Precontrolled Alignment of Graphite Nanoplatelets in Polymeric Composites Prevents Bacterial Attachment

Abstract

Graphene coatings composed of vertical spikes are shown to mitigate bacterial attachment. Such coatings present hydrophobic edges of graphene, which penetrate the lipid bilayers causing physical disruption of bacterial cells. However, manufacturing of such surfaces on a scale required for antibacterial applications is currently not feasible. This study explores whether graphite can be used as a cheaper alternative to graphene coatings. To examine this, composites of graphite nanoplatelets (GNP) and low‐density polyethylene (LDPE) are extruded in controlled conditions to obtain controlled orientation of GNP flakes within the polymer matrix. Flakes are exposed by etching the surface of GNP–LDPE nanocomposites and antibacterial activity is evaluated. GNP nanoflakes on the extruded samples interact with bacterial cell membranes, physically damaging the cells. Bactericidal activity is observed dependent on orientation and nanoflakes density. Composites with high density of GNP (≥15%) present two key advantages: i) they decrease bacterial viability by a factor of 99.9999%, which is 10 000‐fold improvement on the current benchmark, and ii) prevent bacterial colonization, thus drastically reducing the numbers of dead cells on the surface. The latter is a key advantage for longer‐term biomedical applications, since these surfaces will not have to be cleaned or replaced for longer periods.

Graphene‐Based Antimicrobial Biomedical Surfaces

“…Previous studies by authors revealed also other interesting physical properties that these nanocomposites with aligned GNPs exhibit as: gas barrier properties, [79,80] enhanced mechanical performance, [81] or anisotropic electrical and thermal conductivity [78,81] . A schematic of the manufacturing process is shown on Figure 6, with more details found in our previous study [54] . Moreover, the experimental trials have included two types of LDPE, differing in viscosity by around one order of magnitude.…”

“…Graphene and graphene derivatives can be attached to other surfaces as coatings for example by electrical and chemical deposition methods, [14–16,38–40] layer‐by‐layer assembly [41,42] or various surface spreading methods [43–48] . Finally, gel spinning, [49] electrospinning, [50,51] layer‐by‐layer assembly [41,52,53] or melt extrusion [54] have been used to create graphene based antibacterial nanocomposites. The method of obtaining the antibacterial surfaces is essential as it dictates the extent to which such surfaces can be tuned in terms of orientation and distribution of the graphene and their upscaling potential.…”

“…The membrane exhibited a strong antibacterial performance with a 97.9 % reduction in viability of E. coli [35] . In another study, different graphene derivatives including zwitterionic graphene nanomaterials were synthesized with defined exposure, in terms of grafted polymer coverage and functionality, and isoelectric points [54] . The synthesized materials had strong bactericidal activity via trapping of bacterial cells as well as piercing of cell membrane due to nano knives effect suggesting that improvement in the solidity of agglomeration and orientation of nanomaterials could enhance the antimicrobial activity [57] .…”

“…Recently, we developed the method to prepare antibacterial surfaces from highly structured highly filled polymer nanocomposites based on graphite nanoplatelets [54] which showed strong bactericidal activity by eliminating 99.99 % of bacteria. One should highlight the antimicrobial activity achieved by the graphite nanoplatelets (GNP) and low‐density polyethylene (LDPE) composite is several orders of magnitude stronger than any previously reported using pristine graphene, graphene oxide, and reduced graphene oxide, used either as a coating or in solution [14,19,55] .…”

Mechanical Behavior of Melt-Mixed 3D Hierarchical Graphene/Polypropylene Nanocomposites

“…Over the last 15 years, the performance of high aspect ratio fillers has shown great promise and opened a wide range of opportunities in the area of polymer nanocomposites [ 1 ]. Consequently the use of different fillers of high-aspect ratio has led to the development of high-performance and multifunctional materials with a wide range of industrial applications, for example, as gas-barrier membranes [ 2 , 3 , 4 , 5 ], antibacterial surfaces [ 6 , 7 , 8 ], heat-sinks [ 9 , 10 ] and electronics [ 11 ].…”