Ingenium 2017

Page 33

Ingenium 2017

Investigating Antibacterial Properties of Plasma Cleaned Polypropylene Anthony Galante and Paul Leu Laboratory of Advanced Materials in Pittsburgh, Department of Industrial Engineering Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA, USA

Abstract The cleanliness of plastics has become a priority in the modern age of technology, especially in the biomedical field. Preventing contamination of plastic surfaces is an absolute standard to prevent infections or ensure the effectiveness of a biomedical device. Plasma cleaning is a technique known for the unique physiochemical reactions that occur on a substrate’s surface during cleaning. Changes of wettability and adhesion from these physiochemical modifications have been observed on various polymers. In this work, the changes in wettability and bacterial adhesion on polypropylene substrates caused by various plasma cleaning recipes were observed. This study aims to accommodate research toward creating self-cleaning surfaces for biomedical purposes. Keywords: biomedical, polymer, plasma, clean

1. Introduction Polypropylene (PP) is one of the most commonly used biomedical polymers for its unique properties such as rigidness and resistance to chemical solvents. Using this plastic for biomedical applications seems attractive, but the polymer is prone to infections when additional surface treatment is not viable [3]. Infection of biomedical polymers is one of the major hospital-induced complications that can occur during a patient’s treatment. According to the American Association of Critical-Care Nurses, the most common infection from medical polymer devices is a catheter-associated urinary tract infection (CAUTI) [6]. In order to prevent the possibility of infections from hospital devices, antibacterial surface properties of treated polymers are desirable. Approaches for creating antibacterial polymer surfaces include mixing antibacterial reagents in bulk polymers, copolymerization of antibacterial reagents and surface modification of polymer substrates [2]. Surface modification methods involve altering the physiochemical interactions between bacteria and the polymer surface

without damaging the bulk properties of the polymer [5]. Plasma surface modification is relatively expensive; however, advantageous for biomedical applications. Plasma immersion ion implantation (PIII), an extension to the plasma surface modification process, has been done on polyethylene and polyvinyl chloride with triclosan for effective antibacterial response [5]. Various gas plasmas were coupled with antibacterial agent deposition on polymer surfaces to enhance the surface antibacterial properties. This process is faster and possibly more efficient for mass production of biomedical products than other cleaning techniques. Our research focused on how gas plasma alone can be used to alter the surface antibacterial properties for polymers, specifically PP. Polypropylene surfaces were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and contact angle measurements; also, bacterial adhesion properties were evaluated by plate-counting of Staphylococccus Aureus bacteria. Plasma cleaning was observed to significantly alter the surface wettability and roughness at the microscale. Additionally, plasma treatments altered the bacterial adhesion of S. aureus.

2. Methods Polypropylene sheets with 0.0675-inch thickness were purchased from an online vendor and met ASTM D41010112 specifications regarding the chemical and structural integrity of the specimens. Polypropylene discs of equal 0.5-inch diameter were made by a custom hole punch supplied by the Swanson Center for Product Innovation. Afterward, disc samples were cleaned of all organics and solvents with acetone, methanol, and isopropyl alcohol. Samples were plasma cleaned at the Gertrude E. and John M. Petersen Institute of NanoScience and Engineering at the University of Pittsburgh. Plasma cleaning or reactive ion etching (RIE) involves the bombardment of surfaces by activated ions from radio frequency gas plasma.

Undergraduate Research at the Swanson School of Engineering


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