Directing Interfacial Events Using Biomimetic Polymer Brushes

Polymer brushes;biomedical coatings;zwitterionic polymer brushes;statistical modeling;glycopolymers;virus-resistant coatings;Chemical Engineering;Engineering;Chemical Engineering

Kumar, RamyaScott, Timothy ;

University of Michigan

关键词: Polymer brushes;    biomedical coatings;    zwitterionic polymer brushes;    statistical modeling;    glycopolymers;    virus-resistant coatings;    Chemical Engineering;    Engineering;    Chemical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/144127/rmykmr_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Polymer brushes are versatile surface modification tools, wherein composition, architecture and biological functionality can be controlled precisely and independently. By growing biomimetic polymer chains from substrate-bound initiator sites through atom transfer radical polymerization (ATRP), engineered biointerfaces were developed for four application areas. Spatioselective deactivation of ATRP initiator coatings made via chemical vapor deposition polymerization was demonstrated to synthesize micropatterned polymer brushes in a substrate-independent, modular and facile manner. Exposure of 2-bromoisobutyryl groups to UV light resulted in the loss of the bromine atom and effectively inhibited polymer brush growth. Microstructured brushes were selectively grown from those areas on the initiator that were protected from UV exposure, as confirmed by atomic force microscopy (AFM), Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and imaging ellipsometry. Protein patterns based on specific as well as non-specific adsorption can be created on technologically relevant substrates such as polystyrene, PDMS, polyvinyl chloride and steel.Model surfaces can aid in examining different hypotheses relevant to viral adsorption and formulating design rules for virus-resistant coatings. Thermodynamic models predicted that the extent of viral adsorption is shaped by the interplay between electrostatic attraction offered by binding sites and steric and hydration repulsions arising from surrounding polymer brushes. To verify these predictions, electrostatically heterogeneous carbohydrate-functional brushes were developed. Experimental results confirmed model predictions and offered guidelines for designing virus-resistant surfaces in realistic scenarios where electrostatically attractive defects are prevalent. By allowing the carbohydrate brushes to attain brush thicknesses between 3-5 nm, low levels of protein and viral adsorption could be achieved, even when the defect density was as high as 25-30%.The development of polymeric materials that facilitate the culture of large numbers of human pluripotent stem cells in fully defined conditions, poses a critical engineering challenge. Prior work had indicated that modifying the extent of zwitterionic self-association of PMEDSAH coatings could enhance the propagation rate of human embryonic stem cells (hESCs). Moderately self-associated PMEDSAH coatings were reported to be capable of expanding an initial population of 20,000 hESCS to 4.7 billion pluripotent cells at the end of five weeks, which is 2-fold and 12-fold higher than the estimated propagation rates for unassociated and highly associated coatings respectively. It was hypothesized that a property-prediction tool based on statistical design of experiments could identify reaction parameters that would yield targeted gel architectures. Model predictions were used to decrease the critical thickness at which the wettability transition occurs by merely increasing the catalyst quantity from 1 mol% to 3 mol%.Pro-regenerative M2 macrophages (M2 Mps) have the potential to remediate chronic inflammation in a spectrum of disorders pertaining to macrophage polarization, such as diabetic wounds. By targeting the CD206 receptor on these cells using mannose molecules presented in multivalent architectures, we could engineer coatings that preferentially adhered to M2 cells over pro-inflammatory M1 cells. While a selectivity ratio (for M2 over M1) between 6 to 7 was observed on mannosylated surfaces, the control glucosylated surfaces did not discriminate between M1 and M2 phenotypes, exhibiting a selectivity ratio between 0.4 to 0.7. By applying insights from polymer chemistry, surface science, and thermodynamics, an intimate understanding of biomedically relevant interfacial phenomena was acquired. This enabled the development of a platform based on multifunctional polymer brushes to address diverse problems at the interface of polymers and biology.