Nonthermal plasma treatment of polymers modulates biological fouling but can cause material embrittlement

Abstract

Plasma-based treatment is a prevalent strategy to alter biological response and enhance biomaterial coating quality at the surfaces of biomedical devices and implants, especially polymeric materials. Plasma, an ionized gas, is often thought to have negligible effects on the bulk properties of prosthetic substrates given that it alters the surface chemistry on only the outermost few nanometers of material. However, no studies to date have systematically explored the effects of plasma exposure on both the surface and bulk properties of a biomaterial. This work examines the time-dependent effects of a nonthermal plasma on the surface and bulk properties of polymeric implants, specifically polypropylene surgical meshes and sutures. Findings suggest that plasma exposure improved resistance to fibrinogen adsorption and Escherichia coli attachment, and promoted mammalian fibroblast attachment, although increased duration of exposure resulted in a state of diminishing returns. At the same time, it was observed that plasma exposure can be detrimental to the material properties of individual filaments (i.e. sutures), as well as the structural characteristics of knitted meshes, with longer exposures resulting in further embrittlement and larger changes in anisotropic qualities. Though there are few guidelines regarding appropriate mechanical properties of surgical textiles, the results from this investigation imply that there are ultimate exposure limits for plasma-based treatments of polymeric implant materials when structural properties must be preserved, and that the effects of a plasma on a given biomaterial should be examined carefully before translation to a clinical scenario.

Nonthermal Plasma Treatment Improves Uniformity and Adherence of Cyclodextrin-Based Coatings on Hydrophobic Polymer Substrates

“…Deconvolutions of high-resolution C1s scans suggested that most engrafted oxygen was incorporated as hydroxyl groups, with lesser amounts as ketones/aldehydes and carboxyls/esters, for all tested plasma durations. This finding is in agreement with previous reports [17,37]. However, the abundance of hydroxyl groups leveled off after 10 min of treatment, as existing hydroxyls were oxidized further to species such as ketones, carboxylic acids, or possibly even carbonates [38,39,41].…”

“…The former strategy represents a greener chemistry process, and eliminates the risk for residual hazardous compounds, which is especially important for any materials that may ultimately come into contact (directly or indirectly) with human cells or tissues (e.g., medical devices, water treatment filters/membranes). Furthermore, appropriate selection of plasma treatment parameters can ensure minimal impact on bulk mechanical properties of load-bearing substrates [17]. Apart from CD-based coatings, findings herein support the use of substrate plasma activation for improving uniformity and adherence of adhesives or paints (especially polyurethane-based formulations) upon low surface energy substrates such as polyolefins.…”

“…However, the abundance of hydroxyl groups leveled off after 10 min of treatment, as existing hydroxyls were oxidized further to species such as ketones, carboxylic acids, or possibly even carbonates [38,39,41]. These latter two oxygen-rich functional groups can only be created through chain scission at the substrate surface, and such degraded polymer chains may embrittle the PP material [17]. Furthermore, loss of hydroxyl groups at the PP surface might be predicted to decrease the extent of interfacial covalent bonding with the polyurethane coating, as hydroxyls undergo expected reaction with isocyanates [43,44].…”

“…Interaction of nonthermal plasma with a polymer surface results in cleaning or etching, bond scission or rearrangement, and the introduction of new functional groups as determined by the carrier gas composition. These plasma-induced changes can promote substrate receptiveness to coatings [16], and also directly alter biological responses at the substrate surface [17]. Furthermore, plasma treatments circumvent the need for hazardous chemicals (e.g., solvents) as adhesion promoters, are amenable for substrates with complex geometries, and can achieve desirable surface changes while minimizing impact on the substrate material bulk properties [17].…”

Cold plasma surface treatments to prevent biofilm formation in food industries and medical sectors

“…Bacterial adhesion decreased after 1 min of plasma treatment (p > 0.048) whereas after 10 min and 20 min of plasma treatment, the bacterial attachment rate, in comparison with the 1-min rate, was reduced by half (p < 0.001). These results imply that the time exposure of a surface to plasma treatments affects its chemical properties and behavior towards microorganisms (Gd et al 2020). Furthermore, Lin et al (2020) elaborated effective antiadhesive coatings towards Escherichia coli.…”