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Sathirapongsasuti N, Panaksri A, Jusain B, Boonyagul S, Pechprasarn S, Jantanasakulwong K, Suksuwan A, Thongkham S, Tanadchangsaeng N. Enhancing protein trapping efficiency of graphene oxide-polybutylene succinate nanofiber membrane via molecular imprinting. Sci Rep 2023; 13:15398. [PMID: 37717111 PMCID: PMC10505162 DOI: 10.1038/s41598-023-42646-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Accepted: 09/13/2023] [Indexed: 09/18/2023] Open
Abstract
Filtration of biological liquids has been widely employed in biological, medical, and environmental investigations due to its convenience; many could be performed without energy and on-site, particularly protein separation. However, most available membranes are universal protein absorption or sub-fractionation due to molecule sizes or properties. SPMA, or syringe-push membrane absorption, is a quick and easy way to prepare biofluids for protein evaluation. The idea of initiating SPMA was to filter proteins from human urine for subsequent proteomic analysis. In our previous study, we developed nanofiber membranes made from polybutylene succinate (PBS) composed of graphene oxide (GO) for SPMA. In this study, we combined molecular imprinting with our developed PBS fiber membranes mixed with graphene oxide to improve protein capture selectivity in a lock-and-key fashion and thereby increase the efficacy of protein capture. As a model, we selected albumin from human serum (ABH), a clinically significant urine biomarker, for proteomic application. The nanofibrous membrane was generated utilizing the electrospinning technique with PBS/GO composite. The PBS/GO solution mixed with ABH was injected from a syringe and transformed into nanofibers by an electric voltage, which led the fibers to a rotating collector spinning for fiber collection. The imprinting process was carried out by removing the albumin protein template from the membrane through immersion of the membrane in a 60% acetonitrile solution for 4 h to generate a molecular imprint on the membrane. Protein trapping ability, high surface area, the potential for producing affinity with proteins, and molecular-level memory were all evaluated using the fabricated membrane morphology, protein binding capacity, and quantitative protein measurement. This study revealed that GO is a controlling factor, increasing electrical conductivity and reducing fiber sizes and membrane pore areas in PBS-GO-composites. On the other hand, the molecular imprinting did not influence membrane shape, nanofiber size, or density. Human albumin imprinted membrane could increase the PBS-GO membrane's ABH binding capacity from 50 to 83%. It can be indicated that applying the imprinting technique in combination with the graphene oxide composite technique resulted in enhanced ABH binding capabilities than using either technique individually in membrane fabrication. The suitable protein elution solution is at 60% acetonitrile with an immersion time of 4 h. Our approach has resulted in the possibility of improving filter membranes for protein enrichment and storage in a variety of biological fluids.
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Affiliation(s)
- Nuankanya Sathirapongsasuti
- Program in Translational Medicine, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Ratchathewi, Bangkok, Thailand
- Chakri Naruebodindra Medical Institute, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bang Pli, Samut Prakan, Thailand
| | - Anuchan Panaksri
- College of Biomedical Engineering, Rangsit University, Lak Hok, Pathumthani, Thailand
| | - Benjabhorn Jusain
- College of Biomedical Engineering, Rangsit University, Lak Hok, Pathumthani, Thailand
| | - Sani Boonyagul
- College of Biomedical Engineering, Rangsit University, Lak Hok, Pathumthani, Thailand
| | - Suejit Pechprasarn
- College of Biomedical Engineering, Rangsit University, Lak Hok, Pathumthani, Thailand
| | - Kittisak Jantanasakulwong
- School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae Hia, Chiang Mai, Thailand
- National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathumthani, Thailand
| | - Acharee Suksuwan
- The Halal Science Center, Chulalongkorn University, Pathum Wan, Bangkok, Thailand
| | - Somprasong Thongkham
- National Nanotechnology Center (NANOTEC), National Science and Technology Development Agency (NSTDA), Klong Luang, Pathumthani, Thailand
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Hilton SH, White IM. Advances in the analysis of single extracellular vesicles: A critical review. SENSORS AND ACTUATORS REPORTS 2021; 3:100052. [PMID: 35098157 PMCID: PMC8792802 DOI: 10.1016/j.snr.2021.100052] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
There is an ever-growing need for new cancer diagnostic approaches that provide earlier diagnosis as well as richer diagnostic, prognostic, and resistance information. Extracellular vesicles (EVs) recovered from a liquid biopsy have paradigm-shifting potential to offer earlier and more complete diagnostic information in the form of a minimally invasive liquid biopsy. However, much remains unknown about EVs, and current analytical approaches are unable to provide precise information about the contents and source of EVs. New approaches have emerged to analyze EVs at the single particle level, providing the opportunity to study biogenesis, correlate markers for higher specificity, and connect EV cargo with the source or destination. In this critical review we describe and analyze methods for single EV analysis that have emerged over the last five years. In addition, we note that current methods are limited in their adoption due to cost and complexity and we offer opportunities for the research community to address this challenge.
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Wang Y, Shah V, Lu A, Pachler E, Cheng B, Di Carlo D. Counting of enzymatically amplified affinity reactions in hydrogel particle-templated drops. LAB ON A CHIP 2021; 21:3438-3448. [PMID: 34378611 DOI: 10.1039/d1lc00344e] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Counting of numerous compartmentalized enzymatic reactions underlies quantitative and high sensitivity immunodiagnostic assays. However, digital enzyme-linked immunosorbent assays (ELISA) require specialized instruments which have slowed adoption in research and clinical labs. We present a lab-on-a-particle solution to digital counting of thousands of single enzymatic reactions. Hydrogel particles are used to bind enzymes and template the formation of droplets that compartmentalize reactions with simple pipetting steps. These hydrogel particles can be made at a high throughput, stored, and used during the assay to create ∼500 000 compartments within 2 minutes. These particles can also be dried and rehydrated with sample, amplifying the sensitivity of the assay by driving affinity interactions on the hydrogel surface. We demonstrate digital counting of β-galactosidase enzyme at a femtomolar detection limit with a dynamic range of 3 orders of magnitude using standard benchtop equipment and experiment techniques. This approach can faciliate the development of digital ELISAs with reduced need for specialized microfluidic devices, instruments, or imaging systems.
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Affiliation(s)
- Yilian Wang
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
| | - Vishwesh Shah
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
| | - Angela Lu
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
| | - Ella Pachler
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
| | - Brian Cheng
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
| | - Dino Di Carlo
- Department of Bioengineering, University of California, Los Angeles, CA, USA.
- Department of Mechanical and Aerospace Engineering, California NanoSystems Institute, Jonsson Comprehensive Cancer Center, University of California, Los Angeles, CA, USA
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Soga N, Ota A, Nakajima K, Watanabe R, Ueno H, Noji H. Monodisperse Liposomes with Femtoliter Volume Enable Quantitative Digital Bioassays of Membrane Transporters and Cell-Free Gene Expression. ACS NANO 2020; 14:11700-11711. [PMID: 32864949 DOI: 10.1021/acsnano.0c04354] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Digital bioassays have emerged as a new category of bioanalysis. However, digital bioassays for membrane transporter proteins have not been well established yet despite high demands in molecular physiology and molecular pharmacology due to the lack of biologically functional monodisperse liposomes with femtoliter volumes. Here, we established a simple and robust method to produce femtoliter-sized liposomes (femto-liposomes). We prepared 106 monodispersed water-in-oil droplets stabilized by a lipid monolayer using a polyethylene glycol-coated femtoliter reactor array device. Droplets were subjected to the optimized emulsion transfer process for femto-liposome production. Liposomes were monodispersed (coefficient of variation = 5-15%) and had suitable diameter (0.6-5.3 μm) and uniform volumes of subfemtoliter or a few femtoliters; thus, they were termed uniform femto-liposomes. The unilamellarity of uniform femto-liposomes allowed quantitative single-molecule analysis of passive and active transporter proteins: α-hemolysin and FoF1-ATPase. Digital gene expression in uniform femto-liposomes (cell-free transcription and translation from single DNA molecules) was also demonstrated, showing the versatility of digital assays for membrane transporter proteins and cell-free synthetic biology.
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Affiliation(s)
- Naoki Soga
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Akira Ota
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Kota Nakajima
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Rikiya Watanabe
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
- PRIME, Japan Agency for Medical Research and Development, 1-7-1 Otemachi, Chiyoda-ku, Tokyo 100-0004, Japan
| | - Hiroshi Ueno
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
| | - Hiroyuki Noji
- Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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Markel U, Essani KD, Besirlioglu V, Schiffels J, Streit WR, Schwaneberg U. Advances in ultrahigh-throughput screening for directed enzyme evolution. Chem Soc Rev 2020; 49:233-262. [PMID: 31815263 DOI: 10.1039/c8cs00981c] [Citation(s) in RCA: 142] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Enzymes are versatile catalysts and their synthetic potential has been recognized for a long time. In order to exploit their full potential, enzymes often need to be re-engineered or optimized for a given application. (Semi-) rational design has emerged as a powerful means to engineer proteins, but requires detailed knowledge about structure function relationships. In turn, directed evolution methodologies, which consist of iterative rounds of diversity generation and screening, can improve an enzyme's properties with virtually no structural knowledge. Current diversity generation methods grant us access to a vast sequence space (libraries of >1012 enzyme variants) that may hide yet unexplored catalytic activities and selectivity. However, the time investment for conventional agar plate or microtiter plate-based screening assays represents a major bottleneck in directed evolution and limits the improvements that are obtainable in reasonable time. Ultrahigh-throughput screening (uHTS) methods dramatically increase the number of screening events per time, which is crucial to speed up biocatalyst design, and to widen our knowledge about sequence function relationships. In this review, we summarize recent advances in uHTS for directed enzyme evolution. We shed light on the importance of compartmentalization to preserve the essential link between genotype and phenotype and discuss how cells and biomimetic compartments can be applied to serve this function. Finally, we discuss how uHTS can inspire novel functional metagenomics approaches to identify natural biocatalysts for novel chemical transformations.
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Affiliation(s)
- Ulrich Markel
- Institute of Biotechnology, RWTH Aachen University, Worringer Weg 3, 52074 Aachen, Germany.
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Safdar S, Ven K, van Lent J, Pavie B, Rutten I, Dillen A, Munck S, Lammertyn J, Spasic D. DNA-only, microwell-based bioassay for multiplex nucleic acid detection with single base-pair resolution using MNAzymes. Biosens Bioelectron 2020; 152:112017. [PMID: 31941617 DOI: 10.1016/j.bios.2020.112017] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 01/08/2020] [Indexed: 12/17/2022]
Abstract
In disease diagnostics, single- and multiplex nucleic acid (NA) detection, with the potential to discriminate mutated strands, is of paramount importance. Current techniques that rely on target amplification or protein-enzyme based signal amplification are highly relevant, yet still plagued by diverse drawbacks including erroneous target amplification, and the limited stability of protein enzymes. As a solution, we present a multicomponent nucleic acid enzymes (MNAzymes)-based system for singleplex and multiplex detection of NA targets in microwells down to femtomolar (fM) concentrations, without the need for any target amplification or protein enzymes, while operating at room temperature and with single base-pair resolution. After successful validation of the MNAzymes in solution, their performance was further verified on beads in bulk and in femtoliter-sized microwells. The latter is not only a highly simplified system compared to previous microwell-based bioassays but, with the detection limit of 180 fM, it is to-date the most sensitive NAzyme-mediated, bead-based approach, that does not rely on target amplification or any additional signal amplification strategies. Furthermore, we demonstrated, for the first time, multiplexed target detection in microwells, both from buffer and nasopharyngeal swab samples, and presented superior single base-pair resolution of this assay. Because of the design flexibility of MNAzymes and direct demonstration in swab samples, this system holds great promise for multiplexed detection in other clinically relevant matrices without the need for any additional NA or protein components. Moreover, these findings open up the potential for the development of next-generation, protein-free diagnostic tools, including digital assays with single-molecule resolution.
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Affiliation(s)
- Saba Safdar
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
| | - Karen Ven
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
| | - Julie van Lent
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
| | - Benjamin Pavie
- VIB-KU Leuven Center for Brain & Disease Research, KU Leuven, 3000, Leuven, Belgium
| | - Iene Rutten
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
| | - Annelies Dillen
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
| | - Sebastian Munck
- VIB-KU Leuven Center for Brain & Disease Research, KU Leuven, 3000, Leuven, Belgium
| | - Jeroen Lammertyn
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium.
| | - Dragana Spasic
- Department of Biosystems, Biosensors Group, KU Leuven, 3001, Leuven, Belgium
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7
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Zhang Q, Zhang X, Li J, Gai H. Nonstochastic Protein Counting Analysis for Precision Biomarker Detection: Suppressing Poisson Noise at Ultralow Concentration. Anal Chem 2019; 92:654-658. [PMID: 31820622 DOI: 10.1021/acs.analchem.9b04809] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Protein counting analysis obtains the quantitative results of specific protein through counting the number of target signals and displays a great value in disease diagnosis. Current protein counting techniques just stochastically count a small portion of the target signal, which causes a considerable information loss and limits the accuracy and precision of the protein assay at ultralow concentration. Here, we present a nonstochastic and ultrasensitive protein counting method through combining multiround evaporation-induced particle sedimentation, grid-assisted multiframe imaging, and microsphere-enhanced high-resolution signals. Using carcinoembryonic antigen (CEA) as the model, the dynamic range was from 5 × 10-18 M (aM) to 5 × 10-16 M, and the limit of detection was 4.9 aM. For CEA-spiked plasma detection, the relative standard deviation and the relative error of CEA concentrations were both lower than 8.0%, and the recoveries reached 92.5% and 98.8% for 20.0 aM and 40.0 aM CEA respectively. Two clinical plasma samples were measured by the standard addition method, and the results showed little deviation with the values provided by the hospital. The established approach suppresses Poisson noise of the stochastic counting, offers ultrahigh sensitivity, and features a remarkable potential in early disease screening.
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Affiliation(s)
- Qingquan Zhang
- Jiangsu Key Laboratory of Green Synthesis for Functional Materials, School of Chemistry and Materials Science , Jiangsu Normal University , Xuzhou , Jiangsu 221116 , China
| | - Xuebing Zhang
- Jiangsu Key Laboratory of Green Synthesis for Functional Materials, School of Chemistry and Materials Science , Jiangsu Normal University , Xuzhou , Jiangsu 221116 , China
| | - Jiajia Li
- Jiangsu Key Laboratory of Green Synthesis for Functional Materials, School of Chemistry and Materials Science , Jiangsu Normal University , Xuzhou , Jiangsu 221116 , China
| | - Hongwei Gai
- Jiangsu Key Laboratory of Green Synthesis for Functional Materials, School of Chemistry and Materials Science , Jiangsu Normal University , Xuzhou , Jiangsu 221116 , China
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Akama K, Iwanaga N, Yamawaki K, Okuda M, Jain K, Ueno H, Soga N, Minagawa Y, Noji H. Wash- and Amplification-Free Digital Immunoassay Based on Single-Particle Motion Analysis. ACS NANO 2019; 13:13116-13126. [PMID: 31675215 DOI: 10.1021/acsnano.9b05917] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Digital enzyme-linked immunosorbent assay (ELISA) is a powerful analytical method for highly sensitive protein biomarker detection. The current protocol of digital ELISA requires multiple washing steps and signal amplification using an enzyme, which could be the potential drawback in in vitro diagnosis. In this study, we propose a digital immunoassay method, which we call "Digital HoNon-ELISA" (digital homogeneous non-enzymatic immunosorbent assay) for highly sensitive detection without washing and signal amplification. Target antigen molecules react with antibody-coated magnetic nanoparticles, which are then magnetically pulled into femtoliter-sized reactors. The antigens on the particles are captured by antibodies anchored on the bottom surface of the reactor via molecular tethers. Magnetic force enhances the efficiency of particle encapsulation in the reactors. Subsequent physical compartmentalization of the particles enhances the binding efficiency of antigen-carrying particles to the antibodies. The tethered particles show characteristic Brownian motion within a limited space by the molecular tethering, which is distinct from free diffusion or nonspecific binding of antigen-free particles. The number of tethered particles directly correlates with the concentration of the target antigen. Digital HoNon-ELISA was used with a prostate-specific antigen to achieve a detection of 0.093 pg/mL, which is over 9.0-fold the sensitivity of commercialized highly sensitive ELISA (0.84 pg/mL) and comparable to digital ELISA (0.055 pg/mL). This digital immunoassay strategy has sensitivity similar to digital ELISA with simplicity similar to homogeneous assay. Such similarity allows for potential application in rapid and simple digital diagnostic tests without the need for washing and enzymatic amplification.
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Affiliation(s)
- Kenji Akama
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Niina Iwanaga
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Koya Yamawaki
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Masaki Okuda
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Krupali Jain
- Central Research Laboratories , Sysmex Corporation , 4-4-4 Takatsukadai , Nishi-ku, Kobe 651-2271 , Japan
| | - Hiroshi Ueno
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Naoki Soga
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Yoshihiro Minagawa
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
| | - Hiroyuki Noji
- Department of Applied Chemistry, Graduate School of Engineering , The University of Tokyo , 7-3-1 Hongo , Bunkyo-ku, Tokyo 113-8656 , Japan
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9
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Complete inclusion of bioactive molecules and particles in polydimethylsiloxane: a straightforward process under mild conditions. Sci Rep 2019; 9:17575. [PMID: 31772250 PMCID: PMC6879495 DOI: 10.1038/s41598-019-54155-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 10/17/2019] [Indexed: 11/18/2022] Open
Abstract
By applying a slow curing process, we show that biomolecules can be incorporated via a simple process as liquid stable phases inside a polydimethylsiloxane (PDMS) matrix. The process is carried out under mild conditions with regards to temperature, pH and relative humidity, and is thus suitable for application to biological entities. Fluorescence and enzymatic activity measurements show that the biochemical properties of the proteins and enzyme tested are preserved, without loss due to adsorption at the liquid-polymer interface. Protected from external stimuli by the PDMS matrix, these soft liquid composite materials are new tools of interest for robotics, microfluidics, diagnostics and chemical microreactors.
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10
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Sharma H, Navalkar A, Maji SK, Agrawal A. Analysis of drug–protein interaction in bio-inspired microwells. SN APPLIED SCIENCES 2019. [DOI: 10.1007/s42452-019-0778-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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Miyajima K, Miwa Y, Kitamoto Y. Fabrication of porous FePt microcapsules for immunosensing techniques. Colloids Surf B Biointerfaces 2019; 173:407-411. [PMID: 30321798 DOI: 10.1016/j.colsurfb.2018.10.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2018] [Revised: 09/22/2018] [Accepted: 10/02/2018] [Indexed: 10/28/2022]
Abstract
Porous FePt microcapsules are fabricated for use in bead-based immunoassay technologies, that generally use magnetic spheres to immobilize biomolecules on their surface. The magnetic capsules can be used to carry assay reagents to reduce the time required to perform immunoassay processes, and microsize capsules are easier to manipulate magnetically than nanosize ones. Silica particles of approximately 2.5 μm diameter are used as templates and modified with poly(ethyleneimine) (PEI), which enables FePt nanoparticles to accumulate selectively on the template particles and an FePt shell to be formed by a polyol process. To increase the mechanical stability of the FePt nanoparticle assembly shell, a double-layered FePt nanoparticle assembly is fabricated by repeating the modification process of PEI and the synthesis process of FePt nanoparticles, resulting in the fabrication of magnetic capsules with a three-dimensional structure. We further investigate the ability of magnetic capsules to immobilize antibodies on their surface. Gold nanoparticles are used as linkers between the magnetic microcapsules and antibodies. The antibodies are successfully immobilized on the surface of the developed microsize FePt capsules.
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Affiliation(s)
- Kumiko Miyajima
- Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 2217-14 Hayashi-cho, Takamatsu, Kagawa, 761-0395, Japan.
| | - Yuki Miwa
- Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8502, Japan
| | - Yoshitaka Kitamoto
- Department of Materials Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa, 226-8502, Japan
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Anderson GP, Shriver-Lake LC, Walper SA, Ashford L, Zabetakis D, Liu JL, Breger JC, Brozozog Lee PA, Goldman ER. Genetic Fusion of an Anti-BclA Single-Domain Antibody with Beta Galactosidase. Antibodies (Basel) 2018; 7:antib7040036. [PMID: 31544886 PMCID: PMC6698959 DOI: 10.3390/antib7040036] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Revised: 09/26/2018] [Accepted: 09/27/2018] [Indexed: 02/06/2023] Open
Abstract
The Bacillus collagen-like protein of anthracis (BclA), found in Bacillus anthracis spores, is an attractive target for immunoassays. Previously, using phage display we had selected llama-derived single-domain antibodies that bound to B. anthracis spore proteins including BclA. Single-domain antibodies (sdAbs), the recombinantly expressed heavy domains from the unique heavy-chain-only antibodies found in camelids, provide stable and well-expressed binding elements with excellent affinity. In addition, sdAbs offer the important advantage that they can be tailored for specific applications through protein engineering. A fusion of a BclA targeting sdAb with the enzyme Beta galactosidase (β-gal) would enable highly sensitive immunoassays with no need for a secondary reagent. First, we evaluated five anti-BclA sdAbs, including four that had been previously identified but not characterized. Each was tested to determine its binding affinity, melting temperature, producibility, and ability to function as both capture and reporter in sandwich assays for BclA. The sdAb with the best combination of properties was constructed as a fusion with β-gal and shown to enable sensitive detection. This fusion has the potential to be incorporated into highly sensitive assays for the detection of anthrax spores.
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Affiliation(s)
- George P Anderson
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | - Lisa C Shriver-Lake
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | - Scott A Walper
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | - Lauryn Ashford
- The Washington Center for Internships and Academic Seminars, 1333 16th Street N.W., Washington, DC 20036, USA.
| | - Dan Zabetakis
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | - Jinny L Liu
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | - Joyce C Breger
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
| | | | - Ellen R Goldman
- Naval Research Laboratory, Center for Biomolecular Science and Engineering, Washington, DC 20375, USA.
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13
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Sharma H, John K, Gaddam A, Navalkar A, Maji SK, Agrawal A. A magnet-actuated biomimetic device for isolating biological entities in microwells. Sci Rep 2018; 8:12717. [PMID: 30143719 PMCID: PMC6109070 DOI: 10.1038/s41598-018-31274-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Accepted: 08/10/2018] [Indexed: 12/25/2022] Open
Abstract
Microwell platforms show great promise in single-cell studies and protein measurements because of their low volume sampling, rapid analysis and high throughput screening ability. However, the existing actuation mechanisms to manipulate the target samples and fabrication procedures involved in the microwell-based microfluidic devices are complex, resource-intensive and require an external power source. In this work, we present proof of concept of a simple, power-free and low-cost closed magnet digital microfluidics device for isolating biological entities in femtoliter-sized microwells. The target biological entities were encapsulated in magnetic liquid marbles and shuttled back and forth between micropatterned top and bottom plates in the microdevice to obtain high loading efficiency and short processing time. The microdevice performance was studied through fluorescent detection of three different entities: microbeads, bovine serum albumin (BSA) and Escherichia coli, captured in the microwell array. Almost 80% of the microwells were loaded with single microbeads in five shuttling cycles, in less than a minute. Further, a low volume of BSA was compartmentalized in the microwell array over a two order range of concentration. The microdevice exhibits two unique features: lotus leaf stamps were used to fabricate micropatterns (microwells and micropillars) on top and bottom plates to impart functionality and cost-effectiveness, and the target samples were actuated by a permanent magnet to make the microdevice power-free and simple in operation. The developed biomimetic microdevice is therefore capable of capturing a multitude of biological entities in low-resource settings.
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Affiliation(s)
- Himani Sharma
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Kimberley John
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Anvesh Gaddam
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Ambuja Navalkar
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Samir K Maji
- Department of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Amit Agrawal
- Department of Mechanical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India.
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14
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Ven K, Vanspauwen B, Pérez-Ruiz E, Leirs K, Decrop D, Gerstmans H, Spasic D, Lammertyn J. Target Confinement in Small Reaction Volumes Using Microfluidic Technologies: A Smart Approach for Single-Entity Detection and Analysis. ACS Sens 2018; 3:264-284. [PMID: 29363316 DOI: 10.1021/acssensors.7b00873] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Over the last decades, the study of cells, nucleic acid molecules, and proteins has evolved from ensemble measurements to so-called single-entity studies. The latter offers huge benefits, not only as biological research tools to examine heterogeneities among individual entities within a population, but also as biosensing tools for medical diagnostics, which can reach the ultimate sensitivity by detecting single targets. Whereas various techniques for single-entity detection have been reported, this review focuses on microfluidic systems that physically confine single targets in small reaction volumes. We categorize these techniques as droplet-, microchamber-, and nanostructure-based and provide an overview of their implementation for studying single cells, nucleic acids, and proteins. We furthermore reflect on the advantages and limitations of these techniques and highlight future opportunities in the field.
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Affiliation(s)
- Karen Ven
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Bram Vanspauwen
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Elena Pérez-Ruiz
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Karen Leirs
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Deborah Decrop
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Hans Gerstmans
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
- Department
of Applied biosciences, Ghent University, Valentyn Vaerwyckweg 1 - building
C, 9000 Gent, Belgium
- Department
of Biosystems, KU Leuven - University of Leuven, Kasteelpark Arenberg
21, 3001 Leuven, Belgium
| | - Dragana Spasic
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Jeroen Lammertyn
- Department
of Biosystems, KU Leuven - University of Leuven, Willem de Croylaan 42, 3001 Leuven, Belgium
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15
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Duan BK, Cavanagh PE, Li X, Walt DR. Ultrasensitive Single-Molecule Enzyme Detection and Analysis Using a Polymer Microarray. Anal Chem 2018; 90:3091-3098. [PMID: 29425025 DOI: 10.1021/acs.analchem.7b03980] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
This report describes a novel method for isolating and detecting individual enzyme molecules using polymer arrays of picoliter microwells. A fluidic flow-cell device containing an array of microwells is fabricated in cyclic olefin polymer (COP). The use of COP microwell arrays simplifies experiments by eliminating extensive device preparation and surface functionalization that are common in other microwell array formats. Using a simple and robust loading method to introduce the reaction solution, individual enzyme molecules are trapped in picoliter microwells and subsequently isolated and sealed by fluorinated oil. The sealing is stable for hours in the COP device. The picoliter microwell device can measure enzyme concentrations in the low-femtomolar range by counting the number of active wells using a digital read-out. These picoliter microwell arrays can also easily be regenerated and reused.
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Affiliation(s)
- Barrett K Duan
- Department of Pathology , Harvard Medical School , Brigham and Women's Hospital, Wyss Institute for Biologically Inspired Engineering, Building for Transformative Medicine, 60 Fenwood Road , Boston , Massachusetts 02115 , United States
| | - Peter E Cavanagh
- Department of Pathology , Harvard Medical School , Brigham and Women's Hospital, Wyss Institute for Biologically Inspired Engineering, Building for Transformative Medicine, 60 Fenwood Road , Boston , Massachusetts 02115 , United States
| | - Xiang Li
- Department of Pathology , Harvard Medical School , Brigham and Women's Hospital, Wyss Institute for Biologically Inspired Engineering, Building for Transformative Medicine, 60 Fenwood Road , Boston , Massachusetts 02115 , United States
| | - David R Walt
- Department of Pathology , Harvard Medical School , Brigham and Women's Hospital, Wyss Institute for Biologically Inspired Engineering, Building for Transformative Medicine, 60 Fenwood Road , Boston , Massachusetts 02115 , United States
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16
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Longwell CK, Labanieh L, Cochran JR. High-throughput screening technologies for enzyme engineering. Curr Opin Biotechnol 2017. [DOI: 10.1016/j.copbio.2017.05.012] [Citation(s) in RCA: 70] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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17
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Patterned surfaces for biological applications: A new platform using two dimensional structures as biomaterials. CHINESE CHEM LETT 2017. [DOI: 10.1016/j.cclet.2016.09.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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18
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Decrop D, Pardon G, Brancato L, Kil D, Zandi Shafagh R, Kokalj T, Haraldsson T, Puers R, van der Wijngaart W, Lammertyn J. Single-Step Imprinting of Femtoliter Microwell Arrays Allows Digital Bioassays with Attomolar Limit of Detection. ACS APPLIED MATERIALS & INTERFACES 2017; 9:10418-10426. [PMID: 28266828 DOI: 10.1021/acsami.6b15415] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Bead-based microwell array technology is growing as an ultrasensitive analysis tool as exemplified by the successful commercial applications from Illumina and Quanterix for nucleic acid analysis and ultrasensitive protein measurements, respectively. High-efficiency seeding of magnetic beads is key for these applications and is enhanced by hydrophilic-in-hydrophobic microwell arrays, which are unfortunately often expensive or labor-intensive to manufacture. Here, we demonstrate a new single-step manufacturing approach for imprinting cheap and disposable hydrophilic-in-hydrophobic microwell arrays suitable for digital bioassays. Imprinting of arrays with hydrophilic-in-hydrophobic microwells is made possible using an innovative surface energy replication approach by means of a hydrophobic thiol-ene polymer formulation. In this polymer, hydrophobic-moiety-containing monomers self-assemble at the hydrophobic surface of the imprinting stamp, which results in a hydrophobic replica surface after polymerization. After removing the stamp, microwells with hydrophobic walls and a hydrophilic bottom are obtained. We demonstrate that the hydrophilic-in-hydrophobic imprinted microwell arrays enable successful and efficient self-assembly of individual water droplets and seeding of magnetic beads with loading efficiencies up to 96%. We also demonstrate the suitability of the microwell arrays for the isolation and digital counting of single molecules achieving a limit of detection of 17.4 aM when performing a streptavidin-biotin binding assay as model system. Since this approach is up-scalable through reaction injection molding, we expect it will contribute substantially to the translation of ultrasensitive digital microwell array technology toward diagnostic applications.
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Affiliation(s)
- Deborah Decrop
- Department of Biosystems, KU Leuven-University of Leuven , Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Gaspard Pardon
- Department of Micro- and Nanosystems, KTH Royal Institute of Technology , Stockholm, Sweden
| | - Luigi Brancato
- Department of Electrotechnical Engineering (ESAT-MICAS), KU Leuven-University of Leuven , Kasteelpark Arenberg 10, 3001 Leuven, Belgium
| | - Dries Kil
- Department of Electrotechnical Engineering (ESAT-MICAS), KU Leuven-University of Leuven , Kasteelpark Arenberg 10, 3001 Leuven, Belgium
| | - Reza Zandi Shafagh
- Department of Micro- and Nanosystems, KTH Royal Institute of Technology , Stockholm, Sweden
| | - Tadej Kokalj
- Department of Biosystems, KU Leuven-University of Leuven , Willem de Croylaan 42, 3001 Leuven, Belgium
| | - Tommy Haraldsson
- Department of Micro- and Nanosystems, KTH Royal Institute of Technology , Stockholm, Sweden
| | - Robert Puers
- Department of Electrotechnical Engineering (ESAT-MICAS), KU Leuven-University of Leuven , Kasteelpark Arenberg 10, 3001 Leuven, Belgium
| | | | - Jeroen Lammertyn
- Department of Biosystems, KU Leuven-University of Leuven , Willem de Croylaan 42, 3001 Leuven, Belgium
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19
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Linz TH, Hampton Henley W, Michael Ramsey J. Photobleaching kinetics-based bead encoding for multiplexed bioassays. LAB ON A CHIP 2017; 17:1076-1082. [PMID: 28205650 DOI: 10.1039/c6lc01415a] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Multiplexing bead-based bioassays requires that each type of microsphere be uniquely encoded to distinguish one type from another. Microspheres are typically encoded using fluorescent dyes with different spectral properties and varying concentrations. However practical limits exist on the number of dyes that can be spectrally resolved or the number of distinguishable intensity levels with each dye. To expand the number of encoding levels, a novel method was developed that incorporates photobleaching kinetics into bead decoding, unlocking additional multiplexing levels unattainable by conventional decoding methods. To demonstrate this technique, beads were encoded with two dyes having overlapping fluorescence excitation and emission wavelengths but different photostabilities. All beads initially exhibited similar fluorescence intensities; however, following appropriate photoexposure, the less photostable dye had reduced emission intensity due to photobleaching. By comparing the original fluorescence emission intensity to that obtained after photobleaching, multiple different populations could be reliably identified. Using only a single excitation/emission band, two different initial intensity levels were optimized to produce six uniquely identifiable bead populations whereas only two could have been achieved with conventional decoding methods. Incorporation of this encoding strategy into bead-based microwell array assays significantly increases the number of encoding levels available for multiplexed assays without increasing the complexity of the imaging instrumentation.
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Affiliation(s)
- Thomas H Linz
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
| | - W Hampton Henley
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
| | - J Michael Ramsey
- Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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20
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Tang CK, Vaze A, Rusling JF. Automated 3D-printed unibody immunoarray for chemiluminescence detection of cancer biomarker proteins. LAB ON A CHIP 2017; 17:484-489. [PMID: 28067370 PMCID: PMC5317057 DOI: 10.1039/c6lc01238h] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
A low cost three-dimensional (3D) printed clear plastic microfluidic device was fabricated for fast, low cost automated protein detection. The unibody device features three reagent reservoirs, an efficient 3D network for passive mixing, and an optically transparent detection chamber housing a glass capture antibody array for measuring chemiluminescence output with a CCD camera. Sandwich type assays were built onto the glass arrays using a multi-labeled detection antibody-polyHRP (HRP = horseradish peroxidase). Total assay time was ∼30 min in a complete automated assay employing a programmable syringe pump so that the protocol required minimal operator intervention. The device was used for multiplexed detection of prostate cancer biomarker proteins prostate specific antigen (PSA) and platelet factor 4 (PF-4). Detection limits of 0.5 pg mL-1 were achieved for these proteins in diluted serum with log dynamic ranges of four orders of magnitude. Good accuracy vs. ELISA was validated by analyzing human serum samples. This prototype device holds good promise for further development as a point-of-care cancer diagnostics tool.
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Affiliation(s)
- C K Tang
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060, USA.
| | - A Vaze
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060, USA.
| | - J F Rusling
- Department of Chemistry, University of Connecticut, 55 North Eagleville Road, Storrs, Connecticut 06269-3060, USA. and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, USA and Dept. of Surgery, and Neag Cancer Center, UConn Health, 263 Farmington Av., Farmington, Connecticut 06030, USA and School of Chemistry, National University of Ireland at Galway, Ireland
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21
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Cretich M, Daaboul GG, Sola L, Ünlü MS, Chiari M. Digital detection of biomarkers assisted by nanoparticles: application to diagnostics. Trends Biotechnol 2015; 33:343-51. [DOI: 10.1016/j.tibtech.2015.03.002] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2015] [Revised: 03/12/2015] [Accepted: 03/19/2015] [Indexed: 01/09/2023]
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22
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Khanna P, Walt DR. Salivary diagnostics using a portable point-of-service platform: a review. Clin Ther 2015; 37:498-504. [PMID: 25732629 DOI: 10.1016/j.clinthera.2015.02.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 02/04/2015] [Accepted: 02/05/2015] [Indexed: 11/19/2022]
Abstract
Clinical diagnostics can be improved by faster and more accessible disease detection. Our laboratory has developed a point-of-service (POS) device capable of rapid, sensitive, automated, and multiplexed biomarker detection that uses human saliva instead of other biofluids. Here, we review the technology that led to the development of this POS device. This POS technology can advance clinical diagnostics by saving time because of faster diagnosis, saving money because of a shorter hospital stay, and ultimately improving clinical care.
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Affiliation(s)
- Prarthana Khanna
- Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111
| | - David R Walt
- Department of Chemistry, Tufts University, Medford, Massachusetts.
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23
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Falconnet D, She J, Tornay R, Leimgruber E, Bernasconi D, Lagopoulos L, Renaud P, Demierre N, van den Bogaard P. Rapid, sensitive and real-time multiplexing platform for the analysis of protein and nucleic-acid biomarkers. Anal Chem 2015; 87:1582-9. [PMID: 25567587 DOI: 10.1021/ac502741c] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We describe a multiplexing technology, named Evalution, based on novel digitally encoded microparticles in microfluidic channels. Quantitative multiplexing is becoming increasingly important for research and routine clinical diagnostics, but fast, easy-to-use, flexible and highly reproducible technologies are needed to leverage the advantages of multiplexing. The presented technology has been tailored to ensure (i) short assay times and high reproducibility thanks to reaction-limited binding regime, (ii) dynamic control of assay conditions and real-time binding monitoring allowing optimization of multiple parameters within a single assay run, (iii) compatibility with various immunoassay formats such as coflowing the samples and detection antibodies simultaneously and hence simplifying workflows, (iv) analyte quantification based on initial binding rates leading to increased system dynamic range and (v) high sensitivity via enhanced fluorescence collection. These key features are demonstrated with assays for proteins and nucleic acids showing the versatility of this technology.
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24
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Enzyme molecules in solitary confinement. Molecules 2014; 19:14417-45. [PMID: 25221867 PMCID: PMC6271441 DOI: 10.3390/molecules190914417] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2014] [Revised: 09/03/2014] [Accepted: 09/03/2014] [Indexed: 11/17/2022] Open
Abstract
Large arrays of homogeneous microwells each defining a femtoliter volume are a versatile platform for monitoring the substrate turnover of many individual enzyme molecules in parallel. The high degree of parallelization enables the analysis of a statistically representative enzyme population. Enclosing individual enzyme molecules in microwells does not require any surface immobilization step and enables the kinetic investigation of enzymes free in solution. This review describes various microwell array formats and explores their applications for the detection and investigation of single enzyme molecules. The development of new fabrication techniques and sensitive detection methods drives the field of single molecule enzymology. Here, we introduce recent progress in single enzyme molecule analysis in microwell arrays and discuss the challenges and opportunities.
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