5 research outputs found
Utilizing a Key Aptamer Structure-Switching Mechanism for the Ultrahigh Frequency Detection of Cocaine
Aptasensing
of small molecules remains a challenge as detection
often requires the use of labels or signal amplification methodologies,
resulting in both difficult-to-prepare sensor platforms and multistep,
complex assays. Furthermore, many aptasensors rely on the binding
mechanism or structural changes associated with target capture by
the aptameric probe, resulting in a detection scheme customized to
each aptamer. It is in this context that we report herein a sensitive
cocaine aptasensor that offers both real-time and label-free measurement
capabilities. Detection relies on the electromagnetic piezoelectric
acoustic sensor (EMPAS) platform. The sensing interface consists of
a <i>S</i>-(11-trichlorosilyl-undecanyl)Âbenzenethiosulfonate
(BTS) adlayer-coated quartz disc onto which a structure-switching
cocaine aptamer (MN6) is immobilized, completing the preparation of
the MN6 cocaine aptasensor (M6CA). The EMPAS system has recently been
employed as the foundation of a cocaine aptasensor based on a structurally
rigid cocaine aptamer variant (MN4), an aptasensor referred to by
analogy as M4CA. M6CA represents a significant increase in terms of
analytical performance, compared to not only M4CA but also other cocaine
aptamer-based sensors that do not rely on signal amplification, producing
an apparent <i>K</i><sub>d</sub> of 27 ± 6 μM
and a 0.3 μM detection limit. Remarkably, the latter is in the
range of that achieved by cocaine aptasensors relying on signal amplification.
Furthermore, M6CA proved to be capable not only of regaining its cocaine-binding
ability via simple buffer flow over the sensing interface (i.e., without
the necessity to implement an additional regeneration step, such as
in the case of M4CA), but also of detecting cocaine in a multicomponent
matrix possessing potentially assay-interfering species. Finally,
through observation of the distinct shape of its response profiles
to cocaine injection, demonstration was made that the EMPAS system
in practice offers the possibility to distinguish between the binding
mechanisms of structure-switching (MN6) vs rigid (MN4) aptameric probes,
an ability that could allow the EMPAS to provide a more universal
aptasensing platform than what is ordinarily observed in the literature
New Functionalizable Alkyltrichlorosilane Surface Modifiers for Biosensor and Biomedical Applications
We report herein three unprecedented alkyltrichlorosilane
surface
modifiers bearing pentafluorophenyl ester (PFP), benzothiosulfonate
(BTS), or novel β-propiolactone (BPL) functionalizable terminal
groups. Evidence is provided that these molecules can be prepared
in very high purity (as assessed by NMR) through a last synthetic
step of Pt-catalyzed alkene hydrosilylation then directly employed,
without further purification, for the surface modification of quartz
and medical grade stainless steel. Subsequent on-surface functionalizations
with amine and thiol model molecules demonstrate the potential of
these molecular adlayers to be important platforms for future applications
in the bioanalytical and biomedical fields
Probing the Hydration of Ultrathin Antifouling Organosilane Adlayers using Neutron Reflectometry
Neutron reflectometry data and modeling
support the existence of
a relatively thick, continuous phase of water stemming from within
an antifouling monoethylene glycol silane adlayer prepared on oxidized
silicon wafers. In contrast, this physically distinct (from bulk)
interphase is much thinner and only interfacial in nature for the
less effective adlayer lacking internal ether oxygen atoms. These
results provide further insight into the link between antifouling
and surface hydration
Prevention of Thrombogenesis from Whole Human Blood on Plastic Polymer by Ultrathin Monoethylene Glycol Silane Adlayer
In
contemporary society, a large percentage of medical equipment coming in contact with blood
is manufactured from plastic polymers. Unfortunately, exposure may
result in undesirable protein–material interactions that can
potentially trigger deleterious biological processes such as thrombosis.
To address this problem, we have developed an ultrathin antithrombogenic
coating based on monoethylene glycol silane surface chemistry. The
strategy is exemplified with polycarbonate–a plastic polymer
increasingly employed in the biomedical industry. The various straightforward
steps of surface modification were characterized with X-ray photoelectron
spectroscopy supplemented by contact angle goniometry. Antithrombogenicity
was assessed after 5 min exposure to whole human blood dispensed at
a shear rate of 1000 s<sup>–1</sup>. Remarkably, platelet adhesion,
aggregation, and thrombus formation on the coated surface was greatly
inhibited (>97% decrease in surface coverage) compared to the bare
substrate and, most importantly, nearly nonexistent
Adlayer-Mediated Antibody Immobilization to Stainless Steel for Potential Application to Endothelial Progenitor Cell Capture
This work describes the straightforward
surface modification of
316L stainless steel with BTS, <i>S</i>-(11-trichlorosilylundecanyl)-benzeneÂthiosulfonate,
a thiol-reactive trichlorosilane cross-linker molecule designed to
form intermediary coatings with subsequent biofunctionalization capability.
The strategy is more specifically exemplified with the immobilization
of intact antibodies and their Fab′ fragments. Both surface
derivatization steps are thoroughly characterized by means of X-ray
photoelectron spectroscopy. The antigen binding capability of both
types of biofunctionalized surfaces is subsequently assessed by fluorescence
microscopy. It was determined that BTS adlayers achieve robust immobilization
of both intact and fragmented antibodies, while preserving antigen
binding activity. Another key finding was the observation that the
Fab′ fragment immobilization strategy would constitute a preferential
option over that involving intact antibodies in the context of <i>in vivo</i> capture of endothelial progenitor cells in stent
applications