1. Fluorescence based biodetection & bioimaging
Both down-conversion and up-conversion fluorescent inorganic nanoparticles (quantum dots, lanthanide doped nanocrystals) are synthesized and used as fluorescent labels or imaging probes for biodetection & bioimaging. The up-conversion fluorescent nanoparticles can convert near infrared (NIR) light to visible light. Compared to conventional down-conversion fluorescent materials such as organic dyes and quantum dots, these nanoparticles have the following advantages: High light penetration depth in tissues; No photodamage to living organisms; Weak autofluorescence from cells or tissues; Low background light and high sensitivity for detection. Li ZQ & Zhang Y, Angewandte Chemie International Edition 2006, 45, 7732-7735.
2. Imaging-guided cancer therapy
Multi-color fluorescent quantum dots and magnetic agents are encapsulated within nanometer-sized (~50 nm) chitosan nanoparticles. The small size of the nanoparticles allows them to be used as a labeling tag, at the same time, as a contrast agent in magnetic resonance imaging (MRI) as well. In the labeling of cancer cells, specific targeting molecules that recognize cancer cells can be attached to the surface of the nanoparticles so that they bind onto the surface of the cancer cells specifically. This can potentially help in the localization and identification of a cancerous tissue. Moreover, these nanoparticles can be used to deliver therapeutic drugs, proteins and genes by intravenous, oral and mucosal administration. Using these nanoparticles, drugs or genes can be precisely delivered to the specific cells or specific regions of tissues with aid of imaging techniques, for various applications. Tan WB & Zhang Y, Advanced Materials 2005, 17, 2375-2380. Tan WB, Jiang S & Zhang Y. Biomaterials, in press
3. Bead based microarrays for multiplexing bioassays
Compared to the microarrays fabricated on planar substrates, bead based microarrays are more robust as microbeads are ideal reagent delivery vehicles providing large reactive surface areas and have become omnipresent in biomedical applications. A technique is developed to fabricate a microfluidic device with unique dome-shape structures for high efficiency immobilization and patterning of single microbeads. We have also fabricated polymer porous films with tunable pore sizes by employing non-lithographic “breadth figure” method and colloidal template method, for patterning of microbeads. Our research aims to use arrays of encoded microbeads for high-throughput multiplexing bioassays. Lu MH & Zhang Y, Advanced Materials 2006, 18, 3094-3098.
4. Micropatterning of proteins & cells via self-assembled nanoparticles
Micropatterning of biomolecules forms the basis of cell culture, biosensor and microarray technology. We have reported methods to pattern biomolecules through self-assembling polystyrene nanoparticles in arrayed microwells on a solid surface to form well-ordered patterning, followed by attaching biomolecules and cells to the assembled nanoparticles.
Wang C & Zhang Y, Advanced Materials 2005, 17, 150-153. Yap FL & Zhang Y, Langmuir 2005, 21, 5233-5236.