Micro-Rheology and Co-Stream Microfluidics Reveal Critical Contributions of Platelet Concentrate Components to Blood Platelet Integrity in Storage

Fluid viscosity is important in both physical and biological systems, as it helps describe a fluid’s material properties. Recent findings show that the shear stress experienced during storage of blood products can result in damage of platelets making the viscosity of stored platelet concentrates (PC) an important area of study. In this work we characterised the contribution of different components of the PC to viscosity using nanoparticle tracking microrheometry and co-stream microfluidics, to determine whether reduced viscosity approaches can improve PC quality over storage. Validation experiments showed both methods could accurately report on the viscosity of samples, with the microfluidics approach deemed preferable due to the possibility of changing flow rates and therefore studying a range of shear stress. PC quality was assessed over 8 days by measuring platelet count, mean platelet volume (MPV), platelet distribution width (PDW), pH, aggregation, and platelet activation markers. Results showed that PC viscosity depends on the residual plasma following processing and is independent of the stored platelet concentration. Reducing plasma to 10% maintained PC quality over 8 days, but further plasma reductions led to reduced platelet counts and increased MPV by day 8. Platelet function, including aggregation and activation, were similar with plasma levels ≥ 10%. This study concludes reduced plasma strategies for PC have limited influence on mitigating shear induced platelet deterioration over storage.