Physicochemical Properties and O₂-Coordination Structure of Human Serum Albumin Incorporating Tetrakis(o-pivalamido)phenylporphyrinatoiron(II) Derivatives

Abstract

Incorporation of tetrakis(o-pivalamido)phenylporphyrinatoiron(II) derivatives with a covalently linked axial imidazole (FeP) into human serum albumin (HSA) provides a new type of artificial hemoprotein (HSA-FeP) that binds and releases dioxygen reversibly under physiological conditions (in aqueous media, pH 7.4, 37 degreesC) and in a fashion similar to hemoglobin and myoglobin. The HSA host adsorbs a maximal eight FeP molecules, and their stepwise equilibrium constants (K1-K8) range from 1.2 x 10(6) to 1.3 x 10(4) M-1. The major binding sites of the synthetic hemes are identical to those of hemin, bilirubin, and long-chain fatty acids. The red-colored solution of HSA-FeP was stored for three months at 4 degreesC and could be kept as a freeze-dried powder for more than six months. The solution properties [[HSA]: 5 wt %, FeP/HSA = 1-8 (mol/mol)] satisfy the physiological requirements for dioxygen infusion for potential clinical use; the specific gravity is 1.013, and the viscosity is 1.1 cP. Mixing the solution with human blood does not induce any coagulation and precipitation. On the basis of the gel permeation chromatography, CD spectroscopy, and IEF measurements, the molecular size, second-order structure, and surface charge distribution of the HSA-FeP conjugate are constant and independent of the binding numbers of heme molecules. Furthermore, the O2-coordination structure of FeP embedded into certain hydrophobic domains of the albumin was confirmed by resonance Raman spectroscopy.

Superior Plasma Retention of a Cross-Linked Human Serum Albumin Dimer in Nephrotic Rats as a New Type of Plasma Expander

“…Tsuchida et al (1997) previously reported on an HSA-based artificial oxygen carrier "albumin-heme (HSA-FeP)," which is a synthetic heme with a covalently bound proximal base that is incorporated into the hydrophobic cavities of HSA. HSA-FeP reversibly binds and releases O 2 under physiological conditions, the same as hemoglobin (Komatsu et al, 1999). An in vivo study using hemorrhagic shocked rats revealed that the renal cortical O 2 -tensions and skeletal tissue O 2 -tensions were increased when HSA-FeP was injected (Tsuchida et al, 2000;Komatsu et al, 2004b).…”

Exchange transfusion with entirely synthetic red‐cell substitute albumin‐heme into rats: Physiological responses and blood biochemical tests

“…[1][2][3][4] Recombinant human serum albumin (rHSA) incorporating the synthetic heme albumin-heme is an artificial hemoprotein that has the potential to bind and release O 2 under physiological conditions in the same manner as Hb and myoglobin. [5][6][7] In fact, the albumin-heme can transport O 2 through the body and release O 2 to tissues as a red-cell substitute without any acute side effects. 8,9 For example, rHSA including four molecules of 2-[8-{N-(2-methylimidazolyl)}-octanoyloxymethyl]-5,10,15,20-[tetrakis{␣,␣,␣,␣-o-(1-methylcyclohexanoyl)amino}phenyl]porphinatoiron(II) (Scheme 1) is one of the promising materials.…”

Compatibility in vitro of albumin‐heme (O2 carrier) with blood cell components

“…3 Its physicochemical properties and O 2 -transporting ability satisfy the initial clinical requirements as an artificial red blood cell: [3][4][5][6][7][8] (1) A maximum of eight FeP molecules were incorporated into certain domains of rHSA by hydrophobic interaction. [3][4][5] The incorporation of FeP does not induce any changes in the highly ordered structure and surface charge distribution of the host albumin. (2) The red-colored rHSA-FeP solution has a long shelf-life of over 1 year, at temperatures of 5°-40°C.…”

“…7 Although the Hill coefficient is 1.0, the O 2 -transporting efficiency (22%) between the lungs (Po 2 : 110 Torr) and the muscle tissues (Po 2 : 40 Torr) is similar to that of human blood (23%). [3][4][5]7 (4) In contrast to the fact that the intravenous administration of Hb-based O 2 carriers often elicits an acute increase in blood pressure by vasoconstriction, which is due to the depletion of nitric oxide (endothelial-derived relaxing factor) by To use this albumin-based O 2 carrier for clinical applications, it is necessary to evaluate its biocompatibility with blood under physiological conditions. We report herein for the first time the detailed inspections of the compatibility of rHSA-FeP with blood cell components in vitro.…”