14 research outputs found
Reversible control of current across lipid membranes by local heating
Lipid membranes are almost impermeable for charged molecules and ions that can pass the membrane barrier only with the help of specialized transport proteins. Here, we report how temperature manipulation at the nanoscale can be employed to reversibly control the electrical resistance and the amount of current that flows through a bilayer membrane with pA resolution. For this experiment, heating is achieved by irradiating gold nanoparticles that are attached to the bilayer membrane with laser light at their plasmon resonance frequency. We found that controlling the temperature on the nanoscale renders it possible to reproducibly regulate the current across a phospholipid membrane and the membrane of living cells in absence of any ion channels
Reversible control of current across lipid membranes by local heating
Lipid membranes are almost impermeable for charged molecules and ions that can pass the membrane barrier only with the help of specialized transport proteins. Here, we report how temperature manipulation at the nanoscale can be employed to reversibly control the electrical resistance and the amount of current that flows through a bilayer membrane with pA resolution. For this experiment, heating is achieved by irradiating gold nanoparticles that are attached to the bilayer membrane with laser light at their plasmon resonance frequency. We found that controlling the temperature on the nanoscale renders it possible to reproducibly regulate the current across a phospholipid membrane and the membrane of living cells in absence of any ion channels
Membrane composition of jetted lipid vesicles: A Raman spectroscopy study
Microfluidic jetting is a promising method to produce giant unilamellar phospholipid vesicles for mimicking living cells in biomedical studies. We have investigated the chemical composition of membranes of vesicles prepared using this approach by means of Raman scattering spectroscopy. The membranes of all jetted vesicles are found to contain residuals of the organic solvent decane used in the preparation of the initial planar membrane. The decane inclusions are randomly distributed over the vesicle surface area and vary in thickness from a few to several tens of nanometers. Our findings point out that the membrane properties of jetted vesicles may differ considerably from those of vesicles prepared by other methods and from those of living cells.Fil: Kirchner, Silke R.. Ludwig Maximilians Universitat; AlemaniaFil: Ohlinger, Alexander. Ludwig Maximilians Universitat; AlemaniaFil: Pfeiffer, Tom. Ludwig Maximilians Universitat; AlemaniaFil: Urban, Alexander S.. Ludwig Maximilians Universitat; AlemaniaFil: Stefani, Fernando Daniel. Ludwig Maximilians Universitat; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Centro de Investigaciones en Bionanociencias "Elizabeth Jares Erijman"; ArgentinaFil: Deak, Andras. Ludwig Maximilians Universitat; AlemaniaFil: Lutich, Andrey A.. Ludwig Maximilians Universitat; AlemaniaFil: Feldmann, Jochen. Ludwig Maximilians Universitat; Alemani
Scattering Properties of Individual Hedgehog Particles
“Hedgehog”
particles (HPs) possess a micrometer-sized
dielectric spherical core which is densely coated with nanoscale metal
oxide spikes. This unique surface topography, resembling the appearance
of a hedgehog, provides the particles with the exclusive physiochemical
property to stably disperse in both polar and nonpolar solvents without
the necessity of changing the surface chemistry. Optical extinction
measurements of HP ensembles in aqueous solution indicate a broad
spectral response in the visible range. However, there remains a dearth
of fundamental knowledge about the cause of the broad optical resonance,
as it can be a consequence of shape polydispersity in the many-particle
system or intrinsic to each individual HP. In this paper, we present
the first experimental study of the dark-field scattering of individual
hydrophilic and hydrophobic HPs. Our measurements disclose that the
expansive optical response in the visible spectral range is truly
characteristic for the far-field scattering of a single HP. Our results
also uncover how intrinsic particle features, such as spike length,
as well as environmental changes affect the scattering of individual
HPs. In particular, by changing the atmosphere around a hydrophilic
HP from air to nitrogen and by completely immersing in water by employing
a 3D optical trap, we discovered that the scattering from a hydrophilic
HP is strongly modulated by excess water in its interstitial shell
Snapshot Hyperspectral Imaging (SHI) for Revealing Irreversible and Heterogeneous Plasmonic Processes
Plasmon-mediated
processes provide unique opportunities for selective
photocatalysis, photovoltaics, and electrochemistry. Determining the
influence of particle heterogeneity is an unsolved problem because
often such processes introduce irreversible changes to the nanocatalysts
and/or their surroundings. The challenge lies in monitoring heterogeneous
nonequilibrium dynamics via the slow, serial methods that are intrinsic
to almost all spectral acquisition methods with suitable spatial and/or
spectral resolution. Here, we present a new metrology, snapshot hyperspectral
imaging (SHI), that facilitates in situ readout of the tube lens image
and first-order diffraction image of the dark-field scattering from
many individual plasmonic nanoparticles to extract their respective
spectra simultaneously. Evanescent wave excitation with a supercontinuum
laser enabled signal-to-noise ratios greater than 100 with a time
resolution of only 1 ms. Throughput of ∼100 simultaneous spectra
was achieved with a highly ordered nanoparticle array, yielding a
spectral resolution of 0.21 nm/pixel. Additionally, an alternative
dark-field excitation geometry utilized a combination of a supercontinuum
laser and a reflecting objective for polarization-controlled SHI.
Using a simplified version of SHI, we temporally resolve on the millisecond
time scale the heterogeneous kinetics of an electrochemical surface
redox reaction for many individual gold nanoparticles simultaneously
Spectral Response of Plasmonic Gold Nanoparticles to Capacitive Charging: Morphology Effects
We
report a study of the shape-dependent spectral response of the
gold nanoparticle surface plasmon resonance at various electron densities
to provide mechanistic insight into the role of capacitive charging,
a topic of some debate. We demonstrate a morphology-dependent spectral
response for gold nanoparticles due to capacitive charging using single-particle
spectroscopy in an inert electrochemical environment. A decrease in
plasmon energy and increase in spectral width for gold nanospheres
and nanorods was observed as the electron density was tuned through
a potential window of −0.3 to 0.1 V. The combined observations
could not be explained by existing theories. A new quantum theory
for charging based on the random phase approximation was developed.
Additionally, the redox reaction of gold oxide formation was probed
using single-particle plasmon voltammetry to reproduce the reduction
peak from the bulk cyclic voltammetry. These results deepen our understanding
of the relationship between optical and electronic properties in plasmonic
nanoparticles and provide insight toward their potential applications
in directed electrocatalysis
The complement system drives local inflammatory tissue priming by metabolic reprogramming of articular fibroblasts
Arthritis typically involves recurrence and progressive worsening at specific predilection sites, but the checkpoints between remission and persistence remain unknown. Here, we defined the molecular and cellular mechanisms of this inflammation-mediated tissue priming. Re-exposure to inflammatory stimuli caused aggravated arthritis in rodent models. Tissue priming developed locally and independently of adaptive immunity. Repeatedly stimulated primed synovial fibroblasts (SFs) exhibited enhanced metabolic activity inducing functional changes with intensified migration, invasiveness and osteoclastogenesis. Meanwhile, human SF from patients with established arthritis displayed a similar primed phenotype. Transcriptomic and epigenomic analyses as well as genetic and pharmacological targeting demonstrated that inflammatory tissue priming relies on intracellular complement C3- and C3a receptor-activation and downstream mammalian target of rapamycin- and hypoxia-inducible factor 1α-mediated metabolic SF invigoration that prevents activation-induced senescence, enhances NLRP3 inflammasome activity, and in consequence sensitizes tissue for inflammation. Our study suggests possibilities for therapeutic intervention abrogating tissue priming without immunosuppression