Using nonthermal plasma treatment to improve quality and durability of hydrophilic coatings on hydrophobic polymer surfaces

Abstract

Low surface energy substrates, which include many polymers in medicine/industry, present challenges toward achieving uniform, adherent, durable coatings, thus limiting intended coating function. Examples include hydrophobic polymers such as polypropylene, polyethylene, polytetrafluoroethylene, and polydimethylsiloxane. These inert materials are used in various biomedical implants due to favorable bulk properties despite perhaps unfavorable surface properties. The capability to coat such materials holds great value as the surface heavily influences biological response and implant function in vivo. Likewise, paint/ink coatings are often necessary on these same plastics, as their final appearance can be critical for automotive, packaging, and consumer products. Substrate exposure to nonthermal plasma was explored here as a means to improve quality of coatings, specifically cyclodextrin-based polyurethanes previously explored for biomedical applications such as controlled drug delivery and antibiofouling, upon otherwise incompatible polypropylene substrates. Plasma treatment was found to increase wettability and oxygen content on substrate surfaces. These plasma-induced surface alterations were associated with enhanced coating uniformity, and improved coating/substrate adherencedetermined to derive partly from interfacial covalent bond formation. Findings demonstrate the utility of plasma-based surface activation as a strategy to improve coating quality on polymeric substrates, and reveal insights regarding mechanisms by which plasma improves polymer coating adherence.2 reduction of non-specific protein adsorption or bacterial attachment, sustained drug release, enhancement of attachment of certain host cells, and prevention of corrosion.A large number of biomedical implants are composed of polymers that possess low surface energy. Such polymeric materials include: 1) polypropylene (PP), present in surgical meshes and sutures, 2) polyethylene (PE), found in total joint replacements, 3) polydimethylsiloxane (PDMS), utilized in plastic surgery, and 4) polytetrafluoroethylene (PTFE), used for catheters and arterial grafts. The low surface energy of these materials is disadvantageous for several reasons: (i) it promotes adsorption and denaturation of proteins on the bare surface, along with subsequent inflammatory responses, as it is favorable for proteins to displace water at the hydrophobic surface and change conformation to allow core nonpolar amino acids to associate with the material 1 , and (ii) it decreases the receptiveness of these materials toward coatings 2 , which could otherwise allow for improved host response and device function. In general, the surface energy of a substrate should exceed that of a coating to achieve reasonable spreading and adhesion. If not, coatings applied to low surface energy substrates suffer from lack of uniformity, adherence, and durability, limiting the intended function of the coating over the lifetime of the implant.An attractive solution to promote uniformity and adherence of c...

Affinity Effects on the Release of Non-Conventional Antifibrotics from Polymer Depots

“…We herein used both in silico and in vitro measurements to predict and confirm the relative affinity of the selected drugs for β-CD or the base polymer without inclusion complex formation, dextran (Figures 1 and 2). Previous studies have demonstrated using cyclodextrin monomers polymerized into larger macrostructures such as coatings, disks, and particles in order to delay drug release by achieving a high concentration of affinity-binding sites [27,30,31,37,44,45]. The release results herein show differences in the loading efficiencies (Figure 3), release rates ( Figure 4), and cumulative amounts of drug release ( Figure 5) which may inform the future use and design of local drug delivery depots.…”

Cyclodextrin polymer coatings resist protein fouling, mammalian cell adhesion, and bacterial attachment

“…To maximize pCD coating adherence and stability, PP substrates were placed in a 4" diameter x 8" length quartz reaction chamber of a Branson/IPC Model #1005-248 Gas Plasma Cleaner and treated with nonthermal plasma (500 mTorr, 50 W, 13.56 MHz) using an inlet gas mixture of argon bubbled through water (Ar/H2O) 81,83 . PP substrates were treated for a fixed 10 min duration within 1 h of pCD coating application or direct biofoulant exposure (for plasmatreated bare PP controls).…”

“…In this study, polymerized CD (pCD) was applied as a coating for polypropylene (PP), chosen as a model substrate material because of its susceptibility to uncontrolled biofouling in medical [70][71][72][73][74] and industrial [75][76][77][78][79][80] applications. Given the low surface energy of olefin polymers, PP substrates were treated with nonthermal plasma to enhance pCD coating uniformity and adherence 81 . We hypothesized that pCD coatings would deter protein adsorption, cell adhesion, and bacterial attachment to PP substrates, in a manner dependent on crosslinking.…”