Macromolecular Coatings Research Articles

Comparing the resilience of macromolecular coatings on medical-grade polyurethane foils

Foils made from elastomeric polymers, such as polycarbonate-based polyurethane (PCU), can combine desirable properties including flexibility, durability, and compliance. Still, their usage is often limited by their strongly autohesive behavior. To overcome this issue, surface coatings can be applied. Here, dopamine-based (dopa) and carbodiimide-mediated (carbo) coatings are compared by assessing their tribological performance and surface properties after long-term sliding tests, and after storage or sterilization. Even though both coating strategies achieve very good lubricity, the dopa-coatings are less resilient than the carbo-coatings. Thus, for such applications where extended sample storage or sterilization is required, covalent coatings should be preferred.

Macromolecular Coatings for Endotracheal Tubes Probed on An Ex Vivo Extubation Setup

AbstractEndotracheal intubation is indispensable in modern healthcare but typically entails two complications for the treated patients: biofouling‐induced infections and friction‐associated damage to the tissue. Coatings on the endotracheal tubes (ETT) may mitigate those problems, but they require a well‐defined testing method to assess their functionality. Here, such a testing setup is presented, which allows for conducting ex vivo extubation experiments in a reproducible manner. With this setup, different coating strategies that immobilize porcine gastric mucins on the ETT surface are compared. The results demonstrate that covalent coatings generated from lab‐purified mucins outperform the other variants in terms of their ability to decrease tissue damage, prevent lipid adsorption, and reduce cell attachment. With a similar approach as presented here, it should also be possible to evaluate macromolecular coatings generated on other medical tubing systems such as cardiac and urinary catheters and endoscopes.

Effects of Sterilization Methods on the Integrity and Functionality of Covalent Mucin Coatings on Medical Devices

AbstractRecent advances in the field of biomedical materials have demonstrated that covalent mucin coatings generated on polymeric materials have the potential to greatly improve the surface properties of medical devices such as their wettability, lubricity, and resistance toward biofouling. For such biopolymer‐based coatings to be used in a medical application, sterilization of the coated devices is mandatory. However, common sterilization methods such as autoclavation, ethylene oxide fumigation, as well as γ‐ or ultraviolet‐irradiation, create harsh conditions during the device treatment, and this might compromise the structural integrity and thus functionality of macromolecular coatings. Here, it is demonstrated that covalent mucin coatings generated on medical devices made from polyvinyl chloride, polyurethane, or polydimethylsiloxane are able to withstand such treatments—albeit to different extents. Among all treatments tested, ethylene oxide fumigation is identified as the most promising method as it maintains the coatings the best. The findings imply that the beneficial properties demonstrated for mucin coatings in vitro should indeed be transferable to applications in vivo.

Colloid Interaction Energies for Surfaces with Steric Effects and Incompressible and/or Compressible Roughness

Colloid aggregation and retention in the presence of macromolecular coatings (e.g., adsorbed polymers, surfactants, proteins, biological exudates, and humic materials) have previously been correlated with electric double layer interactions or repulsive steric interactions, but the underlying causes are not fully resolved. An interaction energy model that accounts for double layer, van der Waals, Born, and steric interactions as well as nanoscale roughness and charge heterogeneity on both surfaces was extended, and theoretical calculations were conducted to address this gap in knowledge. Macromolecular coatings may produce steric interactions in the model, but non-uniform or incomplete surface coverage may also create compressible nanoscale roughness with a charge that is different from the underlying surface. Model results reveal that compressible nanoscale roughness reduces the energy barrier height and the magnitude of the primary minimum at separation distances exterior to the adsorbed organic layer. The depth of the primary minimum initially alters (e.g., increases or decreases) at separation distances smaller than the adsorbed organic coating because of a decrease in the compressible roughness height and an increase in the roughness fraction. However, further decreases in the separation distance create strong steric repulsion that dominates the interaction energy profile and limits the colloid approach distance. Consequently, adsorbed organic coatings on colloids can create shallow primary minimum interactions adjacent to organic coatings that can explain enhanced stability and limited amounts of aggregation and retention that have commonly been observed. The approach outlined in this manuscript provides an improved tool that can be used to design adsorbed organic coatings for specific colloid applications or interpret experimental observations.

Macromolecular Coatings Enhance the Tribological Performance of Polymer‐Based Lubricants

AbstractIn many biomedical settings, hard surfaces cause friction and wear at interfaces. Surface coatings have been introduced to reduce tribological stress—especially at slow sliding velocities where boundary friction dominates. Here, the ability of coatings generated from differently charged macromolecules, i.e., poly(ethylene glycol) (uncharged), mucin (polyanionic), and poly‐l‐lysine (polycationic), to synergistically interact with polymer‐based lubricants is studied as they are also present in almost every body fluid. It is demonstrated that, in combination with solutions containing either poly(ethylene glycol) or hyaluronic acid, these surface‐bound macromolecules significantly reduce boundary friction and, in addition, protect the surfaces from wear formation. This is attributed to entanglement effects between surface‐bound and solubilized macromolecules, which are most efficient in the absence of repulsive electrostatic forces. The synergetic effects described here could help optimizing medical devices such as catheters, endotracheal tubes, stents, or contact lenses to reduce patient discomfort and prevent inflammatory reactions arising from tribological stress.

Dynamic Intermolecular Interactions Control Adsorption from Mixtures of Natural Organic Matter and Protein onto Titanium Dioxide Nanoparticles.

Engineered nanoparticles (NPs) will obtain macromolecular coatings in environmental systems, changing their subsequent interactions. The matrix complexity inherent in natural waters and wastewaters greatly complicates prediction of the corona formation. Here, we investigate corona formation on titanium dioxide (TiO2) NPs from mixtures of natural organic matter (NOM) and a protein, bovine serum albumin (BSA), to thoroughly probe the role of mixture interactions in the adsorption process. Fundamentally different coronas were observed under different NP exposure conditions and time scales. In mixtures of NOM and protein, the corona composition was kinetically determined, and the species initially coadsorbed but were ultimately limited to monolayers. On the contrary, sequential exposure of the NPs to pure solutions of NOM and protein resulted in extensive multilayer formation. The intermolecular complexation between NOM and BSA in solution and at the NP surface was the key mechanism controlling these distinctive adsorption behaviors, as determined by size exclusion chromatography (SEC) and in situ attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. Overall, this study demonstrates that dynamic intermolecular interactions and the history of the NP surface must be considered together to predict corona formation on NPs in complex environmental media.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications.

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Critical review: impacts of macromolecular coatings on critical physicochemical processes controlling environmental fate of nanomaterials

Challenges in predicting effects of macromolecules on nanoparticle behavior.

Macromolecular approaches to prevent thrombosis and intimal hyperplasia following percutaneous coronary intervention.

Cardiovascular disease remains one of the largest contributors to death worldwide. Improvements in cardiovascular technology leading to the current generation of drug-eluting stents, bioresorbable stents, and drug-eluting balloons, coupled with advances in antirestenotic therapeutics developed by pharmaceutical community, have had a profound impact on quality of life and longevity. However, these procedures and devices contribute to both short- and long-term complications. Thus, room for improvement and development of new, alternative strategies exists. Two major approaches have been investigated to improve outcomes following percutaneous coronary intervention including perivascular delivery and luminal paving. For both approaches, polymers play a major role as controlled research vehicles, carriers for cells, and antithrombotic coatings. With improvements in catheter delivery devices and increases in our understanding of the biology of healthy and diseased vessels, the time is ripe for development of novel macromolecular coatings that can protect the vessel lumen following balloon angioplasty and promote healthy vascular healing.

Gummic acid stabilized γ-Fe2O3 aqueous suspensions for biomedical applications

Biomedical applications of magnetic nanoparticles depend critically on their preparation as aqueous colloidal suspensions, or ferrofluids, with long term stability under physiological conditions. Dispersion of the magnetic nanoparticles is generally achieved by the use of protein cages, polysaccharide, polypeptide and charged macromolecular coatings, which minimize interparticle magnetic interactions, particle agglomeration and precipitation. The synthesis and characterization of gummic-acid stabilized maghemite ferrofluids is reported. X-ray diffraction, transmission electron microscope and dynamic light scattering measurements give a γ-Fe2O3 magnetic core diameter of 8 nm and a nanocomposite particle hydrodynamic diameter of 50 nm. Mossbauer and magnetization measurements indicate the presence of isolated, sterically stabilized superparamagnetic nanoparticles resistant to aging, and thus, promising agents for the production of novel magneto-pharmaceuticals.

Characterization of PEG-Like Macromolecular Coatings on Plasma Modified NiTi Alloy

A poly (ethylene glycol) (PEG-like) coating was developed to improve the biocompatibility of Nickel-Titanium (NiTi) alloy implants. The PEG-like macromolecular coatings were deposited on NiTi substrates at a room temperature of 298 K through a ECR (electron-cyclotron resonance) cold-plasma enhanced chemical vapor deposition method using tetraglyme (CH3-O-(CH2-CH2-O)4-CH3) as a precursor. A power supply with a frequency of 2.45 GHz was applied to ignite the plasma with Ar(argon) used as the carrier gas. Based on the atomic force microscopy (AFM) studies, a thin smooth coating on NiTi substrates with highly amorphous functional groups on the modified NiTi surfaces were mainly the same accumulated stoichiometric ratio of C and O with PEG. The vitro studies showed that platelet-rich plasma (PRP) adsorption on the modified NiTi alloy surface was significantly reduced. This study indicated that plasma surface modification changes the surface components of NiTi alloy and subsequently improves its biocompatibility.