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Liang L, Liang M, Zuo Z, Ai Y. Label-free single-cell analysis in microdroplets using a light-scattering-based optofluidic chip. Biosens Bioelectron 2024; 253:116148. [PMID: 38428071 DOI: 10.1016/j.bios.2024.116148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 02/01/2024] [Accepted: 02/19/2024] [Indexed: 03/03/2024]
Abstract
Droplet-based single-cell analysis is a very powerful tool for studying phenotypic and genomic heterogeneity at single-cell resolution for a variety of biological problems. In conventional two-phase droplet microfluidics, due to the mismatch in optical properties between oil and aqueous phases, light scattering mainly happens at the oil/water interface that disables light-scattering-based cell analysis confined in microdroplets. Detection and analysis of cells in microdroplets thus mostly rely on the fluorescence labeling of cell samples, which may suffer from complex operation, cytotoxicity, and low fluorescence stability. In this work, we propose a novel light-scattering-based droplet screening (LSDS) that can effectively detect and characterize single cells confined in droplets by adjusting the optical properties of droplets in a multiangle optofluidic chip. Theoretical and simulated calculations suggest that refractive index (RI) matching in droplet two-phase materials can reduce or eliminate droplets' scattered signals (background signal), enabling the differentiation of scattered signals from single cells and particles within droplets. Furthermore, by using a set of multiangle (from -145° to 140°) optical fibers integrated into the optofluidic chip, the scattered light properties of droplets with the RI ranging from 1.334 to 1.429 are measured. We find that the smaller the RI and size of microparticles inside droplets are, the smaller the RI difference between two-phase materials Δn is required. Especially, when Δn is smaller than 0.02, single cells in droplets can be detected and analyzed solely based on light scattering. This capability allows to accurately detect droplets containing one single cell and one single gel bead, a typical droplet encapsulation for single-cell sequencing. Altogether, this work provides a powerful platform for high-throughput label-free single-cell analysis in microdroplets for diverse single-cell related biological assays.
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Affiliation(s)
- Li Liang
- School of Physics and Electronic Information, Anhui Normal University, Wuhu, 241000, China
| | - Minhui Liang
- Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore, 487372, Singapore
| | - Zewen Zuo
- School of Physics and Electronic Information, Anhui Normal University, Wuhu, 241000, China
| | - Ye Ai
- Pillar of Engineering Product Development, Singapore University of Technology and Design, Singapore, 487372, Singapore.
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Song Y, Liang C. H-bond engineering as a general strategy for inhibiting twisted intramolecular charge transfer in donor-acceptor fluorescent probes: Reshaping the pre-twisting method. Talanta 2024; 272:125770. [PMID: 38340393 DOI: 10.1016/j.talanta.2024.125770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2023] [Revised: 02/02/2024] [Accepted: 02/06/2024] [Indexed: 02/12/2024]
Abstract
Twisted intramolecular charge transfer (TICT) is a fluorescence quenching mechanism that occurs in donor-acceptor (D‒A) molecules. Chemical engineering research into TICT regulation over the past 50 years has primarily focused on manipulating steric factors by introducing alkyl groups at the D-A junction (pre-twisting). Herein, we report a significant advance in TICT-based probes through the introducing of H-bond as an efficient strategy for suppressing TICT. Accordingly, ortho-Cl installation in the N-phenylpyrazine-2-carboxamide (PPC) platform can achieve complete reversal from the quenching mode to the light-up mode. This specific H-bonding (N-H⋯Cl) effectively blocks N-C(Ar) bond rotation, leading to fluorescence-ON. This suggested that TICT inhibition may be involved. Therefore, in a sharp contrast to the general nature of the pre-twisting method in rotor molecules, which involves incorporating steric hindrance at either the donor or acceptor moiety to enhance intramolecular rotation (promotion TICT), the ortho-H bonding strategy completely freezes D‒A bond twisting (suppression TICT), resulting in improved fluorescent intensity. Furthermore, the fluorophores were evaluated for Hg2+ detection and in vivo bio-imaging. Notably, Hg-complexation induced another fluorescence inversion (OFF-ON) by imposing spatial constraints on twisting freedom in 3,4-Cl-PPC. Taken together, this work provides a valid and generalizable tactic for the development of high-performance sensing fluorophores through inhibition of TICT.
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Affiliation(s)
- Yang Song
- College of Biology and Food, Shangqiu Normal University, Shangqiu, Henan, 476000, China; Henan Provincial Engineering Research Center for Development and Application of Characteristic Microorganism Resources, Shangqiu Normal University, Shangqiu, Henan, 476000, China.
| | - Chuan Liang
- Mental Health Education Center, Shangqiu Medical College, Shangqiu, Henan, 476000, China
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Clark JA, Robinson S, Espinoza EM, Bao D, Derr JB, Croft L, O'Mari O, Grover WH, Vullev VI. Poly(dimethylsiloxane) as a room-temperature solid solvent for photophysics and photochemistry. Phys Chem Chem Phys 2024; 26:8062-8076. [PMID: 38372740 DOI: 10.1039/d3cp05413f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Medium viscosity strongly affects the dynamics of solvated species and can drastically alter the deactivation pathways of their excited states. This study demonstrates the utility of poly(dimethylsiloxane) (PDMS) as a room-temperature solid-state medium for optical spectroscopy. As a thermoset elastic polymer, PDMS is transparent in the near ultraviolet, visible, and near infrared spectral regions. It is easy to mould into any shape, forming surfaces with a pronounced smoothness. While PDMS is broadly used for the fabrication of microfluidic devices, it swells in organic solvents, presenting severe limitations for the utility of such devices for applications employing non-aqueous fluids. Nevertheless, this swelling is reversible, which proves immensely beneficial for loading samples into the PDMS solid matrix. Transferring molecular-rotor dyes (used for staining prokaryotic cells and amyloid proteins) from non-viscous solvents into PDMS induces orders-of-magnitude enhancement of their fluorescence quantum yield and excited-state lifetimes, providing mechanistic insights about their deactivation pathways. These findings demonstrate the unexplored potential of PDMS as a solid solvent for optical applications.
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Affiliation(s)
- John A Clark
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - Samantha Robinson
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - Eli M Espinoza
- Department of Chemistry, University of California, Riverside, CA 92521, USA
| | - Duoduo Bao
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - James B Derr
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
| | - Luca Croft
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - Omar O'Mari
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - William H Grover
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
| | - Valentine I Vullev
- Department of Bioengineering, University of California, Riverside, CA 92521, USA.
- Department of Chemistry, University of California, Riverside, CA 92521, USA
- Department of Biochemistry, University of California, Riverside, CA 92521, USA
- Materials Science and Engineering Program, University of California, Riverside, CA 92521, USA
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Nan L, Zhang H, Weitz DA, Shum HC. Development and future of droplet microfluidics. LAB ON A CHIP 2024; 24:1135-1153. [PMID: 38165829 DOI: 10.1039/d3lc00729d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2024]
Abstract
Over the past two decades, advances in droplet-based microfluidics have facilitated new approaches to process and analyze samples with unprecedented levels of precision and throughput. A wide variety of applications has been inspired across multiple disciplines ranging from materials science to biology. Understanding the dynamics of droplets enables optimization of microfluidic operations and design of new techniques tailored to emerging demands. In this review, we discuss the underlying physics behind high-throughput generation and manipulation of droplets. We also summarize the applications in droplet-derived materials and droplet-based lab-on-a-chip biotechnology. In addition, we offer perspectives on future directions to realize wider use of droplet microfluidics in industrial production and biomedical analyses.
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Affiliation(s)
- Lang Nan
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
- Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong, China
| | - Huidan Zhang
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
| | - David A Weitz
- John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, 02138, USA
- Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong, China
| | - Ho Cheung Shum
- Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong, China.
- Advanced Biomedical Instrumentation Centre, Hong Kong Science Park, Shatin, New Territories, Hong Kong, China
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Panwar J, Utharala R, Fennelly L, Frenzel D, Merten CA. iSort enables automated complex microfluidic droplet sorting in an effort to democratize technology. CELL REPORTS METHODS 2023; 3:100478. [PMID: 37323570 PMCID: PMC10261925 DOI: 10.1016/j.crmeth.2023.100478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 03/24/2023] [Accepted: 04/18/2023] [Indexed: 06/17/2023]
Abstract
Fluorescence-activated droplet sorting (FADS) is a widely used microfluidic technique for high-throughput screening. However, it requires highly trained specialists to determine optimal sorting parameters, and this results in a large combinatorial space that is challenging to optimize systematically. Additionally, it is currently challenging to track every single droplet within a screen, leading to compromised sorting and "hidden" false-positive events. To overcome these limitations, we have developed a setup in which the droplet frequency, spacing, and trajectory at the sorting junction are monitored in real time using impedance analysis. The resulting data are used to continuously optimize all parameters automatically and to counteract perturbations, resulting in higher throughput, higher reproducibility, increased robustness, and a beginner-friendly character. We believe this provides a missing piece for the spreading of phenotypic single-cell analysis methods, similar to what we have seen for single-cell genomics platforms.
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Affiliation(s)
- Jatin Panwar
- Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Ramesh Utharala
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Laura Fennelly
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Daniel Frenzel
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
| | - Christoph A. Merten
- Institute of Bioengineering, School of Engineering, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
- Genome Biology Unit, European Molecular Biology Laboratory (EMBL), 69117 Heidelberg, Germany
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