The term bio-interface describes the boundary between synthetic materials such as plastics, and biological systems. This rapidly growing research area, where biology and material sciences overlap, is creating new opportunities for the design, synthesis, and optimization of biologically-enabled and biologically-inspired materials. It involves manufacturing and characterization of functional surfaces for specific interactions with bio-systems and studies of the molecular and kinetic processes occurring at such interfaces, ranging from small molecule and biomolecular interactions, to cell adhesion, differentiation and tissue formation at the interface. For example, the incorporation of proteins into polymers can result in hybrid materials that combine the properties of the polymer as a cost-effective and easy to process material with the highly evolved biological functionality of the protein, enabling new concepts for construction of sensors and biomedical materials. While researchers so far have been focusing on altering the properties of a polymer by adding the functionality of a biomolecule, a group in California has now demonstrated the reverse situation, where changes in the polymer can alter the properties of the protein.
Developing bioassays that are simple, portable, disposable and inexpensive will provide important tools to rapidly detect toxic substances. This technology could also be extremely useful in monitoring environmental and food-based toxins in remote settings such as less industrialized countries where these tools are essential for the first stages of detecting disease settings and where the time and expense of using sophisticated instrumentation would be prohibitive. To that end, researchers have developed simple, portable, disposable, and inexpensive paper-based solid-phase sensors to run multiple bioassays and controls simultaneously. Bioactive paper is any low-cost and easy-to-use paper product laced with biologically active chemicals that provides a rapid way to detect toxins like E. coli bacteria and salmonella, or pathogens such as SARS or influenza.
Controlling surface plasmons has become increasingly attractive for optical signal processing, surface enhanced spectroscopy and sensor nanotechnology. For instance, the role of surface plasmon resonance (SPR) on resonant transmission through nanohole arrays has motivated their application as surface-based biosensors. New work by a team of scientists in Canada has combined nanofluidics and nanoplasmonics for SPR sensing using flow-through nanohole arrays. This new format enables rapid transport of reactants to the active sensing surface and the array serves as a sieve. That is, the flow-through array efficiently collects and detects biomarkers from a very small volume of fluid.
Environmental and behavioral factors may lead the body to produce superoxide radicals known as reactive oxygen species (ROS) that could cause cell damage through oxidation. Oxidative stress from ROS is implicated in aging and most diseases including cancer, heart disease, liver fibrosis, neurodegenerative diseases, autoimmune disorders. An excess of these reactive molecules can lead to oxidative stress and cellular damage, and toxicologists have identified ROS generation as a likely mechanism of nanoparticle toxicity. Since ROS plays an important role in various pathogenic processes, it has been recognized as an early indicator for cytotoxic events and cellular disorders. However, conventional chemical ROS probes have not fulfilled the rising need of in vitro and in vivo analysis of ROS generation due to auto-oxidation problems and poor specificity and sensitivity. Scientists in South Korea have now demonstrated a novel ROS-sensitive gold nanoprobe prepared from bio-inspired immobilization of fluorescein-labeled hyaluronic acid onto the surface of gold nanoparticles. This probe is highly stable under exposure to natural light and laser sources and extremely sensitive and specific to certain oxygen species.
Gas sensing applications are numerous in our modern society and include process monitoring, environmental compliance, health applications, homeland security, agriculture, etc. Gas sensors often operate by detecting the subtle changes that deposited gas molecules make in the way electricity moves through a surface layer. Thus, the more surface available, the more sensitive the sensor will be. Nanoscale materials are intriguing materials for next-generation nanotechnology gas sensors since their relative surface areas are so large. A problem with existing gas nanosensors is the cross-interference of other gas analytes. For instance, carbon nanotube based gas sensors for the prominent air pollutant nitrogen dioxide have shown strong interference of ethanol and ammonia gases to the NO2 response. Another cross-interference often is caused by humidity, i.e. the water vapor in the air. New research now demonstrates how the manufacturing of a nanosensor for ammonia gas can be tuned to eliminate the interference of water vapor. The trick lies in accurately controlling the synthesis of the sensing nanomaterial.
Infrared (IR) detectors are used in imaging applications that include for instance medical diagnosis, environmental monitoring, space science, and security and military sensor devices. High-quality detectors require cryogenic cooling in order for the image not to be distorted by the detectors own radiation. This makes them expensive both to produce and to run. Although uncooled IR detectors are made, their resolution and image quality tend to be much lower than cooled detectors. It appears that carbon nanotubes (CNTs) could be used as novel IR detector material that would allow the fabrication of highly efficient detectors that do not require cooling. Researchers at Michigan State University have now, for the first time, experimentally demonstrated the design, manufacturing and experimental testing of an integrated nanoantenna concept for CNT based IR sensors.
Over the past few years, scientists have taken advantage of the unique optical and other physical properties of metal nanoparticles to create a wide range of nanotechnology probes for electronic, optical, and microgravimetric transduction of different biomolecular recognition events. An interesting approach that was reported a couple of years ago deals with a technique that estimates the antioxidant power of certain food samples by measuring the generation and growth of gold nanoparticles. Researchers have built on these findings by developing a novel optical nanoprobe that can analyze the total reducing sugar content of samples. This technique could lead to the development of inexpensive and disposable optical nanoprobes that could find applications in a host of industrial, biomedical and clinical fields.
In physics, a plasmon is the quasi-particle resulting from the quantization of plasma oscillations just as photons and phonons are quantizations of light and sound waves, respectively. As the name indicates, surface plasmons are those plasmons that are confined to surfaces. The control of these surface plasmons has become increasingly attractive for optical signal processing, surface enhanced spectroscopy and sensor nanotechnology. The plasmonic properties of nanoparticles depend on various parameters such as their size or shape, and the refractive index of the environment. Surface plasmons form the basis of localized surface plasmon resonance (LSPR) sensing, which allows the detection of single molecules. Researchers have now demonstrated for the first time that the absorption and emission properties of few-atom metal nanoclusters respond dramatically to changes in the chemical environment.