Glucose sensing in human epidermis using mid-infrared photoacoustic detection

Abstract

No reliable non-invasive glucose monitoring devices are currently available. We implemented a mid-infrared (MIR) photoacoustic (PA) setup to track glucose in vitro in deep epidermal layers, which represents a significant step towards non-invasive in vivo glucose measurements using MIR light. An external-cavity quantum-cascade laser (1010–1095 cm−1) and a PA cell of only 78 mm3 volume were employed to monitor glucose in epidermal skin. Skin samples are characterized by a high water content. Such samples investigated with an open-ended PA cell lead to varying conditions in the PA chamber (i.e., change of light absorption or relative humidity) and cause unstable signals. To circumvent variations in relative humidity and possible water condensation, the PA chamber was constantly ventilated by a 10 sccm N2 flow. By bringing the epidermal skin samples in contact with aqueous glucose solutions with different concentrations (i.e., 0.1–10 g/dl), the glucose concentration in the skin sample was varied through passive diffusion. The achieved detection limit for glucose in epidermal skin is 100 mg/dl (SNR=1). Although this lies within the human physiological range (30–500 mg/dl) further improvements are necessary to non-invasively monitor glucose levels of diabetes patients. Furthermore spectra of epidermal tissue with and without glucose content have been recorded with the tunable quantum-cascade laser, indicating that epidermal constituents do not impair glucose detection.

A non-invasive photoacoustic and ultrasonic method for the measurement of glucose solution concentration

“…It overcomes the disadvantage of severe optical absorption in biological materials and can send out acoustic signals in different directions at the same time so that the signals can be detected from any direction (cylindrical wave front). In general, the peak-peak value (PPV) shift of the photoacoustic wave [15][16][17][18][19][20] is taken as the blood glucose index in photoacoustic determination. But the PPV is susceptible to surrounding acoustic and electronic interference, leading to inaccurate measurements.…”

Mid-Infrared Photoacoustic Detection of Glucose in Human Skin: Towards Non-Invasive Diagnostics

“…Numerous attempts have been explored for in vivo glucose measurements. An overview has been given previously [3], differentiating between invasive, non-invasive and minimal invasive techniques. The non-invasive techniques comprise different types of optical (mainly spectroscopic) methods, and non-optical schemes like electromagnetic, ultrasound, or bioimpedance measurements.…”

Nanomolar detection of glucose using SERS substrates fabricated with albumin coated gold nanoparticles

“…Another group designed a low-cost photometer based on metal-waveguide-capillary (MWC) for ultrasensitive detection of Glucose as low as 5.12 nanomolar, in this case, light passed through the photometers and authors detected the optical signals, that in turn, produced a voltage and the amplitude of the voltage signals is related with the concentration of Glucose in the solution 10 . Other techniques have been developed in order to detect Glucose such as: the printing of patterns using gold nanoparticles to create a Glucose sensor 11 , simple inspection of color change in solutions of gold nanoparticles 12 , photoelectrical detection using TiO 2 nanowires with surface-functionalized Glucose oxidase (detection limit 0.9 nM) 13 , and potentiometric methods that associates the electrical conductivity of TiO2-GOx (TiO 2 nanowires with surface-functionalized Glucose oxidase GOx) films with variation of concentrations of Glucose 4 . All those procedures allow the detection of Glucose in the range of micromolar to nanomolar.…”