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Proceedings of the National Academy of... Jan 2017Studying how the membrane modulates ion channel and transporter activity is challenging because cells actively regulate membrane properties, whereas existing in vitro...
Studying how the membrane modulates ion channel and transporter activity is challenging because cells actively regulate membrane properties, whereas existing in vitro systems have limitations, such as residual solvent and unphysiologically high membrane tension. Cell-sized giant unilamellar vesicles (GUVs) would be ideal for in vitro electrophysiology, but efforts to measure the membrane current of intact GUVs have been unsuccessful. In this work, two challenges for obtaining the "whole-GUV" patch-clamp configuration were identified and resolved. First, unless the patch pipette and GUV pressures are precisely matched in the GUV-attached configuration, breaking the patch membrane also ruptures the GUV. Second, GUVs shrink irreversibly because the membrane/glass adhesion creating the high-resistance seal (>1 GΩ) continuously pulls membrane into the pipette. In contrast, for cell-derived giant plasma membrane vesicles (GPMVs), breaking the patch membrane allows the GPMV contents to passivate the pipette surface, thereby dynamically blocking membrane spreading in the whole-GMPV mode. To mimic this dynamic passivation mechanism, beta-casein was encapsulated into GUVs, yielding a stable, high-resistance, whole-GUV configuration for a range of membrane compositions. Specific membrane capacitance measurements confirmed that the membranes were truly solvent-free and that membrane tension could be controlled over a physiological range. Finally, the potential for ion transport studies was tested using the model ion channel, gramicidin, and voltage-clamp fluorometry measurements were performed with a voltage-dependent fluorophore/quencher pair. Whole-GUV patch-clamping allows ion transport and other voltage-dependent processes to be studied while controlling membrane composition, tension, and shape.
PubMed: 28003462
DOI: 10.1073/pnas.1609142114 -
Journal of the Royal Society, Interface Mar 2018The female sex organ of the liverwort () has a characteristic parasol-like form highly suitable for collecting water droplets containing sperm for fertilization....
The female sex organ of the liverwort () has a characteristic parasol-like form highly suitable for collecting water droplets containing sperm for fertilization. Motivated by this observation and using three-dimensional printing techniques, we develop a parasol-like rigid object that can grab, transport and release water droplets of a maximum size of about 1 cm. By combining experiments and scaling theory, we quantify the object's fundamental wetting and fluid dynamical properties. We construct a stability phase diagram and suggest that it is largely insensitive to properties of liquids such as surface tension and viscosity. A simple scaling argument is developed to explain the phase boundary. Our study provides basic design rules of a simple pipette-like device with bubble-free capture and drop of liquids, which can be used in laboratory settings and has applications within soft robotics. Through systematic experimental investigations, we suggest the optimal design criteria of the liverwort-inspired object to achieve maximal pipetting performance. We also provide, based on our scalable model experiments, a biological implication for the mechanistic advantage of this structure in liverwort reproduction.
Topics: Biological Transport, Active; Biomimetic Materials; Hepatophyta; Ovule; Wettability
PubMed: 29540542
DOI: 10.1098/rsif.2017.0868 -
Scientific Reports Aug 2022Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample...
Cross-contamination of biological samples during handling and preparation, is a major issue in laboratory setups, leading to false-positives or false-negatives. Sample carryover residue in pipette tips contributes greatly to this issue. Most pipette tips on the market are manufactured with hydrophobic polymers that are able to repel high surface tension liquids, yet they lack in performance when low surface tension liquids and viscous fluids are involved. Moreover, hydrophobicity of pipette tips can result in hydrophobic adsorption of biomolecules, causing inaccuracies and loss in precision during pipetting. Here we propose the use of lubricant-infused surface (LIS) technology to achieve omniphobic properties in pipette tips. Using a versatile and simple design, the inner lumen of commercially available pipette tips was coated with a fluorosilane (FS) layer using chemical vapor deposition (CVD). The presence of FS groups on the tips is confirmed by x-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) tests. After lubrication of the tips through a fluorinated lubricant, the omniphobicity and repellent behaviour of the tips drastically enhanced which are revealed via static and hysteresis contact angle measurements. The repellency of the lubricant-infused pipette tips against physical adsorption is investigated through pipetting a food coloring dye as well as human blood samples and are compared to the untreated tips. The results show significantly less amount carryover residue when the lubricant-infused tips are utilized compared to commercially available ones. We also demonstrate the lubricant-infused tips reduce bacteria contamination of the inner lumen by 3 to 6-log (over 99%, depending on the tip size) after pipetting up and down the bacteria solution.
Topics: Humans; Adsorption; Hydrophobic and Hydrophilic Interactions; Lubricants; Lubrication; Surface Properties; Complex Mixtures
PubMed: 36008518
DOI: 10.1038/s41598-022-18756-x -
Sensors (Basel, Switzerland) Nov 2023A pipette-free and fully integrated device that can be used to accurately recognize the presence of infectious pathogens is an important and useful tool in point-of-care...
Pipette-Free and Fully Integrated Paper Device Employing DNA Extraction, Isothermal Amplification, and Carmoisine-Based Colorimetric Detection for Determining Infectious Pathogens.
A pipette-free and fully integrated device that can be used to accurately recognize the presence of infectious pathogens is an important and useful tool in point-of-care testing, particularly when aiming to decrease the unpredictable threats posed by disease outbreak. In this study, a paper device is developed to integrate the three main processes required for detecting infectious pathogens, including DNA extraction, loop-mediated isothermal amplification (LAMP), and detection. All key reagents, including sodium dodecyl sulfate (SDS), NaOH, LAMP reagents, and carmoisine, are placed on the paper device. The paper device is operated simply via sliding and folding without using any bulky equipment, and the results can be directly observed by the naked eye. The optimized concentrations of sodium dodecyl sulfate (SDS), sodium hydroxide (NaOH), and carmoisine were found to be 0.1%, 0.1 M, and 0.5 mg/mL, respectively. The paper device was used to detect at concentrations as low as 10 CFU/mL within 60 min. Also, spiked in milk was successfully detected using the paper device, demonstrating the feasible application in real sample analysis.
Topics: Colorimetry; Sodium Dodecyl Sulfate; Sodium Hydroxide; Nucleic Acid Amplification Techniques; DNA
PubMed: 38005500
DOI: 10.3390/s23229112 -
Neuroscience Bulletin Aug 2012Patch-clamp recording requires direct accessibility of the cell membrane to patch pipettes and allows the investigation of ion channel properties and functions in... (Review)
Review
Patch-clamp recording requires direct accessibility of the cell membrane to patch pipettes and allows the investigation of ion channel properties and functions in specific cellular compartments. The cell body and relatively thick dendrites are the most accessible compartments of a neuron, due to their large diameters and therefore great membrane surface areas. However, axons are normally inaccessible to patch pipettes because of their thin structure; thus studies of axon physiology have long been hampered by the lack of axon recording methods. Recently, a new method of patch-clamp recording has been developed, enabling direct and tight-seal recording from cortical axons. These recordings are performed at the enlarged structure (axonal bleb) formed at the cut end of an axon after slicing procedures. This method has facilitated studies of the mechanisms underlying the generation and propagation of the main output signal, the action potential, and led to the finding that cortical neurons communicate not only in action potential-mediated digital mode but also in membrane potential-dependent analog mode.
Topics: Action Potentials; Animals; Axons; Dendrites; Humans; Membrane Potentials; Neurons; Patch-Clamp Techniques
PubMed: 22833034
DOI: 10.1007/s12264-012-1247-1 -
Micromachines May 2022Programmed mini-pumps play a significant role in various fields, such as chemistry, biology, and medicine, to transport a measured volume of liquid, especially in the...
Programmed mini-pumps play a significant role in various fields, such as chemistry, biology, and medicine, to transport a measured volume of liquid, especially in the current detection of COVID-19 with PCR. In view of the cost of the current automatic pipetting pump being higher, which is difficult to use in a regular lab, this paper designed and assembled a three-dimensional programmed mini-pump with the common parts and components, such as PLC controller, motor, microinjector, etc. With the weighting calibration before and after pipetting operation, the error of the pipette in 10 μL (0.2%), 2 μL (1.8%), and 1 μL (5.6%) can be obtained. Besides, the contrast test between three-dimensional programmed mini-pump and manual pipette was conducted with the ORF1ab and pGEM-3Zf (+) genes in qPCR. The results proved that the custom-made three-dimensional programmed mini-pump has a stronger reproducibility compared with manual pipette (ORF1ab: 24.06 ± 0.33 vs. 23.50 ± 0.58, = 0.1014; pGEM-3Zf (+): 11.83.06 ± 0.24 vs. 11.50 ± 0.34, = 0.8779). These results can lay the foundation for the functional, fast, and low-cost programmed mini-pump in PCR or other applications for trace measurements.
PubMed: 35630239
DOI: 10.3390/mi13050772 -
American Journal of Physiology. Heart... Jan 2013The quest for nonoptical imaging methods that can surmount light diffraction limits resulted in the development of scanning probe microscopes. However, most of the... (Review)
Review
The quest for nonoptical imaging methods that can surmount light diffraction limits resulted in the development of scanning probe microscopes. However, most of the existing methods are not quite suitable for studying biological samples. The scanning ion conductance microscope (SICM) bridges the gap between the resolution capabilities of atomic force microscope and scanning electron microscope and functional capabilities of conventional light microscope. A nanopipette mounted on a three-axis piezo-actuator, scans a sample of interest and ion current is measured between the pipette tip and the sample. The feedback control system always keeps a certain distance between the sample and the pipette so the pipette never touches the sample. At the same time pipette movement is recorded and this generates a three-dimensional topographical image of the sample surface. SICM represents an alternative to conventional high-resolution microscopy, especially in imaging topography of live biological samples. In addition, the nanopipette probe provides a host of added modalities, for example using the same pipette and feedback control for efficient approach and seal with the cell membrane for ion channel recording. SICM can be combined in one instrument with optical and fluorescent methods and allows drawing structure-function correlations. It can also be used for precise mechanical force measurements as well as vehicle to apply pressure with precision. This can be done on living cells and tissues for prolonged periods of time without them loosing viability. The SICM is a multifunctional instrument, and it is maturing rapidly and will open even more possibilities in the near future.
Topics: Animals; Biosensing Techniques; Cell Physiological Phenomena; Equipment Design; Fluorescence Resonance Energy Transfer; Humans; Imaging, Three-Dimensional; Ion Channels; Mechanotransduction, Cellular; Membrane Potentials; Microelectrodes; Microscopy; Nanotechnology; Patch-Clamp Techniques; Receptors, G-Protein-Coupled; Second Messenger Systems
PubMed: 23086993
DOI: 10.1152/ajpheart.00499.2012 -
Lab on a Chip Apr 2012Microfluidics has emerged as a powerful laboratory toolbox for biologists, allowing manipulation and analysis of processes at a cellular and sub-cellular level, through...
Microfluidics has emerged as a powerful laboratory toolbox for biologists, allowing manipulation and analysis of processes at a cellular and sub-cellular level, through utilization of microfabricated features at size-scales relevant to that of a single cell. In the majority of microfluidic devices, sample processing and analysis occur within closed microchannels, imposing restrictions on sample preparation and use. We present an optimized non-contact open-volume microfluidic tool to overcome these and other restrictions, through the use of a hydrodynamically confined microflow pipette, serving as a multifunctional solution handling and dispensing tool. The geometries of the tool have been optimised for use in optical microscopy, with integrated solution reservoirs to reduce reagent use, contamination risks and cleaning requirements. Device performance was characterised using both epifluorescence and total internal reflection fluorescence (TIRF) microscopy, resulting in ~200 ms and ~130 ms exchange times at ~100 nm and ~30 μm distances to the surface respectively.
Topics: Animals; CHO Cells; Cricetinae; Cricetulus; Microfluidic Analytical Techniques; Solutions; Specimen Handling
PubMed: 22252460
DOI: 10.1039/c2lc20906c -
Cells Oct 2023The study of individual cell processes that occur both on their surface and inside is highly interesting for the development of new medical drugs, cytology and cell...
The study of individual cell processes that occur both on their surface and inside is highly interesting for the development of new medical drugs, cytology and cell technologies. This work presents an original technique for fabricating the silver-coated pipette and its use for the cell analysis by combination with surface-enhanced Raman spectroscopy (SERS) and scanning ion-conducting microscopy (SICM). Unlike the majority of other designs, the pipette opening in our case remains uncovered, which is important for SICM. SERS-active Ag nanoparticles on the pipette surface are formed by vacuum-thermal evaporation followed by annealing. An array of nanoparticles had a diameter on the order of 36 nm and spacing of 12 nm. A two-particle model based on Laplace equations is used to calculate a theoretical enhancement factor (EF). The surface morphology of the samples is investigated by scanning electron microscopy while SICM is used to reveal the surface topography, to evaluate Young's modulus of living cells and to control an injection of the SERS-active pipettes into them. A Raman microscope-spectrometer was used to collect characteristic SERS spectra of cells and cell components. Local Raman spectra were obtained from the cytoplasm and nucleus of the same HEK-293 cancer cell. The EF of the SERS-active pipette was 7 × 10. As a result, we demonstrate utilizing the silver-coated pipette for both the SICM study and the molecular composition analysis of cytoplasm and the nucleus of living cells by SERS. The probe localization in cells is successfully achieved.
Topics: Humans; Silver; Metal Nanoparticles; HEK293 Cells; Microscopy, Electron, Scanning; Single-Cell Analysis; Ions
PubMed: 37947599
DOI: 10.3390/cells12212521 -
Proceedings. Mathematical, Physical,... Mar 2017Along with more prevalent solid-state nanopores, glass or quartz nanopipettes have found applications in resistive-pulse and rectification sensing. Their advantages... (Review)
Review
Along with more prevalent solid-state nanopores, glass or quartz nanopipettes have found applications in resistive-pulse and rectification sensing. Their advantages include the ease of fabrication, small physical size and needle-like geometry, rendering them useful for local measurements in small spaces and delivery of nanoparticles/biomolecules. Carbon nanopipettes fabricated by depositing a thin carbon layer on the inner wall of a quartz pipette provide additional means for detecting electroactive species and fine-tuning the current rectification properties. In this paper, we discuss the fundamentals of resistive-pulse sensing with nanopipettes and our recent studies of current rectification in carbon pipettes.
PubMed: 28413354
DOI: 10.1098/rspa.2016.0931