## 4 Conclusions  
A numerical investigation was performed to systematically investigate the deformability and morphology changes of RBCs undergoing storage lesion. It is hypothesized that discocyte, echinocyte I, echinocyte II, echinocyte III and sphero-echinocyte morphologies and associated changes in cell membrane mechanics and cell geometry during in-vitro storage, can be attributed to a CG-RBC membrane approach integrated with the BCM-based membrane free energy model. The CG-RBC membrane model [76] captures the essential features of RBC echinocytosis during in-vitro storage, and enables valuable predictions of the influence of storage lesion on RBC quality and viability. The predicted morphology and deformability characteristics of RBC echinocytosis confirms the decreasing cell deformability, and thereby the decreasing quality and viability of stored RBCs with increasing storage duration. Differences in deformability and morphology characteristics: cell shape factor, elongation index and membrane spicule details such as number of spicules, average spicule height, average spicule surface area and average spicule curvature, were observed between the storage lesion-produced and echinocytogenic shape-transforming conditions-produced echinocyte I, echinocyte II, echinocyte III and sphero-echinocyte morphologies. Furthermore, the results predict the adverse influence of membrane structural defects due to storage lesion on cell deformability and recoverability during mechanical deformations, and indicate further degradation of cell viability. RBC storage lesion is a significant issue facing transfusion treatments, and despite the improved in-vitro storage procedures, storage lesion still occurs, affecting the maximum storage time for a healthy and safe RBC supply. Therefore, improved understanding of the interrelation between quality and viability of stored RBCs and storage lesion is essential to prevent or reduce transfusion related adverse outcomes. The present numerical study provides a strengthened approach for such understanding, and can be extended for a detailed discussion of the relationship between storage lesion  
Figure 12: The recovered stretched cell shapes of day 42 sphero-echinocyte RBCs with (**a**) 0% and (**b**) 25% of defective vertical interactions (\(A_{Vertical}\)) at optical tweezers stretching forces of \(P^{ext}\) = 60.0 pN, and that of RBCs having (**c**) \(A_{Vertical}\) = 0% and (**d**) \(A_{Vertical}\) = 25% at \(P^{ext}\) = 200.0 pN. and RBC membrane mechanics, where any associated changes to the lipid-bilayer and/or cytoskeletal spectrin network should be considered. In addition, the availability of any physicochemical models that discuss the influence of storage environment on red blood cells along with these numerical investigations on RBC membrane mechanics would facilitate better predictions of the storage lesion. The present study assumes a homogeneous population of healthy young RBCs at day 0 of storage. However, RBCs are a heterogenous population with different ages, and they are also affected by donor characteristics such as donor age, gender and health. Therefore, this study can be extended further to investigate the influence of these donor characteristics on RBCs during storage. Insights gained from such investigations will facilitate better storage procedure and transfusion practices. Moreover, this numerical approach provides a potential framework to study the membrane vesiculation and RBC deformation characteristics under varying pathophysiological conditions, and the influence of altered membrane proteins on RBC function such as hereditary haemolytic disorders (i.e., spherocytosis, elliptocylosis and ovalocytosis) for better diagnostics and treatments. Finally, this study is currently being extended to investigate the recoverability of deformability and morphology changes of RBCs undergoing storage lesion. [PERSON] developed the CG-RBC model and algorithm, performed modelling, data analysis and composed the manuscript.