Scattering and Absorption Effects in the Determination of Glucose in Whole Blood by Near-Infrared Spectroscopy

Abstract

Optical properties of whole bovine blood are examined under conditions of different glucose loadings. A strong dependency is established between the scattering properties of the whole blood matrix and the concentration of glucose. This dependency is explained in terms of variations in the refractive index mismatch between the scattering bodies (predominately red blood cells) and the surrounding plasma. Measurements in the presence of a well-known glucose transport inhibitor indicate that variations in refractive index mismatch are related to the penetration of glucose into the red blood cells and demonstrate that increased scattering involves the uptake of glucose by red blood cells. Finally, multivariate calibration models are presented for the measurement of glucose in a whole blood matrix. These models are based on near-infrared spectral data collected from 80 different samples prepared from a single whole blood matrix. Calibration studies are performed over the combination, first-overtone, and short-wavelength spectral regions. The best calibration model is generated from combination region spectra, providing a standard error of prediction (SEP) of less than 1 mM over the concentration range of 3-30 mM. The model based on the first-overtone region is slightly degraded but still provides acceptable performance (SEP = 1.20 mM). The model based on the short-wavelength region is further degraded (SEP = 2.53 mM). To rationalize these results, an analysis of the selectivity of the calibration models is performed by computing the glucose net analyte signal. It is established that the models based on the combination and first-overtone regions are dominated by glucose absorption information, while the model computed from the short-wavelength region is based primarily on scattering information. This result provides evidence that absorption information is needed in order to obtain a glucose calibration model with acceptable performance.

Microscale Enzymatic Optical Biosensors Using Mass Transport Limiting Nanofilms. 1. Fabrication and Characterization Using Glucose as a Model Analyte

“…Reported reaction-kinetic simulations of similar systems under physiological conditions show that local oxygen levels within the sensor can be reduced to 10 μM (assuming intradermal oxygen levels of 90 μM) when elevated blood-glucose levels (350 mg/dL) are present. 24,45 To quantify the sensitivity of the overall oxygen-induced quenching response (Q DO ), the following relationship is commonly used: (2) where R N 2 and R O 2 are the PtOEP/RITC peak ratios observed under nitrogen and oxygensaturated conditions, respectively. As expected, Q DO was calculated to be 95%, a sensitivity equivalent to that observed in our previous work on algilica-based dissolved oxygen sensors which did not contain GOx.…”

“…For this work, the detection limit used is the quantification limit, which is defined as the lowest analyte concentration in which there is at least 90% certainty that the analyte is present, and was used to determine if these sensor prototypes could detect the lower limit of the clinically accepted glucose monitoring rage, 40 mg/dL. 47 The quantification limit, C QL , is defined as: (2) where σ baseline is the standard deviation of the baseline (e.g. glucose concentration equal to 0 mg/dL) and S is the response sensitivity defined above.…”

Pulse glucometry: a new approach for noninvasive blood glucose measurement using instantaneous differential near-infrared spectrophotometry

“…The PLS models were assessed by examination of the regression coefficient vectors [9,10,15,18,28] . Presence of positive peaks in the regression coefficients was seen in the spectral regions associated with glucose absorption indicating that these wavelengths have positive correlations to the tissue glucose content.…”

“…Amerov et al [28] show in their in vitro studies of blood that the influence of glucose concentration on scattering is the dominant factor in what they refer to as the short-wavelength region. Their work elegantly shows that, in vitro, the most important mechanism is that of the influence of glucose uptake by blood cells on refractive index.…”

Elliptical optical tweezers for trapping a red blood cell aggregate

“…However, optimal concentrations of OCAs serve to reduce the scattering properties of blood [7], which have been studied extensively both experimentally [8]- [10] and theoretically [11], [12]. In addition, several groups are investigating the optical properties of whole blood [1], [13], [14] as well as RBC aggregates at the whole blood level [3]- [5] and in RBC suspensions [15]. This helps the analysis and understanding of optical measurement results.…”