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Ying D, Tseng CY, Chen PW, Lo YH, Hall D. A 30.3 fA/√Hz Biosensing Current Front-End With 139 dB Cross-Scale Dynamic Range. IEEE TRANSACTIONS ON BIOMEDICAL CIRCUITS AND SYSTEMS 2021; 15:1368-1379. [PMID: 34727038 DOI: 10.1109/tbcas.2021.3124197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
This paper presents an 8-channel array of low-noise (30.3 fA/√Hz) current sensing front-ends with on-chip microelectrode electrochemical sensors. The analog front-end (AFE) consists of a 1st-order continuous-time delta-sigma (CT ΔΣ) modulator that achieves 123 fA sensitivity over a 10 Hz bandwidth and 139 dB cross-scale dynamic range with a 2-bit programmable current reference. A digital predictor and tri-level pulse width modulated (PWM) current-steering DAC realize the equivalent performance of a multi-bit ΔΣ in an area- and power-efficient manner. The AFE consumes 50.3 µW and 0.11 mm2 per readout channel. The proposed platform was used to observe protein-ligand interactions in real-time using transient induced molecular electronic spectroscopy (TIMES), a label- and immobilization-free biosensing technique.
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Chen PW, Tseng CY, Shi F, Bi B, Lo YH. Detecting Protein-Ligand Interaction from Integrated Transient Induced Molecular Electronic Signal (i-TIMES). Anal Chem 2020; 92:3852-3859. [PMID: 32045225 DOI: 10.1021/acs.analchem.9b05310] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Quantitative information about protein-ligand interactions is central to drug discovery. To obtain the quintessential reaction dissociation constant, ideally measurements of reactions should be performed without perturbations by molecular labeling or immobilization. The technique of transient induced molecular electrical signal (TIMES) has provided a promising technique to meet such requirements, and its performance in a microfluidic environment further offers the potential for high throughput and reduced consumption of reagents. In this work, we further the development by using integrated TIMES signal (i-TIMES) to greatly enhance the accuracy and reproducibility of the measurement. While the transient response may be of interest, the integrated signal directly measures the total amount of surface charge density resulted from molecules near the surface of electrode. The signals enable quantitative characterization of protein-ligand interactions. We have demonstrated the feasibility of i-TIMES technique using different biomolecules including lysozyme, N,N',N″-triacetylchitotriose (TriNAG), aptamer, p-aminobenzamidine (pABA), bovine pancreatic ribonuclease A (RNaseA), and uridine-3'-phosphate (3'UMP). The results show i-TIMES is a simple and accurate technique that can bring tremendous value to drug discovery and research of intermolecular interactions.
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Affiliation(s)
- Ping-Wei Chen
- Chemical Engineering Program, University of California San Diego, La Jolla, California 92093-0448, United States
| | - Chi-Yang Tseng
- Materials Science and Engineering Program, University of California San Diego, La Jolla, California 92093-0418, United States
| | - Fumin Shi
- InnoScounting LLC, Rockville, Maryland 20850-4432, United States
| | - Bo Bi
- InnoScounting LLC, Rockville, Maryland 20850-4432, United States
| | - Yu-Hwa Lo
- Chemical Engineering Program, University of California San Diego, La Jolla, California 92093-0448, United States.,Materials Science and Engineering Program, University of California San Diego, La Jolla, California 92093-0418, United States.,Electrical and Computer Engineering Department, University of California San Diego, La Jolla, California 92093-0407, United States
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Measuring Electric Charge and Molecular Coverage on Electrode Surface from Transient Induced Molecular Electronic Signal (TIMES). Sci Rep 2019; 9:16279. [PMID: 31700032 PMCID: PMC6838146 DOI: 10.1038/s41598-019-52588-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Accepted: 10/16/2019] [Indexed: 01/05/2023] Open
Abstract
Charge density and molecular coverage on the surface of electrode play major roles in the science and technology of surface chemistry and biochemical sensing. However, there has been no easy and direct method to characterize these quantities. By extending the method of Transient Induced Molecular Electronic Signal (TIMES) which we have used to measure molecular interactions, we are able to quantify the amount of charge in the double layers at the solution/electrode interface for different buffer strengths, buffer types, and pH values. Most uniquely, such capabilities can be applied to study surface coverage of immobilized molecules. As an example, we have measured the surface coverage for thiol-modified single-strand deoxyribonucleic acid (ssDNA) as anchored probe and 6-Mercapto-1-hexanol (MCH) as blocking agent on the platinum surface. Through these experiments, we demonstrate that TIMES offers a simple and accurate method to quantify surface charge and coverage of molecules on a metal surface, as an enabling tool for studies of surface properties and surface functionalization for biochemical sensing and reactions.
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Zhang T, Wei T, Han Y, Ma H, Samieegohar M, Chen PW, Lian I, Lo YH. Protein-Ligand Interaction Detection with a Novel Method of Transient Induced Molecular Electronic Spectroscopy (TIMES): Experimental and Theoretical Studies. ACS CENTRAL SCIENCE 2016; 2:834-842. [PMID: 27924312 PMCID: PMC5126721 DOI: 10.1021/acscentsci.6b00217] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Indexed: 05/08/2023]
Abstract
Protein-ligand interaction detection without disturbances (e.g., surface immobilization, fluorescent labeling, and crystallization) presents a key question in protein chemistry and drug discovery. The emergent technology of transient induced molecular electronic spectroscopy (TIMES), which incorporates a unique design of microfluidic platform and integrated sensing electrodes, is designed to operate in a label-free and immobilization-free manner to provide crucial information for protein-ligand interactions in relevant physiological conditions. Through experiments and theoretical simulations, we demonstrate that the TIMES technique actually detects protein-ligand binding through signals generated by surface electric polarization. The accuracy and sensitivity of experiments were demonstrated by precise measurements of dissociation constant of lysozyme and N-acetyl-d-glucosamine (NAG) ligand and its trimer, NAG3. Computational fluid dynamics (CFD) computation is performed to demonstrate that the surface's electric polarization signal originates from the induced image charges during the transition state of surface mass transport, which is governed by the overall effects of protein concentration, hydraulic forces, and surface fouling due to protein adsorption. Hybrid atomistic molecular dynamics (MD) simulations and free energy computation show that ligand binding affects lysozyme structure and stability, producing different adsorption orientation and surface polarization to give the characteristic TIMES signals. Although the current work is focused on protein-ligand interactions, the TIMES method is a general technique that can be applied to study signals from reactions between many kinds of molecules.
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Affiliation(s)
- Tiantian Zhang
- Materials
Science and Engineering Program, University
of California San Diego, La Jolla, California 92093-0418, United States
| | - Tao Wei
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Yuanyuan Han
- Electrical
and Computer Engineering Department, University
of California San Diego, La Jolla, California 92093-0407, United States
| | - Heng Ma
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Mohammadreza Samieegohar
- Dan
F. Smith Department of Chemical Engineering, Lamar University, Beaumont, Texas 77710, United States
| | - Ping-Wei Chen
- Chemical
Engineering Program, University of California
San Diego, La Jolla, California 92093-0448, United States
| | - Ian Lian
- Biology
Department, Lamar University, Beaumont, Texas 77710, United States
| | - Yu-Hwa Lo
- Materials
Science and Engineering Program, University
of California San Diego, La Jolla, California 92093-0418, United States
- Electrical
and Computer Engineering Department, University
of California San Diego, La Jolla, California 92093-0407, United States
- E-mail:
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