title: Influence of pH and Surface Chemistry on Poly(L-lysine) Adsorption onto Solid Supports Investigated by Quartz Crystal Microbalance with Dissipation Monitoring.
abstract: Poly(L-lysine) (PLL) adsorption onto various materials has been widely applied as a surface modification strategy and layer-by-layer fabrication method. Considering the role of electrostatic charges, a detailed understanding of the influence of solution pH on PLL adsorption process is important for optimization of PLL coating protocols. Herein, PLL adsorption onto different polar and hydrophilic substrates—silica, an amine-terminated self-assembled monolayer (SAM) on gold, and a carboxyl-terminated SAM on gold—across a range of pH conditions was investigated using the quartz crystal microbalance with dissipation. The adsorption kinetics consisted of an initial rapid phase, followed by a second phase where adsorption rate gradually decelerated. These features were interpreted by applying a mean-field kinetic model implying diffusion-limited adsorption in the first phase and reconfiguration of adsorbed PLL molecules in the second phase. The adsorption kinetics and uptake were found to be sensitive to the pH condition, surface chemistry, and flow rate. The strongest PLL adsorption occurred at pH 11 on all three surfaces while weak PLL adsorption generally occurred under acidic conditions. The surface morphology and roughness of adsorbed PLL layers were investigated using atomic force microscopy, and strong PLL adsorption is found to produce a uniform and smooth adlayer while weak adsorption formed a nonuniform and rough adlayer.
authors.affiliation: †School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|‡Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, 637553 Singapore.
authors.forename: Jae-Hyeok
authors.initials: JH
authors.lastname: Choi
authors.affiliation: †School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|‡Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, 637553 Singapore.
authors.forename: Seong-Oh
authors.initials: SO
authors.lastname: Kim
authors.affiliation: †School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|‡Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, 637553 Singapore.
authors.forename: Eric
authors.initials: E
authors.lastname: Linardy
authors.affiliation: §Koch Institute for Integrative Cancer Research, Department of Chemical Engineering, Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02139, United States.
authors.forename: Erik C
authors.initials: EC
authors.lastname: Dreaden
authors.affiliation: †School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|‡Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, 637553 Singapore.|⊥Boreskov Institute of Catalysis, Russian Academy of Sciences, Novosibirsk 630090, Russia.
authors.forename: Vladimir P
authors.initials: VP
authors.lastname: Zhdanov
authors.affiliation: §Koch Institute for Integrative Cancer Research, Department of Chemical Engineering, Institute for Soldier Nanotechnologies, Massachusetts Institute of Technology, 500 Main Street, Cambridge, Massachusetts 02139, United States.
authors.forename: Paula T
authors.initials: PT
authors.lastname: Hammond
authors.affiliation: †School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore.|‡Centre for Biomimetic Sensor Science, Nanyang Technological University, 50 Nanyang Drive, 637553 Singapore.|∥School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, 637459 Singapore.
authors.forename: Nam-Joon
authors.initials: NJ
authors.lastname: Cho
mesh_terms: D000327:Adsorption; D000588:Amines / Q000737:chemistry; D002021:Buffers; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D011107:Polylysine / Q000737:chemistry*; D058525:Quartz Crystal Microbalance Techniques; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties
chemical_list: D000588:Amines; D002021:Buffers; D011107:Polylysine; D012822:Silicon Dioxide