“Biohybridization of nanohybrid cellulose-based hydrogels with silver nanoparticles bearing antibacterial activity”

In this study, cellulose extracted from four phyto-based waste sources - Lablab purpureus pods, Phoenix dactylifera seeds, sugarcane bagasse, and Camellia sinensis residues was utilized to synthesize cellulose-based hydrogels. Silver nanoparticles (AgNPs) were green-synthesized using the same phyto-based extracts from Lablab purpureus pods (LPNPs), Phoenix dactylifera seeds (PDNPs), Sugarcane bagasse (SBNPs), and Camellia sinensis (CSNPs), and incorporated into the hydrogel matrix to produce antimicrobial nanohybrid hydrogels. AgNPs synthesis was confirmed by UV-Visible spectroscopy, with characteristic surface plasmon resonance peaks in the range of 410-440 nm. Structural and physicochemical characterization were performed using FTIR, XRD, SEM, DLS, and EDX analyses. FTIR confirmed hydroxyl, carboxyl, and ester functional groups associated with the cellulose-grafted polymer network. XRD patterns indicated the amorphous nature of the hydrogels, with additional diffraction peaks in nanohybrid samples confirming crystalline AgNPs embedded within the matrix. SEM revealed smooth morphology for plain hydrogels and increased surface roughness upon nanoparticle incorporation. Swelling studies demonstrated water absorption in the range of 3007-5129% for plain hydrogels and 2420-3702% for nanohybrid hydrogels in distilled water, with additional swelling assessments performed under varying pH and ionic strength conditions. Porosity values ranged from 8.12 to 17.38% for plain hydrogels and 4.06-10.43% for nanohybrid hydrogels. Gel fractions ranged from 76 to 90% for plain hydrogels and 76-88% for nanohybrid hydrogels. Crosslink density ranged from 2.18 × 10 −6 to 5.59 × 10 −6 mol/cm 3 for plain hydrogels and 3.87 × 10 −6 to 8.26 × 10 −6 mol/cm 3 for nanohybrid hydrogels, indicating increased network compactness upon AgNP incorporation. Compression studies revealed compressive stress of 0.44-0.58 MPa for plain hydrogels and 0.20-0.26 MPa for nanohybrid hydrogels. EDX confirmed C and O as major elements across all samples, with Ag detected at approximately 0.4-0.5 wt% in nanohybrid hydrogels, verifying successful nanoparticle incorporation. Antibacterial activity evaluated by the agar well diffusion method demonstrated zones of inhibition against Bacillus cereus in the range of 1.07-1.50 cm, Salmonella typhi in the range of 1.03-1.80 cm, Escherichia coli in the range of 0.97-1.63 cm, and Staphylococcus aureus in the range of 0.62-1.22 cm, with LPNPs exhibiting the highest antimicrobial activity which was also confirmed with broth dilution assay. These findings demonstrate the potential of phyto-derived cellulose and green-synthesized AgNPs for developing sustainable nanohybrid hydrogels with promising antimicrobial and sanitary applications.