Understanding the role of polymer surface nanoscale topography on inhibiting bacteria adhesion and growth

Abstract

Event Abstract Back to Event Understanding the role of polymer surface nanoscale topography on inhibiting bacteria adhesion and growth Luting Liu1 and Thomas J. Webster1, 2 1 Northeastern University, Department of Chemical Engineering, United States 2 King Abdulaziz University, Center of Excellence for Advanced Materials Research, Saudi Arabia Introduction: Currently, the use of nanostructured materials, especially materials with nanofeatured topographies, which have more surface area, altered surface energy, enhanced select protein adsorption, selectively increased desirable cell functions while simultaneously decreasing competitive cell functions, seem to be among the most promising ways for reducing initial bacteria attachment, biofilm formation and infection[1]. Also, natural surfaces, such as cicada wing surfaces, appear to be bactericidal to Pseudomonas aeruginosa, which was thought to be due to the nanostructure surface of the wing rather than a chemical effect[2]. Motivated by these findings, this study aimed to modify the raw surface of a catheter composed of polydimethylsiloxane (PDMS) to possess antibacterial nanostructures, and then to develop a mathematical model that can correlate nanosurface roughness with protein adsorption and bacteria adhesion. Materials and Methods: Here, we present a simple method to prepare a nano-patterned PDMS replica by using nanotubular anodized titanium as the template (Fig. 1)[3]. The surface morphogy and elemental composition of PDMS were characterized by SEM, AFM, and XPS. In vitro bacterial studies using Staphylococcus aureus (ATCC 25923) and Escherichia coli (ATCC 25922) were conducted to assess the effectiveness of the nano-patterned PDMS (nano-PDMS) at inhibiting bacteria adhesion and growth. In addition, human fibroblast (ATCC, CCL-110) and endothelial cell (Life Technologies) MTT assays were conducted to determine the toxicity of the nanostructure to mammalian cells. To study the mechanism of these nanostructured features towards inhibiting bacteria adhesion and growth, the adsorption of proteins from tryptic soy broth that influence bacteria functions were determined. Results and Discussion: As expected, the nano-patterned structures were fabricated successfully on the surface of PDMS without changing its surface chemistry. In vitro studies indicated that nano-PDMS inhibited the adhesion and growth of both two bacteria after 48h compared with plain-PDMS. Moreover, data suggested the effectiveness of bacteria inhibition reached above 50%, all without employing antibiotics (Fig. 2). It was also found that nano-PDMS increased both fibroblast and endothelial cell adhesion after 4h of treatment. A bicinchoninic acid protein assay kit was used to quantify the amount of proteins adsorbed on the sample surfaces. Results indicated that the increase of nanoscale surface roughness caused a significant increase of the amount of adsorbed proteins with a maximum value occurred at 1h (Fig. 3). The increased protein adsorption on the nano-PDMS in the first several minutes could in part be responsible for the antibacterial properties. Conclusions: The relationship between the nanosurface roughness, protein adsorption and bacteria activities was investigated in this study. Data showed that the increased nanoscale surface roughness could increase the amount of proteins adsorbed, specifically, casein, inhibiting both bacteria adhesion and growth significantly while remaining non-toxic to mammalian cells. These results together indicated that the present biomimetic nano-patterned PDMS surface (without any chemical or antibiotic modification) should strongly be considered for reducing infections in catheters and other implanted biomaterials.