10 research outputs found
Fabrication of a Micro-omnifluidic Device by Omniphilic/Omniphobic Patterning on Nanostructured Surfaces
We integrate the adhesive properties of marine mussels, the lubricating properties of pitcher plants, and the nonfouling properties of diatoms into nanostructured surfaces to develop a device called a micro-omnifluidic (μ-OF) system to solve the existing challenges in microfluidic systems. Unlike conventional poly(dimethylsiloxane)-based fluidic systems that are incompatible with most organic solvents, the μ-OF system utilizes a variety of solvents such as water, ethanol, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, <i>n</i>-hexane, 1,2-dichloroethane, acetic acid, 2-propanol, acetone, toluene, diesel oil, dioxane, gasoline oil, hexadecane, and xylene. The μ-OF system is based on a phenomenon called microchannel induction that spontaneously occurs when virtually all droplets of solvents are applied on omniphilically micropatterned regions of a slippery liquid-infused porous surface. Any solvents with surface tension greater than that of the lubricant (17.1 mN/m, Fluorinert FC-70) are able to repel the infused lubricant located on top of the omniphilic microlines, triggering controlled movement of the droplet by gravity along the microlines. We also demonstrated that the μ-OF system is reusable by the nonadsorption properties of the silicified layer. Due to the organic solvent compatibility, we were able to perform organic reactions with high portability and energy efficiency in operation
Visualization 3: Real-time GPU-accelerated processing and volumetric display for wide-field laser-scanning optical-resolution photoacoustic microscopy
Image distortion and changes of shapes and intensities owing to breathing or momentary movement Originally published in Biomedical Optics Express on 01 December 2015 (boe-6-12-4650
Visualization 2: Real-time GPU-accelerated processing and volumetric display for wide-field laser-scanning optical-resolution photoacoustic microscopy
MAP OR-PAM image of a BALB/c-nude mouse's ear Originally published in Biomedical Optics Express on 01 December 2015 (boe-6-12-4650
b<sub>2</sub> Peaks in SERS Spectra of 4‑Aminobenzenethiol: A Photochemical Artifact or a Real Chemical Enhancement?
Strong
b<sub>2</sub> peaks (1142, 1391, 1438, and 1583 cm<sup>–1</sup>) in the SERS spectra of 4-aminobenzenethiol (ABT) have been regarded
by many as a textbook example of chemically enhanced SERS signals.
However, this interpretation is in serious doubt after the recent
claim that they arise from 4,4′-dimercaptoazobenzenes (DMAB)
photogenerated during the acquisition of SERS, not the genuine chemically
enhanced signals of ABT. Subsequent attempts to prove or disprove
this claim have failed to provide any decisive verdict. Here we present
spectroscopic and mass spectrometric evidence that further support
the photogeneration of DMABs from ABTs on an Ag surface. Furthermore,
we show that the amount of the DMAB is sufficient to explain the b<sub>2</sub> intensities of ABT
On-Chip Peptide Mass Spectrometry Imaging for Protein Kinase Inhibitor Screening
Protein
kinases are enzymes that are important targets for drug discovery
because of their involvement in regulating the essential cellular
processes. For this reason, the changes in protein kinase activity
induced by each drug candidate (the inhibitor in this case) need to
be accurately determined. Here, an on-chip secondary ion mass spectrometry
(SIMS) imaging technique of the peptides was developed for determining
protein kinase activity and inhibitor screening without a matrix.
In our method, cysteine-tethered peptides adsorbed onto a gold surface
produced changes in the relative peak intensities of the phosphorylated
and unphosphorylated substrate peptides, which were quantitatively
dependent on protein kinase activity. Using mass spectrometry imaging
of multiple compartments on the gold surface in the presence of a
peptide substrate, we screened 13,727 inhibitors, of which seven were
initially found to have inhibitor efficiencies that surpassed 50%.
Of these, we were able to identify a new breakpoint cluster region-abelson
(BCR-ABL)<sup>T315I</sup> kinase inhibitor, henceforth referred to
as KR135861. KR135861 showed no cytotoxicity and was subsequently
confirmed to be superior to imatinib, a commercial drug marketed as
Gleevec. Moreover, KR135861 exhibited a greater inhibitory effect
on the BCR-ABL<sup>T315I</sup> tyrosine kinase, with an IC<sub>50</sub> value as low as 1.3 μM. In in vitro experiments, KR135861
reduced the viability of both Ba/F3 cells expressing wild-type BCR-ABL
and BCR-ABL<sup>T315I</sup>, in contrast to imatinib’s inhibitory
effects only on Ba/F3 cells expressing wild-type BCR-ABL. Due to the
surface sensitivity and selectivity of SIMS imaging, it is anticipated
that our approach will make it easier to validate the small modifications
of a substrate in relation to enzyme activity as well as for drug
discovery. This mass spectrometry imaging analysis enables efficient
screening for protein kinase inhibitors, thus permitting high-throughput
drug screening with high accuracy, sensitivity, and specificity
Stacked Gold Nanodisks for Bimodal Photoacoustic and Optical Coherence Imaging
Herein,
we report on biological imaging nanoprobes: physically
synthesized gold nanodisks that have inherent optical advantagesa
wide range of resonant wavelengths, tunable ratio of light absorption-to-scattering,
and responsiveness to random incident lightdue to their two-dimensional
circular nanostructure. Based on our proposed physical synthesis where
gold is vacuum deposited onto a prepatterned polymer template and
released from the substrate in the form of a nanodisk, monodisperse
two-dimensional gold nanodisks were prepared with independent control
of their diameter and thickness. The optical benefits of the Au nanodisk
were successfully demonstrated by the measurement of light absorbance
of the nanodisks and the application of stacked nanodisks, where a
smaller sized Au nanodisk was laid atop a larger nanodisk, as bimodal
contrast agents for photoacoustic microscopy and optical coherence
tomography
CRISPR/Cas-Assisted Colorimetric Biosensor for Point-of-Use Testing for African Swine Fever Virus
African swine fever
virus (ASFV) causes a highly contagious and
fatal disease affecting both domesticated and wild pigs. Substandard
therapies and inadequate vaccinations cause severe economic damages
from pig culling and removal of infected carcasses. Therefore, there
is an urgent need to develop a rapid point-of-use approach that assists
in avoiding the spread of ASFV and reducing economic loss. In this
study, we developed a colorimetric sensing platform based on dual
enzymatic amplification that combined the clustered regularly interspaced
short palindromic repeats (CRISPR)/CRISPR-associated protein 12a (Cas12a)
system and the enzyme urease for accurate and sensitive detection
of ASFV. The mechanism of the sensing platform involves a magnetic
bead-anchored urease-conjugated single-stranded oligodeoxynucleotide
(MB@urODN), which in the presence of ASFV dsDNA is cleaved by activated
CRISPR/Cas12a. After magnetically separating the free urease, the
presence of virus can be confirmed by measuring the colorimetric change
in the solution. The advantage of this method is that it can detect
the presence of virus without undergoing a complex target gene duplication
process. The established method detected ASFV from three clinical
specimens collected from porcine clinical tissue samples. The proposed
platform is designed to provide an adequate, simple, robust, highly
sensitive and selective analytical technique for rapid zoonotic disease
diagnosis while eliminating the need for vast or specialized tools
Electrochemical Release of Amine Molecules from Carbamate-Based, Electroactive Self-Assembled Monolayers
In this paper, carbamate-based self-assembled monolayers (SAMs) of alkanethiolates on gold were suggested as a versatile platform for release of amine-bearing molecules in response to the electrical signal. The designed SAMs underwent the electrochemical oxidation on the gold surface with simultaneous release of the amine molecules. The synthesis of the thiol compounds was achieved by coupling isocyanate-containing compounds with hydroquinone. The electroactive thiol was mixed with 11-mercaptoundecanol [HS(CH<sub>2</sub>)<sub>11</sub>OH] to form a mixed monolayer, and cyclic votammetry was used for the characterization of the release behaviors. The mixed SAMs showed a first oxidation peak at +540 mV (versus Ag/AgCl reference electrode), indicating the irreversible conversion from carbamate to hydroquinone groups with simultaneous release of the amine molecules. The analysis of ToF-SIMS further indicated that the electrochemical reaction on the gold surface successfully released amine molecules
Characterizing Nanoparticle Mass Distributions Using Charge-Independent Nanoresonator Mass Spectrometry
Due to their unique size-dependent properties, nanoparticles
(NPs)
have many industrial and biomedical applications. Although NPs are
generally characterized based on the size or morphological analysis,
the mass of whole particles can be of interest as it represents the
total amount of material in the particle regardless of shape, density,
or elemental composition. In addition, the shape of nonspherical NPs
presents a conceptual challenge, making them difficult to characterize
in terms of size or morphological characteristics. Here, we used a
novel nano-electro-mechanical sensor mass spectrometry (NEMS-MS) technology
to characterize the mass distributions of various NPs. For standard
spherical gold NPs, mass distributions covered the range from ∼5
to 250 MDa (8 to ∼415 attograms). Applying the density of gold
(19.3 g/cm3) and assuming perfect sphericity, these mass
measurements were used to compute the equivalent diameters of the
NPs. The sizes determined agreed well with the transmission electron
microscopy (TEM) imaging data, with deviations of ∼1.4%. Subsequently,
we analyzed the mass distribution of ∼50 nm synthetic silicon
dioxide particles, having determined their size by electron microscopy
(SEM and TEM). Their estimated density was in line with the literature
values derived from differential mobility analyzer and aerosol particle
mass analyzer data. Finally, we examined the intact gold nanotetrapods
and obtained a mass distribution revealing their controlled polydispersity.
The presence of polyethylene glycol coating was also quantified and
corroborated nuclear magnetic resonance observations. Our results
demonstrate the potential of NEMS-MS-based measurements as an effective
means to characterize NPs, whatever their composition, shape or density
Measuring Compositions in Organic Depth Profiling: Results from a VAMAS Interlaboratory Study
We report the results of a VAMAS
(Versailles Project on Advanced
Materials and Standards) interlaboratory study on the measurement
of composition in organic depth profiling. Layered samples with known
binary compositions of Irganox 1010 and either Irganox 1098 or Fmoc-pentafluoro-l-phenylalanine in each layer were manufactured in a single
batch and distributed to more than 20 participating laboratories.
The samples were analyzed using argon cluster ion sputtering and either
X-ray photoelectron spectroscopy (XPS) or time-of-flight secondary
ion mass spectrometry (ToF-SIMS) to generate depth profiles. Participants
were asked to estimate the volume fractions in two of the layers and were provided with the compositions of all other layers. Participants using XPS provided volume fractions within 0.03 of the nominal values. Participants using ToF-SIMS either made no attempt, or used various methods that gave results ranging in error from 0.02 to over 0.10 in volume fraction, the latter representing a 50% relative error for a nominal volume fraction of 0.2. Error was predominantly caused by inadequacy in the ability to compensate for primary ion intensity variations and the matrix effect in SIMS. Matrix effects in these materials appear to be more pronounced as the number of atoms in both the primary analytical ion and the secondary ion increase. Using the participants’ data we show that organic SIMS matrix effects can be measured and are remarkably consistent between instruments. We provide recommendations for identifying and compensating for matrix effects. Finally, we demonstrate, using a simple normalization method, that virtually all ToF-SIMS participants could have obtained estimates of volume fraction that were at least as accurate and consistent as XPS