title: Upconversion nanoparticles in biological labeling, imaging, and therapy.
abstract: Upconversion refers to non-linear optical processes that convert two or more low-energy pump photons to a higher-energy output photon. After being recognized in the mid-1960s, upconversion has attracted significant research interest for its applications in optical devices such as infrared quantum counter detectors and compact solid-state lasers. Over the past decade, upconversion has become more prominent in biological sciences as the preparation of high-quality lanthanide-doped nanoparticles has become increasingly routine. Owing to their small physical dimensions and biocompatibility, upconversion nanoparticles can be easily coupled to proteins or other biological macromolecular systems and used in a variety of assay formats ranging from bio-detection to cancer therapy. In addition, intense visible emission from these nanoparticles under near-infrared excitation, which is less harmful to biological samples and has greater sample penetration depths than conventional ultraviolet excitation, enhances their prospects as luminescent stains in bio-imaging. In this article, we review recent developments in optical biolabeling and bio-imaging involving upconversion nanoparticles, simultaneously bringing to the forefront the desirable characteristics, strengths and weaknesses of these luminescent nanomaterials.
authors.affiliation: Department of Chemistry, Faculty of Science, National University of Singapore, 3 Science Drive 3, Singapore 117543.
authors.forename: Feng
authors.initials: F
authors.lastname: Wang
authors.forename: Debapriya
authors.initials: D
authors.lastname: Banerjee
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Liu
authors.forename: Xueyuan
authors.initials: X
authors.lastname: Chen
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Liu
mesh_terms: D005456:Fluorescent Dyes / Q000032:analysis / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D057054:Molecular Imaging / Q000379:methods*; D053758:Nanoparticles / Q000032:analysis* / Q000737:chemistry / Q000627:therapeutic use*; D009369:Neoplasms / Q000188:drug therapy*; D011506:Proteins / Q000737:chemistry; D013194:Staining and Labeling / Q000379:methods
chemical_list: D005456:Fluorescent Dyes; D046911:Macromolecular Substances; D011506:Proteins