Synthesis of biomimetic segmented polyurethanes as antifouling biomaterials

Nanocontainers Against Biofouling and Corrosion Degradation of Materials: A Short Review With Prospects

The current state of the art in active corrosion prevention is based on the use of macromolecular containers that can store and release corrosion inhibitors particularly to the surface when corrosion develops. These corrosion inhibitor-containing nano- or microcontainers are subsequently infused into coatings, allowing them to self-heal. Especially, nanocontainers for self-healing coatings with controlled corrosion inhibitors, energy storage, cement fracture repair, and antifouling metal protection have recently been developed. Incorporating these nanocontainers into materials in small amounts (e.g., 5–10 wt% in paints) provided anticorrosion protection that was incomparably better than the current approaches. Furthermore, the materials developed had multifunctional properties, including self-healing, antibacterial, and antimicrobial properties. The primary goal of this review was to compile the different research studies that have been published in a variety of publications so that the reader may better understand the potential of these new types of nanotechnology and the prospects for nanocontainers.

Anti-Biofouling Polymers with Special Surface Wettability for Biomedical Applications

The use of anti-biofouling polymers has widespread potential for counteracting marine, medical, and industrial biofouling. The anti-biofouling action is usually related to the degree of surface wettability. This review is focusing on anti-biofouling polymers with special surface wettability, and it will provide a new perspective to promote the development of anti-biofouling polymers for biomedical applications. Firstly, current anti-biofouling strategies are discussed followed by a comprehensive review of anti-biofouling polymers with specific types of surface wettability, including superhydrophilicity, hydrophilicity, and hydrophobicity. We then summarize the applications of anti-biofouling polymers with specific surface wettability in typical biomedical fields both in vivo and in vitro, such as cardiology, ophthalmology, and nephrology. Finally, the challenges and directions of the development of anti-biofouling polymers with special surface wettability are discussed. It is helpful for future researchers to choose suitable anti-biofouling polymers with special surface wettability for specific biomedical applications.

The prospects of antimicrobial coated medical implants

The implants are increasingly being a part of modern medicine in various surgical procedures for functional or cosmetic purposes. The progressive use of implants is associated with increased infectious complications and prevention of such infections always remains precedence in the clinical settings. The preventive approaches include the systemic administration of antimicrobial agents before and after the surgical procedures as well as the local application of antibiotics. The relevant literature and existing clinical practices have highlighted the role of antimicrobial coating approaches in the prevention of implants associated infections, although the applications of these strategies are not yet standardized, and the clinical efficacy is not much clear. The adequate data from the randomized control trials is challenging because of the unavailability of a large sample size although it is compulsory in this context to assess the clinical efficacy of preemptive practices. This review compares the efficacy of preventive approaches and the prospects of antimicrobial-coated implants in preventing implant-related infections.

Silver- and Zinc-Decorated Polyurethane Ionomers with Tunable Hard/Soft Phase Segregation

Segmented polyurethane ionomers find prominent applications in the biomedical field since they can combine the good mechanical and biostability properties of polyurethanes (PUs) with the strong hydrophilicity features of ionomers. In this work, PU ionomers were prepared from a carboxylated diol, poly(tetrahydrofuran) (soft phase) and a small library of diisocyanates (hard phase), either aliphatic or aromatic. The synthesized PUs were characterized to investigate the effect of ionic groups and the nature of diisocyanate upon the structure-property relationship. Results showed how the polymer hard/soft phase segregation was affected by both the concentration of ionic groups and the type of diisocyanate. Specifically, PUs obtained with aliphatic diisocyanates possessed a hard/soft phase segregation stronger than PUs with aromatic diisocyanates, as well as greater bulk and surface hydrophilicity. In contrast, a higher content of ionic groups per polymer repeat unit promoted phase mixing. The neutralization of polymer ionic groups with silver or zinc further increased the hard/soft phase segregation and provided polymers with antimicrobial properties. In particular, the Zinc/PU hybrid systems possessed activity only against the Gram-positive Staphylococcus epidermidis while Silver/PU systems were active also against the Gram-negative Pseudomonas aeruginosa. The herein-obtained polyurethanes could find promising applications as antimicrobial coatings for different kinds of surfaces including medical devices, fabric for wound dressings and other textiles.

Anti-Periprosthetic Infection Strategies: From Implant Surface Topographical Engineering to Smart Drug-Releasing Coatings

Despite advanced implant sterilization and aseptic surgical techniques, periprosthetic bacterial infection remains a major challenge for orthopedic and dental implants. Bacterial colonization/biofilm formation around implants and their invasion into the dense skeletal tissue matrices are difficult to treat and could lead to implant failure and osteomyelitis. These complications require major revision surgeries and extended antibiotic therapies that are associated with high treatment cost, morbidity, and even mortality. Effective preventative measures mitigating risks for implant-related infections are thus in dire need. This review focuses on recent developments of anti-periprosthetic infection strategies aimed at either reducing bacterial adhesion, colonization, and biofilm formation or killing bacteria directly in contact with and/or in the vicinity of implants. These goals are accomplished through antifouling, quorum-sensing interfering, or bactericidal implant surface topographical engineering or surface coatings through chemical modifications. Surface topographical engineering of lotus leaf mimicking super-hydrophobic antifouling features and cicada wing-mimicking, bacterium-piercing nanopillars are both presented. Conventional physical coating/passive release of bactericidal agents is contrasted with their covalent tethering to implant surfaces through either stable linkages or linkages labile to bacterial enzyme cleavage or environmental perturbations. Pros and cons of these emerging anti-periprosthetic infection approaches are discussed in terms of their safety, efficacy, and translational potentials.

Biobased polyurethanes for biomedical applications

Polyurethanes (PUs) are a major family of polymers displaying a wide spectrum of physico-chemical, mechanical and structural properties for a large range of fields. They have shown suitable for biomedical applications and are used in this domain since decades. The current variety of biomass available has extended the diversity of starting materials for the elaboration of new biobased macromolecular architectures, allowing the development of biobased PUs with advanced properties such as controlled biotic and abiotic degradation. In this frame, new tunable biomedical devices have been successfully designed. PU structures with precise tissue biomimicking can be obtained and are adequate for adhesion, proliferation and differentiation of many cell's types. Moreover, new smart shape-memory PUs with adjustable shape-recovery properties have demonstrated promising results for biomedical applications such as wound healing. The fossil-based starting materials substitution for biomedical implants is slowly improving, nonetheless better renewable contents need to be achieved for most PUs to obtain biobased certifications. After a presentation of some PU generalities and an understanding of a biomaterial structure-biocompatibility relationship, recent developments of biobased PUs for non-implantable devices as well as short- and long-term implants are described in detail in this review and compared to more conventional PU structures.

A scope at antifouling strategies to prevent catheter-associated infections

The use of invasive medical devices is becoming more common nowadays, with catheters representing one of the most used medical devices. However, there is a risk of infection associated with the use of these devices, since they are made of materials that are prone to bacterial adhesion with biofilm formation, often requiring catheter removal as the only therapeutic option. Catheter-related urinary tract infections (CAUTIs) and central line-associated bloodstream infections (CLABSIs) are among the most common causes of healthcare-associated infections (HAIs) worldwide while endotracheal intubation is responsible for ventilator-associated pneumonia (VAP). Therefore, to avoid the use of biocides due to the potential risk of bacterial resistance development, antifouling strategies aiming at the prevention of bacterial adherence and colonization of catheter surfaces represent important alternative measures. This review is focused on the main strategies that are able to modify the physical or chemical properties of biomaterials, leading to the creation of antiadhesive surfaces. The most promising approaches include coating the surfaces with hydrophilic polymers, such as poly(ethylene glycol) (PEG), poly(acrylamide) and poly(acrylates), betaine-based zwitterionic polymers and amphiphilic polymers or the use of bulk-modified poly(urethanes). Natural polysaccharides and its modifications with heparin, have also been used to improve hemocompatibility. Recently developed bioinspired techniques yielding very promising results in the prevention of bacterial adhesion and colonization of surfaces include slippery liquid-infused porous surfaces (SLIPS) based on the superhydrophilic rim of the pitcher plant and the Sharklet topography inspired by the shark skin, which are potential candidates as surface-modifying approaches for biomedical devices. Concerning the potential application of most of these strategies in catheters, more in vivo studies and clinical trials are needed to assure their efficacy and safety for possible future use.

Specialty Tough Hydrogels and Their Biomedical Applications

Hydrogels have long been explored as attractive materials for biomedical applications given their outstanding biocompatibility, high water content, and versatile fabrication platforms into materials with different physiochemical properties and geometries. Nonetheless, conventional hydrogels suffer from weak mechanical properties, restricting their use in persistent load-bearing applications often required of materials used in medical settings. Thus, the fabrication of mechanically robust hydrogels that can prolong the lifetime of clinically suitable materials under uncompromising in vivo conditions is of great interest. This review focuses on design considerations and strategies to construct such tough hydrogels. Several promising advances in the proposed use of specialty tough hydrogels for soft actuators, drug delivery vehicles, adhesives, coatings, and in tissue engineering settings are highlighted. While challenges remain before these specialty tough hydrogels will be deemed translationally acceptable for clinical applications, promising preliminary results undoubtedly spur great hope in the potential impact this embryonic research field can have on the biomedical community.

Synthesis and characterisation of composite sulphonated polyurethane/polyethersulphone membrane for blood purification application

Polyurethane (PU) with three different functional groups: carboxyl, hydroxyl and sulphonyl group on its molecular structure were synthesised in this work. The synthesised material suppresses blood clotting and exhibits anticoagulant characteristics due to the presence of the important anionic groups. The synthesised PU was blended with polyethersulphone (PES) and fabricated into flat-sheet membrane to study the physico-chemical and biocompatibility properties of the PES membrane for blood purification application. PES-PU flat-sheet membranes were fabricated via the dry-wet phase separation technique. Different loading of PU (0, 1, 2, 3, 4, and 5%) blended with PES was studied and compared. Based on the in-vitro biocompatibility analysis of the membrane, it can be suggested that the membrane incorporated with PU has better anticoagulant properties compared to the pristine PES membrane. PU incorporation prolonged the clotting time, decreased the formation of thrombin, decreased soluble complement component 3a (C3a) generation and suppressed platelet adhesion and aggregation. The anionic groups on the membrane surface might bind to coagulation factors (antithrombin) and the calcium ions, Ca²⁺ and thus improve anticoagulant ability. Based on both physico-chemical and in-vitro studied, 4% loading of PU is the optimum loading for incorporation with PES membrane. These results suggested that the blended PES-PU membranes with good haemocompatibility allowed practical application in the field of blood purification.

Synthesis of polyurethanes with pendant azide groups attached on the soft segments and the surface modification with mPEG by click chemistry for antifouling applications

Polyurethane with pendant azide groups on the soft segment (PU-GAP) was prepared in this study to further increase the content of reactive azide groups and improve their surfaces enrichment for further functionalization. Polymer diols with pendant azide groups (GAP) were prepared by transforming the pendant chlorine groups at polyepichlorohydrin (PECH) into azide groups with sodium azide. The prepared PECH, GAP and PU-GAP was characterized by GPC, ¹H NMR and FTIR. Propargylic mPEG (mPEG-alkyne) was used as model surface modification reagents which was grafted on the prepared azido containing polyurethane films via click chemistry. The surface morphology, chemical composition and wettabilities were studied by SEM, XPS and water contact angle (WCA) analysis, respectively. SEM results demonstrated different surface topologies between mPEG modified PU surface and original PU surface. XPS and WCA analysis proved the successful grafting of mPEG on the pendant azide groups of PUs. The mPEG modified PU surfaces demonstrated good antifouling activities against model bacteria and mPEG with larger molecular weights modified surfaces showed better resistance efficiency to attachment of bacteria. Therefore, the surface reactive polyurethane we prepared can be a universal platform for further functionalization according actual applications.

Polyurethane with pendant azide groups on the soft segment which can be an universal platform for further functionalization according actual applications.

Zwitterionic sulfobetaine polymer-immobilized surface by simple tyrosinase-mediated grafting for enhanced antifouling property

Introducing antifouling property to biomaterial surfaces has been considered an effective method for preventing the failure of implanted devices. In order to achieve this, the immobilization of zwitterions on biomaterial surfaces has been proven to be an excellent way of improving anti-adhesive potency. In this study, poly(sulfobetaine-co-tyramine), a tyramine-conjugated sulfobetaine polymer, was synthesized and simply grafted onto the surface of polyurethane via a tyrosinase-mediated reaction. Surface characterization by water contact angle measurements, X-ray photoelectron spectroscopy and atomic force microscopy demonstrated that the zwitterionic polymer was successfully introduced onto the surface of polyurethane and remained stable for 7days. In vitro studies revealed that poly(sulfobetaine-co-tyramine)-coated surfaces dramatically reduced the adhesion of fibrinogen, platelets, fibroblasts, and S. aureus by over 90% in comparison with bare surfaces. These results proved that polyurethane surfaces grafted with poly(sulfobetaine-co-tyramine) via a tyrosinase-catalyzed reaction could be promising candidates for an implantable medical device with excellent bioinert abilities.

STATEMENT OF SIGNIFICANCE

Antifouling surface modification is one of the key strategy to prevent the thrombus formation or infection which occurs on the surface of biomaterial after transplantation. Although there are many methods to modify the surface have been reported, necessity of simple modification technique still exists to apply for practical applications. The purpose of this study is to modify the biomaterial's surface by simply immobilizing antifouling zwitterion polymer via enzyme tyrosinase-mediated reaction which could modify versatile substrates in mild aqueous condition within fast time period. After modification, pSBTA grafted surface becomes resistant to various biological factors including proteins, cells, and bacterias. This approach appears to be a promising method to impart antifouling property on biomaterial surfaces.

Antifouling and antimicrobial biomaterials: an overview

The use of implantable medical devices is a common and indispensable part of medical care for both diagnostic and therapeutic purposes. However, as side effect, the implant of medical devices quite often leads to the occurrence of difficult-to-treat infections, as a consequence of the colonization of their abiotic surfaces by biofilm-growing microorganisms increasingly resistant to antimicrobial therapies. A promising strategy to combat device-related infections is based on anti-infective biomaterials that either repel microbes, so they cannot attach to the device surfaces, or kill them in the surrounding areas. In general, such biomaterials are characterized by antifouling coatings, exhibiting low adhesion or even repellent properties towards microorganisms, or antimicrobial coatings, able to kill microbes approaching the surface. In this light, the present overview will address the development in the last two decades of antifouling and antimicrobial biomaterials designed to potentially limit the initial stages of microbial adhesion, as well as the microbial growth and biofilm formation on medical device surfaces.

Thiol-ol Chemistry for Grafting of Natural Polymers to Form Highly Stable and Efficacious Antibacterial Coatings

Bacterial contamination of surfaces and the associated infection risk is a significant threat to human health. Some natural antibacterial polymers with low toxicity are promising coating materials for alleviating pathogenic colonization on surfaces. However, widespread application of these polymers as antibacterial coatings is constrained by coating techniques which are not easily scalable due to stringent reaction conditions. Herein, thiol-ol reaction involving oxidative conjugation between thiol and hydroxyl groups is demonstrated as a facile technique to graft two natural polymer derivatives, agarose (AG) and quaternized chitosan (QCS), as antibacterial coatings on polymer and metal substrates. The substrate surfaces are first treated with oxygen plasma followed by UV-induced grafting of the polymers under atmospheric conditions. Dimercaprol, a FDA-approved drug, is used as both surface anchor and cross-linker of the polymer chains during grafting. The AG coating achieves >2 log reduction in Pseudomonas aeruginosa and Staphylococcus aureus biofilm formation, while the QCS coating reduces bacterial count from contaminated droplets on its surface by >95%. The coatings are noncytotoxic and exhibits a high degree of stability under conditions expected in their potential applications as antibacterial coating for biomedical devices (for AG), and for preventing pathogen transmission in the environment (for QCS).

Degradable polyurethane with poly(2-ethyl-2-oxazoline) brushes for protein resistance

The effects of chain length and graft density of poly(2-ethyl-2-oxazoline) on the protein resistance of degradable polyurethane-graft-poly(2-ethyl-2-oxazoline) with PCL as the soft segment have been investigated.

Antifouling polyurethanes to fight device-related staphylococcal infections: synthesis, characterization, and antibiofilm efficacy

In hospital settings, biofilm-based medical device-related infections are considered a threat to patients, the sessile growing bacteria playing a key role in the spreading of healthcare-associated infections. In recent decades, the design of antifouling coatings for medical devices able to prevent microbial adhesiveness has emerged as one of the most promising strategies to face this important issue. In order to obtain suitable antifouling materials, segmented polyurethanes characterized by a hard/soft domain structure, having the same hard domain but a variable soft domain, have been synthesized. The soft domain was constituted by one of the following macrodiols: polypropylenoxide (PPO), polycaprolactide (PCL), and poly-l-lactide (PLA). The effects of the polymer hydrophilicity and the degree of hard/soft domain separation on antifouling properties of the synthesized polyurethanes were investigated. Microbial adherence assays evidenced as the polymers containing PCL or PLA were able to significantly reduce the adhesion of Staphylococcus epidermidis with respect to the PPO-containing polymer.

Tyrosine-derived polycarbonate-silica xerogel nanocomposites for controlled drug delivery

Biodegradable polymer-ceramic composites offer significant potential advantages in biomedical applications where the properties of either polymers or ceramics alone are insufficient to meet performance requirements. Here we demonstrate the highly tunable mechanical and controlled drug delivery properties accessible with novel biodegradable nanocomposites prepared by non-covalent binding of silica xerogels and co-polymers of tyrosine-poly(ethylene glycol)-derived poly(ether carbonate). The Young's moduli of the nanocomposites exceed by factors of 5-20 times those of the co-polymers or of composites made with micron scale silica particles. Increasing the fraction of xerogel in the nanocomposites increases the glass transition temperature and the mechanical strength, but decreases the equilibrium water content, which are all indicative of strong non-covalent interfacial interactions between the co-polymers and the silica nanoparticles. Sustained, tunable controlled release of both hydrophilic and hydrophobic therapeutic agents from the nanocomposites is demonstrated with two clinically significant drugs, rifampicin and bupivacaine. Bupivacaine exhibits an initial small burst release followed by slow release over the 7 day test period. Rifampicin release fits the diffusion-controlled Higuchi model and the amount released exceeds the dosage required for treatment of clinically challenging infections. These nanocomposites are thus attractive biomaterials for applications such as wound dressings, tissue engineering substrates and stents.

Synthesis, characterization, and paclitaxel release from a biodegradable, elastomeric, poly(ester urethane)urea bearing phosphorylcholine groups for reduced thrombogenicity

Biodegradable polymers with high elasticity, low thrombogenicity, and drug loading capacity continue to be pursued for vascular engineering applications, including vascular grafts and stents. A biodegradable elastomeric polyurethane was designed as a candidate material for use as a drug-eluting stent coating, such that it was nonthrombogenic and could provide antiproliferative drug release to inhibit smooth muscle cell proliferation. A phosphorylcholine containing poly(ester urethane) urea (PEUU-PC) was synthesized by grafting aminated phosphorylcholine onto backbone carboxyl groups of a polyurethane (PEUU-COOH) synthesized from a soft segment blend of polycaprolactone and dimethylolpropionic acid, a hard segment of diisocyanatobutane and a putrescine chain extender. Poly(ester urethane) urea (PEUU) from a soft segment of polycaprolactone alone was employed as a control material. All of the synthesized polyurethanes showed high distensibility (>600%) and tensile strengths in the 20-35 MPa range. PEUU-PC experienced greater degradation than PEUU or PEUU-COOH in either a saline or lipase enzyme solution. PEUU-PC also exhibited markedly inhibited ovine blood platelet deposition compared with PEUU-COOH and PEUU. Paclitaxel loaded in all of the polymers during solvent casting continued to release for 5 d after a burst release in a 10% ethanol/PBS solution, which was utilized to increase the solubility of the releasate. Rat smooth muscle cell proliferation was significantly inhibited in 1 wk cell culture when releasate from the paclitaxel-loaded films was present. Based on these results, the synthesized PEUU-PC has promising functionality for use as a nonthrombogenic, drug eluting coating on metallic vascular stents and grafts.

Complementary effects of nanosilver and superhydrophobic coatings on the prevention of marine bacterial adhesion

A superhydrophobic coating composed of silver nanoparticles enclosed in multilayered polyelectrolyte films was deposited onto copper with the aim of preventing bacterial adhesion. Observations from scanning electron microscopy (SEM) and atomic force microscopy (AFM) showed that the amplified exponential growth of the multilayers could induce distinguishable, hierarchical micro- and nanostructures simultaneously. This growth caused the surface roughness to amplify in a lotus-leaf-like manner. UV/visible spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) confirmed the formation of well-dispersed Ag(0) nanoparticles (with sizes from 4-6 nm) in the films. SEM and fluorescence microscope images of the exposed surfaces revealed that the pattern of adhesion and the density of bacterial cells differed depending on the surface energy and the number of Ag(+) ions released during the various immersion time periods. The complementary effects of nanosilver and superhydrophobic coatings can help to effectively reduce bacterial adhesion and the formation of biofilms.