Cationic carbon dots: A novel class of mimetic enzymes
image: Cationic CDs, which possess a positively charged surface, have shown the ability to mimic natural enzyme applications. The positive charge on the surfaces of these nanomaterials significantly influences their fluorescence, biological activity, and interactions with other biomolecules.
Credit: 《Cationic carbon dots: a novel class of mimetic enzymes》，Nano Research
A recent review by Hai-Tao Li's team at Jiangsu University examined the most recent research on the design, structure, catalytic mechanism, biosensing ability and biomedical applications of enzyme-like cationic carbon dots. The synthetic strategies employed in the production of cationic carbon dots are reviewed, and the impact of surface charge on their physical and chemical properties is discussed. The text goes on to highlight the various applications of these cationic carbon dots, demonstrating their use in detection, biomedical applications (including antimicrobials, gene vectors and therapeutic agents), catalysis and other areas. Finally, the challenges and obstacles encountered during the development of cationic carbon dots are discussed, and future prospects are explored.
The team published their review in Nano Research on April 8, 2025.
“In this review, we present a summary of the synthesis methods for cationic CDs, the influence of surface charge on CDs performances, as well as the applications for cationic CDs in recent years. The influence of surface charge on the performances of CDs, which include optical, chemical, biological, and physical characteristics, is comprehensively described. Applications of cationic CDs are categorized and summarized thoroughly, covering fluorescent sensors, biomedicine (imaging, antibiosis, therapy, non-viral gene vectors), catalysis (including photocatalysis and electrocatalysis), physical adsorption and separation. We also conclude with a comprehensive summary of some of challenges and barriers faced during the development of cationic CDs, as well as an outlook regarding further exploration for new applications.” said Haitao Li, senior author of the review paper and professor at the Energy Research Institute of Jiangsu University.
CDs have a number of oxy-functional groups, like carboxyl, hydroxyl, or epoxy functional groups, which offer a high degree of selectivity and the ability to chemically interact with additional chemical as well as biological entities, and also have many extraordinary properties, including abundant photoluminescence properties, easy surface functionalization, chemical stability, photostability, excellent biocompatibility, low cytotoxicity, and excellent water solubility. These special properties have been widely used in biomedical and chemical applications.
The team outlined the synthetic methods and properties of cationic CDs. “Cationic CDs have garnered significant attention due to their adjustable enzyme activity, microbial adhesion, and excellent biocompatibility across a broad spectral range. In particular, CDs with an sp² hybrid structure have demonstrated a strong ability to generate reactive oxygen species. Nitrogen doping in these CDs enhances their peroxidase activity, making them more effective as nanomaterials. Furthermore, the intrinsic activity of carbon nanomaterials can be further improved by using thiourea as a source of sulfur.” Haitao Li said.
The positive surface charge of nanomaterials greatly influences fluorescence, bioreactivity, and interactions with biomolecules. These characteristics enable cationic CDs to be utilized in sensors, biomedicine, and catalysis.
Haitao Li said, “The sensing principle is usually based on specific interactions between the surface functional group or targeting moiety and the analyte, which leads to a change in the photoemission properties of the cationic CDs, thus achieving high sensitivity and selectivity for the detection of specific molecules.”
Most natural enzymes are proteins, which can lead to certain inherent drawbacks, such as variability, susceptibility to loss of activity, cumbersome purification processes, and challenges in storage and recycling. “CDs possess good enzyme activity, effective hydroxyl radical scavenging capabilities, and superior fluorescence properties, making them suitable for biomedicine applications.” said Haitao Li.
Natural enzymes are powerful biocatalysts, but their practical applications are often hampered by their inherent drawbacks, such as low stability and high preparation and purification costs. In addressing these challenges, significant attention has been directed towards the utilisation of nanomaterials, which possess a number of advantageous properties, including their stable structure, low cost and tunable activity. Haitao Li said, “cation CDs enzyme-like materialscan be used as photosensitizers in photocatalytic processes. Bonding of CDs to semiconductors can enhance their photocatalytic activity and electrical conductivity.”
This research team offers some recommendations for future research perspectives in cationic CDs field. “Biomass-derived CDs are environmentally friendly and easy to recover, usually rich in functional groups, and can easily bind to metal ions. Developing the use of biomass CDs. to detect metal ions can solve the problems of complicated operation and expensive equipment of traditional detection methods.” said Haitao Li.
Other contributors include Xin Wu, Zhuang Tong, Yunliang Liu, Yi Yang, Yaxi Li, Yuanyuan Cheng, Jingwen Yu and Naiyun Liu from the Energy Research Institute of Jiangsu University; and Chanyuan Jin from the Second Dental Center, Peking University School and Hospital of Stomatology.
This work was supported by the National Natural Science Foundation of China (Grants 52072152, 51802126), the Jiangsu University Jinshan Professor Fund, the Jiangsu Specially-Appointed Professor Fund, Open Fund from Guangxi Key Laboratory of Electrochemical Energy Materials, Zhenjiang “Jinshan Talents” Project 2021, China PostDoctoral Science Foundation (2022M721372), “Doctor of Entrepreneurship and Innovation” in Jiangsu Province (JSSCBS20221197), and the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Nos. KYCX22_3645 and KYCX24_3964).
About Nano Research
Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.