A perfusion-capable microfluidic bioreactor for assessing microbial heterologous protein production

A high-density microfluidic bioreactor for the automated manufacturing of CAR T cells

The manufacturing of autologous chimaeric antigen receptor (CAR) T cells largely relies either on fed-batch and manual processes that often lack environmental monitoring and control or on bioreactors that cannot be easily scaled out to meet patient demands. Here we show that human primary T cells can be activated, transduced and expanded to high densities in a 2 ml automated closed-system microfluidic bioreactor to produce viable anti-CD19 CAR T cells (specifically, more than 60 million CAR T cells from donor cells derived from patients with lymphoma and more than 200 million CAR T cells from healthy donors). The in vitro secretion of cytokines, the short-term cytotoxic activity and the long-term persistence and proliferation of the cell products, as well as their in vivo anti-leukaemic activity, were comparable to those of T cells produced in a gas-permeable well. The manufacturing-process intensification enabled by the miniaturized perfusable bioreactor may facilitate the analysis of the growth and metabolic states of CAR T cells during ex vivo culture, the high-throughput optimization of cell-manufacturing processes and the scale out of cell-therapy manufacturing.

The chemical neighborhood of cells in a diffusion-limited system

Microorganisms follow us everywhere, and they will be essential to sustaining long-term human space exploration through applications such as vitamin synthesis, biomining, and more. Establishing a sustainable presence in space therefore requires that we better understand how stress due to the altered physical conditions of spaceflight affects our companion organisms. In microgravity environments such as orbital space stations, microorganisms likely experience the change in gravity primarily through changes in fluid mixing processes. Without sedimentation and density-driven convection, diffusion becomes the primary process governing the movement of growth substrates and wastes for microbial cells in suspension culture. Non-motile cells might therefore develop a substrate-deficient "zone of depletion" and experience stress due to starvation and/or waste build-up. This would in turn impact the concentration-dependent uptake rate of growth substrates and could be the cause of the altered growth rates previously observed in microorganisms in spaceflight and in ground-simulated microgravity. To better understand the extent of these concentration differences and their potential influence on substrate uptake rates, we used both an analytical solution and finite difference method to visualize concentration fields around individual cells. We modeled diffusion, using Fick's Second Law, and nutrient uptake, using Michaelis-Menten kinetics, and assessed how that distribution varies in systems with multiple cells and varied geometries. We determined the radius of the zone of depletion, within which cells had reduced the substrate concentration by 10%, to be 5.04 mm for an individual Escherichia coli cell in the conditions we simulated. However, we saw a synergistic effect with multiple cells near each other: multiple cells in close proximity decreased the surrounding concentration by almost 95% from the initial substrate concentration. Our calculations provide researchers an inside look at suspension culture behavior in the diffusion-limited environment of microgravity at the scale of individual cells.

Application of Microfluidic Technology in Antibody Screening

Specific antibodies are widely used in the biomedical field. Current screening methods for specific antibodies mainly involve hybridoma technology and antibody engineering techniques. However, these technologies suffer from tedious screening processes, long preparation periods, high costs, low efficiency, and a degree of automation, which have become a bottleneck for the screening of specific antibodies. To overcome these difficulties, microfluidics has been developed as a promising technology for high-throughput screening and high purity of antibody. In this review, we provide an overview of the recent advances in microfluidic applications for specific antibody screening. In particular, hybridoma technology and four antibody engineering techniques (including phage display, single B cell antibody screening, antibody expression, and cell-free protein synthesis) based on microfluidics have been introduced, challenges, and the future outlook of these technologies are also discussed. This article is protected by copyright. All rights reserved.

Recent advances of integrated microfluidic suspension cell culture system

Microfluidic devices with superior microscale fluid manipulation ability and large integration flexibility offer great advantages of high throughput, parallelisation and multifunctional automation. Such features have been extensively utilised to facilitate cell culture processes such as cell capturing and culturing under controllable and monitored conditions for cell-based assays. Incorporating functional components and microfabricated configurations offered different levels of fluid control and cell manipulation strategies to meet diverse culture demands. This review will discuss the advances of single-phase flow and droplet-based integrated microfluidic suspension cell culture systems and their applications for accelerated bioprocess development, high-throughput cell selection, drug screening and scientific research to insight cell biology. Challenges and future prospects for this dynamically developing field are also highlighted.

Microscale Perfusion-Based Cultivation for Pichia pastoris Clone Screening Enables Accelerated and Optimized Recombinant Protein Production Processes

Pichia pastoris has emerged in the past years as a promising host for recombinant protein and biopharmaceutical production. In the establishment of high cell density fed-batch biomanufacturing, screening phase and early bioprocess development (based on microplates and shake flasks) still represent a bottleneck due to high-cost and time-consuming procedures as well as low experiment complexity. In the present work, a screening protocol developed for P. pastoris clone selection is implemented in a multiplexed microfluidic device with 15 μL cultivation chambers able to operate in perfusion mode and monitor dissolved oxygen content in the culture in a non-invasive way. The setup allowed us to establish carbon-limited conditions and evaluate strain responses to different input variables. Results from micro-scale perfusion cultures are then compared with 1L fed-batch fermentation. The best producer in terms of titer and productivity is rapidly identified after 12 h from inoculation and the results confirmed by lab-scale fermentation. Moreover, the physiological analyses of the strains under different conditions suggested how more complex experimental conditions are achievable despite the relatively easy, straight-forward, and cost-effective experimental setup. Implementation and standardization of these micro-scale protocols could reduce the demand for lab-scale bioreactor cultivations thus accelerating the development of protein production processes.

Recent Developments in Bioprocessing of Recombinant Proteins: Expression Hosts and Process Development

Infectious diseases, along with cancers, are among the main causes of death among humans worldwide. The production of therapeutic proteins for treating diseases at large scale for millions of individuals is one of the essential needs of mankind. Recent progress in the area of recombinant DNA technologies has paved the way to producing recombinant proteins that can be used as therapeutics, vaccines, and diagnostic reagents. Recombinant proteins for these applications are mainly produced using prokaryotic and eukaryotic expression host systems such as mammalian cells, bacteria, yeast, insect cells, and transgenic plants at laboratory scale as well as in large-scale settings. The development of efficient bioprocessing strategies is crucial for industrial production of recombinant proteins of therapeutic and prophylactic importance. Recently, advances have been made in the various areas of bioprocessing and are being utilized to develop effective processes for producing recombinant proteins. These include the use of high-throughput devices for effective bioprocess optimization and of disposable systems, continuous upstream processing, continuous chromatography, integrated continuous bioprocessing, Quality by Design, and process analytical technologies to achieve quality product with higher yield. This review summarizes recent developments in the bioprocessing of recombinant proteins, including in various expression systems, bioprocess development, and the upstream and downstream processing of recombinant proteins.

Enhancing the functionality of a microscale bioreactor system as an industrial process development tool for mammalian perfusion culture

Without a scale-down model for perfusion, high resource demand makes cell line screening or process development challenging, therefore, potentially successful cell lines or perfusion processes are unrealized and their ability untapped. We present here the refunctioning of a high-capacity microscale system that is typically used in fed-batch process development to allow perfusion operation utilizing in situ gravity settling and automated sampling. In this low resource setting, which involved routine perturbations in mixing, pH and dissolved oxygen concentrations, the specific productivity and the maximum cell concentration were higher than 3.0 × 10⁶  mg/cell/day and 7 × 10 ⁷ cells/ml, respectively, across replicate microscale perfusion runs conducted at one vessel volume exchange per day. A comparative analysis was conducted at bench scale with vessels operated in perfusion mode utilizing a cell retention device. Neither specific productivity nor product quality indicated by product aggregation (6%) was significantly different across scales 19 days after inoculation, thus demonstrating this setup to be a suitable and reliable platform for evaluating the performance of cell lines and the effect of process parameters, relevant to perfusion mode of culturing.

Integrated Bottom-Up and Top-Down Liquid Chromatography-Mass Spectrometry for Characterization of Recombinant Human Growth Hormone Degradation Products

With the advent of biosimilars to the U.S. market, it is important to have better analytical tools to ensure product quality from batch to batch. In addition, the recent popularity of using a continuous process for production of biopharmaceuticals, the traditional bottom-up method, alone for product characterization and quality analysis is no longer sufficient. Bottom-up method requires large amounts of material for analysis and is labor-intensive and time-consuming. Additionally, in this analysis, digestion of the protein with enzymes such as trypsin could induce artifacts and modifications which would increase the complexity of the analysis. On the other hand, a top-down method requires a minimum amount of sample and allows for analysis of the intact protein mass and sequence generated from fragmentation within the instrument. However, fragmentation usually occurs at the N-terminal and C-terminal ends of the protein with less internal fragmentation. Herein, we combine the use of the complementary techniques, a top-down and bottom-up method, for the characterization of human growth hormone degradation products. Notably, our approach required small amounts of sample, which is a requirement due to the sample constraints of small scale manufacturing. Using this approach, we were able to characterize various protein variants, including post-translational modifications such as oxidation and deamidation, residual leader sequence, and proteolytic cleavage. Thus, we were able to highlight the complementarity of top-down and bottom-up approaches, which achieved the characterization of a wide range of product variants in samples of human growth hormone secreted from Pichia pastoris.

Synthetic biology and microbioreactor platforms for programmable production of biologics at the point-of-care

Current biopharmaceutical manufacturing systems are not compatible with portable or distributed production of biologics, as they typically require the development of single biologic-producing cell lines followed by their cultivation at very large scales. Therefore, it remains challenging to treat patients in short time frames, especially in remote locations with limited infrastructure. To overcome these barriers, we developed a platform using genetically engineered Pichia pastoris strains designed to secrete multiple proteins on programmable cues in an integrated, benchtop, millilitre-scale microfluidic device. We use this platform for rapid and switchable production of two biologics from a single yeast strain as specified by the operator. Our results demonstrate selectable and near-single-dose production of these biologics in <24 h with limited infrastructure requirements. We envision that combining this system with analytical, purification and polishing technologies could lead to a small-scale, portable and fully integrated personal biomanufacturing platform that could advance disease treatment at point-of-care.