Importance of having low-density functional groups for generating high-performance semiconducting polymer dots

ACS Nano. 2012 Jun 26;6(6):5429-39. doi: 10.1021/nn301308w. Epub 2012 May 24.

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Crystallization / methods
  • Materials Testing
  • Nanoparticles / chemistry*
  • Nanoparticles / ultrastructure*
  • Particle Size
  • Polymers / chemistry*
  • Quantum Dots*
  • Semiconductors*

Substances

  • Polymers