Organ on a chip - Dan Nguyen

Introduction

One application of microfluidic devices is called organ-on-a-chip. Organ-on-a-chip is a small-scaled multichannel 3-dimensional device that can �imitate and reconstitute the structures and hopefully fully perform the functions of �the living organs/tissues of a human body. Building different organ-on-a-chips that mimic a variety of human organs is believed to be the possible substitution to the traditional 2-dimensional cell culture techniques and animal testing (1).

== Overview of an Organ-on-a-chip Human organs are very complex units as each organ has different structures and contains different tissues and different types of cells. Hence traditional in vitro cell culture cannot yield satisfying results as it fails to correctly reconstitute a fully functional nature of a human body. Animal testing also Organ-on-a-chips are often considered not accurate as well due to the animal models mostly fail to correctly predict the drug effects of drugs on humans. Organ-on-a-chips open to new possibilities as they are targeted and developed to simulate near-to-perfect structures and functions of different organs. Polymeric Polydimethylsiloxane (PDMS) is usually used to fabricate the inner microchannels and chambers of the microfluidic devices as its flexibility can imitate healthy blood vessels and air channels. To better �fabricate the human organs, physiological conditions are taken into account while operating the devices such as fluid pH, cell culture medium, nutrient concentrations are monitored through pumps and valves in the microfluidic device (2).

Different microfluidic devices that imitate lungs, kidneys, hearts or guts have been broadly researched. The general steps to create a specific organ on a chip are principally the same. The first steps are to design, mold and sterilize the device. Specific types of cells for the organ chips are perfused to the device with culture media through small inlets that are connected to small tubings. Cells are continuously grown inside the chip in a sterile environment. The model is often screened under the microscope for cell population check and once the cells divide enough, the chips will go through chemical tests such as cancer drug testing and drug screening (4).

Integration of multiple organ on a chip - Human on a chip

Once multiple organs-on-a-chips are perfectly developed and extensively tested, an integration of multiple organ-on-a-chips would be the final goal to work on. Human-on-a-chip is one of the most important and most promising alternatives to animal testing as a human-on-a-chip is expected to perform as an entire human organ system (such as digestive system, respiratory system, cardiovascular system and so on) or even further, an entire living human. However, there are many challenges for the integration of all organ-on-a-chips because we have to ensure that once different chips are connected, they must support others like how human tissues support each other. Supporting computational models are needed to design an entire integration of organ-on-a-chips. In addition, developing a human-on-a-chip requires much more donated human cells and human materials (such as human bones) which are very expensive to get for research. Despite the challenges, human-on-a-chip is still a brilliant idea to be considered as once those human-on-a-chips become true, medical researches such as cancer treatment or drug testing no longer have to depend on animal testing.

References

1. Sosa-Hernández, J. E., Villalba-Rodríguez, A. M., Romero-Castillo, K. D., Aguilar-Aguila-Isaías, M. A., García-Reyes, I. E., Hernández-Antonio, A., . . . Iqbal, H. M. (2018). Organs-on-a-Chip Module: A Review from the Development and Applications Perspective. Micromachines, 9(10), 536. doi:10.3390/mi9100536
2. Aziz, A., Geng, C., Fu, M., Yu, X., Qin, K., & Liu, B. (2017). The Role of Microfluidics for Organ on Chip Simulations, 4(4), 39. doi:10.3390/bioengineering4020039
3. Marturano-Kruik, A., Nava, M. M., Yeager, K., Chramiec, A., Hao, L., Robinson, S., . . . Vunjak-Novakovic, G. (2018). Human bone perivascular niche-on-a-chip for studying metastatic colonization, 115(6), 1256-1261. doi:10.1073/pnas.1714282115
4. Huh, D. (2015). A Human Breathing Lung-on-a-Chip, 12(1), S42-S44. doi:10.1513/annalsats.201410-442mg