## Modelling of Red Blood Cell Morphological and Deformability Changes during In-Vitro Storage  
**[PERSON] 1**\({}^{\copyright}\), [PERSON] 1,*, [PERSON] 2**\({}^{\copyright}\), [PERSON] 3 and [PERSON] 1  
1 School of Mechanical, Medical and Process Engineering, Science and Engineering Faculty, Queensland University of Technology (QUT), Brisbane City, QLD 4000, Australia; [EMAIL_ADDRESS] (N.G.); [EMAIL_ADDRESS] (Y.G.)
2 School of Mechanical and Mechatronic Engineering, University of Technology Sydney (UTS), Ultimo, NSW 2007, Australia; [PERSON]ESS]
3 Research and Development, Australian Red Cross Lifeblood, Kelvin Grove, QLD 4059, Australia; [EMAIL_ADDRESS]
* Correspondence: [EMAIL_ADDRESS]  
Received: 28 February 2020; Accepted: 27 April 2020; Published: 4 May 2020  
**Featured Application: Red blood cell (RBC) storage lesion is a critical issue facing transfusion treatments, and significant changes in RBC morphology and deformability are observed due to the storage lesion. RBCs require high deformability to sustain in-vivo circulation, and impaired deformability leads to several post-transfusion adverse outcomes. Therefore, improved understanding of the interrelation between the morphological and deformability changes and the quality and viability of the stored RBCs is essential to prevent or reduce the transfusion related adverse outcomes. To support this requisite, the influence on RBC deformability due to several aspects of the storage lesion, namely, the changes in cell morphology, surface area and volume, RBC membrane biomechanics, and cytoskeletal structural integrity are explored numerically in this study.**  
Storage lesion is a critical issue facing transfusion treatments, and it adversely affects the quality and viability of stored red blood cells (RBCs). RBC deformability is a key indicator of cell health. Deformability measurements of each RBC unit are a key challenge in transfusion medicine research and clinical haematology. In this paper, a numerical study, inspired from the previous research for RBC deformability and morphology predictions, is conducted for the first time, to investigate the deformability and morphology characteristics of RBCs undergoing storage lesion. This study investigates the evolution of the cell shape factor, elongation index and membrane spicule details, where applicable, of discocyte, echinocyte I, echinocyte II, echinocyte III and sphero-echinocyte morphologies during 42 days of in-vitro storage at 4 \({}^{\circ}\)C in saline-adenine-glucose-mannitol (SAGM). Computer simulations were performed to investigate the influence of storage lesion-induced membrane structural defects on cell deformability and its recoverability during optical tweezers stretching deformations. The predicted morphology and deformability indicate decreasing quality and viability of stored RBCs undergoing storage lesion. The loss of membrane structural integrity due to the storage lesion further degrades the cell deformability and recoverability during mechanical deformations. This numerical approach provides a potential framework to study the RBC deformation characteristics under varying pathophysiological conditions for better diagnostics and treatments.  
red blood cells; storage lesion; deformability; morphology; elongation index; optical tweezers stretching