The construction of the Space Station provides a spaceflight laboratory, which enables us to accomplish tremendous short- and long-duration research such as astronomy, physics, material sciences, and life sciences in a microgravity environment. Continuous innovation and development of spaceflight laboratory prompted us to develop a facile detection approach to meet stringent requirements in a microgravity environment that traditional experimental approaches cannot reach. Here we introduce superhydrophilic microwells onto superhydrophobic substrates that are capable of capturing and transferring microdroplets, demonstrating a proof-of-concept study of a biosensing platform toward microgravity application. The capability of manipulating microdroplets originates from the capillary force of the nanoscale dendritic coating in superhydrophilic microwells. Based on theoretical modeling, capillary forces of the superhydrophilic microwells can dominate the behavior of microdroplets against the gravity. Direct naked-eye observation monitoring of daily physiological markers, such as glucose, calcium, and protein can be achieved by colorimetric tests without the requirement of heavy optical or electrical equipment, which greatly reduced the weight, and will bring a promising clue for biodetection in microgravity environments.Keywords: biosensing; colorimetric biosensor; microgravity; superhydrophilic; superhydrophobic; superwettable microchips;

•Recent progress on ultrasound control and propel micro-/nanomotors is summarized.•Two typical devices for ultrasound microparticle manipulation are discussed.•Ultrasound induced interesting phenomenon is presented.•Use of ultrasound fields for biomedical applications is narrated.•Future challenges and opportunities of ultrasound micro-/nanomotors are concluded.Synthetic micro-/nanomachines, which are able to mimic the amazing natural system, can convert energy source into movement, and are expected to help humanity complete environmental and biological tasks. Ultrasound, with major advantages of on-demand motion control, long lifetime, noninvasive, contact free, and great biocompatibility, have been one of the most probable potential toward in vivo drug delivery and clinical diagnosis. In present short review, we intent to summarize the progress in using ultrasound to control and propel micro-/nanomachines during the last decade, and discussed the important aspects toward biomedical applications.Download high-res image (103KB)Download full-size image

A novel visible light responsive polymeric multilayer was constructed by layer-by-layer (LbL) electrostatic self-assembly, from which the trapping/release of cargoes via azobenzene/cyclodextrin-based host–guest interactions could be realized upon light stimulation. Visible light responsive poly{6-[(2,6-dimethoxyphenyl)azo-4-(2′,6′ dimethoxy)phenoxy]propyl dimethylaminoethyl methacrylate-random-poly(2-(N,N-dimethylaminoethyl) methacrylate)} (Azo-PDMAEMA) was synthesized, which was used as a polycation to combine with polyacrylic acid (PAA) for the construction of multilayers through the LbL electrostatic self-assembly technique. The cargo molecules, cyclodextrins modified with rhodamine B, could be loaded into the multilayers via the interaction between the trans azobenzene and cyclodextrin. Green light would induce isomerization of azobenzene from the trans-configuration to the cis, which disassembled the host–guest complex and resulted in the release of cargoes from the multilayers. Upon blue light irradiation, the cis azobenzene could recover to the trans form, thus a stable inclusion complex would be formed and the cargoes could be reloaded into the multilayers again. It is noted that the visible-light-controlled trapping/release of cargoes from the multilayers could be reconstructed reliably and conveniently. The electrostatically self-assembled multilayers of the prepared azobenzene-functionalized polymers combined with cyclodextrin show great potential in reversible trapping and release of cargoes controlled by visible light.

The measurement of sulfide, especially hydrogen sulfide, has held the attention of the analytical community due to its unique physiological and pathophysiological roles in biological systems. Electrochemical detection offers a rapid, highly sensitive, affordable, simple, and real-time technique to measure hydrogen sulfide concentration, which has been a well-documented and reliable method. This review details up-to-date research on the electrochemical detection of hydrogen sulfide (ion selective electrodes, polarographic hydrogen sulfide sensors, etc.) in biological samples for potential therapeutic use.

One-dimensional Pt nanostructures are of considerable interest for the development of highly stable and sensitive electrochemical sensors. This paper describes a self-interconnecting Pt nanowire network electrode (PtNNE) for the detection of hydrogen peroxide (H2O2) and glucose with ultrahigh sensitivity and stability. The as-prepared PtNNE consists of polycrystalline nanowires with high-index facets along the side surface which provides more active surface atoms on kinks and steps, those ultralong nanowires being interconnected with each other to form a free-standing network membrane. The excellent structural features of the PtNNE promoted its performance as a Pt-based electrochemical sensor both in terms of electrocatalytic activity and stability. Amperometric measurements towards hydrogen peroxide were performed; the PtNNE sensor showed an extremely high sensitivity of 1360 μA mM−1 cm−2. This excellent sensitivity is mainly attributed to the high-index facets of the nanowires resulting in their superior electrocatalytic activity towards H2O2, and the interconnected nanowire network forming an “electron freeway” transport model, which could provide multiple electron pathways and fast electron transport on the electrode, leading to rapid reaction and sensitive signal detection. The as-prepared PtNNE also holds promise as an oxidase-based biosensor. As a proof of concept, a PtNNE-based glucose biosensor also showed an outstanding sensitivity as high as 114 μA mM−1 cm−2, a low detection limit of 1.5 μM, and an impressive detection range from 5 μM to 30 mM.

The aggregation of Aβ peptides is a crucial factor leading to Alzheimer's disease (AD). Inhibiting the Aβ peptide aggregation has become one of the most essential strategies to treat AD. In this work, efficient and low-cytotoxicity inhibitors, graphene quantum dots (GQDs) are reported for their application in inhibiting the aggregation of Aβ peptides. Compared to other carbon materials, the low cytotoxicity and great biocompatibility of GQDs give an advantage to the clinical research for AD. In addition, the GQDs may cross the blood–brain barrier (BBB) because of the small size. It is believed that GQDs may be therapeutic agents against AD. This work provides a novel insight into the development of Alzheimer's drugs.

•We presented a novel electrochemical immunosensor for the detection of APOE4.•Synergetic effect of Fractal nanostructures and enzyme amplification enhanced the sensitivity of the sensor greatly.•It exhibited a wide linearity from 1 ng/mL to 10,000 ng/mL and a detection limit of 0.3 ng/mL.•The APOE4 protein was firstly detected by electrochemical immunosensor.Human apolipoprotein E4 (APOE4) is a major risk factor for Alzheimer's disease (AD) and can greatly increase the morbidity. In this work, an ultrasensitive sandwich-type electrochemical immunosensor for the quantitative detection of APOE4 was designed based on fractal gold (FracAu) nanostructures and enzyme amplification. The FracAu nanostructures were directly electrodeposited by hydrogen tetrachloroaurate (HAuCl4) on polyelectrolytes modified indium tin oxide (ITO) electrode. The sensing performances of the modified interface were investigated by cyclic voltammetry (CV). After functionalization with HRP-labeled APOE4 antibody, the human APOE4 could be detected quantitatively by current response. The current response has a linear relationship with the logarithm of human APOE4 concentrations in a range from 1.0 to 10,000.0 ng/mL, with a detection limit of 0.3 ng/mL. The fabricated APOE4 electrochemical immunosensor exhibits strong specificity, high sensitivity, low detection limit and wide linear range. The detection of human APOE4 provides a strong support for the prevention of AD and early-stage warning for those susceptible populations.

The assembling structure of square and triangular macrocycle molecules constructed with diethynylcarbazole units was investigated by scanning tunneling microscopy (STM) on a graphite surface. STM observation revealed that the square macrocycle molecule (M1) forms a multilayer on the graphite surface. In the first layer, M1 assembles into medium-sized domains with a few defects and dislocations, whereas, for the second layer, most of M1 are dispersed on the first layer separately. A tentative stacking mode of the bilayer structure is provided in this paper on the basis of information given by STM experiments. Considering the interlayer distance given by the crystal data on the similar molecules and the length of the M1 alkyl chains, we think that it is possible that part of the top M1 side chains adsorbs on the cavity area of the bottom M1 and probably plays a dominant role in stabilizing the second layer. This postulation is verified by a control experiment in which coronene is filled in the cavity of M1 and no bilayer structure of M1 is found. The triangular molecule (M2) organizes into a single layer with larger and less defect domains. Two M2 are paired together in parallel, but opposite-oriented style, and are responsible for the serrate edge of the molecular row. The alkyl chains of M2 adopt rather diverse arrangements without disturbing the assembly of M2 core parts. When the solution contains both coronene and M2, no M2–coronene complex is observed and the adlayer characteristics of M2 are essentially the same as those of only M2 in solution. The results may help us to learn the stacking behavior of macrocycle molecules with different shapes, understand surface self-assembling principles, and develop high-performance devices based on related materials.

We report a label-free and ultrasensitive aptasensor based on a fractal gold modified (FracAu) electrode for thrombin detection with a femtomolar detection limit. The FracAu electrode was prepared by electrodeposition of hydrogen tetrachloroaurate (HAuCl4) onto a bare indium tin oxide (ITO) electrode surface. After this process the electrode was characterized by SEM. A thiol-modified aptamer against thrombin was immobilized on the FracAu electrode through a self-assembling process. Upon thrombin binding, the interfacial electron transfer of the FracAu electrode was perturbed by the formation of an aptamer–thrombin complex. The concentration of thrombin in the sample solution was determined by measuring the change in the oxidation peak current of hydroxymethyl ferrocene (C11H12FeO) with differential pulse voltammetry (DPV). The current response (reduced peak current) had a linear relationship with the logarithm of thrombin concentrations in the range of 10−15 to 10−10 M with a detection limit of 5.7 fM. Furthermore, the as-prepared FracAu electrode exhibited high selectivity. The application of FracAu electrodes may be extended to prepare other types of biosensors, such as immunosensors, enzyme biosensors and DNA biosensors. These results show that FracAu electrodes have great promise for clinical diagnosis of disease-related biomarkers.

Proteins play important roles in human daily life. To take advantage of the lessons learned from nature, it is essential to investigate the self-assembly of subunits of proteins, i.e., amino acids and polypeptides. Due to its high resolution and versatility of working environment, scanning tunneling microscopy (STM) has become a powerful tool for studying interfacial molecular assembly structures. This review is intended to reflect the progress in studying interfacial self-assembly of amino acids and peptides by STM. In particular, we focus on environment-induced polymorphism, chiral recognition, and coadsorption behavior with molecular templates. These studies would be highly beneficial to research endeavors exploring the mechanism and nanoscale-controlling molecular assemblies of amino acids and polypeptides on surfaces, understanding the origin of life, unravelling the essence of disease at the molecular level and deeming what is necessary for the “bottom-up” nanofabrication of molecular devices and biosensors being constructed with useful properties and desired performance.