Interfacing human induced pluripotent stem cell-derived neurons with nanowire arrays of altering length, pitch and diameter
Micro structured substrates such as arrayed micro pillars, fibrin hydrogels or chitin-alginate fibrous micro scaffolds have been used to maintain and proliferate pluripotent stem cells. In this work, we demonstrate that micro structured substrates containing nanowire arrays can also be used to conduct the differentiation of human induced pluripotent stem cells (hiPSCs) into mature neurons.
To date, nanowire arrays have been used for studying cell properties of cancer cell lines or rodent neurons with respect to viability, migration, and cell stiffness or to transfect cells, to name a few. However, the feasibility to employ human neurons on nanowire arrays significantly extends the pertinence in the field, since it opens up the arena to study neurological diseases like Parkinson’s or multiple sclerosis by nanowire assisted drug delivery and cell transfection.
Herein, two different protocols for the differentiation of hiPSCs into mature neurons were utilized and applied to nanowire arrays of varying nanowire length, diameter, and array pitch, but identical surface chemistry—namely, biocompatible aluminum oxide deposited by atomic layer deposition. We demonstrate, that the interaction regime between neuron and nanowire can be tuned from a fakir-like state where the cell is resting on the very nanowire tip to a complete engulfment of the nanowire defined by the combination of nanowire length, diameter and array pitch. Generally, long and thick nanowires with a small array pitch facilitate a fakir-like state—and vice versa. In particular, our results confirm the model by Buch-Månson et al. In detail, the neuron/nanowire interface was investigated with z-stacks prepared by fluorescent confocal microscopy and cross sections prepared by focused ion beam milling and imaged by scanning electron microscopy. Furthermore, we demonstrate that cell viability is generally unimpaired when cultured on nanowire arrays tested for up to two weeks. Additionally, we found no influence of the settling behavior on the electrophysiological properties analyzed by patch clamp measurements: Neurons matured on nanowires have similar passive membrane properties as on planar reference samples and show an eminent capability to fire action potentials.
To conclude, our experimental results form an excellent starting point for studies on human induced pluripotent stem cells–derived neuron interfaced with nanowire-based arrays for signal stimulation and sensing or drug delivery.