Selective Fabrication of Nanowires with High Aspect Ratios Using a Diffusion Mixing Reaction System for Applications in Temperature Sensing

Soft Bioelectronics for Heart Monitoring

Cardiovascular diseases (CVDs) are a predominant global health concern, accounting for over 17.9 million deaths in 2019, representing approximately 32% of all global fatalities. In North America and Europe, over a million adults undergo cardiac surgeries annually. Despite the benefits, such surgeries pose risks and require precise postsurgery monitoring. However, during the postdischarge period, where monitoring infrastructures are limited, continuous monitoring of vital signals is hindered. In this area, the introduction of implantable electronics is altering medical practices by enabling real-time and out-of-hospital monitoring of physiological signals and biological information postsurgery. The multimodal implantable bioelectronic platforms have the capability of continuous heart sensing and stimulation, in both postsurgery and out-of-hospital settings. Furthermore, with the emergence of machine learning algorithms into healthcare devices, next-generation implantables will benefit artificial intelligence (AI) and connectivity with skin-interfaced electronics to provide more precise and user-specific results. This Review outlines recent advancements in implantable bioelectronics and their utilization in cardiovascular health monitoring, highlighting their transformative deployment in sensing and stimulation to the heart toward reaching truly personalized healthcare platforms compatible with the Sustainable Development Goal 3.4 of the WHO 2030 observatory roadmap. This Review also discusses the challenges and future prospects of these devices.

Robust Long-Nanowire Fabrication by Clean-Phase-Assisted Micro Chemical Pen for Enhanced Bioassay Sensitivity

Long nanowires offer an increased surface area for biomolecule immobilization, facilitating enhanced binding capacity and sensitivity in the detection of target analytes. However, robust long-nanowire fabrication remains a significant challenge. In this paper, we developed a novel construction of a micro chemical pen (MCP), called a clean-assisted micro chemical pen (CAMCP), for robust long-nanowire fabrication. CAMCP, based on localized hydrodynamic flow confinement, was conducted by incorporating a clean phase to effectively dissolve aggregated silver particles in the aspiration channel's shell, thereby enhancing the MCP's longevity by 60.84%, allowing for an 840 μm extension in nanowire patterning capability. A 4600-aspect ratio (length:1200 μm, width: 260 nm) nanowire was fabricated by CAMCP and utilized as a nanowire sensor, showing a 39.7% increase in IgA detection sensitivity compared to a 3000-aspect ratio sensor. Furthermore, the longer nanowire sensor exhibited enhanced signal responses, a higher signal-to-noise ratio, and a lower limit of detection (LOD). The preponderant bioassay performances of the longer nanowire sensor in bioassays, facilitated by CAMCP, open up its possibilities for chemical-synthesis nanowires (NWs) in ultrasensitive biodetection.

Regioselective fabrication of gold nanowires using open-space laminar flow for attomolar protein detection

Gold nanowires are expected to be applied to biosensing due to their advantages, such as high stability and biocompatibility. However, it is still inconvenient to fabricate a single gold nanowire at a precise position, and without a special demanding environment. In this study, we present an open-space laminar flow approach for fabricating a single gold nanowire at a precise position under normal conditions. The fabricated gold nanowire demonstrated excellent biosensing of IgA with an extremely low limit of detection (1 aM).

Wide Dynamic Range Thermometer Based on Luminescent Optical Cavities in Ga2 O3 :Cr Nanowires

Remote temperature sensing at the micro- and nanoscale is key in fields such as photonics, electronics, energy, or biomedicine, with optical properties being one of the most used transducing mechanisms for such sensors. Ga₂ O₃ presents very high chemical and thermal stability, as well as high radiation resistance, becoming of great interest to be used under extreme conditions, for example, electrical and/or optical high-power devices and harsh environments. In this work, a luminescent and interferometric thermometer is proposed based on Fabry-Perot (FP) optical microcavities built on Cr-doped Ga₂ O₃ nanowires. It combines the optical features of the Cr³⁺ -related luminescence, greatly sensitive to temperature, and spatial confinement of light, which results in strong FP resonances within the Cr³⁺ broad band. While the chromium-related R lines energy shifts are adequate for low-temperature sensing, FP resonances extend the sensing range to high temperatures with excellent sensitivity. This thermometry system achieves micron-range spatial resolution, temperature precision of around 1 K, and a wide operational range, demonstrating to work at least in the 150-550 K temperature range. Besides, the temperature-dependent anisotropic refractive index and thermo-optic coefficient of this oxide have been further characterized by comparison to experimental, analytical, and finite-difference time-domain simulation results.

Fluorescent pattern recognition of metal ions by nanoparticles of bovine serum albumin as a chemical nose/tongue

A sensor array mimicking a chemical nose/tongue based on bovine serum albumin nanoparticles (BSANsn) has been developed for the fluorescence pattern recognition of metal ions in biofluids. Three types of BSANsn (BSANs10, BSANs20, and BSANs40) show the same excitation/emission peak at 478/526 nm. According to the differential fluorescence variation, the sensor array shows particular fluorescence response patterns depending upon metal ions. Upon principal component analysis (PCA), it was found that the sensor array can distinguish 18 metal ions clearly at a concentration of as low as 10 μM. Moreover, different concentrations of metal ions and mixed metal ions of diverse kinds or valence states can be differentiated by the sensor in biofluids. In addition, the results were well consistent with those obtained with the traditional ICP-AES method.

A Fluidic Isolation-Assisted Homogeneous-Flow-Pressure Chip-Solid Phase Extraction-Mass Spectrometry System for Online Dynamic Monitoring of 25-Hydroxyvitamin D3 Biotransformation in Cells

It is well known that cell can response to various chemical and mechanical stimuli. Therefore, flow pressure variation induced by sample loading and elution should be small enough to ignore the physical impact on cells when we use a Chip-SPE-MS system for cells. However, most existent Chip-SPE-MS systems ignored the pressure alternation because it is extremely difficult to develop a homogeneous-flow-pressure hyphenated module. Herein, we developed an interesting fluidic isolation-assisted homogeneous-flow-pressure Chip-SPE-MS system and demonstrated that it is adequate for online high-throughput determination and quantification of the 25-hydroxyvitamin D₃ (25(OH)D₃) biotransformation in different cells. Briefly, the homogeneous ambient flow pressure is achieved by fluidic isolation between the cell culture channel and the SPE column, and an automatic sampling probe could accomplish the sample loading and dispensing to fulfill online pretreatment of the sample. Through this new system, the expression levels of 24,25-dihydroxyvitamin D₃ (24,25(OH)₂D₃) can be determined in real time with a detection limit of 2.54 nM. In addition, the results revealed that 25(OH)D₃ metabolic activity differed significantly between normal L-02 cells and cancerous HepG2 cells. Treatment of L-02 cells with a high dose of 25(OH)D₃ was found to increase significant formation of 24,25(OH)₂D₃, but this change was not apparent in HepG2 cells. The presented system promises to be a versatile tool for online accurate molecule biotransformation investigation and drug screening processes.