From:  Functional lignin hydrogels for biosensors and biomedical therapy

 The various types of stimuli responsive lignin-based hydrogels and their applications.

MaterialStimuli response typeAgentProperties ApplicationReferences
Lignosulfonate-NIPAM-IA hydrogelsTemperature sensitive + pH sensitive (dual stimuli response)N-isopropylacrylamide (NIPAM) for and itaconic acid (IA) as temperature and pH sensitive components, respectivelyThe temperature-sensitive behaviours of LNIH-3.7%, LNIH-5.7%, and LNIH-6.9% hydrogels have been observed at around 35°C, which is relatively close to the physiological temperature of 37°C. Each LNIH hydrogel demonstrated pH sensitivity ranging from 3.0 to 9.1Controlled release of drugs or pesticide[148]
Ag-SLS/PPy-PDA@PEGDA hydrogelPhotothermal responseUnder near-infrared irradiation (808 nm), the temperature of the hydrogel system increased up to 52.9°C within 3 min, validating high photothermal effect. Also demonstrated excellent antibacterial activity against Staphylococcus aureus and Escherichia coliTherapeutic dressing for infected wound healing, tissue engineering[149]
LigHyd-RB@L AgNCs (lignin hydrogel doped RB-conjugated lignin-Ag nanocomposites)Photodynamic + pH responsive release (dual stimuli response)Rose BengalThe survival rate of Candida tropicalis colonies declined to about 14%. In the presence of green laser (525 nm, 2.5 mW for 3 min), the IC50 value of LigHyd-RB@L AgNCs decreased by ~2 fold when compared to dark circumstancesWound dressing, drug delivery of antimicrobial PDT[150]
LPC-MWCNT (lignin–chitosan/multiwalled carbon nanotube) hydrogelsPhotothermalCarbon nanotubesThe LPC-MWCNTs1.5 hydrogel reached about 57°C after being exposed to an 808 nm NIR laser (1.5 W/cm2, 5 min), which successfully killed 99% Escherichia coli and 97.8% Staphylococcus aureus by thermal denaturationAntibacterial wound dressing[151]