title: The effects of anionic electrolytes and human serum albumin on the LCST of poly(N-isopropylacrylamide)-based temperature-responsive copolymers.
abstract: Poly(N-isopropylacrylamide) (PNIPAm) is one of the most widely studied temperature-responsive polymers among those that have been applied to biomaterials science and technology. Here, we investigated the importance of interactions between PNIPAm-based copolymers and biological factors. The effects of a series of major anionic electrolytes in biological environments and of human serum albumin (HSA) on the lower critical solution temperature (LCST) of homo-PNIPAm and PNIPAm copolymers were studied, using either a hydrophobic monomer or a cationic monomer. We synthesized P(NIPAm-co-BMA3%) with butyl methacrylate (BMA) as a hydrophobic monomer and P(NIPAm-co-DMAPAm2%) with N,N-dimethylaminopropyl acrylamide (DMAPAm) as a cationic monomer. The LCST of PNIPAm and P(NIPAm-co-DMAPAm2%) decreased with increasing salt concentrations, and the effects of anions on each polymer corresponded to the Hofmeister series. The LCST of P(NIPAm-co-DMAPAm2%) was greatly affected by anionic electrolytes compared with those of homo-PNIPAm and P(NIPAm-co-BMA3%). While the LCST of homo-PNIPAm was not affected by HSA, the LCST of P(NIPAm-co-DMAPAm2%) decreased non-linearly with increasing HSA concentrations. These effects were due to the electrostatic interactions between the positively charged polymer chains and the negatively charged HSA, as well as the stabilization of polymer aggregations with HSA. Under physiological buffer conditions, the LCST of P(NIPAm-co-DMAPAm2%) was not significantly affected by the HSA concentration. These results indicated that depending on the types of copolymers used for biological applications, it is necessary to take into account the effect of biological media while designing polymers.
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hiruta
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Yuhei
authors.initials: Y
authors.lastname: Nagumo
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Takaaki
authors.initials: T
authors.lastname: Funatsu
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ishikawa
authors.affiliation: Faculty of Pharmacy, Keio University, 1-5-30 Shibakoen, Minato, Tokyo 105-8512, Japan. Electronic address: kanazawa-hd@pha.keio.ac.jp.
authors.forename: Hideko
authors.initials: H
authors.lastname: Kanazawa
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000838:Anions; D004573:Electrolytes / Q000737:chemistry*; D006801:Humans; D011108:Polymers / Q000737:chemistry*; D012709:Serum Albumin / Q000737:chemistry*; D013696:Temperature
chemical_list: D000180:Acrylic Resins; D000838:Anions; D004573:Electrolytes; D011108:Polymers; D012709:Serum Albumin; C052970:poly-N-isopropylacrylamide
keywords: Hofmeister series; Human serum albumin; LCST; Poly(N-isopropylacrylamide); Temperature-responsive