Suuronen, J.-P. | Search bioRxiv

bioRxiv2026

Material-driven fibronectin assembly enables low-dose BMP-2 to regenerate structurally mature bone in critical-sized load-bearing defects

Bone grafts for critical-sized load-bearing defects are usually judged by how much bone forms, and rarely by whether that bone is structurally and mechanically competent. Here, degradable ceramic monetites coated with poly(ethyl acrylate) (PEA) and functionalised with fibronectin (FN) and rhBMP-2 at 10-25 g/mL, 60-150-fold below the approved clinical concentration, are assessed across length scales. MicroCT showed that only monetites functionalised with rhBMP-2 bridged the defect, with a significant increase in new bone volume in both the monetite vicinity and the whole defect volume. In contrast, platelet-rich plasma (PRP) functionalisation significantly reduced bone formation relative to FN, showing that the identity of the adhesion cue, and not merely its presence, determines the outcome. Monetite degradation and increased interconnected porosity favoured bone ingrowth and produced a continuous interface between monetite and new bone. The multiscale analyses of quantitative polarised light microscopy, SAXS and nanoindentation show that PEA-coated monetites functionalised with FN and 25 g/mL rhBMP-2 promoted structurally and mechanically more mature bone, with a hierarchical organisation and local mechanical properties approaching those of native cortical tissue. In the bridged region this group recapitulated the preferential collagen fibre orientation of native cortical bone and reached an elastic modulus and hardness that were not statistically distinguishable from it, although mineral particles throughout the regenerated tissue remained thicker and less aligned than in cortical bone. Synchrotron microCT in an ovine model extended these findings to a clinically relevant scale, supporting the translational potential of the system. Taken together, these findings position PEA-coated monetites functionalised with FN and low-dose rhBMP-2 as a strategy for the structural and functional regeneration of large bone defects.

bioengineering↗

bioRxiv2021

Binocular Mirror-Symmetric Microsaccadic Sampling of Hyperacute 3D-Vision

Neural mechanisms behind stereopsis, which requires simultaneous disparity inputs from two eyes, have remained mysterious. Here we show how ultrafast mirror-symmetric photomechanical contractions in the frontal forward-facing left and right eye photoreceptors give Drosophila super-resolution 3D-vision. By interlinking multiscale in vivo assays with multiscale simulations, we reveal how these photoreceptor microsaccades - by verging, diverging and narrowing the eyes overlapping receptive fields - channel depth information, as phasic binocular image motion disparity signals in time. We further show how peripherally, outside stereopsis, microsaccadic sampling tracks a flying flys optic flow field to better resolve the world in motion. These results change our understanding of how insect compound eyes work and suggest a general dynamic stereo-information sampling strategy for animals, robots and sensors. Significance statementTo move efficiently, animals must continuously work out their x,y,z-positions in respect to real-world objects, and many animals have a pair of eyes to achieve this. How photoreceptors actively sample the eyes optical image disparity is not understood because this fundamental information-limiting step has not been investigated in vivo over the eyes whole sampling matrix. This integrative multiscale study will advance our current understanding of stereopsis from static image disparity comparison to a new morphodynamic active sampling theory. It shows how photomechanical photoreceptor microsaccades enable Drosophila super-resolution 3D-vision and proposes neural computations for accurately predicting these flies depth-perception dynamics, limits, and visual behaviors.

neuroscience↗