9 research outputs found
Mass Spectrometry for Paper-Based Immunoassays: Toward On‑Demand Diagnosis
Current
analytical methods, either point-of-care or centralized
detection, are not able to meet recent demands of patient-friendly
testing and increased reliability of results. Here, we describe a
two-point separation on-demand diagnostic strategy based on a paper-based
mass spectrometry immunoÂassay platform that adopts stable and
cleavable ionic probes as mass reporter; these probes make possible
sensitive, interruptible, storable, and restorable on-demand detection.
In addition, a new touch paper spray method was developed for on-chip,
sensitive, and cost-effective analyte detection. This concept is successfully
demonstrated via (i) the detection of <i>Plasmodium falciparum</i> histidine-rich protein 2 antigen and (ii) multiplexed and simultaneous
detection of cancer antigen 125 and carcinoembryonic antigen
Stable-Isotope N‑Me Aziridination Enables Accurate Quantitative CC Isomeric Lipidomics
Accurate lipid quantification is
essential to revealing their roles
in physiological and pathological processes. However, difficulties
in the structural resolution of lipid isomers hinder their further
accurate quantification. To address this challenge, we developed a
novel stable-isotope N-Me aziridination strategy that enables simultaneous
qualification and quantification of unsaturated lipid isomers. The
one-step introduction of the 1-methylaziridine structure not only
serves as an activating group for the CC bond to facilitate
positional identification but also as an isotopic inserter to achieve
accurate relative quantification. The high performance of this reaction
for the identification of unsaturated lipids was verified by large-scale
resolution of the CC positions of 468 lipids in serum. More
importantly, by using this bifunctional duplex labeling method, various
unsaturated lipids such as fatty acids, phospholipids, glycerides,
and cholesterol ester were accurately and individually quantified
at the CC bond isomeric level during the mouse brain ischemia.
This study provides a new approach to quantitative structural lipidomics
Stable-Isotope N‑Me Aziridination Enables Accurate Quantitative CC Isomeric Lipidomics
Accurate lipid quantification is
essential to revealing their roles
in physiological and pathological processes. However, difficulties
in the structural resolution of lipid isomers hinder their further
accurate quantification. To address this challenge, we developed a
novel stable-isotope N-Me aziridination strategy that enables simultaneous
qualification and quantification of unsaturated lipid isomers. The
one-step introduction of the 1-methylaziridine structure not only
serves as an activating group for the CC bond to facilitate
positional identification but also as an isotopic inserter to achieve
accurate relative quantification. The high performance of this reaction
for the identification of unsaturated lipids was verified by large-scale
resolution of the CC positions of 468 lipids in serum. More
importantly, by using this bifunctional duplex labeling method, various
unsaturated lipids such as fatty acids, phospholipids, glycerides,
and cholesterol ester were accurately and individually quantified
at the CC bond isomeric level during the mouse brain ischemia.
This study provides a new approach to quantitative structural lipidomics
2,3,4,5-Tetrakis(3′,4′-dihydroxylphenyl)thiophene: A New Matrix for the Selective Analysis of Low Molecular Weight Amines and Direct Determination of Creatinine in Urine by MALDI-TOF MS
Small organic matrixes are still the most commonly used
ones in
matrix-assisted laser desorption/ionization mass spectrometry (MALDI
MS) because of their advantages of high sensitivity, convenience,
and cost-effectiveness. However, due to the matrix interference in
the low mass region, the direct analysis of low molecular weight amines
in complex surroundings with conventional organic matrixes remains
a challenge. Here, a new Brønsted–Lowry acid compound
2,3,4,5-tetrakisÂ(3′,4′-dihydroxylphenyl)Âthiophene (DHPT)
was designed, synthesized, and applied as a matrix for analysis of
low molecular weight amines by MALDI-TOF MS. DHPT displays good selectivity
in the analysis of amines without matrix-related interference and
the low picomole/femtomole limit-of-detection was obtained in positive
ion mode. With DHPT, the metabolites including creatinine, glycine,
alloxan, allantoin, and 3-hydroxyhippuric acid in human urine were
directly analyzed by MALDI-TOF MS. The identity of these metabolites
was confirmed by tandem mass spectrometry. Furthermore, the urine
creatinine was quantitatively determined using isotope-labeled internal
standard. This DHPT-assisted LDI MS method provides a general approach
for both qualitative and quantitative analysis of low molecular weight
amines
Carbon Nanodots As a Matrix for the Analysis of Low-Molecular-Weight Molecules in Both Positive- and Negative-Ion Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry and Quantification of Glucose and Uric Acid in Real Samples
Carbon nanodots were applied for
the first time as a new matrix
for the analysis of low-molecular-weight compounds by matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF
MS) in both positive- and negative-ion modes. A wide range of small
molecules including amino acids, peptides, fatty acids, as well as
β-agonists and neutral oligosaccharides were analyzed by MALDI
MS
with carbon nanodots as the matrix,
and the lowest 0.2 fmol limits-of-detection were obtained for octadecanoic
acid. Clear sodium and potassium adducts and deprotonated signals
were produced in positive- and negative-ion modes. Furthermore, the
glucose and uric acid in real samples were quantitatively determined
by the internal standard method with the linear range of 0.5–9
mM and 0.1–1.8 mM (<i>R</i><sup>2</sup> > 0.999),
respectively. This work gives new insight into the application of
carbon nanodots and provides a general approach for rapid analysis
of low-molecular-weight compounds
Quantitative Assessment of Protein Adsorption on Microparticles with Particle Mass Spectrometry
In
this paper, particle mass spectrometry (PMS), which consists
of an aerodynamic desorption/ionization (AD) source, a quadrupole
ion trap (QIT) mass analyzer, and a charge detector, was exploited
to characterize the protein adsorption on microparticles based on
the mass variations of microparticles before and after protein adsorption.
This method is simple and has low sample cost. Importantly, its mass
resolution is good enough to distinguish the microparticles with and
without protein. For the adsorption of bovine serum albumin (BSA)
on 3 μm porous poly styrene-divinylbenzene (poly S-DVB), the
minimum mass increase that can be resolved by PMS corresponds to 128
fg (1.8 ng/cm<sup>2</sup>) or 1.17 × 10<sup>6</sup> BSA molecules
on each poly S-DVB particle. With PMS, the adsorption process of BSA
on poly S-DVB spheres was successfully characterized, and the obtained
maximum adsorption capacity <i>q</i><sub>m</sub> and dissociation
constant <i>K</i><sub>d</sub> were consistent with that
determined by the conventional depletion method. In addition, the
influence of surface modification of silica particles on the enzyme
immobilization was evaluated. Compared with C<sub>4</sub> (propyldimethylsilane),
C<sub>8</sub> (octyldimethylsilane), and Ph (phenyldimethylchlorosilane),
the CN (cyanoethyldimethylchlorosilane) functionalized silica particles
were screened to be most beneficial for the immobilization of both
lysozyme and trypsin
1,5-Diaminonaphthalene Hydrochloride Assisted Laser Desorption/Ionization Mass Spectrometry Imaging of Small Molecules in Tissues Following Focal Cerebral Ischemia
A sensitive
analytical technique for visualizing small endogenous
molecules simultaneously is of great significance for clearly elucidating
metabolic mechanisms during pathological progression. In the present
study, 1,5-naphthalenediamine (1,5-DAN) hydrochloride was prepared
for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry
imaging (MSI) of small molecules in liver, brain, and kidneys from
mice. Furthermore, 1,5-DAN hydrochloride assisted LDI MSI of small
molecules in brain tissue of rats subjected to middle cerebral artery
occlusion (MCAO) was carried out to investigate the altered metabolic
pathways and mechanisms underlying the development of ischemic brain
damage. Our results suggested that the newly prepared matrix possessed
brilliant features including low cost, strong ultraviolet absorption,
high salt tolerance capacity, and fewer background signals especially
in the low mass range (typically <i>m</i>/<i>z</i> < 500), which permitted us to visualize the spatial distribution
of a broad range of small molecule metabolites including metal ions,
amino acids, carboxylic acids, nucleotide derivatives, peptide, and
lipids simultaneously. Nineteen endogenous metabolites involved in
metabolic networks such as ATP metabolism, tricarboxylic acid (TCA)
cycle, glutamate-glutamine cycle, and malate-aspartate shuttle, together
with metal ions and phospholipids as well as antioxidants underwent
relatively obvious changes after 24 h of MCAO. The results were highly
consistent with the data obtained by MRM MS analysis. These findings
highlighted the promising potential of the organic salt matrix for
application in the field of biomedical research
MALDI-TOF MS Imaging of Metabolites with a <i>N</i>‑(1-Naphthyl) Ethylenediamine Dihydrochloride Matrix and Its Application to Colorectal Cancer Liver Metastasis
Matrix-assisted
laser desorption/ionization mass spectrometry imaging (MALDI MSI)
is a label-free technique for identifying multiplex metabolites and
determining both their distribution and relative abundance in situ.
Our previous study showed that <i>N</i>-(1-naphthyl) ethylenediamine
dihydrochloride (NEDC) could act as a matrix for laser desorption/ionization
time-of-flight mass spectrometry (LDI-TOF MS) detection of oligosaccharides
in solution. In the present study, NEDC-assisted LDI-TOF MSI yielded
many more endogenous compound peaks between <i>m</i>/<i>z</i> 60 and <i>m</i>/<i>z</i> 1600 than
9-aminoacridine (9-AA). Our results show that NEDC-assisted LDI-TOF
MSI is especially well-suited for examining distributions of glycerophospholipids
(GPs) in addition to low molecular weight metabolites below <i>m</i>/<i>z</i> 400. Particularly, NEDC matrix allowed
the LDI-TOF MSI of glucose in animal tissue. Furthermore, NEDC-assisted
LDI-TOF MSI was applied to a mouse model of colorectal cancer liver
metastasis. We revealed the distinct spatio-molecular signatures of
many detected compounds in tumor or tumor-bearing liver, and we found
that taurine, glucose, and some GPs decreased in tumor-bearing liver
as the tumor developed in liver. Importantly, we also found a glucose
gradient in metastatic tumor foci for the first time, which further
confirms the energy competition between tumors and liver remnant due
to the Warburg effect. Our results suggest that NEDC-assisted LDI
MSI provides an in situ label-free analysis of multiple glycerophospholipids
and low molecular weight metabolites (including glucose) with abundant
peaks and high spatial resolution. This will allow future application
to in situ definition of biomarkers, signaling pathways, and disease
mechanisms
In Situ Bioconjugation and Ambient Surface Modification Using Reactive Charged Droplets
Molecular ions are generated in induced
electrospray ionization,
and they can be transported to grounded ambient surfaces in the form
of charged microdroplets. Efficient amide bonds formation between
amines and carboxylic acids were observed inside charged droplets
during transfer to the surface. Biomolecules derivatized using this
method were self-assembled on a bare gold surface via Au–S
bonds under the charged microdroplet environment. Cyclic voltammetric
analysis of the self-assembled molecular film showed accelerated protein
derivatization with cysteine, which allowed the covalent immobilization
of the protein to the gold surface. Cytochrome C-functionalized electrodes
prepared using the induced dual nanoelectrospray process showed bioactivity
toward aqueous solutions of hydrogen peroxide below 50 μM. In
effect, we have developed a method that allows derivatization of biomolecules
and their immobilization at ambient surfaces in a single experimental
step