Table 2.
Comparison of Various Glucose Sensing Technologies, Grouped According to Their Transduction Mechanism.
| Detection Technology | Merits | Drawbacks | ||
|---|---|---|---|---|
| Electrochemical | Enzymatic | First generation | 1. Highly specific to glucose | 1. Interferences from co-substrate (i.e., oxygen) and endogenous species |
| 2. High sensor sensitivity | 2. High operating potential required | |||
| 3. Must use outer membranes, which increase sensor response times | ||||
| Second generation | 1. Highly specific to glucose and free of changes in levels of co-substrate | 1. Mediators used may be toxic | ||
| 2. Low overpotential renders the sensor free of interferences | 2. Competition between mediators and oxygen still exists | |||
| Third generation | 1. Highly specific to glucose and free of changes in the level of co-substrate | 1. Toxicity and biocompatibility of required nanomaterials is untested | ||
| 2. Low overpotential renders the sensor free from interferences | 2. The issue of repeatability is still untested | |||
| Non-GOx based | 1. Does not use oxygen as co-substrate and so no interferences from oxygen | 1. Shown to oxidize other sugars as well as common alcohols | ||
| Nonenzymatic | 1. No enzymes used and so no question of degradation | 1. Not specific to glucose | ||
| 2. Substantial electrode fouling by the products of glucose oxidation | ||||
| Optical | Fluorophore-based | Fluorescence or FRET intensity | 1. Highly specific to glucose because of the use of fluorophore with binding specificity to glucose | 1. Photobleaching of the fluorophore and scattering in tissue |
| 2. Dependent on skin pigmentation, redness, epidermal thickness | ||||
| FRET lifetime | 1. Independent of scattering in tissue | 1. Miniaturization of photodetectors and time resolved spectrometers is not trivial | ||
| 2. Independent of fluorophore concentration and so no issue of photobleaching or fluorophore loss through leaching | 2. Fool-proof demonstration in animals and humans is yet to be demonstrated | |||
| Ocular spectroscopy | 1. Truly noninvasive since it measures glucose concentration in tears | 1. Leaching of boronic acid derivative | ||
| 2. No handheld instruments | 2. Effected by pH and ionic strength | |||
| 3. Glucose levels can be assessed visually | 3. When used in tears, a lag between the blood and tear glucose is observed | |||
| Nonfluorophore based | Optical coherence tomography | 1. Unlike other optical techniques, it is not affected by urea, ionic strength, temperature, heart rate, and hematocrit | 1. Shown to be affected by motion and tissue heterogeneity | |
| Polarimetry | 1. Can utilize visible light, easily available | 1. Effected by scattering in the tissue, pH, and temperature | ||
| 2. All the components can be easily miniaturized | 2. Lack of specificity as molecules such as albumin and ascorbic acid are known to polarize light | |||
| Thermal infrared spectroscopy | 1. Same as polarimetry | 1. Effected by scattering in the tissue, pH, probe position, fever, and temperature | ||
| Photoacoustic spectroscopy | 1. Unlike other optical techniques, it is not affected by ionic strength or albumins | 1. Effected by scattering in the tissue | ||
| 2. Miniaturization of instrument is not trivial | ||||
| Raman spectroscopy | 1. Unlike NIR, it shows sharper peaks and less overlap | 1. Longer stabilization times | ||
| 2. No interference from luminescence and fluorescence | 2. Effected by tissue density, thickness, hematocrit | |||
| Combinatorial | Impedance spectroscopy | 1. Can measure glucose levels in the vascular compartment, so no lag time in sensor response | 1. Temperature and disease state of the body may affect measurements | |
| 2. Changes in blood dielectric properties are not specific to glucose | ||||
| Electromagnetic spectroscopy | 1. Same as impedance spectroscopy | 1. Body temperature, sweating, and motion affect glucose measurements | ||