Microbial nanocellulose adherent to human skin used in electrochemical sensors to detect metal ions and biomarkers in sweat.

The pursuit of biocompatible, breathable and skin-conformable wearable sensors has predominantly focused on synthetic stretchable hydrophobic polymers. Microbial nanocellulose (MNC) is an exceptional skin-substitute natural polymer routinely used for wound dressing and offers unprecedented potential as substrate for wearable sensors. A versatile strategy for engineering wearable sensing platforms is reported, with sensing units made of screen-printed carbon electrodes (SPCEs) on MNC. As-prepared SPCEs were used to detect the toxic metals cadmium (Cd2+) and lead (Pb2+) with limits of detection of 1.01 and 0.43 µM, respectively, which are sufficient to detect these metal ions in human sweat and urine. SPCEs functionalized through anodic pre-treatments were used for detecting uric acid and 17ß-estradiol in artificial sweat, with detection limits of 1.8 µM and 0.58 µM, respectively. The electrochemical treatment created oxygen groups on the carbon surfaces, thus improving wettability and hydrophilicity. MNC was herein exploited as an adhesive-free, yet highly skin-adherent platform for wearable sensing devices that also benefit from the semi-permeable, non-allergenic, and renewable features that make MNC unique within the pool of materials that have been used for such a purpose. Our findings have clear implications for the developments on greener and more biocompatible but still efficient substrates and may pave the route for combining immunosensing devices with drug delivery therapies.

Ecological Biosubstrates Obtained from Onion Pulp (Allium cepa L.) for Flexible Organic Light-Emitting Diodes.

A new biopolymer obtained from onion pulp (Allium cepa L.) was employed to produce a sustainable substrate for flexible organic light-emitting diodes (FOLEDs). Indium tin oxide (ITO) and SiO2 thin films were deposited by rf-magnetron sputtering onto these biosubstrates to obtain flexible, transparent, and conductive anodes, on top of which FOLEDs were produced. This new biomaterial exhibits an optical transparency of 63% at 550 nm. ITO films were optimized by varying rf power during deposition onto the biopolymers, and their electrical properties are comparable to the those of ITO grown on top of rigid substrates: a carrier concentration of -3.63 × 1021 cm-3 and carrier mobility of 7.72 cm2 V-1 s-1 for the optimized film. Consequently, the sheet resistance and resistivity of this ITO film were 8.92 Ω sq-1 and 2.23 × 10-4 Ω cm, respectively, hence allowing the production of FOLEDs. The A. cepa L. based FOLED was fabricated using CuPc, ß-NPB, and Alq3 as organic layers, and it exhibited a maximum luminance of about 2062 cd m-2 at 16.6 V. The current efficiency reached a maximum value of 2.1 cd A-1 at 85.3 mA cm-2. The obtained results suggest the possibility to use these substrates for innovative biocompatible applications in optoelectronics, such as photodynamic therapy.

New insights towards mesoporous silica nanoparticles as a technological platform for chemotherapeutic drugs delivery.

Mesoporous silica nanoparticles (MSNs) displays interesting properties for biomedical applications such as high chemical stability, large surface area and tunable pores diameters and volumes, allowing the incorporation of large amounts of drugs, protecting them from deactivation and degradation processes acting as an excellent nanoplatform for drug delivery. However, the functional MSNs do not present the ability to transport the therapeutics without any leakage until reach the targeted cells causing side effects. On the other hand, the hydroxyls groups available on MSNs surface allows the conjugation of specific molecules which can binds to the overexpressed Enhanced Growth Factor Receptor (EGFR) in many tumors, representing a potential strategy for the cancer treatment. Beyond that, the targeting molecules conjugate onto mesoporous surface increase its cell internalization and act as gatekeepers blocking the mesopores controlling the drug release. In this context, multifunctional MSNs emerge as stimuli-responsive controlled drug delivery systems (CDDS) to overcome drawbacks as low internalization, premature release before to reach the region of interest, several side effects and low effectiveness of the current treatments. This review presents an overview of MSNs fabrication methods and its properties that affects drug delivery as well as stimuli-responsive CDDS for cancer treatment.

Luminescent Mesoporous Silica Nanohybrid Based on Drug Derivative Terbium Complex.

Mesoporous silica nanoparticles prepared by organic template-driven synthesis have been successfully explored as carriers of the drug-derivate green luminescent complex of terbium (III) with the nonsteroidal anti-inflammatory drug ketoprofen. The terbium (III) complex was synthesized by reacting ketoprofen sodium salt with terbium (III) chloride, which was further adsorbed onto the surface of mesoporous nanoparticles with a mean particle size of 47 ± 4 nm and pore size of 11 nm. The incorporation of the complex into mesoporous silica nanoparticles was tracked by the decrease in the surface area and pore size of the nanoparticles, and successfully demonstrated by substantial changes in the adsorption isotherms and thermal and vibrational spectroscopy results. The cytotoxicity assay and confocal microscopy have shown that the novel luminescent nanohybrid presents high cell viability and the characteristic terbium (III) emission can be assessed through two-photon excitation, which paves the way for bioimaging applications in nanomedicine.

Surface Plasmon Resonances in Silver Nanostars.

The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced sensing and spectroscopy, which may be further exploited if the mechanisms behind the excitation of localized surface plasmon resonances (LSPRs) are identified. Here, we show that LSPRs in Ag-NSs can be obtained with finite-difference time-domain (FDTD) calculations by considering the nanostars as combination of crossed nanorods (Ag-NRs). In particular, we demonstrate that an apparent tail at large wavelengths ( λ ≳ 700 nm) observed in the extinction spectra of Ag-NSs is due to a strong dipolar plasmon resonance, with no need to invoke heterogeneity (different number of arms) effects as is normally done in the literature. Our description also indicates a way to tune the strongest LSPR at desired wavelengths, which is useful for sensing applications.

Hydrothermal synthesis of bacterial cellulose-copper oxide nanocomposites and evaluation of their antimicrobial activity.

In this work, for the first time bacterial cellulose (BC) hydrogel membranes were used for the fabrication of antimicrobial cellulosic nanocomposites by hydrothermal deposition of Cu derivative nanoparticles (i.e.Cu(0) and CuxOy species). BC-Cu nanocomposites were characterized by FTIR, SEM, AFM, XRD and TGA, to study the effect of hydrothermal processing time on the final physicochemical properties of final products. XRD result show that depending on heating time (3-48h), different CuxOy phases were achieved. SEM and AFM analyses unveil the presence of the Cu(0) and copper CuxOy nanoparticles over BC fibrils while the surface of 3D network became more compact and smother for longer heating times. Furthermore, the increase of heating time placed deleterious effect on the structure of BC network leading to decrease of BC crystallinity as well as of the on-set degradation temperature. Notwithstanding, BC-Cu nanocomposites showed excellent antimicrobial activity against E. coli, S. aureus and Salmonella bacteria suggesting potential applications as bactericidal films.

Fabrication of Biocompatible, Functional, and Transparent Hybrid Films Based on Silk Fibroin and Epoxy Silane for Biophotonics.

In this work we explored the fabrication of flexible and transparent hybrids of silk fibroin (SF) and epoxy-modified siloxane for photonic applications. It is well-known that regenerated SF solutions can form free-standing films with high transparency. Although SF has a restricted number of chemically reactive side groups, the main issues of as-cast pristine SF films regard the high solubility into aqueous media, brittleness, and low thermal stability. The design of SF films with enhanced functionality but high transparency triggers new opportunities on a broader range of applications in biophotonics. Here we present a simple, functional, yet remarkably versatile hybrid material derived from silica sol-gel process based on SF protein and (3-glycidyloxypropyl)trimethoxysilane (GPTMS), an organically modified silicon-alkoxide owning a reactive terminal epoxy group. Specifically, we investigated the effect of the addition of GPTMS into SF solutions on the processability, morphology, crystallinity, and mechanical and optical properties of the resulting hybrid films. Highly transparent (ca. 90%) and flexible free-standing hybrid films were achieved. Cell viability assays revealed that the hybrid films are noncytotoxic to rat osteoblast cells even at high GPTMS content (up to 70 wt %). The hybrid films showed enhanced thermal stability and were rich in organic (epoxy) and inorganic (silanol) functional groups according to the content of GPTMS. We also evaluated the successful preparation of high-quality optical red emissive SF hybrid films by loading YVO4:Eu3+ nanoparticles at low concentration (<5 wt %). A meaningful description of the hybrid film structure is reported from the combination of scanning electron and atomic force microscopies, vibrational spectroscopy, solid-state NMR, and X-ray diffraction analyses.

Immunosensor based on immobilization of antigenic peptide NS5A-1 from HCV and silk fibroin in nanostructured films.

The peptide NS5A-1 (PPLLESWKDPDYVPPWHG), derived from hepatitis C virus (HCV) NS5A protein, was immobilized into layer-by-layer (LbL) silk fibroin (SF) films. Deposition was monitored by UV-vis absorption measurements at each bilayer deposited. The interaction SF/peptide film induced secondary structure in NS5A-1 as indicated by fluorescence and circular dichroism (CD) measurements. Voltammetric sensor (SF/NS5A-1) properties were observed when the composite film was tested in the presence of anti-HCV. The peptide-silk fibroin interaction studied here showed new architectures for immunosensors based on antigenic peptides and SF as a suitable immobilization matrix.

MioLab: simulator for cardiac myocyte contractile force of rat based on the dynamics of calcium.

BACKGROUND: The calcium ion (Ca(2+)) is essential in cardiac electrical activity since it is the direct activator of myofilaments, which cause contraction. For this reason, irregular Ca(2+) flow in the cardiac myocyte is one of the main causes of cardiac arrhythmias and contractile dysfunction. In this sense, the formulation of mathematical and computational models of the mammalian ventricular myocyte has played an important role in understanding cardiac physiology. This paper proposes a biophysical model for the rat cardiac myocyte in order to reduce the number of degrees of freedom and provides a mathematical framework that makes computation simpler for our understanding of the complex process of excitation-contraction-relaxation (ECR), uses low-order lumped parameter of the myofilaments and Ca(2+)handling. The model allows the calculation of contractile force mainly based on the dynamics of Ca(2+), provides data on transient Ca(2+)andenables the analysis of the effects of drugs used in the treatment of cardiac arrhythmias. METHODS: The mathematical model which describes the kinetics of cytosolic Ca(2+) and dynamic cross-bridges, was implemented through nine differential equations, auxiliary equations, three 47 biophysical parameters. Each was implemented using C(++) programming and its user-friendly interface in the programming language Delphi. The results of each simulation were stored in a text file and its analysis was shown in a graphical interface using executable programs in Matlab(®). Additionally, the validation model was performed by comparing both the experimental data of Ca(2+) transient and several drug tests. RESULTS: The model satisfactorily reproduced the Ca(2+) transient, as well as the effects of drugs that cause beta-adrenergic stimulation and the inhibition of the Ca(2+) uptake mechanism (SERCA). Changes in the parameters regulating Ca(2+) entry through L-type channels produced the oscillation amplitude of the Ca(2+) transient known as the syndrome of pulses alternans. Changes in parameters related to the Na(+)-Ca(2+) exchange has already stabilized the transient Ca(2+) and produced a decrease in amplitude of the contractile force. CONCLUSION: The simulator proved to be a tool to study and understand the mechanisms that involve the kinetics of Ca(2+) and the dynamics of cross-bridges in the unit heart muscle, as well as a tool to analyze the possible factors that may cause arrhythmias and study the effects of drugs that are used in the treatment of cardiovascular diseases in general.

Ainhum: ressurgimento histórico e científico / Ainhum: historical and scientific come back

Os autores relatam um caso de ainhum, bilateral em um paciente negro de 49 anos de idade. Säo discutidas suas manifestaçoes clínicas, aspectos etitológicos, radiológicos, histopatológicos e tratamento dessa afecçäo. Chama a atençäo o fato de que, embora vários casos já tenham sido relatados no mundo e no Brasil - particularmente na Bahia -, essa patologia descrita em 1867 ainda permanece relativamente mal estudada na literatura ortopédica recente. Trata-se, portanto, de um resgate histórico e científico dessa patologia mutilante do pé, que afeta particularmente a raça negra.