Denis Scaini

Traditional 3D bioprinting of corneal constructs relies on planar slicing, which often results in a significant stairstep effect and the loss of anatomical curvature. Curvilinear layering has emerged as a promising alternative to address these limitations. The presented methodology, based on non-planar layer integration, ensures a smoother surface finish. The model’s surface is identified via vertex normals and reconstructed using the Poisson method. Finally, surface parametrization is applied to generate spatially curved trajectories. To validate the algorithm, corneal constructs were printed using a planar and the proposed non-planar approach. Quantitative evaluation of micro-Computed Tomography data revealed that the non-planar approach achieved significantly higher morphological fidelity, successfully replicating the intended parabolic profile of the human cornea. Furthermore, the non-planar constructs demonstrated adequate functional performance, characterized by high optical transparency. Thereby, the feasibility of printing non-planar layers using the proposed novel approach is successfully demonstrated. Furthermore, the comparative analysis confirms the method’s potential for corneal biofabrication when compared to traditional planar methods.

Among emerging technologies developed to interface neuronal signaling, engineering electrodes at the nanoscale would yield more precise biodevices opening to progress in neural circuit investigations and to new therapeutic potential. Despite remarkable progress in miniature electronics for less invasive neurostimulation, most nano-enabled, optically triggered interfaces are demonstrated in cultured cells, which precludes the studies of natural neural circuits. We exploit here free-standing silicon-based nanoscale photodiodes to optically modulate single, identified neurons in mammalian spinal cord explants. With near-infrared light stimulation, we show that activating single excitatory or inhibitory neurons differently affects sensory circuits processing in the dorsal horn. We successfully functionalize nano-photodiodes to target single molecules, such as glutamate AMPA receptor subunits, thus enabling light activation of specific synaptic pathways. We conclude that nano-enabled neural interfaces can modulate selected sensory networks with low invasiveness. The use of nanoscale photodiodes can thus provide original perspective in linking neural activity to specific behavioral outcome.

In recent years, the quest for surface modifications to promote neuronal cell interfacing and modulation has risen. This course is justified by the requirements of emerging technological and medical approaches attempting to effectively interact with central nervous system cells, as in the case of brain-machine interfaces or neuroprosthetic. In that regard, the remarkable cytocompatibility and ease of chemical functionalization characterizing surface-immobilized graphene-based nanomaterials (GBNs) make them increasingly appealing for these purposes. Here, we compared the (morpho)mechanical and functional adaptation of rat primary hippocampal neurons when interfaced with surfaces covered with pristine single-layer graphene (pSLG) and phenylacetic acid-functionalized single-layer graphene (fSLG). Our results confirmed the intrinsic ability of glass-supported single-layer graphene to boost neuronal activity highlighting, conversely, the downturn inducible by the surface insertion of phenylacetic acid moieties. fSLG-interfaced neurons showed a significant reduction in spontaneous postsynaptic currents (PSCs), coupled to reduced cell stiffness and altered focal adhesion organization compared to control samples. Overall, we have here demonstrated that graphene substrates, both pristine and functionalized, could be alternatively used to intrinsically promote or depress neuronal activity in primary hippocampal cultures.

The quest for surfaces able to interface cells and modulate their functionality has raised, in recent years, the development of biomaterials endowed with nanocues capable of mimicking the natural extracellular matrix (ECM), especially for tissue regeneration purposes. In this context, carbon nanotubes (CNTs) are optimal candidates, showing dimensions and a morphology comparable to fibril ECM constituents. Moreover, when immobilized onto surfaces, they demonstrated outstanding cytocompatibility and ease of chemical modification with ad hoc functionalities. In this study, we interface porcine aortic valve interstitial cells (pVICs) to multi-walled carbon nanotube (MWNT) carpets, investigating the impact of surface nano-morphology on cell properties. The results obtained indicate that CNTs significantly affect cell behavior in terms of cell morphology, cytoskeleton organization, and mechanical properties. We discovered that CNT carpets appear to maintain interfaced pVICs in a sort of “quiescent state”, hampering cell activation into a myofibroblasts-like phenotype morphology, a cellular evolution prodromal to Calcific Aortic Valve Disease (CAVD) and characterized by valve interstitial tissue stiffening. We found that this phenomenon is linked to CNTs’ ability to alter cell tensional homeostasis, interacting with cell plasma membranes, stabilizing focal adhesions and enabling a better strain distribution within cells. Our discovery contributes to shedding new light on the ECM contribution in modulating cell behavior and will open the door to new criteria for designing nanostructured scaffolds to drive cell functionality for tissue engineering applications.

Graphene unique physicochemical properties made it prominent among other allotropic forms of carbon, in many areas of research and technological applications. Interestingly, in recent years, many studies exploited the use of graphene family nanomaterials (GNMs) for biomedical applications such as drug delivery, diagnostics, bioimaging, and tissue engineering research. GNMs are successfully used for the design of scaffolds for controlled induction of cell differentiation and tissue regeneration. Critically, it is important to identify the more appropriate nano/bio material interface sustaining cells differentiation and tissue regeneration enhancement. Specifically, this review is focussed on graphene‐based scaffolds that endow physiochemical and biological properties suitable for a specific tissue, the nervous system, that links tightly morphological and electrical properties. Different strategies are reviewed to exploit GNMs for neuronal engineering and regeneration, material toxicity, and biocompatibility. Specifically, the potentiality for neuronal stem cells differentiation and subsequent neuronal network growth as well as the impact of electrical stimulation through GNM on cells is presented. The use of field effect transistor (FET) based on graphene for neuronal regeneration is described. This review concludes the important aspects to be controlled to make graphene a promising candidate for further advanced application in neuronal tissue engineering and biomedical use.

Mechanical properties of living cells determined by cytoskeletal elements play a crucial role in a wide range of biological functions.

The use of nanostructured materials and nanosized‐topographies has the potential to impact the performance of implantable biodevices, including neural interfaces, enhancing their sensitivity and selectivity, while reducing tissue reactivity. As a result, current trends in biosensor technology require the effective ability to improve devices with controlled nanostructures. Nanoimprint lithography to pattern surfaces with high‐density and high aspect ratio nanopillars (NPs) made of polystyrene (PS‐NP, insulating), or of a polystyrene/carbon‐nanotube nanocomposite (PS‐CNT‐NP, electrically conductive) are exploited. Both substrates are challenged with cultured primary neurons. They are demonstrated to support the development of suspended synaptic networks at the NPs’ interfaces characterized by a reduction in proliferating neuroglia, and a boost in neuronal emergent electrical activity when compared to flat controls. The authors successfully exploit their conductive PS‐CNT‐NPs to stimulate cultured cells electrically. The ability of both nanostructured surfaces to interface tissue explants isolated from the mouse spinal cord is then tested. The integration of the neuronal circuits with the NP topology, the suspended nature of the cultured networks, the reduced neuroglia formation, and the higher network activity together with the ability to deliver electrical stimuli via PS‐CNT‐NP reveal such platforms as promising designs to implement on neuro‐prosthetic or neurostimulation devices.