Nanobiotechnology: checking out the insides of cells

Nanoparticle-Based and Bioengineered Probes and Sensors to Detect Physiological and Pathological Biomarkers in Neural Cells

Nanotechnology, a rapidly evolving field, provides simple and practical tools to investigate the nervous system in health and disease. Among these tools are nanoparticle-based probes and sensors that detect biochemical and physiological properties of neurons and glia, and generate signals proportionate to physical, chemical, and/or electrical changes in these cells. In this context, quantum dots (QDs), carbon-based structures (C-dots, grapheme, and nanodiamonds) and gold nanoparticles are the most commonly used nanostructures. They can detect and measure enzymatic activities of proteases (metalloproteinases, caspases), ions, metabolites, and other biomolecules under physiological or pathological conditions in neural cells. Here, we provide some examples of nanoparticle-based and genetically engineered probes and sensors that are used to reveal changes in protease activities and calcium ion concentrations. Although significant progress in developing these tools has been made for probing neural cells, several challenges remain. We review many common hurdles in sensor development, while highlighting certain advances. In the end, we propose some future directions and ideas for developing practical tools for neural cell investigations, based on the maxim "Measure what is measurable, and make measurable what is not so" (Galileo Galilei).

Silicon nanowire-based surface-enhanced raman spectroscopy endoscope for intracellular pH detection

Very recently, one-dimensional nanowire (NW) sensors have attracted great attention as smart optical endoscopes to probe and manipulate intracellular biological processes. However, NWs often have limited optical response to the intracellular environment changes. In this work, a near-infrared nanowire optical endoscope for high-resolution intracellular pH detection was developed by integrating the advantages of silicon nanowires and surface-enhanced Raman spectroscopy (SERS). This optical endoscope has a high-resolution, sensitive response to local pH changes over the wide range of pH 4.0-9.0, an important range for most biological processes in cells, with high reproducibility, good reversibility, and at least one-week stability in an aqueous environment. The results indicate the great potential of a single SiNW SERS endoscope for intracellular pH monitoring.