5 research outputs found
Effect of Graphene on Nonneuronal and Neuronal Cell Viability and Stress
In recent years graphene has drawn
considerable research interest
for biomedical applications. However, applications of graphene in
biological systems also raise concerns about its possible toxicity.
Here, by using live cell imaging techniques, we investigate the effect
of pristine graphene on the viability as well as stress of both nonneuronal
and neuronal cells under physiological conditions. We find that graphene
promotes cell adhesion and proliferation. Furthermore, we find that
graphene has no detectable adverse effect on mitochondrial membrane
potential and morphology, or autophagy levels in the cell, indicating
that graphene does not induce cell stress. Our results highlight the
potential of graphene to be used in biomedical applications by providing
long-term and stable nonneural and neural interfaces
Slow DNA Transport through Nanopores in Hafnium Oxide Membranes
We present a study of double- and single-stranded DNA transport through nanopores fabricated in ultrathin (2ā7 nm thick) freestanding hafnium oxide (HfO<sub>2</sub>) membranes. The high chemical stability of ultrathin HfO<sub>2</sub> enables long-lived experiments with <2 nm diameter pores that last several hours, in which we observe >50ā000 DNA translocations with no detectable pore expansion. Mean DNA velocities are slower than velocities through comparable silicon nitride pores, providing evidence that HfO<sub>2</sub> nanopores have favorable physicochemical interactions with nucleic acids that can be leveraged to slow down DNA in a nanopore
Synthetically Encoded Ultrashort-Channel Nanowire Transistors for Fast, Pointlike Cellular Signal Detection
Nanostructures, which have sizes comparable to biological
functional
units involved in cellular communication, offer the potential for
enhanced sensitivity and spatial resolution compared to planar metal
and semiconductor structures. Silicon nanowire (SiNW) field-effect
transistors (FETs) have been used as a platform for biomolecular sensors,
which maintain excellent signal-to-noise ratios while operating on
lengths scales that enable efficient extra- and intracellular integration
with living cells. Although the NWs are tens of nanometers in diameter,
the active region of the NW FET devices typically spans micrometers,
limiting both the length and time scales of detection achievable with
these nanodevices. Here, we report a new synthetic method that combines
gold-nanocluster-catalyzed vaporāliquidāsolid (VLS)
and vaporāsolidāsolid (VSS) NW growth modes to produce
synthetically encoded NW devices with ultrasharp (<5 nm) n-type
highly doped (n<sup>++</sup>) to lightly doped (n) transitions along
the NW growth direction, where n<sup>++</sup> regions serve as source/drain
(S/D) electrodes and the n-region functions as an active FET channel.
Using this method, we synthesized short-channel n<sup>++</sup>/n/n<sup>++</sup> SiNW FET devices with independently controllable diameters
and channel lengths. SiNW devices with channel lengths of 50, 80,
and 150 nm interfaced with spontaneously beating cardiomyocytes exhibited
well-defined extracellular field potential signals with signal-to-noise
values of ca. 4 independent of device size. Significantly, these āpointlikeā
devices yield peak widths of ā¼500 Ī¼s, which is comparable
to the reported time constant for individual sodium ion channels.
Multiple FET devices with device separations smaller than 2 Ī¼m
were also encoded on single SiNWs, thus enabling multiplexed recording
from single cells and cell networks with device-to-device time resolution
on the order of a few microseconds. These short-channel SiNW FET devices
provide a new opportunity to create nanoscale biomolecular sensors
that operate on the length and time scales previously inaccessible
by other techniques but necessary to investigate fundamental, subcellular
biological processes
Outside Looking In: Nanotube Transistor Intracellular Sensors
Nanowire-based field-effect transistors, including devices
with
planar and three-dimensional configurations, are being actively explored
as detectors for extra- and intracellular recording due to their small
size and high sensitivities. Here we report the synthesis, fabrication,
and characterization of a new needle-shaped nanoprobe based on an
active silicon nanotube transistor, ANTT, that enables high-resolution
intracellular recording. In the ANTT probe, the source/drain contacts
to the silicon nanotube are fabricated on one end, passivated from
external solution, and then time-dependent changes in potential can
be recorded from the opposite nanotube end via the solution filling
the tube. Measurements of conductance versus water-gate potential
in aqueous solution show that the ANTT probe is selectively gated
by potential changes within the nanotube, thus demonstrating the basic
operating principle of the ANTT device. Studies interfacing the ANTT
probe with spontaneously beating cardiomyocytes yielded stable intracellular
action potentials similar to those reported by other electrophysiological
techniques. In addition, the straightforward fabrication of ANTT devices
was exploited to prepare multiple ANTT structures at the end of single
probes, which enabled multiplexed recording of intracellular action
potentials from single cells and multiplexed arrays of single ANTT
device probes. These studies open up unique opportunities for multisite
recordings from individual cells through cellular networks
Nanocomposite Gold-Silk Nanofibers
Cell-biomaterial interactions can be controlled by modifying
the
surface chemistry or nanotopography of the material, to induce cell
proliferation and differentiation if desired. Here we combine both
approaches in forming silk nanofibers (SNFs) containing gold nanoparticles
(AuNPs) and subsequently chemically modifying the fibers. Silk fibroin
mixed with gold seed nanoparticles was electrospun to form SNFs doped
with gold seed nanoparticles (SNF<sub>seed</sub>). Following gold
reduction, there was a 2-fold increase in particle diameter confirmed
by the appearance of a strong absorption peak at 525 nm. AuNPs were
dispersed throughout the AuNP-doped silk nanofibers (SNFs<sub>Au</sub>). The Youngās modulus of the SNFs<sub>Au</sub> was almost
70% higher than that of SNFs. SNFs<sub>Au</sub> were modified with
the arginine-glycine-aspartic acid (RGD) peptide. Human mesenchymal
stem cells that were cultured on RGD-modified SNF<sub>Au</sub> had
a more than 2-fold larger cell area compared to the cells cultured
on bare SNFs; SNF<sub>Au</sub> also increased cell size. This approach
may be used to alter the cellāmaterial interface in tissue
engineering and other applications