Background

Blood components such as erythrocyte concentrates remain in high demand. Artificial oxygen carriers in the form of a perfluorodecalin (PFD)-based nanoemulsion with an albumin shell (A-AOCs) offer a promising alternative. In prior experiments our group verified pertinent oxygen transport capacity of A-AOCs.[1-2] When injected into patients, A‑AOCs come into contact with their erythrocytes. In this study it was evaluated if human erythrocytes remain intact and functional after contact with A‑AOCs.

Methods

A-AOCs were synthesized by high-pressure homogenization of bovine serum albumin (BSA) along with PFD. These were mixed with human whole blood (local ethics approval no.21-10314-BO) at a clinically relevant ratio for up to 24 h at 37 °C and static conditions. Spectroscopic photometry was used to detect the free plasma hemoglobin concentration. Hematocrit and osmolality were determined along with glucose and lactate levels by using a blood gas analyzer. In addition, viscosity was measured utilizing a rheometer. To test A-AOCs in a physiologically relevant in vitro set-up, an artificial blood vessel was manufactured with a bio‑3D printer using gelatin-methacryloyl and poloxamer 407.

Results

When mixing human whole blood with A-AOCs in a 1:1 ratio, the viscosity increased as indicated by photometric hemoglobin determination, which was caused by hemolysis of the erythrocytes. This phenomenon could be attributed to a combination of control solution (BSA) and A-AOCs as it was already increased in the control group (1:1 blood/BSA). In a more diluted (4:1 ratio) formulation, erythrocytes stayed intact for 24 h and viscosity was not impaired. These positive results were corroborated by a rise in lactate levels and a concomitant drop in glucose levels (Fig 1.) indicating, that functional erythrocytes were still producing energy through anaerobic glycolysis. The 3D‑printed blood vessels could be integrated in a perfusion circuit.

Conclusion

To summarize, the study demonstrated that in presence of low amounts of A-AOCs in a 4:1 ratio, erythrocytes retained their functionality. Future research examining blood compatibility and usage of 3D-printed blood vessels in conjunction with endothelial cells will aid in determining the clinical utility of perfluorodecalin nanoemulsions as an artificial oxygen carrier.

References

[1] Wrobeln A, Eur J Pharm Biopharm.115,52-64(2017)

[2] Wrobeln A, Artif Cells Nanomed Biot.45(4),723-730(2017)

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