scholarly journals Sorting by interfacial tension (SIFT): Label-free enzyme sorting using droplet microfluidics

2019 ◽  
Vol 1089 ◽  
pp. 108-114 ◽  
Author(s):  
Daniel G. Horvath ◽  
Samuel Braza ◽  
Trevor Moore ◽  
Ching W. Pan ◽  
Lailai Zhu ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Droplet Microfluidics ◽  
Free Enzyme ◽  
Label Free

scholarly journals Interfacial Tension Measurements in Microfluidic Quasi-Static Extensional Flows

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 272
Author(s):  
Doojin Lee ◽  
Amy Q. Shen
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Device ◽  
Extensional Flow ◽  
Immiscible Fluids ◽  
Droplet Microfluidics ◽  
Channel Height ◽  
Deformation Model ◽  
Droplet Deformation ◽  
Extensional Flows ◽  
2D Model

Droplet microfluidics provides a versatile tool for measuring interfacial tensions between two immiscible fluids owing to its abilities of fast response, enhanced throughput, portability and easy manipulations of fluid compositions, comparing to conventional techniques. Purely homogeneous extension in the microfluidic device is desirable to measure the interfacial tension because the flow field enables symmetric droplet deformation along the outflow direction. To do so, we designed a microfluidic device consisting of a droplet production region to first generate emulsion droplets at a flow-focusing area. The droplets are then trapped at a stagnation point in the cross junction area, subsequently being stretched along the outflow direction under the extensional flow. These droplets in the device are either confined or unconfined in the channel walls depending on the channel height, which yields different droplet deformations. To calculate the interfacial tension for confined and unconfined droplet cases, quasi-static 2D Darcy approximation model and quasi-static 3D small deformation model are used. For the confined droplet case under the extensional flow, an effective viscosity of the two immiscible fluids, accounting for the viscosity ratio of continuous and dispersed phases, captures the droplet deformation well. However, the 2D model is limited to the case where the droplet is confined in the channel walls and deforms two-dimensionally. For the unconfined droplet case, the 3D model provides more robust estimates than the 2D model. We demonstrate that both 2D and 3D models provide good interfacial tension measurements under quasi-static extensional flows in comparison with the conventional pendant drop method.

scholarly journals Evaporation-induced stimulation of bacterial osmoregulation for electrical assessment of cell viability

2016 ◽  
Vol 113 (26) ◽  
pp. 7059-7064 ◽  
Author(s):  
Aida Ebrahimi ◽  
Muhammad Ashraful Alam
Keyword(s):  
Cell Viability ◽  
Osmotic Pressure ◽  
Electrical Conductance ◽  
Ionic Concentration ◽  
Droplet Microfluidics ◽  
Cell Multiplication ◽  
Bacterial Cells ◽  
Label Free ◽  
The Road ◽  
Viability Assay

Bacteria cells use osmoregulatory proteins as emergency valves to respond to changes in the osmotic pressure of their external environment. The existence of these emergency valves has been known since the 1960s, but they have never been used as the basis of a viability assay to tell dead bacteria cells apart from live ones. In this paper, we show that osmoregulation provides a much faster, label-free assessment of cell viability compared with traditional approaches that rely on cell multiplication (growth) to reach a detectable threshold. The cells are confined in an evaporating droplet that serves as a dynamic microenvironment. Evaporation-induced increase in ionic concentration is reflected in a proportional increase of the droplet’s osmotic pressure, which in turn, stimulates the osmoregulatory response from the cells. By monitoring the time-varying electrical conductance of evaporating droplets, bacterial cells are identified within a few minutes compared with several hours in growth-based methods. To show the versatility of the proposed method, we show detection of WT and genetically modified nonhalotolerant cells (Salmonella typhimurium) and dead vs. live differentiation of nonhalotolerant (such as Escherichia coli DH5α) and halotolerant cells (such as Staphylococcus epidermidis). Unlike the growth-based techniques, the assay time of the proposed method is independent of cell concentration or the bacteria type. The proposed label-free approach paves the road toward realization of a new class of real time, array-formatted electrical sensors compatible with droplet microfluidics for laboratory on a chip applications.

scholarly journals Mechanism of biosurfactant adsorption to oil/water interfaces from millisecond scale tensiometry measurements

2017 ◽  
Vol 7 (6) ◽  
pp. 20170013 ◽  
Author(s):  
Lingling Kong ◽  
Kadi Liis Saar ◽  
Raphael Jacquat ◽  
Liu Hong ◽  
Aviad Levin ◽  
...  
Keyword(s):  
Interfacial Tension ◽  
Microfluidic Channel ◽  
Industrial Applications ◽  
Droplet Microfluidics ◽  
Kinetic Measurements ◽  
Alkyl Benzene Sulfonate ◽  
Cyclic Lipopeptide ◽  
Ability To Act ◽  
Adsorption Processes ◽  
Order Of Magnitude

Many biological molecules are by their nature amphiphilic and have the ability to act as surfactants, stabilizing interfaces between aqueous and immiscible oil phases. In this paper, we explore the adsorption kinetics of surfactin, a naturally occurring cyclic lipopeptide, at hexadecane/water interfaces and compare and contrast its adsorption behaviour with that of synthetic alkyl benzene sulfonate isomers, through direct measurements of changes in interfacial tension upon surfactant adsorption. We access millisecond time resolution in kinetic measurements by making use of droplet microfluidics to probe the interfacial tension of hexadecane droplets dispersed in a continuous water phase through monitoring their deformation when the droplets are exposed to shear flows in a microfluidic channel with regular corrugations. Our results reveal that surfactin rapidly adsorbs to the interface, thus the interfacial tension equilibrates within 300 ms, while the synthetic surfactants used undergo adsorption processes at an approximately one order of magnitude longer timescale. The approach presented may provide opportunities for understanding and modulating the adsorption mechanism of amphiphiles on a variety of interfaces in the context of life sciences and industrial applications.

scholarly journals Quantum capacitance-limited MoS2 biosensors enable remote label-free enzyme measurements

Nanoscale ◽  
2019 ◽  
Vol 11 (33) ◽  
pp. 15622-15632 ◽  
Author(s):  
Son T. Le ◽  
Nicholas B. Guros ◽  
Robert C. Bruce ◽  
Antonio Cardone ◽  
Niranjana D. Amin ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Field Effect ◽  
Field Effect Transistors ◽  
Free Enzyme ◽  
Quantum Capacitance ◽  
Label Free

Atomically thin, quantum capacitance limited, field-effect transistors, enable measurements of biological enzymes implicated in Alzheimer's disease with unprecedented resolution.

scholarly journals Two-photon fluorescence lifetime for label-free microfluidic droplet sorting

2021 ◽  
Author(s):  
Sadat Hasan ◽  
Maximilian E. Blaha ◽  
Sebastian K. Piendl ◽  
Anish Das ◽  
David Geissler ◽  
...  
Keyword(s):  
Fluorescence Lifetime ◽  
Single Photon ◽  
Photon Counting ◽  
Droplet Microfluidics ◽  
Label Free ◽  
Single Photon Counting ◽  
Two Photon ◽  
Deep Uv ◽  
Droplet Sorting ◽  
532 Nm

AbstractMicrofluidic droplet sorting systems facilitate automated selective micromanipulation of compartmentalized micro- and nano-entities in a fluidic stream. Current state-of-the-art droplet sorting systems mainly rely on fluorescence detection in the visible range with the drawback that pre-labeling steps are required. This limits the application range significantly, and there is a high demand for alternative, label-free methods. Therefore, we introduce time-resolved two-photon excitation (TPE) fluorescence detection with excitation at 532 nm as a detection technique in droplet microfluidics. This enables label-free in-droplet detection of small aromatic compounds that only absorb in a deep-UV spectral region. Applying time-correlated single-photon counting, compounds with similar emission spectra can be distinguished due to their fluorescence lifetimes. This information is then used to trigger downstream dielectrophoretic droplet sorting. In this proof-of-concept study, we developed a polydimethylsiloxane-fused silica (FS) hybrid chip that simultaneously provides a very high optical transparency in the deep-UV range and suitable surface properties for droplet microfluidics. The herein developed system incorporating a 532-nm picosecond laser, time-correlated single-photon counting (TCSPC), and a chip-integrated dielectrophoretic pulsed actuator was exemplarily applied to sort droplets containing serotonin or propranolol. Furthermore, yeast cells were screened using the presented platform to show its applicability to study cells based on their protein autofluorescence via TPE fluorescence lifetime at 532 nm. Graphical abstract

Label-free and enzyme-free detection of microRNA based on a hybridization chain reaction with hemin/G-quadruplex enzymatic catalysis-induced MoS2 quantum dots via the inner filter effect

Nanoscale ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 808-814 ◽  
Author(s):  
Jia Ge ◽  
Zhangyu Qi ◽  
Liangliang Zhang ◽  
Xueping Shen ◽  
Yanmei Shen ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Enzymatic Catalysis ◽  
Inner Filter Effect ◽  
Free Enzyme ◽  
Hybridization Chain Reaction ◽  
Label Free ◽  
Chain Reaction ◽  
Specific Strategy ◽  
Filter Effect ◽  
G Quadruplex

A new label-free, enzyme-free, and specific strategy for the assay of microRNA has been developed based on a hybridization chain reaction with hemin/G-quadruplex enzymatic catalysis-induced MoS2 quantum dots via the inner filter effect.

scholarly journals Coupling Droplet Microfluidics with Mass Spectrometry for Ultrahigh-Throughput Analysis up to and Above 30Hz.

2020 ◽  
Author(s):  
Emily Kempa ◽  
Clive Smith ◽  
Xin Li ◽  
bruno bellina ◽  
Keith Richardson ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Small Molecules ◽  
Egg White ◽  
Droplet Microfluidics ◽  
Industrial Biotechnology ◽  
Proof Of Concept ◽  
Label Free ◽  
Sample Analysis ◽  
Mass Spectrometers ◽  
Free Sample

High and ultra-high-throughput label-free sample analysis is required by many applications, extending from environ-mental monitoring to drug discovery and industrial biotechnology. HTS methods predominantly are based on a targeted workflow, which can limit their scope. Mass spectrometry readily provides chemical identity and abundance for complex mixtures and here, we use microdroplet generation microfluidics to supply picolitre aliquots for analysis at rates up to and including 33 Hz. This is demon-strated for small molecules, peptides and proteins up to 66 kDa on three commercially available mass spectrometers from salty solutions to mimic cellular environments. Designs for chip-based interfaces that permit this coupling are presented and the merits and challenges of these interfaces are discussed. On an Orbitrap platform droplet infusion rates of 6 Hz are used for the analysis of cytochrome c, on a DTIMS Q-TOF similar rates were obtained and on a TWIMS Q-TOF utilizing IM-MS software rates up to 33 Hz are demonstrated. The potential of this approach is demonstrated with proof of concept experiments on crude mixtures including egg white, unpurified recombinant protein and a biotransformation supernatant.

scholarly journals Label-Free Enzyme Activity Measurements with Quantum-Limited Biosensors

2019 ◽  
Vol 116 (3) ◽  
pp. 146a
Author(s):  
Arvind Balijepalli ◽  
Son T. Le ◽  
Nicholas B. Guros ◽  
Antonio Cardone ◽  
Niranjana D. Amin ◽  
...  
Keyword(s):  
Enzyme Activity ◽  
Free Enzyme ◽  
Label Free ◽  
Activity Measurements
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