title: Self-assembled thermosensitive micelles based on poly(L-lactide-star block-N-isopropylacrylamide) for drug delivery.
abstract: A novel seven-arm star block copolymer poly(L-lactide-star block-N-isopropylacrylamide) (PLLA-sb-PNIPAAm), comprised of a hydrophobic poly(L-lactide) (PLLA) arm and an average of six hydrophilic poly(N-isopropylacrylamide) (PNIPAAm) arms, was designed and synthesized. The amphiphilic PLLA-sb-PNIPAAm copolymer was capable of self-assembling into nano-sized micelle in water, which was confirmed by FT-IR, 1H NMR and fluorescence spectroscopy. Transmission electron microscopy images showed that these nano-sized micelles were regularly spherical in shape. Micelle size determined by size analysis was around 100 nm in diameter. The micelles showed reversible dispersion/aggregation in response to temperature changes through an outer polymer shell of PNIPAAm at around 31 degrees C, observed by optical absorbance measurements. The anticancer drug methotrexate (MTX) as model drug was loaded in the polymeric nano-sized micelles. In vitro release behavior of MTX was investigated, which showed a drastic thermoresponsive fast/slow switching behavior according to the temperature-responsive structural changes of a micellar shell structure. The reversible and sensitive thermoresponse of this micelle might provide opportunities to construct a novel drug delivery system in conjunction with localized hyperthermia.
authors.affiliation: Department of Chemistry, Key Laboratory of Biomedical Polymers of Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wei
authors.affiliation: Department of Chemistry, Key Laboratory of Biomedical Polymers of Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Xian-Zheng
authors.initials: XZ
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, Key Laboratory of Biomedical Polymers of Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Wen-Qin
authors.initials: WQ
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Key Laboratory of Biomedical Polymers of Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Si-Xue
authors.initials: SX
authors.lastname: Cheng
authors.affiliation: Department of Chemistry, Key Laboratory of Biomedical Polymers of Ministry of Education, Wuhan University, Wuhan 430072, People's Republic of China.
authors.forename: Ren-Xi
authors.initials: RX
authors.lastname: Zhuo
mesh_terms: D000178:Acrylamides / Q000737:chemistry*; D004337:Drug Carriers; D006358:Hot Temperature; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D011091:Polyesters / Q000737:chemistry*; D011239:Prednisolone / Q000008:administration & dosage / Q000031:analogs & derivatives*; D013050:Spectrometry, Fluorescence / Q000379:methods; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D000178:Acrylamides; D004337:Drug Carriers; D008823:Micelles; D011091:Polyesters; C033616:poly(lactide); C009935:prednisolone acetate; D011239:Prednisolone; C067295:N-isopropylacrylamide