Purification of Intramineral Peptides from Cuttlebones and In Vitro Activity in CaCO3 Biomineralization.

Living organisms develop functional hard structures such as teeth, bones, and shells from calcium salts through mineralization for managing vital functions to sustain life. However, the exact mechanism or role of biomolecules such as proteins and peptides in the biomineralization process to form defect-free hierarchical structures in nature is poorly understood. In this study, we have extracted, purified, and characterized five major peptides (CBP1-CBP5) from the soluble organic materials (SOMs) of cuttlefish bone (CB) and used for the in vitro mineralization of calcium carbonate crystals. The SOMs induced nucleation of the calcite phase at low concentrations and the vaterite phase at high concentrations. The purified peptides nucleated calcite crystals and enhanced aggregation under laboratory conditions. Among five peptides, only CBP2 and CBP3 showed concentration-dependent nucleation, aggregation, and morphological changes of the calcite crystals within 12 h. Circular dichroism studies showed that the peptides CBP2 and CBP3 are in alpha helix and ß-sheet conformation, respectively, in solution. CBP1 and CBP4 and CBP5 are in random coil and ß-sheet conformation, respectively. In addition, the peptides showed different sizes in solution in the absence (∼27 nm, low aggregation) and presence (∼118 nm, high aggregation) of calcium ions. Aragonite crystals with needle-type morphologies were nucleated in the presence of Mg2+ ions in solution. Overall, exploring the activities of such intramineral peptides from CB help to unravel the mechanism of calcium salt deposition in nature.

Patterning at the Resolution Limit of Commercial Electron Beam Lithography.

It has been long known that low molecular weight resists can achieve a very high resolution, theoretically close to the probe diameter of the electron beam lithography (EBL) system. Despite technological improvements in EBL systems, the advances in resists have lagged behind. Here we demonstrate that a low-molecular-mass single-source precursor resist (based on cadmium(II) ethylxanthate complexed with pyridine) is capable of a achieving resolution (4 nm) that closely matches the measured probe diameter (∼3.8 nm). Energetic electrons enable the top-down radiolysis of the resist, while they provide the energy to construct the functional material from the bottom-up─unit cell by unit cell. Since this occurs only within the volume of resist exposed to primary electrons, the minimum size of the patterned features is close to the beam diameter. We speculate that angstrom-scale patterning of functional materials is possible with single-source precursor resists using an aberration-corrected electron beam writer with a spot size of ∼1 Å.

Inhibiting Erastin-Induced Ferroptotic Cell Death by Purine-Based Chelators.

Ferroptosis is a cell death event caused by increased lipid peroxidation leading to iron-dependent oxidative stress and is associated with a wide variety of diseases. In recent years, ferroptosis inhibition has emerged as a novel strategy to target different pathologies. Here, we report the synthesis of two purine derivatives, 1 and 2, for iron chelation strategy and evaluate their potency to inhibit erastin-induced ferroptosis. Both compounds showed efficient iron chelation in solution as well as in cellular environment. The crystal structure of the purine derivatives with iron demonstrated a 2 : 1 (ligand to metal center) stoichiometry for iron and purine derivative complexation. The synthesized compounds also decrease the reactive oxygen species concentration in cell cultures. Compound 2 showed better potency towards the prevention of ferroptotic cell death as compared to commercially available iron chelator in the erastin-induced ferroptosis cell culture model. Such purine analogues are potential functional scaffolds for the development of target molecules for ferroptosis inhibition.

Comparison of Genotoxicity and Cytotoxicity of Polyvinyl Chloride and Poly(methyl methacrylate) Nanoparticles on Normal Human Lung Cell Lines.

High concentrations of micro- and nanoparticles of common plastic materials present in the environment are causing an adverse health impact on living organisms. As a model study, here we report the synthesis and characterization of luminescent polyvinyl chloride (PVC) and poly(methyl methacrylate) (PMMA) nanoparticles and investigate the interaction with normal human lung fibroblast cells (IMR 90) to understand the uptake, translocation, and toxicity of PVC and PMMA nanoparticles. The synthesized particles are in the size range of 120-140 nm with a negative surface potential. The colocalization and uptake efficiency of the nanoparticles were analyzed, and the cytotoxicity assay shows significant reduction in cell viability. Cellular internalization was investigated using colocalization and dynasore inhibitor tests, which showed that the PVC and PMMA nanoparticles enter into the cell via endocytosis. The polymer nanoparticles induced a reduction in viability, decrease in adenosine triphosphate, and increase in reactive oxygen species and lactate dehydrogenase concentrations. In addition, the polymer nanoparticles caused cell cycle arrest at sub-G1, G0/G1, and G2/M phases, followed by apoptotic cell death. Our results reported here are important to the emerging data on understanding the impact of common polymer particles on human health.

Fine-Tuning the Electronic Properties of Azo Chromophore-Incorporated Perylene Bisimide Dyads.

Perylene bisimide (PBI) and azo-compounds are fascinating molecules with interesting optical properties. Here, we combine the two chromophores to prepare nonconjugated and conjugated stable azo-PBI dyes. The detailed structural characterization, comparison of properties, and solid-state self-assembly of the compounds are discussed. The incorporation of azo groups at the bay side of PBI led to significant changes in optical properties as compared to the model PBIs (M1 and M2). All new azo-PBIs showed photoinduced isomerization, which caused disaggregation and enhancement in fluorescence. The amine-incorporated azo-PBIs (3 and 6) reduced chloroauric acid into gold nanoparticles. The current study offers a simple synthetic strategy and comparison of the properties of conjugated and nonconjugated azo-PBIs, which could be useful in photoelectronic devices.

Tubular Perylene Bisimide Macrocycles for the Recognition of Geometrical Isomers of Azobenzenes.

Perylene bisimide-based materials are good candidates for photosensitive applications. Herein, we report synthesis, characterization, and complexation studies of perylene bisimide macrocycles obtained through bayside coupling. The isomeric macrocycles incorporated with interesting optical properties and tubular-shaped cavities are able to recognize geometric isomers of azobenzenes and aromatic amines. Such selective recognition is useful toward developing potential sensors for interesting isomeric pairs in the future.

Soluble Graphene Nanoribbons from Planarization of Oligophenylenes.

A solution-based chemical synthesis of two graphene nanoribbons with armchair edges is reported. The precursor oligophenylene molecules are synthesized and subjected to oxidative cyclodehydrogenation to afford the target molecules, G-1 and G-2. These molecules have good solubility in organic solvents, and show a large redshift in their absorption edge (up to 185 nm) and emission maximum (up to 125 nm) after planarization. Fibrous structures are formed upon self-assembly of molecules through columnar π-π stacking. Such molecular assemblies may be useful for various applications.

Low-Band-Gap BODIPY Conjugated Copolymers for Sensing Volatile Organic Compounds.

Conjugated polymers with strong photophysical properties are used in many applications. A homopolymer (P1) and five new low band gap copolymers based on 4,4'-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) and acceptors 3,6-dithienyldiketopyrrolopyrrole (P2), phthalimide (P3), benzotriazole (P4), 4,7-dithienyl[1,2,3]triazolo[4,5g]quinoxaline (P5), and 2,5-dithienylthieno[3,4-b]pyrazine (P6) were prepared by means of Sonogashira polymerization. The characterization of polymers by using (1) H NMR, absorption, and emission spectroscopy is discussed. All polymers with high molecular weights (Mn ) of 16 000 to 89 000 g mol(-1) showed absorption maxima in the deep-red region (λ=630-760 nm) in solution and exhibited significant redshifts (up to 70 nm) in thin films. Polymers P2, P5, and P6 showed narrow optical band gaps of 1.38, 1.35, and 1.38 eV, respectively, which are significantly lower than that of P1 (1.63 eV). The HOMO and LUMO energy levels of the polymers were calculated by using cyclic voltammetry measurements. The LUMO energy levels of BODIPY-based alternating copolymers were independent of the acceptors; this suggests that the major factor that tunes the LUMO energy levels of the polymers could be the BODIPY core. All polymers showed selective and reproducible detection of volatile organic solvents, such as toluene and benzene, which could be used for developing sensors.

Shape Sensitivity on Toxicity of Gold Nanoplates in Breast Cancer Cells.

Gold nanomaterials (Au NMs) have been explored for a wide range of applications in catalysis and medicine. Here we report the shape sensitive toxicity of gold nanoplates (Au nanoplates) in breast cancer cell line, MCF7. Au nanoplates induced a dose- and shape-dependent toxicity to cancer cells. Oxidative stress induced by Au nanoplates is believed to be the trigger for the DNA, which resulted in cell apoptosis. In summary, the results from our study demonstrate that morphology appears to play a significant role in mediating the cellular responses and Au triangles nanoplates showed the highest toxicity to the cells. Such findings may be able to shine more light on the shape-dependent interaction between Au NMs and living organisms.

Synthesis and photophysical properties of pyrene-based green fluorescent dyes: butterfly-shaped architectures.

A few pyrene-based fluorescent compounds were synthesized using Pd/Cu-catalyzed cross-coupling reaction. Photophysical properties of the π-conjugated pyrene derivatives were studied and the results indicate materials with high quantum efficiency and high extinction coefficient. No π stacking was observed in the crystal lattice. The molecules described here may be useful in developing sensors or imaging agents.

Differential effect of solar light in increasing the toxicity of silver and titanium dioxide nanoparticles to a fish cell line and zebrafish embryos.

The increasing use of silver (Ag) and titanium dioxide (TiO2) nanoparticles (NPs) in consumer products and their inevitable seepage into the environment prompted us to investigate their potential toxicity to a fish cell line (BF-2) and zebrafish embryos under dark and Simulated Solar Light (SSL) exposure conditions. Using high throughput screening (HTS) platforms, we showed that the oxidative stress-dependent cytotoxicity and embryonic toxicity of NPs were significantly increased upon exposure to SSL. While, the toxicity of TiO2 NPs under SSL exposure could be explained by hydroxyl radical generation, the enhanced toxicity of Ag NPs under SSL exposure was due to surface oxidation and physicochemical modification of Ag NPs and shedding of Ag+, leading to an increased bioavailability of silver. Our observations that solar light could induce physicochemical transformation of TiO2 and Ag NPs and enhance their toxic potential emphasizes the need for conducting future toxicity studies under environmentally relevant exposure conditions to guide decision making on the safe handling of NPs.

Anomalous metallic-like transport of Co-Pd ferromagnetic nanoparticles cross-linked with π-conjugated molecules having a rotational degree of freedom.

We investigated the electron transport in Co-Pd ferromagnetic nanoparticles (Co 16%) cross-linked with oligo(phenyleneethynylene)diethanethiolate, which consists of three rotary phenylene moieties bridged by two acetylene groups, or icosane-1,20-dithiol, which consists of one alkane chain. Although the nanoparticles cross-linked with the alkane dithiols (the latter) have extremely high electrical resistance in electron transport, the resistance of the nanoparticles cross-linked with the conjugated molecules (the former) demonstrates a linear temperature dependence from room temperature to ca. 20 K; below that temperature, it has a weak temperature-dependent residual contribution with a resistance minimum around 7 K. Computational simulations suggest that the apparent metallic-like temperature dependence at high temperatures can be explained in terms of the rotational degree of freedom of the linker molecule. The rotational motion of the constituent phenylene groups, which hinders π-conjugation along the linker molecule, becomes less excited as the temperature is lowered. The successive development of a ballistic transport path through the π-conjugated linker molecule with decreasing temperature yields the metallic-like temperature dependence observed for the bridged nanoparticles. The low-temperature resistance behaviour with a minimum is a consequence of carrier scattering by the localized Co spins of Co-Pd nanoparticles randomly ordered in a ferromagnetic state that develops below the temperature of the resistance minimum.

Conversion of PET Bottle Waste into a Terephthalic Acid-Based Metal-Organic Framework for Removing Plastic Nanoparticles from Water.

Micro- and nanoparticles of plastic waste are considered emerging pollutants with significant environmental and health impacts at high concentrations or prolonged exposure time. Here we report the synthesis and characterization of a known metal-organic framework (MOF) using terephthalic acid (TPA) recovered from the hydrolysis of polyethylene terephthalate (PET) bottle waste. This approach adds value to the existing large amounts of bottle waste in the environment. Fully characterized zinc-TPA MOF (MOF-5) was used for the extraction and removal of engineered polyvinyl chloride (PVC) and polymethylmethacrylate (PMMA) nanoparticles from water with a high efficiency of 97% and 95%, respectively. Kinetic and isotherm models for the adsorption of polymer nanoparticles (PNPs) on the MOF surface were investigated to understand the mechanism. The Qmax for PVC and PMMA NPs were recorded as 56.65 mg/g and 33.32 mg/g, respectively. MOF-5 was characterized before and after adsorption of PNPs on the surface of MOF-5 using a range of techniques. After adsorption, the MOF-5 was successfully regenerated and reused for the adsorption and removal of PNPs, showing consistent results for five adsorption cycles with a removal rate of 83-85%. MOF-5 was characterized before and after adsorption of PNPs on the surface using a range of techniques. The MOF-5 with PNPs on the surface was successfully regenerated and reused for the adsorption and removal of polymer nanoparticles, showing consistent results for five extraction cycles. As a proof of concept, MOF-5 was also used to remove plastic particles from commercially available body scrub gel solutions. Such methods and materials are needed to mitigate the health hazards caused by emerging micro- and nanoplastic pollutants in the environment.

Understanding the aggregation, consumption, distribution and accumulation of nanoparticles of polyvinyl chloride and polymethyl methacrylate in Ruditapes philippinarum.

Plastic products have become an integral part of our life. A widespread usage, high stability, uncontrolled disposal and slow degradation of plastics in the environment led to the generation and accumulation of nanoparticles of polymers (NPs) in the marine environment. However, little is known about the aggregation, consumption and distribution of NPs from common polymers such as polyvinyl chloride (NP-PVC) and polymethyl methacrylate (NP-PMMA) inside marine animal physiologies. In the current study, two types of polymers (PVC and PMMA) × four exposure concentrations (1, 5, 15 and 25 mg/L) × four times (4, 8, 12 and 24 h) exposure studies were conducted to understand the consumption and distribution of luminescent NP-PVC (98.6 ± 17.6 nm) and NP-PMMA (111.9 ± 37.1 nm) in R. philippinarum. Under laboratory conditions, NP-PVC showed a higher aggregation rate than NP-PMMA in seawater within a period of 24 h. Aggregations of NPs increased with an increase in initial NP concentrations, leading to significant settling of nanoparticles within 24 h exposure. Such aggregation and settling of particles enhanced the consumption of NPs by benthic filter-feeding R. philippinarum at all exposure concentrations during 4 h exposure. More interestingly, NP-PVC and NP-PMMA were observed in large amounts in both liver and gills (22.6 % - 29.1 %) of the clams. Furthermore, NP-PVC was detected in most organs of R. philippinarum as compared to NP-PMMA. This study demonstrates that different polymers distribute and accumulate differently in the same biological model under laboratory exposure conditions based on their chemical nature.

Synthesis of perylene dyes with multiple triphenylamine substituents.

Perylene monoimide (PMI) was brominated to give tetra- and tribrominated molecules, which underwent a Suzuki coupling reaction with 4-(diphenylamino)phenylboronic acid to give PMI derivatives. The photophysical and electrochemical properties of the synthesized compounds were investigated, and theoretical calculations were performed. Single crystals of tetrasubstituted PMI were grown and studied in detail. The structure-property relationships were examined to reveal the effect of the position and number of substituents on the perylene core unit. All molecules showed a broad absorption up to 750 nm. Corresponding anhydrides of PMIs were used for fabrication of dye-sensitized solar cells. The molecule with four triphenylamine units on perylene monoanhydride showed the highest power conversion efficiency.

Simple and efficient biomimetic synthesis of Mn3O4 hierarchical structures and their application in water treatment.

Biotemplate synthesis of functional materials is interesting owing to low cost, high yield and easy way of preparation. Recently, we have developed a simple and cost effective biomimetic synthesis of hierarchical network like nanostructures of manganese oxide (Mn3O4). Readily available eggshell membrane with nucleating and capping sites were used as a template in our synthesis. The prepared material was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray Diffraction (XRD). The surface area was calculated using the Brunauer-Emmett-Teller (BET) theory, and pore size distribution was obtained by Barrett-Joyner-Helenda (BJH) method. The prepared Mn3O4 showed good ability to remove organic pollutants from water and expected to be useful in effluent treatment in textile industry.

Fabrication and characterization of hybrid nanofibers from poly(vinyl alcohol), milk protein and metal carbonates.

Porous three dimensional nanofibrous membranes were fabricated from poly(vinyl alcohol) (PVA), milk protein and inorganic salts such as calcium carbonate (CaCO3) or magnesium carbonate (MgCO3). Microscopic investigations showed that the fibers have smooth morphology with an average diameter of 300-500 nm and a surface area of 5.29 m2g(-1). Thermal analysis of the composite nanofibers showed a decrease in glass transition temperature as compared to PVA nanofiber. Incorporation of CaCO3 and MgCO3 into the nanofiber matrix was confirmed by energy dispersive spectroscopy and X-ray diffraction analysis. The cytocompatibility of electrospun composite nanofiber sheets was evaluated using human lung fibroblasts (IMR-90). There was an increase in cell attachment and cell density on milk protein incorporated to PVA-CaCO3 and PVA-MgCO3 fibers within a week of cell seeding. The cytocompatibility and increase in cell adhesion property of the hybrid nanofiber may provide significant advantages for such materials in biomedical applications.

A comparative investigation of toxicity of three polymer nanoparticles on acorn barnacle (Amphibalanus amphitrite).

Pollution from plastic waste is increasingly prevalent in the environment and beginning to generate significant adverse impact on the health of living organisms. In this study, we investigate the toxicity of polymer nanoparticles exposed to Acorn Barnacle (Amphibalanus amphitrite) nauplii, as an animal model. Highly stable aqueous dispersion of luminescent nanoparticles from three common polymers: polymethylmethacrylate (PMMA), polystyrene (PS), and polyvinylchloride (PVC), were prepared via nanoprecipitation and fully characterised. Exposure studies of these polymer particles to freshly spawned barnacle nauplii were performed within a concentration range from 1 to 25 mg/L under laboratory-controlled conditions. The exposure to PMMA and PS nanoparticles did not show detrimental toxicity and did not cause sufficient mortality to compute a LC50 value. However, PVC nanoparticles were significantly toxic with a mortality rate of up to 99% at 25 mg/L, and the calculated LC50 value for PVC nanoparticles was 7.66 ± 0.03 mg/L, 95% CI. Interestingly, PVC nanoparticle aggregates were observed to adhere to the naupliar carapace and appendages at higher concentrations and could not be easily removed by washings. To explore the possibility of chemical toxicity of polymer nanoparticles, analysis of the polymer powders which was used to prepare the nanoparticles was conducted. The presence of low molecular weight oligomers such as dimers, trimers and tetramers were observed in all polymer samples. The chemical nature and concentration of such compounds are likely responsible for the observed toxicity to the barnacle nauplii. Overall, our study shows that care should be exercised in generalising the findings of exposure studies performed using one type of plastic particles, as the use of different plastic particles may elicit different responses inside a living organism.

Understanding the biological impact of organic pollutants absorbed by nanoplastics.

Many organisms are consuming food contaminated with micro- and nanoparticles of plastics, some of which absorb persistent organic pollutants (POPs) from the environment and acting as carrier vectors for increasing the bioavailability in living organisms. We recently reported that polymethylmethacrylate (PMMA) nanoparticles at low concentrations are not toxic to animal models tested. In this study, the toxicity of diphenylamine (DPA) incorporated PMMA nanoparticles are assessed using barnacle larvae as a model organism. The absorption capacity of DPA from water for commercially available virgin PMMA microparticles is relatively low (0.14 wt%) during a 48 h period, which did not induce exposure toxicity to barnacle nauplii. Thus, PMMA nanoparticles encapsulated with high concentrations of DPA (DPA-enc-PMMA) were prepared through a reported precipitation method to achieve 40% loading of DPA inside the particles. Toxicity of DPA-enc-PMMA nanoparticles were tested using freshly spawned acorn barnacle nauplii. The observed mortality of nauplii from DPA-enc-PMMA exposure was compared to the values obtained from pure DPA exposure in water. The mortality among the exposed acorn barnacle nauplii did not exceed 50% even at a high concentration of DPA inside the PMMA nanoparticles. The results suggest that the slow release of pollutants from polymer nanoparticles may not induce significant toxicity to the organism living in a dynamic environment. The impact of long-term exposure of DPA absorbed plastic nanoparticles need to be investigated in the future.

Magnetic sponge prepared with an alkanedithiol-bridged network of nanomagnets.

The magnetic dipole-dipole interaction between nanomagnets having huge magnetic moments can have a strength comparable to that of the van der Waals interaction between them, and it can be manipulated by applying an external magnetic field of conventional strength. Therefore, the cooperation between the dipole-dipole interaction and the applied magnetic field allows the magnetic moments of nanomagnets to be aligned and organized in an ordered manner. In this work, a network of magnetic nanoparticles connected with flexible long-alkyl-chain linkers was designed to develop a "magnetic sponge" capable of absorbing and desorbing guest molecules with changes in the applied magnetic field. The magnetization of the sponge with long-alkyl-chain bridges (30 C atoms) exhibited a 500% increase after cooling in the presence of an applied field of 7 T relative to that in the absence of a magnetic field. Cooling in a magnetic field leads to anisotropic stretching in the sponge due to reorganization of the nanomagnets along the applied field, in contrast to the isotropic organization under zero-field conditions. Such magnetic-responsive organization and reorganization of the magnetic particle network significantly influences the gas absorption capacity of the nanopores inside the material. The absorption and desorption of guests in an applied magnetic field at low temperature can be regarded as a fascinating "breathing feature" of our magnetic sponge.