title: Versatile synthesis strategy for carboxylic acid-functionalized upconverting nanophosphors as biological labels.
abstract: Up-converting rare-earth nanophosphors (UCNPs) have great potential to revolutionize biological luminescent labels, but their use has been limited by difficulties in obtaining UCNPs that are biocompatible. To address this problem, we have developed a simple and versatile strategy for converting hydrophobic UCNPs into water-soluble and carboxylic acid-functionalized analogues by directly oxidizing oleic acid ligands with the Lemieux-von Rudloff reagent. This oxidation process has no obvious adverse effects on the morphologies, phases, compositions and luminescent capabilities of UCNPs. Furthermore, as revealed by Fourier transform infrared (FTIR) and NMR results, oleic acid ligands on the surface of UCNPs can be oxidized into azelaic acids (HOOC(CH2)7COOH), which results in the generation of free carboxylic acid groups on the surface. The presence of free carboxylic acid groups not only confers high solubility in water, but also allows further conjugation with biomolecules such as streptavidin. A highly sensitive DNA sensor based on such streptavidin-coupled UCNPs have been prepared, and the demonstrated results suggest that these biocompatible UCNPs have great superiority as luminescent labeling materials for biological applications.
authors.affiliation: Department of Chemistry & Laboratory of Advanced Materials, Fudan University, 220 Handan Road, Shanghai 200433, People's Republic of China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Chen
authors.forename: Huili
authors.initials: H
authors.lastname: Chen
authors.forename: He
authors.initials: H
authors.lastname: Hu
authors.forename: Mengxiao
authors.initials: M
authors.lastname: Yu
authors.forename: Fuyou
authors.initials: F
authors.lastname: Li
authors.forename: Qiang
authors.initials: Q
authors.lastname: Zhang
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Zhou
authors.forename: Tao
authors.initials: T
authors.lastname: Yi
authors.forename: Chunhui
authors.initials: C
authors.lastname: Huang
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D004247:DNA / Q000032:analysis; D003998:Dicarboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D049408:Luminescent Agents / Q000737:chemistry*; D008163:Luminescent Measurements; D049329:Nanostructures / Q000737:chemistry*; D019301:Oleic Acid / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D012680:Sensitivity and Specificity; D013194:Staining and Labeling; D019809:Streptavidin / Q000737:chemistry; D013499:Surface Properties
chemical_list: D003998:Dicarboxylic Acids; D049408:Luminescent Agents; D019301:Oleic Acid; D004247:DNA; D019809:Streptavidin; C010038:azelaic acid