Transducer Technologies for Biosensors and Their Wearable Applications.

The development of new biosensor technologies and their active use as wearable devices have offered mobility and flexibility to conventional western medicine and personal fitness tracking. In the development of biosensors, transducers stand out as the main elements converting the signals sourced from a biological event into a detectable output. Combined with the suitable bio-receptors and the miniaturization of readout electronics, the functionality and design of the transducers play a key role in the construction of wearable devices for personal health control. Ever-growing research and industrial interest in new transducer technologies for point-of-care (POC) and wearable bio-detection have gained tremendous acceleration by the pandemic-induced digital health transformation. In this article, we provide a comprehensive review of transducers for biosensors and their wearable applications that empower users for the active tracking of biomarkers and personal health parameters.

Artifacts in cranial MRI caused by extracranial foreign bodies and analysis of these foreign bodies.

PURPOSE: The purpose of our study was to conduct a chemical analysis of extracranial foreign bodies (FBs) causing artifacts in cranial magnetic resonance imaging (MRI) and to investigate the association between chemical composition, magnetic susceptibility, and artifact size. MATERIALS AND METHODS: A total of 12 patients were included in the study. The FBs responsible for the artifacts were visualized using cranial computed tomography (CT). Artifact-causing FBs were removed from the scalps of 10 patients and analyzed using scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction spectroscopy (X-RD), and Fourier-transform infrared spectroscopy (FT-IR). The magnetic susceptibility of the samples was determined using the reference standard material MnCl2.6H2O. The volume of the MRI artifacts was measured in cubic centimeters (cm3). RESULTS: EDS results demonstrated that the mean Fe ratio was 5.82% in the stone samples and 0.08% in the glass samples. Although no phase peaks were detected in the X-RD spectra of the glass samples, peaks of Fe2O3, Al2Ca (SiO4) were detected in the X-RD spectra of the stone samples. The FT-IR spectra revealed metal oxide peaks corresponding to Fe, Al, in the stone samples and peaks confirming Al2SiO5 and Na2SiO3 structures in the glass samples. The mean volumes of the MRI artifacts produced by the stone and glass samples were 5.9 cm3 and 2.5 cm3, respectively. CONCLUSIONS: Artifacts caused by extracranial FBs containing metal/metal oxide components are directly associated with their chemical composition and the artifact size are also related to element composition and magnetic susceptibility.

Investigation of molecular structure and solvent/temperature effect on tautomerism in (E)-4,6-dibromo-3-methoxy-2-[(p-tolylimino)methyl]phenol, a new thermochromic Schiff base, by using XRD, FT-IR, UV-vis, NMR and DFT methods.

The molecular structure and the solvent/temperature effect on the tautomerism in a new Schiff base, (E)-4,6-dibromo-3-methoxy-2-[(p-tolylimino)methyl]phenol, were investigated using spectroscopic (NMR, UV-vis, FT-IR), crystallographic (XRD), computational (DFT and TD-DFT) methods and harmonic oscillator model of aromaticity (HOMA). The XRD, DFT and FT-IR results show that the compound exists in the phenol-imine form in the solid state. HOMA indices support the aromatic structure of the compound. DFT calculations were performed to understand proton transfer process and relatively close values were obtained for the energies of tautomers. UV-vis studies prove the solvent dependence of the tautomerism in the compound by revealing the existence of both phenol-imine and keto-amine forms in polar solvents and only the phenol-imine form in apolar solvent. The TD-DFT results for the electronic transitions lead to the same conclusion as the absorption spectra. 1H NMR and 13C NMR studies at room and low (-60 °C) temperatures indicate that the tautomeric equilibrium occurs rapidly in the compound. Therefore, it is difficult to observe two tautomers. However, the presence of tautomeric structures is clearly seen in acetone­d6, alternatively underlying the solvent and temperature dependence of tautomerism in the title compound.

Temperature Gradients Drive Bulk Flow Within Microchannel Lined by Fluid-Fluid Interfaces.

Surface tension gradients induce Marangoni flow, which may be exploited for fluid transport. At the micrometer scale, these surface-driven flows can be quite significant. By introducing fluid-fluid interfaces along the walls of microfluidic channels, bulk fluid flows driven by temperature gradients are observed. The temperature dependence of the fluid-fluid interfacial tension appears responsible for these flows. In this report, the design concept for a biocompatible microchannel capable of being powered by solar irradiation is provided. Using microscale particle image velocimetry, a bulk flow generated by apparent surface tension gradients along the walls is observed. The direction of flow relative to the imposed temperature gradient agrees with the expected surface tension gradient. The phenomenon's ability to replace bulky peripherals, like traditional syringe pumps, on a diagnostic microfluidic device that captures and detects leukocyte subpopulations within blood is demonstrated. Such microfluidic devices may be implemented for clinical assays at the point of care without the use of electricity.

Noble metal nanoparticles supported on activated carbon: Highly recyclable catalysts in hydrogen generation from the hydrolysis of ammonia borane.

Noble metal nanoparticles including rhodium, ruthenium and palladium have been extensively used in catalysis field. Since their limited abundance and high cost, many methods have been developed to obtain highly active and recyclable catalysts. In this work, Rh3+, Ru3+, Pd2+ ions were impregnated on activated carbon derived from pumpkin stalk in distilled water and then reduced with sodium borohydride to form Rh0, Ru0, Pd0 nanoparticles on the surface of carbon. The analyses show that these nanoparticles were successfully dispersed on the activated carbon. Rh0, Ru0 and Pd0 nanoparticles on activated carbon provide a turnover frequency value of 188 min-1, 235 min-1 and 40 min-1, respectively, at 25.0 ±â€¯0.1 °C. They preserve their activity even after multiple use in H2 generation from the hydrolysis of ammonia borane.

3D-Printed Biodegradable Microswimmer for Theranostic Cargo Delivery and Release.

Untethered mobile microrobots have the potential to leverage minimally invasive theranostic functions precisely and efficiently in hard-to-reach, confined, and delicate inner body sites. However, such a complex task requires an integrated design and engineering, where powering, control, environmental sensing, medical functionality, and biodegradability need to be considered altogether. The present study reports a hydrogel-based, magnetically powered and controlled, enzymatically degradable microswimmer, which is responsive to the pathological markers in its microenvironment for theranostic cargo delivery and release tasks. We design a double-helical architecture enabling volumetric cargo loading and swimming capabilities under rotational magnetic fields and a 3D-printed optimized 3D microswimmer (length = 20 µm and diameter = 6 µm) using two-photon polymerization from a magnetic precursor suspension composed from gelatin methacryloyl and biofunctionalized superparamagnetic iron oxide nanoparticles. At normal physiological concentrations, we show that matrix metalloproteinase-2 (MMP-2) enzyme could entirely degrade the microswimmer in 118 h to solubilized nontoxic products. The microswimmer rapidly responds to the pathological concentrations of MMP-2 by swelling and thereby boosting the release of the embedded cargo molecules. In addition to delivery of the drug type of therapeutic cargo molecules completely to the given microenvironment after full degradation, microswimmers can also release other functional cargos. As an example demonstration, anti-ErbB 2 antibody-tagged magnetic nanoparticles are released from the fully degraded microswimmers for targeted labeling of SKBR3 breast cancer cells in vitro toward a potential future scenario of medical imaging of remaining cancer tissue sites after a microswimmer-based therapeutic delivery operation.

Controllable switching between planar and helical flagellar swimming of a soft robotic sperm.

Sperm cells undergo a wide variety of swimming patterns by a beating flagellum to maintain high speed regardless of the rheological and physical properties of the background fluid. In this work, we develop and control a soft robotic sperm that undergoes controllable switching between swimming modes like biological sperm cells. The soft robotic sperm consists of a magnetic head and an ultra-thin flexible flagellum, and is actuated using external magnetic fields. We observe that out-of-plane wobbling of the head results in helical wave propagation along the flagellum, whereas in-plane wobbling achieves planar wave propagation. Our theoretical predictions and experimental results show the ability of the soft robotic sperm to change its swimming speed by tuning the beating frequency of its flagellum and the propulsion pattern. The average speed of the soft robotic sperm increases by factors of 2 and 1.2 in fluids with viscosity of 1 Pa.s and 5 Pa.s at relatively low actuation frequencies, respectively, when they switch between planar to helical flagellar propulsion.

Swimming Back and Forth Using Planar Flagellar Propulsion at Low Reynolds Numbers.

Peritrichously flagellated Escherichia coli swim back and forth by wrapping their flagella together in a helical bundle. However, other monotrichous bacteria cannot swim back and forth with a single flagellum and planar wave propagation. Quantifying this observation, a magnetically driven soft two-tailed microrobot capable of reversing its swimming direction without making a U-turn trajectory or actively modifying the direction of wave propagation is designed and developed. The microrobot contains magnetic microparticles within the polymer matrix of its head and consists of two collinear, unequal, and opposite ultrathin tails. It is driven and steered using a uniform magnetic field along the direction of motion with a sinusoidally varying orthogonal component. Distinct reversal frequencies that enable selective and independent excitation of the first or the second tail of the microrobot based on their tail length ratio are found. While the first tail provides a propulsive force below one of the reversal frequencies, the second is almost passive, and the net propulsive force achieves flagellated motion along one direction. On the other hand, the second tail achieves flagellated propulsion along the opposite direction above the reversal frequency.

Soft erythrocyte-based bacterial microswimmers for cargo delivery.

Bacteria-propelled biohybrid microswimmers have recently shown to be able to actively transport and deliver cargos encapsulated into their synthetic constructs to specific regions locally. However, usage of synthetic materials as cargo carriers can result in inferior performance in load-carrying efficiency, biocompatibility, and biodegradability, impeding clinical translation of biohybrid microswimmers. Here, we report construction and external guidance of bacteria-driven microswimmers using red blood cells (RBCs; erythrocytes) as autologous cargo carriers for active and guided drug delivery. Multifunctional biohybrid microswimmers were fabricated by attachment of RBCs [loaded with anticancer doxorubicin drug molecules and superparamagnetic iron oxide nanoparticles (SPIONs)] to bioengineered motile bacteria, Escherichia coli MG1655, via biotin-avidin-biotin binding complex. Autonomous and on-board propulsion of biohybrid microswimmers was provided by bacteria, and their external magnetic guidance was enabled by SPIONs loaded into the RBCs. Furthermore, bacteria-driven RBC microswimmers displayed preserved deformability and attachment stability even after squeezing in microchannels smaller than their sizes, as in the case of bare RBCs. In addition, an on-demand light-activated hyperthermia termination switch was engineered for RBC microswimmers to control bacteria population after operations. RBCs, as biological and autologous cargo carriers in the biohybrid microswimmers, offer notable advantages in stability, deformability, biocompatibility, and biodegradability over synthetic cargo-carrier materials. The biohybrid microswimmer design presented here transforms RBCs from passive cargo carriers into active and guidable cargo carriers toward targeted drug and other cargo delivery applications in medicine.