1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Colloids and Biological Interfaces, Department of Micro- and Nanotechnology, Technical University of Denmark3 Center for Nanomedicine and Theranostics, Center, Technical University of Denmark4 Amphiphilic Polymers in Biological Sensing, Department of Micro- and Nanotechnology, Technical University of Denmark5 Risø National Laboratory for Sustainable Energy, Technical University of Denmark6 Center for Nanostructured Graphene, Center, Technical University of Denmark
A micelle based nanosensor was synthesized and investigated as a ratiometric pH sensor for use in measurements in living cells by fluorescent microscopy. The nanosensor synthesis was based on self-assembly of an amphiphilic triblock copolymer, which was chemically cross-linked after micelle formation. The copolymer, poly(ethylene glycol)-b-poly(2-aminoethyl methacrylate)-b-poly(styrene) (PEG-b-PAEMA-b-PS), was synthesized by isolated macroinitiator atom transfer radical polymerization that forms micelles spontaneously in water. The PAEMA shell of the micelle was hereafter cross-linked by an amidation reaction using 3,6,9-trioxaundecandioic acid cross-linker. The cross-linked micelle was functionalized with two pH sensitive fluorophores and one reference fluorophore, which resulted in a highly uniform ratiometric pH nanosensor with a diameter of 29 nm. The use of two sensor fluorophores provided a sensor with a very broad measurement range that seems to be influenced by the chemical design of the sensor. Cell experiments show that the sensor is capable of monitoring the pH distributions in HeLa cells.
Journal of Materials Chemistry B, 2014, Vol 2, Issue 38, p. 6652-6659