Temperature/pH Dual-sensitive Fluorescence Nano-gel Based on Cellulose Through Self-assembly Assisted Polymerization

Temperature/pH dual-sensitive fluorescence nanogels(FNGs) were synthesized through a self-assembly assisted(SAA) "one-step" method. A hydrophilic fluorescence monomer 5-acrylamide fluorescein(5-AAF) has been fabricated, on this basis, graft copolymerization of 5-AAF from the backbone of hydroxypropyl cellulose(HPC) was initiated using ceric ammonium nitrate(CAN), the self-assembly of 5-AAF graft chains induced by both hydrogen bond and the hydrophobic interaction of fluorescence group proceeded with the polymerization of 5-AAF. Furthermore, N,N'-methylenebisacrylamide(MBA) was applied as crosslinker. As a result, FNGs were synthesized efficiently and environment-friendly with stable temperature/pH sensitivity properties. The environment-sensitivity of resultant FNGs can be tuned by changing molecular weight of HPC, the existence of hydrophobic/hydrophilic group on FNGs as well as the hydrogen bond contributed to FNGs' temperature-sensitivity. Moreover, FNGs displayed impressive pH-sensitivity under various pH values, the fluorescence intensity can be rapidly enhanced at neutral and alkali environment, while it quenches at acidic environment. The influence of pH on fluorescence intensity can be reversed without any other recovery process. The cytotoxicity of FNG was preliminarily studied, the results revealed good biocompatibility of FNGs. The temperature/pH responsivity of the FNGs' fluorescence are of great potential in biomedical detection, such as fluorescence labeling, or temperature/pH sensor for micro-environment.