Murine cerebral organoids develop network of functional neurons and hippocampal brain region identity

Brain organoids are in vitro three-dimensional (3D) self-organized neural structures, which can enable disease modeling and drug screening. However, their use for standardized large-scale drug screening studies is limited by their high batch-to-batch variability, long differentiation time (10\u201320 weeks), and high production costs. This is particularly relevant when brain organoids are obtained from human induced pluripotent stem cells (iPSCs). Here, we developed, for the first time, a highly standardized, reproducible, and fast (5 weeks) murine brain organoid model starting from embryonic neural stem cells. We obtained brain organoids, which progressively differentiated and self-organized into 3D networks of functional neurons with dorsal forebrain phenotype. Furthermore, by adding the morphogen WNT3a, we generated brain organoids with specific hippocampal region identity. Overall, our results showed the establishment of a fast, robust and reproducible murine 3D in vitro brain model that may represent a useful tool for high-throughput drug screening and disease modeling

Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

We report on the superior electrochemical properties, in-vivo performance and long term stability under electrical stimulation of a new electrode material fabricated from lithographically patterned glassy carbon. For a direct comparison with conventional metal electrodes, similar ultra-flexible, micro-electrocorticography (μ-ECoG) arrays with platinum (Pt) or glassy carbon (GC) electrodes were manufactured. The GC microelectrodes have more than 70% wider electrochemical window and 70% higher CTC (charge transfer capacity) than Pt microelectrodes of similar geometry. Moreover, we demonstrate that the GC microelectrodes can withstand at least 5 million pulses at 0.45 mC/cm2 charge density with less than 7.5% impedance change, while the Pt microelectrodes delaminated after 1 million pulses. Additionally, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was selectively electrodeposited on both sets of devices to specifically reduce their impedances for smaller diameters (<60 μm). We observed that PEDOT-PSS adhered significantly better to GC than Pt, and allowed drastic reduction of electrode size while maintaining same amount of delivered current. The electrode arrays biocompatibility was demonstrated through in-vitro cell viability experiments, while acute in vivo characterization was performed in rats and showed that GC microelectrode arrays recorded somatosensory evoked potentials (SEP) with an almost twice SNR (signal-to-noise ratio) when compared to the Pt ones

NADPH reduces oligomerization rate of a pre-existing dimer-tetramer equilibrium in Trypanosoma brucei 6-phosphogluconate dehydrogenase

6-Phosphogluconate dehydrogenase (6PGDH), the third enzyme of the pentose phosphate pathway, catalyzes the NADP-dependent oxidative decarboxylation of 6-phosphogluconate (6PG) to ribulose-5-phosphate (RU5P). It not only gives NADPH and RU5P, but also depletes 6PG, whose accumulation induces cell senescence. It is a proposed drug target for African trypanosomiasis caused by T. brucei and for other microbial infections and cancer. We report here that the association of dimers to tetramers is an equilibrium present in the free enzyme, independently of the ligands. It has been shown by glutaraldehyde cross-linking, dynamic light scattering (DLS) and density gradient sedimentation. Both DLS and sedimentation indicate the enzyme size increases by increasing the enzyme concentration. In addition, gel filtration, density gradient sedimentation and isothermal titration calorimetry (ITC) reveal that the oligomerization rates are differently influenced by ligands. Indeed dynamic experiments where different oligomeric forms can be separated, show a strong NADPH shift of the enzyme versus the tetrameric form while NADP does not affect dimeric state of 6PGDH. Accordingly heat capacity change measured by ITC is different between NADP and NADPH binding (-92.56 against -520.35 cal/mol∙K) in agreement with a decreased solvent exposed surface area in tetramer. Tetramer is about 3-fold more active than dimer, indeed NADPH, the 6PGDH product and inhibitor, decreases interconversion rate while 6PG antagonizes NADPH effect. This is a further substrate way of promoting increased catalytic efficiency. The sheep liver 6PGDH, instead, by sedimentation studies appears always a dimer, the dimertetramer shift hence representing further drug exploitable potential

A New Drug Delivery System Based on Tauroursodeoxycholic Acid and PEDOT

Localized drug delivery represents one of the most challenging uses of systems based on conductive polymer films. Typically, anionic drugs are incorporated within conductive polymers through electrostatic interaction with the positively charged polymer. Following this approach, the synthetic glucocorticoid dexamethasone phosphate is often delivered from neural probes to reduce the inflammation of the surrounding tissue. In light of the recent literature on the neuroprotective and anti-inflammatory properties of tauroursodeoxycholic acid (TUDCA), for the first time, this natural bile acid was incorporated within poly(3,4-ethylenedioxythiophene) (PEDOT). The new material, PEDOT-TUDCA, efficiently promoted an electrochemically controlled delivery of the drug, while preserving optimal electrochemical properties. Moreover, the low cytotoxicity observed with viability assays, makes PEDOT-TUDCA a good candidate for prolonging the time span of chronic neural recording brain implants

On the longevity of flexible neural interfaces: Establishing biostability of polyimide-based intracortical implants

Flexible neural implants are extremely favored, as the most successful strategy to promote probe-tissue integration and avoid severe gliosis relies on reducing the mechanical mismatch between probe and brain tissue. But what are the realistic requirements for achieving chronic recording stability? What are the critical dimensions and main factors determining glial scar-free device integration? To answer these questions, two types of hair-sized polyimide-based flexible intracortical (PIXI) arrays were fabricated, differing only in their cross-sectional area. Chronic tissue reaction to both types was evaluated in rats, and in different implantation setups. Interfacial stresses were found to play a critical role in long-term tissue integration. Still, all the devices provided high quality chronic recordings of single units and inflammatory gene expression was not significantly upregulated for larger devices. Our study points out that the most relevant factor in eliciting FBR is played by mechanical probe-tissue interactions, that polyimide is well tolerated by the tissue, and that a holistic design - considering material properties, geometrical dimensions and assembling techniques - is the key towards longevity and long-term performance of intracortical probes. The optimization of only one parameter did not yet lead to the successful translation of research accomplishments into chronic preclinical and clinical applications

Conformable polyimide-based μECoGs: Bringing the electrodes closer to the signal source

none11Structural biocompatibility is a fundamental requirement for chronically stable bioelectronic devices. Newest neurotechnologies are increasingly focused on minimizing the foreign body response through the development of devices that match the mechanical properties of the implanted tissue and mimic its surface composition, often compromising on their robustness. In this study, an analytical approach is proposed to determine the threshold of conformability for polyimide-based electrocorticography devices. A finite element model was used to quantify the depression of the cortex following the application of devices mechanically above or below conformability threshold. Findings were validated in vivo on rat animal models. Impedance measurements were performed for 40 days after implantation to monitor the status of the biotic/abiotic interface with both conformable and non-conformable implants. Multi-unit activity was then recorded for 12 weeks after implantation using the most compliant device type. It can therefore be concluded that conformability is an essential prerequisite for steady and reliable implants which does not only depend on the Young's modulus of the device material: it strongly relies on the relation between tissue curvature at the implantation site and corresponding device's thickness and geometry, which eventually define the moment of inertia and the interactions at the material-tissue interface.mixedVomero M.; Porto Cruz M.F.; Zucchini E.; Ciarpella F.; Delfino E.; Carli S.; Boehler C.; Asplund M.; Ricci D.; Fadiga L.; Stieglitz T.Vomero, M.; Porto Cruz, M. F.; Zucchini, E.; Ciarpella, F.; Delfino, E.; Carli, S.; Boehler, C.; Asplund, M.; Ricci, D.; Fadiga, L.; Stieglitz, T