Construction of multiple concentration gradients for single-cell level drug screening

Engineered microenvironments and pancreatic islet-on-chips for screening sugar substitute and antidiabetic compounds

Recent advancements in the food industry have rekindled interest in the safety of food additives, such as sugar substitutes and food pigments. Consequently, the main purpose of this study was to develop models that can more accurately predict the effects of these additives on the human body. In response to this demand, we have created an innovative pancreas islet-on-a-chip system featuring a concentration gradient generator and a perfusable 3D cell culture array. This setup facilitates the 3D culture of pseudo-islets under stable biochemical and biophysical conditions. When compared to static culture environments, our dynamic environment maintains islet cell viability at over 95 %, resulting in larger cell clusters that exhibit a higher tendency for aggregation up to 30 μm. Furthermore, the expression levels of key factors integral to islet development, namely INS-1, INS-2, and PDX-1, increased by 4.5-fold, 1.9-fold, and 5.8-fold respectively in the dynamic environment. Utilizing this sophisticated pancreas islet-on-a-chip model, we discovered that the consumption of sugar substitutes like erythritol and sucralose for 1 h does not impact insulin secretion levels. In contrast, the administration of glucagon-like peptide 1 (GLP-1), GLP-1 receptor (GLP-1R) agonist exendin-4, curcumin, and a combination therapy group led to a substantial increase in insulin secretion levels (p < 0.01). Such engineered microenvironments and pancreatic islet-on-chips offer a groundbreaking platform for evaluating sugar substitutes and antidiabetic compounds.

High-throughput 3D microfluidic chip for generation of concentration gradients and mixture combinations

Concentration gradient generation and mixed combinations of multiple solutions are of great value in the field of biomedical research. However, existing concentration gradient generators for single or two-drug solutions cannot simultaneously achieve multiple concentration gradient formations and mixed solution combinations. Furthermore, the whole system was huge, and required expensive auxiliary equipment, which may lead to complex operations. To address this problem, we devised a novel 3D microchannel network design, which is capable of creating all the desired mixture combinations and concentration gradients of given small amounts of the input solutions. As a proof of concept, the device we presented was verified by both colorimetric and fluorescence detection methods to test the efficiency. This can enable the implementation of one to three solutions with no driving pump and facilitate unique multiple types of more concentration gradients and mixture combinations in a single operation. We envision that this will be a promising candidate for the development of simplified methods for screening of the appropriate concentration and combination, such as various drug screening applications.

The Physics and Manipulation of Dean Vortices in Single- and Two-Phase Flow in Curved Microchannels: A Review

Microchannels with curved geometries have been employed for many applications in microfluidic devices in the past decades. The Dean vortices generated in such geometries have been manipulated using different methods to enhance the performance of devices in applications such as mixing, droplet sorting, and particle/cell separation. Understanding the effect of the manipulation method on the Dean vortices in different geometries can provide crucial information to be employed in designing high-efficiency microfluidic devices. In this review, the physics of Dean vortices and the affecting parameters are summarized. Various Dean number calculation methods are collected and represented to minimize the misinterpretation of published information due to the lack of a unified defining formula for the Dean dimensionless number. Consequently, all Dean number values reported in the references are recalculated to the most common method to facilitate comprehension of the phenomena. Based on the converted information gathered from previous numerical and experimental studies, it is concluded that the length of the channel and the channel pathline, e.g., spiral, serpentine, or helix, also affect the flow state. This review also provides a detailed summery on the effect of other geometric parameters, such as cross-section shape, aspect ratio, and radius of curvature, on the Dean vortices' number and arrangement. Finally, considering the importance of droplet microfluidics, the effect of curved geometry on the shape, trajectory, and internal flow organization of the droplets passing through a curved channel has been reviewed.