Shear stress increases cytotoxicity and reduces transfection efficiency of liposomal gene delivery to CHO-S cells

Synthetic Cell Armor Made of DNA Origami

The bioengineering applications of cells, such as cell printing and multicellular assembly, are directly limited by cell damage and death due to a harsh environment. Improved cellular robustness thus motivates investigations into cell encapsulation, which provides essential protection. Here we target the cell-surface glycocalyx and cross-link two layers of DNA nanorods on the cellular plasma membrane to form a modular and programmable nanoshell. We show that the DNA origami nanoshell modulates the biophysical properties of cell membranes by enhancing the membrane stiffness and lowering the lipid fluidity. The nanoshell also serves as armor to protect cells and improve their viability against mechanical stress from osmotic imbalance, centrifugal forces, and fluid shear stress. Moreover, it enables mediated cell-cell interactions for effective and robust multicellular assembly. Our results demonstrate the potential of the nanoshell, not only as a cellular protection strategy but also as a platform for cell and cell membrane manipulation.

Proof-of-Concept of Continuous Transfection for Adeno-Associated Virus Production in Microcarrier-Based Culture

Adeno-associated virus vectors (AAV) are reported to have a great potential for gene therapy, however, a major bottleneck for this kind of therapy is the limitation of production capacity. Higher specific AAV vector yield is often reported for adherent cell systems compared to cells in suspension, and a microcarrier-based culture is well established for the culture of anchored cells on a larger scale. The purpose of the present study was to explore how microcarrier cultures could provide a solution for the production of AAV vectors based on the triple plasmid transfection of HEK293T cells in a stirred tank bioreactor. In the present study, cells were grown and expanded in suspension, offering the ease of this type of operation, and were then anchored on microcarriers in order to proceed with transfection of the plasmids for transient AAV vector production. This process was developed in view of a bioreactor application in a 200 mL stirred-tank vessel where shear stress aspects were studied. Furthermore, amenability to a continuous process was studied. The present investigation provided a proof-of-concept of a continuous process based on microcarriers in a stirred-tank bioreactor.

Improved cultivation of Chinese hamster ovary cells in bioreactor with reciprocal mixing

We have constructed a new bioreactor with reciprocal mixing that is better suited for the cultivation of delicate animal cells. In-silico simulation (computational fluid dynamics) suggested both maximum and average shear stresses in the bioreactor with reciprocal mixing to be remarkably lower than in a conventional bioreactor with rotary mixing. Although we could not find any difference in growth speed and cell density between the bioreactors with reciprocal and rotary mixing, we did find cell viability in the reciprocal-mixing bioreactor to be retained longer than in the rotary-paddle bioreactor. This implied that cell culture in a bioreactor with reciprocal mixing could be prolonged for the production of target proteins. Leakage of lactate dehydrogenase activity into the culture medium was suppressed much more in the reciprocal-mixing bioreactor than in the rotary-paddle one. Production of human tissue plasminogen activator in the former system was also observed to be much higher than in the latter. Therefore, a bioreactor with reciprocal mixing was concluded to be better suited for the cultivation of animal cells and efficient production of proteins, such as antibody drugs and various growth factors.

3D Printed Microfluidic Spiral Separation Device for Continuous, Pulsation-Free and Controllable CHO Cell Retention

The development of continuous bioprocesses-which require cell retention systems in order to enable longer cultivation durations-is a primary focus in the field of modern process development. The flow environment of microfluidic systems enables the granular manipulation of particles (to allow for greater focusing in specific channel regions), which in turn facilitates the development of small continuous cell separation systems. However, previously published systems did not allow for separation control. Additionally, the focusing effect of these systems requires constant, pulsation-free flow for optimal operation, which cannot be achieved using ordinary peristaltic pumps. As described in this paper, a 3D printed cell separation spiral for CHO-K1 (Chinese hamster ovary) cells was developed and evaluated optically and with cell experiments. It demonstrated a high separation efficiency of over 95% at up to 20 × 10⁶ cells mL^-1. Control over inlet and outlet flow rates allowed the operator to adjust the separation efficiency of the device while in use-thereby enabling fine control over cell concentration in the attached bioreactors. In addition, miniaturized 3D printed buffer devices were developed that can be easily attached directly to the separation unit for usage with peristaltic pumps while simultaneously almost eradicating pump pulsations. These custom pulsation dampeners were closely integrated with the separator spiral lowering the overall dead volume of the system. The entire device can be flexibly connected directly to bioreactors, allowing continuous, pulsation-free cell retention and process operation.

Micro Versus Macro - The Effect of Environmental Confinement on Cellular Nanoparticle Uptake

While the microenvironment is known to alter the cellular behavior in terms of metabolism, growth and the degree of endoplasmic reticulum stress, its influence on the nanoparticle uptake is not yet investigated. Specifically, it is not clear if the cells cultured in a microenvironment ingest different amounts of nanoparticles than cells cultured in a macroenvironment (for example a petri dish). To answer this question, here we used J774 murine macrophages and fluorescent nanodiamonds (FND) as a model system to systematically compare the uptake efficiency of cells cultured in a petri dish and in a microfluidic channel. Specifically, equal numbers of cells were cultured in two devices followed by the FND incubation. Then cells were fixed, stained and imaged to quantify the FND uptake. We show that the FND uptake in the cells cultured in petri dishes is significantly higher than the uptake in a microfluidic chip where the alteration in CO2 environment, the cell culture medium pH and the surface area to volume ratio seem to be the underlying causes leading to this observed difference.

Combinatory interpretation of protein corona and shear stress for active cancer targeting of bioorthogonally clickable gelatin-oleic nanoparticles

Nanoparticle-protein interactions under conditions mimicking physiology determine how nanoparticles (NPs) will behave inside blood vessels and, therefore, the overall outcome of the drug-delivery system. Here, for the first time, we explore the effects of bio-mimicking shear stress and protein corona conditions on novel active targeting of clickable fattigation nanoparticles (NPs) for cancer therapy. Active targeting dibenzocyclooctyne-functionalized biocompatible gelatin-oleic NPs (GON-DBCOs) via a bioorthogonal click reaction were prepared by the desolvation method for delivery of docetaxel (DTX) to lung and breast cancer models. The effect of shear stress (5 dyne/cm²) and human serum albumin (HSA) protein corona on the cellular behavior of NPs was explored under a dynamic microfluidic system in lung (A549) and breast (MCF-7) cancer cell lines. The developed drug-loaded NPs had a particle size of 300 nm, a narrow size distribution, positive zeta potential, high encapsulation efficacy (72.4%), and spherical morphology. The particle size of the protein corona-coated NPs increased to 341 nm with a negative zeta potential. The inhibitory dose (IC₅₀) increased approximately 3- and 42-fold in A549 and MCF-7 cells, respectively, under dynamic microfluidic conditions compared to static conditions. Cellular uptake was significantly decreased in the presence of shear stress and a protein corona, compared with static conditions, in both lung (A549, **p < 0.01) and breast (MCF-7, *p < 0.05) cancer cell lines. Clathrin-and energy-dependent pathways were found to be involved in the cellular uptake of NPs. This study could serve as a vital tool for the evaluation of NPs under aggressive bio-mimicking conditions comprising shear stress and a protein corona to predict the in vivo performance of NPs and support the preclinical and clinical translation of NP drug delivery systems.

The transient expression of CHIKV VLP in large stirred tank bioreactors

Transient gene expression (TGE) bioprocesses have been difficult to scale up in large stirred tank bioreactors with volumes of more than 1.5 L. Low production levels are often observed, but the causes have not been investigated (Gutierrez-Granados et al. in Crit Rev Biotechnol 38:918-940, 2018). Chikungunya Virus-like particle (VLP), expressed by DNA-PEI transient transfection, is a representative case study for these difficulties. Clinical materials were produced in shake flasks, but the process suffered when transferred to large stirred tank bioreactors. The resulting process was not operationally friendly nor cost effective. In this study, a systematic approach was used to investigate the root causes of the poor scale up performance. The transfection conditions were first screened in ambr® 15 high throughput mini bioreactors then examined in 3 L stirred-tank systems. The studies found that production level was negatively correlated with inoculum cell growth status (P < 0.05). The pH range, DNA and PEI levels, order of the reagent addition, and gas-sparging systems were also studied and found to affect process performance. Further hydromechanical characterizations (Re, energy dissipation rates, and P/V, etc.) of shake flasks, ambr® 15, and 3-L stirred tank systems were performed. Overall, the study discovered that the shear stress (caused by a microsparger) and PEI toxicity together were the root causes of scale-up failure. Once the microsparger was replaced by a macrosparger, the scale-up was successful.

3D Printed Microfluidic Mixers-A Comparative Study on Mixing Unit Performances

One of the basic operations in microfluidic systems for biological and chemical applications is the rapid mixing of different fluids. However, flow profiles in microfluidic systems are laminar, which means molecular diffusion is the only mixing effect. Therefore, mixing structures are crucial to enable more efficient mixing in shorter times. Since traditional microfabrication methods remain laborious and expensive, 3D printing has emerged as a potential alternative for the fabrication of microfluidic devices. In this work, five different passive micromixers known from literature are redesigned in comparable dimensions and manufactured using high-definition MultiJet 3D printing. Their mixing performance is evaluated experimentally, using sodium hydroxide and phenolphthalein solutions, and numerically via computational fluid dynamics. Both experimental and numerical analysis results show that HC and Tesla-like mixers achieve complete mixing after 0.99 s and 0.78 s, respectively, at the highest flow rate (Reynolds number (Re) = 37.04). In comparison, Caterpillar mixers exhibit a lower mixing rate with complete mixing after 1.46 s and 1.9 s. Furthermore, the HC mixer achieves very good mixing performances over all flow rates (Re = 3.7 to 37.04), while other mixers show improved mixing only at higher flow rates.