title: Contact time- and pH-dependent adhesion and cohesion of low molecular weight chitosan coated surfaces.
abstract: Low molecular weight chitosan (LMW chitosan, ∼5 kDa) potentially has many desirable biomedical applications such as anti-microbial, anti-tumor, and anti-diabetes. Unlike high molecular weight chitosan, LMW chitosan is easily dissolvable in aqueous solutions even at neutral and basic pH, but its dissolution mechanism is not well understood. Here, we measured adhesion and cohesion of molecularly thin LMW chitosan films in aqueous solutions in different buffer pHs (from 3.0 to 8.5) using a surface forces apparatus (SFA). Interestingly, significantly lower adhesion force was measured for LMW chitosan films compared to the high molecular weight chitosan (∼150 kDa) films. Not only the strength of adhesion is lower, but also the critical contact time where adhesion starts to increase with contact time is longer. The results from both the SFA and atomic force microscopy (AFM) indicate that, in physiological and basic conditions, the low cohesion of LMW chitosan due to the stiffness of the chain which cause strong electrostatic correlation energy penalty when they are aggregated. Here, we propose the reduction in cohesion for shorter chitosan (LMW chitosan) as an explanation of its high solubility of LMW chitosan in physiological pHs.
authors.affiliation: School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea.
authors.forename: Chanoong
authors.initials: C
authors.lastname: Lim
authors.affiliation: Department of Chemical Engineering, University of California at Santa Barbara, CA 93106, USA.
authors.forename: Dong Woog
authors.initials: DW
authors.lastname: Lee
authors.affiliation: School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea.
authors.forename: Jacob N
authors.initials: JN
authors.lastname: Israelachvili
authors.affiliation: Asia Pacific Center for Theoretical Physics, Pohang, Gyeongbuk 790-784, South Korea; Department of Physics, Pohang University of Science and Technology, Pohang, Gyeongbuk 790-784, South Korea.
authors.forename: YongSeok
authors.initials: Y
authors.lastname: Jho
authors.affiliation: School of Interdisciplinary Bioscience and Bioengineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea; School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea; Integrative Biosciences and Biotechnology, Pohang University of Science and Technology (POSTECH), Pohang 790-784, South Korea. Electronic address: dshwang@postech.ac.kr.
authors.forename: Dong Soo
authors.initials: DS
authors.lastname: Hwang
mesh_terms: D000268:Adhesiveness; D000538:Aluminum Silicates / Q000737:chemistry; D002021:Buffers; D048271:Chitosan / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D012995:Solubility; D013499:Surface Properties
chemical_list: D000538:Aluminum Silicates; D002021:Buffers; D048271:Chitosan; C011934:mica
keywords: Adhesion; Biomolecule; Cohesion; Low molecular weight chitosan; Solubility; Surface forces apparatus