Recommendations on fit-for-purpose criteria to establish quality management for microphysiological systems and for monitoring their reproducibility.

Cell culture technology has evolved, moving from single-cell and monolayer methods to 3D models like reaggregates, spheroids, and organoids, improved with bioengineering like microfabrication and bioprinting. These advancements, termed microphysiological systems (MPSs), closely replicate tissue environments and human physiology, enhancing research and biomedical uses. However, MPS complexity introduces standardization challenges, impacting reproducibility and trust. We offer guidelines for quality management and control criteria specific to MPSs, facilitating reliable outcomes without stifling innovation. Our fit-for-purpose recommendations provide actionable advice for achieving consistent MPS performance.

From animal testing to in vitro systems: advancing standardization in microphysiological systems.

Limitations with cell cultures and experimental animal-based studies have had the scientific and industrial communities searching for new approaches that can provide reliable human models for applications such as drug development, toxicological assessment, and in vitro pre-clinical evaluation. This has resulted in the development of microfluidic-based cultures that may better represent organs and organ systems in vivo than conventional monolayer cell cultures. Although there is considerable interest from industry and regulatory bodies in this technology, several challenges need to be addressed for it to reach its full potential. Among those is a lack of guidelines and standards. Therefore, a multidisciplinary team of stakeholders was formed, with members from the US Food and Drug Administration (FDA), the National Institute of Standards and Technology (NIST), European Union, academia, and industry, to provide a framework for future development of guidelines/standards governing engineering concepts of organ-on-a-chip models. The result of this work is presented here for interested parties, stakeholders, and other standards development organizations (SDOs) to foster further discussion and enhance the impact and benefits of these efforts.

Taking the leap toward human-specific nonanimal methodologies: The need for harmonizing global policies for microphysiological systems.

With a recent amendment, India joined other countries that have removed the legislative barrier toward the use of human-relevant methods in drug development. Here, global stakeholders weigh in on the urgent need to globally harmonize the guidelines toward the standardization of microphysiological systems. We discuss a possible framework for establishing scientific confidence and regulatory approval of these methods.

Putting Science into Standards workshop on standards for organ-on-chip.

The European Commission Joint Research Centre and the European Standardization Organizations CEN and CENELEC organized the "Putting Science into Standards" workshop, focusing on organ-on-chip technologies. The workshop, held online on 28-29 April, 2021, aimed at identifying needs and priorities for standards development and suggesting possible ways forward.

Standardisation needs for organ on chip devices.

Organ on chip (OoC) devices represent the cutting edge of biotechnologies, combining advanced cell and tissue culture with microengineering. OoC is accelerating innovation in the life sciences and has the potential to revolutionise many fields including biomedical research, drug development and chemical risk assessment. In order to gain acceptance by end-users of OoC based methods and the data derived from them, and to establish OoC approaches as credible alternatives to animal testing, OoC devices need to go through an extensive qualification process. In this context, standardisation can play a key role in ensuring proper characterisation of individual devices, benchmarking against appropriate reference elements and aiding efficient communication among stakeholders. The development of standards for OoC will address several important issues such as basic terminology, device classification, and technical and biological performance. An analysis of technical and biological aspects related to OoC is presented here to identify standardisation areas specific for OoC, focusing on needs and opportunities. About 90 standards are already available from related fields including microtechnologies, medical devices and in vitro cell culture, laying the basis for future work in the OoC domain. Finally, two priority areas for OoC are identified that could be addressed with standards, namely, characterisation of small molecule absorption and measurement of microfluidic parameters.

Deformation of leukaemia cell lines in hyperbolic microchannels: investigating the role of shear and extensional components.

The mechanical properties of cells are of enormous interest in a diverse range of physio and pathological situations of clinical relevance. Unsurprisingly, a variety of microfluidic platforms have been developed in recent years to study the deformability of cells, most commonly employing pure shear or extensional flows, with and without direct contact of the cells with channel walls. Herein, we investigate the effects of shear and extensional flow components on fluid-induced cell deformation by means of three microchannel geometries. In the case of hyperbolic microchannels, cell deformation takes place in a flow with constant extensional rate, under non-zero shear conditions. A sudden expansion at the microchannel terminus allows one to evaluate shape recovery subsequent to deformation. Comparison with other microchannel shapes, that induce either pure shear (straight channel) or pure extensional (cross channel) flows, reveals different deformation modes. Such an analysis is used to confirm the softening and stiffening effects of common treatments, such as cytochalasin D and formalin on cell deformability. In addition to an experimental analysis of leukaemia cell deformability, computational fluid dynamic simulations are used to deconvolve the role of the aforementioned flow components in the cell deformation dynamics. In general terms, the current study can be used as a guide for extracting deformation/recovery dynamics of leukaemia cell lines when exposed to various fluid dynamic conditions.

Shear-Induced Encapsulation into Red Blood Cells: A New Microfluidic Approach to Drug Delivery.

Encapsulating molecules into red blood cells (RBCs) is a challenging topic for drug delivery in clinical practice, allowing to prolong the residence time in the body and to avoid toxic residuals. Fluidic shear stress is able to temporary open the membrane pores of RBCs, thus allowing for the diffusion of a drug in solution with the cells. In this paper, both a computational and an experimental approach were used to investigate the mechanism of shear-induced encapsulation in a microchannel. By means of a computational fluid dynamic model of a cell suspension, it was possible to calculate an encapsulation index that accounts for the effective shear acting on the cells, their distribution in the cross section of the microchannel and their velocity. The computational model was then validated with micro-PIV measurements on a RBCs suspension. Finally, experimental tests with a microfluidic channel showed that, by choosing the proper concentration and fluid flow rate, it is possible to successfully encapsulate a test molecule (FITC-Dextran, 40 kDa) into human RBCs. Cytofluorimetric analysis and confocal microscopy were used to assess the RBCs physiological shape preservation and confirm the presence of fluorescent molecules inside the cells.

Microcirculation in the murine liver: a computational fluid dynamic model based on 3D reconstruction from in vivo microscopy.

The liver is organized in hexagonal functional units - termed lobules - characterized by a rather peculiar blood microcirculation, due to the presence of a tangled network of capillaries - termed sinusoids. A better understanding of the hemodynamics that governs liver microcirculation is relevant to clinical and biological studies aimed at improving our management of liver diseases and transplantation. Herein, we built a CFD model of a 3D sinusoidal network, based on in vivo images of a physiological mouse liver obtained with a 2-photon microscope. The CFD model was developed with Fluent 16.0 (ANSYS Inc., Canonsburg, PA), particular care was taken in imposing the correct boundary conditions representing a physiological state. To account for the remaining branches of the sinusoids, a lumped parameter model was used to prescribe the correct pressure at each outlet. The effect of an adhered cell on local hemodynamics is also investigated for different occlusion degrees. The model here proposed accurately reproduces the fluid dynamics in a portion of the sinusoidal network in mouse liver. Mean velocities and mass flow rates are in agreement with literature values from in vivo measurements. Our approach provides details on local phenomena, hardly described by other computational studies, either focused on the macroscopic hepatic vasculature or based on homogeneous porous medium model.

Herringbone-like hydrodynamic structures in microchannels: A CFD model to evaluate the enhancement of surface binding.

Selected adsorption efficiency of a molecule in solution in a microchannel is strongly influenced by the convective/diffusive mass transport phenomena that supply the target molecule to the adsorption surface. In a standard microchannel with a rectangular cross section, laminar flow regime limits the fluid mixing, thus suggesting that mass transport conditions can be improved by the introduction of herringbone-like structures. Tuning of these geometrical patterns increases the concentration gradient of the target molecule at the adsorption surface. A computational fluid dynamic (CFD) study was performed to evaluate the relation between the geometrical herringbone patterns and the concentration gradient improvement in a 14 mm long microchannel. The results show that the inhomogeneity of the concentration gradient can provide an improved and localized adsorption under specific geometrical features, which can be tuned in order to adapt the adsorption pattern to the specific assay requirements.