Qiao Lin

Columbia University, New York, New York, United States

Are you Qiao Lin?

Claim your profile

Publications (150)228.93 Total impact

  • Bin Wang · Yuan Jia · Qiao Lin
    [Show abstract] [Hide abstract]
    ABSTRACT: Isothermal titration calorimetry (ITC) directly measures heat evolved in a chemical reaction to determine equilibrium binding properties of biomolecular systems. Conventional ITC instruments are expensive, use complicated design and construction, and require long analysis times. Microfabricated calorimetric devices are promising, although they have yet to allow accurate, quantitative ITC measurements of biochemical reactions. This paper presents a microfabrication-based approach to integrated, quantitative ITC characterization of biomolecular interactions. The approach integrates microfabricated differential calorimetric sensors with microfluidic titration. Biomolecules and reagents are introduced at each of a series of molar ratios, mixed, and allowed to react. The reaction thermal power is differentially measured, and used to determine the thermodynamic profile of the biomolecular interactions. Implemented in a microdevice featuring thermally isolated, well-defined reaction volumes with minimized fluid evaporation as well as highly sensitive thermoelectric sensing, the approach enables accurate and quantitative ITC measurements of protein-ligand interactions under different isothermal conditions. Using the approach, we demonstrate ITC characterization of the binding of 18-Crown-6 with barium chloride, and the binding of ribonuclease A with cytidine 2'-monophosphate within reaction volumes of approximately 0.7µL and at concentrations down to 2mM. For each binding system, the ITC measurements were completed with considerably reduced analysis times and material consumption, and yielded a complete thermodynamic profile of the molecular interaction in agreement with published data. This demonstrates the potential usefulness of our approach for biomolecular characterization in biomedical applications.
    No preview · Article · Dec 2015 · Biosensors & Bioelectronics
  • [Show abstract] [Hide abstract]
    ABSTRACT: The ability to correlate single-cell genetic information with cellular phenotypes is of great importance to biology and medicine, as it holds the potential to gain insight into disease pathways that is unavailable from ensemble measurements. We present a microfluidic approach to parallelized, rapid, quantitative analysis of messenger RNA from single cells via RT-qPCR. The approach leverages an array of single-cell RT-qPCR analysis units formed by a set of parallel microchannels concurrently controlled by elastomeric pneumatic valves, thereby enabling parallelized handling and processing of single cells in a drastically simplified operation procedure using a relatively small number of microvalves. All steps for single-cell RT-qPCR, including cell isolation and immobilization, cell lysis, mRNA purification, reverse transcription and qPCR, are integrated on a single chip, eliminating the need for off-chip manual cell and reagent transfer and qPCR amplification as commonly used in existing approaches. Additionally, the approach incorporates optically transparent microfluidic components to allow monitoring of single-cell trapping without the need for molecular labeling that can potentially alter the targeted gene expression and utilizes a polycarbonate film as a barrier against evaporation to minimize the loss of reagents at elevated temperatures during the analysis. We demonstrate the utility of the approach by the transcriptional profiling for the induction of the cyclin-dependent kinase inhibitor 1a and the glyceraldehyde 3-phosphate dehydrogenase in single cells from the MCF-7 breast cancer cell line. Furthermore, the methyl methanesulfonate is employed to allow measurement of the expression of the genes in individual cells responding to a genotoxic stress.
    No preview · Article · Oct 2015 · Microfluidics and Nanofluidics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Surface-enhanced Raman spectroscopy (SERS) based on nanostructured platforms is a promising technique for quantitative and highly sensitive detection of biomolecules in the field of analytical biochemistry. Here, we report a mathematical model to predict experimental SERS signal (or hotspot) intensity distributions of target molecules on receptor-functionalized nanopillar substrates for biomolecular quantification. We demonstrate that by utilizing only a small set of empirically determined parameters, our general theoretical framework agrees with the experimental data particularly well in the picomolar concentration regimes. This developed model may be generally used for biomolecular quantification using Raman mapping on SERS substrates with planar geometries, in which the hotspots are approximated as electromagnetic enhancement fields generated by closely spaced dimers. Lastly, we also show that the detection limit of a specific target molecule, TAMRA-labeled vasopressin, approaches the single molecule level, thus opening up an exciting new chapter in the field of SERS quantification.
    Full-text · Article · Oct 2015 · RSC Advances
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an aptameric graphene nanosensor for detection of small-molecule biomarkers. To address difficulties in direct detection of small molecules associated with their low molecular weight and electrical charge, we incorporate an aptamer-based competitive affinity assay in a graphene field effect transistor (FET), and demonstrate the utility of the nanosensor with dehydroepiandrosterone sulfate (DHEA-S), a small-molecule steroid hormone, as the target analyte. In the competitive affinity assay, DHEA-S specifically binds to aptamer molecules pre-hybridized to their complementary DNA anchor molecules immobilized on the graphene surface. This results in the competitive release of the strongly charged aptamer from the DNA anchor and hence a change in electrical properties of the graphene, which can be measured to achieve the detection of DHEA-S. We present experimental data on the label-free, specific and quantitative detection of DHEA-S at clinically appropriate concentrations with an estimated detection limit of 44.7nM, and analyze the trend observed in the experiments using molecular binding kinetics theory. These results demonstrate the potential of our nanosensor in the detection of DHEA-S and other small molecules in biomedical applications. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Sep 2015 · Biosensors & Bioelectronics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper describes an aptamer-based optomagnetic biosensor for detection of a small molecule based on target binding-induced inhibition of magnetic nanoparticle (MNP) clustering. For the detection of a target small molecule, two mutually exclusive binding reactions (aptamer-target binding and aptamer-DNA linker hybridization) are designed. An aptamer specific to the target and a DNA linker complementary to a part of the aptamer sequence are immobilized onto separate MNPs. Hybridization of the DNA linker and the aptamer induces formation of MNP clusters. The target-to-aptamer binding on MNPs prior to the addition of linker-functionalized MNPs significantly hinders the hybridization reaction, thus reducing the degree of MNP clustering. The clustering state, which is thus related to the target concentration, is then quantitatively determined by an optomagnetic readout technique that provides the hydrodynamic size distribution of MNPs and their clusters. A commercial Blu-ray optical pickup unit is used for optical signal acquisition, which enables the establishment of a low-cost and miniaturized biosensing platform. Experimental results show that the degree of MNP clustering correlates well with the concentration of a target small molecule, adenosine triphosphate (ATP) in this work, in the range between 10µM and 10mM. This successful proof-of-concept indicates that our optomagnetic aptasensor can be further developed as a low-cost biosensing platform for detection of small molecule biomarkers in an out-of-lab setting.
    Full-text · Article · Aug 2015 · Biosensors & Bioelectronics
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Affinity glucose sensors based on equilibrium binding can offer improved stability and accuracy for continuous glucose monitoring in diabetes care. This paper presents a graphene-based affinity nanosensor for glucose measurements. The nanosensor exploits the affinity binding of a novel, surface-immobilized synthetic polymer with glucose. The binding induces changes in the bulk electrical properties of graphene, which are measured for sensitive glucose detection in a highly miniaturized device without the use of physical barriers commonly employed by existing affinity glucose sensors.
    Full-text · Conference Paper · Jun 2015
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a microfluidic chip capable of isolating thermally sensitive protein-binding aptamer candidates. The chip makes use of bead-immobilized target molecules and DNA (deoxyribonucleic acid) sequences to enable a simplified chip design, in which affinity selection and PCR (polymerase chain reaction) amplification of target-binding sequences occur in temperature-controlled microchambers. Using pressure-driven flow, buffer containing single-stranded DNA molecules with randomized sequences is cycled through a series of affinity selection and PCR amplification steps on microbeads. Successive introduction of the sample to each chamber effects a process of competition whereby DNA strands with weak binding strength to target molecules are rejected in favor of strongly binding sequences. Using bead-based PCR, the amplification step was miniaturized and integrated with affinity selection, resulting in significant reductions in process time and reagent use. As a demonstration, temperature-dependent selection and amplification of single-stranded oligonucleotides that bind to human Immunoglobulin E (IgE) was performed in 4 h, a 20-fold reduction in process time as compared to conventional methods that would require approximately a week. Fluorescent binding assays then demonstrated that the desired temperature specificity was imparted to the aptamer candidates within just one round of selection, and within two rounds the aptamer candidates exhibited enhanced affinity toward IgE.
    No preview · Article · Jun 2015 · Microfluidics and Nanofluidics
  • [Show abstract] [Hide abstract]
    ABSTRACT: Gene expression analysis at the single-cell level is critical to understanding variations among cells in heterogeneous populations. Microfluidic reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) is well suited to gene expression assays of single cells. We present a microfluidic approach that integrates all functional steps for RT-qPCR of a single cell, including isolation and lysis of the cell, as well as purification, reverse transcription and quantitative real-time PCR of messenger RNA in the cell lysate. In this approach, all reactions in the multi-step assay of a single lysed cell can be completed on microbeads, thereby simplifying the design, fabrication and operation of the microfluidic device, as well as facilitating the minimization of sample loss or contamination. In the microfluidic device, a single cell is isolated and lysed; mRNA in the cell lysate is then analyzed by RT-qPCR using primers immobilized on microbeads in a single microchamber whose temperature is controlled in closed loop via an integrated heater and temperature sensor. The utility of the approach was demonstrated by the analysis of the effects of the drug (methyl methanesulfonate, MMS) on the induction of the cyclin-dependent kinase inhibitor 1a (CDKN1A) in single human cancer cells (MCF-7), demonstrating the potential of our approach for efficient, integrated single-cell RT-qPCR for gene expression analysis.
    No preview · Article · Apr 2015 · RSC Advances
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This letter presents a graphene field effect transistor (GFET) nanosensor that, with a solid gate provided by a high-κ dielectric, allows analyte detection in liquid media at low gate voltages. The gate is embedded within the sensor and thus is isolated from a sample solution, offering a high level of integration and miniaturization and eliminating errors caused by the liquid disturbance, desirable for both in vitro and in vivo applications. We demonstrate that the GFET nanosensor can be used to measure pH changes in a range of 5.3–9.3. Based on the experimental observations and quantitative analysis, the charging of an electrical double layer capacitor is found to be the major mechanism of pH sensing.
    Full-text · Article · Mar 2015 · Applied Physics Letters
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We here present a microfluidic aptasensor that integrates aptamer-based selective analyte enrichment, isocratic elution and conductance-based graphene nanosensing, achieving sensitive and label-free detection of small biomolecules. An aptamer specific to a target analyte is immobilized on microbeads for selective enrichment and isocratic elution of the analyte. A conductance-based graphene nanosensor using a competitive assay format achieves label-free detection, with a high sensitivity due to surface binding-induced changes in carrier concentration in the bulk of graphene. Experimental results show that our integrated device is capable of detecting arginine vasopressin (AVP), a small peptide, at clinically relevant low concentrations (1–500 pM).
    Full-text · Conference Paper · Jan 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We here present a microfluidic aptasensor that integrates aptamer-based selective analyte enrichment, isocratic elution and conductance-based graphene nanosensing, achieving sensitive and label-free detection of small biomolecules. An aptamer specific to a target analyte is immobilized on microbeads for selective enrichment and isocratic elution of the analyte. A conductance-based graphene nanosensor using a competitive assay format achieves label-free detection, with a high sensitivity due to surface binding-induced changes in carrier concentration in the bulk of graphene. Experimental results show that our integrated device is capable of detecting arginine vasopressin (AVP), a small peptide, at clinically relevant low concentrations (1–500 pM).
    Full-text · Conference Paper · Jan 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a graphene field effect transistor (GFET) nanosensor that, with a solid gate provided by a high-κ dielectric, allows analyte detection in liquid media at low gate voltages. The gate is embedded within the sensor and thus is isolated from a sample solution, offering a high level of integration and miniaturization and eliminating errors caused by the liquid disturbance, desirable for both in vitro and in vivo applications. We demonstrate that the GFET nanosensor can be used to measure pH changes in a range of 5.3–9.3. Based on the experimental observations and quantitative analysis, the charging of an electrical double layer capacitor is found to be the major mechanism of pH sensing.
    Full-text · Conference Paper · Jan 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this work, we present for the first time a centrifugal microfluidic system for the detection of analytes in blood using a low cost (< 10$) blu-ray pickup head for detection. The microfluidic operations are carried out on a disk, while the detection method is based on optical measurements of the rotation dynamics of functionalized magnetic nanobeads (MNBs) in an oscillating uniaxial magnetic field. INTRODUCTION There is a need for low-cost and fast methods at the point of care level (POC) to quantify the pres-ence of multiple analytes directly from a patient sample. Several technologies have been proposed in re-cent years, but, in many cases the need for state of the art readout methods, complex microfludics and high-end sensors or optics inevitably limits their real commercialization potential. Here we present a novel diagnostic technology based on the integration of a homogeneus immuno-assay based on the use of magnetic nanoparticles (MNPs) with centrifugal microfluidics. The sensing technique, based on the previously presented magneto-optical method[1] is sensitive to the presence of clustered particles in the sample which is related to the target concentration. A Blu-ray optical pickup unit (OPU) is used as a single excitation and sensing element. The technology holds great commercial potential as the basic technological elements – Blu-ray OPU and microfluidic disks – are already mass-produced. In addition, different types of assay can be implemented over multiple chambers using the same magneto-optical readout method[1]. EXPERIMENTAL Figure 1 shows the set-up configuration, where a Sony Blu-ray pickup head (the same as in the Playstation 3) is used as a laser source (=405nm) and as a detector, as the light beam is reflected back by a mirror. The blood (15L) is inserted in the disk, as shown in panel (a) and is separated into plasma, which is mixed with MNPs (30 L, 0.2 mg/mL) functionalized with antibodies specific for the target an-tigen. The disks were manufactured in Poly(methyl methacrylate) (PMMA) and bonded using pressure sensitive adhesive (PSA). The magneto-optical signal is measured in the final reservoir after a magnetic incubation step. This reservoir is placed between two electromagnets (see panel (b)), which are used to generate a sinusoidal uniaxial magnetic field parallel to the laser beam direction. The magnetic field has a fixed amplitude B 0 = 2 mT at a frequency f up to 10 kHz. For the magneto-optical measurements[1] the beam is reflected on an adjustable mirror and directed back through the reservoir to the four quadrant photo detector after passing the beam splitter of the OPU. A customized circuit is used to extract and pre-amplify the signal sum of the four quadrants. Under magnetic actuation, the collective behavior of the particles modulates the light transmission measured by the photodetector. By extracting with a software the intensity of the 2 nd harmonic signal from the photo detector and its phase lag with respect to the mag-netic field excitation at different frequencies the dynamic rotation of the MNPs is characterized. 978-0-9798064-7-6/µTAS 2014/$20©14CBMS-0001 2044 18th International Conference on Miniaturized
    Full-text · Conference Paper · Oct 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: Controlled manipulation, such as isolation, positioning and trapping of cells, is important in basic biological research and clinical diagnostics. Micro/nanotechnologies have been enabling more effective and efficient cell trapping than possible with conventional platforms. Currently available micro/nanoscale methods for cell trapping, however, still lack flexibility in precisely controlling the number of trapped cells. We exploited the large compliance of elastomers to create an array of cell-trapping microstructures, whose dimensions can be mechanically modulated by inducing uniformly distributed strain via application of external force on the chip. The device consists of two elastomer polydimethylsiloxane (PDMS) sheets, one of which bears dam-like, cup-shaped geometries to physically capture cells. The mechanical modulation is used to tune the characteristics of cell trapping to capture a predetermined number of cells, from single cells to multiple cells. Thus, enhanced utility and flexibility for practical applications can be attained, as demonstrated by tunable trapping of MCF-7 cells, a human breast cancer cell line.
    No preview · Article · Aug 2014 · Sensors and Actuators A Physical
  • Yuan Jia · Bin Wang · Jing Zhu · Qiao Lin
    [Show abstract] [Hide abstract]
    ABSTRACT: We present a flexible, polymer based MEMS differential scanning calorimetric (DSC) device combining integrated microfluidic channels, highly sensitive thermoelectric sensing, and real-time temperature monitoring for thermodynamic characterization of biomolecular samples with minimized sample consumption. The device uses an inexpensive, commercially available polymer substrate and a novel fabrication approach to create a microstructure consisting of a pair of microchannels (containing the sample and reference buffer, respectively), which are integrated with resistive temperature sensors (for in-situ measurement of sample temperature) and an antimony-bismuth (Sb-Bi) thermopile (for measurement of the temperature difference between the sample and reference channels). We demonstrate the utility of this MEMS DSC device by measuring the unfolding of lysozyme in a small volume (1 μL), and at practically relevant protein concentrations (approaching 1 mg/mL). Thermodynamic properties including the total enthalpy change per mole of protein (ΔH) and melting temperature (Tm) at different protein concentrations during this conformational transition are determined and found to agree with published data.
    No preview · Conference Paper · Jul 2014
  • Junhui Ni · Bin Wang · Stanley Chang · Qiao Lin
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an integrated magnetic micropump that uses in-plane compliance-based check valves and a magnetically actuated membrane. The device, which allows for simple fabrication and system integration with other functional elements, consists of two functional layers both fabricated from poly(dimethylsiloxane) (PDMS). The upper PDMS layer provides a compliant membrane with an electroplated thin-film permalloy strip for actuation, while the lower PDMS layer incorporates microfluidic components including the microchannels, pump chamber, and a pair of check valves for flow regulation. The PDMS check valves, each having a compliant flap in contact with a stiff stopper to allow for unidirectional fluid flow with minimized leakage, are located at the inlet and outlet of the pump chamber, respectively. As such, the unidirectional flow at a controlled volumetric rate can be readily generated in accordance with the pumping actions. Systematic characterization of the micropump has been performed by studying the dependence of its pumping flow rate on the driving frequency of magnetic actuation, and the back pressure. Experimental results show that this micropump is capable of generating fluid flow of 0.15 μL/min at the frequency of 2 Hz, corresponding to a volume resolution of 1 nL per stroke, and working reliably against a maximum back-pressure of 550 Pa, demonstrating the potential application of this micropump for various integrated lab-on-a-chip systems.
    No preview · Article · Apr 2014 · Microelectronic Engineering
  • [Show abstract] [Hide abstract]
    ABSTRACT: Isolation of cells from heterogeneous biological samples is critical in both basic biological research and clinical diagnostics. Affinity-based methods, such as those that recognise cells by binding antibodies to cell membrane biomarkers, can be used to achieve specific cell isolation. Microfluidic techniques have been employed to achieve more efficient and effective cell isolation. By employing aptamers as surface-immobilised ligands, cells can be easily released and collected after specific capture. However, these methods still have limitations in cell release efficiency and spatial selectivity. This study presents an aptamer-based microfluidic device that not only achieves specific affinity cell capture, but also enables spatially selective temperature-mediated release and retrieval of cells without detectable damage. The specific cell capture is realised by using surface-patterned aptamers in a microchamber on a temperature-control chip. Spatially selective cell release is achieved by utilising a group of microheater and temperature sensor that restricts temperature changes, and therefore the disruption of cell-aptamer interactions, to a design-specified region. Experimental results with CCRF-CEM cells and sgc8c aptamers have demonstrated the specific cell capture and temperature-mediated release of selected groups of cells with negligible disruption to their viability.
    No preview · Article · Mar 2014 · IET Nanobiotechnology
  • Yao Zhou · Qiao Lin
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a class of novel microfluidic concentration gradient generation (CGG) devices that create temporally stable chemical concentration gradients with complex shapes in a flow-free environment. The devices feature a two-layer channel design and the incorporation of a semipermeable membrane, which effectively segregates the concentration gradient region in the lower layer from the flow of reagent sample (simply “sample” onward) and buffer in the upper layer. In the mean time, free diffusion across the membrane constantly replenishes sample and buffer to maintain a stable concentration. The shapes of the concentration gradients are controlled by the geometries of the micro-channels and chambers. Concentration gradients with complex shapes can be achieved by piecewise combining constituent gradients with elementary shapes. Capable of generating concentration gradients in a flow-free environment, our devices eliminate undesirable flow stimulation on biological cells under investigation, while maintaining a stable chemical environment for cell studies.
    No preview · Article · Jan 2014 · Sensors and Actuators B Chemical
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents an aptamer-based graphene nanosensor capable of detecting small molecules. To address difficulties in direct detection of small molecules associated with their low electric charges, we use a competitive sensing approach as demonstrated with dehydroepiandrosterone sulfate (DHEA-S) as a target analyte, which is a small molecular steroid hormone with important applications in clinical diagnostics. A DHEA-S aptamer is captured by a complementary short DNA probe immobilized on the graphene and released upon exposure to DHEA-S in solution due to the binding between DHEA-S and the aptamer. The aptamer release is detected by measuring the change in the conductivity of graphene. Experimental results show that the time rate of aptamer release from the graphene is inversely proportional to DHEA-S concentration in solution. Thus, the nanosensor can potentially enable label-free, specific and quantitative measurement of DHEA-S and other small molecules.
    Full-text · Conference Paper · Jan 2014
  • [Show abstract] [Hide abstract]
    ABSTRACT: This paper presents a microfluidic device for affinity selection and amplification of cell membrane protein-binding strands from a randomized single-strand DNA (ssDNA) oligomer library, thereby isolating specific cell-targeting aptamers. The device consists of the selection and amplification microchambers situated on a temperature control chip. Affinity selection, integrated with cell culturing, of cell-binding ssDNA is performed in the selection chamber; the selected strands are then amplified by bead-based polymerase chain reaction (PCR) in the amplification chamber. Transfer between the selection and amplification microchambers using pressure-driven flow realizes multi-round aptamer isolation on a single chip. Experimental results demonstrate the feasibility of using this device to develop aptamers that specifically bind to target cells.
    No preview · Conference Paper · Jan 2014

Publication Stats

2k Citations
228.93 Total Impact Points

Institutions

  • 2006-2015
    • Columbia University
      • Department of Mechanical Engineering
      New York, New York, United States
  • 2002-2006
    • Carnegie Mellon University
      • Department of Mechanical Engineering
      Pittsburgh, Pennsylvania, United States
  • 1997-2001
    • California Institute of Technology
      • • Division of Engineering and Applied Science
      • • Department of Electrical Engineering
      • • Department of Mechanical & Civil Engineering
      Pasadena, California, United States