报告人：Prof. Yong Zhang
Department of Bioengineering, Faculty of Engineering
National University of Singapore, Singapore 117574
题目: Upconverting Fluorescent Nanoparticles for light based detection, disease diagnostics and therapy
Upconverting nanoparticles (UCNs) present a new technology for optical imaging/detection which is a growing field with both diagnostic and drug discovery uses. Currently, fluorophores including fluorescent dyes/proteins and quantum dots (QDs) are used for fluorescence-based imaging and detection. These are based on ‘downconversion fluorescence’, emitting low energy fluorescence when excited by high energy light (such as UV or short wavelength visible light). Fluorophores in current use have several drawbacks: photobleaching, autofluorescence, short tissue penetration depth and tissue photo-damage. UCNs emit detectable photons of higher energy in the visible range upon irradiation with near-infrared (NIR) light based on a process termed ‘upconversion’. UCNs show absolute photostability, negligible autofluorescence, high penetration depth and minimum photodamage to biological tissues. They can be used for ultrasensitive interference-free biodetection because most biomolecules do not have upconversion properties.
UCNs are also useful for light based therapy with enhanced efficiency. Photodynamic therapy (PDT) has several advantages as compared to chemotherapies: cost-effectiveness, highly localized and specific tumor treatments, outpatient therapy, higher cure rates for some tumors, and repetition of therapy without cumulative toxicity. PDT involves two individually non-toxic components that are combined to kill cancer cells. The first component is photosensitizer, a photosensitive molecule that localizes to a target cell and/or tissue. The second component involves the administration of light of a specific wavelength that activates the sensitizer. The photosensitizer transfers energy from light to molecular oxygen, to generate reactive oxygen species which can kill cancer cells. Most of photosensitizers are activated by visible light only. However, visible light has limited penetration depth in biological tissues. For this reason, PDT is usually used to treat tumors on or just under the skin or on the lining of internal organs or cavities, and is less effective in treating large tumors or deep-seated tumors. UCNs are used for enhanced PDT in deep tissues, because NIR light can go much deeper in tissues than visible light. They are used not only as a light converter but also a carrier for photosensitizers.
Dr. Yong Zhang is an Associate professor and Deputy Head in Department of Bioengineering, National University of Singapore (NUS), a senior Faculty member of NUS Nanoscience & Nanotechnology Initiative (NUSNNI / NanoCore), and the Principle Investigator of Cellular & Molecular Bioengineering Laboratory. He is also an Executive Committee (EXCO) member, Admission Committee Chair and senior Faculty member of NUS Graduate School for Integrative Sciences and Engineering (NGS). Prior to that, he was a research scientist at National Institute of Biomedical Engineering (INEB, Portugal), and a researcher at University of Washington (UW) and PNNL/UW Joint Institute for Nanoscience (USA). His current research interests include nanobiophotonics, nanomedicine, biomedical microdevices, and tissue engineering. He has authored over 200 peer-reviewed research papers in high impact factor journals such as Nature Medicine and PNAS, a number of book chapters and patents. He received NUS Young Investigator Award, DAAD Scholarship and a few other research awards. He is in the editorial board of more than 15 peer reviewed international scientific journals. Currently he is a guest professor of University of Science & Technology of China and HuangShan Scholar of Hefei University of Technology.