Development of a Microfluidic Device to Form a Long Chemical Gradient in a Tissue from Both Ends with an Analysis of Its Appearance and Content

Local Microbubble Removal in Polydimethylsiloxane Microchannel by Balancing Negative and Atmospheric Pressures

Long-term experiments using organoids and tissues are crucial for drug development. Microfluidic devices have been regularly used in long-term experiments. However, microbubbles often form in these devices, and they may damage and starve cells. A method involving the application of negative pressure has been reported to remove microbubbles from microfluidic devices composed of polydimethylsiloxane; however, negative pressure affects the cells and tissues in microfluidic devices. In this study, a local microbubble removal method was developed using a microfluidic device with 0.5 mm thin polydimethylsiloxane sidewalls. The thin sidewalls counterbalanced the negative and atmospheric pressures, thereby localizing the negative pressure near the negatively pressurized chamber. Microbubbles were removed within 5 mm of the negatively pressurized chamber; however, those in an area 7 mm and more from the chamber were not removed. Using the local removal method, a long-term perfusion test was performed, and no contact was confirmed between the bubbles and the simulated tissue for 72 h.

Microfluidic Distillation System for Separation of Propionic Acid in Foods

A microfluidic distillation system is proposed to facilitate the separation and subsequent determination of propionic acid (PA) in foods. The system comprises two main components: (1) a polymethyl methacrylate (PMMA) micro-distillation chip incorporating a micro-evaporator chamber, a sample reservoir, and a serpentine micro-condensation channel; and (2) and a DC-powered distillation module with built-in heating and cooling functions. In the distillation process, homogenized PA sample and de-ionized water are injected into the sample reservoir and micro-evaporator chamber, respectively, and the chip is then mounted on a side of the distillation module. The de-ionized water is heated by the distillation module, and the steam flows from the evaporation chamber to the sample reservoir, where it prompts the formation of PA vapor. The vapor flows through the serpentine microchannel and is condensed under the cooling effects of the distillation module to produce a PA extract solution. A small quantity of the extract is transferred to a macroscale HPLC and photodiode array (PDA) detector system, where the PA concentration is determined using a chromatographic method. The experimental results show that the microfluidic distillation system achieves a distillation (separation) efficiency of around 97% after 15 min. Moreover, in tests performed using 10 commercial baked food samples, the system achieves a limit of detection of 50 mg/L and a limit of quantitation of 96 mg/L, respectively. The practical feasibility of the proposed system is thus confirmed.

Mini Bioreactor Can Support In Vitro Spermatogenesis of Mouse Testicular Tissue

Objective

It was in the early 20^th century when the quest for in vitro spermatogenesis started. In vitro spermatogenesis is critical for male cancer patients undergoing gonadotoxic treatment. Dynamic culture system creates in vivo-like conditions. In this study, it was intended to evaluate the progression of spermatogenesis after testicular tissue culture in mini-perfusion bioreactor.

Materials and Methods

In this experimental study, 12 six-day postpartum neonatal mouse testes were removed and fragmented, placed on an agarose gel in parallel to bioreactor culture, and incubated for 8 weeks. Histological, molecular and immunohistochemical evaluations were carried out after 8 weeks.

Results

Histological analysis suggested successful maintenance of spermatogenesis in tissues grown in the bioreactor but not on agarose gel, possibly because the central region did not receive sufficient oxygen and nutrients, which led to necrotic or degenerative changes. Molecular analysis indicated that Plzf, Tekt1 and Tnp1 were expressed and that their expression did not differ significantly between the bioreactor and agarose gel. Immunohistochemical evaluation of testis fragments showed that PLZF, SCP3 and ACRBP proteins were expressed in spermatogonial cells, spermatocytes and spermatozoa. PLZF expression after 8 weeks was significantly lower (P<0.05) in tissues incubated on agarose gel than in the bioreactor, but there was no significant difference between SCP3 and ACRBP expression among the bioreactor and agarose gel culture systems.

Conclusion

This three-dimensional (3D) dynamic culture system can provide somewhat similar conditions to the physiological environment of the testis. Our findings suggest that the perfusion bioreactor supports induction of spermatogenesis for generation of haploid cells. Further studies will be needed to address the fertility of the sperm generated in the bioreactor system..