Dragnea, B. | Search bioRxiv

bioRxiv2025

Nanotribology of Viruses Reveals Their Adhesion Strength and Modality of Motion on Surfaces

We studied the friction dynamics of icosahedral viruses adsorbed to solid surfaces to probe their adhesion. Using the lateral torsion of cantilevers in atomic force microscopy to move individual capsids in a liquid environment, we found that the virions tend to roll rather than slide on the surface. In contrast, rigid, ligand-stabilized gold nanoparticles are more likely to combine rolling with sliding under the same conditions. The experiments indicate that the force required to drag the viruses on the surface is four times less than that of AuNPs, while the lateral force work needed to induce virus movement was [~] 104 kT, ten times less than that of the rigid gold nanoparticles. These results go beyond the paradigm that adhesion of nanoparticles is mainly governed by geometrical factors, such as size and area of contact, highlighting the need to amend modeling approaches to account for mechanically-compliant tribological response of biologically derived nanoparticles.

biophysics↗

bioRxiv2017

Layered structure and complex mechanochemistry of a strong bacterial adhesive

While designing adhesives that perform in aqueous environments has proven challenging for synthetic adhesives, microorganisms commonly produce bioadhesives that efficiently attach to a variety of substrates, including wet surfaces that remain a challenge for industrial adhesives. The aquatic bacterium Caulobacter crescentus uses a discrete polar polysaccharide complex, the holdfast, to strongly attach to surfaces and resist flow. The holdfast is extremely versatile and has an impressive adhesive strength. Here, we use atomic force microscopy (AFM) to unravel the complex structure of the holdfast and characterize its chemical constituents and their role in adhesion. We used purified holdfasts to dissect the intrinsic properties of this component as a biomaterial, without the effect of the bacterial cell body. Our data support a model where the holdfast is a heterogeneous material composed of two layers: a stiff nanoscopic core, covered by a sparse, flexible brush layer. These two layers contain not only N-acetyl-D-glucosamine (NAG), the only yet identified component present in the holdfast, but also peptides and DNA, which provide structure and adhesive character. Biochemical experiments suggest that, while polypeptides are the most important components for adhesive force, the presence of DNA mainly impacts the brush layer and initial adhesion, and NAG plays a primarily structural role within the core. Moreover, our results suggest that holdfast matures structurally, becoming more homogeneous over time. The unanticipated complexity of both the structure and composition of the holdfast likely underlies its distinctive strength as a wet adhesive and could inform the development of a versatile new family of adhesives.

biophysics↗