G-Quadruplex Based Impedimetric 2-Hydroxyfluorene Biosensor Using Hemin As a Peroxidase

Electronic Supplementary Material

G-quadruplex based impedimetric 2-hydroxyfluorene biosensor using hemin as a peroxidase enzyme mimic

Gang Lianga,b, Xinhui Liua*

aState Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, P. R. China

bState Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, P. R. China

*Corresponding Authors: (X. H. Liu), Tel: +86-01-58802996, Fax: +86-01-58802996

Materials and Methods

Differential Pulse Voltammetry Measurements

Electrochemical experiment for Differential Pulse Voltammetry(DPV) wascarried outon a CHI 650D electrochemical workstation (Shanghai Chenhua instrument Co. Ltd., China). A conventional three-electrode system was used. The DNAmodified gold electrode was employed as the working electrode, a saturated Ag/AgCl reference electrode and a platinum wire auxiliary electrode were separately used for the measurements. The test Tris-ClO4 buffer solution (20 mM, pH=7.4) was firstly bubbled thoroughly with high purity nitrogen for 5 min. DPV was recorded in the scan range from 100 to -600mV using pulse amplitude 100 mV and scan step 5 mV. All experiments were performed atroomtemperature.

Results and Discussion

Fig. S1. pH effects on the DNAzyme activity to the ABTS-H2O2 system in Tris-HClO4 buffer solution (20 mM). Error bars were derived from three measurements. (DNA: 0.1 μM; hemin: 0.1 μM; ABTS: 2 mM; H2O2: 2.5 mM; K+: 10 mM).

Table S1．Comparison of reported methods for determination of 2-Hydroxyfluorene

Methods / Detection limit (nM) / linear range
(nM) / Disadvantages / Advantages / Reference
HPLC-Column-switching and Fluorescence detection / 0.03a / 0.5-41.6 / expensive instruments, tedious pre-treatment of sample (involved enzymatic hydrolysis, solid/liquid phase extraction etc.), and highly qualified technicians / high sensitivity andselectivity, simultaneous analysis of several compounds / 1
LC-MS / 0.57a / -- / 2
0.55a / -- / 3
GC-MS / 0.025a / -- / 4
LC-MS-MS / 0.5 / -- / 5
This method / 1.2b / 10-104 / requiring specific DNA aptamer / easy operation,
low cost,
high sensitivity / This work
3.6c

a Method detection limit; b detection limit in buffer; c detection limit in lake water.

References

[1] Toriba A, Chetiyanukornkul T, Kizu R, Hayakawa K (2003) Quantification of 2-hydroxyfluorene in human urine by column-switching high performance liquid chromatography with fluorescence detection, Analyst 128: 605

[2] Kamiya M, Toriba A, Onoda Y, Kizu R, Hayakawa K (2005) Evaluation of estrogenic activities of hydroxylated polycyclic aromatic hydrocarbons in cigarette smoke condensate, Food Chem Toxicol 43: 1017

[3] Campo L, Rossella F, Fustinoni S, (2008) Development of a gas chromatography/mass spectrometry method to quantify several urinary monohydroxy metabolites of polycyclic aromatic hydrocarbons in occupationally exposed subjects, J Chromatogr B, 875: 531

[4] Li Z, Romanoff LC, Trinidad DA, Hussain N, Jones RS, Porter EN, Patterson DG, Sjödin A (2006) Measurement of urinary monohydroxy polycyclic aromatic hydrocarbons using automated liquid−Liquid extraction and gas chromatography/isotope dilution high-resolution mass spectrometry, Anal Chem, 78: 5744

[5] Jacob P, Wilson M, Benowitz NL (2007) Determination of phenolic metabolites of polycyclic aromatic hydrocarbons in human urine as their pentafluorobenzyl ether derivatives using liquid chromatography−tandem mass spectrometry, Anal Chem 79: 587