31 research outputs found
Cell-Penetrating Peptide Spirolactam Derivative as a Reversible Fluorescent pH Probe for Live Cell Imaging
A colorless
and nonfluorescent spirolactam derivative, RhB-R<sub>12</sub>K, was
synthesized by amide condensation between the carboxyl
group of rhodamine B (RhB) and the amino group of cell-penetrating
peptide (CPP). The fluorescence intensity of RhB-R<sub>12</sub>K sharply
increased as the pH value decreased from 8.0 to 4.9, demonstrating
sensitive and reversible response to intracellular pH distribution.
This CPP probe was completely water soluble, had low cytotoxicity,
was membrane permeable, and was suitable for pH measurement in various
organelles by choosing organelle-specific CPP sequences. Interestingly,
CPPs acted not only as carriers but also as indispensable parts of
fluorophores here. The presence of active groups on the peptides potentially
allows for modification with additional dyes to construct multifunctional
and ratiometric probes for cell imaging
Detecting Low-Abundance Molecules at Single-Cell Level by Repeated Ion Accumulation in Ion Trap Mass Spectrometer
Low-abundance metabolites
or proteins in single-cell samples are
usually undetectable by mass spectrometry (MS) due to the limited
amount of substances in single cells. This limitation inspired us
to further enhance the sensitivity of commercial mass spectrometers.
Herein, we developed a technique named repeated ion accumulation by
ion trap MS, which is capable of enhancing the sensitivity by selectively
and repeatedly accumulating ions in a linear ion trap for up to 25
cycles. The increase in MS sensitivity was positively correlated with
the number of repeated cycles. When ions were repeatedly accumulated
for 25 cycles, the sensitivity of adenosine triphosphate detection
was increased by 22-fold within 1.8 s. Our technique could stably
detect low-abundance ions, especially MS<i><sup>n</sup></i> ions, at the single-cell level, such as 5-methylcytosine hydrolyzed
from sample equivalent to ∼0.2 MCF7 cell. The strategy presented
in this study offers the possibility to aid single-cell analysis by
enhancing MS detection sensitivity
Multicolor Imaging of Cancer Cells with Fluorophore-Tagged Aptamers for Single Cell Typing
The
discrimination of the type of cancer cells remains challenging
due to the subtle differences in their expression of membrane receptors.
In this work, we developed a multicolor cell imaging method for distinguishing
the type of cancer cells with fluorophore-tagged aptamers. We found
that the interaction between aptamers and cancer cells was affected
by both of the sequence of aptamers and the labeled dyes. As the co-ownership
of biomarkers for different cancer cell lines, the fluorophore-tagged
aptamers interacted with different cancer cell lines in different
degree, resulting in a distinct color to discriminate the type of
cancer cells at single cell level. Taking advantage of the cross-reactive
ability of the fluorophore-tagged aptamers, we could not only distinguish
the cancerous cells quickly from large quantities of noncancerous
cells, but also identify the type of the cancerous cells. This work
has potential application for cancer diagnostic and therapy in the
future
Detecting Low-Abundance Molecules at Single-Cell Level by Repeated Ion Accumulation in Ion Trap Mass Spectrometer
Low-abundance metabolites
or proteins in single-cell samples are
usually undetectable by mass spectrometry (MS) due to the limited
amount of substances in single cells. This limitation inspired us
to further enhance the sensitivity of commercial mass spectrometers.
Herein, we developed a technique named repeated ion accumulation by
ion trap MS, which is capable of enhancing the sensitivity by selectively
and repeatedly accumulating ions in a linear ion trap for up to 25
cycles. The increase in MS sensitivity was positively correlated with
the number of repeated cycles. When ions were repeatedly accumulated
for 25 cycles, the sensitivity of adenosine triphosphate detection
was increased by 22-fold within 1.8 s. Our technique could stably
detect low-abundance ions, especially MS<i><sup>n</sup></i> ions, at the single-cell level, such as 5-methylcytosine hydrolyzed
from sample equivalent to ∼0.2 MCF7 cell. The strategy presented
in this study offers the possibility to aid single-cell analysis by
enhancing MS detection sensitivity
Aptamer-Based Plasmonic Sensor Array for Discrimination of Proteins and Cells with the Naked Eye
We
developed a colorimetric sensor array with reported protein aptamers
as nonspecific receptors. We found that different target proteins
could make the aptamer-protected gold nanoparticles (AuNPs) exhibit
different aggregation behaviors in the presence of a high concentration
salt and cause various color change. On the basis of this phenomenon,
we applied a series of reported protein aptamers as a receptor array
obtaining a distinct response pattern to each target protein. Seven
proteins have been well distinguished with the naked eye at the 50
nM level. Cancerous human cells have also been discriminated from
noncancerous cells. This method is simple, label-free, and sensitive.
It will broaden the application filed of plasmonic nanoparticle-based
sensors and give a new direction of developing sensitive array sensing
systems
Protein Discrimination Using Fluorescent Gold Nanoparticles on Plasmonic Substrates
Fluorescent gold nanoparticle (GNP) is an easily synthesized
and biocompatible optical platform for sensing and imaging with tunable
near-infrared (NIR) emission. However, the relatively low fluorescence
(FL) quantum yield limits the further improvement of sensitivity and
application. Here, we find that, on plasmonic substrates, the FL intensity
of protein-directed synthesized GNPs can be enhanced significantly
(∼20-fold). Moreover, protein analytes can interact with GNPs
and influence the enhanced fluorescence process so that we can obtain
distinct FL image patterns. Then, using the array-based sensing strategy,
protein discrimination can be achieved. In our present experiment,
five GNPs were used as sensing elements and 10 kinds of proteins at
three concentrations (0.2, 0.5, and 1 μM) were successfully
identified. This array-based sensing strategy using enhanced-fluorescence
from GNPs is highly sensitive and differentiable, expanding the application
field of GNPs
Rapid Analysis of Unsaturated Fatty Acids on Paper-Based Analytical Devices via Online Epoxidation and Ambient Mass Spectrometry
In
this work, we demonstrate a novel design that allows rapid online
identification and quantitation of unsaturated fatty acid Cî—»C
location isomers via epoxidation and ambient mass spectrometry (MS).
Unsaturated fatty acid solution was loaded on a paper strip placed
between a low-temperature plasma probe and the inlet of a mass spectrometer.
Reactive oxygen species in the plasma promoted epoxidation at the
Cî—»C, and the product was simultaneously ionized. Upon collision-induced
dissociation (CID), the epoxidation product was fragmented to release
diagnostic ions specific to the Cî—»C location. The whole analytical
workflow can be completed within 5 s and is particularly promising
for point-of-care (POC) clinical diagnosis, considering its fast,
high-throughput nature, and coupling with paper-based analytical devices
In Vivo Nanoelectrospray for the Localization of Bioactive Molecules in Plants by Mass Spectrometry
The method for the localization of bioactive molecules
in plants
is highly needed since it provides a fundamental prerequisite for
understanding their physiological and ecological functions. Here,
we propose a simple method termed in vivo nanoelectrospray for the
localization of bioactive molecules in plants without sample preparation.
A capillary is partly inserted into the plant to sample liquid from
a highly located region, and then, a high voltage is applied to the
plant to generate an electrospray from the capillary tip for mass
spectrometry analysis. Using this method, bioactive molecules such
as saccharides, glycoalkaloids, flavonoids, organic acids, and glucosinolates
(GLs) are detected in the target regions of living plants or fresh
fruits. Original information for endogenous chemicals including liable
molecules in plant can be obtained. A sketchy three-dimensional distribution
of glycoalkaloids in a cherry tomato has been obtained. The present
work provides a powerful tool for the study of bioactive molecules
in a living plant by mass spectrometry
Controlling Charge States of Peptides through Inductive Electrospray Ionization Mass Spectrometry
A novel ionization device for controlling the charge states of peptides based on an inductive elecrospray ionization technique was developed. This ion source keeps the major capabilities of electrospray ionization (ESI) which is compatible with liquid separation techniques (such as liquid chromatography (LC) and capillary electrophoresis (CE)) and can be potentially used to control the charge states of peptides accurately by simply varying the AC voltage applied. In comparison with conventional ESI, inductive ESI successfully simplifies the mass spectrum by reducing the charge states of peptide to a singly charged one, as well as eliminating the adduct ions
Hydrogen Sulfide Detection Based on Reflection: From a Poison Test Approach of Ancient China to Single-Cell Accurate Localization
With the inspiration of an ancient
Chinese poison test approach,
we report a rapid hydrogen sulfide detection strategy in specific
areas of live cells using silver needles with good spatial resolution
of 2 × 2 μm<sup>2</sup>. Besides the accurate-localization
ability, this reflection-based strategy also has attractive merits
of convenience and robust response when free pretreatment and short
detection time are concerned. The success of endogenous H<sub>2</sub>S level evaluation in cellular cytoplasm and nuclear of human A549
cells promises the application potential of our strategy in scientific
research and medical diagnosis