PDMS-based porous membrane for medical applications: design, development, and fabrication.

Organ-on-a-chip (OoC) is one of the most popular microfluidic chips and possesses various industrial, biomedical, and pharmaceutical applications. So far, many types of OoCs with different applications have been fabricated, most of which contain porous membranes useful as cell culture substrates. One of the challenging parts of OoC's chips is porous membrane fabrication, making it a complex and sensitive process, which is an issue in microfluidic design. These membranes are made of various materials, the same as biocompatible polymer polydimethylsiloxane (PDMS). Besides OoC, these PDMS membranes can be applied in diagnosis, cell separating, trapping, and sorting. In the present study, a new approach has been presented to design and fabricate an efficient porous membrane in terms of time and cost. The fabrication method has fewer steps than previous techniques and employs more conventional approaches. The presented method for membrane fabrication is functional and a novel way to continue producing this product with a single mold and peeling off the membrane on each try. Merely one sacrificial layer (polyvinyl alcohol) and an O2plasma surface treatment have been used for fabrication. Surface modification and sacrificial layer on the mold ease the peeling of the PDMS membrane. Transferring process of the membrane to the OoC device is explained, and a filtration test is presented to show the functionality of the PDMS membranes. Cell viability is investigated by MTT assay to ensure the PDMS porous membranes are suitable for microfluidic devices. Also, cell adhesion, cell count, and confluency are analyzed, showing almost the same results for the PDMS membranes and the control samples.

Electrochemical generation of microbubbles by carbon nanotube interdigital electrodes to increase the permeability and material uptakes of cancer cells.

Artificial cavitation as a prerequisite of sonoporation, plays an important role on the ultrasound (US) assisted drug delivery systems. In this study, we have proposed a new method of microbubble (MB) generation by local electrolysis of the medium. An integrated interdigital array of three-electrode system was designed and patterned on a nickel-coated quartz substrate and then, a short DC electrical pulse was applied that consequently resulted in distributed generation of microbubbles at the periphery of the electrodes. Growth of the carbon nanotube (CNT) nanostructures on the surface of the electrodes approximately increased the number of generated microbubbles up to 7-fold and decreased their average size from ∼20 µm for bare to ∼7 µm for CNT electrodes. After optimizing the three-electrode system, biocompatibility assays of the CNT electrodes stimulated by DC electrical micropulses were conducted. Finally, the effect of the proposed method on the sonoporation efficiency and drug uptake of breast cells were assessed using cell cycle and Annexin V/PI flow cytometry analysis. These results show the potential of electrochemical generation of MBs by CNT electrodes as an easy, available and promising technique for artificial cavitation and ultrasound assisted drug delivery.