Multi-Channel Signals in Dynamic Force-Clamp Mode of Microcantilever Sensors for Detecting Cellular Peripheral Brush.

The development of numerous diseases, such as renal cyst, cancer, and viral infection, is closely associated with the pathological changes and defects in the cellular peripheral brush. Therefore, it is necessary to develop a potential new method to detect lesions of cellular peripheral brush. Here, a piecewise linear viscoelastic constitutive model of cell is established considering the joint contribution of the peripheral brush and intra-cellular structure.

Temperature-dependent ejection evolution arising from active and passive effects in DNA viruses.

Recent experiments have demonstrated that the ejection velocity of different species of DNA viruses is temperature dependent, potentially influencing the cellular infection mechanisms of these viruses. However, due to the challenge in quantifying the multiscale characteristics of DNA virus systems, there is currently a lack of systematic theoretical research on the temperature-dependent evolution of ejection dynamics. This work presents a multiscale model to quantitatively explore the temperature-dependent mechanical properties during the virus ejection process, and unveil the underlying mechanisms.

Oxidized Starch-Reinforced Aqueous Polymer Isocyanate Cured with High-Frequency Heating.

In this research, an oxidized starch/styrene-butadiene rubber system with high capability of absorbing electromagnetic energy was adopted as the main component, the effect of oxidized starch content on the bonding and mechanical properties of aqueous polymer isocyanate (API) after high-frequency curing was evaluated, and the effect mechanisms were explored by combining thermodynamic tests and material characterization methods. Our findings revealed that the addition of oxidized starch enhanced the mechanical properties of API after high-frequency curing and the increase in the amount of oxidized starch enhanced the improvement effect of high-frequency curing on API bonding and mechanical properties. At 5 wt% oxidized starch, high-frequency curing improved API bonding properties by 18.

Mechanical Constraint Effect on DNA Persistence Length.

Persistence length is a significant criterion to characterize the semi-flexibility of DNA molecules. The mechanical constraints applied on DNA chains in new single-molecule experiments play a complex role in measuring DNA persistence length; however, there is a difficulty in quantitatively characterizing the mechanical constraint effects due to their complex interactions with electrostatic repulsions and thermal fluctuations. In this work, the classical buckling theory of Euler beam and Manning's statistical theories of electrostatic force and thermal fluctuation force are combined for an isolated DNA fragment to formulate a quantitative model, which interprets the relationship between DNA persistence length and critical buckling length.

Anomalous Elastic Properties of Attraction-Dominated DNA Self-Assembled 2D Films and the Resultant Dynamic Biodetection Signals of Microbeam Sensors.

The condensation of DNA helices has been regularly found in cell nucleus, bacterial nucleoids, and viral capsids, and during its relevant biodetections the attractive interactions between DNA helices could not be neglected. In this letter, we theoretically characterize the elastic properties of double-stranded DNA (dsDNA) self-assembled 2D films and their multiscale correlations with the dynamic detection signals of DNA-microbeams. The comparison of attraction- and repulsion-dominated DNA films shows that the competition between attractive and repulsive micro-interactions endows dsDNA films in multivalent salt solutions with anomalous elastic properties such as tensile surface stresses and negative moduli; the occurrence of the tensile surface stress for the attraction-dominated DNA self-assembled film reveals the possible physical mechanism of the condensation found in organism.

Theoretical Analysis for Bending of Single-Stranded DNA Adsorption on Microcantilever Sensors.

An energy-based model is presented to establish the bending deformation of microcantilever beams induced by single-stranded DNA (ssDNA) adsorption. The total free energy of the DNA-microcantilever sensor was obtained by considering the excluded-volume energy and the polymer stretching energy of DNA chains from mean-field theory, and the mechanical energy of three non-biological layers. The radius of curvature and deflection of the cantilever were determined through the minimum principle of energy.

Influence of Microscopic Interactions on the Flexible Mechanical Properties of Viral DNA.

During the packaging and ejection of viral DNA, its mechanical properties play an essential role in viral infection. Some of these mechanical properties originate from different microscopic interactions of the encapsulated DNA in the capsid. Based on an updated mesoscopic model of the interaction potential by Parsegian et al.

The pH-dependent elastic properties of nanoscale DNA films and the resultant bending signals for microcantilever biosensors.

The diverse mechanical properties of nanoscale DNA films on solid substrates have a close correlation with complex detection signals of micro-/nano-devices. This paper is devoted to formulating several multiscale models to study the effect of pH-dependent ionic inhomogeneity on the graded elastic properties of nanoscale DNA films and the resultant bending deflections of microcantilever biosensors. First, a modified inverse Debye length is introduced to improve the classical Poisson-Boltzmann equation for the electrical potential of DNA films to consider the inhomogeneous effect of hydrogen ions.

Effect of surface charge state on the surface stress of a microcantilever.

The surface charge state at a liquid-solid interface is important to the variations in the physical/chemical properties of adsorbate film such as surface stress and the ensuing tip deflection of the microcantilever. The well-known Stoney's equation, derived more than 100 years ago, conceals the film electrical properties with the replacement of substrate deformation induced by adsorptions of particles. This implicit expression provides a shortcut to circumvent the difficulty in identifying some film properties, however, it limits the capacity to ascertain the relation between surface stress variation and the surface charge state.

A multi-scale model for the analysis of the inhomogeneity of elastic properties of DNA biofilm on microcantilevers.

In nanoscale diagnostic systems, inhomogeneity in near-surface systems and flexibility in biostructures greatly influence the mechanical/electrical/thermal properties of biosensors and resultant detection signals. This study focuses on inhomogeneity and flexibility of DNA biofilm and characterizes its local interactions and mechanical properties. First, a flexible cylinder model of DNA chain is employed to capture the local geometric deformation characteristics of DNA molecules on microcantilever.

Mechanical properties of DNA biofilms adsorbed on microcantilevers in label-free biodetections.

Biomolecule adsorption is a fundamental process in the design of biosensors. Mechanical/electrical/thermal properties of biofilms have great influences on biodetection signals. The double-stranded DNA (dsDNA) biofilm adhered on microcantilever is treated as a bending beam with a macroscopic elastic modulus in the viewpoint of continuum mechanics.

Mechanical properties of double-stranded DNA biolayers immobilized on microcantilever under axial compression.

In label-free biodetections based on microcantilever technology, double-stranded DNA (dsDNA) structures form through the linkage between probe single-stranded DNA (ssDNA) molecules immobilized on solid substrates and target ssDNA molecules in solutions. Mechanical/electrical properties of these biolayers are important factors for nanomechanical deflections of microcantilevers. In this paper, the biolayer immobilized on microcantilever is treated as a bar with a macroscopic elastic modulus on the basis of continuum mechanics viewpoints.