Derailed transmembrane receptor trafficking could be a hallmark of tumorigenesis and increased tumor invasiveness, but receptor dynamics have not been used to differentiate metastatic cancer cells from less invasive ones. Using single-particle tracking techniques, we developed a phenotyping asssay named
T
ransmembrane
Re
ceptor
D
ynamics (TReD), studied the dynamics of epidermal growth factor receptor (EGFR) in seven breast epithelial cell lines and developed a phenotyping assay named
T
ransmembrane
Re
ceptor
D
ynamics (TReD). Here we show a clear evidence that increased EGFR diffusivity and enlarged EGFR confinement size in the plasma membrane (PM) are correlated with the enhanced metastatic potential in these cell lines. By comparing the TReD results with the gene expression profiles, we found a clear negative correlation between the EGFR diffusivities and the breast cancer luminal differentiation scores (r = −0.75). Upon the induction of epithelial-mesenchymal transition (EMT), EGFR diffusivity significantly increased for the non-tumorigenic MCF10A (99%) and the non-invasive MCF7 (56%) cells, but not for the highly metastatic MDA-MB-231 cell. We believe that the reorganization of actin filaments during EMT modified the PM structures, causing the receptor dynamics to change. TReD can thus serve as a new biophysical marker to probe the metastatic potential of cancer cells and even to monitor the transition of metastasis.
The advent of 3D
printing has had a disruptive impact in manufacturing
and can potentially revolutionize industrial fields. Thermoplastic
materials printable into complex structures are widely employed for
3D printing. Polylactic acid (PLA) is among the most promising polymers
used for 3D printing, owing to its low cost, biodegradability, and
nontoxicity. However, PLA is electrically insulating and mechanically
weak; this limits its use in a variety of 3D printing applications.
This study demonstrates a straightforward and environment-friendly
method to fabricate conductive and mechanically reinforced PLA composites
by incorporating graphene nanoplatelets (GNPs). To fully utilize the
superior electrical and mechanical properties of graphene, liquid-exfoliated
GNPs are dispersed in isopropyl alcohol without the addition of any
surfactant and combined with PLA dissolved in chloroform. The GNP–PLA
composites exhibit improved mechanical properties (improvement in
tensile strength by 44% and maximum strain by 57%) even at a low GNP
threshold concentration of 2 wt %. The GNP–PLA composites also
exhibit an electrical conductivity of over 1 mS/cm at >1.2 wt %.
The
GNP–PLA composites can be 3D-printed into various features
with electrical conductivity and mechanical flexibility. This work
presents a new direction toward advanced 3D printing technology by
providing higher flexibility in designing multifunctional 3D printed
features.
Here, we present
a three-dimensional two-color dual-particle tracking
(3D-2C-DPT) technique that can simultaneously localize two spectrally
distinct targets in three dimensions with a time resolution down to
5 ms. The dual-targets can be tracked with separation distances from
33 to 250 nm with tracking precisions of ∼15 nm (for static
targets) and ∼35 nm (for freely diffusing targets). Since each
target is individually localized, a wealth of data can be extracted,
such as the relative 3D position, the 2D rotation, and the separation
distance between the two targets. Using this technique, we turn a
double-stranded DNA (dsDNA)-linked dumbbell-like dimer into a nanoscopic
optical ruler to quantify the bending dynamics of nicked or gapped
dsDNA molecules in free solution by manipulating the design of dsDNA
linkers (1-nick, 3-nt, 6-nt, or 9-nt single-strand gap), and the results
show the increase of k
on (linear to bent)
from 3.2 to 10.7 s–1. The 3D-2C-DPT is then applied
to observe translational and rotational motions of the landing of an antibody-conjugated
nanoparticle on the plasma membrane of living cells, revealing the
reduction of rotations possibly due to interactions with membrane
receptors. This study demonstrates that this 3D-2C-DPT technique is
a new tool to shed light on the conformational changes of biomolecules
and the intermolecular interactions on plasma membrane.
A moment magnitude 5.4 earthquake struck the Pohang city located in the southeastern Korean Peninsula on 15 November 2017, possibly triggered by an enhanced geothermal system. Despite the moderate magnitude of the earthquake, extensive geotechnical and structural damage occurred. This study summarizes the widespread geotechnical damage resulted from the Pohang earthquake, observed during our reconnaissance trip. The affected area is mainly covered by Tertiary/Quaternary Alluvium underlain by mudstones with a thickness of approximately 500 m. Because of the soft grounds and shallow focal depth, this area experienced ground settlements up to 39 cm, building settlements that made apartments tilted by 1.6°. We also present observations on ground cracks, lateral spreadings, landslides, retaining wall deformations, and liquefactions. Documenting the damage is significant because (1) those are the first earthquake-induced damage observed in Korea, and (2) those are caused by the shallow-depth earthquake possibly induced by an enhanced geothermal system.
Polyaspartamide,
derived from polysuccinimide (PSI), has the advantage
of conveniently presenting desired functional groups by ring-opening
addition of amine-based nucleophiles to the succinimidyl ring moieties
of PSI. Using diamines with varying lengths of poly(ethylene glycol)
linker, polyaspartamide presenting amine groups with controllable
grafting density and length, namely, poly(2-hydroxyethyl aspartamide)-g-amino-poly(ethylene glycol) (PHEA–PEGAm) could
be synthesized. This PHEA–PEGAm was then used to develop in
situ forming hydrogels by Schiff base formation with aldehyde-containing
alginate (Alg-ALD). By modulating the graft architecture (i.e., grafting
length and density), the mechanical properties of the resulting Alg-PHEA
hydrogels could be controlled in a broad range. Remarkably, the hydrogels
were shown to undergo facile degradation and complete dissolution
in physiological conditions, regardless of hydrogel mechanics, by
the expedited hydrolysis through the action of remaining amine groups,
which was also heavily influenced by the graft architecture. Moreover,
the rate of degradation could be further controlled by additional
ionic cross-linking of alginate. The potential application as an injectable
drug delivery system was demonstrated by measuring drug release kinetics
and monitoring degradation ex vivo.
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