Enhanced antibacterial and corrosion resistance properties of Ag substituted hydroxyapatite/functionalized multiwall carbon nanotube nanocomposite coating on 316L stainless steel for biomedical application

Preparation of Ag@3D-TiO2 Scaffolds and Determination of its Antimicrobial Properties and Osteogenesis-promoting Ability

OBJECTIVES

The micro-nano structure of 3D-printed porous titanium (Ti) alloy with excellent performance in avoiding stress shielding and promoting bone tissue differentiation provides a new opportunity for the development of bone implants, but it necessitates higher requirements for bone tissue differentiation and the antibacterial properties of bone implants in clinical practice.

METHODS

This study investigated the preparation, antimicrobial properties, and osteogenesis-promoting ability of the 3D printed porous Ti alloy anodic oxidized Ag-carrying (Ag@3D-TiO2) scaffolds. The 3D printed porous Ti alloy (3D-Ti), anodized 3D printed porous Ti alloy (3D-TiO2), and Ag@3D-TiO2 scaffolds were synthesized using electron beam melting. The antimicrobial properties of the scaffolds were examined using antibacterial tests and their cytocompatibility was assessed using a cell proliferation assay and acridine orange/ethidium bromide (AO/EB) staining. In vitro cellular assays were used to investigate the effects of the scaffold microstructural features on cell activity, proliferation, and osteogenesis-related genes and proteins. In vivo animal experiments were used to evaluate the anti-inflammatory and osteogenesis-promoting abilities of the scaffolds.

RESULTS

The Ag@3D-TiO2 scaffolds exhibited sustained anti-microbial activity over time, enhanced cell proliferation, facilitated osteogenic differentiation, and increased extracellular matrix mineralization. In addition, alkaline phosphatase (ALP), collagen type I (COL-I), and osteocalcin (OCN)-related genes and proteins were upregulated. In vivo animal implantation experiments, the anti-inflammatory effect of the Ag@3D-TiO2 scaffolds were observed using histology, and a large amount of fibrous connective tissue was present around it; the Ag@3D-TiO2 scaffolds were more bio-compatible with the surrounding tissues compared with 3D-Ti and 3D-TiO2; a large amount of uniformly distributed neoplastic bone tissue existed in their pores, and the chronic systemic toxicity test showed that the 3D-Ti, 3D-TiO2, and Ag@3D-TiO2 scaffolds are biologically safe.

CONCLUSION

The goal of this study was to create a scaffold that exhibits antimicrobial properties and can aid bone growth, making it highly suitable for use in bone tissue engineering.

Silver-Containing Biomaterials for Biomedical Hard Tissue Implants

Bacterial infection caused by biomaterials is a very serious problem in the clinical treatment of implants. The emergence of antibiotic resistance has prompted other antibacterial agents to replace traditional antibiotics. Silver is rapidly developing as an antibacterial candidate material to inhibit bone infections due to its significant advantages such as high antibacterial timeliness, high antibacterial efficiency, and less susceptibility to bacterial resistance. However, silver has strong cytotoxicity, which can cause inflammatory reactions and oxidative stress, thereby destroying tissue regeneration, making the application of silver-containing biomaterials extremely challenging. In this paper, the application of silver in biomaterials is reviewed, focusing on the following three issues: 1) how to ensure the excellent antibacterial properties of silver, and not easy to cause bacterial resistance; 2) how to choose the appropriate method to combine silver with biomaterials; 3) how to make silver-containing biomaterials in hard tissue implants have further research. Following a brief introduction, the discussion focuses on the application of silver-containing biomaterials, with an emphasis on the effects of silver on the physicochemical properties, structural properties, and biological properties of biomaterials. Finally, the review concludes with the authors' perspectives on the challenges and future directions of silver in commercialization and in-depth research.

Nanotube breakthroughs: unveiling the potential of carbon nanotubes as a dual therapeutic arsenal for Alzheimer's disease and brain tumors

Alzheimer's disease (AD) and brain tumors are debilitating neurological conditions that pose significant challenges in current medical practices. Existing treatment options for AD primarily focus on symptom management, and brain tumors often require aggressive therapeutic approaches. Novel disease-modifying strategies and therapeutic agents are urgently needed to address the underlying causes of AD pathogenesis and improve brain tumor management. In recent years, nanoparticles (NPs) have shown promise as valuable tools in diagnosing and managing various brain disorders, including AD. Among these, carbon nanotubes (CNTs) have garnered attention for their unique properties and biomedical potential. Their ability to cross the blood-brain barrier (BBB) with ease opens up new possibilities for targeted drug delivery and neuroprotection. This literature review aims to explore the versatile nature of CNTs, which can be functionalized with various biomolecules or substances due to their sp2 hybridization. This adaptability enables them to specifically target cells and deliver medications under specific environmental conditions. Moreover, CNTs possess an exceptional capacity to penetrate cell membranes, making them valuable tools in the treatment of AD and brain tumors. By delving into the role of CNTs in biomedicine, this review sheds light on their potential in managing AD, offering a glimpse of hope for effective disease-modifying options. Understanding the mechanisms of CNTs' action and their capabilities in targeting and delivering medication to affected cells will pave the way for innovative therapeutic strategies that can improve the lives of those afflicted with these devastating neurological conditions. The exploration of CNTs as a dual therapeutic arsenal for both brain tumors and Alzheimer's disease holds great promise and may usher in a new era of effective treatment strategies for these challenging conditions.

Graphene oxide reinforced chitosan/polyvinyl alcohol antibacterial coatings on stainless steel surfaces exhibit superior bioactivity without human cell cytotoxicity

The study proposes an alternative therapeutics to diminish bacterial attachment in biomedical implants by modifying their surface with passive coatings. A uniform, thin-film of chitosan/polyvinyl alcohol/graphene oxide (CS/PVA/GO) was coated on 316 L stainless steel (SS) surface through spread casting followed by solvent evaporation. The abundant anchoring sites available at macromolecular interfaces of chitosan/PVA matrix facilitated a smooth, dense loading of GO. The effect of GO content on physicochemical features, antibacterial potential, and biocompatibility of coatings was thoroughly studied. The hybrid films displayed good adhesion behavior, and UV-protection ability with desired mechanical and thermal stability when coated on SS surface. Coatings manifested a 1.5-1.7 fold rise in antibacterial efficacy against Staphylococcus epidermidis and Staphylococcus aureus and exhibited a permanent biocidal response after 6 h of contact-active behaviour. We investigated a 3-fold generation of reactive oxygen species as the predominant antibacterial mechanism, which diminishes bacterial integrity by inducing protein leakage (8.5-9 fold higher) and suppressing respiratory chain activity as two secondary mechanisms. All coatings with varying GO content appeared non-haemolytic (<2%) with ultra-low cytotoxicity (<29.08%) against human hepatocellular carcinoma (HepG2) and peripheral blood mononuclear cells. The degradation rate of coatings in simulated body fluid exhibited a higher stability, indicated by a lower weight loss (69-78%) and a decrease in pH values as the GO content in coatings increased from 0.05 to 0.15 wt%. Such anti-infective coating is a step forward in inhibiting bacterial colonization on SS surfaces to extend its lifespan.

Nanoantibiotic effect of carbon-based nanocomposites: epicentric on graphene, carbon nanotubes and fullerene composites: a review

Carbon in many different forms especially, Graphene, Carbon nanotubes (CNTs), and Fullerene is emerging as an important material in the areas of the biomedical field for various applications. This review comprehensively describes the nano antibiotic effect of carbon-based nanocomposites: epicenter on graphene, carbon nanotubes, and fullerene Composites. It summarises the studies conducted to evaluate their antimicrobial applications as they can disrupt the cell membrane of bacteria resulting in cell death. The initial section gives a glimpse of both "Gram"-positive and negative bacteria, which have been affected by Graphene, CNTs, and Fullerene-based nanocomposites. These bacteria include Staphylococcus Aureus, Bacillus Thuringiensis, Enterococcus faecalis, Enterococcus faecium, Bacillus subtilis, Escherichia coli, Klebseilla pneumoniae, Pseudomonas aeroginosa, Pseudomonas syringae , Shigella flexneri,Candida Albicans, Mucor. Another section is dedicated to the insight of Graphene, and its types such as Graphene Oxide (GO), Reduced graphene oxide (rGO), Graphene Nanoplatelets (GNPs), Graphene Nanoribbons (GNRs), and Graphene Quantum Dots (GQDs). Insight into CNT, including both the types SWCNT and MWCNT, studied, followed by understanding fullerene is also reported. Another section is dedicated to the antibacterial mechanism of Graphene, CNT, and Fullerene-based nanocomposites. Further, an additional section is dedicated to a comprehensive review of the antibacterial characteristics of Graphene, CNT, and nanocomposites based on fullerene. Future perspectives and recommendations have also been highlighted in the last section.

Ion-Doped Calcium Phosphate-Based Coatings with Antibacterial Properties

Ion-substituted calcium phosphate (CP) coatings have been extensively studied as promising materials for biomedical implants due to their ability to enhance biocompatibility, osteoconductivity, and bone formation. This systematic review aims to provide a comprehensive analysis of the current state of the art in ion-doped CP-based coatings for orthopaedic and dental implant applications. Specifically, this review evaluates the effects of ion addition on the physicochemical, mechanical, and biological properties of CP coatings. The review also identifies the contribution and additional effects (in a separate or a synergistic way) of different components used together with ion-doped CP for advanced composite coatings. In the final part, the effects of antibacterial coatings on specific bacteria strains are reported. The present review could be of interest to researchers, clinicians, and industry professionals involved in the development and application of CP coatings for orthopaedic and dental implants.

Green Synthesis of Antibacterial Nanocomposite of Silver Nanoparticle-Doped Hydroxyapatite Utilizing Curcuma longa Leaf Extract and Land Snail (Achatina fulica) Shell Waste

Preparation of green synthesized silver nanoparticle (AgNPs)-doped hydroxyapatite (Ag/HA) utilizing Curcuma longa leaf extract and land snail (Achatina fulica) shell waste was performed. Physicochemical characteristics and antibacterial activity of Ag/HA composite as a function of Ag content was studied. Instrumental analysis such as XRD, SEM-EDX, TEM, and XPS were employed to characterize the nanocomposites. The physicochemical study revealed the maintained porous structure of HA after Ag immobilization, and from TEM analyses, it was found that the distributed spherical particles are associated with the dispersed Ag and have a particle diameter of around 5-25 nm. Antibacterial activity of the nanocomposite was evaluated against Escherichia coli, Staphylococcus aureus, Kliebsiella, pneumonia, and Streptococcus pyogenes. The results showed that the varied Ag content (1.0; 1.6; and 2.4% wt) influenced the nanoparticle distribution in the nanocomposite and enhanced the antibacterial feature.

Synergetic effect of Sn doped ZnO nanoparticles synthesized via ultrasonication technique and its photocatalytic and antibacterial activity

The current work reports the photocatalytic and antibacterial performance of tin (Sn) doped zinc oxide (ZnO) nanoparticles synthesized via ultrasonic aided co-precipitation technique. The increase of Sn concentration decreased the lattice parameter and increased the crystallite size without changing the ZnO structure. The hexagonal shaped particles and sheets obtained for 3% and 5% Sn substituted ZnO, respectively. The increase of dopant concentration reduced the reflectance and optical band gap energy of Sn doped ZnO. The vibrational band present at 1443 cm^-1 confirmed the successful bond formation of Sn-O-Zn. The 5% Sn doped ZnO nanoparticles exhibited greater dye elimination rate of methylene blue compared to 3% Sn. The antibacterial activity of Sn doped ZnO showed the higher zone of inhibition about 14 mm against different pathogens. The 5% Sn doped ZnO photocatalyst improve the transfer rate of photo excite carrier and decrease the rate of recombination which greatly influence on the photocatalytic and antibacterial performance.

Hybrid Materials Based on Multi-Walled Carbon Nanotubes and Nanoparticles with Antimicrobial Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were decorated with different types of nanoparticles (NPs) in order to obtain hybrid materials with improved antimicrobial activity. Structural and morphological analysis, such as Fourier transformed infrared spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, environmental scanning electron microscopy/energy-dispersive X-ray spectroscopy and the Brunauer-Emmett-Teller technique were used in order to investigate the decoration of the nanotubes with NPs. Analysis of the decorated nanotubes showed a narrow size distribution of NPs, 7-13 nm for the nanotubes decorated with zinc oxide (ZnO) NPs, 15-33 nm for the nanotubes decorated with silver (Ag) NPs and 20-35 nm for the nanotubes decorated with hydroxyapatite (HAp) NPs, respectively. The dispersion in water of the obtained nanomaterials was improved for all the decorated MWCNTs, as revealed by the relative absorbance variation in time of the water-dispersed nanomaterials. The obtained nanomaterials showed a good antimicrobial activity; however, the presence of the NPs on the surface of MWCNTs improved the nanocomposites' activity. The presence of ZnO and Ag nanoparticles enhanced the antimicrobial properties of the material, in clinically relevant microbial strains. Our data proves that such composite nanomaterials are efficient antimicrobial agents, suitable for the therapy of severe infection and biofilms.

Ultrasound-irradiated synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite derived from fish-scale residues followed by ultrasound-assisted organic dyes removal

We report a novel method for the synthesis of 3-mercaptopropyl trimethoxysilane-modified hydroxyapatite (FHAP-SH) derived from fish-scale residues by using ultrasound irradiation. Scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used for the FHAP-SH characterization. Then, the organic dye adsorption on the FHAP-SH was monitored through an ultrasound process. After the dye removal optimization, significant improvements were observed in the maximum adsorption capacities for Congo Red (CR, 500 mg g^-1), Coomassie Brilliant Blue G 250 (CB, 235 mg g^-1), and Malachite Green (MG, 625 mg g^-1). The adsorption behaviors of these dyes were fitted by using the Langmuir isotherm model with a high coefficient of determination values ranging from 0.9985 to 0.9969. The adsorption of the three dyes onto FHAP-SH was an endothermic process based on the adsorption thermodynamics model, while the adsorption kinetics analysis of the dyes presented a good alignment with the pseudo-second-order kinetics. The FHAP-SH exhibits a remarkably high adsorption capacity, is inexpensive, and fulfills the ecofriendly requirements of dye wastewater treatment, especially in the textile industry.

Nanocomposites for Enhanced Osseointegration of Dental and Orthopedic Implants Revisited: Surface Functionalization by Carbon Nanomaterial Coatings

Over the past few decades, carbon nanomaterials, including carbon nanofibers, nanocrystalline diamonds, fullerenes, carbon nanotubes, carbon nanodots, and graphene and its derivatives, have gained the attention of bioengineers and medical researchers as they possess extraordinary physicochemical, mechanical, thermal, and electrical properties. Recently, surface functionalization with carbon nanomaterials in dental and orthopedic implants has emerged as a novel strategy for reinforcement and as a bioactive cue due to their potential for osseointegration. Numerous developments in fabrication and biological studies of carbon nanostructures have provided various novel opportunities to expand their application to hard tissue regeneration and restoration. In this minireview, the recent research trends in surface functionalization of orthopedic and dental implants with coating carbon nanomaterials are summarized. In addition, some seminal methodologies for physicomechanical and electrochemical coatings are discussed. In conclusion, it is shown that further development of surface functionalization with carbon nanomaterials may provide innovative results with clinical potential for improved osseointegration after implantation.

Investigation on hydrogen bonds and conformational changes in protein/polysaccharide/ceramic based tri-component system

The main attention of present work is to study the molecular level interactions in the interface of biocomposite to increase their applicability. A specific kind of molecular interaction namely, hydrogen bonds play a vital role in deciding composite property. In this study, we construct a tri-component system based on silk fibroin/sodium alginate/hydroxyapatite by varying protein and polysaccharide proportions using in-situ co-precipitation method. The Fourier Transfer Infrared (FTIR) prediction state that prepared composite exhibit inter-(OH⋯N, OH⋯O, OH⋯π) and intra-(OH⋯OH) molecular hydrogen bonds and their strength are varied in accordance with composition of composite. During composite preparation, conformational changes from the random coil to β-sheet structure through intermediate β-turns exist within the protein molecule that is confirmed by vibrational spectra. The crystallographic profile and morphology of HAP were greatly influenced by virtue of polymer matrix. Simulated body fluid (SBF) immersion study shows that biodegradation and swelling ratio are correlated with type of hydrogen bond and secondary structure of protein. Moreover, the in-vitro biomineralization, cytotoxicity and antibacterial activity of composite were analysed in detail.

Morphological, Chemical, and Biological Investigation of Ionic Substituted, Pulse Current Deposited Calcium Phosphate Coatings

Ionic substituted calcium phosphate coatings (iCP) have been prepared by the electrochemical pulse current deposition technique with an alternate pulse on and off time of 5 ms onto a titanium alloy substrate. The elemental distribution and morphology of the deposited layers have been extensively studied by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The crystallinity and phase structure of iCPs have been investigated by X-ray diffraction (XRD). The corrosion characteristics and biodegradability of coatings have been determined by electrochemical measurements, recording potentiodynamic curves in a physiological solution over a long-term immersion period. The cell viability tests confirmed that the iCP coating was biocompatible, while the corrosion tests proved its biodegradable characteristic. In our paper, we compare the morphological, chemical, and biological characteristics of silver and zinc substituted calcium phosphate layers deposited by the electrochemical method.

Antibacterial properties of Ag/TiO2/PDA nanofilm on anodized 316L stainless steel substrate under illumination by a normal flashlight

The demand of medical materials for rapid and efficient elimination of bacteria has seen a dramatic surge over the past few years. In this study, antibacterial nanofilms with reactive oxygen species were generated by photocatalysis. To prepare these nanofilms, Ag and amorphous TiO₂ nanoparticles decorated on polydopamine (PDA) were coated on three-dimensional (3D) nanopore arrays, which was fabricated on a substrate of anodized stainless steel. All the antibacterial tests were conducted with a household flashlight, which may be considered as a practical approach for antibacterial materials. The photoelectrochemical property of the 3D Ag/TiO₂/PDA nanofilm on 316L stainless steel (Ag/TiO₂/PDA SS) was about 15 times higher than that of the annealed Ag/TiO₂/PDA SS, and consequently, it exhibited higher antibacterial activity. The enhanced photoelectrochemical property is attributed to the successful separation of electrons (amorphous TiO₂) and holes (Ag nanoparticles). Further, when a plate containing 3D Ag/TiO₂/PDA SS was irradiated with visible light just for 10 min, it immediately destroyed the bacteria in 10⁶ CFU/mL without any bacterial colony. After five weeks, there were still no bacterial colonies in the plate corresponding to Ag/TiO₂/PDA SS under visible light, while Ag/TiO₂/PDA SS in dark had a negligible effect on the bacteria, i.e., the antibacterial mechanism through direct contact and ion dissolution was not efficient. The excellent antibacterial properties of 3D Ag/TiO₂/PDA SS illuminated by flashlight provides an efficient, facile, and cost-effective technique for the development of antibacterial medical materials to meet the increasing demand of eliminating bacterial infections.

Tissue Engineering and Regenerative Medicine: Achievements, Future, and Sustainability in Asia

Exploring innovative solutions to improve the healthcare of the aging and diseased population continues to be a global challenge. Among a number of strategies toward this goal, tissue engineering and regenerative medicine (TERM) has gradually evolved into a promising approach to meet future needs of patients. TERM has recently received increasing attention in Asia, as evidenced by the markedly increased number of researchers, publications, clinical trials, and translational products. This review aims to give a brief overview of TERM development in Asia over the last decade by highlighting some of the important advances in this field and featuring major achievements of representative research groups. The development of novel biomaterials and enabling technologies, identification of new cell sources, and applications of TERM in various tissues are briefly introduced. Finally, the achievement of TERM in Asia, including important publications, representative discoveries, clinical trials, and examples of commercial products will be introduced. Discussion on current limitations and future directions in this hot topic will also be provided.