Graphene oxide immobilized surfaces facilitate the sustained release of doxycycline for the prevention of implant related infection

Graphene-Based Composites for Biomedical Applications: Surface Modification for Enhanced Antimicrobial Activity and Biocompatibility

The application of graphene-based materials in medicine has led to significant technological breakthroughs. The remarkable properties of these carbon materials and their potential for functionalization with various molecules and compounds make them highly attractive for numerous medical applications. To enhance their functionality and applicability, extensive research has been conducted on surface modification of graphene (GN) and its derivatives, including modifications with antimicrobials, metals, polymers, and natural compounds. This review aims to discuss recent and relevant studies related to advancements in the formulation of graphene composites, addressing their antimicrobial and/or antibiofilm properties and evaluating their biocompatibility, with a primary focus on their biomedical applications. It was concluded that GN surface modification, particularly with compounds intrinsically active against bacteria (e.g., antimicrobial peptides, silver and copper nanomaterials, and chitosan), has resulted in biomaterials with improved antimicrobial performance. Furthermore, the association of GN materials with non-natural polymers provides composites with increased biocompatibility when interfaced with human tissues, although with slightly lower antimicrobial efficacy. However, it is crucial to highlight that while modified GN materials hold huge potential, their widespread use in the medical field is still undergoing research and development. Comprehensive studies on safety, long-term effects, and stability are essential before their adoption in real-world medical scenarios.

Multifunctional antibacterial chitosan-based hydrogel coatings on Ti6Al4V biomaterial for biomedical implant applications

Among biomedical community, great efforts have been realized to develop antibacterial coatings that avoid implant-associated infections. To date, conventional mono-functional antibacterial strategies have not been effective enough for successful long-term implantations. Consequently, researchers have recently focused their attention on novel bifunctional or multifunctional antibacterial coatings, in which two or more antibacterial mechanisms interact synergistically. Thus, in this work different chitosan-based (CHI) hydrogel coatings were created on Ti6Al4V surface using genipin (Ti-CHIGP) and polyethylene glycol (Ti-CHIPEG) crosslinking agents. Hydrogel coatings demonstrated an exceptional in vivo biocompatibility plus a remarkable ability to promote cell proliferation and differentiation. Lastly, hydrogel coatings demonstrated an outstanding bacteria-repelling (17-28 % of S. aureus and 33-43 % of E. coli repelled) and contact killing (186-222 % of S. aureus and 72-83 % of E. coli damaged) ability. Such bifunctional antibacterial activity could be further improved by the controlled release of drugs resulting in powerful multifunctional antibacterial coatings.

Graphene and its derivatives: "one stone, three birds" strategy for orthopedic implant-associated infections

Orthopedic implants provide an avascular surface for microbial attachment and biofilm formation, impeding the entry of immune cells and the diffusion of antibiotics. The above is an important cause of dental and orthopedic implant-associated infection (IAI). For the prevention and treatment of IAI, the drawbacks of antibiotic resistance and surgical treatment are increasingly apparent. Due to their outstanding biological properties such as biocompatibility, immunomodulatory effects, and antibacterial properties, graphene-based nanomaterials (GBNs) have been applied to bone tissue engineering to deal with IAI, and in particular have great potential application in drug/gene carriers, multi-functional platforms, and coating forms. Here we review the latest research progress and achievements in GBNs for the prevention and treatment of IAI, mainly including their biomedical applications for antibacterial and immunomodulation effects, and for inducing osteogenesis. Furthermore, the biosafety of graphene family materials in bone tissue regeneration and the feasibility of clinical application are critically analyzed and discussed.

The design, construction and application of graphene family composite nanocoating on dental metal surface

Enhancement of the biological and mechanical properties of dental metals is important for accommodation with therapeutic schemes in different stomatological disciplines. Nanocoatings based on graphene family nanomaterials (GFNs) improve the topological structure and physicochemical properties of metal surfaces, endowing them with new properties while maintaining inherent mechanical properties. Nano-composite coatings, composed of GFNs with one or more type of polymer, metal, oxide, and inorganic nonmetallic compound, offer more matching modification schemes to meet multifunctional oral treatment requirements (e.g., anti-bacterial and anti-corrosive activity, osteogenesis and angiogenesis). This review describes recent progress in the development of GFN composite nanocoatings for the modification of dental metals, focus on biological effects in clinical settings. Underlying molecular mechanisms, critical modification schemes, and technical innovation in preparation methods are also discussed. The key parameters of GFN composite nanocoating surface modification are summarized according to effects on cellular responses and antibacterial activity. This review provides a theoretical reference for the optimization of the biological effects and application of GFN composite nanocoatings for dental metals, and the promotion of the environmentally friendly large-scale production of high-quality multifunctional GFN-based nanocoatings in the field of oral science.

Graphene Oxide Thin Films with Drug Delivery Function

Graphene oxide has been used in different fields of nanomedicine as a manager of drug delivery due to its inherent physical and chemical properties that allow its use in thin films with biomedical applications. Several studies demonstrated its efficacy in the control of the amount and the timely delivery of drugs when it is incorporated in multilayer films. It has been demonstrated that oxide graphene layers are able to work as drug delivery or just to delay consecutive drug dosage, allowing the operation of time-controlled systems. This review presents the latest research developments of biomedical applications using graphene oxide as the main component of a drug delivery system, with focus on the production and characterization of films, in vitro and in vivo assays, main applications of graphene oxide biomedical devices, and its biocompatibility properties.

Preparation of Titanium Oxide-Based Nanoparticles Modified with D-(+)-Mannose and Investigation of their Properties As A Potential Drug Carrier

Titanium oxide nanoparticles modified with D-(+)-mannose were obtained. In the process of their formation, they were conjugated with an active substance (tadalafil). The physicochemical properties of the obtained products were assessed, and the size and electrokinetic potential were determined using a dynamic light scattering technique. X-ray diffractometry was applied in order to define the crystalline properties, and Fourier-transform infrared spectroscopy was used to confirm the formation of the desired products. It was possible to obtain TiO2 coated with D-(+)-mannose. The average size of nanoparticles was between 230 and 268 nm. The release of the active substance from the product over a time period of three hours was assessed against the reference material, which was not modified by D-(+)-mannose. The results indicate that covering titanium oxide nanoparticles with the modifying substance favours a slower rate of release for the active substance, which is the desired effect from a pharmacological point of view. The releasing of active substance from modified products was even 68% slower than that from the reference product. These modified titanium oxides are promising materials that may have found an application as drug carriers.

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Simultaneous Grafting Polymerization of Acrylic Acid and Silver Aggregates Formation by Direct Reduction Using γ Radiation onto Silicone Surface and Their Antimicrobial Activity and Biocompatibility

The modification of medical devices is an area that has attracted a lot of attention in recent years; particularly, those developments which search to modify existing devices to render them antimicrobial. Most of these modifications involve at least two stages (modification of the base material with a polymer graft and immobilization of an antimicrobial agent) which are both time-consuming and complicate synthetic procedures; therefore, as an improvement, this project sought to produce antimicrobial silicone (PDMS) in a single step. Using gamma radiation as both an energy source for polymerization initiation and as a source of reducing agents in solution, PDMS was simultaneously grafted with acrylic acid and ethylene glycol dimethacrylate (AAc:EGDMA) while producing antimicrobial silver nanoparticles (AgNPs) onto the surface of the material. To obtain reproducible materials, experimental variables such as the effect of the dose, the intensity of radiation, and the concentration of the silver salt were evaluated, finding the optimal reaction conditions to obtain materials with valuable properties. The characterization of the material was performed using electronic microscopy and spectroscopic techniques such as 13C-CPMAS-SS-NMR and FTIR. Finally, these materials demonstrated good antimicrobial activity against S. aureus while retaining good cell viabilities (above 90%) for fibroblasts BALB/3T3.

A functional coating to enhance antibacterial and bioactivity properties of titanium implants and its performance in vitro

Bacterial infections and lack of osseointegration may negatively affect the success of titanium (Ti) implants. In the present study, a functional coating composed of chitosan (CS) microspheres and nano hydroxyapatite (nHA) was prepared to obtain antimicrobial Ti implants with enhanced bioactivity. First, the chitosan microspheres were fixed to Ti surfaces activated by alkali and heat treatment, then nHA coatings were precipitated onto these surfaces. Ciprofloxacin was loaded into the microspheres using two different procedures; encapsulation and diffusion. Scanning electron microscopy micrographs of the modified Ti surfaces showed that the coating was successfully deposited onto the Ti surfaces and stable for 30 days in PBS. The drug was completely released from free microspheres loaded by encapsulation in 21 days whereas only 89% release was observed after immobilization. The burst release also decreased from ca. 55% to ca. 35%. The release was further reduced following the nHA precipitation. The modified Ti surfaces showed antimicrobial activity based on the bacterial time-kill assay using S. aureus, but the efficiency was affected by both nHA precipitation and drug loading strategy. Highest antimicrobial activity was seen in the samples without nHA layer, and when the drug was loaded by diffusion. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed that nHA on the surface enhanced HA growth in simulated body fluid for 3 weeks, showing increased osseointegration potential. Therefore, the proposed coating may be used to prevent Ti implant failure originated from bacterial infection and/or low bioactivity.

Biofilm Formation and Expression of Virulence Genes of Microorganisms Grown in Contact with a New Bioactive Glass

Bioactive glass F18 (BGF18), a glass containing SiO2-Na2O-K2O-MgO-CaO-P2O5, is highly effective as an osseointegration buster agent when applied as a coating in titanium implants. Biocompatibility tests using this biomaterial exhibited positive results; however, its antimicrobial activity is still under investigation. In this study we evaluated biofilm formation and expression of virulence-factor-related genes in Candida albicans, Staphylococcus epidermidis, and Pseudomonas aeruginosa grown on surfaces of titanium and titanium coated with BGF18. C. albicans, S. epidermidis, and P. aeruginosa biofilms were grown on specimens for 8, 24, and 48 h. After each interval, the pH was measured and the colony-forming units were counted for the biofilm recovery rates. In parallel, quantitative real-time polymerase chain reactions were carried out to verify the expression of virulence-factor-related genes. Our results showed that pH changes of the culture in contact with the bioactive glass were merely observed. Reduction in biofilm formation was not observed at any of the studied time. However, changes in the expression level of genes related to virulence factors were observed after 8 and 48 h of culture in BGF18. BGF18 coating did not have a clear inhibitory effect on biofilm growth but promoted the modulation of virulence factors.

Polylactic Acid-Graphene Oxide-based Materials for Loading and Sustained Release of Poorly Soluble Pesticides

A pesticide carrier system can offer advantages to active components, such as improving shelf life, extending the lasting period, and reducing toxicity, all of which could reduce the adverse effects of pesticides on the environment. Graphene oxide (GO) is a promising medical drug carrier material, and its research in the field of pesticides is still in the exploration stage. Herein, in order to load water-insoluble pesticides, a series of polylactic acid-graphene oxides (PLA-GOs) were produced incorporating small amounts (0.1-1 wt %) of GO using acetone-chloroform and N,N-dimethylformamide-dichloromethane, two dual-solvent systems. The prepared PLA-GO carrier materials were characterized by FT-IR, Raman spectroscopy, and differential scanning calorimetry analysis, and their effects on rice growth within 20 days were also evaluated. When the amount of GO added was 0.5% and the solvent system was acetone-chloroform, the amount of pyraclostrobin (Pyr) loaded on PLA-GO (A-0.5%) was very high (39.89%). The PLA-GO pesticide microsphere showed a significantly sustained release of Pyr (up to 30 d). Furthermore, the indoor bioassay results showed that the PLA-GO pesticide microsphere (EC₅₀ = 1.2682) had the best fungicidal activity against Rhizoctonia solani, followed by Pyr technical (EC₅₀ = 2.3137) and commercial Pyr microcapsule suspension (EC₅₀ = 3.4570). In conclusion, it was found that PLA-GOs prepared using the acetone-chloroform system were more suitable as a pesticide carrier, which provided a preliminary basis for GO to realize the coating of water-insoluble pesticides.

Graphenic Materials for Biomedical Applications

Graphene-based nanomaterials have been intensively studied for their properties, modifications, and application potential. Biomedical applications are one of the main directions of research in this field. This review summarizes the research results which were obtained in the last two years (2017-2019), especially those related to drug/gene/protein delivery systems and materials with antimicrobial properties. Due to the large number of studies in the area of carbon nanomaterials, attention here is focused only on 2D structures, i.e. graphene, graphene oxide, and reduced graphene oxide.