title: Simple synthesis of carboxyl-functionalized upconversion nanoparticles for biosensing and bioimaging applications.
abstract: We report a simple one-step hydrothermal method for the synthesis of hydrophilic luminescent upconversion nanoparticles (UCNPs) using malonic acid as the stabilizer and functional agent. Using this method, two UCNPs with different colors of upconversion luminescence were synthesized. The surface of the as-prepared UCNPs was capped with carboxyl groups, which not only resulted in the UCNPs having good dispersity in water, but also allowed further conjugation with other functional molecules, thus indicating the potential applications in biosensing and bioimaging. To demonstrate this, amino-labeled single-stranded DNA (ssDNA) was conjugated on the surface of the UCNPs. Based on the different absorption and luminescence quenching abilities of graphene oxide (GO) to ssDNA-modified UCNPs before and after exonuclease I (Exo I)-triggered hydrolysis of ssDNA, a detection platform was developed for the detection of Exo I activity with a detection limit of 0.02U mL(-1). The prepared hydrophilic UCNPs were also used successfully for in vivo upconversion luminescence imaging of nude mice.
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, PR China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, PR China.
authors.forename: Gui-Mei
authors.initials: GM
authors.lastname: Han
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, PR China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, PR China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, PR China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, PR China.
authors.forename: Xiao-Xi
authors.initials: XX
authors.lastname: Huang
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, PR China; Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin 300071, PR China. Electronic address: kongdem@nankai.edu.cn.
authors.forename: De-Ming
authors.initials: DM
authors.lastname: Kong
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods*; D060326:Chemistry Techniques, Synthetic; D004277:DNA, Single-Stranded / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D006108:Graphite / Q000737:chemistry; D006868:Hydrolysis; D057927:Hydrophobic and Hydrophilic Interactions; D049408:Luminescent Agents / Q000737:chemistry*; D051379:Mice; D057054:Molecular Imaging; D053758:Nanoparticles / Q000737:chemistry*; D061848:Optical Imaging / Q000379:methods*; D010087:Oxides / Q000737:chemistry
chemical_list: D004277:DNA, Single-Stranded; D049408:Luminescent Agents; D010087:Oxides; D006108:Graphite; D005090:Exodeoxyribonucleases; C028450:exodeoxyribonuclease I
keywords: Bioimaging; Biosensing; Carboxyl-functionalized; Exonulcease I; Hydrophilic; Upconversion nanoparticles