2 research outputs found
Active Control of SPR by Thermoresponsive Hydrogels for Biosensor Applications
The use of thermoresponsive poly(<i>N</i>-isopropylacrylamide)-based
hydrogel (pNIPAAm) for rapid tuning of surface plasmon resonance (SPR)
is reported. This approach is implemented by using an SPR layer architecture
with an embedded indium tin oxide microheater and pNIPAAm film on
its top. It takes advantage of rapid thermally induced swelling and
collapse of pNIPAAm that is accompanied by large refractive index
changes and leads to high thermo-optical coefficient of d<i>n</i>/d<i>T</i> = 2 × 10<sup>–2</sup> RIU/K. We
show that this material is excellently suited for efficient control
of refractive index-sensitive SPR and that it can serve simultaneously
as a 3D binding matrix in biosensor applications (if modified with
biomolecular recognition elements for a specific capture of target
analyte). We demonstrate that this approach enables modulating of
the output signal in surface plasmon-enhanced fluorescence spectroscopy
biosensors and holds potential for simple time-multiplexing of sensing
channels for parallelized readout of fluorescence assays
Simultaneous Measurement of Mechanical and Surface Properties in Thermoresponsive, Anchored Hydrogel Films
Hydrogel films have been used extensively in the preparation
of
biosensors and biomedical devices. The characteristics of the aqueous
interface of the polymer layer are significant for the biosensor or
device function; likewise, the changing mechanical properties of thermoresponsive
polymers are an important feature that affects the polymer behavior.
Atomic force microscopy was used here to characterize both the surface
and the mechanical properties of polymeric hydrogel films prepared
from a thermoresponsive terpolymer of <i>N</i>-isopropylacrylamide
and acrylic acid with benzophenonemethacrylate as a photoreactive
cross-linker comonomer. The force–distance curves thus obtained
were analyzed to assess both the surface forces and the mechanical
response that were associated with the hydrogel. These properties
were investigated as a function of temperature, in water and in Tris
buffer, for different degrees of polymer cross-linking. For samples
in water, the distance over which the surface forces were effective
was found to remain constant as the temperature was increased from
26 to 42 °C, even though the mechanical response indicated that
the samples had been heated past the lower critical solution temperature,
or LCST. The bulk of the polymer becomes less soluble above the LCST,
although this does not seem to affect the surface properties. This
may be due to the segregation of the acrylic acid-rich polymer segments
near the gel surface, which is in agreement with reports for related
systems