Tailoring the (bio)activity of polymeric and metal oxide nano- and microparticles in biotic and abiotic environments

Polymeric and metal oxide micro- and nanoparticles are being increasingly introduced into biomedical applications such as tissue engineering as well as in consumer products, which has boosted extensive research towards developing predictive paradigms of their (bio-)activity. The core hypotheses which are tested in the four interrelated studies of this work is that the (bio-)activity of the particles is defined not only by their intrinsic properties such as the composition/structure, functional groups, surface charge, and size/morphology, but also on the concentration of particles which in turn is determined by specific applications. In addition, the (bio)activity of the particles can be controlled by the application-specific biomolecules or surfactants. These hypotheses are tested on polymeric and metal oxide particles from the perspective of their application in tissue engineering of articular cartilage and consumer products (antioxidant additives and dyes), respectively. The modeling of the transport properties of biomaterials, as well as of the adsorption properties of metal oxide nanoparticles can help to determine or interpret the observed relationships

Poly(4-vinylpyridine) as a platform for robust CO2 electroreduction

The development of efficient and robust catalysts is critical for the viability of the electrocatalytic conversion of CO2 into useful chemicals. Herein, we discover a new class of metal-polymer electrocatalysts with incorporated mechanisms of their stabilization which is based on a poly(4-vinyl pyridine). We attribute the outstanding catalytic properties of the new hybrid material to new intrinsic mechanisms of the metal stabilization offered by the N-heteroaromatic polymer. More generally, our study offers a new simple strategy to design and prepare robust CO2 reduction electrocatalyst

Biocompatibility of polysebacic anhydride microparticles with chondrocytes in engineered cartilage

One of main challenges in developing clinically relevant engineered cartilage is overcoming limited nutrient diffusion due to progressive elaboration of extracellular matrix at the periphery of the construct. Macro-channels have been used to decrease the nutrient path-length; however, the channels become occluded with matrix within weeks in culture, reducing nutrient diffusion. Alternatively, microparticles can be imbedded throughout the scaffold to provide localized nutrient delivery. In this study, we evaluated biocompatibility of polysebacic anhydride (PSA) polymers and the effectiveness of PSA-based microparticles for short-term delivery of nutrients in engineered cartilage. PSA-based microparticles were biocompatible with juvenile bovine chondrocytes for concentrations up to 2mg/mL; however, cytotoxicity was observed at 20mg/mL. Cytotoxicity at high concentrations is likely due to intracellular accumulation of PSA degradation products and resulting lipotoxicity. Cytotoxicity of PSA was partially reversed in the presence of bovine serum albumin. In conclusion, the findings from this study demonstrate concentration-dependent biocompatibility of PSA-based microparticles and potential application as a nutrient delivery vehicle that can be imbedded in scaffolds for tissue engineering

Rational Design of Interfacial Properties of Ferric (Hydr)oxide Nanoparticles by Adsorption of Fatty Acids from Aqueous Solutions

Notwithstanding the great practical importance, still open are the questions how, why, and to what extent the size, morphology, and surface charge of metal (hydr)­oxide nanoparticles (NPs) affect the adsorption form, adsorption strength, surface density, and packing order of organic (bio)­molecules containing carboxylic groups. In this article, we conclusively answer these questions for a model system of ferric (hydr)­oxide NPs and demonstrate applicability of the established relationships to manipulating their hydrophobicity and dispersibility. Employing <i>in situ</i> Fourier transform infrared (FTIR) spectroscopy and adsorption isotherm measurements, we study the interaction of 150, 38, and 9 nm hematite (α-Fe₂O₃) and ∼4 nm 2-line ferrihydrite with sodium laurate (dodecanoate) in water. We discover that, independent of morphology, an increase in size of the ferric (hydr)­oxide NPs significantly improves their adsorption capacity and affinity toward fatty acids. This effect favors the formation of bilayers, which in turn promotes dispersibility of the larger NPs in water. At the same time, the local order in self-assembled monolayer (SAM) strongly depends on the morphological compatibility of the NP facets with the geometry-driven well-packed arrangements of the hydrocarbon chains as well as on the ratio of the chemisorbed to the physically adsorbed carboxylate groups. Surprisingly, the geometrical constraints can be removed, and adsorption capacity can be increased by negatively polarizing the NPs due to promotion of the outer-sphere complexes of the fatty acid. We interpret these findings and discuss their implications for the nanotechnological applications of surface-functionalized metal (hydr)­oxide NPs

Dendritic Ag Electrocatalyst with High Mass-Specific Activity for Zero-Gap Gas-Fed CO₂ Electroreduction

Electrodeposited silver catalyst is attractive compared to commercially available silver nanoparticles because it allows for the investigation of catalyst morphology and crystallography on the performance of CO2 electrolyzer for the conversion of CO2 to CO. In this work, Ag electrodes with different Ag structures varying from polycrystalline to dendrite were fabricated by controlling different electrodeposition parameters: deposition voltage, ethylenediamine additive and ammonium sulfate concentration, and time of deposition. The electrode performance was evaluated in a zero-gap, gas-fed, polymer electrolyte membrane-based cell. The highest mass-specific activity of 362 mA·mgAg–1 and a CO selectivity of 94% at a cell potential of 3 V were achieved for dendritic Ag catalyst (0.29 mg·cm–2) that possessed the maximum (220)/(111) facet ratio, as determined by X-ray diffraction. The long-term durability test on the electrode demonstrated a robust performance after 100 h of CO2 reduction at a 3 V cell voltage

Beneficial Effects of Cerium Oxide Nanoparticles in Development of Chondrocyte-Seeded Hydrogel Constructs and Cellular Response to Interleukin Insults

The harsh inflammatory environment associated with injured and arthritic joints represents a major challenge to articular cartilage repair. In this study, we report the effect of cerium oxide nanoparticles, or nanoceria, in modulating development of engineered cartilage and in combating the deleterious effects of interleukin-1α. Nanoceria was found to be biocompatible with bovine chondrocytes up to a concentration of 1000 μg/mL (60,000 cells/μg of nanoceria), and its presence significantly improved compressive mechanical properties and biochemical composition (i.e., glycosaminoglycans) of engineered cartilage. Raman microspectroscopy revealed that individual chondrocytes with internalized nanoceria have increased concentrations of proline, procollagen, and glycogen as compared with cells without the nanoparticles in their vicinity. The inflammatory response due to physiologically relevant quantities of interluekin-1α (0.5 ng/mL) is partially inhibited by nanoceria. To the best of the authors' knowledge, these results are the first to demonstrate a high potential for nanoceria to improve articular cartilage tissue properties and for their long-term treatment against an inflammatory reaction

Beneficial Effects of Cerium Oxide Nanoparticles in Development of Chondrocyte-Seeded Hydrogel Constructs and Cellular Response to Interleukin Insults

The harsh inflammatory environment associated with injured and arthritic joints represents a major challenge to articular cartilage repair. In this study, we report the effect of cerium oxide nanoparticles, or nanoceria, in modulating development of engineered cartilage and in combating the deleterious effects of interleukin-1α. Nanoceria was found to be biocompatible with bovine chondrocytes up to a concentration of 1000 μg/mL (60,000 cells/μg of nanoceria), and its presence significantly improved compressive mechanical properties and biochemical composition (i.e., glycosaminoglycans) of engineered cartilage. Raman microspectroscopy revealed that individual chondrocytes with internalized nanoceria have increased concentrations of proline, procollagen, and glycogen as compared with cells without the nanoparticles in their vicinity. The inflammatory response due to physiologically relevant quantities of interluekin-1α (0.5 ng/mL) is partially inhibited by nanoceria. To the best of the authors' knowledge, these results are the first to demonstrate a high potential for nanoceria to improve articular cartilage tissue properties and for their long-term treatment against an inflammatory reaction

Cytotoxicity, cellular localization and photophysical properties of Re(I) tricarbonyl complexes bound to cysteine and its derivatives

The potential chemotherapeutic properties coupled to photochemical transitions make the family of fac-[Re(CO)3(N,N)X]0/+ (N,N = a bidentate diimine such as 2,2'-bipyridine (bpy); X = halide, H2O, pyridine derivatives, PR3, etc.) complexes of special interest. We have investigated reactions of the aqua complex fac-[Re(CO)3(bpy)(H2O)](CF3SO3) (1) with potential anticancer activity with the amino acid l-cysteine (H2Cys), and its derivative N-acetyl-l-cysteine (H2NAC), as well as the tripeptide glutathione (H3A), under physiological conditions (pH 7.4, 37 °C), to model the interaction of 1 with thiol-containing proteins and enzymes, and the impact of such coordination on its photophysical properties and cytotoxicity. We report the syntheses and characterization of fac-[Re(CO)3(bpy)(HCys)]·0.5H2O (2), Na(fac-[Re(CO)3(bpy)(NAC)]) (3), and Na(fac-[Re(CO)3(bpy)(HA)])·H2O (4) using extended X-ray absorption spectroscopy, IR and NMR spectroscopy, electrospray ionization spectrometry, as well as the crystal structure of {fac-[Re(CO)3(bpy)(HCys)]}4·9H2O (2 + 1.75 H2O). The emission spectrum of 1 displays a variance in Stokes shift upon coordination of l-cysteine and N-acetyl-l-cysteine. Laser excitation at λ = 355 nm of methanol solutions of 1–3 was followed by measuring their ability to produce singlet oxygen (1O2) using direct detection methods. The cytotoxicity of 1 and its cysteine-bound complex 2 was assessed using the MDA-MB-231 breast cancer cell line, showing that the replacement of the aqua ligand on 1 with l-cysteine significantly reduced the cytotoxicity of the Re(I) tricarbonyl complex. Probing the cellular localization of 1 and 2 using X-ray fluorescence microscopy revealed an accumulation of 1 in the nuclear and/or perinuclear region, whereas the accumulation of 2 was considerably reduced, potentially explaining its reduced cytotoxicity.Natural Science and Engineering Research Council of CanadaCanadian Cancer SocietyCanadian Foundation for InnovationDepartment of Innovation and Science of Province of Albert