Near-infrared fluorescent dyes, such as IR780, are promising theranostics, acting as photosensitizers for photodynamic therapy and in vivo tracers in image-guided diagnosis. This work compared the uptake by macrophage-like cells of IR780 either physically associated or covalently attached to poly(D,L-lactide) (PLA) formulated as polymeric nanocapsules (NC) from a blend of PLA homopolymer and PLA-PEG block copolymer. The physicochemical characterization of both NC was conducted using asymmetric flow field-flow fractionation (AF4) analysis with static and dynamic light scattering and atomic force microscopy. The interaction of IR780 with serum proteins was evidenced by AF4 with fluorescence detection and flow cytometry in cell uptake studies. The average diameters of NC were around 120 nm and zeta potentials close to -40 mV for all NC. NC uptake by cells in different media and experimental conditions shows significantly lower fluorescence intensities for IR780 covalently linked to PLA and correspondingly low quantitative uptake. Different mechanisms of internalization were evidenced depending on the IR780 type of association to NC. Serum proteins mediate IR780 interaction with cells in a dose-dependent manner. Our results show that non-covalently linked IR780 was released from NC and accumulated in macrophage cells. Oppositely, IR780 conjugated to PLA provides stable association with NC, and its fluorescence is representative of cell uptake of the nanocarrier itself. This work strongly reinforces the importance of covalent attachment of a fluorescence dye such as IR780 to the nanocarrier to study their interaction with cells in vitro and to obtain reliable tracking in image-guided therapy.
Mechanical resistant bioactive materials are of high interest for biomedical applications. In this work, we address the improvement in mechanical properties of HA coatings by the addition of a cheap and widely available secondary phase material, the talc from soapstone. The composites hydroxyapatite/talc (HA/talc) were successfully obtained by pulsed electrodeposition and characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, Raman spectroscopy, corrosion and wear resistance and biocompatibility tests. We found that the addition of talc greatly improves the mechanical properties of coatings (i. e., wear track and friction coefficient in wear tests were significantly diminished) without diminishing corrosion resistance and biocompatibility. Alamar Blue® tests, alkaline phosphatase activity, and collagen production indicate that the biocomposites are biocompatible and talc itself induce bone maturation.
Difluoroboron β-diketonates complexes are highly luminescent with extensive properties such as their fluorescence both in solution and in solid state and their high molar extinction coefficients. Due to their rich optical properties, these compounds have been studied for their applications in organic electronics such as in self-assembly and applications in biosensors, bio-imaging and optoelectronic devices. The easy and fast synthesis of difluoroboron β-diketonate (BF2dbm) complexes makes their applications even more attractive. Although many different types of difluoroboron β-diketonates complexes have been studied, the cyclic flavanone analogues of these compounds have never been reported in the literature. Therefore, the present work aims to synthesize difluouroboron flavanone β-diketonate complexes, study their photophysical and electrochemical properties and assess their suitability for applications in optoelectronic devices. The synthesis was based on a Baker–Venkataraman reaction which initially provided substituted diketones, which were subsequently reacted with aldehydes to afford the proposed flavanones. The complexation was achieved by reacting flavanones and BF3. Et2O and in total 9 novel compounds were obtained. A representative difluoroboron flavanone complex was subjected to single crystal X-ray diffraction to unequivocally confirm the chemical structure. A stability study indicated only partial degradation of these compounds over a few days in a protic solvent at elevated temperatures. Photophysical studies revealed that the substituent groups and the solvent media significantly influence the electrochemical and photophysical properties of the final compounds, especially the molar absorption coefficient, fluorescence quantum yields, and the band gap. Moreover, the compounds exhibited a single excited-state lifetime in all studied solvent. Computational studies were employed to evaluate ground and excited states properties and carry out DFT and TDDFT level analysis. These studies clarify the role of each state in the experimental absorption spectra as well as the effect of the solvent.
Hydroxyapatite nanoparticles have been investigated as biological agents for the treatment and diagnosis of bone diseases due to their properties, providing high affinity to bone tissues and also due to the possibility to chemically modify the surfaces of these nanoparticles to provide active targeting to bone tumors or other bone disorders. In this work, synthetic hydroxyapatite nanoparticles and their surface modifications with folic and medronic acid were studied. Copper-64 was produced by neutron irradiation in a TRIGA MARK I nuclear reactor, and the functionalized nanoparticles radiolabeled with this radioisotope. The multi-technique characterization includes FTIR, PXRD, TGA, DSC, CHN, Zeta potential, XPS, SEM, TEM, and Gamma spectroscopy. Furthermore, the evaluation of the chemical interaction stability was through leaching tested for efficiency. The results indicate that folic and medronic acids can be covalently bonded to HA surface, producing a new material not yet described in the literature, been stably attached to hydroxyapatite nanoparticle surfaces, able to provide active targeting for bone disorders. The complexation of copper-64 provides high radiochemistry purity, although the specific activity must be improved.
Molecular Dynamics simulations of water confined in carbon nanotubes subjected to external electric fields show that water mobility strongly depends on the confining geometry, the intensity and directionality of the electric field. While fields forming angles of 0° and 45° slow down the water dynamics by increasing organization, perpendicular fields can enhance water diffusion by decreasing hydrogen bond formation. For 1.2 diameter long nanotubes, the parallel field destroys the ice-like water structure increasing mobility. These results indicate that the structure and dynamics of confined water are extremely sensitive to external fields and can be used to facilitate filtration processes.
Low-dimensionality materials are highly susceptible to interfaces. Indeed, intercalation of different chemical species in between epitaxial graphene and silicon carbide (SiC), for instance, may decouple the graphene with respect to the substrate due to the conversion of the buffer layer into a graphene layer. O-intercalation is known to release the strain of such 2D material and to lead to the formation of high structural quality AB-stacked bilayer graphene. Nonetheless, this interface transformation concomitantly degrades graphene electronic transport properties. In this work we employed different techniques in order to better understand the structure of the graphene/SiC interface generated by O-intercalation and to elucidate the origin of the poor electronic properties of graphene. Experimental results revealed the formation of a SiO2 rich layer with a defective transition layer in between it and the SiC, which is characterized by the existence of silicon oxycarbide structures. Scanning tunneling spectroscopy measurements revealed an extensive presence of electronic states just around the Fermi level all over the sample surface, which may suppress the charge carriers mobility around this region. According to theoretical calculations, such states are mainly due to the formation of silicon oxicarbides within the interfacial layer.
The control of geometric structure is a key aspect in the interplay between theoretical predictions and experimental realization in the science and applications of nanomaterials. This is particularly important in one-dimensional structures such as nanoribbons, in which the edge morphology dictates most of the electronic behavior in low energy scale. In the present work we demonstrate by means of first principles calculations that the oxidation of few-layer antimonene may lead to an atomic restructuring with formation of ordered multilayer zig-zag nanoribbons. The widths are uniquely determined by the number of layers of the initial structure, allowing the synthesis of ultranarrow ribbons and chains. We also show that the process may be extended to other compounds based on group V elements, such as arsenene. The characterization of the electronic structure of the resulting ribbons shows an important effect of stacking on band gaps and on modulation of electronic behavior.
Gypsum is an Earth-abundant mineral with enormous applications in agriculture and civil engineering. Here, we show it is also an excellent height calibration standard alternative for atomic force microscopy (AFM). Using plain water as etchant, gypsum flakes readily review 0.75 nm tall terraces which are easy to image (lateral dimensions from tens to hundreds of nanometers) and robust against time in ambient conditions. Therefore, the present work demonstrates a new height standard alternative which is easily-available for all AFM microscopists around the world.
Scanning probe microscopy and ab initio calculations reveal modifications on the electronic and structural properties of graphene/h-BN heterostructures induced by compression. Using AFM and EFM techniques, with charge injection being made in the heterostructures at different pressures, the charge injection efficiency monotonically decreases with increasing pressure for monolayer-graphene (MLG)+BN heterostructures, indicative of a conductor-insulator electronic transition. Bilayer-graphene (BLG)+BN and trilayer-graphene (TLG)+BN heterostructures show a non-monotonic behavior of charge injection versus pressure, indicative of competing electronic structure modifications. First-principle calculations of these systems indicate a pressure-induced van der Waals-to-covalent interlayer transition, where such interlayer covalent binding, in the presence of water molecules, results in a disordered insulating structure for the MLG + BN case, while it leads to an ordered conducting structure for both BLG + BN and TLG + BN heterostructures. These opposing effects may have a strong influence on graphene/h-BN-based electronic devices and their physics under pressurized environments.
We use molecular dynamics simulations to study the diffusion of water inside deformed carbon nanotubes with different degrees of eccentricity at 300 K. We found a water structural transition between tubular-like to single-file for (7,7) nanotubes associated with change from a high to low mobility regimes. Water is frozen when confined in a perfect (9,9) nanotube and it becomes liquid if such a nanotube is deformed above a certain threshold. Water diffusion enhancement (suppression) is related to a reduction (increase) in the number of hydrogen bonds. This suggests that the shape of the nanotube is an important ingredient when considering the dynamical and structural properties of confined water.
The addition of propolis extract (PE) to the glass ionomer results in an adhesive material for restorative treatment, with interesting properties mainly due to the flavonoids contained in the propolis extract. However, no study of the flavonoid release profile in these materials was reported. This work studies the flavonoid release profile in such materials aiming to contribute to the future synthesis of optimized devices adept to prolong the efficacy of the drug. The study involved the synthesis and study of the physicochemical, antibacterial and mechanical properties of glass ionomer cement (GIC) and glass-ionomer-propolis composites (GIC-PE). The samples were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and thermogravimetric analyses. The released concentration of flavonoids, the antimicrobial activity and the compressive strength were also evaluated. Antimicrobial activity was assessed against Streptococcus mutans, Streptococcus salivarius, and Candida albicans, common pathogens in the mouth. The results indicate that the antibacterial activity of GIC-PE samples is closely correlated with the release of flavonoids. The method used to prepare the composite GIC-PE leads to an initial drug delivery burst effect able to diminish partially the population of bacteria tested. The mechanical properties and thermal stability of GIC-PE are higher than those of the GIC and are clearly related to its microstructure. This study is clinically significant because the addition of propolis extract (PE) to the GIC resulted in a novel differentiated product with enhanced mechanical and antimicrobial properties compared to the GIC.
We employed PBE and BLYP semi-local functionals and the van der Waals density functional of Dion et al. (2004) (vdW-DF) to investigate structural properties of liquid acetonitrile and methanol. Among those functionals the vdW-DF is the only one that correctly predicts energy minima in inter-molecular interactions between acetonitrile molecules. We found that van der Waals interactions have a negligible effect on H-bonds in methanol chains. However, it significantly increases chain packing resulting in a more dense liquid in comparison to the other two functionals. The overall trend is that the vdW-DF tends to overestimate density and bulk modulus, meanwhile the semi-local functionals tend to underestimate density. Thus, van der Waals interactions play an important role in the properties of liquids in which much stronger dipole-dipole interactions are present.
Calcium phosphates are suggested as a CO2 adsorbent via pressure swing adsorption. Amorphous calcium phosphate (ACP) and biphasic calcium phosphate (BCP) (composed of hydroxyapatite and beta-tricalcium phosphate) were investigated for the capture/immobilization of the gas. A fluidized bed was set up to assess the levels of CO2 adsorption by ACP and BCP. A gaseous mixture was synthesized, mimicking the conditions for possible industrial use. The results show a significant reduction in CO2 concentrations. Using DFT calculations, we show that CO2 adsorption increases the stability by reducing the surface energy. The energies involved and preferential adsorption sites were also theoretically predicted.
Phenazine derivative molecules were studied using steady state and time resolved fluorescence techniques and demonstrated to lead to strong formation of aggregated species, identified as dimers by time dependent density functional theory calculations. Blended films in a matrix of Zeonex®, produced at different concentrations, showed different contributions of dimer and monomer emissions in a prompt time frame, e.g. less than 50 ns. In contrast, the phosphorescence (e.g. emission from the triplet state) shows no significant effect on dimer formation, although strong dependence of the phosphorescence intensity on concentration is observed, leading to phosphorescence being quenched at higher concentration.
Optical microscopy has been one of the most important tools for visualizing biological samples since the seventeenth century. Recently, with the advances in femtosecond laser technology, all the nonlinear optical processes have now been included as optical microscopy methods, and second harmonic generation (SHG) microscopy has emerged as a powerful new optical imaging tool with applications in medicine and biology. Here we use SHG microscopy to obtain images of 76 prostate biopsies on histological slides. Multiple samples from the excised prostates of patients who underwent a radical prostatectomy were evaluated. The samples were collected from prostate positions as in needle biopsy procedures. The results show the collagen fiber architecture among malignant acini, and analysis of the fiber orientation in the images reveals that the collagen fibers become more aligned at higher malignancy grades. Furthermore, we find that the degree of fiber alignment correlates directly with the Gleason patterns.
The combined use of the microcapillary cell (MEC) and scanning vibrating electrode technique (SVET) and low-angle cross sections was employed to elucidate the role of each coating region on the protection of the cut-edge corrosion of galvanized steels. Different compounds are involved in the blocking action of the corrosion products: Zincite (ZnO) on the steel substrate, hydrozincite (Zn5(OH)6(CO3)2) at the coating/steel interface, and Simonkolleite (Zn5(OH)8Cl2) and ZnO on the different coating regions in different proportions. The coating surface is also active at the initial stage and during long-term protection and thus, must be considered in experimental simulation of the cut-edge corrosion.
The use of chitosan functionalized silica for benznidazole delivery in the treatment of neglected disease such as Chagas disease is one of the forms not yet explored, but with great potential for this therapy, as little is known about nanoformulations for the treatment of Chagas disease. In this work, we used chitosan-succinate covalently attached to the surface pore of MSNs to act as anchor for benznidazole as a delivery system. The samples were characterized structurally and chemically with multiple techniques. The applicability of functionalized MSNs as platforms for benznidazole delivery into T. cruzi parasites was assessed. The results demonstrate that the proposed system is a potential promising nanoplatform for drug and gene delivery targeting neglected diseases such as Chagas disease.
Synthetic polymers are made up of repeated monomeric units, and this gives them a very versatile appearance, making them useful in many areas of science. One is the pharmaceutical, which correlates the properties of the polymer with the active principle, so they can be used as an excipient or in the controlled release system. The PMMA-g-PEG4000 has characteristics derived from its precursors, that are pharmacologically active. When we incorporate drugs into this structure, the polymer can act on the controlled release, lessening the toxic character of the drug and producing fewer side effects. In this work, incorporations of the drug indomethacin were made in the PMMA-g-PEG copolymer and derivatives (PMMA-g-PEG4000 ETIL and PMMA-g-PEG4000 ACET). The samples were characterized by infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), thermogravimetric analysis (TGA), and atomic force microscopy (AFM) measurements. For each sample, the controlled release was performed in a total time of 4 h and the efficiency of the modified structures was verified.