Biology subjects

Evans, N. D.

Publications and source records attributed to Evans, N. D..

4 recordsLinked to original sources

bioRxiv2026

The material properties of the cell determine microbubble-induced cell deformation and permeabilisation

Mechanical properties influence how cells withstand and transmit force, but their role in clinically relevant, high-frequency therapeutic perturbations remains poorly understood. Ultrasound-stimulated microbubbles can locally deform cells and tissues to enhance drug delivery, yet therapeutic responses vary markedly across mechanical microenvironments. How cellular material properties govern microbubble-cell interactions at megahertz loading rates - well beyond the range accessible to conventional mechanobiology - remains unresolved. Here we combine ultra-high-speed imaging with digital image correlation to map microbubble-induced deformation in living cells at ultrasound frequencies. We show that oscillating microbubbles generate harmonic deformation waves whose spatial decay defines a micrometre-scale attenuation length governed by cytoskeletal organisation and intracellular viscoelastic dissipation. Pharmacological softening or stiffening alters both deformation propagation and wave speed, and these mechanical changes predict permeabilisation efficiency in tumour-derived and primary human bone-marrow stromal cells. These findings establish cellular viscoelasticity as a determinant of microbubble bioeffects and suggest that tissue mechanical state can be used as a design parameter for ultrasound-mediated therapeutic delivery.

bioengineering↗

bioRxiv2023

Geometric constraint of mechanosensing in bone marrow stromal cell cultures prevents stiffness-induced differentiation

Extracellular matrix (ECM) stiffness is fundamental in cell division, movement and differentiation. The stiffness that cells sense is determined not only by the elastic modulus of the ECM material, but also by ECM geometry and cell density. We hypothesised that these factors would influence cell-traction-induced matrix deformations and cellular differentiation in bone marrow stromal cells (BMSCs). To achieve this, we cultivated BMSCs on polyacrylamide hydrogels that varied in elastic modulus and geometry and measured cell spreading, cell-imparted matrix-deformations and differentiation. At low cell density BMSCs spread to a greater extent on stiff compared to soft hydrogels, or on thin compared to thick hydrogels. Cell-imparted matrix deformations were greater on soft compared to stiff hydrogels or thick compared to thin hydrogels. There were no significant differences in osteogenic differentiation relative to hydrogel elastic modulus and thickness. However, increased cell density and/or prolonged culture significantly reduced matrix deformations on soft hydrogels to levels similar to those on stiff substrates. This suggests that at high cell densities cell traction-induced matrix displacements are reduced by both neighbouring cells and the constraint imposed by an underlying stiff support. This may explain observations of the lack of difference in osteogenic differentiation as a function of stiffness.

biophysics↗

bioRxiv2022

Chemoproteomics yields a selective molecular host for acetyl-CoA

Chemoproteomic profiling is a powerful approach to define the selectivity of small molecules and endogenous metabolites with the human proteome. In addition to mechanistic studies, proteome specificity profiling also has the potential to identify new scaffolds for biomolecular sensing. Here we report a chemoproteomics-inspired strategy for selective sensing of acetyl-CoA. First, we use chemoproteomic capture experiments to validate the N-terminal acetyltransferase NAA50 as a protein capable of differentiating acetyl-CoA and CoA. A Nanoluc-NAA50 fusion protein retains this specificity and can be used to generate a bioluminescence resonance energy transfer (BRET) signal in the presence of a CoA-linked fluorophore. This enables the development of a ligand displacement assay in which CoA metabolites are detected via their ability to bind the Nanoluc-NAA50 protein host and compete binding of the CoA-linked fluorophore guest. We demonstrate that the specificity of ligand displacement reflects the molecular recognition of the NAA50 host, while the window of dynamic sensing can be controlled by tuning the binding affinity of the CoA-linked fluorophore guest. Finally, we show the methods specificity for acetyl-CoA can be harnessed for gain-of-signal optical detection of enzyme activity. Overall, our studies demonstrate the potential of harnessing insights from chemoproteomics for molecular sensing and provide a foundation for future applications in target engagement and selective metabolite detection.

biochemistry↗

bioRxiv2019

Injectable nanoclay gels for angiogenesis

The retention and sustained activity of therapeutic proteins at delivery sites are goals of regenerative medicine. Vascular endothelial growth factor (VEGF) has significant potential in promoting the growth and regeneration of blood vessels but is intrinsically labile. This is exacerbated by the inflammatory microenvironments at sites requiring regeneration. For VEGF to be efficacious it may require a carrier that stabilises it, protects it from degradation and retains it at a site of interest. In this study we tested the hypothesis that injectable nanoclay gels composed of Laponite XLG can stabilise VEGF and retain it in active form for therapeutic delivery. To achieve this, VEGF was incorporated in Laponite gels and its activity tested at a range of concentrations using in vivo cell culture tubulogenesis assays and in vivo angiogenesis assays. We found that VEGF-Laponite gels enhanced tubulogenesis in a dose-dependent manner in vivo. When administered subcutaneously in vivo Laponite was retained at an injection site for up to a period of three weeks and promoted a 4-fold increase in blood vessel formation compared with alginate or vehicle controls as confirmed by CD31 staining. Notably, in contrast to alginate, Laponite gels did not release VEGF, indicating a strong interaction between the growth factor and the nanoclay, and suggesting that Laponite enhancement of VEGF efficacy is due to its retention at an implantation site over a prolonged period. Our approach provides a robust method for delivery of bioactive recombinant VEGF without the necessity for complex hydrogel or protein engineering.

bioengineering↗