Moldable Oxidized Tannic Acid-Cellulose Nanofiber Hydrogels with antibacterial properties

The synthesis of hydrogels of tannic acid and cellulose nanofibers with moldable, self-healing, and antibacterial properties usually requires additional components such as polyvinyl alcohol and borax, hence leading to undesired byproducts. In this work, a simplified approach was pursued by synthesizing hydrogels solely from oxidized tannic acid (OTA) and TEMPO-oxidized cellulose nanofibers (TOCN). OTA particles were prepared under alkaline conditions, yielding spindle-shaped structures that assembled into flower-like morphologies. FT-IR spectra suggest interfacial interactions between OTA and TOCN dominated by hydrogen bonding, while thermogravimetric analysis indicated an enhanced thermal stability of the hydrogels. Rheological measurements revealed an elastic solid-like behavior (G’>G’’) with a weak frequency dependence, and the TOCN/OTA hydrogel with a 1:2 weight ratio exhibited the highest storage modulus (~150 Pa at 1 rad s -1 ). These hydrogels also displayed regenerative capacity through pressure-assisted re-adhesion after cutting, as well as antibacterial activity, producing a 7.5 mm inhibition halo (distance measured from hydrogel boundary to observed bacterial growth) against Escherichia coli 5 alpha. These findings demonstrate that TOCN/OTA hydrogels can be synthesized without the use of auxiliary polymers or boron-containing crosslinkers, and still achieve desirable mechanical, regenerative, and biocidal properties. These results highlight the potential of these hydrogels in biomedical and environmental applications. • Hydrogels were prepared using oxidized tannic acid and cellulose nanofibers • Crosslinking occurs via ester bonds and hydrogen bonding without additives • Gels show elastic solid-like behavoir and self-healing under applied pressure • Best mechanical performance achieved at a TOCN/OTA ratio of 1:2 • Materials exhibit antibacterial activity against E. coli and potential applications