Peptide-assembled graphene oxide as fluorescent turn–on sensor for ultrasensitive Lipopolysaccharide (Endotoxin) detection

Lipopolysaccharide (LPS), or endotoxin, a major component in the outer cell membrane of Gram-negative bacteria is a very\udpowerful and toxic inflammatory stimulator, resulting in sepsis or septic shock, a significant medical problem affecting about 700 000 patients and\udcausing 250 000 casualties annually in the United States itself. The detection of LPS is highly importance. However, the currently used enzymatic\udlimulus amebocyte lysate assay is highly susceptible to changes in temperature and pH, interference factors, and requires cumbersome sample\udpreparation. A more cost-effective, sensitive and robust detection method is needed.\udObjective: To design and develop biosensor for LPS detection by assembling a LPS-binding peptide (as LPS receptor) with graphene oxide (GO, as\udfluorescence quencher).\udMethods: GO was synthesized using a modified Hummer’s method. A synthetic LPS-binding peptide was designed, fluorescent labelled, and\udassembled with GO in PBS buffer solution. The fluorescence recovery of the peptide-GO was measured upon addition of LPS from Gram negative\udbacteria: E. coli, K. pneumoniae, Samonella Thyphosa, P. aeruginosa, as well as living pathogenic bacteria. Specificity tests were conducted with\udvarious biological molecules to evaluate the sensing performance.\udResults & Discussion: Specific binding of LPS with peptide release the peptides from GO, resulting in fluorescence recovery, allowing\udultrasensitive detection of LPS with the limit of detection of 130 pM, the most sensitive synthetic LPS sensors to-date. The LPS sensor is highly\udselective to LPS than other biological species.\udConclusion: We developed a peptide-GO assembled fluorescence sensor for ultrasensitive and specific LPS/endotoxin detection. This is the most\udsensitive synthetic LPS sensor reported in the world