6 research outputs found
Sodium-Doped Gold-Assisted Laser Desorption Ionization for Enhanced Imaging Mass Spectrometry of Triacylglycerols from Thin Tissue Sections
The
deposition of sodium salts followed by a sputtered layer of
gold has been demonstrated to be a power combination for the analysis
of triacylglycerols (TAGs) from tissue sections by laser desorption
ionization (LDI) imaging mass spectrometry (IMS). Various sodium salts
were tested for their capability to ionize TAGs and their ability
to produce fast drying, small crystals (≤3 μm). The spray
deposition of a sodium acetate and carbonate buffer mixture at pH
10.3 on which a 28 ± 3 nm sputtered layer of gold (Au-CBS) is
subsequently deposited was found to provide the most effective combination
for TAG analysis by high imaging resolution IMS. Under these conditions,
a 30-fold increase in TAG signal intensity was observed when compared
to matrix-assisted LDI (MALDI) methods using 2,5-dihydrobenzoic acid
as matrix. Furthermore, Au-CBS led to an increase in the number of
detected TAG species from ∼7 with DHB to more than 25 with
the novel method, while few phospholipid signals were observed. These
results were derived from the IMS investigation of fresh frozen mouse
liver and rabbit adrenal gland tissue sections with a range of higher
spatial resolutions between 35 and 10 μm. Au-CBS-LDI MS presents
a highly sensitive and specific alternative to MALDI MS for imaging
of TAGs from tissue sections. This novel approach has the potential
to provide new biological insights on the role of TAGs in both health
and disease
Response Monitoring of Acute Lymphoblastic Leukemia Patients Undergoing l‑Asparaginase Therapy: Successes and Challenges Associated with Clinical Sample Analysis in Plasmonic Sensing
Monitoring
the response of patients undergoing chemotherapeutic
treatments is of great importance to predict remission success, avoid
adverse effects and thus, maximize the patients’ quality of
life. In the case of leukemia patients treated with E. coli l-asparaginase, monitoring the immune
response by the detection of specific antibodies to l-asparaginase
in the serum of patients can prevent extended immune response to the
drug. Here, we developed a surface plasmon resonance (SPR) biosensor
to rapidly detect anti-asparaginase antibodies directly in patients’
sera, without requiring sample pretreatment or dilution. A direct
assay with SPR sensing to detect anti-asparaginase antibodies exhibited
a limit of detection of 500 pM and a high sensitivity range between
100 nM and 1 μM in pooled and undiluted human serum from a commercial
source. While the SPR assay showed excellent reproducibility (12%
RSD) in pooled serum, challenges were encountered upon analyzing clinical
samples due to high sample-to-sample variability in color and turbidity
and, in all likelihood, in composition. As a result, direct detection
in clinical samples was unreliable due to factors that may generally
affect assays based on plasmonic detection. Addition of a secondary
detection step overcame sample variability due to bulk differences
in patients’ sera. By those means, the SPR biosensor was successfully
applied to the analysis of clinical samples from leukemia patients
undergoing asparaginase treatments and the results agreed well with
the standard ELISA assay. Monitoring antibodies against drugs is common
such that this type of sensing scheme could serve to monitor a plethora
of immune responses in sera of patients undergoing treatment
Silver-Assisted Laser Desorption Ionization For High Spatial Resolution Imaging Mass Spectrometry of Olefins from Thin Tissue Sections
Silver
has been demonstrated to be a powerful cationization agent
in mass spectrometry (MS) for various olefinic species such as cholesterol
and fatty acids. This work explores the utility of metallic silver
sputtering on tissue sections for high resolution imaging mass spectrometry
(IMS) of olefins by laser desorption ionization (LDI). For this purpose,
sputtered silver coating thickness was optimized on an assorted selection
of mouse and rat tissues including brain, kidney, liver, and testis.
For mouse brain tissue section, the thickness was adjusted to 23 ±
2 nm of silver to prevent ion suppression effects associated with
a higher cholesterol and lipid content. On all other tissues, a thickness
of at 16 ± 2 nm provided the best desorption/ionization efficiency.
Characterization of the species by MS/MS showed a wide variety of
olefinic compounds allowing the IMS of different lipid classes including
cholesterol, arachidonic acid, docosahexaenoic acid, and triacylglyceride
52:3. A range of spatial resolutions for IMS were investigated from
150 μm down to the high resolution cellular range at 5 μm.
The applicability of direct on-tissue silver sputtering to LDI-IMS
of cholesterol and other olefinic compounds presents a novel approach
to improve the amount of information that can be obtained from tissue
sections. This IMS strategy is thus of interest for providing new
biological insights on the role of cholesterol and other olefins in
physiological pathways or disease
Dynamic-SERS Optophysiology: A Nanosensor for Monitoring Cell Secretion Events
We
monitored metabolite secretion near living cells using a plasmonic
nanosensor. The nanosensor created from borosilicate nanopipettes
analogous to the patch clamp was decorated with Au nanoparticles and
served as a surface-enhanced Raman scattering (SERS) substrate with
addressable location. With this nanosensor, we acquired SERS locally
near Madin-Darby canine kidney (MDCKII) epithelial cells, and we detected
multiple metabolites, such as pyruvate, lactate, ATP, and urea simultaneously.
These plasmonic nanosensors were capable of monitoring metabolites
in the extracellular medium with enough sensitivity to detect an increase
in metabolite concentration following the lyses of MDCKII cells with
a nonionic surfactant. The plasmonic nanosensors also allowed a relative
quantification of a chemical gradient for a metabolite near cells,
as demonstrated with a decrease in relative lactate to pyruvate concentration
further away from the MDCKII cells. This SERS optophysiology technique
for the sensitive and nondestructive monitoring of extracellular metabolites
near living cells is broadly applicable to different cellular and
tissue models and should therefore provide a powerful tool for cellular
studies
Tracking Silent Hypersensitivity Reactions to Asparaginase during Leukemia Therapy Using Single-Chip Indirect Plasmonic and Fluorescence Immunosensing
Microbial
asparaginase is an essential component of chemotherapy
for the treatment of childhood acute lymphoblastic leukemia (cALL).
Silent hypersensitivity reactions to this microbial enzyme need to
be monitored accurately during treatment to avoid adverse effects
of the drug and its silent inactivation. Here, we present a dual-response
anti-asparaginase sensor that combines indirect SPR and fluorescence
on a single chip to perform ELISA-type immunosensing, and correlate
measurements with classical ELISA. Analysis of serum samples from
children undergoing cALL therapy revealed a clear correlation between
single-chip indirect SPR/fluorescence immunosensing and ELISA used
in clinical settings (<i>R</i><sup>2</sup> > 0.9). We
also
report that the portable SPR/fluorescence system had a better sensitivity
than classical ELISA to detect antibodies in clinical samples with
low antigenicity. This work demonstrates the reliability of dual sensing
for monitoring clinically relevant antibody titers in clinical serum
samples
Development of Escherichia coli Asparaginase II for Immunosensing: A Trade-Off between Receptor Density and Sensing Efficiency
The clinical success
of Escherichia coli l-asparaginase
II (EcAII) as a front line chemotherapeutic
agent for acute lymphoblastic leukemia (ALL) is often compromised
because of its silent inactivation by neutralizing antibodies. Timely
detection of silent immune response can rely on immobilizing EcAII,
to capture and detect anti-EcAII antibodies. Having recently reported
the use of a portable surface plasmon resonance (SPR) sensing device
to detect anti-EcAII antibodies in undiluted serum from children undergoing
therapy for ALL (Aubé et al., <i>ACS Sensors</i> <b>2016</b>, <i>1</i> (11), 1358–1365), here we
investigate the impact of the quaternary structure and the mode of
immobilization of EcAII onto low-fouling SPR sensor chips on the sensitivity
and reproducibility of immunosensing. We show that the native tetrameric
structure of EcAII, while being essential for activity, is not required
for antibody recognition because monomeric EcAII is equally antigenic.
By modulating the mode of immobilization, we observed that low-density
surface coverage obtained upon covalent immobilization allowed each
tetrameric EcAII to bind up to two antibody molecules, whereas high-density
surface coverage arising from metal chelation by N- or C-terminal
histidine-tag reduced the sensing efficiency to less than one antibody
molecule per tetramer. Nonetheless, immobilization of EcAII by metal
chelation procured up to 10-fold greater surface coverage, thus resulting
in increased SPR sensitivity and allowing reliable detection of lower
analyte concentrations. Importantly, only metal chelation achieved
highly reproducible immobilization of EcAII, providing the sensing
reproducibility that is required for plasmonic sensing in clinical
samples. This report sheds light on the impact of multiple factors
that need to be considered to optimize the practical applications
of plasmonic sensors