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Harvesting adherent cells from microcarriers has become one of the major challenges of the downstream bioprocessing at large scale the current method has high maintenance and operation cost, which are the results of frequent clogging, due to cell lysing effect and microcarrier cake formation on membrane-based technology. These problems hugely impede the adaptation of microcarriers technologies in large-scale cell culture and hampered the supply of cells to the clinical need. Here, we describe two 3D printing-based methods to fabricate inertial microfluidic devices for separating adherent cells from microcarriers which overcome the above-mentioned limitations. The spiral devices are employed to separate mesenchymal stem cells from the microcarriers with 99% microcarrier removal rate and 77% cell recovery rate in one round of separation., (© 2021. Springer Science+Business Media, LLC.)

Recently, particle concentration and filtration using inertial microfluidics have drawn attention as an alternative to membrane and centrifugal technologies for industrial applications, where the target particle size varies between 1 µm and 500 µm. Inevitably, the bigger particle size (>50 µm) mandates scaling up the channel cross-section or hydraulic diameter (D H > 0.5 mm). The Dean-coupled inertial focusing dynamics in spiral microchannels is studied broadly; however, the impacts of secondary flow on particle migration in a scaled-up spiral channel is not fully elucidated. The mechanism of particle focusing inside scaled-up rectangular and trapezoidal spiral channels (i.e., 5-10× bigger than conventional microchannels) with an aim to develop a continuous and clog-free microfiltration system for bioprocessing is studied in detail. Herein, a unique focusing based on inflection point without the aid of sheath flow is reported. This new focusing mechanism, observed in the scaled-up channels, out-performs the conventional focusing scenarios in the previously reported trapezoidal and rectangular channels. Finally, as a proof-of-concept, the utility of this device is showcased for the first time as a retention system for a cell-microcarrier (MC) suspension culture., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Rapidly evolving cell-based therapies towards clinical trials demand alternative approaches for efficient expansion of adherent cell types such as human mesenchymal stem cells (hMSCs). Using microcarriers (100-300 µm) in a stirred tank bioreactor offers considerably enhanced surface to volume ratio of culture environment. However, downstream purification of the harvested cell product needs to be addressed carefully due to distinctive features and fragility of these cell products. This work demonstrates a novel alternative approach which utilizes inertial focusing to separate microcarriers (MCs) from the final cell suspension. First, we systematically investigated MC focusing dynamics inside scaled-up curved channels with trapezoidal and rectangular cross-sections. A trapezoidal spiral channel with ultra-low-slope (Tan(α) = 0.0375) was found to contribute to strong MC focusing (~300 < Re < ~400) while managing high MC volume fractions up to ~1.68%. Accordingly, the high-throughput trapezoidal spiral channel successfully separated MCs from hMSC suspension with total cell yield~94% (after two passes) at a high volumetric flow rate of ~30 mL/min (Re~326.5).