Hydrogel gratings with patterned analyte responsive dyes for spectroscopic sensing

This is an unprecedented report of hydrogel gratings with an analyte responsive dye immobilised in alternating strips where the patterned dye is its own dispersive element to perform spectroscopy. At each wavelength, the diffraction efficiency of hydrogel gratings is a function of dye absorbance, which in turn is dependent on the concentration of analytes in samples. Thus, changes in intensity of diffracted light of hydrogel gratings were measured for sensing of analytes. Equally, the ratio of diffracted intensities at two wavelengths was used for quantification of analytes to reduce errors caused by variations in intensity of light sources and photobleaching of dyes. 15.27 μm pitch gratings were fabricated by exposing 175 μm thick films of photofunctionalisable poly(acrylamide) hydrogel in a laser interferometric lithography setup, generating an array of alternating lines with and without free functional groups. The freed functional groups were reacted with pH sensitive fluorescein isothiocyanate to create gratings for measurement of pH. The ratio of intensity of diffracted light of hydrogel gratings at 430 and 475 nm was shown to be linear over 4 pH units, which compares favourably with ∼2 pH units for conventional absorption spectroscopy. This increased dynamic range was a result of cancellation of the opposite non-linearities in the pH response of the analyte responsive dye and the diffraction efficiency as a function of dye absorbance

Dupuytren's Disease: Review of the Current Literature

Dupuytren’s disease is one of the most common condition seen by hand surgeons. It is not only prevalent but can also be a most debilitating condition resulting in significant loss of function of the fingers involved. The cause of this disease, however still remains largely unknown although some recent evidence suggests a stem cell etiology. This review article summarizes the current known knowledge of Dupuytren’s as well as the clinical findings, investigations and treatments available

Disposable electrochemical flow cells for catalytic adsorptive stripping voltammetry (CAdSV) at a bismuth film electrode (BiFE)

Catalytic adsorptive stripping voltammetry (CAdSV) has been demonstrated at a bismuth film electrode (BiFE) in an injection-moulded electrochemical micro-flow cell. The polystyrene three-electrode flow cell was fabricated with electrodes moulded from a conducting grade of polystyrene containing 40% carbon fibre, one of which was precoated with Ag to enable its use as an on-chip Ag/AgCl reference electrode. CAdSV of Co(II) and Ni(II) in the presence of dimethylglyoxime (DMG) with nitrite employed as the catalyst was performed in order to assess the performance of the flow cell with an in-line plated BiFE. The injection-moulded electrodes were found to be suitable substrates for the formation of BiFEs. Key parameters such as the plating solution matrix, plating flow rate, analysis flow rate, solution composition and square-wave parameters have been characterised and optimal conditions selected for successful and rapid analysis of Co(II) and Ni(II) at the ppb level. The analytical response was linear over the range 1 to 20 ppb and deoxygenation of the sample solution was not required. The successful coupling of a microfluidic flow cell with a BiFE, thereby forming a “mercury-free” AdSV flow analysis sensor, shows promise for industrial and in-the-field applications where inexpensive, compact, and robust instrumentation capable of low-volume analysis is required

A method for determining average iron content of ferritin by measuring its optical dispersion

© 2019 American Chemical Society. We report a method where the refractive index increments of an iron storage protein, ferritin, and apoferritin (ferritin minus iron) were measured over the wavelength range of 450-678 nm to determine the average iron content of the protein. The protein used in this study had ∼3375 iron atoms per molecule. The measurement of optical dispersion over the broad wavelength range was enabled by the use of mesoporous leaky waveguides (LWs) made of chitosan. We present a facile approach for fabricating mesoporous chitosan waveguides for improving the measurement sensitivity of macromolecules such as ferritin. Mesoporous materials allow macromolecules to diffuse into the waveguide, maximizing their interaction with the optical mode and thus increasing sensitivity by a factor of ∼9 in comparison to nonporous waveguides. The sensitivity was further improved and selectivity toward ferritin was achieved by the incorporation of antibodies in the waveguide. The method presented in this work is a significant advance over the state of the art method, the enzyme linked immunosorbent assay (ELISA) used in clinics, because it allows determining the average content of ferritin in a single step. The average iron content of ferritin is an important marker for conditions such as injury, inflammation, and infection. Thus, the approach presented here of measuring optical dispersion to determine the average iron content of ferritin has a significant potential to improve the point of care analysis of the protein for disease diagnosis and screening

Biosensor for determining average iron content of ferritin by measuring its optical dispersion

© 2020 SPIE. Average iron content of ferritin has a potential to serve as a biomarker for early identification of high-risk trauma patients at point-of-care (PoC). Appropriate therapies can then be administered to reduce morbidity and mortality. Currently, protein and iron levels are measured separately using enzyme-linked immunosorbent assay (ELISA) and UV or atomic absorption spectroscopy (AAS) respectively, but the use of two completely different methods adds to the complexity and analysis time of the combined measurement. As a result, these methods are unsuitable for PoC analysis. To address this gap, we report a biosensor for measuring the average iron content of ferritin in a single step. The biosensor was based on a dye-doped leaky waveguide (LW), which operates in the entire visible wavelength range, and hence allowed the measurement of differences in the optical dispersion of ferritin and apoferritin to determine the average iron content of the protein. The LW biosensor comprised a 1.54 micron thick mesoporous chitosan slab waveguide with immobilized antibodies against ferritin/apoferritin to measure the optical dispersion of 110 nM protein. Based on the baseline noise, the limit of detection for this method is ∼700 pM for ferritin/apoferritin. The biosensor has a significant potential for PoC measurement of the average iron content of serum ferritin and, in future, the total protein cencentration