Development of Functional Polyelectrolyte Coatings with Antifouling & Lubricating Applications in Bioengineering and Study of the Associated Surface Interaction Mechanisms

• Author / Creator

  Han, Linbo

• The fabrication of functional polyelectrolyte coatings by employing reliable anchoring mechanisms has attracted great attention due to their wide range of potential applications. In this thesis, we develop robust-anchored functional coatings, especially polyelectrolyte coatings, for endowing the substrates with efficient antifouling and/or lubricating properties in bioengineering, and further investigate the related surface interaction mechanisms using nanomechanical techniques including atomic force microscope (AFM), surface forces apparatus (SFA) and quartz crystal microbalance with dissipation monitoring (QCM-D). Adsorption and desorption of biomolecules on/from polyelectrolyte surfaces play a critical role in numerous biomedical and engineering applications. Though some weak polyelectrolytes have been developed for protein adsorption and desorption by regulating the salinity and pH, limited reports are available about the regeneration of strong polyelectrolyte surfaces between protein-attractive and protein-repulsive states, which is highly desirable but challenging to realize as it is more difficult to fully release the pre-adsorbed proteins from strong polyelectrolytes due to their permanent charges comparing to weak polyelectrolytes. We report a strategy to facilely tune the resistance to nonspecific protein adsorption onto a charged (cationic poly([2-(methacryloyloxy) ethyl] trimethylammonium chloride) (PMTAC) or anionic Poly(3-sulfopropyl methacrylate potassium salt) (PSPMA)) strong polyelectrolyte brush coating via salinity adjustment. It has been demonstrated that the charged polyelectrolyte coating displays strong adhesion to proteins at low salinity (e.g., 0.1 mM NaCl) but protein-repellent property at high salinity (e.g., 1.0 M NaCl). The adsorbed proteins on the strong polyelectrolyte coatings under low salinity condition could be readily removed via rinsing with high-salinity water, demonstrating the excellent surface regeneration capability. An outstanding anchoring ligand with robust anchoring ability and universal applicability is highly desirable in materials science and surface engineering. We report a novel and universal mussel-inspired anchoring strategy based on cationic amine-modified catechol ligand coupled with 2-methacryloyloxyethyl phosphorylcholine (MPC) moiety. The ligand shows substrate-independent anchoring capability, and the deposited film possesses excellent antifouling properties and superior ultrasonic stability as compared to conventional catechol ligand. Single-molecule force spectroscopy based on atomic force microscopy reveals that the enhanced ultra-stable anchoring is attributed to the synergistic binding effect of cationic amine and catechol. Our results provide new nanomechanical insights into the development of novel coating strategies underwater based on amine-incorporated catechol derivatives for a wide range of materials chemistry, bioengineering and environmental applications. Polyelectrolyte brush coatings have been developed as excellent boundary lubricants in aqueous media due to the lubricating behavior of tenaciously attached but labile water molecules on charged segments, as well as the suppressed mutual interpenetration of opposing polyelectrolyte chains under a high compression. Development of smart surfaces with tunable interfacial lubrication by external stimuli broads their applications in aqueous media and helps to gain better understanding of lubricating mechanisms. We report a salinity-responsive cationic PMTAC brush coating, whose lubricating properties could be facilely tuned from an excellent lubrication with friction coefficient μ100mM). Such controllable lubricating behaviors of charged PMTAC brush coating are mainly attributed to salinity effects on the chain conformation of PMTAC brushes and electrostatic interactions between sliding PMATC coatings, paving the way of developing rational strategies for fabrication of smart polyelectrolyte brush coatings with tunable lubricating properties for various biomedical and engineering applications. Bioinspired zwitterionic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) has been widely used for fabrication of lubricating surfaces due to its excellent surface hydration ability and biocompatibility. However, simplifying the process of immobilizing PMPC on substrates for achieving excellent boundary lubrication is still remains as a challenge. Here, a simple and facile one-step dip-coating method is developed to anchor PMPC on various surfaces via co-deposition of poly(dopamine methacrylamide)-co-poly(2-methacryloyloxyethyl phosphorylcholine) (PDMA-co-PMPC) and dopamine (DA) in a mild condition. The as-fabricated PDA/PDMA-co-PMPC coatings not only exhibit excellent lubricating properties (μ=0.036±0.002, 2.8MPa) when sliding with each other, but also can lubricate a model albumin (bovine serum albumin (BSA)) layer (μ=0.041±0.005, 4.8MPa) in phosphate-buffered saline (PBS). Intriguingly, both systems show Amontons-like behaviors: the friction is directly proportional to the applied load and the kinetic friction is independent of the shear velocity. Moreover, the PDA/PDMA-co-PMPC coatings could resist the BSA fouling in PBS, which is crucial to prevent the surfaces from being contaminated when applied in biological media, thus maintaining their lubricating properties.

• Subjects / Keywords

  • Bio-antifouling
  • Surface interaction mechanism
  • Hydration lubrication
  • Polyelectrolyte

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3QJ78D07

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.