Evidence of differential mass change rates between human breast cancer cell lines in culture.

Investigating the growth signatures of single cells will determine how cell growth is regulated and cell size is maintained. The ability to precisely measure such changes and alterations in cell size and cell mass could be important for applications in cancer and drug screening. Here, we measure the mass growth rate of individual benign (MCF-10A), non-invasive (MCF-7), and highly-invasive malignant (MDA-MB-231) breast cancer cells. A micro-patterning technique was employed to allow for the long-term growth of motile cells. Results show mass growth rates at 4.8%, 1.2%, and 2.8% for MCF-10A, MCF-7, and MDA-MB-231, demonstrating that normal cells have a higher mass growth rate than cancerous cells. All the cell lines show an increase in mass change rate indicating that the mass accumulation rate is exponential over a single cell cycle. The growth rates measured with our MEMS sensor are compared with doubling times obtained through conventional bulk analysis techniques, and exhibit excellent agreement.

Aligning Synthetic Hippocampal Neural Circuits via Self-Rolled-Up Silicon Nitride Microtube Arrays.

Directing neurons to form predetermined circuits with the intention of treating neurological disorders and neurodegenerative diseases is a fundamental goal and current challenge in neuroengineering. Until recently, only neuronal aggregates were studied and characterized in culture, which can limit information gathered to populations of cells. In this study, we use a substrate constructed of arrays of strain-induced self-rolled-up membrane 3D architectures. This results in changes in the neuronal architecture and altered growth dynamics of neurites. Hippocampal neurons from postnatal rats were cultured at low confluency (∼250 cells mm-2) on an array of transparent rolled-up microtubes (µ-tubes; 4-5 µm diameter) of varying topographical arrangements. Neurite growth on the µ-tubes was characterized and compared to controls in order to establish a baseline for alignment imposed by the topography. Compared to control substrates, neurites are significantly more aligned toward the 0° reference on the µ-tube array. Pitch (20-60 and 100 µm) and µ-tube length (30-80 µm) of array elements were also varied to investigate their impact on neurite alignment. We found that alignment was improved by the gradient pitch arrangement and with longer µ-tubes. Application of this technology will enhance the ability to construct intentional neural circuits through array design and manipulation of individual neurons and can be adapted to address challenges in neural repair, reinnervation, and neuroregeneration.

Toward intelligent synthetic neural circuits: directing and accelerating neuron cell growth by self-rolled-up silicon nitride microtube array.

In neural interface platforms, cultures are often carried out on a flat, open, rigid, and opaque substrate, posing challenges to reflecting the native microenvironment of the brain and precise engagement with neurons. Here we present a neuron cell culturing platform that consists of arrays of ordered microtubes (2.7-4.4 µm in diameter), formed by strain-induced self-rolled-up nanomembrane (s-RUM) technology using ultrathin (<40 nm) silicon nitride (SiNx) film on transparent substrates. These microtubes demonstrated robust physical confinement and unprecedented guidance effect toward outgrowth of primary cortical neurons, with a coaxially confined configuration resembling that of myelin sheaths. The dynamic neural growth inside the microtube, evaluated with continuous live-cell imaging, showed a marked increase (20×) of the growth rate inside the microtube compared to regions outside the microtubes. We attribute the dramatic accelerating effect and precise guiding of the microtube array to three-dimensional (3D) adhesion and electrostatic interaction with the SiNx microtubes, respectively. This work has clear implications toward building intelligent synthetic neural circuits by arranging the size, site, and patterns of the microtube array, for potential treatment of neurological disorders.