11 research outputs found
Integrated Distance-Based Origami Paper Analytical Device for One-Step Visualized Analysis
An
integrated distance-based origami paper analytical device (ID-<i>o</i>PAD) is developed for simple, user friendly and visual
detection of targets of interest. The platform enables complete integration
of target recognition, signal amplification, and visual signal output
based on aptamer/invertase-functionalized sepharose beads, cascaded
enzymatic reactions, and a 3D microfluidic paper-based analytical
device with distance-based readout, respectively. The invertase–DNA
conjugate is released upon target addition, after which it permeates
through the cellulose and flows down into the bottom detection zone,
whereas sepharose beads with larger size are excluded and stay in
the upper zone. Finally, the released conjugate initiates cascaded
enzymatic reactions and translates the target signal into a brown
bar chart reading. By simply closing the device, the ID-<i>o</i>PAD enables a sample-in-answer-out assay within 30 min with visual
and quantitative readout. Importantly, bound/free probe separation
is achieved by taking advantage of the size difference between sepharose
beads and cellulose pores, and the downstream enzymatic amplification
is realized based on the compatibility of multiple enzymes with corresponding
substrates. Overall, with the advantages of low-cost, disposability,
simple operation, and visual quantitative readout, the ID-<i>o</i>PAD offers an ideal platform for point-of-care testing,
especially in resource-limited areas
Logic-Gates of Gas Pressure for Portable, Intelligent and Multiple Analysis of Metal Ions
DNA logic gates have shown outstanding
magic in intelligent biology
applications, but it remains challenging to construct a portable,
affordable and convenient DNA logic gate. Herein, logic gates of gas
pressure were innovatively developed for multiplex analysis of metal
ions. Hg2+ and Ag+ were input to interact specifically
with the respective mismatched base pairs, which activated DNA extension
reaction by polymerase and led to the enrichment of platinum nanoparticles
for catalyzing the decomposition of peroxide hydrogen. Thus, the gas
pressure obtained from a sealed well was used as output for detecting
or identifying metal ions. Hg2+ and Ag+ were
sensitively and selectively detected, and the assay of the real samples
was also satisfactory. Based on this, DNA logic gates, including YES,
NOT, AND, OR, NAND, NOR, INHIBIT, and XOR were successfully established
using a portable and hand-held gas pressure meter as detector. So,
the interactions between DNA and metal ions were intelligently transferred
into the output of gas pressure, which made metal ions to be detected
portably and identified intelligently. Given the remarkable merits
of simplicity, logic operation, and portable output, the metal ion-driven
DNA logic gate of gas pressure provides a promising way for intelligent
and portable biosensing
Portable and Label-Free Sensor Array for Discriminating Multiple Analytes via a Handheld Gas Pressure Meter
Cross-reactive sensor arrays are useful for discriminating
multiple
analytes in a complex sample. Herein, a portable and label-free gas
pressure sensor array was proposed for multiplex analysis via a handheld
gas pressure meter. It is based on the interaction diversity of analytes
with catalase-like nanomaterials, including Pt nanoparticles (PtNP),
Co3O4 nanosheets (Co3O4NS), and Pt–Co alloy nanosheets (PtCoNS), respectively. Thus,
the diverse influence of analytes on the catalase-like activity could
be output as the difference in the gas pressure. By using principal
component analysis, eight proteins were well distinguished by the
gas pressure sensor array at the 10 nM level within 12 min. Moreover,
different concentrations of proteins and mixtures of proteins could
likewise be discriminated. More importantly, the effective discrimination
of proteins in human serum and discrimination of five kinds of cells
further confirmed the potential of the gas pressure sensor array.
Therefore, it provides a portable, cheap, sensitive, and label-free
gas pressure sensor array, which is totally different from the reported
sensor arrays and holds great potential for portable and cheap discrimination
of multiple analytes
Dual-Mode Logic Gate for Intelligent and Portable Detection of MicroRNA Based on Gas Pressure and Lateral Flow Assay
Molecular logic gate provides an intelligent option for
simultaneous
detection of biomarkers. Herein, a dual-mode DNA logic gate was proposed
to portably and intelligently detect multiple microRNAs (miRNAs) by
gas pressure biosensing and lateral flow assay (LFA). A platinum-coated
gold nanoparticle (Au@PtNP) with catalase-like activity was used as
a signal reporter to achieve a dual-signal readout. MiRNAs as the
input initiated the cyclic strand displacement reaction (SDR) to enrich
a large amount of Au@PtNPs. Thus, miRNA can be visually detected by
a lateral flow strip (LFS) using the grayish-brown color of Au@PtNPs
as output 1. Furthermore, Au@PtNP-catalyzed decomposition of H2O2 resulted in gas pressure as output 2, which
was measured by a digital and handheld gas pressure meter. As a consequence,
microRNA 21 (miR-21) was sensitively and reliably detected with the
limit of detection (LOD) of 7.2 pM. The selectivity and real sample
analysis were both satisfactory. Significantly, two-input and three-input
AND logic gates were successfully developed to realize multiple detection
of two miRNAs and three miRNAs, which provide a promising way for
intelligent multi-input analysis. Predictably, with the advantages
of portability, simplicity, and affordability, the dual-mode logic
gate based on gas pressure biosensing and LFA offers a new perspective
on the field of intelligent and portable biosensing and bioanalysis
Integrated Distance-Based Origami Paper Analytical Device for One-Step Visualized Analysis
An
integrated distance-based origami paper analytical device (ID-<i>o</i>PAD) is developed for simple, user friendly and visual
detection of targets of interest. The platform enables complete integration
of target recognition, signal amplification, and visual signal output
based on aptamer/invertase-functionalized sepharose beads, cascaded
enzymatic reactions, and a 3D microfluidic paper-based analytical
device with distance-based readout, respectively. The invertase–DNA
conjugate is released upon target addition, after which it permeates
through the cellulose and flows down into the bottom detection zone,
whereas sepharose beads with larger size are excluded and stay in
the upper zone. Finally, the released conjugate initiates cascaded
enzymatic reactions and translates the target signal into a brown
bar chart reading. By simply closing the device, the ID-<i>o</i>PAD enables a sample-in-answer-out assay within 30 min with visual
and quantitative readout. Importantly, bound/free probe separation
is achieved by taking advantage of the size difference between sepharose
beads and cellulose pores, and the downstream enzymatic amplification
is realized based on the compatibility of multiple enzymes with corresponding
substrates. Overall, with the advantages of low-cost, disposability,
simple operation, and visual quantitative readout, the ID-<i>o</i>PAD offers an ideal platform for point-of-care testing,
especially in resource-limited areas
Highly Sensitive and Automated Surface Enhanced Raman Scattering-based Immunoassay for H5N1 Detection with Digital Microfluidics
Digital
microfluidics (DMF) is a powerful platform for a broad
range of applications, especially immunoassays having multiple steps,
due to the advantages of low reagent consumption and high automatization.
Surface enhanced Raman scattering (SERS) has been proven as an attractive
method for highly sensitive and multiplex detection, because of its
remarkable signal amplification and excellent spatial resolution.
Here we propose a SERS-based immunoassay with DMF for rapid, automated,
and sensitive detection of disease biomarkers. SERS tags labeled with
Raman reporter 4-mercaptobenzoic acid (4-MBA) were synthesized with
a core@shell nanostructure and showed strong signals, good uniformity,
and high stability. A sandwich immunoassay was designed, in which
magnetic beads coated with antibodies were used as solid support to
capture antigens from samples to form a beads–antibody–antigen
immunocomplex. By labeling the immunocomplex with a detection antibody-functionalized
SERS tag, antigen can be sensitively detected through the strong SERS
signal. The automation capability of DMF can greatly simplify the
assay procedure while reducing the risk of exposure to hazardous samples.
Quantitative detection of avian influenza virus H5N1 in buffer and
human serum was implemented to demonstrate the utility of the DMF-SERS
method. The DMF-SERS method shows excellent sensitivity (LOD of 74
pg/mL) and selectivity for H5N1 detection with less assay time (<1
h) and lower reagent consumption (∼30 μL) compared to
the standard ELISA method. Therefore, this DMF-SERS method holds great
potentials for automated and sensitive detection of a variety of infectious
diseases
Microwell Array Method for Rapid Generation of Uniform Agarose Droplets and Beads for Single Molecule Analysis
Compartmentalization
of aqueous samples in uniform emulsion droplets
has proven to be a useful tool for many chemical, biological, and
biomedical applications. Herein, we introduce an array-based emulsification
method for rapid and easy generation of monodisperse agarose-in-oil
droplets in a PDMS microwell array. The microwells are filled with
agarose solution, and subsequent addition of hot oil results in immediate
formation of agarose droplets due to the surface-tension of the liquid
solution. Because droplet size is determined solely by the array unit
dimensions, uniform droplets with preselectable diameters ranging
from 20 to 100 μm can be produced with relative standard deviations
less than 3.5%. The array-based droplet generation method was used
to perform digital PCR for absolute DNA quantitation. The array-based
droplet isolation and sol–gel switching property of agarose
enable formation of stable beads by chilling the droplet array at
−20 °C, thus, maintaining the monoclonality of each droplet
and facilitating the selective retrieval of desired droplets. The
monoclonality of droplets was demonstrated by DNA sequencing and FACS
analysis, suggesting the robustness and flexibility of the approach
for single molecule amplification and analysis. We believe our approach
will lead to new possibilities for a great variety of applications,
such as single-cell gene expression studies, aptamer selection, and
oligonucleotide analysis
Microwell Array Method for Rapid Generation of Uniform Agarose Droplets and Beads for Single Molecule Analysis
Compartmentalization
of aqueous samples in uniform emulsion droplets
has proven to be a useful tool for many chemical, biological, and
biomedical applications. Herein, we introduce an array-based emulsification
method for rapid and easy generation of monodisperse agarose-in-oil
droplets in a PDMS microwell array. The microwells are filled with
agarose solution, and subsequent addition of hot oil results in immediate
formation of agarose droplets due to the surface-tension of the liquid
solution. Because droplet size is determined solely by the array unit
dimensions, uniform droplets with preselectable diameters ranging
from 20 to 100 μm can be produced with relative standard deviations
less than 3.5%. The array-based droplet generation method was used
to perform digital PCR for absolute DNA quantitation. The array-based
droplet isolation and sol–gel switching property of agarose
enable formation of stable beads by chilling the droplet array at
−20 °C, thus, maintaining the monoclonality of each droplet
and facilitating the selective retrieval of desired droplets. The
monoclonality of droplets was demonstrated by DNA sequencing and FACS
analysis, suggesting the robustness and flexibility of the approach
for single molecule amplification and analysis. We believe our approach
will lead to new possibilities for a great variety of applications,
such as single-cell gene expression studies, aptamer selection, and
oligonucleotide analysis
In Situ Pt Staining Method for Simple, Stable, and Sensitive Pressure-Based Bioassays
Pressure-based bioassays
(PASS) integrate a molecular recognition
process with a catalyzed gas generation reaction, enabling sensitive
and portable quantitation of biomarkers in clinical samples. Using
platinum nanoparticles (PtNPs) as a catalyst has significantly improved
the sensitivity of PASS compared with protein enzyme-based detection.
However, PtNPs are easily deactivated during storage or after being
decorated with antibodies. Moreover, nonspecific adsorption of PtNPs
on substrates has been a problem, resulting in significant backgrounds.
To solve these problems of PtNP-based detection, we report a robust,
simple, stable, and sensitive Pt staining method for PASS. Detection
antibody-decorated gold nanoparticles (AuNPs) are used to perform
enzyme-linked immunosorbent assay, followed by Pt staining to stain
AuNPs with Ag and Pt bimetallic shells (Au@AgPtNPs), which endow AuNPs
with catalytic activity. The concentration of targets can be quantitatively
determined by measuring the pressure due to O<sub>2</sub> gas (g)
formed by the decomposition of H<sub>2</sub>O<sub>2</sub> catalyzed
by Au@AgPtNPs. C-reactive protein and avian influenza hemagglutinin
5 neuraminidase 1 can be quantitatively detected with detection limits
of 0.015 and 0.065 ng/mL, respectively. The simple, stable, and sensitive
properties of the Pt staining-based method will largely broaden the
applications of PASS in clinical diagnosis and biomedicine
Surface-Enhanced Raman Scattering Active Plasmonic Nanoparticles with Ultrasmall Interior Nanogap for Multiplex Quantitative Detection and Cancer Cell Imaging
Due to its large enhancement effect,
nanostructure-based surface-enhanced
Raman scattering (SERS) technology had been widely applied for bioanalysis
and cell imaging. However, most SERS nanostructures suffer from poor
signal reproducibility, which hinders the application of SERS nanostructures
in quantitative detection. We report an etching-assisted approach
to synthesize SERS-active plasmonic nanoparticles with 1 nm interior
nanogap for multiplex quantitative detection and cancer cell imaging.
Raman dyes and methoxy polyÂ(ethylene glycol) thiol (mPEG–SH)
were attached to gold nanoparticles (AuNPs) to prepare gold cores.
Next, Ag atoms were deposited on gold cores in the presence of Pluronic
F127 to form a Ag shell. HAuCl<sub>4</sub> was used to etch the Ag
shell and form an interior nanogap in Au@AgAuNPs, leading to increased
Raman intensity of dyes. SERS intensity distribution of Au@AgAuNPs
was found to be more uniform than that of aggregated AuNPs. Finally,
Au@AgAuNPs were used for multiplex quantitative detection and cancer
cell imaging. With the advantages of simple and rapid preparation
of Au@AgAuNPs with highly uniform, stable, and reproducible Raman
intensity, the method reported here will widen the applications of
SERS-active nanoparticles in diagnostics and imaging