Function of Hemoglobin-Based Oxygen Carriers: Determination of Methemoglobin Content by Spectral Extinction Measurements

Abstract

Suspensions of hemoglobin microparticles (HbMPs) are promising tools as oxygen therapeutics. For the approval of clinical studies extensive characterization of these HbMPs with a size of about 750 nm is required regarding physical properties, function, pharmaco-kinetics and toxicology. The standard absorbance measurements in blood gas analyzers require dissolution of red blood cells which does not work for HbMP. Therefore, we have developed a robust and rapid optical method for the quality and functionality control of HbMPs. It allows simultaneous determination of the portion of the two states of hemoglobin oxygenated hemoglobin (oxyHb) and deoxygenated hemoglobin (deoxyHb) as well as the content of methemoglobin (metHb). Based on the measurement of collimated transmission spectra between 300 nm and 800 nm, the average extinction cross section of HbMPs is derived. A numerical method is applied to determine the composition of the HbMPs based on their wavelength-dependent refractive index (RI), which is a superposition of the three different states of Hb. Thus, light-scattering properties, including extinction cross sections can be simulated for different compositions and sizes. By comparison to measured spectra, the relative concentrations of oxyHb, deoxyHb, metHb are accessible. For validation of the optically determined composition of the HbMPs, we used X-ray fluorescence spectrometry for the ratio of Fe(II) (oxyHb/deoxyHb) and Fe(III) (metHb). High accuracy density measurements served to access heme-free proteins, size was determined by dynamic light scattering and analytical centrifugation and the shape of the HbMPs was visualized by electron and atomic force microscopy.

Effects of Different Feed Additives on Intestinal Metabolite Composition of Weaned Piglets

“…The Tib group of weaned piglets exhibited significantly higher leukocyte counts than the Nor group on the 21st day of the test ( p < 0.01). Furthermore, higher hemoglobin levels contribute to enhanced oxygen transport, immune ability, and metabolic function [ 31 , 32 , 33 ]. Clinically, higher hemoglobin levels have been associated with improved body resistance [ 34 ].…”

Effects of Lincomycin and Faecal Bacterial Stress on Intestinal Metabolite Composition of Weaned Tibetan Piglets

“…Furthermore, higher hemoglobin levels contribute to enhanced oxygen transport, immune ability, and metabolic function [30][31][32] . Clinically, higher hemoglobin levels have been associated with improved body resistance [33] . In this experiment, the Tib group had significantly higher hemoglobin (HGB) levels than the Nor group (P < 0.05), which indicates an enhancement in the immune ability of weaned piglets.…”

Pulse Oximetry Imaging System Using Spatially Uniform Dual Wavelength Illumination

“…The specific absorption coefficients of oxygenated (HbO 2 ) and deoxygenated hemoglobin (Hb) have distinct spectral dependence [ 32 ], as included in Figure 1 e. The difference between these coefficients allows for the quantification of each constituent, forming the basis of pulse oximetry [ 33 , 34 ]. At wavelengths below 800 nm, the Hb-specific absorption coefficients are higher than the HbO 2 one, while in the region above 800 nm, the HbO 2 absorptions dominate.…”