Noninvasive Glucose Monitoring of the Aqueous Humor of the Eye: Part I. Measurement of Very Small Optical Rotations

Geddes

2004

Analytica Chimica Acta

We describe a new approach for glucose determination with tunable glucose dynamic sensing ranges, dependent on the properties of new nanosensors, which are comprised of Con A-aggregated dextran-coated gold colloids.Dextran-coated 10 or 20 nm gold colloids can be aggregated with Con A in a controlled fashion, the change in absorbance at an arbitrary wavelength used to monitor the extent of aggregation, which can be optimized for sensing. The presence of any glucose competitively binds with Con A, dissociating the dextran-coated colloids, affording for the reverse gold plasmon change and hence the determination of glucose concentrations. For one of our sensor systems, a 500K dextran-20 nm gold sensor, crosslinked with 8.70 M Con A, a change in absorbance at 650 nm of 0.03 was observed, in response to as little as 3 mM glucose. In contrast, a 500K dextran-10 nm gold 18.7 M Con A aggregate sensor, produced a 0.05 and 0.1 change in absorbance, respectively, by the addition of 50 and 100 mM glucose.We have found that the glucose sensing ranges can be somewhat tuned by altering the properties, and therefore the extent of aggregation of the gold aggregate sensors. Reducing the gold colloid size and dextran molecular weight typically reduces the glucose sensing range (lower [glucose]) but also reduces the long-term stability of the gold aggregate sensor. Similarly the concentration of Con A used to aggregate the system also has an effect on long term sensor stability and glucose response.In this paper, we present our findings, which offer unique opportunities and perspectives for building tunable plasmonic type glucose sensors.

Section: Introductionmentioning

confidence: 99%

Tunable plasmonic glucose sensing based on the dissociation of Con A-aggregated dextran-coated gold colloids

Aslan

Geddes

2004

Analytica Chimica Acta

“…The first one is inconvenience and the required compliance by patients, while the second is that this is not a continuous monitoring method. Despite intensive efforts [1][2][3][4][5][6][7][8][9][10][11], no method is currently available for the continuous non-invasive monitoring of blood glucose.…”

Section: Introductionmentioning

confidence: 99%

“…We chose to adopt commonly used plastic contact lenses, 4 for the primary reason that their physiological compatibility has already been assessed and optimised with regard to vision correction, size and oxygen/analyte permeability etc. However, our ongoing 4 The contact lenses were supplied by CIBA Vision, Atlanta, USA, and were stirred in 500 mL water, 20 • C for 24 hr before post-doping. The contact lens is a polyvinyl alcohol type polymer which swells slightly in water.…”

Section: Introductionmentioning

confidence: 99%

A Glucose Sensing Contact Lens: A Non-Invasive Technique for Continuous Physiological Glucose Monitoring

Badugu

Journal of Fluorescence

Geddes

2003

105

We have developed a range of glucose sensing contact lenses, using a daily, disposable contact lens embedded with newly developed boronic acid containing fluorophores. Our findings show that our approach may be suitable for the continuous monitoring of tear glucose levels in the range 50-1000 µM, which typically track blood glucose levels, which are ≈5-10 fold higher. Our non-invasive approach may well offer an alternative solution to current invasive glucose monitoring techniques for diabetes, such as "finger pricking."

Section: Introductionmentioning

confidence: 99%

Saccharide Sensing Using Gold and Silver Nanoparticles-A Review

Aslan

Zhang

Journal of Fluorescence

et al. 2004

132

We review new methodologies for glucose sensing from our laboratories based on the specific biological interactions between Con A, dextran-coated gold nanoparticles and glucose, and the interactions between dextran, glucose, and boronic-acid capped silver nanoparticles in solution. Our new approaches promise new tunable glucose sensing platforms. Dextran-coated gold nanoparticles were aggregated with the addition of Con A resulting in increase an in absorbance of nanoparticles at 650 nm, where the post-addition of glucose caused the dissociation of the aggregates and thus a decrease in the absorbance at 650 nm. The interaction of glucose and dextran with boronic acid-capped silver nanoparticles in solution resulted in enhanced luminescence intensity cumulatively due to surfaceenhanced fluorescence and the decrease in absorbance at 400 nm, with an increase in absorbance at 640 nm. Lifetime measurements were used to distinguish the contribution from the surface-enhanced fluorescence. TEM was employed to assess the aggregation of nanoparticles.