title: Importance of having low-density functional groups for generating high-performance semiconducting polymer dots.
abstract: Semiconducting polymers with low-density side-chain carboxylic acid groups were synthesized to form stable, functionalized, and highly fluorescent polymer dots (Pdots). The influence of the molar fraction of hydrophilic side-chains on Pdot properties and performance was systematically investigated. Our results show that the density of side-chain carboxylic acid groups significantly affects Pdot stability, internal structure, fluorescence brightness, and nonspecific binding in cellular labeling. Fluorescence spectroscopy, single-particle imaging, and a dye-doping method were employed to investigate the fluorescence brightness and the internal structure of the Pdots. The results of these experiments indicate that semiconducting polymers with low density of side-chain functional groups can form stable, compact, and highly bright Pdots as compared to those with high density of hydrophilic side-chains. The functionalized polymer dots were conjugated to streptavidin (SA) by carbodiimide-catalyzed coupling and the Pdot-SA probes effectively and specifically labeled the cancer cell-surface marker Her2 in human breast cancer cells. The carboxylate-functionalized polymer could also be covalently modified with small functional molecules to generate Pdot probes for click chemistry-based bio-orthogonal labeling. This study presents a promising approach for further developing functional Pdot probes for biological applications.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
authors.forename: Xuanjun
authors.initials: X
authors.lastname: Zhang
authors.forename: Jiangbo
authors.initials: J
authors.lastname: Yu
authors.forename: Changfeng
authors.initials: C
authors.lastname: Wu
authors.forename: Yuhui
authors.initials: Y
authors.lastname: Jin
authors.forename: Yu
authors.initials: Y
authors.lastname: Rong
authors.forename: Fangmao
authors.initials: F
authors.lastname: Ye
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chiu
mesh_terms: D003460:Crystallization / Q000379:methods; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D045663:Quantum Dots; D012666:Semiconductors
chemical_list: D011108:Polymers