Meneses, J. | bioRxiv Science

bioRxiv2023

3D printed magneto-active microfiber scaffolds for remote stimulation of 3D in vitro skeletal muscle models

Tunable culture platforms that guide cellular organization and mechanically stimulate skeletal muscle development are still unavailable due to limitations in biocompatibility and actuation triggered without contact. This study reports the rational design and fabrication of magneto-active microfiber meshes with controlled hexagonal microstructures via melt electrowriting (MEW) of a thermoplastic/graphene/iron oxide composite. In situ deposition of iron oxide nanoparticles on oxidized graphene yielded homogeneously dispersed magnetic particles with sizes above 0.5 m and low aspect ratio, preventing cellular internalization and toxicity. With these fillers, homogeneous magnetic composites with very high magnetic filler content (up to 10 wt.%) were obtained and successfully processed in a solvent-free manner for the first time. MEW of magnetic composites enabled the skeletal muscle-inspired design of hexagonal scaffolds with tunable fiber diameter, reconfigurable modularity, and zonal distribution of magneto-active and nonactive material. Importantly, the hexagonal microstructures displayed elastic deformability under tension, mitigating the mechanical limitations due to high filler content. External magnetic fields below 300 mT were sufficient to trigger out-of-plane reversible deformation leading to effective end-to-end length decrease up to 17%. Moreover, C2C12 myoblast culture on 3D Matrigel/collagen/MEW scaffolds showed that the presence of magnetic particles in the scaffolds did not significantly affect viability after 8 days with respect to scaffolds without magnetic filler. Importantly, in vitro culture demonstrated that myoblasts underwent differentiation at similar rates regardless of the presence of magnetic filler. Overall, these innovative microfiber scaffolds were proven as a magnetically deformable platform suitable for dynamic culture of skeletal muscle with potential for in vitro disease modeling.

bioengineering↗

bioRxiv2021

In vitro neuronal networks show bidirectional axonal conduction with antidromic action potentials effectively depolarizing the soma

Recent technological advances are revealing the complex physiology of the axon and challenging long-standing assumptions. Namely, while most action potential (AP) initiation occurs at the axon initial segment in central nervous system neurons, initiation in distal parts of the axon has been shown to occur in both physiological and pathological conditions. However, such ectopic action potential (EAP) activity has not been reported yet in studies using neuronal cultures and its functional role, if exists, is still not clear. Here, we show the spontaneous occurrence of EAPs and effective antidromic conduction in hippocampal neuronal cultures. We also observe a significant fraction of bidirectional axonal conduction in dorsal root ganglia neuronal cultures. We investigate and characterize this antidromic propagation via a combination of microfluidics, microelectrode arrays, advanced data analysis and in silico studies. We show that EAPs and antidromic conduction can occur spontaneously, and after distal axotomy or physiological changes in the axon biochemical environment. Conduction velocity is asymmetrical, with antidromic conduction being slower than orthodromic. Importantly, EAPs may carry information and can have a functional impact on the neuron, as they consistently depolarize the soma. Thus, plasticity or gene transduction mechanisms triggered by soma depolarization can also be affected by these antidromic APs. Altogether these findings have important implications for the study of neuronal function in vitro, reshaping our understanding on how information flows in neuronal cultures.

neuroscience↗