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Special Issue on Biomaterials and Health-care related Materials
The demand for biomaterials and health-care related materials in various medical applications has been increasing significantly across the globe over the last decade, and has been even more acute these days. This special issue of NPG Asia Materials, “Biomaterials and health-care related materials” is aimed at providing the recent advances in fundamental research on biomaterials, biointeractions, health-care and wearable health-monitoring materials, as well as the forefront of their medical applications. The issue covers original research and comprehensive review articles on topics ranging from biochemistry, biomaterials and biointerfaces to functional bio-devices for advanced research and healthcare systems.
DNA double helix exploiting Watson–Crick base-pairing lays the foundation of DNA nanotechnology. However, other forms of nucleic acids (e.g., triplex, i-motif, and G-quadruplex) exhibiting noncanonical base-base interactions bring about novel functionality. Here, we review the interplay of naturally occurring noncanonical nucleic acids and artificial DNA nanostructures in biomedical applications that have not been possible by duplex formation alone.
Wearable electronic devices are under development which can monitor health by analyzing bodily fluids such as sweat. Electronic components placed inside the body or on the skin that constantly monitor our bodies could become a key part of future healthcare strategies. Chi Hwan Lee and coworkers from Purdue University, West Lafayette, USA, have reviewed recent advances in a variety of wearable devices that can be worn to electrochemically analyze bodily fluids. They discuss the materials required for these components, which need to be mechanically soft and deformable to conform to the body as it moves, the mechanisms used for sensing and the different wireless connection configurations. The devices can test sweat, tears and the interstitial fluid that surrounds cells for monitoring diseases such as diabetes, gout, and Parkinson’s disease.
The development of low-cost, efficient, and large-scale methods for fabricating ‘soft’ electronics, conducting materials with improved flexibility and stretchability, increases the range of possible applications. Flexible electronics are useful for foldable displays, healthcare monitoring, artificial skins and implantable bioelectronics. One approach to fabricating these devices is to construct them from conductive nanofibers. Takao Someya from the University of Tokyo and colleagues review recent advances in constructing nanofiber-based soft electronics using a technique called electrospinning. Electrospinning works by drawing a molten material through a nozzle into an electric field to produce strands much finer than a human hair. The authors review the structure and properties of electrospun nanofiber materials and the various strategies for assembling flexible and stretchable electronic devices such as sensors, transistors, and components for energy harvesting and storage.
Scientists in Japan have reviewed how nanoscience is helping us understand infection with SARS-CoV-2, the virus responsible for Covid-19, and the immune response it produces. The coronavirus pandemic has driven international scientific collaboration to identify treatments and develop a vaccine, not only between virologists and immunologists but also with researchers from a broad range of other disciplines including chemists, physicists and materials scientists. Vasudevanpillai Biju from Hokkaido University, Sapporo, and colleagues have reviewed the ongoing research at the interface of infectious diseases, biological chemistry and nanoscience aimed at answering key questions on how the virus functions. The authors summarize the use of nanomaterials in imaging techniques, vaccine development and drug delivery, while investigating problems associated with the toxicity of nanomaterials. Understanding these molecular interactions will help to fight this and future pandemics.
The various sheets, tubes, and dot-like nanostructures formed by carbon atoms can make a molecular sensing technology safer and more effective. In surface-enhanced Raman spectroscopy (SERS), detection of single molecules is achieved by attaching biological targets to signal-boosting substrates, typically metal nanoparticles. Biao Kong from Fudan University in Shanghai, China, and colleagues review how metal SERS substrates are being replaced by carbon-based nanostructures engineered to produce localized ‘hotspots’ where electric fields are enhanced. These substrates offer improved biocompatibility and customizable device structures. For example, graphene can easily host tumor cells for cancer sensing, while carbon dots can attach to DNA strands to act as ultra-small barcodes. The favorable mechanical properties of carbon also enable production of innovative materials including drug-sensing nanosheets that adhere to the surfaces of banknotes and coins.
Schematic illustration showing our overall approach, studies performed, and envisioned application. Our strategy combines biomechanical and biochemical cues from a mechanically graded biomaterial and GF biopatterning, respectively, to spatially control bone- and tendon-like differentiation. Here, experiments (i) characterized our biomaterial, (ii) investigated the interplay between biomechanical and biochemical cues in vitro, and (iii) assessed the ability of our GF-biopatterned and biphasic biomaterial to spatially control bone- and tendon-like tissue formation in vivo. The envisioned goal of this study is to develop a biomaterial for treating large-to-massive tendon injuries.
A new material that can selectively bind to multiple types of toxins while leaving other protein biomolecules and blood cells untouched has undergone successful animal trials. Baoyang Hu, Shu Wang, and colleagues from the Chinese Academy of Sciences in Beijing report that aromatic polymers containing amine-based rings active esters and carboxylic acid groups recognize and attach to proteins carrying high densities of surface positive charges. Gel electrophoresis and measurements of enzyme activity demonstrated that this polymer binding could also deactivate the functions of the positively charged proteins found in many snake venoms. Polymer treatments of mice injected with cardiotoxins improved survival rates significantly compared to control groups. In addition, the polymer’s naturally bright fluorescent emissions enabled the team to examine its distribution into internal organs using bioimaging techniques.
A conductive material created by combining metals with Teflon-like polymers can improve the stability of touch panels and wearable sensors. Han-Ki Kim and colleagues from Sungkyunkwan University in Suwon, South Korea, report that magneton sputtering, a technique that bombards surfaces with energetic ions, can be used to produce thin polytetrafluoroethylene films infused with narrow channels of silver atoms. Investigations revealed that this material remained highly conductive even after being stretched repeatedly, avoiding the fracturing problems commonly seen when metals are deposited on top of plastic substrates. The team used the new composite as flexible electrodes in a variety of applications including wrist sensors that detect a range of human motion, and forearm-attached electromyography sensors. The silver-filled polymer also had natural water-repelling properties that could be used to make devices with self-cleaning surfaces.
Nanoparticles made from an organic dye that can help kill cancer cells have been developed by scientists in India and Australia. Photothermal therapy uses light to heat nanoparticles that are injected into the body and accumulate in cancer cells. The resulting increase in temperature kills the cells. The choice of nanoparticle material is vital. Existing inorganic nanomaterials are non-biodegradable and potentially toxic, while materials based on bio-compatible polymers are complicated to fabricate. Kandala Laxman from the Indian Institute of Technology Bombay and co-workers have developed an organic dye suitable for photothermal therapy. The team engineered the molecular structure of the dye so that, unlike many dyes, it strongly absorbs light at wavelengths that pass through human tissue. They showed that the material is efficient at converting light to heat and is stable at physiological pH.
A silver nanomaterial that can destroy drug-resistant bacteria has been developed by researchers in China. The rise of antibiotic-resistant bacteria is a major source of concern in global health. Silver has long been known to have antibacterial properties, and so scientists are returning to it as a possible agent to combat these multidrug-resistant bacteria. While silver nanoparticles have previously been shown to have good antibacterial activity, a team led by Nanfeng Zheng, Xiamen University, and Sijin Liu, Chinese Academy of Sciences, Beijing, have shown that small clusters of silver particles are even better. The researchers determined the optimal size, structure and surface properties of antibacterial nanosilver clusters. They used their nanoclusters to treat pneumonia in mice caused by the multidrug-resistant bacteria Pseudomonas aeruginosa, increasing their survival rates.
Improvements to a recently developed technique for printing biomaterials could make it easier to fabricate complex scaffolds for tissue regrowth. By shaping biocompatible polymers into thin microfibers and then collecting the strands on a moving platform, researchers can build tissue scaffolds layer-by-layer into 3D structures. Yingchun Su from the Harbin Institute of Technology in Harbin, China, and Aarhus University, Denmark, and colleagues report that materials printed by this ‘speed-programmed melt electrospinning writing’ technique can be composed of coil-shaped microfibers. The team found that the coil-like strands, produced by manipulating platform collection speeds, were effective at introducing pores into 3D scaffolds to better mimic natural tissue. Experiments showed this approach enabled better control over the cell density and growth behavior of stem cells implanted in a scaffold shaped like an artificial lumbar vertebra.