A Sample Preparation Strategy For Portable Blood Counting Based On Large Field-of-view Cellular Imaging

Blood cell counting is one of the most routine clinical tests,and provides part of important guidence for initial diagnosis and screening for diseases.Numerous studies have shown that flow-based or imaging-based instruments are capable of counting blood cells with the potential of being portable.These methods have common problems.For instance,simple experimental procedures can only obtain a single parameter,or multiple reagents/instrumental components are required to obtain multiple parameters.Our research group previously developed a small microscopic system based on the concept of counting of blood cells using large field-of-view imaging.However,the surfactant used to sphere red blood cells conflicts with the fluorescent dye used to stain white blood cells and platelets,and thus the two preparation steps have to be separated.On the other hand,the imaging chambers used in this method are from commercial providers and costly due to its exact thickness control(100 μm).These issues do not meet the practical needs of point of care testing.To solve this problem,we have developed a simple and efficient sample preparation method for portable blood cell counting.The main contents include:(1)A surfactant 3-(N,N-Dimethyloctadecylammonio)propanesulfonate(DOPS)was selected instead of the anionic surfactant sodium dodecyl sulfate(SDS).DOPS has no interference on the fluorescence intensity of acridine orange(AO),so these two reagents have good compatibility.DOPS spheres red blood cells effeciently,and it applies for blood samples of various cellular densities.By adjusting the concentrations of DOPS,dye,salt ions and environmental pH,we have determined the optimal blood sample preparation conditions.(2)Monolayers of blood cells are formed when the blood dilution factors and the chamber depths are co-optimized.By controlling the chamber depth,this type of lab-made imaging chambers can replace the commercial chambers with lower cost but still maintaining the counting accuracy.(3)Dry forms of reagents are pre-stored in centrifuge vials.This method increases the storage time of reagents,ensures the reproducibility of sample preparation,and enables detection of multiple parameters.This method may further advance the technology to be used in low-resource settings for the detection of blood cell counts.