No matter how precise nanosensors and -probes become, bridging the huge gap between nanoscale dimensions and macroscale structures (e.g., wafer size) has been a tremendous challenge for researchers. Researchers in the U.S. have demonstrated a generalized hybrid nanofabrication concept that combines both top-down (deep-UV lithography) and bottom-up (controlled lateral epitaxial growth and atomic layer deposition) fabrication techniques. This unique methodology allows the development of reproducible nanostructured platforms that contain controlled sub-10 nm gaps between plasmonic nanostructures over an entire wafer, i.e. a 6-12 inch area. This approach opens new horizons to more widespread applications in chemical sensing and biomedical diagnostics.
Research to develop sensors that can rapidly detect biomarkers (associated with certain diseases such as cancer) in whole blood, ideally at the point of care, and when the protein biomarker level in blood is very low (i.e. the disease is in an early stage) is being advanced by nanosensor technology. In a recent development, scientists in Spain have developed a rapid nanochannel-based immunoassay capable of the filtering and subsequent detection of proteins in whole blood without any sample preparation. This is the first time that a simple assay to detect proteins in whole blood using nanochannels has been achieved. This is a simple device and set-up that allows nanochannels to achieve such the double functionality of filtering and detection on the same platform.
A multi-disciplinary research team has introduced a novel label-free optofluidic-nanoplasmonic biosensor and demonstrated direct detection of live viruses from biological media at medically relevant concentrations with little to no sample preparation. This novel platform can be easily adapted for point-of-care diagnostics to detect a broad range of viral pathogens in resource-limited clinical settings at the far corners of the world, in defense and homeland security applications as well as in civilian settings such as airports or other public spaces. This work is the first demonstration of detection of intact viruses using extraordinary light transmission phenomena in plasmonic nanohole arrays.
In order to improve throughput speed of DNA sequencing and reduce its cost, researchers are pursuing real-time solid-state DNA sequencing devices. To that end, electronic functional devices in liquid environments need to be developed, ideally utilizing the compatibility with current complementary metal oxide semiconductor (CMOS) based fabrication technology. In this regard, the combination of electronics and nanofluidics leads to the field of electrofluidics, which utilizes the electrical behaviors of fluids for solid state device applications. In order to explore the ion transport and biomolecule transport through nanochannels, researchers have now reported the fabrication of an electrofluidic platform to study the motion of single molecules, including DNA. The device's nanochannel structures were fabricated with sub-lithographic dimension through top-down based, conventional semiconductor fabrication methods.
One of the tools developed by molecular biologists to study cell membranes and their associated proteins is a synthetic membrane model called Nanodisc. This is a self-assembled phospholipid bilayer disc of about 10 nm diameter, wrapped in a membrane scaffold protein belt. Nanodiscs render amphipathic and hydrophobic molecules easily soluble, offering transformative innovations across a broad range of applications in both in vivo delivery of therapeutics, diagnostic and imaging agents as well as for in vitro drug discovery. They have become important tools in analyzing membrane proteins, which are the most important target for present-day drug discovery programs. Further developing the nanodisc toolbox, researchers have now demonstrated the efficacy of Nanodiscs receptors for the nanomechanical detection of cholera.
Semiconducting nanowires are known to be extremely sensitive to chemical species adsorbed on their surfaces. For a nanowire device, the binding of a charged analyte to the surface of the nanowire leads to a conductance change, or a change in current flowing through these tinny wires. Their one-dimensional nanoscale morphology and their extremely high surface-to-volume ratio make this conductance change to be much greater for nanowire-based sensors versus planar field-effect transistors, increasing the sensitivity to a point that single molecule detection is possible. In the last decade, it has been demonstrated that these new nanostructures can be used for the detection of multiple biomolecular species of medical diagnostic relevance, such as DNA and proteins. In recent work, researchers have used the ultrasensitive recognition properties of semiconducting silicon nanowires to demonstrate the most sensitive ever published sensing of explosives reported so far.
Unlike most biological membranes, polymeric, nanometer-thin membranes are very stable and can withstand considerable pressure. This is an essential requirements for separation processes such as in water purification and desalination. Because their mechanical stability can be combined with flexibility and chemical functionality, polymer nanomembranes are also intensely researchers as materials for actuators and microsensors. They have also entered the biomedical field as artificial nacre and as a novel material used in surgery. Crosslinking of a spin-coated precursor solution, a common fabrication technique, reduces the interactions between the polymer chains and the environment and thus impairs the sensitivity and flexibility of the films. Researchers in Germany have now developed the first freestanding polymer brush, grafted from a crosslinked monolayer (nanosheet) that provides mechanical stability and structural integrity.
Imagine a device the size of - and nearly as cheap as - a grain of sand which is capable of analyzing the environment around it, recognize its chemical composition, and report it to a monitoring system. This is the concept of nanotechnology-based electronic noses (e-nose) - miniature electronic devices which mimic the olfactory systems of mammals and insects and which will lead to better, cheaper and smaller sensor devices. An international team of researchers has made a further step towards this vision and demonstrated a novel analytical sensor which mimics our olfaction system. The difference between this and similar prior e-noses is that the active element of this new device is an individual wedge-like nanowire (nanobelt) made of tin dioxide. The required diversity of the sensing elements is encoded in the nanobelt morphology via longitudinal width variations of the nanobelt realized during its growth and via functionalization of some of the segments with palladium catalyst.