2 research outputs found
Groepsgedrag op de nanoschaal
Monodisperse gas microbubbles, encapsulated with a shell
of photopolymerizable
diacetylene lipids and phospholipids, were produced by microfluidic
flow focusing, for use as ultrasound contrast agents. The stability
of the polymerized shell microbubbles against both aggregation and
gas dissolution under physiological conditions was studied. Polyethylene
glycol (PEG) 5000, which was attached to the diacetylene lipids, was
predicted by molecular theory to provide more steric hindrance against
aggregation than PEG 2000, and this was confirmed experimentally.
The polymerized shell microbubbles were found to have higher shell-resistance
than nonpolymerizable shell microbubbles and commercially available
microbubbles (Vevo MicroMarker). The acoustic stability under 7.5
MHz ultrasound insonation was significantly greater than that for
the two comparison microbubbles. The acoustic stability was tunable
by varying the amount of diacetylene lipid. Thus, our polymerized
shell microbubbles are a promising platform for ultrasound contrast
agents
A Mass-Tagging Approach for Enhanced Sensitivity of Dynamic Cytokine Detection Using a Label-Free Biosensor
Monitoring
cytokine release by cells allows the investigation of
cellular response to specific external stimuli, such as pathogens
or candidate drugs. Unlike conventional colorimetric techniques, label-free
detection of cytokines enables studying cellular secretions in real
time by eliminating additional wash and labeling steps after the binding
step. However, label-free techniques that are based on measuring mass
accumulation on a sensor surface are challenging for measuring small
cytokines binding to much larger capture agents (usually antibodies)
because the relative signal change is small. This problem is exacerbated
when the capturing antibodies desorb from the surface, a phenomenon
that almost inevitably occurs in immunoassays but is rarely accounted
for. Here, we demonstrate a quantitative dynamic detection of interleukine-6
(IL-6), a pro-inflammatory cytokine, using an interferometric reflectance
imaging sensor (IRIS). We improved the accuracy of the quantitative
analysis of this relatively small protein (21 kDa) by characterizing
the antibody desorption rate and compensating for the antibody loss
during the binding experiment. By correcting for protein desorption,
we achieved an analytical limit of detection at 19 ng/mL IL-6 concentration.
We enhanced the sensitivity by 7-fold by using detection antibodies
that recognize a different epitope of the cytokine. We demonstrate
that these detection antibodies, which we call “mass tags”,
can be used concurrently with the target analyte to eliminate an additional
wash and binding step. Finally, we report successful label-free detection
of IL-6 in cell culture medium (with 10% serum) with comparable signal
to that obtained in PBS. This work is the first to report quantitative
dynamic label-free detection of small protein in a complex biological
fluid using IRIS