1
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Dai L, Johnson-Buck A, Laird PW, Tewari M, Walter NG. Ultrasensitive amplification-free quantification of a methyl CpG-rich cancer biomarker by single-molecule kinetic fingerprinting. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.06.587997. [PMID: 38645159 PMCID: PMC11030368 DOI: 10.1101/2024.04.06.587997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
The most well-studied epigenetic marker in humans is the 5-methyl modification of cytosine in DNA, which has great potential as a disease biomarker in liquid biopsies of cell-free DNA. Currently, quantification of DNA methylation relies heavily on bisulfite conversion followed by PCR amplification and NGS or microarray analysis. PCR is subject to potential bias in differential amplification of bisulfite-converted methylated versus unmethylated sequences. Here, we combine bisulfite conversion with single-molecule kinetic fingerprinting to develop an amplification-free assay for DNA methylation at the branched-chain amino acid transaminase 1 (BCAT1) promoter. Our assay selectively responds to methylated sequences with a limit of detection below 1 fM and a specificity of 99.9999%. Evaluating complex genomic DNA matrices, we reliably distinguish 2-5% DNA methylation at the BCAT1 promoter in whole blood DNA from completely unmethylated whole-genome amplified DNA. Taken together, these results demonstrate the feasibility and sensitivity of our amplification-free, single-molecule quantification approach to improve the early detection of methylated cancer DNA biomarkers.
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Affiliation(s)
- Liuhan Dai
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Peter W. Laird
- Department of Epigenetics, Van Andel Institute, Grand Rapids, MI, 49503, USA
| | - Muneesh Tewari
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI 48109, USA
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nils G. Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI 48109, USA
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2
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Li Q, Qiang W, Yuan J, Xiao L. Nanoparticle-Coupled Single-Molecule Kinetic Fingerprinting for Enzymatic Activity Detection. Anal Chem 2023; 95:7796-7803. [PMID: 37129996 DOI: 10.1021/acs.analchem.3c01385] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The sensitive and accurate detection of biomarkers plays an important role in clinical diagnosis and drug discovery. Currently, amplification-based methods for biomarker detection are widely explored. However, the key challenges of these methods are limited reproducibility and high background noise. To overcome these limitations, we develop a robust plasmonic nanoparticle-coupled single-molecule kinetic fingerprinting (PNP-SMKF) method to achieve ultrasensitive detection of protein kinase A (PKA). Transient binding of a short fluorescent probe with the genuine target produces a distinct kinetic signature that is completely different from that of the background signal, allowing us to recognize PKA sensitively. Importantly, integrating a plasmonic nanoparticle efficiently breaks the concentration limit of the imager strand for single-molecule imaging, thus achieving a much faster imaging speed. A limit of detection (LOD) of as low as 0.0005 U/mL is readily realized. This method holds great potential as a versatile platform for enzyme detection and inhibitor screening in the future.
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Affiliation(s)
- Qingnan Li
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
- College of Chemistry, Nankai University, Tianjin 300071, China
| | - Wenzhi Qiang
- College of Chemistry, Nankai University, Tianjin 300071, China
| | - Jie Yuan
- School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453007, China
| | - Lehui Xiao
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, China
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3
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Chatterjee T, Johnson-Buck A, Walter NG. Highly sensitive protein detection by aptamer-based single-molecule kinetic fingerprinting. Biosens Bioelectron 2022; 216:114639. [PMID: 36037714 DOI: 10.1016/j.bios.2022.114639] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 07/21/2022] [Accepted: 08/13/2022] [Indexed: 11/28/2022]
Abstract
Sensitive assays of protein biomarkers play critical roles in clinical diagnostics and biomedical research. Such assays typically employ immunoreagents such as monoclonal antibodies that suffer from several drawbacks, including relatively tedious production, significant batch-to-batch variability, and challenges in site-specific, stoichiometric modification with fluorophores or other labels. One proposed alternative to such immunoreagents, nucleic acid aptamers generated by systematic evolution of ligand by exponential enrichment (SELEX), can be chemically synthesized with much greater ease, precision, and reproducibility than antibodies. However, most aptamers exhibit relatively poor affinity, yielding low sensitivity in the assays employing them. Recently, single molecule recognition through equilibrium Poisson sampling (SiMREPS) has emerged as a platform for detecting proteins and other biomarkers with high sensitivity without requiring high-affinity detection probes. In this manuscript, we demonstrate the applicability and advantages of aptamers as detection probes in SiMREPS as applied to two clinically relevant biomarkers, VEGF165 and IL-8, using a wash-free protocol with limits of detection in the low femtomolar range (3-9 fM). We show that the kinetics of existing RNA aptamers can be rationally optimized for use as SiMREPS detection probes by mutating a single nucleotide in the conserved binding region or by shortening the aptamer sequence. Finally, we demonstrate the detection of endogenous IL-8 from human serum at a concentration below the detection limit of commercial ELISAs.
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Affiliation(s)
- Tanmay Chatterjee
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, 48109, United States
| | - Alexander Johnson-Buck
- aLight Sciences, Inc., 333 Jackson Plaza Suite 460, Ann Arbor, Michigan, 48103, United States.
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan, 48109, United States.
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4
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Abstract
One of the key advantages of single-molecule sensors over conventional ensemble technologies is their capability of revealing the heterogeneity among molecular events. In dynamic single-molecule sensing, heterogeneity in molecular interaction kinetics is quantified as the fingerprint to specifically detect target molecules. This strategy offers a unique approach to develop ultrasensitive biosensors with a limit of detection at the fM level, which is three orders of magnitude lower than that of conventional assays. However, due to the lack of a comprehensive theoretical model, the rational design of dynamic single-molecule sensors is challenging. Herein, we present the theoretical study of sensing performance with a hydrodynamic model. We quantitatively show that there is a dilemma regarding the probe design. High-affinity probes offer higher specificity but require extremely long assay time, while low-affinity probes could shorten the assay time but are prone to the interference from unwanted molecules. This study also suggests that one possible solution to solve this dilemma is by applying external disturbance to the system, as we have recently demonstrated by experiments. We anticipate that this work could inspire the rational design of single-molecule sensors to further improve the sensitivity, specificity, and multiplexing capability.
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Affiliation(s)
- Yuting Yang
- Department of Instrument Science and Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China
| | - Qiang Zeng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China
| | - Qingqing Luo
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China
| | - Chen Wang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China
| | - Hui Yu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai 200030, People's Republic of China
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5
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Li Z, McNeely M, Sandford E, Tewari M, Johnson-Buck A, Walter NG. Attomolar Sensitivity in Single Biomarker Counting upon Aqueous Two-Phase Surface Enrichment. ACS Sens 2022; 7:1419-1430. [PMID: 35438959 DOI: 10.1021/acssensors.2c00135] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
From longstanding techniques like enzyme-linked immunosorbent assay (ELISA) to modern next-generation sequencing, many of the most sensitive and specific biomarker detection assays require capture of the analyte at a surface. While surface-based assays provide advantages, including the ability to reduce background by washing away excess reagents and/or increase specificity through analyte-specific capture probes, the limited efficiency of capture from dilute solution often restricts assay sensitivity to the femtomolar-to-nanomolar range. Although assays for many nucleic acid analytes can decrease limits of detection (LODs) to the subfemtomolar range using polymerase chain reaction, such amplification may introduce biases, errors, and an increased risk of sample cross-contamination. Furthermore, many analytes cannot be amplified easily, including short nucleic acid fragments, epigenetic modifications, and proteins. To address the challenge of achieving subfemtomolar LODs in surface-based assays without amplification, we exploit an aqueous two-phase system (ATPS) to concentrate target molecules in a smaller-volume phase near the assay surface, thus increasing capture efficiency compared to passive diffusion from the original solution. We demonstrate the utility of ATPS-enhanced capture via single molecule recognition through equilibrium Poisson sampling (SiMREPS), a microscopy technique previously shown to possess >99.9999% detection specificity for DNA mutations but an LOD of only ∼1-5 fM. By combining ATPS-enhanced capture with a Förster resonance energy transfer (FRET)-based probe design for rapid data acquisition over many fields of view, we improve the LOD ∼ 300-fold to <10 aM for an EGFR exon 19 deletion mutation. We further validate this ATPS-assisted FRET-SiMREPS assay by detecting endogenous exon 19 deletion molecules in cancer patient blood plasma.
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Affiliation(s)
- Zi Li
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Molly McNeely
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Erin Sandford
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Muneesh Tewari
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nils G. Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
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6
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A guide to accelerated direct digital counting of single nucleic acid molecules by FRET-based intramolecular kinetic fingerprinting. Methods 2022; 197:63-73. [PMID: 34182140 PMCID: PMC8709879 DOI: 10.1016/j.ymeth.2021.06.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Revised: 06/21/2021] [Accepted: 06/23/2021] [Indexed: 01/03/2023] Open
Abstract
Cell-free nucleic acids (cfNAs) such as short non-coding microRNA (miRNA) and circulating tumor DNA (ctDNA) that reside in bodily fluids have emerged as potential cancer biomarkers. Methods for the rapid, highly specific, and sensitive monitoring of cfNAs in biofluids have, therefore, become increasingly attractive as clinical diagnosis tools. As a next generation technology, we provide a practical guide for an amplification-free, single molecule Förster resonance energy transfer (smFRET)-based kinetic fingerprinting approach termed intramolecular single molecule recognition through equilibrium Poisson sampling, or iSiMREPS, for the rapid detection and counting of miRNA and mutant ctDNA with virtually unlimited specificity and single molecule sensitivity. iSiMREPS utilizes a pair of fluorescent detection probes, wherein one probe immobilizes the target molecules on the surface, and the other probe transiently and reversibly binds to the target to generate characteristic time-resolved fingerprints as smFRET signal that are detected in a total internal reflection fluorescence microscope. Analysis of these kinetic fingerprints enables near-perfect discrimination between specific binding to target molecules and nonspecific background binding. By accelerating kinetic fingerprinting using the denaturant formamide and reducing background signals by removing target-less probes from the surface via toehold-mediated strand displacement, iSiMREPS has been demonstrated to count miR-141 and EGFR exon 19 deletion ctDNA molecules with a limit of detection (LOD) of ~1 and 3 fM, respectively, as well as mutant allele fractions as low as 0.0001%, during a standard acquisition time of only ~10 s per field of view. In this review, we provide a detailed roadmap for implementing iSiMREPS more broadly in research and clinical diagnostics, combining rapid analysis, high specificity, and high sensitivity.
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7
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Stein J, Stehr F, Jungmann R, Schwille P. Calibration-free counting of low molecular copy numbers in single DNA-PAINT localization clusters. BIOPHYSICAL REPORTS 2021; 1:100032. [PMID: 36425461 PMCID: PMC9680712 DOI: 10.1016/j.bpr.2021.100032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/04/2021] [Indexed: 06/16/2023]
Abstract
Single-molecule localization microscopy (SMLM) has revolutionized light microscopy by enabling optical resolution down to a few nanometer. Yet, localization precision commonly does not suffice to visually resolve single subunits in molecular assemblies or multimeric complexes. Because each targeted molecule contributes localizations during image acquisition, molecular counting approaches to reveal the target copy numbers within localization clusters have been persistently proposed since the early days of SMLM, most of which rely on preliminary knowledge of the dye photophysics or on a calibration to a reference. Previously, we developed localization-based fluorescence correlation spectroscopy (lbFCS) as an absolute ensemble counting approach for the SMLM-variant DNA-PAINT (points accumulation for imaging in nanoscale topography), for the first time, to our knowledge, circumventing the necessity for reference calibrations. Here, we present an extended concept termed lbFCS+, which allows absolute counting of copy numbers for individual localization clusters in a single DNA-PAINT image. In lbFCS+, absolute counting of fluorescent loci contained in individual nanoscopic volumes is achieved via precise measurement of the local hybridization rates of the fluorescently labeled oligonucleotides ("imagers") employed in DNA-PAINT imaging. In proof-of-principle experiments on DNA origami nanostructures, we demonstrate the ability of lbFCS+ to truthfully determine molecular copy numbers and imager association and dissociation rates in well-separated localization clusters containing up to 10 docking strands. For N ≤ 4 target molecules, lbFCS+ is even able to resolve integers, providing the potential to study the composition of up to tetrameric molecular complexes. Furthermore, we show that lbFCS+ allows resolving heterogeneous binding dynamics, enabling the distinction of stochastically generated and a priori indistinguishable DNA assemblies. Beyond advancing quantitative DNA-PAINT imaging, we believe that lbFCS+ could find promising applications ranging from biosensing to DNA computing.
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Affiliation(s)
- Johannes Stein
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Florian Stehr
- Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Ralf Jungmann
- Max Planck Institute of Biochemistry, Martinsried, Germany
- Faculty of Physics, Ludwig Maximilian University, Munich, Germany
| | - Petra Schwille
- Max Planck Institute of Biochemistry, Martinsried, Germany
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8
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Khanna K, Mandal S, Blanchard AT, Tewari M, Johnson-Buck A, Walter NG. Rapid kinetic fingerprinting of single nucleic acid molecules by a FRET-based dynamic nanosensor. Biosens Bioelectron 2021; 190:113433. [PMID: 34171818 PMCID: PMC8295208 DOI: 10.1016/j.bios.2021.113433] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2021] [Revised: 06/08/2021] [Accepted: 06/10/2021] [Indexed: 01/05/2023]
Abstract
Biofluid-derived cell-free nucleic acids such as microRNAs (miRNAs) and circulating tumor-derived DNAs (ctDNAs) have emerged as promising disease biomarkers. Conventional detection of these biomarkers by digital PCR and next generation sequencing, although highly sensitive, requires time-consuming extraction and amplification steps that also increase the risk of sample loss and cross-contamination. To achieve the direct, rapid, and amplification-free detection of miRNAs and ctDNAs with near-perfect specificity and single-molecule level sensitivity, we herein designed a single-molecule kinetic fingerprinting assay, termed intramolecular single-molecule recognition through equilibrium Poisson sampling (iSiMREPS). iSiMREPS exploits a dynamic DNA nanosensor comprising a surface anchor and a pair of fluorescent detection probes: one probe captures a target molecule onto the surface, while the other transiently interrogates the target to generate kinetic fingerprints by intramolecular single-molecule Förster resonance energy transfer (smFRET) that are recorded by single-molecule fluorescence microscopy and identify the target after kinetic filtering and data analysis. We optimize the sensor design, use formamide to further accelerate the fingerprinting kinetics, and maximize sensitivity by removing non-target-bound probes using toehold-mediated strand displacement to reduce background. We show that iSiMREPS can detect, in as little as 10 s, two distinct, promising cancer biomarkers-miR-141 and a common EGFR exon 19 deletion-reaching a limit of detection (LOD) of ~3 fM and a mutant allele fraction among excess wild-type as low as 1 in 1 million, or 0.0001%. We anticipate that iSiMREPS will find utility in research and clinical diagnostics based on its features of rapid detection, high specificity, sensitivity, and generalizability.
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Affiliation(s)
- Kunal Khanna
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, United States
| | - Shankar Mandal
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, United States
| | - Aaron T Blanchard
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, United States; Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, United States; Michigan Society of Fellows, University of Michigan, Ann Arbor, MI 48109, United States
| | - Muneesh Tewari
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, MI, 48109, United States; Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI, 48109, United States; Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, 48109, United States; Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, United States
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, United States; Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI, 48109, United States; Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, 48109, United States.
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI, 48109, United States; Center for RNA Biomedicine, University of Michigan, Ann Arbor, MI, 48109, United States; Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, MI, 48109, United States.
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9
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Ghosh S, Li N, Xiong Y, Ju YG, Rathslag MP, Onal EG, Falkiewicz E, Kohli M, Cunningham BT. A compact photonic resonator absorption microscope for point of care digital resolution nucleic acid molecular diagnostics. BIOMEDICAL OPTICS EXPRESS 2021; 12:4637-4650. [PMID: 34513214 PMCID: PMC8407813 DOI: 10.1364/boe.427475] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 06/24/2021] [Accepted: 06/27/2021] [Indexed: 05/05/2023]
Abstract
Rapid, sensitive, and selective detection of nucleic acid biomarkers for health diagnostic applications becomes feasible for point of care scenarios when the detection instrument is inexpensive, simple, and robust. Here, we report the design, implementation, and characterization of a point of care instrument for photonic resonator absorption microscopy (PRAM) that takes advantage of resonant optical coupling between plasmonic gold nanoparticle tags and a photonic crystal (PC) surface. Matching the PC resonant wavelength to the gold nanoparticle's surface plasmon wavelength generates localized and efficient quenching of the PC resonant reflection intensity, resulting in the ability to clearly detect and count individual gold nanoparticles when they are captured on the PC surface. Surface-captured nanoparticles are observed by illuminating the PC at normal incidence with polarized light from a low-intensity red LED, and recording of PC reflected intensity on an inexpensive CMOS image sensor. A contrast limited adaptive histogram equalization (CLAHE) image processing algorithm was applied to derive counts of captured nanoparticles. The instrument is utilized in the context of an activate capture + digital counting (AC + DC) assay for a specific miRNA sequence, using nucleic acid toehold probes applied to gold nano-urchin (AuNU) nanoparticles to achieve 160 aM detection limits in a 30 min. assay.
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Affiliation(s)
- Shreya Ghosh
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- S. G. and N. L. contributed equally to this work
| | - Nantao Li
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- S. G. and N. L. contributed equally to this work
| | - Yanyu Xiong
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Young-Gu Ju
- Department of Physics Education, Kyungpook National University, 80 Daehak-ro, Sangyeok-dong, Buk-gu, Daegu, Republic of Korea
| | - Michael P Rathslag
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Ege G Onal
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Erika Falkiewicz
- School of Integrative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Manish Kohli
- Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
| | - Brian T Cunningham
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
- Cancer Center at Illinois, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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10
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Cheng X, Yin W. Probing Biosensing Interfaces With Single Molecule Localization Microscopy (SMLM). Front Chem 2021; 9:655324. [PMID: 33996750 PMCID: PMC8117217 DOI: 10.3389/fchem.2021.655324] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 03/16/2021] [Indexed: 11/23/2022] Open
Abstract
Far field single molecule localization microscopy (SMLM) has been established as a powerful tool to study biological structures with resolution far below the diffraction limit of conventional light microscopy. In recent years, the applications of SMLM have reached beyond traditional cellular imaging. Nanostructured interfaces are enriched with information that determines their function, playing key roles in applications such as chemical catalysis and biological sensing. SMLM enables detailed study of interfaces at an individual molecular level, allowing measurements of reaction kinetics, and detection of rare events not accessible to ensemble measurements. This paper provides an update to the progress made to the use of SMLM in characterizing nanostructured biointerfaces, focusing on practical aspects, recent advances, and emerging opportunities from an analytical chemistry perspective.
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Affiliation(s)
- Xiaoyu Cheng
- State Key Laboratory for Modern Optical Instrumentations, National Engineering Research Center of Optical Instrumentation, College of Optical Science and Engineering, Zhejiang University, Hangzhou, China
| | - Wei Yin
- Core Facilities, School of Medicine, Zhejiang University, Hangzhou, China
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11
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Chatzimichail S, Supramaniam P, Salehi-Reyhani A. Absolute Quantification of Protein Copy Number in Single Cells With Immunofluorescence Microscopy Calibrated Using Single-Molecule Microarrays. Anal Chem 2021; 93:6656-6664. [PMID: 33876929 DOI: 10.1021/acs.analchem.0c05177] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Great strides toward routine single-cell analyses have been made over the last decade, particularly in the field of transcriptomics. For proteomics, amplification is not currently possible and has necessitated the development of ultrasensitive platforms capable of performing such analyses on single cells. These platforms are improving in terms of throughput and multiplexability but still fall short in relation to more established methods such as fluorescence microscopy. However, microscopy methods rely on fluorescence intensity as a proxy for protein abundance and are not currently capable of reporting this in terms of an absolute copy number. Here, a microfluidic implementation of single-molecule microarrays for single-cell analysis is assessed in its ability to calibrate fluorescence microscopy data. We show that the equivalence of measurements of the steady-state distribution of protein abundance to single-molecule microarray data can be exploited to pave the way for absolute quantitation by fluorescence and immunofluorescence microscopy. The methods presented have been developed using GFP but are extendable to other proteins and other biomolecules of interest.
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Affiliation(s)
| | | | - Ali Salehi-Reyhani
- Department of Surgery & Cancer, Imperial College London, London W12 0HS, U.K
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12
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Abstract
Selective and sensitive detection of nucleic acid biomarkers is of great significance in early-stage diagnosis and targeted therapy. Therefore, the development of diagnostic methods capable of detecting diseases at the molecular level in biological fluids is vital to the emerging revolution in the early diagnosis of diseases. However, the vast majority of the currently available ultrasensitive detection strategies involve either target/signal amplification or involve complex designs. Here, using a p53 tumor suppressor gene whose mutation has been implicated in more than 50% of human cancers, we show a background-free ultrasensitive detection of this gene on a simple platform. The sensor exhibits a relatively static mid-FRET state in the absence of a target that can be attributed to the time-averaged fluorescence intensity of fast transitions among multiple states, but it undergoes continuous dynamic switching between a low- and a high-FRET state in the presence of a target, allowing a high-confidence detection. In addition to its simple design, the sensor has a detection limit down to low femtomolar (fM) concentration without the need for target amplification. We also show that this sensor is highly effective in discriminating against single-nucleotide polymorphisms (SNPs). Given the generic hybridization-based detection platform, the sensing strategy developed here can be used to detect a wide range of nucleic acid sequences enabling early diagnosis of diseases and screening genetic disorders.
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Affiliation(s)
- Anoja Megalathan
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Kalani M Wijesinghe
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
| | - Soma Dhakal
- Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284, United States
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13
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Mandal S, Li Z, Chatterjee T, Khanna K, Montoya K, Dai L, Petersen C, Li L, Tewari M, Johnson-Buck A, Walter NG. Direct Kinetic Fingerprinting for High-Accuracy Single-Molecule Counting of Diverse Disease Biomarkers. Acc Chem Res 2021; 54:388-402. [PMID: 33382587 DOI: 10.1021/acs.accounts.0c00621] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methods for detecting and quantifying disease biomarkers in biofluids with high specificity and sensitivity play a pivotal role in enabling clinical diagnostics, including point-of-care tests. The most widely used molecular biomarkers include proteins, nucleic acids, hormones, metabolites, and other small molecules. While numerous methods have been developed for analyzing biomarkers, most techniques are challenging to implement for clinical use due to insufficient analytical performance, high cost, and/or other practical shortcomings. For instance, the detection of cell-free nucleic acid (cfNA) biomarkers by digital PCR and next-generation sequencing (NGS) requires time-consuming nucleic acid extraction steps, often introduces enzymatic amplification bias, and can be costly when high specificity is required. While several amplification-free methods for detecting cfNAs have been reported, these techniques generally suffer from low specificity and sensitivity. Meanwhile, the quantification of protein biomarkers is generally performed using immunoassays such as enzyme-linked immunosorbent assay (ELISA); the analytical performance of these methods is often limited by the availability of antibodies with high affinity and specificity as well as the significant nonspecific binding of antibodies to assay surfaces. To address the drawbacks of existing biomarker detection methods and establish a universal diagnostics platform capable of detecting different types of analytes, we have developed an amplification-free approach, named single-molecule recognition through equilibrium Poisson sampling (SiMREPS), for the detection of diverse biomarkers with arbitrarily high specificity and single-molecule sensitivity. SiMREPS utilizes the transient, reversible binding of fluorescent detection probes to immobilized target molecules to generate kinetic fingerprints that are detected by single-molecule fluorescence microscopy. The analysis of these kinetic fingerprints enables nearly perfect discrimination between specific binding to target molecules and any nonspecific binding. Early proof-of-concept studies demonstrated the in vitro detection of miRNAs with a limit of detection (LOD) of approximately 1 fM and >500-fold selectivity for single-nucleotide polymorphisms. The SiMREPS approach was subsequently expanded to the detection of rare mutant DNA alleles from biofluids at mutant allele fractions of as low as 1 in 1 million, corresponding to a specificity of >99.99999%. Recently, SiMREPS was generalized to protein quantification using dynamically binding antibody probes, permitting LODs in the low-femtomolar to attomolar range. Finally, SiMREPS has been demonstrated to be suitable for the in situ detection of miRNAs in cultured cells, the quantification of small-molecule toxins and drugs, and the monitoring of telomerase activity at the single-molecule level. In this Account, we discuss the principles of SiMREPS for the highly specific and sensitive detection of molecular analytes, including considerations for assay design. We discuss the generality of SiMREPS for the detection of very disparate analytes and provide an overview of data processing methods, including the expansion of the dynamic range using super-resolution analysis and the improvement of performance using deep learning algorithms. Finally, we describe current challenges, opportunities, and future directions for the SiMREPS approach.
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14
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Li J, Zhang L, Johnson-Buck A, Walter NG. Automatic classification and segmentation of single-molecule fluorescence time traces with deep learning. Nat Commun 2020; 11:5833. [PMID: 33203879 PMCID: PMC7673028 DOI: 10.1038/s41467-020-19673-1] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 10/20/2020] [Indexed: 01/19/2023] Open
Abstract
Traces from single-molecule fluorescence microscopy (SMFM) experiments exhibit photophysical artifacts that typically necessitate human expert screening, which is time-consuming and introduces potential for user-dependent expectation bias. Here, we use deep learning to develop a rapid, automatic SMFM trace selector, termed AutoSiM, that improves the sensitivity and specificity of an assay for a DNA point mutation based on single-molecule recognition through equilibrium Poisson sampling (SiMREPS). The improved performance of AutoSiM is based on accepting both more true positives and fewer false positives than the conventional approach of hidden Markov modeling (HMM) followed by hard thresholding. As a second application, the selector is used for automated screening of single-molecule Förster resonance energy transfer (smFRET) data to identify high-quality traces for further analysis, and achieves ~90% concordance with manual selection while requiring less processing time. Finally, we show that AutoSiM can be adapted readily to novel datasets, requiring only modest Transfer Learning.
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Affiliation(s)
- Jieming Li
- Single Molecule Analysis Group, Department of Chemistry and Center for RNA Biomedicine, The University of Michigan, Ann Arbor, MI, USA
- Bristol-Myers Squibb Company, New Brunswick, NJ, USA
| | - Leyou Zhang
- Department of Physics, The University of Michigan, Ann Arbor, MI, USA
- Google, Pittsburgh, PA, USA
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry and Center for RNA Biomedicine, The University of Michigan, Ann Arbor, MI, USA.
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI, USA.
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry and Center for RNA Biomedicine, The University of Michigan, Ann Arbor, MI, USA.
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15
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Chatterjee T, Knappik A, Sandford E, Tewari M, Choi SW, Strong WB, Thrush EP, Oh KJ, Liu N, Walter NG, Johnson-Buck A. Direct kinetic fingerprinting and digital counting of single protein molecules. Proc Natl Acad Sci U S A 2020; 117:22815-22822. [PMID: 32868420 PMCID: PMC7502736 DOI: 10.1073/pnas.2008312117] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The sensitive and accurate quantification of protein biomarkers plays important roles in clinical diagnostics and biomedical research. Sandwich ELISA and its variants accomplish the capture and detection of a target protein via two antibodies that tightly bind at least two distinct epitopes of the same antigen and have been the gold standard for sensitive protein quantitation for decades. However, existing antibody-based assays cannot distinguish between signal arising from specific binding to the protein of interest and nonspecific binding to assay surfaces or matrix components, resulting in significant background signal even in the absence of the analyte. As a result, they generally do not achieve single-molecule sensitivity, and they require two high-affinity antibodies as well as stringent washing to maximize sensitivity and reproducibility. Here, we show that surface capture with a high-affinity antibody combined with kinetic fingerprinting using a dynamically binding, low-affinity fluorescent antibody fragment differentiates between specific and nonspecific binding at the single-molecule level, permitting the direct, digital counting of single protein molecules with femtomolar-to-attomolar limits of detection (LODs). We apply this approach to four exemplary antigens spiked into serum, demonstrating LODs 55- to 383-fold lower than commercially available ELISA. As a real-world application, we establish that endogenous interleukin-6 (IL-6) can be quantified in 2-µL serum samples from chimeric antigen receptor T cell (CAR-T cell) therapy patients without washing away excess serum or detection probes, as is required in ELISA-based approaches. This kinetic fingerprinting thus exhibits great potential for the ultrasensitive, rapid, and streamlined detection of many clinically relevant proteins.
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Affiliation(s)
- Tanmay Chatterjee
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055
| | - Achim Knappik
- Life Science Group, Antibodies Division, Bio-Rad AbD Serotec GmbH, 82178 Puchheim, Germany
| | - Erin Sandford
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109-1055
| | - Muneesh Tewari
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109-1055
| | - Sung Won Choi
- Department of Pediatrics, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109-1055
| | - William B Strong
- Life Science Group, Bio-Rad Laboratories, Inc., Hercules, CA 94547
| | - Evan P Thrush
- Life Science Group, Bio-Rad Laboratories, Inc., Hercules, CA 94547
| | - Kenneth J Oh
- Life Science Group, Bio-Rad Laboratories, Inc., Hercules, CA 94547
| | - Ning Liu
- Life Science Group, Bio-Rad Laboratories, Inc., Hercules, CA 94547
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055;
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055;
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, MI 48109-1055
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16
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Huang Q, Li N, Zhang H, Che C, Sun F, Xiong Y, Canady TD, Cunningham BT. Critical Review: digital resolution biomolecular sensing for diagnostics and life science research. LAB ON A CHIP 2020; 20:2816-2840. [PMID: 32700698 PMCID: PMC7485136 DOI: 10.1039/d0lc00506a] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
One of the frontiers in the field of biosensors is the ability to quantify specific target molecules with enough precision to count individual units in a test sample, and to observe the characteristics of individual biomolecular interactions. Technologies that enable observation of molecules with "digital precision" have applications for in vitro diagnostics with ultra-sensitive limits of detection, characterization of biomolecular binding kinetics with a greater degree of precision, and gaining deeper insights into biological processes through quantification of molecules in complex specimens that would otherwise be unobservable. In this review, we seek to capture the current state-of-the-art in the field of digital resolution biosensing. We describe the capabilities of commercially available technology platforms, as well as capabilities that have been described in published literature. We highlight approaches that utilize enzymatic amplification, nanoparticle tags, chemical tags, as well as label-free biosensing methods.
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Affiliation(s)
- Qinglan Huang
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Nantao Li
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Hanyuan Zhang
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Congnyu Che
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- Department of Bioengineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Fu Sun
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Yanyu Xiong
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Taylor D. Canady
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
| | - Brian T. Cunningham
- Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801
- Holonyak Micro and Nanotechnology Laboratory, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- Department of Bioengineering, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana–Champaign, Urbana, IL 61801
- Illinois Cancer Center, University of Illinois at Urbana-Champaign Urbana, IL 61801
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17
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Lackey HH, Peterson EM, Harris JM, Heemstra JM. Probing the Mechanism of Structure-Switching Aptamer Assembly by Super-Resolution Localization of Individual DNA Molecules. Anal Chem 2020; 92:6909-6917. [PMID: 32297506 DOI: 10.1021/acs.analchem.9b05563] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Oligonucleotide aptamers can be converted into structure-switching biosensors by incorporating a short, typically labeled oligonucleotide that is complementary to the analyte-binding region. Binding of a target analyte can disrupt the hybridization equilibrium between the aptamer and the labeled-complementary oligo producing a concentration-dependent signal for target-analyte sensing. Despite its importance in the performance of a biosensor, the mechanism of analyte-response of most structure-switching aptamers is not well understood. In this work, we employ single-molecule fluorescence imaging to investigate the competitive kinetics of association of a labeled complementary oligonucleotide and a target analyte, l-tyrosinamide (L-Tym), interacting with an L-Tym-binding aptamer. The complementary readout strand is fluorescently labeled, allowing us to measure its hybridization kinetics with individual aptamers immobilized on a surface and located with super-resolution techniques; the small-molecule L-Tym analyte is not labeled in order to avoid having an attached dye molecule impact its interactions with the aptamer. We measure the association kinetics of unlabeled L-Tym by detecting its influence on the hybridization of the labeled complementary strand. We find that L-Tym slows the association rate of the complementary strand with the aptamer but does not impact its dissociation rate, suggesting an SN1-like mechanism where the complementary strand must dissociate before L-Tym can bind. The competitive model revealed a slow association rate between L-Tym and the aptamer, producing a long-lived L-Tym-aptamer complex that blocks hybridization with the labeled complementary strand. These results provide insight about the kinetics and mechanism of analyte recognition in this structure-switching aptamer, and the methodology provides a general means of measuring the rates of unlabeled-analyte binding kinetics in aptamer-based biosensors.
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Affiliation(s)
- Hershel H Lackey
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Eric M Peterson
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Joel M Harris
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Jennifer M Heemstra
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States.,Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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18
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Single-molecule analysis of nucleic acid biomarkers - A review. Anal Chim Acta 2020; 1115:61-85. [PMID: 32370870 DOI: 10.1016/j.aca.2020.03.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Revised: 02/29/2020] [Accepted: 03/02/2020] [Indexed: 12/11/2022]
Abstract
Nucleic acids are important biomarkers for disease detection, monitoring, and treatment. Advances in technologies for nucleic acid analysis have enabled discovery and clinical implementation of nucleic acid biomarkers. However, challenges remain with technologies for nucleic acid analysis, thereby limiting the use of nucleic acid biomarkers in certain contexts. Here, we review single-molecule technologies for nucleic acid analysis that can be used to overcome these challenges. We first discuss the various types of nucleic acid biomarkers important for clinical applications and conventional technologies for nucleic acid analysis. We then discuss technologies for single-molecule in vitro and in situ analysis of nucleic acid biomarkers. Finally, we discuss other ultra-sensitive techniques for nucleic acid biomarker detection.
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19
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Lackey HH, Chen Z, Harris JM, Peterson EM, Heemstra JM. Single-Molecule Kinetics Show DNA Pyrimidine Content Strongly Affects RNA:DNA and TNA:DNA Heteroduplex Dissociation Rates. ACS Synth Biol 2020; 9:249-253. [PMID: 31909980 DOI: 10.1021/acssynbio.9b00471] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The heteroduplex hybridization thermodynamics of DNA with either RNA or TNA are greatly affected by DNA pyrimidine content, where increased DNA pyrimidine content leads to significantly increased duplex stability. Little is known, however, about the effect that purine or pyrimidine content has on the hybridization kinetics of these duplexes. In this work, single-molecule imaging is used to measure the hybridization kinetics of oligonucleotides having varying DNA pyrimidine content with complementary DNA, RNA, and TNA sequences. Results suggest that the change in duplex stability from DNA pyrimidine content (corresponding to purine content in the complementary TNA or RNA) is primarily due to changes in the dissociation rate, and not single-strand ordering or other structural changes that increase the association rate. Decreases in heteroduplex hybridization rates with pyrimidine content are similar for RNA and TNA, indicating that TNA behaves as a kinetic analogue for RNA.
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Affiliation(s)
- Hershel H. Lackey
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Zhe Chen
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Joel M. Harris
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Eric M. Peterson
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Jennifer M. Heemstra
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
- Department of Chemistry, Emory University, Atlanta, Georgia 30322, United States
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20
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Chatterjee T, Li Z, Khanna K, Montoya K, Tewari M, Walter NG, Johnson-Buck A. Ultraspecific analyte detection by direct kinetic fingerprinting of single molecules. Trends Analyt Chem 2020; 123:115764. [PMID: 32863484 PMCID: PMC7451408 DOI: 10.1016/j.trac.2019.115764] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The detection and quantification of biomarkers have numerous applications in biological research and medicine. The most widely used methods to detect nucleic acids require amplification via the polymerase chain reaction (PCR). However, errors arising from the imperfect copying fidelity of DNA polymerases, limited specificity of primers, and heat-induced damage reduce the specificity of PCR-based methods, particularly for single-nucleotide variants. Furthermore, not all analytes can be amplified efficiently. While amplification-free methods avoid these pitfalls, the specificity of most such methods is strictly constrained by probe binding thermodynamics, which for example hampers detection of rare somatic mutations. In contrast, single-molecule recognition through equilibrium Poisson sampling (SiMREPS) provides ultraspecific detection with single-molecule and single-nucleotide sensitivity by monitoring the repetitive interactions of a fluorescent probe with surface-immobilized targets. In this review, we discuss SiMREPS in comparison with other analytical approaches, and describe its utility in quantifying a range of nucleic acids and other analytes.
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Affiliation(s)
- Tanmay Chatterjee
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Zi Li
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Kunal Khanna
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Karen Montoya
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Muneesh Tewari
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
- Biointerfaces Institute, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for Computational Medicine and Bioinformatics, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Alexander Johnson-Buck
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
- Department of Internal Medicine, Division of Hematology/Oncology, University of Michigan, Ann Arbor, Michigan 48109, United States
- Center for RNA Biomedicine, University of Michigan, Ann Arbor, Michigan 48109, United States
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21
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Peterson EM, Reece EJ, Li W, Harris JM. Super-Resolution Imaging of Competitive Unlabeled DNA Hybridization Reveals the Influence of Fluorescent Labels on Duplex Formation and Dissociation Kinetics. J Phys Chem B 2019; 123:10746-10756. [PMID: 31731835 DOI: 10.1021/acs.jpcb.9b09736] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Single-molecule fluorescence imaging is a powerful method to measure reversible reaction kinetics, allowing one to monitor the bound state of individual probe molecules with fluorescently labeled targets. In the case of DNA hybridization, previous studies have shown that the presence of a fluorescent label on a target strand can exhibit significant influence on the stability of a DNA duplex that is formed. In this work, we have developed a super-resolution imaging method to measure the hybridization kinetics of unlabeled target DNA that compete with a fluorescently labeled tracer DNA strand to hybridize with an unlabeled probe DNA immobilized at a surface. The hybridization of an unlabeled DNA target cannot be detected directly, but its presence blocks the immobilized probe DNA, influencing the measured time intervals between labeled DNA hybridization events. We derive a model for competitive hybridization kinetics to extract the association and dissociation rate constants of the unlabeled species from the distribution of time intervals between hybridization events of the labeled tracer DNA at individual localized DNA probe sites. We use this methodology to determine the hybridization kinetics of a model 11-mer unlabeled target DNA strand and then determine how five different fluorescent labels attached to the same target DNA strand impact the hybridization kinetics. Compared to the unlabeled target, these labels can slow the association and dissociation rates by as much as a factor of 5. The super-resolution time-interval methodology provides a unique approach to determining fundamental (label-free) rates of DNA hybridization, revealing the significant influence of fluorescent labels on these kinetics. This measurement concept can be extended to studies of other reversible reaction systems, where kinetics of unlabeled species can be determined from their influence on the reaction of a labeled species with localized probe molecules on a surface.
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Affiliation(s)
- Eric M Peterson
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Eric J Reece
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Wenyuan Li
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
| | - Joel M Harris
- Department of Chemistry , University of Utah , 315 South 1400 East , Salt Lake City , Utah 84112-0850 , United States
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22
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Digital-resolution detection of microRNA with single-base selectivity by photonic resonator absorption microscopy. Proc Natl Acad Sci U S A 2019; 116:19362-19367. [PMID: 31501320 DOI: 10.1073/pnas.1904770116] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Circulating exosomal microRNA (miR) represents a new class of blood-based biomarkers for cancer liquid biopsy. The detection of miR at a very low concentration and with single-base discrimination without the need for sophisticated equipment, large volumes, or elaborate sample processing is a challenge. To address this, we present an approach that is highly specific for a target miR sequence and has the ability to provide "digital" resolution of individual target molecules with high signal-to-noise ratio. Gold nanoparticle tags are prepared with thermodynamically optimized nucleic acid toehold probes that, when binding to a target miR sequence, displace a probe-protecting oligonucleotide and reveal a capture sequence that is used to selectively pull down the target-probe-nanoparticle complex to a photonic crystal (PC) biosensor surface. By matching the surface plasmon-resonant wavelength of the nanoparticle tag to the resonant wavelength of the PC nanostructure, the reflected light intensity from the PC is dramatically and locally quenched by the presence of each individual nanoparticle, enabling a form of biosensor microscopy that we call Photonic Resonator Absorption Microscopy (PRAM). Dynamic PRAM imaging of nanoparticle tag capture enables direct 100-aM limit of detection and single-base mismatch selectivity in a 2-h kinetic discrimination assay. The PRAM assay demonstrates that ultrasensitivity (<1 pM) and high selectivity can be achieved on a direct readout diagnostic.
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23
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Li L, Yu Y, Wang C, Han Q, Su X. Transient Hybridization Directed Nanoflare for Single-Molecule miRNA Imaging. Anal Chem 2019; 91:11122-11128. [PMID: 31402644 DOI: 10.1021/acs.analchem.9b01766] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Accurate quantifications of cellular miRNAs are important not only for accelerating them becoming reliable diagnostics biomarkers but also for deeply understanding their influence on central signaling pathways. Although single-molecule miRNA imaging permits quantifying biomolecules at the single-molecule level, it is limited by the sensitivity and specificity of hybridization-based probes. We report a miRNA single-molecule imaging method by using conjugated polymer nanoparticle (CPN) labeled short DNA probe termed as a nanoflare. The transient hybridization of the nanoflares and target miRNAs yields a featured single-molecule kinetics signal rendering high single-molecule sensitivity and specificity. miRNA can be detected with a remarkable detection limit of 1 fM without using any amplification steps. The discrimination capability of homologous miRNAs was also demonstrated. Taking advantage of the featured single-molecule signal of the nanoflare, we can directly count single miR-21 molecules in single cells by using highly inclined and laminated optical sheet (HILO) microscopy. The statistics of the counting reveals miR-21's cell-to-cell fluctuation and differential expression of tumor cells and normal cells.
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Affiliation(s)
- Lina Li
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Yingjie Yu
- Institute of Translational Medicine , The First Affiliated Hospital of Shenzhen University, Shenzhen Second People's Hospital , Shenzhen 518039 , China
| | - Congshan Wang
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Qianqian Han
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
| | - Xin Su
- College of Life Science and Technology , Beijing University of Chemical Technology , Beijing 100029 , China
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24
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Chauvier A, Cabello-Villegas J, Walter NG. Probing RNA structure and interaction dynamics at the single molecule level. Methods 2019; 162-163:3-11. [PMID: 30951833 DOI: 10.1016/j.ymeth.2019.04.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 03/28/2019] [Accepted: 04/01/2019] [Indexed: 02/07/2023] Open
Abstract
RNA structures and their dynamic fluctuations lie at the heart of understanding key biological process such as transcription, splicing, translation and RNA decay. While conventional bulk assays have proven to identify and characterize key pathway intermediates, the generally dynamic nature of RNA structures renders the information obtained from time and ensemble averaging techniques necessarily lacking in critical details. Here we detail Single-Molecule Kinetic Analysis of RNA Transient Structure (SiM-KARTS), a method that readily monitors structural fluctuations of single RNA molecules through the repetitive interaction of fluorescent probes with an unlabeled, surface-immobilized RNA target of virtually any length and in any biological context. In addition, we demonstrate the broad applicability of SiM-KARTS by kinetically fingerprinting the binding of cognate tRNA ligand to single immobilized T-box riboswitch molecules. SiM-KARTS represents a valuable tool for probing biologically relevant structure and interaction features of potentially many diverse RNA metabolic pathways.
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Affiliation(s)
- Adrien Chauvier
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Javier Cabello-Villegas
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA
| | - Nils G Walter
- Single Molecule Analysis Group, Department of Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
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25
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Walter NG. Introduction to “Convergence of Science and Technology: Fluorescent Resolution of Single RNA Molecules”. Methods 2019; 153:1-2. [DOI: 10.1016/j.ymeth.2018.12.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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26
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Hayward SL, Lund PE, Kang Q, Johnson-Buck A, Tewari M, Walter NG. Ultraspecific and Amplification-Free Quantification of Mutant DNA by Single-Molecule Kinetic Fingerprinting. J Am Chem Soc 2018; 140:11755-11762. [PMID: 30125495 DOI: 10.1021/jacs.8b06685] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Conventional techniques for detecting rare DNA sequences require many cycles of PCR amplification for high sensitivity and specificity, potentially introducing significant biases and errors. While amplification-free methods exist, they rarely achieve the ability to detect single molecules, and their ability to discriminate between single-nucleotide variants is often dictated by the specificity limits of hybridization thermodynamics. Here we show that a direct detection approach using single-molecule kinetic fingerprinting can surpass the thermodynamic discrimination limit by 3 orders of magnitude, with a dynamic range of up to 5 orders of magnitude with optional super-resolution analysis. This approach detects mutations as subtle as the drug-resistance-conferring cancer mutation EGFR T790M (a single C → T substitution) with an estimated specificity of 99.99999%, surpassing even the leading PCR-based methods and enabling detection of 1 mutant molecule in a background of at least 1 million wild-type molecules. This level of specificity revealed rare, heat-induced cytosine deamination events that introduce false positives in PCR-based detection, but which can be overcome in our approach through milder thermal denaturation and enzymatic removal of damaged nucleobases.
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