Black Phosphorus-Based Reusable Biosensor Platforms for the Ultrasensitive Detection of Cortisol in Saliva.

A black phosphorus (BP)-based reusable biosensor platform is developed for the repeated and real-time detection of cortisol using antibody-conjugated magnetic particle (MP) structures as a refreshable receptor. Here, we took advantage of the low-noise characteristics of a mechanically exfoliated BP-based field-effect transistor (FET) and hybridized it with anti-cortisol antibody-functionalized MPs to build a highly sensitive cortisol sensor. This strategy allowed us to detect cortisol down to 1 aM in real time and discriminate cortisol from other hormones. In this case, we could easily remove MPs with used antibodies from the surface of a BP-FET and reuse the chip for up to eight repeated sensing operations. Moreover, since our platform could be fabricated using conventional photolithography techniques and the sensor can be reused multiple times, one should be able to significantly reduce operation costs for practical applications. Furthermore, this method could be utilized to detect different hormones with high sensitivity and selectivity in complex environments such as artificial saliva solutions. In this respect, our reusable BP-FET biosensing platform can be a powerful tool for versatile applications such as clinical diagnosis and basic biological analysis by conjugating various antibodies.

Nano-storage wires.

We report the development of "nano-storage wires" (NSWs), which can store chemical species and release them at a desired moment via external electrical stimuli. Here, using the electrodeposition process through an anodized aluminum oxide template, we fabricated multisegmented nanowires composed of a polypyrrole segment containing adenosine triphosphate (ATP) molecules, a ferromagnetic nickel segment, and a conductive gold segment. Upon the application of a negative bias voltage, the NSWs released ATP molecules for the control of motor protein activities. Furthermore, NSWs can be printed onto various substrates including flexible or three-dimensional structured substrates by direct writing or magnetic manipulation strategies to build versatile chemical storage devices. Since our strategy provides a means to store and release chemical species in a controlled manner, it should open up various applications such as drug delivery systems and biochips for the controlled release of chemicals.

Nanovesicle-based bioelectronic nose platform mimicking human olfactory signal transduction.

We developed a nanovesicle-based bioelectronic nose (NBN) that could recognize a specific odorant and mimic the receptor-mediated signal transmission of human olfactory systems. To build an NBN, we combined a single-walled carbon nanotube-based field effect transistor with cell-derived nanovesicles containing human olfactory receptors and calcium ion signal pathways. Importantly, the NBN took advantages of cell signal pathways for sensing signal amplification, enabling ≈ 100 times better sensitivity than that of previous bioelectronic noses based on only olfactory receptor protein and carbon nanotube transistors. The NBN sensors exhibited a human-like selectivity with single-carbon-atomic resolution and a high sensitivity of 1 fM detection limit. Moreover, this sensor platform could mimic a receptor-meditated cellular signal transmission in live cells. This sensor platform can be utilized for the study of molecular recognition and biological processes occurring at cell membranes and also for various practical applications such as food screening and medical diagnostics.

Large-scale assembly of highly flexible low-noise devices based on silicon nanowires.

Recently, integrated flexible devices based on silicon nanowires (Si-NWs) have received significant attention as high performance flexible devices. However, most previous assembly methods can generate only specifically-shaped devices and require unconventional facilities, which has been a major hurdle for industrial applications. Herein, we report a simple but very efficient method for assembling Si-NWs into virtually generally-shape patterns on flexible substrates using only conventional microfabrication facilities, allowing us to mass-produce highly flexible low-noise devices. As proof of this method, we demonstrated the fabrication of highly bendable top-gate transistors based on Si-NWs. These devices showed typical n-type semiconductor behaviors, and exhibited a much lower noise level compared to previous flexible devices based on organic conductors or other nanowires. In addition, the gating behaviors and low-noise characteristics of our devices were maintained, even under highly bent conditions.