Biomicrofluidics最新文献

Cardiovascular diseases are the leading cause of morbidity and mortality worldwide with numerous inflammatory cell etiologies associated with impaired cardiac function and heart failure. Inflammatory cardiomyopathy, also known as myocarditis, is an acquired cardiomyopathy characterized by inflammatory cell infiltration into the myocardium with a high risk of progression to deteriorated cardiac function. Recently, amidst the ongoing COVID-19 pandemic, the emergence of acute myocarditis as a complication of SARS-CoV-2 has garnered significant concern. Given its mechanisms remain elusive in conjunction with the recent withdrawal of previously FDA-approved antiviral therapeutics and prophylactics due to unexpected cardiotoxicity, there is a pressing need for human-mimetic platforms to investigate disease pathogenesis, model dysfunctional features, and support pre-clinical drug screening. Traditional in vitro models for studying cardiovascular diseases have inherent limitations in recapitulating the complexity of the in vivo microenvironment. Heart-on-a-chip technologies, combining microfabrication, microfluidics, and tissue engineering techniques, have emerged as a promising approach for modeling inflammatory cardiac diseases like myocarditis. This review outlines the established and emerging conditions of inflamed myocardium, identifying key features essential for recapitulating inflamed myocardial structure and functions in heart-on-a-chip models, highlighting recent advancements, including the integration of anisotropic contractile geometry, cardiomyocyte maturity, electromechanical functions, vascularization, circulating immunity, and patient/sex specificity. Finally, we discuss the limitations and future perspectives necessary for the clinical translation of these advanced technologies.

The development of a non-invasive method for measuring the internal fluid behavior and dynamics of microchannels in microfluidics poses critical challenges to biological research, such as understanding the impact of wall shear stress (WSS) in the growth of a bone-forming osteoblast. This study used the General Defocus Particle Tracking (GDPT) technique to develop a non-invasive method for quantifying the fluid velocity profile and calculated the WSS within a microfluidic chip. The GDPT estimates particle motion in a three-dimensional space by analyzing two-dimensional images and video captured using a single camera. However, without a lens to introduce aberration, GDPT is prone to error in estimating the displacement direction for out-of-focus particles, and without knowing the exact refractive indices, the scaling from estimated values to physical units is inaccurate. The proposed approach addresses both challenges by using theoretical knowledge on laminar flow and integrating results obtained from multiple analyses. The proposed approach was validated using computational fluid dynamics (CFD) simulations and experimental video of a microfluidic chip that can generate different WSS levels under steady-state flow conditions. By comparing the CFD and GDPT velocity profiles, it was found that the Mean Pearson Correlation Coefficient is 0.77 (max = 0.90) and the Mean Intraclass Correlation Coefficient is 0.66 (max = 0.82). The densitometry analysis of osteoblast cells cultured on the designed microfluidic chip for four days revealed that the cell proliferation rate correlates positively with the measured WSS values. The proposed analysis can be applied to quantify the laminar flow in microfluidic chip experiments without specialized equipment.

Rapid prototyping and fabrication of microstructure have been revolutionized by 3D printing, especially stereolithography (SLA) based techniques due to the superior spatial resolution they offer. However, SLA-type 3D printing faces intrinsic challenges in multi-material integration and adaptive Z-layer slicing due to the use of a vat and a mechanically controlled Z-layer generation. In this paper, we present the conceptualization of a novel paradigm which uses dynamic and multi-phase laminar flow in a microfluidic channel to achieve fabrication of 3D objects. Our strategy, termed "in situ 3D polymerization," combines in situ polymerization and co-flow aqueous two-phase systems and achieves slicing, polymerization, and layer-by-layer printing of 3D structures in a microchannel. The printing layer could be predicted and controlled solely by programming the fluid input. Our strategy provides generalizability to fit with different light sources, pattern generators, and photopolymers. The integration of the microfluidic channel could enable high-degree multi-material integration without complicated modification of the 3D printer.

In recent years, the allure of space exploration and human spaceflight has surged, yet the effects of microgravity on the human body remain a significant concern. Immune and red blood cells rely on hematic or lymphatic streams as their primary means of transportation, posing notable challenges under microgravity conditions. This study sheds light on the intricate dynamics of cell behavior when suspended in bio-fluid under varying gravitational forces. Utilizing the dissipative particle dynamics approach, blood and white blood cells were modeled, with gravity applied as an external force along the vertical axis, ranging from 0 to 2 g in parameter sweeps. The results revealed discernible alterations in the cell shape and spatial alignment in response to gravity, quantified through metrics such as elongation and deformation indices, pitch angle, and normalized center of mass. Statistical analysis using the Mann-Whitney U test underscored clear distinctions between microgravity (<1 g) and hypergravity (>1 g) samples compared to normal gravity (1 g). Furthermore, the examination of forces exerted on the solid, including drag, shear stress, and solid forces, unveiled a reduction in the magnitude as the gravitational force increased. Additional analysis through dimensionless numbers unveiled the dominance of capillary and gravitational forces, which impacted cell velocity, leading to closer proximity to the wall and heightened viscous interaction with surrounding fluid particles. These interactions prompted shape alterations and reduced white blood cell area while increasing red blood cells. This study represents an effort in comprehending the effects of gravity on blood cells, offering insights into the intricate interplay between cellular dynamics and gravitational forces.

Urinary and vascular catheters are among the most commonly used medical devices. However, infections caused by biofilm formation on the surface of catheters are a major cause of healthcare-associated infections. Traditional methods, such as using antimicrobials to prevent such infections, generally have short-term effects, and treatment is challenging owing to the emergence of antimicrobial-resistant bacteria. This review aims to evaluate the limitations of conventional catheter-related infection prevention efficacy, such as currently used antimicrobials, and analyze the efficacy and limitations of potential alternatives to prevent catheter-related infections that have not yet been commercialized, classified by the transition stages of biofilm formation. We intend to provide profound insights into the ideal technologies for preventing catheter-associated tract infections and present perspectives on future directions in this field.

In order to study Bacillus subtilis biofilm formation in microdroplets, we use microfluidics technology to make the droplets and confocal microscopy to capture bacterial movement and biofilm formation in the droplets. We develop a multi-target tracking methodology, using a YOLOv5 detector to identify cells and a DeepSORT algorithm to track cell movements. We find that Bacillus subtilis bacteria with autonomous migration and biofilm-forming ability prefer to cluster and swarm near the microdroplet surface, rather than in the droplet interior. Bacterial mobility depends on phenotype and spatial location within the droplet. The motile cells move about 3.5 times faster than the matrix-producing cells. When the cells are near the wall of the droplet, the direction of the motion of motile cells is along that wall. When the cells are inside the droplet, the direction of the motion of motile cells is disordered, i.e., there is no clear directional or goal-oriented movement. This contrast increases the cell contact probability and facilitates the formation of a Bacillus subtilis biofilm in the droplet. Furthermore, we develop a mathematical model to describe the motion behavior of Bacillus subtilis in microdroplets, which is useful for exploring the influence of motility on biofilm formation.

Encapsulation of a single (bio)particle into individual droplets (referred to as single encapsulation) presents tremendous potential for precise biological and chemical reactions at the single (bio)particle level. Previously demonstrated successful strategies often rely on the use of high flow rates, gel, or viscoelastic materials for initial cell ordering prior to encapsulation into droplets, which could potentially challenge the system's operation. We propose to enhance the single encapsulation rate by using a stratified flow structure to focus and pre-order the (bio)particles before encapsulation. The stratified flow structure is formed using two simple aqueous Newtonian fluids with a viscosity contrast, which together serve as the dispersed phase. The single encapsulation rate is influenced by many parameters, including fluid viscosity contrast, geometric conditions, flow conditions and flow rate ratios, and dimensionless numbers such as the capillary number. This study focuses on investigating the influences of these parameters on the focused stream of the stratified flow, which is key for single encapsulation. The results allow the proposal of a simple guideline that can be adopted to design droplet microfluidic chips with an improved single encapsulation rate demanded by a wide range of applications. The guideline was validated by performing the single encapsulation of mouse embryonic stem cells suspended in a gelatin-methacryloyl solution in individual droplets of phosphate buffer saline, achieving a single encapsulation efficiency of up to 70%.

Filamentous fungi and fungal-like organisms contribute to a wide range of important ecosystem functions. Evidence has shown the movement of liquid across mycelial networks in unsaturated environments, such as soil. However, tools to investigate liquid movement along hyphae at the level of the single cell are still lacking. Microfluidic devices permit the study of fungal and fungal-like organisms with cellular resolution as they can confine hyphae to a single optical plane, which is compatible with microscopy imaging over longer timescales and allows for precise control of the microchannel environment. The aim of this study was to develop a method that enables the visualization and quantification of liquid movement on hyphae of fungal and fungal-like microorganisms. For this, the fungal-fungal interaction microfluidic device was modified to allow for the maintenance of unsaturated microchannel conditions. Fluorescein-containing growth medium solidified with agar was used to track liquid transported by hyphae via fluorescence microscopy. Our key findings highlight the suitability of this novel methodology for the visualization of liquid movement by hyphae over varying time scales and the ability to quantify the movement of liquid along hyphae. Furthermore, we showed that at the cellular level, extracellular movement of liquid along hyphae can be bidirectional and highly dynamic, uncovering a possible link between liquid movement and hyphal growth characteristics. We envisage that this method can be applied to facilitate future research probing the parameters contributing to hyphal liquid movement and is an essential step for studying the phenomenon of fungal highways.

The physics of the effects of electric field on the desiccation of colloidal droplets, comprising of dispersed negatively charged nanoparticles [2 μl, 1(w/w. %)], are studied in a standard electrowetting-on-a-dielectric configuration. The extent of contact line pinning during evaporation is found to be a function of the magnitude of the applied voltage and quantified in terms of the dimensionless electrowetting number (η). The pinned contact line led to higher particle compaction as evidenced by the characterization of dried colloidal film thicknesses. Crack formation and their dynamics have been analyzed in detail to elicit the interplay of forces near the contact line region and on the compaction front. These aspects of crack formation are elucidated in the light of magnitude and polarity of the applied electric field. It is found to influence the crack front initiation velocity, the geometry, the number of cracks, and an attempt is made to explain the same via first principle-based approaches. Therefore, this study indicates the possibility of using electrowetting as a technique to fine-tune the crack formation behavior in thin colloidal films.

The scarcity of blood for transfusion purposes has been widely acknowledged. Surgical therapeutic processes, war zones, and post-disaster treatments demand a huge amount of blood. Modern-day laboratories also require blood for bioengineering experimentation. Therefore, an artificially devised solution capable of mimicking the blood functions from biological and engineering relevance would be a noteworthy discovery of contemporary science. The experience drawn from discarded century-old blood substitutes has led us to technologically more advanced present-day solutions, which are better at carrying out the physiological functions of blood. Aiming at safety, stability, non-toxicity, and compatibility in terms of immuno-response, a remarkable number of substitutes are being tried to mimic the physiological properties and functions of red blood cells, platelets, plasma, and white blood cells. Despite significant efforts and time devoted, for transfusion, no product so far has been able to replace natural blood. This article puts together the important developments in blood substitutes that have evolved over the years, including substitutes for clinical as well as engineering requirements. It also points out the recent endeavors of synthesizing blood cells through modern synthetic routes. It has been highlighted that none of the blood substitutes have achieved the required efficacy so that they can be used in vivo. Finally, the emerging trends and future research needs have been stressed upon.