Multi-color fluorescence of pNIPAM-Based nanogels modulated by dual stimuli-responsive FRET processes

• DOI: 10.1016/j.dyepig.2017.06.006
• Publication Date: 2017-06-04T00:30:51Z
• Authors: Seung Hwan Lee; Hoa Thi Bui; Temmy Pegarro Vales; Sung Cho; Ho-Joong Kim
• Keywords: Spiropyran; Nanogel; Merocyanine

Abstract We report the modulation of the dual photo/thermo-responsive multicolor fluorescence from poly( N -isopropyl acrylate) pNIPAM-based nanogels. The thermo-responsive pNIPAM-crosslinked matrix was covalently copolymerized with nitrobenzoxadiazole (NBD) monomers as a Forster resonance energy transfer (FRET) donor and electrostatically conjugated with photochromic spiropyran (SP) dyes as a FRET acceptor. The pristine nanogel emits green fluorescence derived from the NBD moieties; however, the irradiation of the nanogels with UV light led to the transformation of the ring-closed colorless SP moieties to the ring-opened coral-red merocyanine (MC) moieties, resulting in light-pink fluorescent nanogels. Notably, at higher temperatures, the fluorescence of the nanogels was red-shifted and enhanced by the more efficient FRET process. The nanogels were well-distributed in the cellular cytoplasm and showed excellent photochromic function in the subcellular environment for applications as photo-switchable bio-imaging agents and nanothermometers.