Synthesis and Physicochemical Properties of Poly(2-Alkyl-2-Oxazoline)-Conjugated Hemoglobins as an Artificial O2 Carrier: Comparison with Polyethylene Glycol Conjugates

Abstract

Polyethylene glycol (PEG) is a biocompatible polymer extensively employed to prolong blood circulation and mitigate the immunogenicity of the protein therapeutics. Nonetheless, there are reports of anti-PEG antibody production. Poly(2-alkyl-2-oxazoline) (PROx) exhibits analogous immunological stealth properties and represents a potential substitute for PEG. This study details the synthesis of PROx-conjugated hemoglobins (PROx_m-Hbs, R = Me, Et) as artificial O₂ carriers, functioning as red blood cell (RBC) substitutes, and evaluates their O₂ affinities and solution properties. The average number of polymers bound is designed to be 6 or 11. The O₂ affinities (P₅₀) of PMeOx_m-Hbs and PEtOx_m-Hbs are ascertained as 9 Torr, comparable to those of PEG-conjugated Hbs (PEG_m-Hbs). The PEtOx₆-Hb^T, synthesized under an N₂ atmosphere, exhibited a low O₂ affinity (P₅₀ = 57 Torr). Through the admixture of PEtOx₆-Hb and PEtOx₆-Hb^T, the P₅₀ value of the formulation to range from 9 to 57 Tor can be tailored as desired. The colloid osmotic pressures and viscosities of PMeOx_m-Hb and PEtOx_m-Hb solutions are lower than those of the corresponding PEG_m-Hb solutions. Furthermore, the PROx conjugates evinced no cytotoxicity against normal cells. PMeOx_m-Hbs and PEtOx_m-Hbs, characterized by their appropriate O₂ affinities and solution properties, present themselves as promising alternative materials to RBCs.