No abstract

This study reports a new perfusion-based, micro three-dimensional (3-D) cell culture platform for high-throughput cell culture using enabling microfluidic technologies. In this work, the micro 3-D cell culture platform is fabricated based on SU-8 lithography and polydimethylsiloxane replication processes. The micro cell culture platform can maintain homogenous and stable culture environments, as well as provide pumping of multiple mediums and efficient cell/agarose (scaffold) loading functions, which allows realization of more precise and high-throughput cell culture-based assays. In this study, the design of a high-throughput medium pumping mechanism was especially highlighted. A new serpentine-shaped pneumatic micropump was used to provide the required medium pumping mechanism. Pneumatic microchannels with a varied length and U-shape bending corners were designed to connect three rectangular pneumatic chambers such that one can fine-tune the pumping rate of the S-shape micropump by using the fluidic resistance. To achieve a high-throughput medium pumping function, a pneumatic tank was designed to simultaneously activate all of the 30 pneumatic micropumps with a uniform pumping rate. Results show that the pumping rates of the 30 integrated micropumps were statistically uniform with a flow rate ranging from 8.5 to 185.1 microl h(-1), indicating the present multiple medium pumping mechanism is feasible for high-throughput medium delivery purposes. Furthermore, as a demonstration case study, 3-D culture of oral cancer cell was successfully performed, showing that the cell viability remained as high as 95% - 98% during the 48 h cell culture. As the result of miniaturization, this perfusion-based 3-D cell culture platform not only provides a well-defined and stable culture condition, but also greatly reduces the sample/reagent consumption and the need for human intervention. Moreover, due to the integrated capability for multiple medium pumping, high-throughput research work can be achieved. These traits are found particularly useful for high-precision and high-throughput, 3-D cell culture-based assay.

Stem cells with the capability to self-renew and differentiate into multiple cell derivatives provide platforms for drug screening and promising treatment options for a wide variety of neural diseases. Nevertheless, clinical applications of stem cells have been hindered partly owing to a lack of standardized techniques to characterize cell molecular profiles noninvasively and comprehensively. Here, we demonstrate that a label-free and noninvasive single-cell Raman microspectroscopy (SCRM) platform was able to identify neural cell lineages derived from clinically relevant human induced pluripotent stem cells (hiPSCs). By analyzing the intrinsic biochemical profiles of single cells at a large scale (8,774 Raman spectra in total), iPSCs and iPSC-derived neural cells can be distinguished by their intrinsic phenotypic Raman spectra. We identified a Raman biomarker from glycogen to distinguish iPSCs from their neural derivatives, and the result was verified by the conventional glycogen detection assays. Further analysis with a machine learning classification model, utilizing t-distributed stochastic neighbor embedding (t-SNE)-enhanced ensemble stacking, clearly categorized hiPSCs in different developmental stages with 97.5% accuracy. The present study demonstrates the capability of the SCRM-based platform to monitor cell development using high content screening with a noninvasive and label-free approach. This platform as well as our identified biomarker could be extensible to other cell types and can potentially have a high impact on neural stem cell therapy.

This paper reports a new membrane-based pneumatic micropump with new serpentine-shape (S-shape) pneumatic channels intended for achieving high-throughput pumping in a microfluidic system at a relatively low pumping rate and a board flow rate range. The key feature of this design is the ability to modulate the pumping rates by fine-tuning the fluidic resistance of injected compressed air in the designed pneumatic microchannels and the chambers of the micropump. In the study, several S-shape pneumatic micropumps with various layouts were designed and fabricated based on thick-film photoresist lithography and polydimethylsiloxane (PDMS) replication processes. To investigate designs with a suitable pumping performance, S-shape pneumatic micropumps with varied lengths (1000, 5000 and 10 000 µm), varied widths (20, 40 and 200 µm) of the pneumatic microchannel bridging two rectangular pneumatic chambers, and different numbers of pneumatic channel bends (two and four U-shape bends) were designed and evaluated experimentally by using high-speed CCD-coupled microscopic observation of the movement of PDMS membrane pulsation and pumping rate measurements. The results revealed that under the experimental conditions studied, the layout of the S-shape pneumatic micropump with three rectangular pneumatic chambers, 5000 µm long and 40 µm wide pneumatic microchannel and four U-shape bends in the pneumatic microchannel was found to be capable of providing a broader pumping rate range from 0 to 539 µl h −1 compared to the other designs. As a whole, the experimental results demonstrate the use of fluidic resistance of injected air in a pneumatic micropump with S-shape layout to control its pumping performance, which largely expands the flexibility of its pumping application in a microfluidic system.

Articular cartilage has a limited capacity for self-repair after damage. Engineered cartilage is a promising treatment to replace or repair damaged tissue. The growth of engineered cartilage is sensitive to the extracellular culture environment. Chondrocytes were seeded into alginate beads and agarose scaffolds at 4 millions/mL, and the response to static and perfusion culture was examined over period of up to 12 days. For both types of scaffolds, the chondrocytes kept their differentiated morphology over 12 days in all culture conditions. In alginate beads, more glycosaminoglycans (GAGs) were produced in perfusion culture than in static conditions. GAG distribution in alginate constructs was more uniform in perfusion culture than in static culture. However, in agarose constructs there was no significant difference in GAG production between static culture and perfusion culture. Under perfusion culture, the retention rate of GAG in alginate was higher than in agarsoe. It is suggested that the positive effect of perfusion culture only can be achieved by an appropriate choice of other factors such as scaffold materials.