Find Six Disease-Causing Substances All at Once in Just 20 Minutes

KAIST, Gachon University, POSTECH Joint Research Team Develops Paper Sensor

Image related to the development of a paper sensor for detecting disease substances capable of simultaneously detecting six target substances. Image courtesy of KAIST.

[Asia Economy Reporter Kim Bong-su] Domestic researchers have developed a paper sensor capable of accurately detecting six different disease-causing substances.

The Korea Advanced Institute of Science and Technology (KAIST) announced on the 7th that Professor Jinwoo Lee's research team from the Department of Bio and Chemical Engineering, together with Professor Moonil Kim's team from Gachon University’s Department of Bio-Nano Engineering and Professor Jungwoo Han's team from POSTECH’s Department of Chemical Engineering, succeeded in synthesizing a new inorganic material (Nanozyme) and developed a paper sensor that can precisely detect six target substances simultaneously using this material.

The research team developed cobalt-doped mesoporous structured cerium oxide, which, unlike conventional peroxidase-mimicking nanozymes, exhibits activity in neutral conditions and has large pores capable of loading oxidase enzymes. Using this, they succeeded in creating a paper sensor capable of simultaneously detecting six substances, including disease diagnostic markers such as glucose, acetylcholine, and cholesterol.

This study was published in the international journal Advanced Functional Materials, Volume 19, Issue 2, last month.

Nanozymes can be used not only for detecting various diseases where traditional enzymes have been applied but also in extreme environments or diverse microenvironments within the body where enzymes are difficult to use. Enzymes act as catalysts in various chemical reactions inside our bodies, and recently, purified enzymes have been reported to be applicable in detecting various substances and treatments. In particular, peroxidase oxidizes a transparent chromogenic substrate in the presence of hydrogen peroxide, turning it blue, allowing visual detection of hydrogen peroxide. When used together with oxidases for substances like acetylcholine and glucose that release hydrogen peroxide during oxidation, target substances can be visually detected.

However, most oxidases that oxidize acetylcholine and glucose have optimal activity at neutral pH, whereas peroxidase-mimicking nanozymes are active only in acidic conditions, requiring a change in buffer solution to adjust the pH during detection. This makes it difficult to detect subtle amounts of target substances and limits their application as biosensors. Therefore, developing nanozymes that mimic peroxidase activity in neutral conditions and can load oxidases for target substances is essential.

To solve this problem, the research team introduced Density Functional Theory (DFT) to screen which elements, when doped onto cerium oxide with existing peroxidase activity, would maintain peroxidase activity in neutral conditions. Through calculations, cobalt was predicted to be the optimal element.

The team succeeded in synthesizing mesoporous cerium oxide with large 17-nanometer (nm) pores doped with cobalt to induce activity in neutral conditions and to load oxidases. Unlike typical mesoporous nanomaterials with 2?3 nm pores, the team synthesized the material to have larger pores by controlling changes during heat treatment, confirming that oxidases could be loaded into these pores. Additionally, the synthesized nanozyme exhibited optimal activity at neutral pH (pH 6), enabling cascade reactions with oxidases without changing pH.

The researchers loaded oxidases for important disease diagnostic substances such as glucose, acetylcholine, choline, galactose, and cholesterol onto the developed nanozyme and created a paper sensor capable of simultaneously detecting six substances, including hydrogen peroxide. This paper sensor can rapidly detect six substances within 20 minutes and demonstrated better detection limits than existing sensors that detect substances individually. Furthermore, the team confirmed that oxidases loaded onto mesoporous cerium oxide remained stable at high temperatures of 60°C and functioned reliably for over 60 days.

Professor Lee stated, "Although the field of nanozymes has not been established for long, interest is rapidly increasing due to their potential to replace traditional enzymes." He added, "In the future, nanozymes could be introduced not only in paper sensors but also in various diagnostics and cancer treatments, potentially leading to significant advances in diagnosis and therapy."

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