Monitoring the hydration of DNA self-assembled monolayers using an extensional nanomechanical resonator

Detection of Trace Amounts of Water in Organic Solvents by DNA-Based Nanomechanical Sensors

The detection of trace amounts of water in organic solvents is of great importance in the field of chemistry and in the industry. Karl Fischer titration is known as a classic method and is widely used for detecting trace amounts of water; however, it has some limitations in terms of rapid and direct detection because of its time-consuming sample preparation and specific equipment requirements. Here, we found that a DNA-based nanomechanical sensor exhibits high sensitivity and selectivity to water vapor, leading to the detection and quantification of trace amounts of water in organic solvents as low as 12 ppm in THF, with a ppb level of LoD through their vapors. Since the present method is simple and rapid, it can be an alternative technique to the conventional Karl Fischer titration.

Application of nanotechnology in biosensors for enhancing pathogen detection

Rapid detection and identification of pathogenic microorganisms is fundamental to minimizing the spread of infectious disease, and informing clinicians on patient treatment strategies. This need has led to the development of enhanced biosensors that utilize state of the art nanomaterials and nanotechnology, and represent the next generation of diagnostics. A primer on nanoscale biorecognition elements such as, nucleic acids, antibodies, and their synthetic analogs (molecular imprinted polymers), will be presented first. Next the application of various nanotechnologies for biosensor transduction will be discussed, along with the inherent nanoscale phenomenon that leads to their improved performance and capabilities in biosensor systems. A future outlook on characterization and quality assurance, nanotoxicity, and nanomaterial integration into lab-on-a-chip systems will provide the closing thoughts. This article is categorized under: Diagnostic Tools > Diagnostic Nanodevices Diagnostic Tools > Biosensing.

Hybrid spin-microcantilever sensor for environmental, chemical, and biological detection

Nowadays hybrid spin-micro/nanomechanical systems are being actively explored for potential quantum sensing applications. In combination with the pump-probe technique or the spin resonance spectrum, we theoretically propose a realistic, feasible, and an exact way to measure the cantilever frequency in a hybrid spin-micromechanical cantilever system which has a strong coherent coupling of a single nitrogen vacancy center in the single-crystal diamond cantilever with the microcantilever. The probe absorption spectrum which exhibits new features such as mechanically induced three-photon resonance and ac Stark effect is obtained. Simultaneously, we further develop this hybrid spin-micromechanical system to be an ultrasensitive mass sensor, which can be operated at 300 K with a mass responsivity 0.137 Hz ag(-1), for accurate sensing of gaseous or aqueous environments, chemical vapors, and biomolecules. And the best performance on the minimum detectable mass can be [Formula: see text] in vacuum. Finally, we illustrate an in situ measurement to detect Angiopoietin-1, a marker of tumor angiogenesis, accurately with this hybrid microcantilever at room temperature.

Hydration induced stress on DNA monolayers grafted on microcantilevers

Surface tethered single-stranded DNA films are relevant biorecognition layers for oligonucleotide sequence identification. Also, hydration induced effects on these films have proven useful for the nanomechanical detection of DNA hybridization. Here, we apply nanomechanical sensors and atomic force microscopy to characterize in air and upon varying relative humidity conditions the swelling and deswelling of grafted single stranded and double stranded DNA films. The combination of these techniques validates a two-step hybridization process, where complementary strands first bind to the surface tethered single stranded DNA probes and then slowly proceed to a fully zipped configuration. Our results also demonstrate that, despite the slow hybridization kinetics observed for grafted DNA onto microcantilever surfaces, ex situ sequence identification does not require hybridization times typically longer than 1 h, while quantification is a major challenge.

Atomic force microscopy reveals two phases in single stranded DNA self-assembled monolayers

We have investigated the structure of single-stranded (ss) DNA self-assembled monolayers (SAMs) on gold by combining peak force tapping, Kelvin probe and phase contrast atomic force microscopy (AFM) techniques. The adhesion, surface potential and phase shift signals show heterogeneities in the DNA film structure at two levels: microscale and nanoscale; which cannot be clearly discerned in the topography. Firstly, there is multilayer aggregation covering less than 5% of the surface. The DNA multilayers seem to be ordered phases and their existence suggests that DNA end-to-end interaction can play a role in the self-assembly process. Secondly, we find the formation of two phases in the DNA monolayer, which differ both in surface energy and surface potential. We relate the two domains to differences in the packing density and in the ssDNA conformation. The discovered heterogeneities in ssDNA SAMs provide a new scenario in our vision of these relevant films that have direct consequences on their biological, chemical and physical properties.