Study of Oligonucleotide Fixation on Bilayer Lipid Membranes by Patch-clamp Pipette Support

One kind of novel BLMs was fabricated by patch-clamp pipette technology characterized in considerably sensitive to changes of electrochemical parameters.Detectiye currents and voltage presented linear relationship when BLMs was formed and it could be confirmed by Gramicidin method.Ion current was increased by dihexyl (C_ (12)) modified ssDNA fixed on the BLMs and also indicated linear relationship to ssDNA's concentration due to the interaction of (C_ 12)-ssDNA and BLMs.Further more,the regression equations were different from BLMs fixed with ssDNA probe and a blank control BLM in the same experimental conditions.The ssDNA probe was successfully fixed on patch-clamp pipette supported-BLMs.Based on our studies,a biosensor with reactive element of patch-clamp pipette-supported BLMs has been established.

Development of a monolithic polymer pipette for solid-phase extraction of liquiritigenin in rat plasma

A monolithic polymer column with mixed-mode interaction was prepared by in situ polymerization in a 1000μL pipette. Two kinds of monomers, butyl methacrylate （BMA） and 2-（dimethylamino）ethyl methacrylate （DMAM） were applied to constructing the mixed-mode interaction of monolithic polymer column. Its solid-phase extraction properties for liquiritigenin （LQG） were evaluated by high performance liquid chromatography （HPLC） with a gradient elution procedure. After the extraction procedure was optimized, the maximum binding capacity and extraction recovery following the optimal extraction procedure were investigated. Calibration curve was expressed as A = 65.9C ＋ 4.53 （r2 = 0.998） with a linear range of 0.151-1.80μg/mL. The experimental results indicate that the monolithic polymer pipette presents good extraction efficiency for LQG. It can be envisaged that the developed monolithic polymer pipette possesses the potential for its application to the enrichment of other flavonoids compounds being similar to the structure of LQG.

A modular single-cell pipette microfluidic chip coupling to ETAAS and ICP-MS for single cell analysis

Accurate single-cell capture is a crucial step for single cell biological and chemical analysis. Conventional single-cell capturing often confront operational complexity, limited efficiency, cell damage, large scale but low accuracy, incompetence in the acquirement of nano-upgraded single-cell liquid. Flow cytometry has been widely used in large-scale single-cell detection, while precise single-cell isolation relies on both a precision operating platform and a microscope, which is not only extremely inefficient, but also not conducive to couple with modern analytical instruments. Herein, we develop a modular single-cell pipette(m SCP) microfluidic chip with high efficiency and strong applicability for accurate direct capture of single viable cell from cell suspensions into nanoliter droplets(30-1000 n L). The m SCP is used as a sampling platform for the detection of Cd Te quantum dots in single cells with electrothermal atomic absorption spectrometry(ETAAS) for the first time. It also ensures precise single-cell sampling and detection by inductively coupled plasma mass spectrometry(ICP-MS).

Using pipette tips to readily generate spheroids comprising single or multiple cell types

Three-dimensional(3D)cell culture methods have been validated that can replicate the tumor environment in vivo to a large extent,providing an effective tool for studying tumors.In this study,we demonstrated the use of standard laboratory pipette tips as micro vessels for generating 3D cell spheroids.No microfabrication or wet-chemistry surface modifications were involved in the procedure.Spheroids consisting of single or multiple cell types were generated within 24 h just by pipetting and incubating a cell suspension in pipette tips.Scanning electron microscope and optical microscope proved that the cells grew together tightly,and suggested that while gravity force might have initiated the sedimentation of cells at the bottom of the tip,the active aggregation of cells to form tight cell-cell interactions drove the formation of spheroids.Using common laboratory micropipettes and pipette tips,the rate of spheroid generation and the generation reproducibility was characterized from five boxes each with 80 tips.The ease of transferring reagents allowed modeling of the growth of microvascular endothelial cells in tumor spheroids.Moreover,the pairing and fusion of tumor spheroids could be manipulated in the pipette tips,suggesting the potential for building and assembling heterogeneous micro-tumor tissues in vitro to mimic solid tumors in vivo.This study demonstrated that spheroids can be readily and cost-effectively generated in standard biological laboratories in a timely manner using pipette tips.

3D printing-based frugal manufacturing of glass pipettes for minimally invasive delivery of therapeutics to the brain

Objective:Intracerebral delivery of agents in liquid form is usually achieved through commercially available and durable metal needles.However,their size and texture may contribute to mechanical brain damage.Glass pipettes with a thin tip may significantly reduce injection-associated brain damage but require access to prohibitively expensive programmable pipette pullers.This study is to remove the economic barrier to the application of minimally invasive delivery of therapeutics to the brain,such as chemical compounds,viral vectors,and cells.Methods:We took advantage of the rapid development of free educational online resources and emerging low-cost 3D printers by designing an affordable pipette puller(APP)to remove the cost obstacle.Results:We showed that our APP could produce glass pipettes with a sharp tip opening down to 20μm or less,which is sufficiently thin for the delivery of therapeutics into the brain.A pipeline from pipette pulling to brain injection using low-cost and open-source equipment was established to facilitate the application of the APP.Conclusion:In the spirit of frugal science,our device may democratize glass pipette-puling and substantially promote the application of minimally invasive and precisely controlled delivery of therapeutics to the brain for finding more effective therapies of brain diseases.

Sorting Gold and Sand(Silica) Using Atomic Force Microscope-Based Dielectrophoresis

Additive manufacturing-also known as 3D printing-has attracted much attention in recent years as a powerful method for the simple and versatile fabrication of complicated three-dimensional structures.However,the current technology still exhibits a limitation in realizing the selective deposition and sorting of various materials contained in the same reservoir,which can contribute significantly to additive printing or manufacturing by enabling simultaneous sorting and deposition of different substances through a single nozzle.Here,we propose a dielectrophoresis(DEP)-based material-selective deposition and sorting technique using a pipette-based quartz tuning fork(QTF)-atomic force microscope(AFM) platform DEPQA and demonstrate multi-material sorting through a single nozzle in ambient conditions.We used Au and silica nanoparticles for sorting and obtained 95% accuracy for spatial separation,which confirmed the surfaceenhanced Raman spectroscopy(SERS).To validate the scheme,we also performed a simulation for the system and found qualitative agreement with the experimental results.The method that combines DEP,pipette-based AFM,and SERS may widely expand the unique capabilities of 3D printing and nano-micro patterning for multi-material patterning,materials sorting,and diverse advanced applications.

Convective Assembly of Linear Gold Nanoparticle Arrays at the Micron Scale for Surface Enhanced Raman Scattering

A convective assembly technique at the micron scale analogous to the writing action of a ＂pipette pen＂ has been developed for the linear assembly of gold nanoparticle strips with micron scale width and millimeter scale length for surface enhanced Raman scattering （SERS）. The arrays with interparticle gaps smaller than 3 nm are hexagonally stacked in the vicinity of the pipette tip. Variable numbers of stacked layers and clean surfaces of the assembled nanoparticles are obtained by optimizing the velocity of the pipette tip. The SERS properties of tile assembled nanoparticle arrays rely on their stacking number and surface cleanliness.

Probing non-polarizable liquid/liquid interfaces using scanning ion conductance microscopy

The study of microscopic structure of a liquid/liquid interface is of fundamental importance due to its close relation to the thermodynamics and kinetics of interfacial charge transfer reactions.In this article,the microscopic structure of a non-polarizable water/nitrobenzene(W/NB)interface was evaluated by scanning ion conductance microscope(SICM).Using SICM with a nanometer-sized quartz pipette filled with an electrolyte solution as the probe,the thickness of this type of W/NB interface could be measured at sub-nanometer scale,based on the continuous change of ionic current from one phase to another one.The effects for thicknesses of the non-polarizable W/NB interfaces with different electrolyte concentrations,the Galvani potentials at the interface and the applied potentials on the probe were measured and systematically analyzed.Both experimental setups,that is an organic phase up and an aqueous down,and a reverse version,were employed to acquire the approach curves.These data were compared with those of an ideal polarizable interface under the similar experimental conditions,and several characteristics of non-polarizable interfaces were found.The thickness of a non-polarizable interface increases with the decrease of electrolyte concentration and the increase of applied potential,which is similar to the situation of a polarizable liquid/liquid interface.We also find that the Galvani potential across a non-polarizable interface can also influence the interfacial thickness,this phenomenon is difficult to observe when using polarizable interface.Most importantly,by the comparison of two kinds of liquid/liquid interfaces,we experimentally proved that much more excess ions are gathered in the space charge layer of non-polarizable interfaces than in that of polarizable interfaces.These results are consistent with the predictions of molecular dynamic simulations and X-ray reflectivity measurements.