Direct chemical sensing in liquid environments using
polymer-guided shear horizontal surface acoustic wave
sensor platforms on 36° rotated Y-cut LiTaO3 is investigated. Design considerations for optimizing these devices
for liquid-phase detection are systematically explored.
Two different sensor geometries are experimentally and
theoretically analyzed. Dual delay line devices are used
with a reference line coated with poly (methyl methacrylate) (PMMA) and a sensing line coated with a chemically
sensitive polymer, which acts as both a guiding layer and
a sensing layer or with a PMMA waveguide and a chemically sensitive polymer. Results show the three-layer
model provides higher sensitivity than the four-layer
model. Contributions from mass loading and coating
viscoelasticity changes to the sensor response are evaluated, taking into account the added mass, swelling, and
plasticization. Chemically sensitive polymers are investigated in the detection of low concentrations (1−60 ppm)
of toluene, ethylbenzene, and xylenes in water. A low-ppb
level detection limit is estimated from the present experimental measurements. Sensor properties are investigated
by varying the sensor geometries, coating thickness
combinations, coating properties, and curing temperature
for operation in liquid environments. Partition coefficients
for polymer−aqueous analyte pairs are used to explain
the observed trend in sensitivity for the polymers PMMA,
poly(isobutylene), poly(epichlorohydrin), and poly(ethyl
acrylate) used in this work.
Attenuated total internal reflectance Fourier transform infrared (ATR-FTIR) spectroscopy was used for the investigation of sorption of aqueous solutions of analytes into polymer coatings. A series of simple model polymers: poly(dimethylsiloxane) (PDMS), poly(epichlorhydrin) (PECH), and poly(isobutylene) (PIB) films and analytes: aqueous solutions of ethylbenzene, xylenes, toluene, and nitrobenzene were used to evaluate the use of ATR-FTIR spectroscopy as a screening tool for sensor development. The ratios of integrated infrared absorption bands provided a simple and efficient method for predicting trends in partition coefficients. Responses of polymer-coated guided shear horizontal surface acoustic wave (SH-SAW) sensor platforms to the series of analytes, using polymer coatings with similar viscoelastic properties, were consistent with ATR-FTIR predictions. Guided SH-SAW sensor responses were linear in all cases with respect to analyte concentration in the tested range. Comparison of ATR-FTIR data with guided SH-SAW sensor data identifies cases where mass loading is not the dominant contribution to the response of the acoustic wave sensor. ATR-FTIR spectra of nitrobenzene, coupled with computational chemistry, provided additional insight into analyte/polymer interactions.
For several decades, cancer has been
one of the most life-threatening
diseases. For enhancing anticancer efficiency with minimum side effects,
combination therapy is envisioned. The current manuscript reports
for the first time the development of a methylene blue (MB) bound
nanoplatform, which is capable of delivering targeted diagnostic and
combined synergistic photothermal and photodynamic treatment of cancer.
Experimental data found that, once the nanoparticle binds with the
target cell surface, it can detect LNCaP human prostate cancer cell
selectively using fluorescence imaging. Our result shows that the
therapeutic actions can be controlled with external NIR light. No
cytotoxicity was observed in the absence of NIR light. Targeted photodynamic
and photothermal treatment using 785 nm NIR light indicates that the
multimodal treatment enhances the possibility of destroying LNCaP
prostate cancer cells in vitro dramatically. We discuss the operating
principle for the targeted imaging and possible mechanisms for combined
therapeutic actions. Our experimental data show that NIR light activated
combined therapy for cancer may become a highly effective treatment
procedure in clinical settings.
In this article, we demonstrate the use of bio-conjugated 2D graphene oxide (bio-GO) nanostructure to probe breast cancer cell (SKBR3) with excellent discrimination over other types of circulating tumor cells. We distinctly observed that bio-GO nanostructure targets and bind SKBR3 cell selectively in the cell mixture. Longer incubation of SKBR3 cell with bio-GO causes Raman signal “turn off” when excited with 532 nm laser. This is attributed to penetration of the bio-GO through the plasma membrane of the cell by generating transient hole. Extraction of GO after cell digestion also support the internalization rubric of 2D graphene through cell membrane. Our experimental data with the HaCaT healthy cell line, as well as with LNCaP prostate cancer cell line clearly demonstrated that this Raman scattering assay is highly selective to SKBR3. The mechanism of selectivity and the assay’s response change have been verified and discussed utilizing fluorescence properties of GO and various other techniques. The experimental results open up a possibility of new label free Raman scattering assay, for reliable diagnosis of cancer cell lines by monitoring “turn-off” of the Raman signal from Bio-GO nanostructure.
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