NUS dons win German research prizes for nanoscale control of light

Imagine a place full of moving lights of a hundred different colours changing rapidly under precision control, and one of the first things that comes to mind is a discotheque.

A not-too-different scene is happening in the labs of two principal investigators at NUS - but at the nanoscale.

Professor Zhang Yong from NUS Biomedical Engineering and Professor Jiang Donglin from NUS Chemistry, however, are not doing this for entertainment. Their experiments with light could actually save lives and even help save the planet. And their efforts have earned each of them the Humboldt Research Award from Germany.

Next year, they will travel to different parts of Germany on €60,000 grants to collaborate with researchers and take their respective fields of study to the next level.

Funded by the Alexander von Humboldt Foundation in Germany, the Humboldt Research Award honours international scientists who are outstanding researchers in their field and whose work have had a significant impact on their own discipline and beyond.

Zapping cancer with light

Prof Zhang’s specialty is in developing devices containing special nanoparticles that can be implanted in diseased locations deep in the human body, such as cancer. The nanoparticles emit light of specific colours when stimulated by X-rays or near-infrared light from a “remote control” outside the body. The light from the nanoparticles activates special light-sensitive drugs to accurately target and kill cancerous cells, in a treatment known as photodynamic therapy (PDT). This is more targeted and less debilitating than chemotherapy, which causes widespread damage to good tissue.

Prof Zhang’s team has described their latest nanoparticles as looking like watermelons under the transmission electron microscope. Materials with different functions are assembled at the nanoscale and combined in small nanocrystals. When excited by deep tissue-penetrating X-rays or near-infrared light, these nanoparticles emit light that could be used to activate anti-cancer drugs in precise locations in the body. This new nanoparticle is used as a nanotransducer to manipulate light at the nanoscale, and was published in Nature Communications in January 2021.

“As a child, I always wanted to be a scientist, but when I grew up I found that scientific research was not as simple as described in comic books,” said Prof Zhang. But as it turned out, there was a higher calling. After publishing his research papers as a young principal investigator at NUS, he started getting emails from cancer patients and their families from several countries, asking if the new materials he had developed could give them a chance at treating their illness. Prof Zhang shared, “They were in despair and were writing to scientists all over the world hoping to find a cure. I felt bad when I had to disappoint them.”

That spurred him to find ways of translating his research to medical treatments that could actually save lives. He began working with the National Cancer Centre Singapore, Duke-NUS Medical School and National University Health System, which helped identify clinical needs and how his devices could be harnessed to satisfy those needs. His efforts also coincide with one of NUS’ key research areas, Biomedical Science and Translational Medicine. “It takes time to develop a new technology and make it available for clinical use, but we are on the way,” he said.

Designing and manipulating two-dimensional polymeric materials

On the other side of campus, Prof Jiang is working on organic two-dimensional polymers, a kind of molecule that is very large but only a few molecules thick. He is a world expert in the field - in fact, he pioneered it.

When he got his first academic job working on 2D polymers in Japan many years ago, he wanted to do something no one had done before. Scientists had created self-assembling 2D polymers previously, but they had used noncovalent bonds, which are chemical bonds that do not involve the sharing of electrons between atoms.

Prof Jiang had the idea of creating 2D polymers using covalent bonds instead. These bonds can be found in organic compounds, which are substances that contain carbon-hydrogen bonds. The so-called covalent organic frameworks (COFs) created by Prof Jiang can form stable structures that are more complex than purely noncovalent polymers, giving scientists more flexibility in designing polymers with desired properties.

At NUS, Prof Jiang has been investigating the many potential “talents” of COFs, from energy storage to semiconductors to reducing emissions by absorbing and converting carbon dioxide. However, the chemical and physical properties of COFs cannot be easily controlled, making them unwieldy in practice.

In their latest research, Prof Jiang’s team found a way to easily and accurately modify the 2D molecular backbone of COFs with various atoms and molecules, such as hydrogen, chlorine and methyl groups, to induce emission of different wavelengths of light spanning the entire colour spectrum. Furthermore, their system is chemically stable and emits lots of light, taking it a big step towards actual light-emitting and sensing applications in the real world. Their findings were published in Angewandte Chemie International Edition in June 2021, and has been categorised by the journal as a “Very Important Paper”. The research on COFs also contributes to NUS’ key focus areas of Materials Science, Smart Nation and Integrative Sustainability Solutions.

Pushing the frontiers of science through international collaboration

Prof Zhang and a couple of his PhD students will visit Technische Universität Ilmenau in Germany to collaborate with a few researchers there, whom he met many years ago in a scientific meeting but has not had a chance to work with.

With expertise in nanofabrication, the combined team will develop new implantable PDT devices that combine the light-emitting nanoparticles and light-sensitive drugs in a single biodegradable package with better light transmission. This will make PDT less invasive and more effective. Prof Zhang’s devices are currently non-biodegradable and have to be left in the body permanently or removed surgically.

Meanwhile, Prof Jiang plans to deepen his existing collaborations with four principal investigators at the Max Planck Institute for Polymer Research, Max Planck Institute for Solid State Research and Technische Universität Dresden. Each of them will work on a different aspect of 2D polymers and COFs. Three of Prof Jiang’s PhD students will also be involved.

Collectively, the scientists will develop a whole range of new structures and functions for COFs with the potential to scale up and tackle global environmental and energy issues. “The collaboration will merge the strengths of our group and the German groups. COFs offer very promising materials for a sustainable development of our society,” said Prof Jiang.

Bon voyage!