There is a high demand for in vitro models of the central nervous system (CNS) to study neurological disorders, injuries, toxicity, and drug efficacy. Three-dimensional (3D) in vitro models can bridge the gap between traditional two-dimensional culture and animal models because they present an in vivo-like microenvironment in a tailorable experimental platform. Within the expanding variety of sophisticated 3D cultures, scaffold-free, self-assembled spheroid culture avoids the introduction of foreign materials and preserves the native cell populations and extracellular matrix types. In this study, we generated 3D spheroids with primary postnatal rat cortical cells using an accessible, size-controlled, reproducible, and cost-effective method. Neurons and glia formed laminin-containing 3D networks within the spheroids. The neurons were electrically active and formed circuitry through both excitatory and inhibitory synapses. The mechanical properties of the spheroids were in the range of brain tissue. These in vivo-like features of 3D cortical spheroids provide the potential for relevant and translatable investigations of the CNS in vitro.

Polymeric microspheres (MSs) have received attention for their potential to improve the delivery of drugs with poor oral bioavailability. Although MSs can be absorbed into the absorptive epithelium of the small intestine, little is known about the physiologic mechanisms that are responsible for their cellular trafficking. In these experiments, nonbiodegradable polystyrene MSs (diameter range: 500 nm to 5 μm) were delivered locally to the jejunum or ileum or by oral administration to young male rats. Following administration, MSs were taken up rapidly (≤5 min) by the small intestine and were detected by transmission electron microscopy and confocal laser scanning microscopy. Gel permeation chromatography confirmed that polymer was present in all tissue samples, including the brain. These results confirm that MSs (diameter range: 500 nm to 5 μm) were absorbed by the small intestine and distributed throughout the rat. After delivering MSs to the jejunum or ileum, high concentrations of polystyrene were detected in the liver, kidneys, and lungs. The pharmacologic inhibitors chlorpromazine, phorbol 12-myristate 13-acetate, and cytochalasin D caused a reduction in the total number of MSs absorbed in the jejunum and ileum, demonstrating that nonphagocytic processes (including endocytosis) direct the uptake of MSs in the small intestine. These results challenge the convention that phagocytic cells such as the microfold cells solely facilitate MS absorption in the small intestine.oral delivery | uptake mechanism B eginning in the 1960s, several groups (1-7) demonstrated that the small intestine could absorb microparticles with a diameter >1 μm, challenging dogma that the small intestine could only absorb small macromolecules. After this discovery, researchers began engineering microspheres (MSs) to deliver drugs with poor water solubility (8-10), poor gastrointestinal permeability (11), or poor oral bioavailability (8,9,(12)(13)(14)(15) to the small intestine. MS-based oral drug delivery systems (ODDSs) can be made from biodegradable polymers (12,(16)(17)(18), nondegradable polymers (19-21), and polysaccharides (22, 23) and can be engineered to carry polypeptides (18,24,25) and other molecules (26, 27). The motivation for using microparticulate-based ODDSs is to improve the oral bioavailability of drugs by enhancing their delivery and transit through the absorptive epithelium of the small intestine. This work may ultimately enable patients to take medications orally instead of relying on daily or weekly injections or other, less convenient routes of administration (28).More than five decades after Sanders and Ashworth discovered that the small intestine can engulf large particles (1), little is known today about the cellular mechanisms or physiologic pathways that facilitate the absorption, transit, and biodistribution of microparticles that are delivered to the small intestine. Nonetheless, the diverse physiology and multitude of cell types in the small intestine likely play a central role in these processes. The absorp...

Summary Three-dimensional (3D) in vitro cultures recapitulate key features of the brain including morphology, cell-cell and cell-extracellular matrix interactions, gradients of factors, and mechanical properties. However, there remains a need for experimental and computational tools to investigate network functions in these 3D models. To address this need, we present an experimental system based on 3D scaffold-based cortical neuron cultures in which we expressed the genetically encoded calcium indicator GCaMP6f to record neuronal activity at the millimeter-scale. Functional neural network descriptors were computed with graph-theory-based network analysis methods, showing the formation of functional networks at 3 weeks of culture. Changes to the functional network properties upon perturbations to glutamatergic neurotransmission or GABAergic neurotransmission were quantitatively characterized. The results illustrate the applicability of our 3D experimental system for the study of brain network development, function, and disruption in a biomimetic microenvironment.