# Redox Potential of Hemoglobin Sub-Micron Particles and Impact of Layer-by-Layer Coating

## TL;DR

Researchers studied how hemoglobin particles and their biopolymer coatings affect oxygen delivery and stability in artificial blood substitutes.

## Contribution

The study shows that layer-by-layer biopolymer coatings do not alter the redox properties of hemoglobin particles.

## Key findings

- The redox potential of hemoglobin particles and coated particles shifted slightly compared to free hemoglobin.
- Hemoglobin particles can undergo multiple oxidation-reduction cycles without degradation.
- Coating does not impact the redox behavior of hemoglobin particles, suggesting long-term stability.

## Abstract

The search for artificial blood substitutes that are suitable for safe transfusion in clinical conditions and in extreme situations has gained increasing interest during recent years. Most of the problems related to donor blood could be overcome with hemoglobin sub-micron particles (HbMPs) that are able to bind and deliver oxygen. On the other hand, the length of the circulation time of HbMPs in the bloodstream strongly depends on their surface properties and can be improved with biopolymer coatings. The redox potential of HbMPs and HbMPs coated with biopolymers using the layer-by-layer technique (LbL-HbMPs) is related to the energy required for electron transfer upon transition from an oxidized to a reduced state. It can be used as a measure of the stability of Hb against oxidation, which is directly connected with its function as an oxygen carrier. The redox potential of Hb, HbMPs, and LbL-HbMPs was determined by a spectroelectrochemical method utilizing the shift of the Soret peak of Hb upon oxidation/reduction of the iron in the heme. The obtained results showed a slight shift in the redox potential of both particle types of about 17 mV towards more negative values compared to the free Hb in the solution. It was demonstrated that the free Hb and the cross-linked Hb in HbMPs and LbL-HbMPs undergo transitions from an oxidized to a reduced state and vice versa several times without Hb destruction. The LbL coating does not affect the redox properties of HbMPs. This ability, as well as the proximity of the obtained redox potentials of Hb, HbMPs, and LbL-HbMPs, indicates that the eventual oxidation of HbMPs in the bloodstream is reversible; thus, HbMPs can be active as artificial oxygen carriers for a longer period of time.