Ways for improving the sensing of nano-bio-sensors

The nano-bio-sensoristic sector is one of the mainstreams of nanotechnology and requires careful information for constant improvement of the nanodevice performance. The sensing/sensitivity plays a peculiar role, is a determinant characteristics, able to cause a great improvement of the device quality.The paper provides a detailed analysis on the casuistry for increasing the performanceof nano-systems through enhanced diffusion, studied with the use of a recent analytical transport model, able to accommodate previously not completely understood behaviours and to predict new interesting features at nanoscale.

Protein corona formation around biocatalytic nanomotors unveiled by STORM

The interaction of nanoparticles with biological media is a topic of general interest for drug delivery systems and among those for active nanoparticles, also called nanomotors. Herein, we report the use of super resolu-tion microscopy, in particular stochastic optical reconstruction microscopy (STORM), to characterize the formation of protein corona around active enzyme-powered nanomotors. First, we characterize the distribu-tion and number of enzymes on nano-sized particles and characterized their motion capabilities. Then, we incubated the nanomotors with fluorescently labelled serum proteins. Interestingly, we observed a signifi-cant decrease of protein corona formation (20 %) and different composition, which was studied by a proteo-mic analysis. Moreover, motion was not hindered, as nanomotors displayed an enhanced diffusion regardless of protein corona. Elucidating how active particles interact with biological media and maintain their self-propulsion after protein corona formation will pave the way of the use these systems in complex biological fluids in biomedicine.

Tuning the Reduction of Graphene Oxide Nanoflakes Differently Affects Neuronal Networks in the Zebrafish

The increasing engineering of biomedical devices and the design of drug-delivery platforms enriched by graphene-based components demand careful investigations of the impact of graphene-related materials (GRMs) on the nervous system. In addition, the enhanced diffusion of GRM-based products and technologies that might favor the dispersion in the environment of GRMs nanoparticles urgently requires the potential neurotoxicity of these compounds to be addressed. One of the challenges in providing definite evidence supporting the harmful or safe use of GRMs is addressing the variety of this family of materials, with GRMs differing for size and chemistry. Such a diversity impairs reaching a unique and predictive picture of the effects of GRMs on the nervous system. Here, by exploiting the thermal reduction of graphene oxide nanoflakes (GO) to generate materials with different oxygen/carbon ratios, we used a high-throughput analysis of early-stage zebrafish locomotor behavior to investigate if modifications of a specific GRM chemical property influenced how these nanomaterials affect vertebrate sensory-motor neurophysiology—exposing zebrafish to GO downregulated their swimming performance. Conversely, reduced GO (rGO) treatments boosted locomotor activity. We concluded that the tuning of single GRM chemical properties is sufficient to produce differential effects on nervous system physiology, likely interfering with different signaling pathways.

Guided accumulation of active particles by topological design of a second-order skin effect

Collective guidance of out-of-equilibrium systems without using external fields is a challenge of paramount importance in active matter, ranging from bacterial colonies to swarms of self-propelled particles. Designing strategies to guide active matter and exploiting enhanced diffusion associated to its motion will provide insights for application from sensing, drug delivery to water remediation. However, achieving directed motion without breaking detailed balance, for example by asymmetric topographical patterning, is challenging. Here we engineer a two-dimensional periodic topographical design with detailed balance in its unit cell where we observe spontaneous particle edge guidance and corner accumulation of self-propelled particles. This emergent behaviour is guaranteed by a second-order non-Hermitian skin effect, a topologically robust non-equilibrium phenomenon, that we use to dynamically break detailed balance. Our stochastic circuit model predicts, without fitting parameters, how guidance and accumulation can be controlled and enhanced by design: a device guides particles more efficiently if the topological invariant characterizing it is non-zero. Our work establishes a fruitful bridge between active and topological matter, and our design principles offer a blueprint to design devices that display spontaneous, robust and predictable guided motion and accumulation, guaranteed by out-of-equilibrium topology.

Structure-induced features of transport processes in an electroconsolidated FeNi composite

The structure and processes of mass, charge and heat transfer are investigated in an equiatomic Fe–Ni composite fabricated by electroconsolidation using the spark plasma sintering (SPS) technology. The system contains regions of almost pure Fe and Ni, separated by areas with variable concentration of components, formed in consequence of the interdiffusion in the electroconsolidation process. The interdiffusion coefficient of the Fe–Ni system has been revealed to be significantly higher than that of an alloy of a similar composition at the same temperature, which is likely the result of the employed SPS technology and the enhanced diffusion along the grain boundaries. The concentration dependence of the interdiffusion coefficient passes through a maximum at a Ni concentration of [Formula: see text] at.%. The electrical and thermal conductivity of the studied system is significantly higher than that of an alloy of the same composition. The temperature dependence of the resistivity of the sample in the range 5–300 K is due to the scattering of electrons by defects and phonons, and the scattering of electrons by phonons fits well to the Bloch–Grüneisen–Wilson relation. The boundaries of the conductivity of the investigated composite correspond to the Hashin–Shtrikman boundaries for a three-phase system, if Fe, Ni and the FeNi alloy are selected as phases.

Displacement statistics of unhindered single molecules show no enhanced diffusion in enzymatic reactions

Recent studies have sparked heated debate over whether catalytical reactions would enhance the diffusion coefficients D of enzymes. Through high statistics of the transient (600 μs) displacements of unhindered single molecules freely diffusing in common buffers, we here quantify D for four highly contested enzymes under catalytic turnovers. We thus formulate how precisions of better than ±1% may be achieved for D at the 95% confidence level, and show no changes in diffusivity for catalase, urease, aldolase, and alkaline phosphatase under the application of wide concentration ranges of substrates. Our single-molecule approach thus overcomes potential limitations and artifacts underscored by recent studies to show no enhanced diffusion in enzymatic reactions.

Direction-dependent turning leads to anisotropic diffusion and persistence

Cells and organisms follow aligned structures in their environment, a process that can generate persistent migration paths. Kinetic transport equations are a popular modelling tool for describing biological movements at the mesoscopic level, yet their formulations usually assume a constant turning rate. Here we relax this simplification, extending to include a turning rate that varies according to the anisotropy of a heterogeneous environment. We extend known methods of parabolic and hyperbolic scaling and apply the results to cell movement on micropatterned domains. We show that inclusion of orientation dependence in the turning rate can lead to persistence of motion in an otherwise fully symmetric environment and generate enhanced diffusion in structured domains.