Microfluidic Manufacturing of PEG Surface-Conjugated Liposome-Encapsulated Hemoglobin

Abstract

Over the past few decades, PEG surface-conjugated liposome-encapsulated hemoglobin (PEG-HbV) has been investigated as a red blood cell (RBC) substitute. However, the formulation and homogenization processes to refine the size of particles take extensive time and effort. Hence, microfluidic devices were explored to synthesize PEG-HbV by manipulating small volumes in a microchannel environment using a lab-on-a-chip approach. Microfluidic devices allow ease of scale-up, precise control of flow rates to adjust liposome size, and faster synthesis times. In this study, a herringbone microfluidic chip design was selected for the synthesis of PEG-HbV, wherein a lipid stream and aqueous stream converged and underwent chaotic mixing from pattern indentations to form liposomes. The lipid stream contained a solution of distearoylphosphatidylcholine (DSPC), distearoylphosphatidylethanolamine poly(ethylene glycol)5000 (DSPE-PEG5000) and cholesterol dissolved in pure ethanol. The aqueous stream contained human hemoglobin (hHb) dispersed in phosphate-buffered saline (PBS). This study tested the parameters of lipid composition, organic phase-to-aqueous phase flow rate ratios, and hHb concentration. Based on results from microscopy, the morphology of synthesized PEG-HbVs was spherical, which confirmed the synthesis of PEG-HbV particles and entrapment of hemoglobin. The preliminary goal guiding syntheses was to produce monodisperse PEG-HbV particles with an average diameter of 200 nm. The particles manufactured ranged in diameter from 180 nm to 600 nm with some variability in size reaching over 1 µm, leaving room for further parameter optimization. Overall, this initial goal of this study was to determine the potential for using microfluidics to synthesize PEG-HbV as an RBC substitute, then to see how different parameters affect PEG-HbVs to try and match previous PEG-HbV dimensions.A three-year embargo was granted for this item.Academic Major: Chemical Engineerin