Monitoring magnesium degradation using microdialysis and fabric-based biosensors

This paper describes the development of a monitoring system capable of detecting the concentration of magnesium ions (Mg2+) released during the degradation of magnesium implants. The system consists of a microdialysis probe that samples fluid adjacent to the implant and a catalytic biosensor specific to Mg2+ ions. The biosensor was fabricated on a cotton fabric platform, in which a mixture of glycerol kinase and glycerol-3-phosphate oxidase enzymes was immobilized on the fabric device via a simple matrix entrapment technique of the cotton fibers. Pure magnesium was used as the implant material. Subsequently, the concentration of ions released from the degradation of the magnesium specimen in Ringer’s solution was evaluated using cyclic voltammetry technique. The device demonstrated a pseudo-linear response from 0.005 to 0.1 mmol L−1 with a slope of 67.48 μA mmol−1 L. Detectable interfering species were lesser than 1% indicating a high selectivity of the fabric device. Furthermore, the device requires only 3 μL of fluid sample to complete the measurement compared to spectroscopic method (±50 μL), hence providing a higher temporal resolution and reduced sampling time. The system could potentially provide a real time assessment of the degradation behavior, a new studied aspect in biodegradable metals research

Textile/Al2O3-TiO2 nanocomposite as an antimicrobial and radical scavenger wound dressing

Improving the antimicrobial activity and radical scavenging ability of a textile-based nanocomposite (textile/TiO2, textile/Al2O3/TiO2, textile/Al2O3 and textile/Al2O3-TiO2 bimetal oxide nanocomposite) is the key issue in developing a good and flexible wound dressing. In this work, flexible textile attached with Al2O3-TiO2 nanoparticles was prepared by dipping the textile in a suspension containing Al2O3-TiO2 nanoparticles (150 mmol l-1). The mean radical scavenging ability for textile/TiO2, textile/Al2O3/TiO2, textile/Al2O3 and textile/Al2O3-TiO2 bimetal oxide nanocomposites as measured by liquid ultraviolet visible spectroscopy (UV-Vis) coupled with dependence formula was 0.2%, 35.5%, 35.0% and 38.2%, respectively. Based on the X-ray diffraction (XRD) patterns, the preface reactive oxygen species (ROS) scavenging ability shown by the textile/Al2O3-TiO2 bimetal oxide nanocomposite is most probably caused by the crystal structure concluding in a corundum-like structure, with Al3+ ions filling the octahedral sites in the lattice. Increased antimicrobial activity measured by optical density at 600 nm recorded for textile/Al2O3-TiO2 bimetal oxide nanocomposites showed better interaction between Al2O3 and TiO2 nanoparticles. This good interaction is expected to lead to better antimicrobial and radical scavenging ability as shown by the E. coli and human skin fibroblast (HSF) cytotoxicity tests, respectivel

A proposed mechanism of textile/Al2O3–TiO2 bimetal oxide nanocomposite as an antimicrobial agent

The textile/Al2O3–TiO2 bimetal oxide nanocomposite has been developed as an antimicrobial agent, but its antimicrobial mechanism has still not been clarified. The Al2O3–TiO2 bimetal oxide nanoparticle has been reported as a radical scavenger. This study focuses on investigating the antimicrobial mechanism of the textile/Al2O3–TiO2 bimetal oxide nanocomposite against Escherichia coli and their interaction with cell envelope biomolecules. L-α-Phosphatidyl ethanolamine (PE) is used as a model of bacteria to investigate the antimicrobial mechanism of this nanocomposite. The antimicrobial activity of the textile/Al2O3–TiO2 bimetal oxide nanocomposite was investigated by using attenuated total reflectance/Fourier transform infrared (ATR-FTIR) and UV–Vis, while the toxicity of this nanocomposite was also examined through tissue culture test against a fibroblast skin cell. The ATR-FTIR used was able to confirm the destroyed cell envelope of the bacteria. The amounts of reactive oxygen species (ROS) were analyzed by UV–Vis spectroscopy and the toxicity of this nanocomposite was also examined by reacting tissue culture against the fibroblast skin cell. Overall, the antimicrobial mechanism of this textile nanocomposite was first by the attachment of this nanocomposite through the attachment of this nanoparticle to the surface of PE (as the model of bacteria) by hydrogen binding, and then nanoparticles can destroy the cell wall of bacteria through oxidation reaction by the produced ROS. Finally, these nanoparticles scavenged the ROS free radical. Therefore, the attached nanoparticles attached on textile can kill bacteria without any ROS free radical remaining in human body. These results suggest that the antimicrobial mechanism of this nanocomposite is mostly different due to the scavenger ability of this nanocomposite and its lower toxicity

Development of an electrocardiogram based biometric identification system: a case study in the university

This paper focuses on the electrocardiogram (ECG) based biometric identification system in the university scenario as an alternative to the traditional methods being used nowadays. There are a lot of researches and studies about ECG based biometric system where some of them showed positive result. However, ECG based biometric system in the university scenario is under-researched. Therefore, this issue will be the main focus of our study. A total of five subjects were used for experimentation purposes. A bandpass filter is used to remove unwanted portion of the signal. Unique features are extracted from these filtered ECG signals. Later, Multilayer Perceptron and Naïve Bayes are used to classify the subjects using the discriminant features. Based on the experimentation results, classification accuracies of 90% and 80 % were achieved which suggest the capability of our proposed system to identify individuals. The result provides an alternative mechanism to detect a person besides using the traditional methods

Physical and electrochemical appraisal of cotton textile modified with polypyrrole and graphene/reduced graphene oxide for flexible electrode

The aim of this study was to prepare a flexible fabric electrode for electronic devices. Cotton fabric (CT) was used as the substrate for coating graphene oxide (GO) and reduced graphene oxide (RGO) as electroactive materials, then subjected to the chemical polymerization of polypyrrole (PPy). The sheet resistances and surface morphologies of the as-prepared composite textiles were evaluated by means of using van der Pauw technique and FESEM, respectively. XPS results showed a reduction of around 17% in the ratio of O/C in RGO/CT in comparison with the GO/CT, which could be related to the reduction of GO to RGO. The PPy/RGO/CT composite fabric exhibited sheet resistance of 7.5 Ω/sq, whereas PPy/GO/CT samples presented a sheet resistance of 308.3 Ω/sq. Charge-transfer resistance of PPy/GO/CT was 10 times of PPy/RGO/CT, which showed the insulating role of GO in this composite. Therefore, PPy/RGO/CT can hold a significant promise in flexible electrode applications

Optimization of reduced GO-Based cotton electrodes for wearable electrocardiography

The quality of Electrocardiography (ECG) signal is dependent on the electrode's performance. Comfort and long-term monitoring are the main benefits of a dry and flexible electrode compared to conventional silver/silver chloride (Ag/AgCl) electrode. The main objective of this study is to develop high performance textile-based electrode by optimising fabrication method and electrode design. Cotton fabric was dipped into graphene oxide (GO), followed by reduction process to form reduced graphene oxide-cotton (rGOC), where L-ascorbic acid (C6H8O6) was used as the reducing agent. Conductivity and skin-electrode interface impedance of the fabricated cotton were characterized using Four-point probe (Van der Pauw) and Potentiostat, respectively. This study focuses on the investigation of electrode design that includes fabrication methods, electrode sizes and shapes. The performance of the reduced GO-based cotton (rGOC) electrode in terms of ECG signal quality was compared to conventional Ag/AgCl electrode and metal clamp under static and dynamic wearable conditions. Results from the conducted experiments show that the fabricated electrode's performance is influenced by dipping time and electrode design, with circle-shape electrode shows the highest conductivity (up to 9k S/m at 1 cm2 area) compared to square- and rectangular-shape electrodes (<8k S/m and 14.55 S/m, respectively, at 1 cm2 area). The circle-shape rGOC electrode's performed better (SNR 14.85±0.22 dB) than Ag/AgCl electrode (SNR 11.26±0.18 dB) and metal clamp (SNR 12.28±0.72 dB) in capturing static ECG signal. A wearable circle rGOC electrode with 1.7 cm radius performed also similarly under static (SNR 32.60±0.72 dB) and dynamic (SNR 30.27±1.37 dB) ECG monitoring, respectively

Oxygen reduction reaction mechanism on a phosporus-doped pyrolyzed graphitic Fe/N/C catalyst

The oxygen reduction reaction (ORR) mechanism on the active sites of a phosphorus-doped pyrolyzed Fe/N/C catalyst is examined by using density functional theory based calculations. The introduction of the phosphorus dopant creates three initial possible active sites for the ORR i.e., FeN4, C–N and P-doped sites. In the presence of O2, the P-doped sites become passivated while the rest of the catalyst sites are still functional. The ORR profile for the associative mechanism (the O2 molecule is reduced from its molecular form) on the FeN4 site is practically unaffected by the presence of the neighboring P[double bond, length as m-dash]O site. However, the ORR profile for the dissociative mechanism (the O2 molecule is reduced from its dissociated form) on the FeN4 site is significantly improved as compared to that on the undoped Fe/N/C catalyst system. This phenomenon is mainly induced by the distortion of C–C networks due to the presence of the neighboring FeN4 and P[double bond, length as m-dash]O sites, which leads to the stabilization of the *OH adsorption state on the C atoms next to the FeN4 site

Cotton fiber-based assay with time-based microfluidic absorption sampling for point-of-care applications

Aim: Time-based microfluidic absorption sampling was proposed using cotton fiber-based device made in swab stick. The assay was optimized and compared with conventional pipetted drop sampling using the same device. Materials & methods: Reagents were integrated into cotton fiber device for assessing concentration of analytes by the colorimetric detection method through time-based absorption sampling microfluidic system. All assay parameters were first optimized using conventional pipette-based drop sampling. Results: The color intensity is linear in the relevant concentration range of the analytes. The LOD are 0.189 mM for glucose and 6.56 μM for nitrite, respectively. These values are better than conventional drop sampling. The fiber-containing swab itself functions as sampling, assay and calibration device. Conclusion: Microfluidic cotton fiber-based assay device was fabricated and can determine analyte concentration in artificial salivary samples, colorimetrically, by time-based absorption sampling without the need of complex equipments