6 research outputs found
Carbon-Binding Designer Proteins that Discriminate between sp<sup>2</sup>- and sp<sup>3</sup>‑Hybridized Carbon Surfaces
Robust and simple strategies to directly
functionalize graphene-
and diamond-based nanostructures with proteins are of considerable
interest for biologically-driven manufacturing, biosensing, and bioimaging.
Here, we identify a new set of carbon-binding peptides that vary in
overall hydrophobicity and charge and engineer two of these sequences
(Car9 and Car15) within the framework of <i>E. coli</i> thioredoxin
1 (TrxA). We develop purification schemes to recover the resulting
TrxA derivatives in a soluble form and conduct a detailed analysis
of the mechanisms that underpin the interaction of the fusion proteins
with carbonaceous surfaces. Although equilibrium quartz crystal microbalance
measurements show that TrxA::Car9 and TrxA::Car15 have similar affinities
for sp<sup>2</sup>-hybridized graphitic carbon (<i>K</i><sub>d</sub> = 50 and 90 nM, respectively), only the latter protein
is capable of dispersing carbon nanotubes. Further investigation by
surface plasmon resonance and atomic force microscopy reveals that
TrxA::Car15 interacts with sp<sup>2</sup>-bonded carbon through a
combination of hydrophobic and π–π interactions
but that TrxA::Car9 exhibits a cooperative mode of binding that relies
on a combination of electrostatics and weaker π stacking. Consequently,
we find that TrxA::Car9 binds equally well to sp<sup>2</sup>- and
sp<sup>3</sup>-bonded (diamondlike) carbon particles whereas TrxA::Car15
is capable of discriminating between the two carbon allotropes. Our
results emphasize the importance of understanding both bulk and molecular
recognition events when exploiting the adhesive properties of solid-binding
peptides and proteins in technological applications
Measuring Proton Currents of Bioinspired Materials with Metallic Contacts
Charge
transfer at the interface between the active layer and the contact
is essential in any device. Transfer of electronic charges across
the contact/active layer interface with metal contacts is well-understood.
To this end, noble metals, such as gold or platinum, are widely used.
With these contacts, ionic currents (especially protonic) are often
neglected because ions and protons do not transfer across the interface
between the contact and the active layer. Palladium hydride contacts
have emerged as good contacts to measure proton currents because of
a reversible redox reaction at the interface and subsequent absorption/desorption
of H into palladium, translating the proton flow reaching the interface
into an electron flow at the outer circuit. Here, we demonstrate that
gold and palladium contacts also collect proton currents, especially
under high relative humidity conditions because of electrochemical
reactions at the interface. A marked kinetic isotope effect, which
is a signature of proton currents, is observed with gold and palladium
contacts, indicating both bulk and contact processes involving proton
transfer. These phenomena are attributed to electrochemical processes
involving water splitting at the interface. In addition to promoting
charge transfer at the interface, these interfacial electrochemical
processes inject charge carriers into the active layer and hence can
also modulate the bulk resistivity of the materials, as was found
for the studied peptide fibril films. We conclude that proton currents
may not be neglected a priori when performing electronic measurements
on biological and bioinspired materials with gold and palladium contacts
under high humidity conditions
Delivery of Cargo with a Bioelectronic Trigger
Biological systems
exchange information often with chemical signals. Here, we demonstrate
the chemical delivery of a fluorescent label using a bioelectronic
trigger. Acid-sensitive microparticles release fluorescin diacetate
upon low pH induced by a bioelectronic device. Cardiac fibroblast
cells (CFs) uptake fluorescin diacetate, which transforms into fluorescein
and emits a fluorescent signal. This proof-of-concept bioelectronic
triggered delivery may be used in the future for real-time programming
and control of cells and cell systems
DataSheet1_Deep learning classification for macrophage subtypes through cell migratory pattern analysis.pdf
Macrophages can exhibit pro-inflammatory or pro-reparatory functions, contingent upon their specific activation state. This dynamic behavior empowers macrophages to engage in immune reactions and contribute to tissue homeostasis. Understanding the intricate interplay between macrophage motility and activation status provides valuable insights into the complex mechanisms that govern their diverse functions. In a recent study, we developed a classification method based on morphology, which demonstrated that movement characteristics, including speed and displacement, can serve as distinguishing factors for macrophage subtypes. In this study, we develop a deep learning model to explore the potential of classifying macrophage subtypes based solely on raw trajectory patterns. The classification model relies on the time series of x-y coordinates, as well as the distance traveled and net displacement. We begin by investigating the migratory patterns of macrophages to gain a deeper understanding of their behavior. Although this analysis does not directly inform the deep learning model, it serves to highlight the intricate and distinct dynamics exhibited by different macrophage subtypes, which cannot be easily captured by a finite set of motility metrics. Our study uses cell trajectories to classify three macrophage subtypes: M0, M1, and M2. This advancement holds promising implications for the future, as it suggests the possibility of identifying macrophage subtypes without relying on shape analysis. Consequently, it could potentially eliminate the necessity for high-quality imaging techniques and provide more robust methods for analyzing inherently blurry images.</p
Protonic and Electronic Transport in Hydrated Thin Films of the Pigment Eumelanin
The
electrical properties of eumelanin, a ubiquitous natural pigment,
have fascinated scientists since the late 1960s. For several decades,
the hydration-dependent electrical properties of eumelanin have mainly
been interpreted within the amorphous semiconductor model. Recent
works undermined this paradigm. Here we study protonic and electronic
charge carrier transport in hydrated eumelanin in thin film form.
Thin films are ideal candidates for these studies since they are readily
accessible to chemical and morphological characterization and potentially
amenable to device applications. Current–voltage (<i>I</i>-<i>V</i>) measurements, transient current measurements
with proton-transparent electrodes, and electrochemical impedance
spectroscopy (EIS) measurements are reported and correlated with the
results of the chemical characterization of the films, performed by
X-ray photoelectron spectroscopy. We show that the electrical response
of hydrated eumelanin films is dominated by ionic conduction (10<sup>–4</sup>–10<sup>–3</sup> S cm<sup>–1</sup>), largely attributable to protons, and electrochemical processes.
To propose an explanation for the electrical response of hydrated
eumelanin films as observed by EIS and <i>I</i>-<i>V</i>, we considered the interplay of proton migration, redox
processes, and electronic transport. These new insights improve the
current understanding of the charge carrier transport properties of
eumelanin opening the possibility to assess the potential of eumelanin
for organic bioelectronic applications, e.g. protonic devices and
implantable electrodes, and to advance the knowledge on the functions
of eumelanin in biological systems
Proton Conduction in Tröger’s Base-Linked Poly(crown ether)s
Exactly 50 years
ago, the ground-breaking discovery of dibenzo[18]Âcrown-6 (DB18C6)
by Charles Pedersen led to the use of DB18C6 as a receptor in supramolecular
chemistry and a host in host–guest chemistry. We have demonstrated
proton conductivity in Tröger’s base-linked polymers
through hydrogen-bonded networks formed from adsorbed water molecules
on the oxygen atoms of DB18C6 under humid conditions. Tröger’s
base-linked polymersî—¸polyÂ(TBL-DB18C6)-<i>t</i> and
polyÂ(TBL-DB18C6)-<i>c</i>î—¸synthesized by the in situ
alkylation and cyclization of either <i>trans</i>- or <i>cis</i>-diÂ(aminobenzo) [18]Âcrown-6 at room temperature have
been isolated as high-molecular-weight polymers. The macromolecular
structures of the isomeric polyÂ(TBL-DB18C6)Âs have been established
by spectroscopic techniques and size-exclusion chromatography. The
excellent solubility of these polymers in chloroform allows the formation
of freestanding membranes, which are thermally stable and also show
stability under aqueous conditions. The hydrophilic nature of the
DB18C6 building blocks in the polymer facilitates retention of water
as confirmed by water vapor adsorption isotherms, which show a 23
wt % water uptake. The adsorbed water is retained even after reducing
the relative humidity to 25%. The proton conductivity of polyÂ(TBL-DB18C6)-<i>t</i>, which is found to be 1.4 × 10<sup>–4</sup> mS cm<sup>–1</sup> in a humid environment, arises from the
hydrogen bonding and the associated proton-hopping mechanism, as supported
by a modeling study. In addition to proton conductivity, the Tröger’s
base-linked polymers reported here promise a wide range of applications
where the sub-nanometer-sized cavities of the crown ethers and the
robust film-forming ability are the governing factors in dictating
their properties