Ascidian-Inspired Supramolecular Cellulose Nanocomposite Hydrogels with Antibacterial Activity

Abstract

The design of ultratough hydrogels has recently emerged as a topic of great interest in the scientific community due to their ability to mimic the features of biological tissues. An outstanding strategy for preparing these materials relies on reversible and dynamic cross-links within the hydrogel matrix. In this work, inspired by the composition of ascidians’ tunic, stretchable supramolecular hydrogels combining poly(vinyl alcohol), green tea-derived gallic acid, and rigid tannic acid-coated cellulose nanocrystals (TA@CNC) were designed. The addition of TA@CNC nanofillers in concentrations up to 1.2 wt % significantly impacted the mechanical and viscoelastic properties of the hydrogels due to the promotion of hydrogen bonding with the polymer matrix and polyphenols π–π stacking interactions. These supramolecular associations endow the hydrogels with excellent stretchability and strength (>340%, 540 kPa), low thermoreversible gel–sol transition (60 °C), and remolding ability, while the natural polyphenols provided potential antibacterial properties. These versatile materials can be anticipated to open up new prospects for the rational design of polyphenol-based cellulosic hydrogels for different biomedical applications.

Natural, Biocompatible, and 3D-Printable Gelatin Eutectogels Reinforced with Tannic Acid-Coated Cellulose Nanocrystals for Sensitive Strain Sensors

“…52 This trend is reasonably expected because the TA that coats the CNCs promotes H-bonding formation and thus enhances the adhesion energy values. 33 Although the tackiness values of BioeGels are lower than those of recently reported gelatin eutectogels 18 but higher than that of CNC nanocomposite hydrogels, 33,52 the magnitude of the adhesion force of our ionic materials is good enough to be able to adhere to human skin. 53,54 Figure 4C shows the cyclic adhesion test on porcine skin for the most sticky gel, BioeGel4%, observing an adhesion increase with successive cycles.…”

“…Typical bands of TA at 1701 (C�O ν); 1607, 1535, and 1448 cm −1 (aromatic C−C skeletal vibrations); and 870 and 755 cm −1 (aromatic C−H δ oop, C�C δ) show slight bathochromic shifts, indicating that TA is coating the CNCs. 33 The IR bands of ethaline can be appreciated in all BioeGels spectra due to its relatively high concentration (Figure 1C). The band at 3500−3000 cm −1 in the BioeGel spectra is more intense than in ethaline/TA@CNC spectra due to the contribution of Amide A (N−H ν) from gelatin.…”

“…Also, vibrational modes at 1100–900 cm –1 can be appreciated and assigned to C–O–C vibrations of CNCs. Typical bands of TA at 1701 (CO ν); 1607, 1535, and 1448 cm –1 (aromatic C–C skeletal vibrations); and 870 and 755 cm –1 (aromatic C–H δ oop, CC δ) show slight bathochromic shifts, indicating that TA is coating the CNCs …”

“…Preparation of TA@CNC. CNCs coated with TA were prepared according to Carnicero et al 33 Briefly, 1 g of CNCs was dispersed in 100 mL of distilled water using magnetic stirring and sonicated for 10 min. Then, the pH of the dispersion was adjusted to 8.0, using tris buffer (1 M).…”

“…In this sense, tannic acid-coated cellulose nanocrystals (TA@CNC) are an excellent option for enhancing the mechanical performances of composites as biobased nanofillers owing to their rigid crystalline core, H-bond forming ability of the natural polyphenol, and high surface area. Indeed, TA@CNC have already demonstrated their outstanding reinforcer capacity in several nanocomposite hydrogels. − Interestingly, TA has shown an extraordinary binding affinity for proteins, and a superior reinforcing performance could be expected for TA@CNC compared to that for pristine CNCs. − …”