Highly sensitive endotoxin detection using a gold nanoparticle loaded layered molybdenum disulfide-polyacrylic acid nanocomposite

Abstract

Endotoxins or lipopolysaccharides (LPS) are pathogens released from the outer membrane of gram-negative bacteria which produce toxic effects on humans. The sensitive and selective detection of LPS is in high demand, especially in the field of medical supplies, therapeutics and in the food industry. Herein we report a new nano-probe based on a gold nanoparticle loaded, water-soluble layered molybdenum disulfide-polyacrylic acid (Au/MoS₂-PAA) nanocomposite as a label-free voltammetric aptasensor for ultrasensitive LPS detection. MoS₂ nanosheets were obtained through one-step sonication assisted exfoliation of bulk MoS₂ with polyacrylic acid (PAA). Au nanoparticles were incorporated into the MoS₂-PAA nanocomposite and thiol terminated LPS binding aptamers (LBA) were immobilized on this. The specific binding of LPS with LBA is investigated electrochemically by differential pulse voltammetry. The apparent binding constant (K_b) of LPS with LBA has been calculated to be 1.53 × 10² mL g⁻¹. The aptasensor demonstrated LPS detection down to the ag mL⁻¹ level without incorporating any redox mediator and showed wide linearity from 100 ag mL⁻¹ to 100 pg mL⁻¹ with a low limit of detection of 29 ag mL⁻¹. The sensor showed excellent recovery upon spiking LPS in clinical grade insulin, suggesting that LBA/Au/MoS₂-PAA/GCE has promising application for the trace analysis of LPS in the field of pharmaceutical products.