title: Synthesis of thermo- and pH-sensitive polyion complex micelles for fluorescent imaging.
abstract: Two thermo- and pH-sensitive polypeptide-based copolymers, poly(N-isopropylacrylamide-co-N-hydroxymethylacrylamide)-b-poly(L-lysine) (P(NIPAAm-co-HMAAm)-b-PLL, P1) and poly(N-isopropylacrylamide-co-N-hydroxymethylacrylamide)-b-poly(glutamic acid) (P(NIPAAm-co-HMAAm)-b-PGA, P2), have been designed and synthesized by the ring-opening anionic polymerization of N-carboxyanhydrides (NCA) with amino-terminated P(NIPAAm-co-HMAAm). It was found that the block copolymers exhibit good biocompatibility and low toxicity. As a result of electrostatic interactions between the positively charged PLL and negatively charged PGA, P1 and P2 formed polyion complex (PIC) micelles consisting of polyelectrolyte complex cores and P(NIPAAm-co-HMAAm) shells in aqueous solution. The thermo- and pH-sensitivity of the PIC micelles were studied by UV/Vis spectrophotometry, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Moreover, fluorescent PIC micelles were achieved by introducing two fluorescent molecules with different colors. Photographs and confocal laser scanning microscopy (CLSM) showed that the fluorescence-labeled PIC micelles exhibit thermo- and pH-dependent fluorescence, which may find wide applications in bioimaging in complicated microenvironments.
authors.affiliation: Key Laboratory of Biomedical Polymers of the Ministry of Education & Department of Chemistry, Wuhan University, Wuhan 430072, PR China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Liu
authors.forename: Cao
authors.initials: C
authors.lastname: Li
authors.forename: Hui-Yuan
authors.initials: HY
authors.lastname: Wang
authors.forename: Xian-Zheng
authors.initials: XZ
authors.lastname: Zhang
authors.forename: Ren-Xi
authors.initials: RX
authors.lastname: Zhuo
mesh_terms: D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D015394:Molecular Structure; D010455:Peptides / Q000737:chemistry*; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D011107:Polylysine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D058105:Polymerization; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014867:Water / Q000737:chemistry*
chemical_list: D008823:Micelles; D010455:Peptides; C571909:poly(N-isopropylacrylamide-co-N-hydroxymethylacrylamide)-b-poly(L-lysine); C571910:poly(N-isopropylacrylamide-co-N-hydroxymethylacrylamide)-b-poly(glutamic acid); D014867:Water; D011107:Polylysine; D011099:Polyglutamic Acid