Novel aspects of neuronal differentiation in vitro and monitoring with advanced biosensor tools

Neuronal differentiation is a very complex and sophisticated cellular process that encompasses the development of mature neurons and their specialization. In this review we will focus on the novel and less well-known aspects of neuronal differentiation. Cell lines, to which some pro-differentiation drugs are added, have been widely used because of their convenience in terms of cost-efficiency, ease of use and reproducibility. After a brief overview of these systems, this review focuses on the new pharmacological aspects of differentiation related to mitochondrial changes and cellular redox homeostasis. A number of different parameters are commonly evaluated to assess neuronal differentiation. These include neurite length, differential gene expression, mitochondrial mass, free radical levels, enzyme induction and others. However, the classical techniques used to detect neuronal differentiation (such as immunochemistry, flow cytometry and gene expression analysis) are time-consuming or dependent on the subjective view of the researcher. On the other hand, emerging novel, miniaturized biosensor technologies have the potential to revolutionize the study of neuronal differentiation, by detecting neuron-derived electrical signals and differentiation markers, such as shape or attachment in a non-invasive and high throughput fashion. These state-of-the-art technologies are being extensively reviewed. Emphasis is given to progress, made in the field of integrated systems (including impedance sensing, microfluidics and associated nanotechnologies), neuronal differentiation in 3-D cultures and the identification of novel agents controlling neuronal cell fate.