Utilization of Waste Sugarcane Bagasse Towards the Formation of Lignin Nanoparticles and Its Application as a Renewable Carrier for Silver Ions

Abstract Lignin of lignocellulosic biomass holds tremendous potential for producing chemicals and biomaterials. However, unlocking lignin’s utility has been challenging until the advent of lignin nanoparticles (LNPs). LNPs have revolutionized the application of lignin, especially in fields like medicine and pharmaceuticals, by enabling efficient delivery of active bactericidal agents, such as silver ions. Silver ions possess broad-spectrum antibiotic properties against various microbial species. Yet, their clinical and pharmaceutical applications have been limited due to issues like toxicity and inefficient delivery mechanisms. In this study, lignin was extracted from sugarcane bagasse through alkali treatment and acid precipitation. The experimental results indicated that treating the biomass with a 5% NaOH solution followed by precipitation with 6 M H 2 SO 4 yielded the highest lignin content of 23.76%. Characterization of the isolated lignin and synthesized LNPs revealed significant structural and morphological features. FTIR spectra confirmed the presence of characteristic lignin functional groups. DLS analysis showed that the average particle size of LNP@Ag was around 323.7 nm with a polydispersity index (PDI) of 0.17, indicating uniform nanoparticle distribution. SEM imaging revealed irregular morphology of the LNP and rough morphology of LNP@Ag, while EDX confirmed successful silver immobilization in LNP@Ag by detecting a distinct Ag signal. The antimicrobial testing suggested that LNP@Ag exhibited potential antibacterial activity against Escherichia coli and Staphylococcus aureus . Further microtiter calorimetric assay analysis of bactericidal activity against E. coli was performed. Overall, this study underscores the potential of lignin-based nanoparticles, particularly LNP@Ag, as promising candidates for antimicrobial applications, addressing key challenges associated with silver ion delivery and toxicity in clinical and pharmaceutical settings. Graphical abstract