Extended X-ray Absorption Fine Structure Calibrated Hemoglobin-Bound Iron Fraction via Blood Thin Films Rapidly Solidified From 100µL Drops

Measuring the fraction of Iron bound to Hemoglobin in whole blood can detect anemia. But state-of-the-art Blood diagnostics via High Performance Liquid Chromatography (HPLC) use large blood volumes (8-10 mL) leading to Hospital Acquired Anemia in 74% of patients.

In this work, small volume blood drops are rapidly solidified via Hyper-hydrophilic coatings [2] to yield flat, Homogeneous Thin Solid Films (HTSFs) in min. without coagulation. X-ray Fluorescence (XRF) and Ion Beam Analysis [2] yield Fe composition within ± 10% on HTSF.

Extended X-ray Absorption Fine Structure (EXAFS) can be used since solidifying blood into HTSFs does not modify Fe bonding.

Hemoglobin is a globular protein, folded into a spherical shape with four heme groups, each with an Fe bound to a histidine residue via N. Fe is bound to four N nearest neighbors within a plane, with a 5^th nearest neighbor and a 6^th N atom. Prior EXAFS on hemoglobin detected oxidized Fe, matching HPLC [1]. In this work, EXAFS at the Canadian Light Source uses fluorescence near the Fe absorption edge (7.126 -7.8 keV). Spectra on whole blood HTSF match [1] with a Fe-N bond length of 1.97±0.02 Å [1].

[1] Z. Wu et al.. (2001) Phys. Med. Biol, 46(71)

[2] Herbots, N., et al. (2019). MRS Adv.,4(46-47), 2489-2513. doi:10.1557/adv.2019.398