Prof.  Qing-Hua  Xu
National University of Singapore,  Singapore

Title: Nano-photosensitizers for Two-photon Excitation based Imaging Guided Therapy

Abstract:

Phototherapy, including photothermal therapy (PTT) and photodynamic therapy (PDT), is a non-invasive treatment technique that use phototherapeutic chemicals in concert with light irradiation to generate heat or cytotoxic reactive oxygen species (ROS) to selectively kill cancer cells with minimal harmful effects to normal tissues, which has great potential for cancer therapy. Two-photon excitation techniques have unique advantages such as 3-dimensional selectivity and deep penetration into biological tissues, compared to their one-photon counterparts. In this talk, I will present our recent research work on the development of nanocomposite materials with enhanced two-photon excitation properties and their potential applications in cancer therapy. We used two different strategies to develop composite nanomaterials with enhanced two-photon properties. One is based on energy transfer from conjugated polymers that have large two-photon absorption cross sections as two-photon light harvesting materials. We have developed various schemes for two-photon sensing, imaging, and photodynamic therapy, with efficiency improved by over 1000-fold. Another approach is based on plasmon resonance enhancement. Noble metal nanoparticles are known to display unique properties of localized surface plasmon resonance, which could be utilized to enhance linear and nonlinear optical properties of external chromophores and metal nanoparticles themselves. We have developed various plasmon engineered nanocomposites with enhanced two-photon properties, explored their biological applications, and conducted single particle spectroscopy and ultrafast spectroscopy studies to understand the underlying enhancement mechanisms. We have further combined these two strategies to develop plasmon enhanced two-photon optical properties of conjugated polymer-based NPs for biomedical applications.

Biography:

Qing-Hua Xu received his Ph.D. from UC Berkeley (2001) and conducted postdoctoral Research at Stanford University (2001-2002) and UC Santa Barbara (2002-2005). He joined the Department of Chemistry, National University of Singapore in 2005 and became a tenured Associate Professor in 2011. His primary research interests focus on optical properties and dynamical processes of novel low-dimensional materials as well as their applications in biomedicine, optoelectronics, energy, and environmental areas. So far, he has published over 240 peer reviewed articles with citations of >17,000 times and H-index of 78.