Hemoglobin-Laden Microcapsules for Simulating Oxygen Dynamics of Biological Tissue

We propose one-step synthesis of hemoglobin-laden microcapsules (HbMs) by the liquid-driven coaxial flow focusing (LDCFF) method, in which purified hemoglobin (Hb) is fully encapsulated inside photocurable resin with a solid core-shell structure. The polymeric shell constitutes a rigid semipermeable membrane which prevents the leakage of Hb and allows oxygen transport. Gas-binding capacity and oxygen affinity of HbMs are comparable to the purified Hb. Solid HbMs phantoms (SHMPs) are also fabricated using resin-based HbMs homogeneously mixed with oil-soluble silicone. The spectral characteristics of SHMPs closely resemble to that of oxy-hemoglobin, and its long-term stability is more than 25 weeks. HbM dispersion with certain absorption and scattering properties circulating through the dialysis tube simulates tissue oxygen dynamics compared with the post occlusive reactive hyperemia (PORH) test on the healthy volunteer. The occlusion test indicates that HbMs dispersion solution can substitute conventional blood phantom. Our studies have shown that microencapsulation of Hb effectively protects it from the external environment, which makes HbMs promising for optical tissue-simulating phantom in biomedical fields.