12 research outputs found
Regenerative Electronic Biosensors Using Supramolecular Approaches
A supramolecular interface for Si nanowire FETs has been developed with the aim of creating regenerative electronic biosensors. The key to the approach is Si-NWs functionalized with β-cyclodextrin (β-CD), to which receptor moieties can be attached with an orthogonal supramolecular linker. Here we demonstrate full recycling using the strongest biomolecular system known, streptavidin (SAv)–biotin. The bound SAv and the linkers can be selectively removed from the surface through competitive desorption with concentrated β-CD, regenerating the sensor for repeated use. An added advantage of β-CD is the possibility of stereoselective sensors, and we demonstrate here the ability to quantify the enantiomeric composition of chiral targets
Solid-State Microfluidics with Integrated Thin-Film Acoustic Sensors
For
point-of-care applications, integrating sensors into a microfluidic
chip is a nontrivial task because conventional detection modules are
bulky and microfluidic chips are small in size and their fabrication
processes are not compatible. In this work, a solid-state microfluidic
chip with on-chip acoustic sensors using standard thin-film technologies
is introduced. The integrated chip is essentially a stack of thin
films on silicon substrate, featuring compact size, electrical input
(fluid control), and electrical output (sensor read-out). These features
all contribute to portability. In addition, by virtue of processing
discrete microdroplets, the chip provides a solution to the performance
degradation bottleneck of acoustic sensors in liquid-phase sensing.
Label-free immunoassays in serum are carried out, and the viability
of the chip is further demonstrated by result comparison with commercial
ELISA in prostate-specific antigen sensing experiments. The solid-state
chip is believed to fit specific applications in personalized diagnostics
and other relevant clinical settings where instrument portability
matters
Biofouling Removal and Protein Detection Using a Hypersonic Resonator
Nonspecific binding
(NSB) is a general issue for surface based
biosensors. Various approaches have been developed to prevent or remove
the NSBs. However, these approaches either increased the background
signals of the sensors or limited to specific transducers interface.
In this work, we developed a hydrodynamic approach to selectively
remove the NSBs using a microfabricated hypersonic resonator with
2.5 gigahertz (GHz) resonant frequency. The high frequency device
facilitates generation of multiple controlled microvortexes which
then create cleaning forces at the solid–liquid interfaces.
The competitive adhesive and cleaning forces have been investigated
using the finite element method (FEM) simulation, identifying the
feasibility of the vortex-induced NSB removal. NSB proteins have been
selectively removed experimentally both on the surface of the resonator
and on other substrates which contact the vortexes. Thus, the developed
hydrodynamic approach is believed to be a simple and versatile tool
for NSB removal and compatible to many sensor systems. The unique
feature of the hypersonic resonator is that it can be used as a gravimetric
sensor as well; thus a combined NSB removal and protein detection
dual functional biosensor system is developed
Smartphone-Enabled Colorimetric Trinitrotoluene Detection Using Amine-Trapped Polydimethylsiloxane Membranes
A smartphone-enabled
platform for easy and portably colorimetric analysis of 2,4,6-trinitroÂtoluene
(TNT) using amine-trapped PDMS is designed and implemented. The amine-trapped
polydimethylÂsiloxane (PDMS) is simply prepared by immersing
the cured PDMS in aminosilane solutions forming an amine-containing
polymer. After contacting with TNT-containing solutions, the colorless
PDMS showed a rapid colorimetric change which can be easily identified
by the naked eye. The amine-trapped PDMS was carefully optimized to
achieve visible detection of TNT at concentrations as low as 1 ÎĽM.
Using an integrated camera in the smartphone, pictures of colored
PDMS membranes can be analyzed by a home-developed mobile application.
Thus, the TNT amount can be precisely quantified. Direct TNT detection
in real samples (e.g., drinking, tap, and lake waters) is demonstrated
as well. The smartphone-enabled colorimetric method using amine-trapped
PDMS membranes realizes a convenient and efficient approach toward
a portable system for field TNT detections
Cellphone-Enabled Microwell-Based Microbead Aggregation Assay for Portable Biomarker Detection
Quantitative biomarker
detection methods featured with rapidity,
high accuracy, and label-free are demonstrated for the development
of point-of-care (POC) technologies or “beside” diagnostics.
Microbead aggregation via protein-specific linkage provides an effective
approach for selective capture of biomarkers from the samples, and
can directly readout the presence and amount of the targets. However,
sensors or microfluidic analyzers that can accurately quantify the
microbead aggregation are scared. In this work, we demonstrate a microwell-based
microbeads analyzing system, by which online manipulations of microbeads
including trapping, arraying, and rotations can be realized, providing
a series of microfluidic approaches to layout the aggregated microbeads
for further convenient characterizations. Prostate specific antigen
is detected using the proposed system, demonstrating the limit of
detection as low as 0.125 ng/mL (3.67 pM). A two-step reaction kinetics
model is proposed for the first time to explain the dynamic process
of microbeads aggregation. The developed microbeads aggregation analysis
system has the advantages of label-free detection, high throughput,
and low cost, showing great potential for portable biomarker detection
Detection of Volatile Organic Compounds Using Microfabricated Resonator Array Functionalized with Supramolecular Monolayers
This paper describes the detection
of volatile organic compounds (VOCs) using an e-nose type integrated
microfabricated sensor array, in which each resonator is coated with
different supramolecular monolayers: <i>p</i>-<i>tert</i>-butyl calix[8]Âarene (Calix[8]Âarene), 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine
(Porphyrin), β-cyclodextrin (β-CD), and cucurbit[8]Âuril
(CB[8]). Supramolecular monolayers fabricated by Langmuir–Blodgett
techniques work as specific sensing interface for different VOCs recognition
which increase the sensor selectivity. Microfabricated ultrahigh working
frequency film bulk acoustic resonator (FBAR) transducers (4.4 GHz)
enable their high sensitivity toward monolayer gas sensing which facilitate
the analyses of VOCs adsorption isotherms and kinetics. Two affinity
constants (<i>K</i><sub>1</sub>, <i>K</i><sub>2</sub>) are obtained for each VOC, which indicate the gas molecule
adsorption happen inside and outside of the supramolecular cavities.
Additional kinetic information on adsorption and desorption rate constants
(<i>k</i><sub>a</sub>, <i>k</i><sub>d</sub>) are
obtained as well from exponential fitting results. The five parameters,
one from the conventional frequency shift signals of mass transducers
and the other four from the indirect analyses of monolayer adsorption
behaviors, thus enrich the sensing matrix (Δ<i>f</i>, <i>K</i><sub>1</sub>, <i>K</i><sub>2</sub>, <i>k</i><sub>a</sub>, <i>k</i><sub>d</sub>) which can
be used as multiparameter fingerprint patterns for highly selective
detection and discrimination of VOCs
A Universal Biomolecular Concentrator To Enhance Biomolecular Surface Binding Based on Acoustic NEMS Resonator
In designing bioassay systems for
low-abundance biomolecule detection,
most research focuses on improving transduction mechanisms while ignoring
the intrinsically fundamental limitations in solution: mass transfer
and binding affinity. We demonstrate enhanced biomolecular surface
binding using an acoustic nano-electromechanical system (NEMS) resonator,
as an on-chip biomolecular concentrator which breaks both mass transfer
and binding affinity limitations. As a result, a concentration factor
of 10<sup>5</sup> has been obtained for various biomolecules. The
resultantly enhanced surface binding between probes on the absorption
surface and analytes in solution enables us to lower the limit of
detection for representative proteins. We also integrated the biomolecular
concentrator into an optoelectronic bioassay platform to demonstrate
delivery of proteins from buffer/serum to the absorption surface.
Since the manufacture of the resonator is CMOS-compatible, we expect
it to be readily applied to further analysis of biomolecular interactions
in molecular diagnostics
A Universal Biomolecular Concentrator To Enhance Biomolecular Surface Binding Based on Acoustic NEMS Resonator
In designing bioassay systems for
low-abundance biomolecule detection,
most research focuses on improving transduction mechanisms while ignoring
the intrinsically fundamental limitations in solution: mass transfer
and binding affinity. We demonstrate enhanced biomolecular surface
binding using an acoustic nano-electromechanical system (NEMS) resonator,
as an on-chip biomolecular concentrator which breaks both mass transfer
and binding affinity limitations. As a result, a concentration factor
of 10<sup>5</sup> has been obtained for various biomolecules. The
resultantly enhanced surface binding between probes on the absorption
surface and analytes in solution enables us to lower the limit of
detection for representative proteins. We also integrated the biomolecular
concentrator into an optoelectronic bioassay platform to demonstrate
delivery of proteins from buffer/serum to the absorption surface.
Since the manufacture of the resonator is CMOS-compatible, we expect
it to be readily applied to further analysis of biomolecular interactions
in molecular diagnostics
A Universal Biomolecular Concentrator To Enhance Biomolecular Surface Binding Based on Acoustic NEMS Resonator
In designing bioassay systems for
low-abundance biomolecule detection,
most research focuses on improving transduction mechanisms while ignoring
the intrinsically fundamental limitations in solution: mass transfer
and binding affinity. We demonstrate enhanced biomolecular surface
binding using an acoustic nano-electromechanical system (NEMS) resonator,
as an on-chip biomolecular concentrator which breaks both mass transfer
and binding affinity limitations. As a result, a concentration factor
of 10<sup>5</sup> has been obtained for various biomolecules. The
resultantly enhanced surface binding between probes on the absorption
surface and analytes in solution enables us to lower the limit of
detection for representative proteins. We also integrated the biomolecular
concentrator into an optoelectronic bioassay platform to demonstrate
delivery of proteins from buffer/serum to the absorption surface.
Since the manufacture of the resonator is CMOS-compatible, we expect
it to be readily applied to further analysis of biomolecular interactions
in molecular diagnostics
A Universal Biomolecular Concentrator To Enhance Biomolecular Surface Binding Based on Acoustic NEMS Resonator
In designing bioassay systems for
low-abundance biomolecule detection,
most research focuses on improving transduction mechanisms while ignoring
the intrinsically fundamental limitations in solution: mass transfer
and binding affinity. We demonstrate enhanced biomolecular surface
binding using an acoustic nano-electromechanical system (NEMS) resonator,
as an on-chip biomolecular concentrator which breaks both mass transfer
and binding affinity limitations. As a result, a concentration factor
of 10<sup>5</sup> has been obtained for various biomolecules. The
resultantly enhanced surface binding between probes on the absorption
surface and analytes in solution enables us to lower the limit of
detection for representative proteins. We also integrated the biomolecular
concentrator into an optoelectronic bioassay platform to demonstrate
delivery of proteins from buffer/serum to the absorption surface.
Since the manufacture of the resonator is CMOS-compatible, we expect
it to be readily applied to further analysis of biomolecular interactions
in molecular diagnostics