Label-Free Homogeneous Electroanalytical Platform for Pesticide. Detection Based on Acetylcholinesterase-Mediated DNA

Transcription

1 Supporting Information Label-Free Homogeneous Electroanalytical Platform for Pesticide Detection Based on Acetylcholinesterase-Mediated DNA Conformational Switch Integrated with Rolling Circle Amplification Xiaojuan Liu, Mengmeng Song, Ting Hou, and Feng Li* College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao , People s Republic of China * Corresponding author. Tel/Fax: lifeng@qust.edu.cn Table of Contents: 1. Experimental Section Reagents; Apparatus; Effect of Pesticide on Enzyme Activity; Effect of Hg 2+ on Enzyme Activity; Versatility Study 2. Supplementary Figures and Tables Figure S-1 ~ Figure S-5; Table S-2 ~ Table S-3 3. Supplemental References S-1

2 1. Experimental Section Reagents. Tris(hydroxymethyl)aminomethane (Tris), MB, hydrochloric acid (HCl), (NH 4 ) 2 SO 4, KCl, and MgCl 2 were obtained from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China). ATP, T4 DNA ligase, and phi29 DNA polymerase were purchased from New England BioLabs, Inc.. AChE (220 U/g), acetylthiocholine chloride (ATCh), SYBR Green I, and omethoate were purchased from Sigma-Aldrich (St. Louis, MO, USA). All the chemicals are of analytical grade and used without further purification. Ultrapure water (resistivity 18.2 MΩ cm) was used during the experiments. All DNA probes were synthesized and HPLC-purified by Sangon Biotechnology Co., Ltd. (Shanghai, China), and their sequences were shown in Table S1. Table S-1. Sequences of DNA probes used in this work. a Name Sequence (5 3 ) HP with 2 T-T mismatch CGT TCA GCA GTG TTC G phosphate-gct GAA CGA AAT CCC TCC CTC CCT CCC Padlock probe 1 ATT TTT TTA TCC CTC CCT CCC TCC CAA ACG AAC ACT HP with 3 T-T mismatch CGT TTC AGC AGT GTT TCG phosphate- GCT GAA ACG AAA TCC CTC CCT CCC TCCC Padlock probe 2 ATT TTT TTA TCC CTC CCT CCC TCCC AAA CG AAA CAC T HP with 4 T-T mismatch CGT TTT CAG CAG TGT TTT CG phosphate- GCT GAA AAC GAA ATC CCT CCC TCC CTC Padlock probe 3 CCA TTT TTT TAT CCC TCC CTC CCT CCC AAA CGA AAA CAC T HP with 5 T-T mismatch CGT TTC TTG CAG TTG TTT CG S-2

3 phosphate-gca AGA AAC GAA ATC CCT CCC TCC CTC Padlock probe 4 CCA TTT TTT TAT CCC TCC CTC CCT CCC AAA CGA AAC AAC T HP S1 CGT TTC AGC AGT GAG CCG phosphate- GCT GAA ACG AAA TCC CTC CCT CCC TCCC Padlock probe S1 ATT TTT TTA TCC CTC CCT CCC TCCC AAA CG GCT CAC T a The underlined letters represent the T-T mismatch bases, which can form T-Hg 2+ -T structures. The letters in italic are the sequences complementary to that of G-quadruplex. Apparatus. Electrochemical measurements were performed on an Autolab Electrochemical Workstation (Metrohm, Switzerland) with a conventional three-electrode system, in which an ITO electrode was employed as the working electrode, a platinum wire was used as the auxiliary electrode, and a standard Ag/AgCl was used as the reference electrode. The ITO electrode was pretreated and cleaned by the previously reported procedures 1 to obtain a negatively charged electrode. Differential pulse voltammetric (DPV) measurement was performed in 50 μl of reaction solution, with the potential sweeping from 0.6 V to 0.1 V, the width, height, period, and increment of pulse were set to 0.05 V, 0.05 s, 0.5 s, and V, respectively. Effect of Pesticide on Enzyme Activity. To investigate the effect of pesticide on enzyme activity, omethoate with different concentrations were incubated with T4 DNA ligase and phi 29 DNA polymerase for 3 h, respectively. Then, the as-treated T4 DNA ligase and phi 29 DNA polymerase were used for the following ligation reaction and RCA reaction via the aforementioned procedure, except that single-stranded HP without incorporation of Hg 2+ was used in the ligation reaction. S-3

4 Effect of Hg 2+ on Enzyme Activity. The influence of Hg 2+ on enzyme activity was tested by substituting HP and padlock probe 2 with HP S1 and Padlock probe S1, respectively. HP S1 had random sequences without T-T mismatch that could not incorporate with Hg 2+. The possible inhibition effects of Hg 2+ on T4 DNA ligase and phi 29 DNA polymerase were investigated by using Hg 2+ incubated enzymes for the following ligation reaction and RCA reaction, respectively. Versatility Study. The versatility of the as-proposed method for the detection of other pesticides were carried out by substituting omethoate with other conventional organophosphate and carbamate pesticides (10000 g/l), namely aldicarb, dibrom, diazinon, dursban, glyphosate, methomyl, carbaryl, and the mixture of omethoate (5000 g/l) and carbaryl (5000 g/l), respectively. S-4

5 2. Supplementary Figures and Tables Figure S-1. DPV peak current changes between MB in buffer and in the reaction system with T4 and phi 29 incubated with different concentrations of omethoate, in which the MB concentrations were kept the same at 5 μm. The error bars represent the standard deviation of three repetitive measurements. S-5

6 Figure S-2. DPV peak current changes between MB in buffer and in the reaction system with T4 and phi 29 incubated with different concentrations of Hg 2+. The error bars represent the standard deviation of three repetitive measurements. S-6

7 Figure S-3. The DPV peak current change ( i p = i p(omethoate) - i p(blank) ) of the system with different MB concentrations: 1, 3, 5, 7, and 9 μm. The error bars represent the standard deviation of three repetitive measurements. S-7

8 Figure S-4. The DPV peak current recorded under different intercalation time for MB molecules (ranging from 0 to 21 min). The error bars represent the standard deviation of three repetitive measurements. S-8

9 Figure S-5. DPV peak currents of the sensing system in the absence (blank), and presence of different pesticides: omethoate, aldicarb, dibrom, diazinon, dursban, glyphosate, carbaryl, methomyl with the same concentration (10,000 μg/l), and the mixture of omethoate (5000 μg/l) and carbaryl (5000 μg/l), respectively. S-9

10 Table S-2. Comparison of the pesticide detection performance of the present method and those previously reported methods. Detection Strategy Immobilization of AChE on the quartz crystal Detection methods Quartz crystal microbalance Pesticide LOD Ref. Carbaryl 20.1 μg/l 2 Tetrathiafulvalene tetracyanoquinodimethane /ionic liquid conductive gels AChE and choline oxidase coupled with nanoceria-coated paper AChE immobilized on a carbon screen printed electrode Immobilization of AChE onto SAM gold electrode Amperometry Neostigmine 57 μg/l 3 Colorimetry Methyl-paraoxon 18 μg/l 4 Amperometry Paraoxon 2.5 μg/l 5 Amperometry Parathion 9.3 μg/l 6 AChE-based AutoDip biosensor Amperometry Chlorpyrifos-oxon 35 μg/l 7 AChE entrapped in a polyvinylalcohol based matrix AChE-catalyzing coupled with nicking enzyme-assisted cycling amplification Immobilization of AChE on nanoparticle modified glass carbon electrode Amperometry Chlorfenvinphos 46.7 μg/l 8 Fluoremetry Aldicarb 3.3 μg/l 9 Amperometry Aldicarb 8.5 mg/l 10 DNA probe modified gold electrode DPV Aldicarb 10 μg/l 11 Label-free homogeneous electrochemical biosensor DPV omethoate 2.1 μg/l Present work S-10

11 Table S-3. Determination of omethoate spiked in real food samples. Food samples No. Omethoate added (μg/l) Omethoate detected (μg/l) Recovery (%) a Standards for recovery (%) b Peach Carrot a Recovery (%) = (Cdetected / C added ) 100% b Chinese National Standards (GB/T ) S-11

12 3. Supplemental References (1) Liu, X. J.; Li, W.; Hou, T.; Dong, S. S.; Yu, G. H.; Li, F. Homogeneous Electrochemical Strategy for Human Telomerase Activity Assay at Single-Cell Level Based on T7 Exonuclease-Aided Target Recycling Amplification. Anal. Chem. 2015, 87, (2) Abad, M. J.; Pariente, F.; Hernandez, L.; Abrun, D. H.; Lorenzo, E. Determination of Organophosphorus and Carbamate Pesticides Using a Piezoelectric Biosensor. Anal. Chem. 1998, 70, (3) Zamfir, L. G.; Rotariu, L.; Bala, C. Acetylcholinesterase Biosensor for Carbamate Drugs Based on Tetrathiafulvalene Tetracyanoquinodimethane/Ionic Liquid Conductive Gels. Biosens. Bioelectron. 2013, 46, (4) Nouanthavong, S.; Nacapricha, D.; Henry, C. S.; Sameenoi, Y. Pesticide Analysis Using Nanoceria-Coated Paper-Based Devices as a Detection Platform. Analyst 2016, 141, (5) Pohanka, M.; Jun, D.; Kuca, K. Amperometric Biosensors for Real Time Assays of Organophosphates. Sensors 2008, 8, (6) Pedrosa, V. A.; Caetona, J.; Sergio, A. S.; Machodo, S. A. S.; Freire, R. S.; Bertotti, M. Acetylcholinesterase Immobilization on 3-Mercaptopropionic Acid Self-Assembled Monolayer for Determination of Pesticides. Electroanalysis 2007, 19, (7) Drechsel, L.; Schulz, M.; Stetten, F.; Moldovan, C.; Zengerle, R.; Paust, N. Electrochemical Pesticide Detection with Auto Dip A Portable Platform for Automation of Crude Sample Analyses. Lab Chip 2015, 15, (8) Istamboulie, G.; Andreescu, S.; Marty, J. L.; Noguer, T. Highly Sensitive Detection of Organophosphorus Insecticides Using Magnetic Microbeads and Genetically Engineered S-12

13 Acetylcholinesterase. Biosens. Bioelectron. 2007, 23, (9) Wang, X. Z.; Hou, T.; Dong, S. S.; Liu, X. J.; Li, F. Fluorescence Biosensing Strategy Based on Mercury Ion-Mediated DNA Conformational Switch and Nicking Enzyme-Assisted Cycling Amplification for Highly Sensitive Detection of Carbamate Pesticide. Biosens. Bioelectron. 2016, 77, (10) Upadhyay, S.; Rao, R. G.; Sharma, K. M.; Bhattacharya, K. B.; Rao, K. V.; Vijayaraghavan, R. Immobilization of Acetylcholineesterase Choline Oxidase on a Gold Platinum Bimetallic Nanoparticles Modified Glassy Carbon Electrode for the Sensitive Detection of Organophosphate Pesticides, Carbamates and Nerve Agents. Biosens. Bioelectron. 2009, 25, (11) Yang, Y. M.; Liu, X. J.; Wu, M.; Wang, X. Z.; Hou, T.; Li, F. Electrochemical Biosensing Strategy for Highly Sensitive Pesticide Assay Based on Mercury Ion-Mediated DNA Conformational Switch Coupled with Signal Amplification by Hybridization Chain Reaction. Sens. Actuators B: Chem. 2016, 236, S-13