Synergistic effect of cellulose nanofibres and bio- extracts for fabricating high strength sodium alginate based composite bio-sponges with antibacterial properties

This study investigates the synergistic potential of natural bio-extracts for preparing all-natural composite biosponges of sodium alginate (SA) with the reinforcement of a natural bio-nanomaterial i.e., cellulose nanofibres (CNFs). Aqueous suspensions of SA and CNFs in various combinations of bio-extracts (Rice water (Rw) and Giloy extract (Ge)) were freeze-dried to obtain the composite bio-sponges. Composites prepared using Rw resulted in structurally more stable samples with porosity above 75% that showed a compact honeycomb-like microstructure with interlocked CNFs network structures. A significant improvement in mechanical performance (400% increment in compressive strength and 800% increment in modulus) and thermal stability (decomposition temperature reaching up to 240 degrees C from 200 degrees C) for SA based composite bio-sponges was achieved due to the synergistic effect of Rw and CNFs as compared to conventionally prepared sponges in water. Additionally, the use of Ge has resulted in developing antimicrobial surfaces with up to 98% and 90% growth inhibition efficiency for gram-negative and gram-positive bacteria, respectively. Hence, CNFs and bio-extracts together played a competent role in effective tailoring of structural, thermo-mechanical and antibacterial properties of composite bio-sponges.