Jonas Baltrusaitis

The Development of Electrically Conductive Polycaprolactone Fumarate-Polypyrrole Composite Materials for Nerve Regeneration

Electrically conductive polymer composites composed of polycaprolactone fumarate and polypyrrole (PCLF-PPy) have been developed for nerve regeneration applications. Here we report the synthesis and characterization of PCLF-PPy and in vitro studies showing PCLF-PPy materials support both PC12 cell and dorsal root ganglia (DRG) neurite extension. PCLF-PPy composite materials were synthesized by polymerizing pyrrole in preformed PCLF scaffolds (M(n) 7,000 or 18,000 g mol(-1)) resulting in interpenetrating networks of PCLF-PPy. Chemical compositions and thermal properties were characterized by ATR-FTIR, XPS, DSC, and TGA. PCLF-PPy materials were synthesized with five different anions (naphthalene-2-sulfonic acid sodium salt (NSA), dodecylbenzenesulfonic acid sodium salt (DBSA), dioctyl sulfosuccinate sodium salt (DOSS), potassium iodide (I), and lysine) to investigate effects on electrical conductivity and to optimize chemical composition for cellular compatibility. PCLF-PPy materials have variable electrical conductivity up to 6 mS cm(-1) with bulk compositions ranging from 5 to 13.5 percent polypyrrole. AFM and SEM characterization show microstructures with a root mean squared (RMS) roughness of 1195 nm and nanostructures with RMS roughness of 8 nm. In vitro studies using PC12 cells and DRG show PCLF-PPy materials synthesized with NSA or DBSA support cell attachment, proliferation, neurite extension, and are promising materials for future studies involving electrical stimulation.

Induction of Inflammasome-dependent Pyroptosis by Carbon Black Nanoparticles

Inhalation of nanoparticles has been implicated in respiratory morbidity and mortality. In particular, carbon black nanoparticles are found in many different environmental exposures. Macrophages take up inhaled nanoparticles and respond via release of inflammatory mediators and in some cases cell death. Based on new data, we propose that exposure of macrophages (both a macrophage cell line and primary human alveolar macrophages) to carbon black nanoparticles induces pyroptosis, an inflammasome-dependent form of cell death. Exposure of macrophages to carbon black nanoparticles resulted in inflammasome activation as defined by cleavage of caspase 1 to its active form and downstream IL-1β release. The cell death that occurred with carbon black nanoparticle exposure was identified as pyroptosis by the protective effect of a caspase 1 inhibitor and a pyroptosis inhibitor. These data demonstrate that carbon black nanoparticle exposure activates caspase 1, increases IL-1β release after LPS priming, and induces the proinflammatory cell death, pyroptosis. The identification of pyroptosis as a cellular response to carbon nanoparticle exposure is novel and relates to environmental and health impacts of carbon-based particulates.

A template-free, thermal decomposition method to synthesize mesoporous MgO with a nanocrystalline framework and its application in carbon dioxide adsorption

Alkaline earth-based oxides are important materials in the storage of carbon dioxide. Here we present a template-free synthesis method for mesoporous magnesium oxide (MgO) via the thermal decomposition of anhydrous magnesium acetate. Characterization of the crystalline phase, particle size, pore size and surface area for mesoporous MgO samples was accomplished using a variety of techniques and methods including scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), and nitrogen adsorption analysis. The results showed that mesoporous MgO prepared from anhydrous magnesium acetate had a high surface area in the range of 120–136 m2 g−1 and a narrow pore size distribution in the range of 3–4 nm. The pore structure was composed of small primary MgO nanoparticle aggregates with interparticle connections. In situ transmission FTIR spectroscopy was used to investigate CO2 adsorption on mesoporous MgO. This spectroscopic investigation showed that mesoporous MgO exhibited enhanced CO2 adsorption capacity relative to commercially available MgO nanoparticles. This difference was attributed mainly to an increase in surface area. Differences in surface carbonate/bicarbonate speciation were observed between the mesoporous and commercial MgO samples and were related to structural differences for the smaller nanoparticles.

Supramolecular Catalysis in the Organic Solid State through Dry Grinding

[Figure Presented] Chemical mechanics: Hydrogen-bonddriven self-assembly and mechanochemistry are used to facilitate supramolecular catalysis in the solid state. Mortar-andpestle grinding proves to be an efficient means to achieve co-crystal formation and turnover using a physical mixture composed of an olefin and catalytic amounts of a ditopic template (see scheme).

Thixotropic Hydrogel Derived from a Product of an Organic Solid-State Synthesis: Properties and Densities of Metal-Organic Nanoparticles

Metallogels form from Cu(II) ions and tetratopic ligand rctt-1,2-bis(3-pyridyl)-3,4-bis(4-pyridyl)cyclobutane. The tetrapyridyl cyclobutane has been synthesized in the organic solid state. The gel forms with a variety of counteranions and gels water. The hydrogel is thixotropic and is composed of nanoscale metal-organic particles (NMOPs), a high surface area of which likely accounts for the gelation of the polar aqueous medium. A shear stress profile of the thixotropic hydrogel gave a yield value of 8.33 Pa. A novel combination of atomic force microscopy (AFM) and scanning transmission X-ray microscopy (STXM) is used to assess the densities of individual NMOPs. A density of 1.37 g/cm(3) has been determined. A single-crystal X-ray diffraction study demonstrates the ability of the unsymmetrical cyclobutane 3,4-tpcb to self-assemble with Cu(II) ions in [Cu(2)(hfac)(4)(3,4-tpcb)](∞) (where hfac is hexafluoroacetylacetonate) to form a solvated 1D coordination polymer.

Development of Electrically Conductive Oligo(polyethylene Glycol) Fumarate-Polypyrrole Hydrogels for Nerve Regeneration

Electrically conductive hydrogel composites consisting of oligo(polyethylene glycol) fumarate (OPF) and polypyrrole (PPy) were developed for applications in nerve regeneration. OPF-PPy scaffolds were synthesized using three different anions: naphthalene-2-sulfonic acid sodium salt (NSA), dodecylbenzenesulfonic acid sodium salt (DBSA), and dioctyl sulfosuccinate sodium salt (DOSS). Scaffolds were characterized by ATR-FTIR, XPS, AFM, dynamic mechanical analysis, electrical resistivity measurements, and swelling experiments. OPF-PPy scaffolds were shown to consist of up to 25 mol % polypyrrole with a compressive modulus ranging from 265 to 323 kPa and a sheet resistance ranging from 6 to 30 × 10(3) Ohms/square. In vitro studies using PC12 cells showed OPF-PPy materials had no cytotoxicity and PC12 cells showed distinctly better cell attachment and an increase in the percent of neurite bearing cells on OPF-PPy materials compared to OPF. The neurite lengths of PC12 cells were significantly higher on OPF-PPyNSA and OPF-PPyDBSA. These results show that electrically conductive OPF-PPy hydrogels are promising candidates for future applications in nerve regeneration.

Water Adsorption on Clay Minerals As a Function of Relative Humidity: Application of BET and Freundlich Adsorption Models

Water adsorption on kaolinite, illite, and montmorillonite clays was studied as a function of relative humidity (RH) at room temperature (298 K) using horizontal attenuated total reflectance (HATR) Fourier transform infrared (FTIR) spectroscopy equipped with a flow cell. The water content as a function of RH was modeled using the Brunauer, Emmett, and Teller (BET) and Freundlich adsorption isotherm models to provide complementary multilayer adsorption analysis of water uptake on the clays. A detailed analysis of model fit integrity is reported. From the BET fit to the experimental data, the water content on each of the three clays at monolayer (ML) water coverage was determined and found to agree with previously reported gravimetric data. However, BET analysis failed to adequately describe adsorption phenomena at RH values greater than 80%, 50%, and 70% RH for kaolinite, illite, and montmorillonite clays, respectively. The Freundlich adsorption model was found to fit the data well over the entire range of RH values studied and revealed two distinct water adsorption regimes. Data obtained from the Freundlich model showed that montmorillonite has the highest water adsorption strength and highest adsorption capacity at RH values greater than 19% (i.e., above ML water adsorption) relative to the kaolinite and illite clays. The difference in the observed water adsorption behavior between the three clays was attributed to different water uptake mechanisms based on a distribution of available adsorption sites. It is suggested that different properties drive water adsorption under different adsorption regimes resulting in the broad variability of water uptake mechanisms.

Influenza A Viral Replication Is Blocked by Inhibition of the Inositol-requiring Enzyme 1 (IRE1) Stress Pathway

Background: The role of endoplasmic reticulum (ER) stress in influenza A viral infection is unknown. Results: Influenza A virus induces the IRE1 pathway of the ER stress response. Inhibition of IRE1 activity leads to decreased viral replication. Conclusion: IRE1 is a potential therapeutic target for influenza A virus. Significance: Targeting a host molecular mechanism is a novel therapeutic strategy that is less likely to be invalidated by viral mutagenesis. Known therapies for influenza A virus infection are complicated by the frequent emergence of resistance. A therapeutic strategy that may escape viral resistance is targeting host cellular mechanisms involved in viral replication and pathogenesis. The endoplasmic reticulum (ER) stress response, also known as the unfolded protein response (UPR), is a primitive, evolutionary conserved molecular signaling cascade that has been implicated in multiple biological phenomena including innate immunity and the pathogenesis of certain viral infections. We investigated the effect of influenza A viral infection on ER stress pathways in lung epithelial cells. Influenza A virus induced ER stress in a pathway-specific manner. We showed that the virus activates the IRE1 pathway with little or no concomitant activation of the PERK and the ATF6 pathways. When we examined the effects of modulating the ER stress response on the virus, we found that the molecular chaperone tauroursodeoxycholic acid (TUDCA) significantly inhibits influenza A viral replication. In addition, a specific inhibitor of the IRE1 pathway also blocked viral replication. Our findings constitute the first evidence that ER stress plays a role in the pathogenesis of influenza A viral infection. Decreasing viral replication by modulating the host ER stress response is a novel strategy that has important therapeutic implications.

Semiconducting Organic Assemblies Prepared from Tetraphenylethylene Tetracarboxylic Acid and Bis(pyridine)s via Charge-Assisted Hydrogen Bonding

Principles of crystal engineering have been applied toward the construction of supramolecular assemblies between an acid-functionalized tetraphenylethylene derivative and three different bis(pyridine)s [4,4-bis(pyridyl)ethylene, 4,4-bis(pyridyl)ethane, and 4,4-bipyridine]. Each assembly was structurally characterized, and charge transfer interactions within each sample were visually apparent. Quantum chemical calculations were used to determine crystal band structure and band gap magnitude, and electrical properties of the materials were measured using conducting probe atomic force microscopy (CP-AFM). The crystals displayed charge-carrier capability, and the magnitude of semiconductivity varied systematically as a function of conjugation in the bis(pyridine) component. Crystals incorporating 4,4-bis(pyridyl)ethylene and 4,4-bipyridine displayed conductivities comparable to those of established organic semiconductors (μ(eff) = 0.38 and 1.7 × 10(-2) cm(2)/V·s, respectively).

Visible light driven photocatalytic evolution of hydrogen from water over CdS encapsulated MCM-48 materials

CdS encapsulated cubic MCM-48 mesoporous photocatalysts were prepared by a post-impregnation method. Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption isotherm, UV-visible diffuse reflectance spectroscopy (DRS), FT-IR spectrometry, X-ray photoelectron spectroscopy (XPS), atomic absorption spectroscopy (AAS), and photoluminescence (PL) spectroscopy were employed for the characterization of the CdS incorporated MCM-48 siliceous materials. MCM-48 was loaded with different amounts of CdS. In the current study, all the samples showed photocatalytic activity under visible light (λ > 400 nm) irradiation for production of hydrogen from splitting of water in the absence of Pt, which is usually used in photocatalytic splitting of water. The photocatalytic activity of the CdS incorporated MCM-48 mesoporous photocatalysts was found to be dependent on the CdS loading and the pore size of MCM-48 siliceous support. The highest solar hydrogen evolution rate by visible light irradiation from the splitting of water was determined to be 1.81 mmol h−1 gCdS−1 and the apparent quantum yield was estimated to be 16.6%.