In previous volume, we have discussed different ways of incubators regulating the temperature and gas content of its inner chamber. In this volume, we will comprehensively look over how the size, water reservoir, and cell imaging system could differentiate a biological incubator from one another based on different needs.
Freezer-like incubator: Freezer-like incubators usually range from 30 cubic feet to 60 cubic feet.
- Freezer-like incubators have a large capacity which comes particularly handy for High-volume tissue culture study and engineering (e.g. tissue regeneration, biomaterial, and cell harvesting).
- A large capacity of incubator also implies higher compatibility of in-incubator apparatus (e.g. microscope and roller bottle apparatus).
- To keep the uniformity in temperature, Freezer-like incubators are usually equipped with high-sensitive temperature sensors and large surface-area heaters. Therefore, a freezer-like incubator is not necessarily cheaper than a few benchtop incubators combined.
- The nature of a freezer-like incubator doesn’t meet the needs of most frontline cellular research today. Freezer-like incubators are not an ideal choice for experiments involving more than one type of cell line and incubation conditions in addition to a higher risk of cross-contamination.
Benchtop incubators usually have a way smaller footprint so that they can be placed on the benchtop. The volume of the internal chamber can be less than 0.5 cu.ft.
- A compact design makes the benchtop incubator more power-efficient, which is ideal for labs with a little budget.
- Benchtop incubators are usually more efficient than their counterparts, a smaller chamber size secures the uniformity in temperature and humidity.
- Bench-top incubators give researchers an option to customize the incubation environment based on different cell types. An experiment-dedicated incubator allows a lower chance of cross-contamination.
💡 Bench-top incubators generally possess a modular, stackable design, assuring a higher customization between different experiments yet a lower contamination rate.
💡 Tip: cross-contamination can be a huge issue when comes to share the incubator with other labs. Check out our rationale on why you should never share your incubators!
Water Reservoir Explained:
The difference between internal water reservoirs and the external one lies between whether they have direct contact with the internal chamber.
Internal Water Reservoir.
Internal water reservoir can be a removable water pan or a built-in water container usually installed underneath the bottom shelf.
- Internal water reservoirs fulfill the need of most cellular research. It directly provides the inner chamber with high relative humidity (RH) and fast recovery rate.
- A removable, metal water pan eventually allows researchers to decontaminate the water container regularly; for instance, weekly disinfection of the water pan and the placement of a piece of pure copper metal in the water pan can both effectively repress the microbial activity within the chamber.
- Without a humidity monitoring system installed, there is certain risk for cell sample desiccation.
External Water Reservoir.
External water reservoir is usually placed outside the inner chamber, then the water tank and the inner chamber is connected via a valve.
- The extra valve gives the incubator the ability to actively control the RH.
- An external water tank also enables researchers to refill the water without disrupting the cell culture in the chamber.
- Incubators with external water reservoirs, however, tend to face a higher chance of contamination in the long run. The water input channel (i.e. Valve and tubes) cannot be directly disinfected as what can be done on internal water reservoirs (i.e. removable components).
💡 Tip: To effectively prevent sample desiccation? Incubators with real-time RH monitoring and reporting systems can make it possible!
Live Cell Imaging Explained:
In-incubator cell imaging is something way overdue. To observe the cellular image in real-time without disrupting the incubation environment, scientists have been trying to stuff the incubators with imaging systems. Two popular cell imaging systems appear in the incubator: Brightfield and Phase-contrast.
In order to mimic in-vivo conditions, the CO2 tension within the chamber must be different from the atmosphere. In addition, Different cell lines require different optimum [CO2]. A previously regulated [CO2] is essential to sustain the PH of cell culture.
- Brightfield microscopy is simple and cheap
- Brightfield microscopy doesn’t change the color of cell samples, it is ideal for observing samples involved in vivo staining
- Brightfield images tend to have lower contrast and details, and the image quality can be varied depending on different cell types; Studies focus on living cell morphology or organoid activities shall look for more advanced microscopy.
Phase-contrast microscopy was born during the revolutionary time of biomedical and molecular research in 1934. The working principle behind Phase-contrast microscopy is rather complicated. Long story short, it leverages optical condenser and phase plates to magnify the difference of refractive indices between different media, then translating the differences as grayscale intensity
- Phase-contrast allows observing transparent samples, saving the time and risk to stain the cell culture
- Images captured via Phase-contrast have higher contrast and sharpness, which is optimal for studying cellular and organoid structures
- Despite delivering a sufficient amount of structure, Phase-contrast microscopy is not capable of illustrating the color information of the sample. To overcome this drawback, Phase-contrast microscopies can be coupled with Fluorescence filters to visualize fluorescent-labeled samples/cellular structure.
- Due to its working principle, phase-contrast microscopes have more constraints on the thickness of the sample.
This Figure compares a brightfield model (left) with a phase-contrast model (right) of the same unstained simple squamous epithelial cells .
💡 Read More: Why current solution on live cell imaging sucks? Hearing the confession from a PhD student!
Doing cellular research doesn’t have to suffer. The development of open-source platforms, data sharing, protocol automation, and machine learning has empowered scientists to simplify the experience of studying cell cultures.
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Figure credit:  Parker, N., Mark Schneegurt, A., Lister, P., & Forster, B. (2016, November 01). Instruments of Microscopy. Retrieved June 03, 2020, from https://opentextbc.ca/microbiologyopenstax/chapter/instruments-of-microscopy/