Lubricin on Platinum Electrodes: A Low‐Impedance Protein‐Resistant Surface Towards Biomedical Implantation

Abstract

Biofouling on surfaces compromises the function of biomedical devices whose function involves contact with biological fluids. In the context of electrochemical devices, proteins are attracted to the surface via coaction of various forces (hydrogen bond, hydrophobic effect, and other polar interactions) and protein interaction with the surface can significantly alter the surface chemistry. In response to this issue, we have developed an efficient anti-biofouling surface that employs a glycoprotein, lubricin (LUB), and which generates low impedance layers compatible with electrochemical applications. Herein, we investigate how different LUB densities on platinum (Pt) electrodes affect the surface electrochemistry and its ability to prevent nonspecific adsorption of protein to the surface. Surfaces with higher densities of LUB were more resistant to protein adsorption. The LUB modified Pt electrodes were challenged in artificial perilymph (AP) media under passive and electrically stimulated conditions over 7-day periods throughout which the LUB layer retained its anti-biofouling and surface coating stability.

Cellular Interactions with Lubricin and Hyaluronic Acid–Lubricin Composite Coatings on Gold Electrodes in Passive and Electrically Stimulated Environments

“…Likewise, it is also unlikely that the electrode polarization regiment produced any significant loss of R-LUB due to surface desorption resulting from either the long incubation times or biphasic polarization regiment consistent with conclusions of previous studies of R-LUB-coated Pt electrodes performed in artificial perilymph media and similar stimulation conditions. 45 The experiments outlined here demonstrate that R-LUB can still mediate it is antiattachment (fibroblasts) properties, even after 96 h under electrical stimulation conditions. This suggests that R-LUB-coated electrodes are not only antifouling at the protein level but also retain their "cell-repellant" properties for at least 96 h.…”

“…Characterization of the electrochemical properties of N-LUB and R-LUB coatings, including electrochemical stability, in various highly fouling, protein-containing fluids including blood plasma and saliva has been carried out on several electrode materials including Au, 9 Pt, 45 carbon (glassy carbon, carbon black, and reduced graphene oxide), 41,43 and polypyrrole. 46 The viability of LUB-coated electrodes, antiadhesive properties, and electrochemical stability have been demonstrated up to 7 days in published reports on Pt 45 and polypyrrole 46 Au surfaces and an assessment of cell viability at 24, 48, and 72 h was conducted using an Image-IT DEAD Green viability stain (see Figure 1). Cell viability was high at all time points, with viability consistently above 95% on both the bare and N-LUB-coated Au surfaces, indicating that N-LUB coatings have negligible toxicity and minimal impact upon cell viability (see Figure S2 of the Supporting Information for fluorescent micrographs showing the viability staining at 72 h).…”

“…Effect of Electrical Stimulation in R-LUB, HA, and HA/R-LUB Antifouling Properties. Recent publications have demonstrated the potential of LUB-based antiadhesive coatings in both electrochemical biosensing in blood plasma 9 and saliva 41,43 as well as simulated bionic applications 45 in in vitro experiments conducted in artificial perilymph fluid using the cochlear pulse sequence over a span of 1 week. In all of these previous electrochemical studies, the stability and antiadhesive performance of the LUB-based coatings have been tested against protein-rich solutions and fluids.…”

“…24,28,34,44 In addition, self-assembled LUB layers deposited on gold (Au) and platinum electrode sensors have been shown to be electrochemically stable within a physiologically relevant electrochemical "window" of ±1.0 V while having virtually zero impact upon the demonstrated electrode electrochemical processes including the electrode impedance, capacitance, or interfacial faradic reactions. 9,45 Recent experiments conducted on recombinant LUB (R-LUB)-coated platinum electrodes in artificial perilymph fluid (a complex solution of proteins and amino acids) subjected to 8 h of continuous stimulation per day, using the cochlear implant pulse sequence, support R-LUB coating's potential utility as a bionic implant coating, demonstrating excellent fouling resistance over 1 week without any significant change in impedance over the duration of the experiment. 45 This same stability study was repeated using R-LUB-coated polypyrrole electrodes resulting in a similar inhibition of electrode fouling.…”

“…9,45 Recent experiments conducted on recombinant LUB (R-LUB)-coated platinum electrodes in artificial perilymph fluid (a complex solution of proteins and amino acids) subjected to 8 h of continuous stimulation per day, using the cochlear implant pulse sequence, support R-LUB coating's potential utility as a bionic implant coating, demonstrating excellent fouling resistance over 1 week without any significant change in impedance over the duration of the experiment. 45 This same stability study was repeated using R-LUB-coated polypyrrole electrodes resulting in a similar inhibition of electrode fouling. 46 While the electrode fouling resistance has been demonstrated against proteins and within complex fluids, the adhesion resistance of R-LUB against proteins does not guarantee similar adhesion resistance against cells that typically exhibit cell-surface receptor sites that can bind specifically to certain glycans or carbohydrate residues, which may be present on the native LUB (N-LUB), R-LUB, or hyaluronic acid (HA) molecules.…”