Lower fluidity of supported lipid bilayers promotes neuronal differentiation of neural stem cells by enhancing focal adhesion formation

Concealing Organic Neuromorphic Devices with Neuronal-Inspired Supported Lipid Bilayers

Neurohybrid systems have gained large attention for their potential as in vitro and in vivo platform to interrogate and modulate the activity of cells and tissue within nervous system. In this scenario organic neuromorphic devices have been engineered as bioelectronic platforms to resemble characteristic neuronal functions. However, aiming to a functional communication with neuronal cells, material synthesis, and surface engineering can yet be exploited for optimizing bio-recognition processes at the neuromorphic-neuronal hybrid interface. In this work, artificial neuronal-inspired lipid bilayers have been assembled on an electrochemical neuromorphic organic device (ENODe) to resemble post-synaptic structural and functional features of living synapses. Here, synaptic conditioning has been achieved by introducing two neurotransmitter-mediated biochemical signals, to induce an irreversible change in the device conductance thus achieving Pavlovian associative learning. This new class of in vitro devices can be further exploited for assembling hybrid neuronal networks and potentially for in vivo integration within living neuronal tissues.

Acellularized Uvea Hydrogel as Novel Injectable Platform for Cell-Based Delivering Treatment of Retinal Degeneration and Optimizing Retinal Organoids Inducible System

Replenishing the retina with retinal pigment epithelial (RPE) cells derived from pluripotent stem cells (PSCs) has great promise for treating retinal degenerative diseases, but it is limited by poor cell survival and integration in vivo. Herein, porcine acellular sclera and uvea extracellular matrix (ECM) and their counterpart hydrogels are developed, and their effects on the biological behavior of human induced pluripotent stem cell (hiPSC)-derived RPE cells (hiPSC-RPE) and embryoid body (hiPSC-EB) differentiation are investigated. Both acellular ECM hydrogels have excellent biocompatibility and suitable biodegradability without evoking an obvious immune response. Most importantly, the decellularized uvea hydrogel-delivered cells' injection remarkably promotes the hiPSC-RPE cells' survival and integration in the subretinal space, rescues the photoreceptor cells' death and retinal gliosis, and restores vision in rats with retinal degeneration for a long duration. In addition, medium supplementation with decellularized uvea peptides promotes hiPSC-EBs onset morphogenesis and neural/retinal differentiation, forming layered retinal organoids. This study demonstrates that ECM hydrogel-delivered hiPSC-RPE cells' injection may be a useful approach for treating retinal degeneration disease, combined with an optimized retinal seeding cells' induction program, which has potential for clinical application.

Surface Viscosity-Dependent Neurite Initiation in Cortical Neurons

Dynamic extracellular environments profoundly affect the behavior and function of cells both biochemically and mechanically. Neurite initiation is the first step for neurons to establish intricate neuronal networks. How such a process is modulated by mechanical factors is not fully understood. Particularly, it is unknown whether the molecular clutch model, which has been used to explain cell responses to matrix rigidity, also holds for neurite initiation. To study how mechanical properties modulate neurite initiation, substrates with various well-defined surface viscosities using supported lipid bilayers (SLBs) are synthesized. The results show that ligands with intermediate viscosity greatly maximize neurite initiation in primary neurons, while neurite initiation is drastically limited on substrates with higher or lower viscosity. Importantly, biochemical characterizations reveal altered focal adhesion and calpain activity are associated with distinct neurite initiation patterns. Collectively, these results indicate that neurite initiation is surface viscosity-dependent; there is an optimal range of surface viscosities to drive neurite initiation. Upon binding to ligands of varying viscosities, calpain activity is differentially triggered and leads to distinct levels of neurite outgrowth. These findings not only enhance the understanding of how extracellular environments regulate neurons, but also demonstrate the potential utility of SLBs for neural tissue engineering applications.

Advances in Cell-Conductive Polymer Biointerfaces and Role of the Plasma Membrane

The plasma membrane (PM) is often described as a wall, a physical barrier separating the cell cytoplasm from the extracellular matrix (ECM). Yet, this wall is a highly dynamic structure that can stretch, bend, and bud, allowing cells to respond and adapt to their surrounding environment. Inspired by shapes and geometries found in the biological world and exploiting the intrinsic properties of conductive polymers (CPs), several biomimetic strategies based on substrate dimensionality have been tailored in order to optimize the cell–chip coupling. Furthermore, device biofunctionalization through the use of ECM proteins or lipid bilayers have proven successful approaches to further maximize interfacial interactions. As the bio-electronic field aims at narrowing the gap between the electronic and the biological world, the possibility of effectively disguising conductive materials to “trick” cells to recognize artificial devices as part of their biological environment is a promising approach on the road to the seamless platform integration with cells.

A Study of the Effects of Plasma Surface Treatment on Lipid Bilayers Self-Spreading on a Polydimethylsiloxane Substrate under Different Treatment Times

Plasma-treated poly(dimethylsiloxane) (PDMS)-supported lipid bilayers are used as functional tools for studying cell membrane properties and as platforms for biotechnology applications. Self-spreading is a versatile method for forming lipid bilayers. However, few studies have focused on the effect of plasma treatment on self-spreading lipid bilayer formation. In this paper, we performed lipid bilayer self-spreading on a PDMS surface with different treatment times. Surface characterization of PDMS treated with different treatment times is evaluated by AFM and SEM, and the effects of plasma treatment of the PDMS surface on lipid bilayer self-spreading behavior is investigated by confocal microscopy. The front-edge velocity of lipid bilayers increases with the plasma treatment time. By theoretical analyses with the extended-DLVO modeling, we find that the most likely cause of the velocity change is the hydration repulsion energy between the PDMS surface and lipid bilayers. Moreover, the growth behavior of membrane lobes on the underlying self-spreading lipid bilayer was affected by topography changes in the PDMS surface resulting from plasma treatment. Our findings suggest that the growth of self-spreading lipid bilayers can be controlled by changing the plasma treatment time.

Mussel-Inspired Redox-Active and Hydrophilic Conductive Polymer Nanoparticles for Adhesive Hydrogel Bioelectronics

Conductive polymers (CPs) are generally insoluble, and developing hydrophilic CPs is significant to broaden the applications of CPs. In this work, a mussel-inspired strategy was proposed to construct hydrophilic CP nanoparticles (CP NPs), while endowing the CP NPs with redox activity and biocompatibility. This is a universal strategy applicable for a series of CPs, including polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene). The catechol/quinone contained sulfonated lignin (LS) was doped into various CPs to form CP/LS NPs with hydrophilicity, conductivity, and redox activity. These CP/LS NPs were used as versatile nanofillers to prepare the conductive hydrogels with long-term adhesiveness. The CP/LS NPs-incorporated hydrogels have a good conductivity because of the uniform distribution of the hydrophilic NPs in the hydrogel network, forming a well-connected electric path. The hydrogel exhibits long-term adhesiveness, which is attributed to the mussel-inspired dynamic redox balance of catechol/quinone groups on the CP/LS NPs. This conductive and adhesive hydrogel shows good electroactivity and biocompatibility and therefore has broad applications in electrostimulation of tissue regeneration and implantable bioelectronics.

Supramolecular Nanofibers for Encapsulation and In Situ Differentiation of Neural Stem Cells

Design and fabrication of fibrous materials by natural biological macromolecules in light of biomimetics to achieve spatially cellular arrangements are highly desirable in tissue engineering. Herein, chromatin-inspired supramolecular fibers formed through the interfacial polyelectrolyte complexation (IPC) process by DNA and histone proteins for encapsulation and in situ differentiation of murine brain-derived neural stem cells (NSCs) are reported. High cell viability of encapsulated NSCs demonstrates the excellent biocompatibility of fibers as 3D scaffolds. Moreover, a cell-adhesive peptide (K₆ -PEG-RGD) is introduced into fibers by electrostatic interaction to improve NSCs encapsulation efficiency and prevent them from migrating out of fibers for enhanced spatially cellular arrangement. In situ differentiation of NSCs into oligodendrocytes within fibers is revealed by immunocytochemical staining assay. Due to the robust abilities to encapsulate and in situ differentiate NSCs, these chromatin-inspired supramolecular fibers show great potential in neural system-related tissue.

Composite Lipid Bilayers from Cell Membrane Extracts and Artificial Mixes as a Cell Culture Platform

An artificial lipid bilayer is the closest possible model for the cell membrane. Despite that, current methods of lipid bilayer assembly and functionalization do not provide a satisfactory mimic of the cell-cell contact due to the inability to recreate an asymmetrical multicomponent system. In the current work, a method to produce an integrated solid-supported lipid bilayer combining natural extracts from cell membranes and artificially made lipid vesicles is proposed. This simple method allows delivery of transmembrane proteins and components of the extracellular matrix into the substrate. Biocompatibility of the composite natural/artificial lipid bilayers is evaluated by their interactions with the cardiomyocyte-like HL-1 cell line. Compared with fully artificial mixes, composite lipid bilayers allow cells to adhere and develop a morphologically more normal cytoskeleton.