Engineering a dynamic three-dimensional cell culturing microenvironment using a 'sandwich' structure-liked microfluidic device with 3D printing scaffold.

Most ofin vivotissue cells reside in 3D extracellular matrix (ECM) with fluid flow. To better study cell physiology and pathophysiology, there has been an increasing need in the development of methods for culturing cells inin vivolike microenvironments with a number of strategies currently being investigated including hydrogels, spheroids, tissue scaffolds and very promising microfluidic systems. In this paper, a 'sandwich' structure-liked microfluidic device integrated with a 3D printing scaffold is proposed for three-dimensional and dynamic cell culture. The device consists of three layers, i.e. upper layer, scaffold layer and bottom layer. The upper layer is used for introducing cells and fixing scaffold, the scaffold layer mimicking ECM is used for providing 3D attachment areas, and the bottom layer mimicking blood vessels is used for supplying dynamic medium for cells. Thermally assisted electrohydrodynamic jet (TAEJ) printing technology and microfabrication technology are combined to fabricate the device. The flow field in the chamber of device is evaluated by numerical simulation and particle tracking technology to investigate the effects of scaffold on fluid microenvironment. The cell culturing processes are presented by the flow behaviors of inks with different colors. The densities and viabilities of HeLa cells are evaluated and compared after 72 h of culturing in the microfluidic devices and 48-well plate. The dose-dependent cell responses to doxorubicin hydrochloride (DOX) are observed after 24 h treatment at different concentrations. These experimental results, including the evaluation of cell proliferation andin vitrocytotoxicity assessment of DOX in the devices and plate, demonstrate that the presented microfluidic device has good biocompatibility and feasibility, which have great potential in providing native microenvironments forin vitrocell studies, tissue engineering and drug screening for tumor therapy.

Sensitive immunoassay of cardiac troponin I using an optimized microelectrode array in a novel integrated microfluidic electrochemical device.

A sensitive and portable microfluidic electrochemical array device (µFED) was developed for the immunoassay of trace amounts of human cardiac troponin I (cTnI), which is an attractive biomarker for acute myocardial infarction (AMI). The classical "sandwich" method was adopted for the immunoassay. The capture antibody was immobilized using a self-assembled monolayer (SAM) technique, and the process was reorganized to be compatible with the bonding process. The detection antibody was labeled with alkaline phosphatase (AP) for signal amplification. The performance of the µFED was improved by eliminating the shielding effect of the microelectrode array (MEA) integrated in the µFED. The effects of the interstice and the width of the MEA on the response peak current were analyzed and simulated. The concentration gradient, about 3% of the gradient at the surface, was considered as the criterion for estimation of the optimal interstice between electrodes, and its effectiveness was proved. A stable and miniaturized reference electrode was integrated in the µFED, and its potential deviation was less than 5 mV in 15 min. These efforts resulted in the enhanced immunoassay performance of the µFED. A low limit of detection of about 5 pg/mL was obtained in serum samples, and the response current was proportional to the logarithm of concentration from 50 pg/mL to 1 µg/mL. The immunoassay process was accomplished in 15 min. The µFED was thus qualified and is a promising candidate for point-of-care immunoassay of cTnI. Graphical abstract.

A microfluidic design to provide a stable and uniform in vitro microenvironment for cell culture inspired by the redundancy characteristic of leaf areoles.

The leaf venation is considered to be an optimal transportation system with the mesophyll cells being divided by minor veins into small regions named areoles. The transpiration of water in different regions of a leaf fluctuates over time making the transportation of water in veins fluctuate as well. However, because of the existence of multiple paths provided by the leaf venation network and the pits on the walls of the vessels, the pressure field and nutrient concentration in the areoles that the mesophyll cells live in are almost uniform. Therefore, inspired by such structures, a microfluidic design of a novel cell culture chamber has been proposed to obtain a stable and uniform microenvironment. The device consists of a novel microchannel system imitating the vessels in the leaf venation to transport the culture medium, a cell culture chamber imitating the areole and microgaps imitating the pits. The effects of the areole and pit on flow fields in the cell culture chamber have been discussed. The results indicate that the bio-inspired microfluidic device is a robust platform to provide an in vivo like fluidic microenvironment.