Large-Scale Metabolite Analysis of Standards and Human Serum by Laser Desorption Ionization Mass Spectrometry from Silicon Nanopost Arrays.

The unique challenges presented by metabolomics have driven the development of new mass spectrometry (MS)-based techniques for small molecule analysis. We have previously demonstrated silicon nanopost arrays (NAPA) to be an effective substrate for laser desorption ionization (LDI) of small molecules for MS. However, the utility of NAPA-LDI-MS for a wide range of metabolite classes has not been investigated.

Molecular Imaging of Biological Samples on Nanophotonic Laser Desorption Ionization Platforms.

Mass spectrometry imaging (MSI) is a comprehensive tool for the analysis of a wide range of biomolecules. The mainstream method for molecular MSI is matrix-assisted laser desorption ionization, however, the presence of a matrix results in spectral interferences and the suppression of some analyte ions. Herein we demonstrate a new matrix-free MSI technique using nanophotonic ionization based on laser desorption ionization (LDI) from a highly uniform silicon nanopost array (NAPA).

In Vitro Spoilation of Silicone-Hydrogel Soft Contact Lenses in a Model-Blink Cell.

Purpose: We developed an in vitro model-blink cell that reproduces the mechanism of in vivo fouling of soft contact lenses. In the model-blink cell, model tear lipid directly contacts the lens surface after forced aqueous rupture, mirroring the pre-lens tear-film breakup during interblink.

Methods: Soft contact lenses are attached to a Teflon holder and immersed in artificial tear solution with protein, salts, and mucins.

Reversal of mitochondrial proteomic loss in Type 1 diabetic heart with overexpression of phospholipid hydroperoxide glutathione peroxidase.

Mitochondrial dysfunction is a contributor to diabetic cardiomyopathy. Previously, we observed proteomic decrements within the inner mitochondrial membrane (IMM) and matrix of diabetic cardiac interfibrillar mitochondria (IFM) correlating with dysfunctional mitochondrial protein import. The goal of this study was to determine whether overexpression of mitochondria phospholipid hydroperoxide glutathione peroxidase 4 (mPHGPx), an antioxidant enzyme capable of scavenging membrane-associated lipid peroxides in the IMM, could reverse proteomic alterations, dysfunctional protein import, and ultimately, mitochondrial dysfunction associated with the diabetic heart.

Rapid, non-targeted discovery of biochemical transformation and biomarker candidates in oncovirus-infected cell lines using LAESI mass spectrometry.

Finding insights into how viruses hijack metabolic processes and biomarkers for viral diseases often require hypotheses about target compounds and/or labelling techniques. Here we present a method based on laser ablation electrospray ionization mass spectrometry to rapidly identify potential protein and metabolite biomarkers of oncovirus infection in B lymphocytes.

Proteomic alterations of distinct mitochondrial subpopulations in the type 1 diabetic heart: contribution of protein import dysfunction.

Diabetic cardiomyopathy is associated with increased risk of heart failure in type 1 diabetic patients. Mitochondrial dysfunction is suggested as an underlying contributor to diabetic cardiomyopathy. Cardiac mitochondria are characterized by subcellular spatial locale, including mitochondria located beneath the sarcolemma, subsarcolemmal mitochondria (SSM), and mitochondria situated between the myofibrils, interfibrillar mitochondria (IFM).

A general approach to anionic acid-labile surfactants with tunable properties.

A general approach to the synthesis of a new series of unique sulfate anionic acid-labile surfactants (AALS) was developed. In this approach, the ketal was derived from methyl pyruvate, and the sulfate motif was introduced via sulfitylation of the alcohol, oxidation, and finally conversion of the sulfate diester to the desired sodium salt. The physicochemical properties in aqueous solution of this novel series of surfactants, such as CMCs, solubility, acid lability, and stability were studied.

Mitochondrial dysfunction in the type 2 diabetic heart is associated with alterations in spatially distinct mitochondrial proteomes.

Cardiac complications and heart failure are the leading cause of death in type 2 diabetic patients. Mitochondrial dysfunction is central in the pathogenesis of the type 2 diabetic heart. However, it is unclear whether this dysfunction is specific for a particular subcellular region.

Development of a microfluidics-based gel protein recovery system.

A PMMA microfluidic chip, in which fluid is manipulated to transport protein from a PAGE gel piece to a collection reservoir via a microfluidic channel, has been developed. The protein sample is mobilized out of the gel (loaded in a chip access hole) into a low EOF-CE microfluidic channel under the influence of an electric field. Simultaneously, hydrostatic pressure from the filled buffer reservoirs is used to direct the protein sample to a third reservoir, through a field-free channel connected to the electrophoresis channel.

Nanophotonic ion production from silicon microcolumn arrays.

Nanoantennas for ions: Silicon microcolumn arrays harvest light from a laser pulse to produce ions. The system behaves like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of polarization and the angle of incidence of the laser beam. Photonic ion sources promise to enable enhanced control of ion production on a micro- and nanometer scale and direct integration with miniaturized analytical devices.

ESI-MS compatible permanent coating of glass surfaces using poly(ethylene glycol)-terminated alkoxysilanes for capillary zone electrophoretic protein separations.

Thin poly(ethylene glycol) silane (PEG-silane) coatings formed from N-(triethoxysilyl propyl)-O-poly(ethylene oxide) urethane with different chain lengths of poly(ethylene glycol) (MW 750 and 4000-5000) are used to modify glass microfluidic channels and fused-silica capillaries for electrophoretic separations of proteins. These coatings combine three important properties, which make them favorable for proteomic analyses including reduction of protein adsorption, compatibility with mass spectrometry due to their stability, and the ability to control the magnitude of electroosmotic flow (EOF). The coatings have been successfully used in microfluidic chips and fused-silica capillaries for separation of protein sample mixtures under low EOF conditions.

Interfacing microchip capillary electrophoresis with electrospray ionization mass spectrometry.

Microfluidic devices are a unique enabling technology for chemical separations, modification, and synthesis that are ideally suited for the manipulation of low volume samples on the order of a few nanoliters in volume. Complex patterns of capillary-sized channels with zero dead volume connections are the distinguishing features of many microfluidic devices. Concurrently, mass spectrometry has undergone further development, and is now arguably the method of choice for structural characterization of mass- and volume-limited samples.

An electrokinetic/hydrodynamic flow microfluidic CE-ESI-MS interface utilizing a hydrodynamic flow restrictor for delivery of samples under low EOF conditions.

A hydrodynamic flow restrictor (HDR) that is used to combine electrokinetic and hydrodynamic flow streams has been fabricated in a microfluidic channel by laser micromachining. Combining electrokinetic and hydrodynamic flow streams is challenging in microfluidic devices, because the hydrodynamic flow often overpowers the electrokinetic flow, making it more difficult to use low electroosmotic flow in the electrokinetic portion of the system. The HDR has been incorporated into a capillary electrophoresis-mass spectrometry interface that provides continuous introduction of a make-up solution and negates the hydrodynamic backpressure in the capillary electrophoresis channel to the extent that low EOF can be utilized.

Fabrication and characterization of a fritless microfabricated electroosmotic pump with reduced pH dependence.

A fritless electroosmotic pump with reduced pH dependence has been fabricated on a glass microchip and its performance characterized. The chip design consists of two 500-microm channels, one packed with anion exchange beads and the other packed with cation exchange beads, which produce convergent electroosmotic flow streams. The electroosmotically pumped solution flows away from the intersection of the two pumping channels through a field-free channel.