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    Biomaterials

    (C-86) Molecular Weight Influence on Surface Properties of Immobilized Biomimetic Brush

    Friday, October 13, 2023
    3:30 PM – 4:30 PM PDT
    Location: Exhibit Hall - Row C - Poster # 86
    Introduction:: Nosocomial infections, commonly known as Hospital-Acquired Infections (HAI), are acquired during medical care, resulting from exposure to contaminated medical devices such as catheters, wound dressings, stents, and more. In 2020, HAI affected approximately 5% of hospitalized patients; of those 5%, 75,000 cases led to casualty [1]. Conventional antibiotics are administrated for nosocomial infections, but their therapeutic efficiency is affected due to increasing drug resistance [2]. For example, each year, over 2 million people in the US experience an infection resistant to antibiotics [3]. Due to the increasing emergence of antibiotic resistance, research of novel antibacterial therapeutics gained significant attention over the past decade. For example, surface coatings with anti-fouling capabilities have been developed with enhanced biocompatibility to combat nosocomial infections. Fouling indicates the accumulation of bacteria on the medical device, which can eventually lead to biofilm formation and more serious complications. In this study, a surface immobilized biomimetic brush is being explored for biomaterial applications for its potential anti-fouling properties. The impact of the brush’s molecular weight (MW) on its anti-fouling behavior was explored. 

    Materials and Methods:: For fabrication of brush immobilized polymers, polymer films were cut and plasma treated, resulting in hydroxyl group formation on the polymer surface. The films were then placed in 10 volume percent aminosilane ethanol solution. To create oxidized solutions, various MW of the brush solution was prepared with sodium metaperiodate (NaIO4). Unreacted NaIO4 was removed by dialysis against deionized water (DI) for 24 hours. Polymer films were incubated in the oxidized brush solution under shaking conditions. Oxidized brushes were bound to the surface of the polymer through a Schiff base formation. Static contact angle measurements were performed using the Ossila Contact Angle Machine. Briefly, 5 µL DI was dispensed onto the films and the average angle of contact was measured (N=3). Surface composition was studied using The Fourier Transform Infrared (FTIR) Grazing Angle employed by the PerkinElmer FTIR Spectrometer.  Surface brush stability was determined using Uv-vis at 625nm. Samples were incubated in 0.1 wt.% anthrone and 95% sulfuric acid to form furfural. The detached bacteria were diluted and cultured on TSA/LB. The 24 hour bacterial adhesion assay used biomimetic brush-coated polymers exposed to E. coli ATCC25922, a gram-negative bacterium, and S. aureus ATCC 6538, a gram-positive bacterium (N=5). After 24 hours, the bacteria were detached from the surface through vortex and homogenizing. The detached bacteria were diluted and cultured on TSA/LB. Some details are intentionally not discussed due to pending patent. 

    Results, Conclusions, and Discussions::

    Brush-coated surface, when compared to the uncoated control polymer, showed significant decrease in contact angle (Figure 2). The polymer is deemed hydrophobic with an average static contact angle of 105°± 2.46, while the brush-coated surfaces had an average contact angle of 48.97° and were hydrophilic. Bacteria, to conserve energy, will bind to a surface with lower surface energy like the hydrophobic polymer [4]. The downward contact angle trend on the brush samples is expected due to the elongation in the brush’s chain caused by the increase in molecular weight. Elongation in the brush chain results in more hydrophilic groups and more surface area for water absorption [5]. The hydrophilicity of brush-coated polymers can have increased anti-fouling compatibility due to the high affinity for water, allowing the formation of a hydration layer. The FTIR analysis (Figure 3) proved surface brush immobilization. The O-H stretching, C-H stretching vibrations, and the C-O bands were marked in the corresponding locations, but it was presumed that an increase in molecular weight would correlate to the peaks at ~3400, 2850, 1650, and 1050 cm-1, though the results do not reveal this. This could be accredited to steric hindrance of the molecular size prohibiting complex molecules from binding to the surface. The range of the brush molecular weight resulted in an overall 1-2 log reduction against E. coli and S. aureus (Figures 4). The reduction in biofouling ranged from 50-83% reduction, proving potential antimicrobial properties of brush-coated surfaces. After the 24 hours in physiological condition, 50% of the immobilized brush remained stable, indicating that brush-coated material has the potential to improve anti-fouling capability of short-term medical devices such as intermittent catheter that stays in patient for 4-6 hours (Figure 5).  




    The biomimetic brush-coated polymers prove to have hydrophilic properties with an average contact angle of 48.97º, allowing for increased anti-fouling potential. FTIR confirmed the immobilization of the brush onto the polymer surface. A 24 hour adhesion showed reduction against both gram positive and negative bacteria. Therefore, brush-coated polymers have the potential to reduce fouling-related intermittent device failure due to their stability and anti-fouling properties. 




    Acknowledgements (Optional): : This material is based upon work supported by a National Science Foundation Research Experiences for Undergraduates (REU) site program under Grant No. 1950581. 

    References (Optional): :

    [1] Public Health, E. (n.d.). Diseases & topics. NC DPH: Healthcare-Associated Infections (HAIs). https://epi.dph.ncdhhs.gov/cd/diseases/hai.html  




    [2] World Health Organization. (n.d.). Antibiotic resistance. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/antibiotic-resistance#:~:text=These%20bacteria%20may%20infect%20humans,hospital%20stays%2C%20and%20increased%20mortality.   




    [3] Fukunaga, B. T., Sumida, W. K., Taira, D. A., Davis, J. W., & Seto, T. B. (2016, October). Hospital-acquired methicillin-resistant staphylococcus aureus bacteremia related to Medicare antibiotic prescriptions: A state-level analysis. Hawai’i journal of medicine & public health : a journal of Asia Pacific Medicine & Public Health. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5056633/   




    [4] Oh, J. K., Yegin, Y., Yang, F., Zhang, M., Li, J., Huang, S., Verkhoturov, S. V., Schweikert, E. A., Perez-Lewis, K., Scholar, E. A., Taylor, T. M., Castillo, A., Cisneros-Zevallos, L., Min, Y., & Akbulut, M. (2018, November 22). The influence of surface chemistry on the kinetics and thermodynamics of bacterial adhesion. Scientific reports. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6250697/  




    [5] Krasowska, A., & Sigler, K. (2014, July 29). How microorganisms use hydrophobicity and what does this mean for human needs?. Frontiers. https://www.frontiersin.org/articles/10.3389/fcimb.2014.00112/full