Synthesis and Characterization of a Micelle-Based pH Nanosensor with an Unprecedented Broad Measurement Range

Pramod Kumar Ek, Lise N. Feldborg, Kristoffer Almdal, Thomas L. Andresen

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

A new cross-linked micelle pH nanosensor design was investigated. The nanosensor synthesis was based on self-assembly of an amphiphilic triblock copolymer, poly(ethylene glycol)-b-poly(2-amino ethyl methacrylate)-b-poly(coumarin methacrylate) (PEG-b-PAEMA-b-PCMA), which was synthesized by isolated macroinitiator atom transfer radical polymerization. Micelles were formed by PEG-b-PAEMA-b-PCMA self-assembly in water, giving micelles with an average diameter of 45 nm. The PCMA core was employed to utilize coumarin-based photoinduced cross-linking in the core of the micelles, which was performed by UV irradiation (320 nm <λ <500 nm), and the progress of the cross-linking was monitored by UV spectroscopy. The formed cross-linked core–shell–corona micelle was converted into ratiometric pH nanosensors by binding the pH-sensitive fluorophores oregon green 488 and 2′,7′-bis-(2-carboxyethyl)-5-(and-6) carboxyfluorescein and a reference fluorophore Alexa 633 to the PAEMA shell region of the micelles. Fluorescence measurements show that these pH nanosensors are sensitive in a surprisingly broad pH range of 3.4–8.0, which is hypothesized to be due to small differences in the individual fluorophores’ local environement. It was found that the utilization of self-organization principles to form the nanoparticles, followed by cross-linking to ensure sensor integrity, provides a fast and highly flexible method that can be utilized in a broad range of nanosensor designs.
Original languageEnglish
JournalChemistry of Materials
Volume25
Issue number9
Pages (from-to)1496-1501
ISSN0897-4756
DOIs
Publication statusPublished - 2013

Keywords

  • Nanosensor
  • Cross-linked micelle
  • Coumarin
  • Core−shell−corona micelle
  • Ratiometric sensor
  • pH sensor

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