title: Reporter-encapsulated liposomes on graphene field effect transistors for signal enhanced detection of physiological enzymes.
abstract: A novel approach for enzymatic assay using reporter-encapsulated liposomes on graphene field effect transistors (FET) is proposed. This approach involves real time monitoring of drain current (Id) of reduced graphene oxide (rGO) upon rupture of reporter-encapsulated 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) liposomes triggered by enzymes. For validation of the proposed approach, 2,4,6-trinitrophenol (TNP) is used as the reporter for specific detection of phospholipase A2 (PLA2), a key enzyme in various membrane related physiological processes. Experimental results revealed that Id increased with PLA2 concentration, which is attributed to the interaction between released TNP and rGO. The limit of detection (LOD) achieved by the proposed approach was 80 pM, which is superior to most assays reported previously and much lower than the cut-off level of circulating secretory PLA2 (2.07 nM). Besides the high accuracy of the electronic detection methodology, the signal enhancement effect realized by the excess concentration of TNP (approximately 1 mM) in liposomes is believed to be the main reason for the significantly enhanced sensitivity of the proposed assay, indicating great potential for further improvement in the sensitivity by increasing the concentration of TNP. In addition, the proposed approach is rapid (incubation time ≤ 10 min) and label-free, thus showing great potential for practical applications in the future.
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798. MIYTOK@ntu.edu.sg.
authors.forename: Hu
authors.initials: H
authors.lastname: Chen
authors.forename: Seng Koon
authors.initials: SK
authors.lastname: Lim
authors.forename: Peng
authors.initials: P
authors.lastname: Chen
authors.forename: Jingfeng
authors.initials: J
authors.lastname: Huang
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.forename: Alagappan
authors.initials: A
authors.lastname: Palaniappan
authors.forename: Mark
authors.initials: M
authors.lastname: Platt
authors.forename: Bo
authors.initials: B
authors.lastname: Liedberg
authors.forename: Alfred Iing Yoong
authors.initials: AI
authors.lastname: Tok
mesh_terms: D006108:Graphite / Q000737:chemistry*; D007700:Kinetics; D008081:Liposomes / Q000737:chemistry* / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D010087:Oxides / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D054467:Phospholipases A2 / Q000032:analysis*; D010851:Picrates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013053:Spectrophotometry; D013379:Substrate Specificity; D014173:Transistors, Electronic
chemical_list: D008081:Liposomes; D010087:Oxides; D010713:Phosphatidylcholines; D010851:Picrates; D012822:Silicon Dioxide; D006108:Graphite; C005858:picric acid; D054467:Phospholipases A2; C028694:1-palmitoyl-2-oleoylphosphatidylcholine