supported by the Associate Laboratory for Sustainable Chemistry, Clean Processes and Technologies LAQV. The latter is financed by national funds from UIDB/50006/2020. This work was funded by the European Union’s Horizon Europe research and innovation programme under the grant agreement No. 101079482 (“SUPRALIFE”). This work was also developed under the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020 (DOI 10.54499/UIDB/50011/2020), UIDP/50011/2020 (DOI 10.54499/UIDP/50011/2020) & LA/P/0006/2020 (DOI 10.54499/LA/P/0006/2020), financed by national funds through the FCT/MEC (PIDDAC). L.C. (DL 57/2016/CP1334/CT0008), J.M.M.R. (CEEC-IND/01363/2018, DOI 10.54499/CEECIND/01363/2018/CP1559/CT0022) and J.B. (2020.00758.CEECIND, DOI 10.54499/2020.00758.CEECIND/CP1589/CT0007) gratefully acknowledge FCT for their research contracts.

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