From:  Functional lignin hydrogels for biosensors and biomedical therapy

 Lignin-based hydrogels in biosensor applications

Hydrogel compositionLignin typeSynthesisPropertiesReferences
Amino-grafted sodium lignosulfonate, polyvinyl alcohol (PVA), in situ grown silver nanoparticles (AgNPs)LignosulfateGrafting amino groups onto lignosulfonate, crosslinking with PVA, followed by in situ AgNP growthStrong antibacterial activity (against Staphylococcus aureus, Escherichia coli), good mechanical strength and elasticity, porous network[29]
Water/glycerol, PEDOT: sulfonated Lignin (PEDOT:SL), PAASulfonated ligninIn-situ radical polymerization of acrylic acid with PEDOT:SL in water/glycerolHigh electrical conductivity, soft, elastic, self-wrinkling, anti-freezing capability, biocompatible (non-toxic to skin and cells)[66]
Fe-sulfonated lignin (SL), Polyacrylic acid (PAA), Lignin-based nanoparticles–Fe3+ chelates, ammonium persulfate (APS)Sulfonated ligninRedox/coordination-initiated polymerization using SL–Fe3+ complex and APS at room temperatureHigh stretchability (1,680%), strong adhesion (36.4 kPa), good conductivity (7.0 × 10–2 S/m), UV-blocking (99.7%), excellent self-healing (up to 85.7% stretch recovery, 98.5% conductivity recovery)[67]
Poly (acrylic acid), poly (vinyl alcohol), lignosulfonate, and LiClLignosulfateRedox polymerization via LS/Fe3+/APS system at room temperature, no external stimulusMechanical strength (1.04 MPa), stretchability (758%), and conductivity (9.81 S/m)[68]
Top layer: quaternary hydroxyethyl cellulose (QHEC), bottom layer: lignosulfonate sodium (LS)–boraxLignosulfonate sodiumLayer-by-layer assembly forming a double-layer hydrogel with oppositely charged polymers enabling ionic crosslinkingTop layer: strong (Young’s modulus ~101.3 kPa), non-adhesive (2.2 kPa), bottom layer: soft (14.2 kPa), adhesive (18.7 kPa), mechanical adaptability, skin compatibility, antimicrobial, biodegradable[69]
Sodium lignosulfonate-silver (Ls-Ag), cellulose nanocrystals, poly(acrylamide), ammonium persulfate (APS)LignosulfateAPS radical polymerization catalyzed by Ls-Ag, forming cellulose-PAM composite hydrogel.High tensile strength (406 kPa), ultra-stretchability (1,880%), self-recovery, robust adhesion, conductivity (~9.5 mS/cm), UV shielding, and antibacterial activity (> 98%)[70]
Aminated lignin (AL), polydopamine (PDA), polyacrylamide (PAM), and biomass carbon aerogel (C-SPF)Animated lignin- lignin extracted from corncobDual-network polymerization combining PAM with AL/PDA and biomass carbon aerogel reinforcementHigh elasticity and self-adhesion, stable over 500 cycles, ultrahigh sensitivity (170 kPa–1), quick response, mechanical strength, Biocompatible and antibacterial[71]
Ca2+-adsorbed tannic acid–sulfonated lignin (Ca2+–TA@SL) and polyacrylamide (PAM)Sulfonated ligninSulfonated lignin doped with tannic acid, Ca2+-adsorbed, then polymerized with PAMExcellent conductivity, Strong adhesion, UV resistance, antioxidant and antibacterial activity, real-time ECG/EMG sensing[72]