Self-assembled lignin nanoparticles produced from elephant grass leaves enable selective inactivation of Gram-positive microorganisms
In this study, we added value to lignocellulosic biomass-derived lignin by converting it into antimicrobial nanoparticles using a simple self-assembling method in solution. Transmission electron microscopy (TEM) and zeta potential analyses showed that the self-assembled lignin nanoparticles (SA-LNPs...
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Published in | RSC sustainability Vol. 2; no. 2; pp. 459 - 474 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
07.02.2024
|
Online Access | Get full text |
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Summary: | In this study, we added value to lignocellulosic biomass-derived lignin by converting it into antimicrobial nanoparticles using a simple self-assembling method in solution. Transmission electron microscopy (TEM) and zeta potential analyses showed that the self-assembled lignin nanoparticles (SA-LNPs) had a spherical-like morphology, 80 nm average size, and a surface charge of −29 ± 4 mV. Previous studies have shown that LNPs are toxic to bacteria, though the potential mechanisms of action leading to antimicrobial properties of LNPs are lacking in the literature. Therefore, we conducted a thorough investigation of the antibacterial activity of SA-LNPs using four bacteria strains:
Escherichia coli
and
Pseudomonas aeruginosa
(Gram-negative) and
Bacillus subtilis
and
Lactobacillus fermentum
(Gram-positive). The antimicrobial assays performed in saline media revealed that SA-LNPs were selectively toxic to Gram-positive bacteria, and no significant antimicrobial effects were found against the Gram-negative strains. Time-kill experiments showed that 25 μg mL
−1
SA-LNPs were able to inactivate more than 90% of the Gram-positive bacteria after 30 min exposure. We conducted
in vitro
and
in vivo
assays to evaluate the production of reactive oxidative species (ROS), such as glutathione and 2′,7′-dichlorodihydrofluorescein diacetate (H
2
DCFA). These assays indicated that oxidative stress was not the underlying mechanism involved in the antimicrobial activity of SA-LNPs. This finding corroborates that SA-LNPs could scavenge radicals of 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazin-1-yl (DPPH), confirming their strong antioxidant property. Although direct oxidative stress was ruled out as the probable mechanism of action, we still cannot dismiss an indirect pro-oxidant effect resulting from the SA-LNPs-containing adsorbed ROS coming into direct contact with the cell wall.
Plant-derived lignin nanoparticles produced through a self-assembly method show selective toxicity against Gram-positive bacteria. |
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Bibliography: | https://doi.org/10.1039/d3su00400g cells exposed to SA-LNPs. See DOI Electronic supplementary information (ESI) available: Zeta potential and number-weighted average hydrodynamic diameters of SA-LNPs dispersed in water and saline solution; ATR-FTIR spectra of dried bulk alkaline lignin and SA-LNPs; DPPH radical scavenging activity measured for bulk alkaline lignin dissolved; SEM image of L. fermentum |
ISSN: | 2753-8125 2753-8125 |
DOI: | 10.1039/d3su00400g |