Localization and Quantification of Drugs in Animal Tissues by Use of Desorption Electrospray Ionization Mass Spectrometry Imaging

Mass spectrometric imaging (MSI) has emerged as a powerful technique to obtain spatial arrangement of individual molecular ions in animal tissues. Ambient desorption electrospray ionization (DESI) technique is uniquely suited for such imaging experiments, as it can be performed on animal tissues in their native environment without prior treatments. Although MSI has become a rapid growing technique for localization of proteins, lipids, drugs, and endogenous compounds in different tissues, quantification of imaged targets has not been explored extensively. Here we present a novel MSI approach for localization and quantification of drugs in animal thin tissue sections. DESI-MSI using an Orbitrap mass analyzer in full scan mode was performed on 6 μm coronal brain sections from rats that were administered 2.5 mg/kg clozapine. Clozapine was localized and quantified in individual brain sections 45 min postdose. External calibration curves were prepared by micropipetting standards with internal standard (IS) on top of the tissues, and average response factors were calculated for the scans in which both clozapine and IS were detected. All response factors were normalized to area units. Quantifications from DESI-MSI revealed 0.2–1.2 ng of clozapine in individual brain sections, results that were further confirmed by extraction and liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis

Enhanced Impact Resistance of Three-Dimensional-Printed Parts with Structured Filaments

Net-shape manufacture of customizable objects through three-dimensional (3D) printing offers tremendous promise for personalization to improve the fit, performance, and comfort associated with devices and tools used in our daily lives. However, the application of 3D printing in structural objects has been limited by their poor mechanical performance that manifests from the layer-by-layer process by which the part is produced. Here, this interfacial weakness is overcome using a structured, core–shell polymer filament where a polycarbonate (PC) core solidifies quickly to define the shape, whereas an olefin ionomer shell contains functionality (crystallinity and ionic) that strengthen the interface between the printed layers. This structured filament leads to improved dimensional accuracy and impact resistance in comparison to the individual components. The impact resistance from structured filaments containing 45 vol % shell can exceed 800 J/m. The origins of this improved impact resistance are probed using X-ray microcomputed tomography. Energy is dissipated by delamination of the shell from PC near the crack tip, whereas PC remains intact to provide stability to the part after impact. This structured filament provides tremendous improvements in the critical properties for manufacture and represents a major leap forward in the impact properties obtainable for 3D-printed parts

Rheological Behavior of Tough PVP-<i>in Situ</i>-PAAm Hydrogels Physically Cross-Linked by Cooperative Hydrogen Bonding

Rheology studies were performed on tough PVP-<i>in situ</i>-PAAm hydrogels physically cross-linked by cooperative hydrogen bonding to understand their viscoelastic response and, hence, the interactions and microstructure. The viscoelasticity of the PVP-<i>in situ</i>-PAAm hydrogels was strongly affected by the monomer ratio (<i>C</i>_AAm/<i>C</i>_VP). Hydrogels prepared with a high monomer ratio exhibited weak time, temperature and frequency dependence of the viscoelastic properties, similar to those of chemically cross-linked hydrogels. The storage modulus (<i>G</i>′) of the gels was much greater than the loss moduli (<i>G</i>″) and low loss factor (tan δ < ∼ 0.1), which indicated that they were solid-like, and mostly elastic. These supramolecular gels exhibited a strain- and <i>C</i>_AAm/<i>C</i>_VP-dependent reversible gel (solid) to viscoelastic liquid transition due to the dynamic nature of the cooperative hydrogen bonds. That transition also coincided with the onset of nonlinear viscoelastic behavior. The addition of a low molecular weight compound, urea, that competes for hydrogen bonding sites weakens the gel by decreasing the effective cross-link density or weakening the intermolecular hydrogen bonding

Three-Dimensional Printed Shape Memory Objects Based on an Olefin Ionomer of Zinc-Neutralized Poly(ethylene-<i>co</i>-methacrylic acid)

Three-dimensional printing enables the net shape manufacturing of objects with minimal material waste and low tooling costs, but the functionality is generally limited by available materials, especially for extrusion-based printing, such as fused deposition modeling (FDM). Here, we demonstrate shape memory behavior of 3D printed objects with FDM using a commercially available olefin ionomer, Surlyn 9520, which is zinc-neutralized poly­(ethylene-<i>co</i>-methacrylic acid). The initial fixity for 3D printed and compression-molded samples was similar, but the initial recovery was much lower for the 3D printed sample (<i>R</i> = 58%) than that for the compression-molded sample (<i>R</i> = 83%). The poor recovery in the first cycle is attributed to polyethylene crystals formed during programming that act to resist the permanent network recovery. This effect is magnified in the 3D printed part due to the higher strain (lower modulus in the 3D printed part) at a fixed programming stress. The fixity and recovery in subsequent shape memory cycles are greater for the 3D printed part than for the compression-molded part. Moreover, the programmed strain can be systematically modulated by inclusion of porosity in the printed part without adversely impacting the fixity or recovery. These characteristics enable the direct formation of complex shapes of thermoplastic shape memory polymers that can be recovered in three dimensions with the appropriate trigger, such as heat, through the use of FDM as a 3D printing technology

Three-Dimensional Printed Shape Memory Objects Based on an Olefin Ionomer of Zinc-Neutralized Poly(ethylene-<i>co</i>-methacrylic acid)

Three-dimensional printing enables the net shape manufacturing of objects with minimal material waste and low tooling costs, but the functionality is generally limited by available materials, especially for extrusion-based printing, such as fused deposition modeling (FDM). Here, we demonstrate shape memory behavior of 3D printed objects with FDM using a commercially available olefin ionomer, Surlyn 9520, which is zinc-neutralized poly­(ethylene-<i>co</i>-methacrylic acid). The initial fixity for 3D printed and compression-molded samples was similar, but the initial recovery was much lower for the 3D printed sample (<i>R</i> = 58%) than that for the compression-molded sample (<i>R</i> = 83%). The poor recovery in the first cycle is attributed to polyethylene crystals formed during programming that act to resist the permanent network recovery. This effect is magnified in the 3D printed part due to the higher strain (lower modulus in the 3D printed part) at a fixed programming stress. The fixity and recovery in subsequent shape memory cycles are greater for the 3D printed part than for the compression-molded part. Moreover, the programmed strain can be systematically modulated by inclusion of porosity in the printed part without adversely impacting the fixity or recovery. These characteristics enable the direct formation of complex shapes of thermoplastic shape memory polymers that can be recovered in three dimensions with the appropriate trigger, such as heat, through the use of FDM as a 3D printing technology

General Approach to the Synthesis of Metal Hybrid Carbon/Titania Aerogel for the Oxygen Reduction Reaction

A mass production route to catalysts for the oxygen reduction reaction (ORR) is crucial for their end-use application. To date, the direct manufacture of ORR catalysts through simple and economic manufacturing routes remains a challenge, with current approaches relying on convoluted processes using expensive components. Here, a straightforward and cost-effective method is developed to fabricate metal hybrid carbon/titania composite aerogels (CTA-M) as ORR catalysts, which was obtained via carbonizing metal hybrid resorcinol–formaldehyde (RF)/titania composite aerogels at 900 °C in an inert atmosphere. The effect of metal nitrate, including La, Sm, Zr, Cr, Fe, and Cu nitrates, on the structure and ORR performance was investigated. The high porosity and specific surface area enabled CTA-M with a high mass transfer performance. The high asymmetry of anatase leads to the presence of oxygen vacancies in the crystal structure of CTA-M, which maintains the electrostatic equilibrium of the crystal structure, which verifies that the catalytic activity of anatase is superior to that of rutile, whereas the non-homogeneous product enhances the electrical conductivity, which further affects the catalytic activity of the ORR. Trace metal doping can modulate the electronic structure and composition of CTA-M. Iron nitrate doping carbon/titania aerogel (CTA-Fe-A) showed the best pore structure and oxygen adsorption performance. The specific surface area and pore volume of CTA-Fe-A were 720 m2 g–1 and 1.12 cm3 g–1, respectively. The onset potential, half-wave potential, and ultimate current density were 0.82 V, 0.74 V, and 4.96 mA cm–2, respectively. It is expected that this synthesis technique and the resulting CTA-M could be used as a method for large-scale commercial production of ORR catalysts, thus enabling the use of these materials in a broad spectrum of industrial applications