Mercury (II) sensing using a simple turn-on fluorescent graphene oxide based aptasensor in serum and water samples.

A simple, highly sensitive, and selective fluorometric aptasensing platform based on aptamer and graphene oxide (GO) is proposed for the determination of mercury (II) ion (Hg2+). In the designed assay, two aptamer probes, a carboxy-fluorescein (FAM) labeled aptamer (aptamer A) and its complementary (aptamer B) with partial complement containing several mismatches and GO as the quencher were used. In the absence of Hg2+, both A and B aptamers were adsorbed on the surface of GO by π-π-stacking, leading to fluorescence quenching of FAM due to fluorescence resonance energy transfer (FRET). Upon exposure to Hg2+, the A and B aptamer strands bind Hg2+ and form T-Hg2+-T complexes, leading to the formation of a stable double-stranded aptamer. The double-stranded aptamer is detached from the GO surface, resulting in the recovery of FAM fluorescence. The fluorescence intensity (FI) of the developed sensor was correlated with the Hg2+ concentration under optimized experimental conditions in two wide linear ranges, even in the presence of 10 divalent cations as interferences. The linear ranges were obtained from 200.0 to 900.0 fM and 5.0 to 33.0 pM, a limit of detection (LOD) of 106.0 fM, and a limit of quantification (LOQ) of 321.3 fM. The concentration of Hg2+ was determined in five real samples containing three water and two serum samples, using spiking and standard addition methods and the results were compared with the spiked amounts and atomic absorption (AAS) as standard method respectively, with acceptable recoveries. Furthermore, in the standard addition method, to overcome the effects of matrix influence of real samples in quantitative predictions, the excitation-emission matrix (EEM) data for samples was simultaneously analyzed by multivariate curve resolution with alternating least squares (MCR-ALS) as a second-order standard addition method (SOSAM).

Biomimetic Dehydrogenation of Non-Conventional Lignin Monomers on Cellulose Ferulate Interfaces.

Cellulose ferulate, synthesized by Mitsunobu reaction, is shaped into thin films and also used as an aqueous dispersion to perform artificial lignin polymerization on anchor groups. This biomimetic approach is carried out in a Quartz crystal microbalance with a dissipation monitoring (QCM-D) device to enable online monitoring of the dehydrogenation, applying H2 O2 and adsorbed horseradish peroxidase (HRP). The systematic use of phenylpropanoids with different oxidation states, i.e., ferulic acid, coniferyl aldehyde, coniferyl alcohol, and eugenol allowed to conclude structure-property relationships. Both the deposited material, as well as the surface roughness increased with the hydrophobicity of the monomers. Beyond surface characterizations, py-GC-MS, HSQC NMR spectroscopy and Size exclusion chromatography (SEC) measurements revealed the linkage types ß-ß, ß-5, 5-5, and ß-O-4, as well as the oligomeric character of the dehydrogenation products. All samples possessed an antibacterial activity against B. subtilis and can be used in the field of antimicrobial biomaterials.

Creation of a 3D Goethite-Spongin Composite Using an Extreme Biomimetics Approach.

The structural biopolymer spongin in the form of a 3D scaffold resembles in shape and size numerous species of industrially useful marine keratosan demosponges. Due to the large-scale aquaculture of these sponges worldwide, it represents a unique renewable source of biological material, which has already been successfully applied in biomedicine and bioinspired materials science. In the present study, spongin from the demosponge Hippospongia communis was used as a microporous template for the development of a new 3D composite containing goethite [α-FeO(OH)]. For this purpose, an extreme biomimetic technique using iron powder, crystalline iodine, and fibrous spongin was applied under laboratory conditions for the first time. The product was characterized using SEM and digital light microscopy, infrared and Raman spectroscopy, XRD, thermogravimetry (TG/DTG), and confocal micro X-ray fluorescence spectroscopy (CMXRF). A potential application of the obtained goethite-spongin composite in the electrochemical sensing of dopamine (DA) in human urine samples was investigated, with satisfactory recoveries (96% to 116%) being obtained.

Spongin as a Unique 3D Template for the Development of Functional Iron-Based Composites Using Biomimetic Approach In Vitro.

Marine sponges of the subclass Keratosa originated on our planet about 900 million years ago and represent evolutionarily ancient and hierarchically structured biological materials. One of them, proteinaceous spongin, is responsible for the formation of 3D structured fibrous skeletons and remains enigmatic with complex chemistry. The objective of this study was to investigate the interaction of spongin with iron ions in a marine environment due to biocorrosion, leading to the occurrence of lepidocrocite. For this purpose, a biomimetic approach for the development of a new lepidocrocite-containing 3D spongin scaffold under laboratory conditions at 24 °C using artificial seawater and iron is described for the first time. This method helps to obtain a new composite as "Iron-Spongin", which was characterized by infrared spectroscopy and thermogravimetry. Furthermore, sophisticated techniques such as X-ray fluorescence, microscope technique, and X-Ray diffraction were used to determine the structure. This research proposed a corresponding mechanism of lepidocrocite formation, which may be connected with the spongin amino acids functional groups. Moreover, the potential application of the biocomposite as an electrochemical dopamine sensor is proposed. The conducted research not only shows the mechanism or sensor properties of "Iron-spongin" but also opens the door to other applications of these multifunctional materials.

Electrochemical Sensing of Gallic Acid in Beverages Using a 3D Bio-Nanocomposite Based on Carbon Nanotubes/Spongin-Atacamite.

Gallic acid (GA) is one of the most important polyphenols, being widely used in the food, cosmetic, and pharmaceutical industries due to its biological effects such as antioxidant, antibacterial, anticancer, antiviral, anti-inflammatory, and cardioprotective properties. Hence, simple, fast, and sensitive determination of GA is of particular importance. Considering the fact that GA is an electroactive compound, electrochemical sensors offer great potential for GA quantitation due to their fast response time, high sensitivity, and ease of use. A simple, fast, and sensitive GA sensor was fabricated on the basis of a high-performance bio-nanocomposite using spongin as a natural 3D polymer, atacamite, and multi-walled carbon nanotubes (MWCNTs). The developed sensor showed an excellent response toward GA oxidation with remarkable electrochemical features due to the synergistic effects of 3D porous spongin and MWCNTs, which provide a large surface area and enhance the electrocatalytic activity of atacamite. At optimal conditions by differential pulse voltammetry (DPV), a good linear relationship was obtained between peak currents and GA concentrations in a wild linear range of 500 nM to 1 mM. Subsequently, the proposed sensor was used to detect GA in red wine as well as in green and black tea, confirming its great potential as a reliable alternative to conventional methods for GA determination.

Paradigm Changing Integration Technology for the Production of Flexible Electronics by Transferring Structures, Dies and Electrical Components from Rigid to Flexible Substrates.

Emerging trends like the Internet of Things require an increasing number of different sensors, actuators and electronic devices. To enable new applications, such as wearables and electronic skins, flexible sensor technologies are required. However, established technologies for the fabrication of sensors and actuators, as well as the related packaging, are based on rigid substrates, i.e., silicon wafer substrates and printed circuit boards (PCB). Moreover, most of the flexible substrates investigated until now are not compatible with the aforementioned fabrication technologies on wafers due to their lack of chemical inertness and handling issues. In this presented paper, we demonstrate a conceptually new approach to transfer structures, dies, and electronic components to a flexible substrate by lift-off. The structures to be transferred, including the related electrical contacts and packaging, are fabricated on a rigid carrier substrate, coated with the flexible substrate and finally lifted off from the carrier. The benefits of this approach are the combined advantages of using established semiconductor and microsystem fabrication technologies as well as packaging technologies, such as high precision and miniaturization, as well as a variety of available materials and processes together with those of flexible substrates, such as a geometry adaptivity, lightweight structures and low costs.

Nitrogen and sulfur co-doped carbon quantum dots fluorescence quenching assay for detection of mercury (II).

Mercury is a highly toxic and potentially bioaccumulative heavy metal ion that can cause severe health problems in humans even at very low concentrations. Thus, the development of a simple, rapid, and sensitive assay for the effective detection of mercury ions at trace levels is of great importance. Here, nitrogen and sulfur co-doped carbon quantum dots (N,S-CQD) were synthesized by a simple hydrothermal treatment of chitosan in the presence of thiourea and citric acid with a quantum yield (QY) up to 33.0 % and used as a selective fluorescent probe to detect mercury ions (Hg2+). The effect of pH, ionic strength, and time on the fluorescence intensity of N,S-CQD were investigated and optimized. The synthesized N,S-CQD showed ultrasensitive ability to detect Hg2+ ions in the water samples, also in the presence of 11 interfering metal ions, with a low detection limit (∼4 nM) over a wide linear range from ∼5-160 nM. The sensing performance of N,S-CQD probe in real sample applications was evaluated by the detection of Hg2+ in lake water samples, which confirmed its potential application in environmental analysis.

Biomarkers and Corresponding Biosensors for Childhood Cancer Diagnostics.

Although tremendous progress has been made in treating childhood cancer, it is still one of the leading causes of death in children worldwide. Because cancer symptoms overlap with those of other diseases, it is difficult to predict a tumor early enough, which causes cancers in children to be more aggressive and progress more rapidly than in adults. Therefore, early and accurate detection methods are urgently needed to effectively treat children with cancer therapy. Identification and detection of cancer biomarkers serve as non-invasive tools for early cancer screening, prevention, and treatment. Biosensors have emerged as a potential technology for rapid, sensitive, and cost-effective biomarker detection and monitoring. In this review, we provide an overview of important biomarkers for several common childhood cancers. Accordingly, we have enumerated the developed biosensors for early detection of pediatric cancer or related biomarkers. This review offers a restructured platform for ongoing research in pediatric cancer diagnostics that can contribute to the development of rapid biosensing techniques for early-stage diagnosis, monitoring, and treatment of children with cancer and reduce the mortality rate.

Impact of Non-Accelerated Aging on the Properties of Parylene C.

The polymer Parylene combines a variety of excellent properties and, hence, is an object of intensive research for packaging applications, such as the direct encapsulation of medical implants. Moreover, in the past years, an increasing interest for establishing new applications for Parylene is observed. These include the usage of Parylene as a flexible substrate, a dielectric, or a material for MEMS, e.g., a bonding adhesive. The increasing importance of Parylene raises questions regarding the long-term reliability and aging of Parylene as well as the impact of the aging on the Parylene properties. Within this paper, we present the first investigations on non-accelerated Parylene C aging for a period of about five years. Doing so, free-standing Parylene membranes were fabricated to investigate the barrier properties, the chemical stability, as well as the optical properties of Parylene in dependence on different post-treatments to the polymer. These properties were found to be excellent and with only a minor age-related impact. Additionally, the mechanical properties, i.e., the Young's modulus and the hardness, were investigated via nano-indentation over the same period of time. For both mechanical properties only, minor changes were observed. The results prove that Parylene C is a highly reliable polymer for applications that needs a high long-term stability.

Growing of Artificial Lignin on Cellulose Ferulate Thin Films.

Thin films of cellulose ferulate were designed to study the formation of dehydrogenation polymers (DHPs) on anchor groups of the surface. Trimethylsilyl (TMS) cellulose ferulate with degree of substitution values of 0.35 (ferulate) and 2.53 (TMS) was synthesized by sophisticated polysaccharide chemistry applying the Mitsunobu reaction. The biopolymer derivative was spin-coated into thin films to yield ferulate moieties on a smooth cellulose surface. Dehydrogenative polymerization of coniferyl alcohol was performed in a Quartz crystal microbalance with a dissipation monitoring device in the presence of H2O2 and adsorbed horseradish peroxidase. The amount of DHP formed on the surface was found to be independent of the base layer thickness from 14 to 75 nm. Pyrolysis-GC-MS measurements of the DHP revealed ß-O-4 and ß-5 linkages. Mimicking lignification of plant cell walls on highly defined model films enables reproducible investigations of structure-property relationships.

High-Performance Three-Dimensional Spongin-Atacamite Biocomposite for Electrochemical Nonenzymatic Glucose Sensing.

The design of sensitive and cost-effective biocomposite materials with high catalytic activity for the effective electrooxidation of glucose plays a key role in developing enzyme-free glucose sensors. The porous three-dimensional (3D) spongin scaffold of marine sponge origin provides an excellent template for the growth of atacamite crystals and improves the activity of atacamite as a catalyst. By using the design of experiment method, the influence of different parameters on the electrode efficiency was optimized. The optimized sensor based on spongin-atacamite showed distinguished performance toward glucose with two linear ranges of 0.4-200 µM and 0.2-10 mM and high sensitivities of 3908.4 and 600.5 µA mM-1 cm-2, respectively. Importantly, the designed sensor exhibited strong selectivity and favorable stability, reproducibility, and repeatability. The performance in the real application was estimated by glucose detection in spiked human blood serum samples, which verified its great potential as a reliable platform for enzyme-free glucose sensing.

Product Integration of Established Crash Sensors for Safety Applications in Lightweight Vehicles.

The functionality of products increases when more sensors are used. This trend also affects future automobiles and becomes even more relevant in connected and autonomous applications. Concerning automotive lightweight design, carbon fibre-reinforced polymers (CFRP) are suitable materials. However, their drawbacks include the relatively high manufacturing costs of CFRP components in addition to the difficulty of recycling. To compensate for the increased expenditure, the integration of automotive sensors in CFRP vehicle structures provides added value. As a new approach, established sensors are integrated into fibre-reinforced polymer (FRP) structures. The sensors are usually mounted to the vehicle. The integration of sensors into the structure saves weight and space. Many other approaches specifically develop new sensors for integration into FRP structures. With the new approach, there is no need for elaborate development of new sensors since established sensors are used. The present research also showed that the range of applications of the sensors can be extended by the integration. The present paper outlines the functional behaviour of the integrated sensor utilized for crashing sensing. First of all, the integration quality of the sensor is relevant. Different requirements apply to the usual mounting of the sensor. The self-sensing structure must fulfil those requirements. Moreover, unfamiliar characteristics of the new surrounding structure might affect the sensing behaviour. Thus, the sensing behaviour of the self-sensing composite was analyzed in detail. The overarching objective is the general integration of sensors in products with reasonable effort.

Non-Coding RNA-Based Biosensors for Early Detection of Liver Cancer.

Primary liver cancer is an aggressive, lethal malignancy that ranks as the fourth leading cause of cancer-related death worldwide. Its 5-year mortality rate is estimated to be more than 95%. This significant low survival rate is due to poor diagnosis, which can be referred to as the lack of sufficient and early-stage detection methods. Many liver cancer-associated non-coding RNAs (ncRNAs) have been extensively examined to serve as promising biomarkers for precise diagnostics, prognostics, and the evaluation of the therapeutic progress. For the simple, rapid, and selective ncRNA detection, various nanomaterial-enhanced biosensors have been developed based on electrochemical, optical, and electromechanical detection methods. This review presents ncRNAs as the potential biomarkers for the early-stage diagnosis of liver cancer. Moreover, a comprehensive overview of recent developments in nanobiosensors for liver cancer-related ncRNA detection is provided.

Extreme Biomimetics: Designing of the First Nanostructured 3D Spongin-Atacamite Composite and its Application.

The design of new composite materials using extreme biomimetics is of crucial importance for bioinspired materials science. Further progress in research and application of these new materials is impossible without understanding the mechanisms of formation, as well as structural features at the molecular and nano-level. It presents a challenge to obtain a holistic understanding of the mechanisms underlying the interaction of organic and inorganic phases under conditions of harsh chemical reactions for biopolymers. Yet, an understanding of these mechanisms can lead to the development of unusual-but functional-hybrid materials. In this work, a key way of designing centimeter-scale macroporous 3D composites, using renewable marine biopolymer spongin and a model industrial solution that simulates the highly toxic copper-containing waste generated in the production of printed circuit boards worldwide, is proposed. A new spongin-atacamite composite material is developed and its structure is confirmed using neutron diffraction, X-ray diffraction, high-resolution transmission electron microscopy/selected-area electron diffraction, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, and electron paramagnetic resonance spectroscopy. The formation mechanism for this material is also proposed. This study provides experimental evidence suggesting multifunctional applicability of the designed composite in the development of 3D constructed sensors, catalysts, and antibacterial filter systems.

Structure-Function Relationships of Nanocarbon/Polymer Composites for Chemiresistive Sensing: A Review.

Composites of organic compounds and inorganic nanomaterials provide novel sensing platforms for high-performance sensor applications. The combination of the attractive functionalities of nanomaterials with polymers as an organic matrix offers promising materials with tunable electrical, mechanical, and chemisensitive properties. This review mainly focuses on nanocarbon/polymer composites as chemiresistors. We first describe the structure and properties of carbon nanofillers as reinforcement agents used in the manufacture of polymer composites and the sensing mechanism of developed nanocomposites as chemiresistors. Then, the design and synthesizing methods of polymer composites based on carbon nanofillers are discussed. The electrical conductivity, mechanical properties, and the applications of different nanocarbon/polymer composites for the detection of different analytes are reviewed. Lastly, challenges and the future vision for applications of such nanocomposites are described.

Molecularly Imprinted Polymer-Based Sensors for Priority Pollutants.

Globally, there is growing concern about the health risks of water and air pollution. The U.S. Environmental Protection Agency (EPA) has developed a list of priority pollutants containing 129 different chemical compounds. All of these chemicals are of significant interest due to their serious health and safety issues. Permanent exposure to some concentrations of these chemicals can cause severe and irrecoverable health effects, which can be easily prevented by their early identification. Molecularly imprinted polymers (MIPs) offer great potential for selective adsorption of chemicals from water and air samples. These selective artificial bio(mimetic) receptors are promising candidates for modification of sensors, especially disposable sensors, due to their low-cost, long-term stability, ease of engineering, simplicity of production and their applicability for a wide range of targets. Herein, innovative strategies used to develop MIP-based sensors for EPA priority pollutants will be reviewed.

Dry sonication process for preparation of hybrid structures based on graphene and carbon nanotubes usable for chemical sensors.

The combination of graphene (G) and multi-walled carbon nanotubes (MWCNTs) creates three-dimensional hybrid structures particularly suitable as next-generation electrical interface materials. Nevertheless, efficient mixing of the nanopowders is challenging, unless previous disaggregation and eventual surface modification of both is reached. To avoid use of solvents and multistep purification process for synthesis of stable G/MWCNTs hybrids, herein, a novel dry method based on an air sonication process was used. Taking advantage from the vigorous turbulent currents generated by powerful ultrasonication in air that induces strong thermal convection or radiation to and from the particles, it simultaneously ensures disentanglement of the large MWCNT bundles and G exfoliation and their only mild surface modifications. By changing the ratio between MWCNTs and G, a range of hybrids was obtained, different in surface morphology and chemistry. These hybrids have shown great potential as sensing material for designing mass-based sensors for toxic gases and chemiresistor for vapors detection.

Highly efficient sunitinib release from pH-responsive mHPMC@Chitosan core-shell nanoparticles.

This study reports developing novel smart drug delivery systems (DDS) that have great importance in anticancer therapeutics. The magnetic hydroxypropyl methylcellulose (mHPMC) synthesized via in situ method and introduced in the fabrication of tripolyphosphate (TPP)-cross-linked chitosan core-shell nano-carriers (mHPMC@Chitosan). The TPP-cross-linked mHPMC@Chitosan nano-carriers then characterized using TEM, SEM/EDS, DLS, XPS, FTIR, TGA, XRD, and VSM. The encapsulation efficiency showed high capacity of loading for sunitinib malate (above 86 % for all samples). At pH 7.4, the minimum content of drug release was observed for all samples fabricated with variable contents of chitosan. At pH 4.5, the effect of chitosan content revealed that the rate of sunitinib release tends to decrease as its content increased. During two days, 44 and 93 % of the loaded sunitinib released from carriers containing high and low contents of chitosan, respectively. Besides, this mHPMC@Chitosan core shell nano-carrier shown pH-sensitive drug release.

Rational Design of Molecularly Imprinted Polymers Using Quaternary Ammonium Cations for Glyphosate Detection.

Molecularly imprinted polymers have emerged as cost-effective and rugged artificial selective sorbents for combination with different sensors. In this study, quaternary ammonium cations, as functional monomers, were systematically evaluated to design imprinted polymers for glyphosate as an important model compound for electrically charged and highly water-soluble chemical compounds. To this aim, a small pool of monomers were used including (3-acrylamidopropyl)trimethylammonium chloride, [2-(acryloyloxy)ethyl]trimethylammonium chloride, and diallyldimethylammonium chloride. The simultaneous interactions between three positively charged monomers and glyphosate were preliminary evaluated using statistical design of the experiment method. Afterwards, different polymers were synthesized at the gold surface of the quartz crystal microbalance sensor using optimized and not optimized glyphosate-monomers ratios. All synthesized polymers were characterized using atomic force microscopy, contact angle, Fourier-transform infrared, and X-ray photoelectron spectroscopy. Evaluated functional monomers showed promise as highly efficient functional monomers, when they are used together and at the optimized ratio, as predicted by the statistical method. Obtained results from the modified sensors were used to develop a simple model describing the binding characteristics at the surface of the different synthesized polymers. This model helps to develop new synthesis strategies for rational design of the highly selective imprinted polymers and to use as a sensing platform for water soluble and polar targets.

Sol-Gel Derived Hydroxyapatite Coatings for Titanium Implants: A Review.

With the growing demands for bone implant therapy, titanium (Ti) and its alloys are considered as appropriate choices for the load-bearing bone implant substitutes. However, the interaction of bare Ti-based implants with the tissues is critical to the success of the implants for long-term stability. Thus, surface modifications of Ti implants with biocompatible hydroxyapatite (HAp) coatings before implantation is important and gained interest. Sol-gel is a potential technique for deposition the biocompatible HAp and has many advantages over other methods. Therefore, this review strives to provide widespread overview on the recent development of sol-gel HAp deposition on Ti. This study shows that sol-gel technique was able to produce uniform and homogenous HAp coatings and identified the role of surface pretreatment of Ti substrate, optimizing the sol-gel parameters, substitution, and reinforcement of HAp on improving the coating properties. Critical factors that influence on the characteristics of the deposited sol-gel HAp films as corrosion resistance, adhesion to substrate, bioactivity, morphological, and structural properties are discussed. The review also highlights the critical issues, the most significant challenges, and the areas requiring further research.