Radiation-grafting of N-vinylimidazole onto silicone rubber for antimicrobial properties

Antimicrobial Functionalization of Silicone-graft-poly(N-vinylimidazole) Catheters

In this work, we present the modification of a medical-grade silicone catheter with the N-vinylimidazole monomer using the grafting-from method at room temperature and induced by gamma rays. The catheters were modified by varying the monomer concentration (20-100 vol%) and the irradiation dose (20-100 kGy). Unlike the pristine material, the grafted poly(N-vinylimidazole) chains provided the catheter with hydrophilicity and pH response. This change allowed for the functionalization of the catheters to endow it with antimicrobial features. Thus, the quaternization of amines with iodomethane and bromoethane was performed, as well as the immobilization of silver and ampicillin. The inhibitory capacity of these materials, functionalized with antimicrobial agents, was challenged against Escherichia coli and Staphylococcus aureus strains, showing variable results, where loaded ampicillin was amply better at eliminating bacteria.

From rosin to novel bio-based silicone rubber: a review

Rosin is a characteristic natural renewable resource. In view of the unique hydrogenated phenanthrene ring skeleton structure of rosin, it can be designed and synthesized to modify silicone rubber for improving its mechanical properties, thermal stability, and other properties. In this paper, the research progress of silicone rubber modified by rosin and its derivatives is reviewed, including internal or surface modification of room temperature or high temperature vulcanized silicone rubber. The different chemical modifications and polymerization pathways to obtain bio-based silicone rubber (e.g. rosin-based silicone cross-linking agent, filler compound rosin-based silicone cross-linking agent, rosin-based polymer, and rosin quaternary ammonium salt bifunctional antibacterial coating) are discussed and its research prospect is reviewed. Overall, the present review article will provide a quantitative experimental basis for rosin to produce bio-renewable multifunctional silicone rubber to increase our level of understanding of the behavior of this important class of silicone rubber and other similar bio-based polymers.

Natural rubber latex films with effective growth inhibition against S. aureus via surface conjugated gentamicin

Hospital-associated infections and related complications are of extreme concern in the healthcare sector since biofilms generated over material surfaces not only create turbulence in the healthcare practices followed but also ruin the device performance, and increased medication, leading to significant chances of drug resistance. Natural rubber latex (NRL) being the first choice for the manufacture of several conventional biomedical devices, it is essential to ensure the surfaces of the same are inherently inactive against most microorganisms. This study presents NRL film surface conjugated with a well-known antibiotic, gentamicin through an amide linkage to generate antibacterial activity to the surface with a significant growth inhibition rate, especially against Staphylococcus aureus. The NRL films were surface-oxidized under controlled acidic conditions to generate carboxyl groups exploring the unsaturation of the base monomer unit. The carboxyl group reacts with the amine groups of gentamicin facilitating its surface conjugation. The surface anchoring was authenticated by FTIR-ATR complimented further by contact angle measurement as a function of hydrophilicity and elemental analysis by EDX spectroscopy. The antibacterial efficacy of modified NRL films was evaluated using antibacterial drop test and the results indicated a substantial growth inhibition rate (>60%) against Pseudomonas aeruginosa and Staphylococcus aureus. The study could be further optimized and proposed as a viable route for the conjugation of active molecules over inert polymer molecules.

Bibliometrics of Functional Polymeric Biomaterials with Bioactive Properties Prepared by Radiation-Induced Graft Copolymerisation: A Review

Functional polymeric biomaterials (FPBMs) with bioactive characteristics obtained by radiation-induced graft copolymerisation (RIGC) have been subjected to intensive research and developed into many commercial products. Various studies have reported the development of a variety of radiation-grafted FPBMs. However, no reports dealing with the quantitative evaluations of these studies from a global bibliographic perspective have been published. Such bibliographic analysis can provide information to overcome the limitations of the databases and identify the main research trends, together with challenges and future directions. This review aims to provide an unprecedented bibliometric analysis of the published literature on the use of RIGC for the preparation of FPBMs and their applications in medical, biomedical, biotechnological, and health care fields. A total of 235 publications obtained from the Web of Science (WoS) in the period of 1985-2021 were retrieved, screened, and evaluated. The records were used to manifest the contributions to each field and underline not only the top authors, journals, citations, years of publication, and countries but also to highlight the core research topics and the hubs for research excellence on these materials. The obtained data overviews are likely to provide guides to early-career scientists and their research institutions and promote the development of new, timely needed radiation-grafted FPBMs, in addition to extending their applications.

Antimicrobial Properties of a Copper/Silicone Composite Membrane Prepared Using a Two-Step Immersion Process in Iodine and Copper Sulfate Solutions

Silicone (polydimethylsiloxane) materials are widely used in various applications. Due to microbe adherence and biofilm formation at the surface of silicone materials, silicone materials must possess antibacterial properties. To achieve this, we prepared copper (Cu)−silicone composite membranes using a simple two-step process of immersion in iodine and copper sulfate solutions. Subsequent scanning electron microscopy revealed Cu nanoparticles (CuNPs) of 10 to 200 nanometers in diameter on the silicone membrane surface, which were identified as copper iodide using energy-dispersive X-ray spectroscopy. The mechanical strength of the material did not change significantly as a result of the two-step immersion treatment and the Cu/silicone membrane showed excellent antibacterial efficacy against Escherichia coli and Staphylococcus aureus, maintaining R > 2 even after a physical impact such as stomacher treatment. Additionally, the Cu ions eluted from the Cu/silicone membrane remained at very low concentrations, suggesting firm immobilization of CuNPs on the silicone membrane. This proposed antimicrobial treatment method does not require special equipment, can be performed at room temperature, and has the potential for use on silicone materials other than membranes.

Engineered Bioactive Polymeric Surfaces by Radiation Induced Graft Copolymerization: Strategies and Applications

The interest in developing antimicrobial surfaces is currently surging with the rise in global infectious disease events. Radiation-induced graft copolymerization (RIGC) is a powerful technique enabling permanent tunable and desired surface modifications imparting antimicrobial properties to polymer substrates to prevent disease transmission and provide safer biomaterials and healthcare products. This review aims to provide a broader perspective of the progress taking place in strategies for designing various antimicrobial polymeric surfaces using RIGC methods and their applications in medical devices, healthcare, textile, tissue engineering and food packing. Particularly, the use of UV, plasma, electron beam (EB) and γ-rays for biocides covalent immobilization to various polymers surfaces including nonwoven fabrics, films, nanofibers, nanocomposites, catheters, sutures, wound dressing patches and contact lenses is reviewed. The different strategies to enhance the grafted antimicrobial properties are discussed with an emphasis on the emerging approach of in-situ formation of metal nanoparticles (NPs) in radiation grafted substrates. The current applications of the polymers with antimicrobial surfaces are discussed together with their future research directions. It is expected that this review would attract attention of researchers and scientists to realize the merits of RIGC in developing timely, necessary antimicrobial materials to mitigate the fast-growing microbial activities and promote hygienic lifestyles.

Poly(N-vinylcaprolactam) and Salicylic Acid Polymeric Prodrug Grafted onto Medical Silicone to Obtain a Novel Thermo- and pH-Responsive Drug Delivery System for Potential Medical Devices

New medical devices with anti-inflammatory properties are critical to prevent inflammatory processes and infections in medical/surgical procedures. In this work, we present a novel functionalization of silicone for medical use with a polymeric prodrug and a thermosensitive polymer, by graft polymerization (gamma rays), for the localized release of salicylic acid, an analgesic, and anti-inflammatory drug. Silicone rubber (SR) films were functionalized in two stages using graft polymerization from ionizing radiation (⁶⁰Co). The first stage was grafting poly(N-vinylcaprolactam) (PNVCL), a thermo-sensitive polymer, onto SR to obtain SR-g-PNVCL. In the second stage, poly(2-methacryloyloxy-benzoic acid) (P2MBA), a polymeric prodrug, was grafted to obtain (SR-g-PNVCL)-g-P2MBA. The degree of functionalization depended on the concentrations of monomers and the irradiation dose. The films were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM–EDX), thermogravimetric analysis (TGA), and contact angle. An upper critical solution temperature (UCST) of the films was demonstrated by the swelling degree as a temperature function. (SR-g-PNVCL)-g-P2MBA films demonstrated hydrolysis-mediated drug release from the polymeric prodrug, pH, and temperature sensitivity. GC–MS confirmed the presence of the drug (salicylic acid), after polymer hydrolysis. The concentration of the drug in the release media was quantified by HPLC. Cytocompatibility and thermo-/pH sensitivity of functionalized medical silicone were demonstrated in cancer and non-cancer cells.

Review of silicone surface modification techniques and coatings for antibacterial/antimicrobial applications to improve breast implant surfaces

Silicone implants are widely used in the medical field for plastic or reconstructive surgeries for the purpose of soft tissue issues. However, as with any implanted object, healthcare-associated infections are not completely avoidable. The material suffers from a lack of biocompatibility and is often subject to bacterial/microbial infections characterized by biofilm growth. Numerous strategies have been developed to either prevent, reduce, or fight bacterial adhesion by providing an antibacterial property. The present review summarizes the diverse approaches to deal with bacterial infections on silicone surfaces along with the different methods to activate/oxidize the surface before any surface modifications. It includes antibacterial coatings with antibiotics or nanoparticles, covalent attachment of active bacterial molecules like peptides or polymers. Regarding silicone surfaces, the activation step is essential to render the surface reactive for any further modifications using energy sources (plasma, UV, ozone) or chemicals (acid solutions, sol-gel strategies, chemical vapor deposition). Meanwhile, corresponding work on breast silicone prosthesis is discussed. The latter is currently in the line of sight for causing severe capsular contractures. Specifically, to that end, besides chemical modifications, the antibacterial effect can also be achieved by physical surface modifications by adjusting the surface roughness and topography for instance.

Synthesis of a crosslinked poly(ionic liquid) and evaluation of its antimony binding properties

First ever ionic liquid derived sorbent for antimony was synthesised. The charged functional groups of the polymer showed preferential binding and strong affinity for difficult to remove anionic species of antimony. The sorbent was synthesised by crosslinking co-polymerisation of 1-butyl-3-vinylimidazolium bromide with N,N-methylenebis(acrylamide). SEM-EDS analysis showed that the polymer retained the bromide counter ions. Antimony removal properties under wide solution conditions, including the presence of competitor ions, were investigated. Maximum antimony binding and selectivity was at pH 3.0. Variation in saturation capacity with respect to the crosslinker amount matched with the calculated capacity values. Maximum uptake obtained was 4.6 and 3.2 mmol/g for Sb(III) and Sb(V) respectively. Tartrate salt of Sb(III) showed better binding through the interaction of tartrate with the imidazole moieties of the polymer. In less than 15 min, saturation capacity was achieved for Sb(III), while over 90% of uptake was complete for Sb(V). Investigations on sorption mechanism, which included synthesis and comparative evaluation of the non-ionic counterpart polyvinylimidazole as sorbent, indicated the uptake to be through anion exchange. Sb(III) specific binding against Sb(V) was seen in the presence of nitrilotriacetic acid.

Antibacterial Coatings for Improving the Performance of Biomaterials

Biomedical devices have become essential in the health care. Every day, an enormous number of these devices are used or implanted in humans. In this context, the bacterial contamination that could be developed in implanted devices is critical since it is estimated that infections kill more people than other medical causes. Commonly, these infections are treated with antibiotics, but the biofilm formation on implant surfaces could significantly reduce the effectiveness of these antibiotics since bacteria inside the biofilm is protected from the drug. In some cases, a complete removal of the implant is necessary in order to overcome the infection. In this context, antibacterial coatings are considered an excellent strategy to avoid biofilm formation and, therefore, mitigate the derived complications. In this review, the main biomaterials used in biomedical devices, the mechanism of biofilm formation, and the main strategies for the development of antibacterial coatings, are reviewed. Finally, the main polymer-based strategies to develop antibacterial coatings are summarized, with the aim of these coatings being to avoid the bacteria proliferation by controlling the antibacterial mechanisms involved and enhancing long-term stability.

Reduced fibrous capsule formation at nano-engineered silicone surfaces via tantalum ion implantation

Nano-engineered surface of silicone implant improves the biocompatibility and suppresses the fibrous capsule formation which is the most common side effect of polymeric implants.

Recent Advances in Antimicrobial Polymers: A Mini-Review

Human safety and well-being is threatened by microbes causing numerous infectious diseases resulting in a large number of deaths every year. Despite substantial progress in antimicrobial drugs, many infectious diseases remain difficult to treat. Antimicrobial polymers offer a promising antimicrobial strategy for fighting pathogens and have received considerable attention in both academic and industrial research. This mini-review presents the advances made in antimicrobial polymers since 2013. Antimicrobial mechanisms exhibiting either passive or active action and polymer material types containing bound or leaching antimicrobials are introduced. This article also addresses the applications of these antimicrobial polymers in the medical, food, and textile industries.

Synthesis and characterization of stimuli-responsive polypropylene containing N-vinylcaprolactam and N-vinylimidazole obtained by ionizing radiation

Polypropylene films were grafted with thermo-responsive N-vinylcaprolactam and pH-responsive N-vinylimidazole polymers by means of gamma radiation using pre-irradiation and direct methods, in order to functionalize the films with thermo- and/or pH-responsiveness. The dependence of grafting yield on parameters such as co-monomer concentration, pre-irradiation dose, temperature, and reaction time was evaluated. The samples were characterized by Fourier transform infrared and X-ray photoelectron spectroscopies, differential scanning calorimetry, thermogravimetric analysis, swelling studies in different solvents, and water contact angle. The grafted copolymers presented thermo- and pH-sensitiveness, highlighting their potential as advanced biomaterials, capable of providing adequate environment for hosting and sustained release of antimicrobial drugs bearing cationic moieties, such as groups of diclofenac, while still exhibiting good cytocompatibility.