New formats for affinity selection of human cells

Despite recent advances in stem cell biology, immunotherapy and transplantation, substantial barriers still exist in the large-scale specific separation of a discrete population of human therapeutic cells from a cell suspension. The ideal purification technique should combine high cell purity, yield and function, with fast processing and affordability. Currently, fluorescence-activated cell sorting with flow cytometry (FACS) and magnetic activated cell sorting (MACS®) are the most used methods for cell separation and purification and have been employed extensively in molecular biology, diagnostic and cell sorting applications, because they are considered to be gentle, fast and scalable. However, these methods have several key disadvantages; they are invariably expensive, yield low log cell reduction (LCR) rates, and suffer from drawbacks when applied to niche cell populations, such as those requiring multiple tandem separation steps and/or involving combined positive and negative cell selection steps. To address this challenge, a new cell affinity selection system was developed. The selectivity is based on the reversible monomeric avidin biotin interaction and it is primary designed for positive selection. The initial studies were performed on flat, nonporous, glass coverslips and the technology was then successfully transferred on high grade smooth non-porous glass beads (with a diameter of 79.12 to 118.59 μm). The multi-step layer-by-layer deposition procedure culminating in dextran-coated supports bearing monomeric avidin was rigorously characterized and subsequently employed in packed bed chromatography experiments with human erythrocytes isolated from cord blood and B lymphocytes from cell lines. The developed affinity selection platform was highly selective, efficient and, most importantly, resulted in high yields, cell purity and viability comparable with MACS® technology. Additionally scale up is possible and could be easily transferred to another chromatographic matrix with the appropriate structure.