Cell culture using centrifugal microfluidic platform with demonstration on Pichia pastoris

Open and closed microfluidics for biosensing

Biosensing is vital for many areas like disease diagnosis, infectious disease prevention, and point-of-care monitoring. Microfluidics has been evidenced to be a powerful tool for biosensing via integrating biological detection processes into a palm-size chip. Based on the chip structure, microfluidics has two subdivision types: open microfluidics and closed microfluidics, whose operation methods would be diverse. In this review, we summarize fundamentals, liquid control methods, and applications of open and closed microfluidics separately, point out the bottlenecks, and propose potential directions of microfluidics-based biosensing.

Film-Shaped Self-Powered Electro-Osmotic Micropump Array

This paper reports a new concept of a film-shaped micropump array for biomedical perfusion. The detailed concept, design, fabrication process, and performance evaluation using prototypes are described. In this micropump array, an open circuit potential (OCP) is generated by a planar biofuel cell (BFC), which in turn generates electro-osmotic flows (EOFs) in multiple through-holes arranged perpendicular to the micropump plane. The micropump array is thin and wireless, so it can be cut like postage stamps, easily installed in any small location, and can act as a planar micropump in solutions containing the biofuels glucose and oxygen. Perfusion at local sites are difficult with conventional techniques using multiple separate components such as micropumps and energy sources. This micropump array is expected to be applied to the perfusion of biological fluids in small locations near or inside cultured cells, cultured tissues, living organisms, and so on.

Monolithically 3D-Printed Microfluidics with Embedded µTesla Pump

Microfluidics has earned a reputation for providing numerous transformative but disconnected devices and techniques. Active research seeks to address this challenge by integrating microfluidic components, including embedded miniature pumps. However, a significant portion of existing microfluidic integration relies on the time-consuming manual fabrication that introduces device variations. We put forward a framework for solving this disconnect by combining new pumping mechanics and 3D printing to demonstrate several novel, integrated and wirelessly driven microfluidics. First, we characterized the simplicity and performance of printed microfluidics with a minimum feature size of 100 µm. Next, we integrated a microtesla (µTesla) pump to provide non-pulsatile flow with reduced shear stress on beta cells cultured on-chip. Lastly, the integration of radio frequency (RF) device and a hobby-grade brushless motor completed a self-enclosed platform that can be remotely controlled without wires. Our study shows how new physics and 3D printing approaches not only provide better integration but also enable novel cell-based studies to advance microfluidic research.

An integrated microfluidic detection system for the automated and rapid diagnosis of high-risk human papillomavirus

Human papillomavirus (HPV) causes the prevalent sexually transmitted infection that accounts for the majority of cervical cancer incidences. Therefore, the development of a rapid, accurate, automatic and affordable nucleic acid detection strategy is urgently required for HPV tests, among which microfluidic chip is a promising diagnostic method. In this work, we developed a microfluidic detection system consisting of a microfluidic chip and the corresponding detection equipment to diagnose high-risk HPV. The proposed method integrates nucleic acid purification, isothermal amplification and real-time fluorescence detection into one device. Moreover, it demonstrates good detection performance such as high specificity of primer sets (100%) and exceptional stability (coefficient of variation <6%) among five HPV genotypes. Besides, the microfluidic loop-mediated isothermal amplification (LAMP) assay is accurate (specificity of 91.7% and sensitivity of 100%) and fast (average time threshold = 10.56 minutes) when considering the conventional qPCR assay as the gold standard. The integrated microfluidic detection system offers automated and rapid diagnosis within 40 minutes and shows broad potential to deliver point-of-care detection in resource-limited circumstances owing to its simplicity and affordability.

Evaluation of the anti-bacterial activity of methanolic extract of Chlorella vulgaris Beyerinck [Beijerinck] with special reference to antioxidant modulation

Background

The natural antioxidants from Chlorella have potent therapeutic implication in several diseases. However, the anti-bacterial activity and their molecular mode of action have not been investigated yet. The present study focussed on the assessment of antioxidant potential as well as free radical scavenging activity such as DPPH, hydroxyl radical, hydrogen peroxide, and superoxide anion radical assay of Chlorella vulgaris Beyerinck [Beijerinck] (BUACC25) isolated from marine habitat. Furthermore, the anti-bacterial activity and their molecular mode of action have been evaluated.

Results

In the present study, the preliminary phytochemical screening of methanolic algal extract revealed the presence of alkaloids, glycosides, proteins, terpenoids, saponins, coumarin, phenols, and tannins, which was confirmed by in an UV-visible and FT-IR spectroscopy, indicated the distinct spectral peaks. The methanolic algal extract was found to be rich in phenolic content (45 ± 0.06 mg GAE g−1) and flavonoid content (470 ± 0.25 mg of RUE g−1). Furthermore, the methanolic extract was revealed potent antioxidant scavenging activity to scavenge various free radicals with minimum IC50 values of DPPH, hydroxyl, H2O2, superoxide 2.82 ± 0.30, 2.30 ± 0.25, 3.24 ± 0.32, and 3.15 ± 0.02 μg ml−1 respectively. Furthermore, the methanolic extract of C. vulgaris exhibited potent anti-bacterial activity which was evident with the reduction in cfu × 107/ml and % of cell viability. Mechanistically, reduction of SOD, CAT, and GSH activity provoked ROS-mediated cell death after drug treatment. Moreover, in combination with norfloxacin and ciprofloxacin, methanolic extract of C. vulgaris demonstrated enhanced anti-bacterial activity with an evident reduction in cfu/ml and % of cell viability.

Conclusion

This study advocates that C. vulgaris (BUACC25) has promising antioxidant activity owing to the presence of phenolic and flavonoids evidenced by scavenging of DPPH, hydroxyl, H2O2, and superoxide radicals. In addition to this, it sustained anti-microbial activity against E. coli through modulation of SOD, CAT, and GSH. This study carved a path for uncovering a better therapeutic agent against disease-causing bacterial pathogens.

Frequency dependent multiphase flows on centrifugal microfluidics

The simultaneous flow of gas and liquids in large scale conduits is an established approach to enhance the performance of different working systems under critical conditions. On the microscale, the use of gas-liquid flows is challenging due to the dominance of surface tension forces. Here, we present a technique to generate common gas-liquid flows on a centrifugal microfluidic platform. It consists of a spiral microchannel and specific micro features that allow for temporal and local control of stratified and slug flow regimes. We investigate several critical parameters that induce different gas-liquid flows and cause the transition between stratified and slug flows. We have analytically derived formulations that are compared with our experimental results to deliver a general guideline for designing specific gas-liquid flows. As an application of the gas-liquid flows in enhancing microfluidic systems' performance, we show the acceleration of the cell growth of E. coli bacteria in comparison to traditional culturing methods.

CD-Based Microfluidics for Primary Care in Extreme Point-of-Care Settings

We review the utility of centrifugal microfluidic technologies applied to point-of-care diagnosis in extremely under-resourced environments. The various challenges faced in these settings are showcased, using areas in India and Africa as examples. Measures for the ability of integrated devices to effectively address point-of-care challenges are highlighted, and centrifugal, often termed CD-based microfluidic technologies, technologies are presented as a promising platform to address these challenges. We describe the advantages of centrifugal liquid handling, as well as the ability of a standard CD player to perform a number of common laboratory tests, fulfilling the role of an integrated lab-on-a-CD. Innovative centrifugal approaches for point-of-care in extremely resource-poor settings are highlighted, including sensing and detection strategies, smart power sources and biomimetic inspiration for environmental control. The evolution of centrifugal microfluidics, along with examples of commercial and advanced prototype centrifugal microfluidic systems, is presented, illustrating the success of deployment at the point-of-care. A close fit of emerging centrifugal systems to address a critical panel of tests for under-resourced clinic settings, formulated by medical experts, is demonstrated. This emphasizes the potential of centrifugal microfluidic technologies to be applied effectively to extremely challenging point-of-care scenarios and in playing a role in improving primary care in resource-limited settings across the developing world.

Numerical Investigation of Cell Encapsulation for Multiplexing Diagnostic Assays Using Novel Centrifugal Microfluidic Emulsification and Separation Platform

In the present paper, we report a novel centrifugal microfluidic platform for emulsification and separation. Our design enables encapsulation and incubation of multiple types of cells by droplets, which can be generated at controlled high rotation speed modifying the transition between dripping-to-jetting regimes. The droplets can be separated from continuous phase using facile bifurcated junction design. A three dimensional (3D) model was established to investigate the formation and sedimentation of droplets using the centrifugal microfluidic platform by computational fluid dynamics (CFD). The simulation results were compared to the reported experiments in terms of droplet shape and size to validate the accuracy of the model. The influence of the grid resolution was investigated and quantified. The physics associated with droplet formation and sedimentation is governed by the Bond number and Rossby number, respectively. Our investigation provides insight into the design criteria that can be used to establish centrifugal microfluidic platforms tailored to potential applications, such as multiplexing diagnostic assays, due to the unique capabilities of the device in handling multiple types of cells and biosamples with high throughput. This work can inspire new development of cell encapsulation and separation applications by centrifugal microfluidic technology.

Flow-induced stress on adherent cells in microfluidic devices

Transduction of mechanical forces and chemical signals affect every cell in the human body. Fluid flow in systems such as the lymphatic or circulatory systems modulates not only cell morphology, but also gene expression patterns, extracellular matrix protein secretion and cell-cell and cell-matrix adhesions. Similar to the role of mechanical forces in adaptation of tissues, shear fluid flow orchestrates collective behaviours of adherent cells found at the interface between tissues and their fluidic environments. These behaviours range from alignment of endothelial cells in the direction of flow to stem cell lineage commitment. Therefore, it is important to characterize quantitatively fluid interface-dependent cell activity. Common macro-scale techniques, such as the parallel plate flow chamber and vertical-step flow methods that apply fluid-induced stress on adherent cells, offer standardization, repeatability and ease of operation. However, in order to achieve improved control over a cell's microenvironment, additional microscale-based techniques are needed. The use of microfluidics for this has been recognized, but its true potential has emerged only recently with the advent of hybrid systems, offering increased throughput, multicellular interactions, substrate functionalization on 3D geometries, and simultaneous control over chemical and mechanical stimulation. In this review, we discuss recent advances in microfluidic flow systems for adherent cells and elaborate on their suitability to mimic physiologic micromechanical environments subjected to fluid flow. We describe device design considerations in light of ongoing discoveries in mechanobiology and point to future trends of this promising technology.