Human-made mini brains now have mini electrodes, thanks to this study

Electroencephalography (EEG) caps are medical devices doctors use to diagnose brain disorders like epilepsy and seizures in patients. In the past decade, scientists have created 3D mini-brains called brain organoids from human-derived stem cells that mimic some aspects of brain development. A team of researchers at John Hopkins University has recently developed the world’s smallest EEG caps to study these more efficiently. The micro EEG caps can be used on a brain organoid the size of a pen dot.

Brain organoids can mimic some key features of the human brain. Scientists create them to understand the human brain’s development process and the factors leading to various neural disorders. Moreover, such mini-brains can also be used to perform experiments that researchers would have to otherwise perform on a real brain. Thus, eliminating the need to conduct tests on live human and animal subjects.

However, studying brain organoids is tricky. To explain this further, David Gracias, professor of chemical and biomolecular engineering at John Hopkins University, tells IE, “ brain organoids are very tiny (like a dot of a pen), and it is challenging to measure electrical activity from them using conventional instrumentation (microelectrode arrays).” Therefore, the researchers created miniaturized microelectrode array shells (MEA, also called micro EEG caps or mini-brain caps) with a customizable fit for mini-brains.

The significance of miniaturized EEG caps

According to the researchers, the conventional methods to study brain organoids can examine only a limited number of cells found on the surface of the mini-brains. They cannot be employed to understand how the neuronal cells communicate with one another and how they react when subjected to a new chemical. The miniaturized EEG electrode caps that perfectly fit mini-brains would overcome such limitations.

Just like how doctors use dotted skull caps to detect disorders and tumors in the human brain, the micro EEG electrode caps would enable scientists to better understand brain organoids' chemical and electrical activity. The detailed analysis of organoids could even help them understand the effect of different chemicals on brain functions. For instance, pesticide-treated vegetables and antibiotic medicines contain various chemicals that can adversely affect the nervous system of insects and animals.

Using brain organoids and micro EEG caps, scientists can study the impact of such chemicals on the human brain and track neural disorders while they originate. Such experiments could also reveal how different drugs affect the human brain. The size of an electrode cap is in micrometers, and it needs to be wrapped around the 3D surface of a mini-brain to record the neural activity.

According to the study, scientists could listen to the noise of electrical activity inside the mini-brains using these caps. When asked about the wide-scale implications of micro EEGs, Professor Gracias said, “we believe that our developed shell-MEAs can allow interrogation of brain organoids with higher Spatio-temporal resolution and higher signal to noise which could accelerate our understanding of the human brain and related disorders.”

Challenges with mini-organs and mini caps

Although organoids have been used for over a decade, there are various challenges unique to their application. For instance, regular lab instruments are meant to examine regular-sized organs. They cannot be used to study miniaturized organs. Therefore, scientists are required to create new miniature-scale lab tools to experiment with the mini organs.

The main challenge related to the miniaturization of the laboratory and medical instruments to small-size scales is to preserve their three-dimensionality. Moreover, different brain organoids require different types of instruments. The mini EEG electrode cap developed by the researchers is a compatible device for studying mini-brains. Still, the mini caps cannot be used in the case of studying, say, a mini kidney or a heart organoid.

The researchers are now planning to create novel instrumentation for mini-organs, including the ability to exchange liquids, stimulate and record electrical activity.

The complete study is published in the journal Science Advances.