Selenium nanoparticles incorporated into titania nanotubes inhibit bacterial growth and macrophage proliferation

Antimicrobial Effects of Metal Coatings or Physical, Chemical Modifications of Titanium Dental Implant Surfaces for Prevention of Peri-Implantitis: A Systematic Review of In Vivo Studies

Introduction: Peri-implantitis poses a significant challenge for implant dentistry due to its association with bacterial colonization on implant surfaces and the complexity of its management. This systematic review aims to assess evidence from in vivo studies regarding the antimicrobial efficacy of titanium (Ti) dental implant surfaces following physical/chemical modifications or the application of various metal element coatings in preventing bacterial growth associated with peri-implantitis. Materials and Methods: A literature review was conducted across four scientific databases (PubMed, Embase, Scopus, Web of Science), encompassing in vivo studies published between 2013 and 2024, and 18 reports were included in the systematic review. Results: The findings suggest that titanium dental implant surfaces, following physical/chemical modifications and metal element coatings, exhibit antimicrobial effects against bacteria associated with peri-implantitis in humans and various animal models. Conclusions: The reviewed studies indicated a reduction in bacterial colonization, diminished biofilm formation, and decreased signs of inflammation in the peri-implant tissues, which provides evidence that physical/chemical alterations on titanium dental implant surfaces or metal element coatings, like silver (Ag), zinc (Zn), magnesium (Mg), and copper (Cu), demonstrate antimicrobial properties in in vivo studies. However, caution is warranted when translating findings to clinical practice due to methodological disparities and high bias risks. Further larger-scale clinical trials are imperative to assess their long-term efficacy and validate their clinical applicability.

TiO2 nanotubes as an antibacterial nanotextured surface for dental implants: Systematic review and meta-analysis

OBJECTIVES

Nanotechnology is constantly advancing in dental science, progressing several features aimed at improving dental implants. An alternative for surface treatment of dental implants is electrochemical anodization, which may generate a nanotubular surface (TiO2 nanotubes) with antibacterial potential and osteoinductive features. This systematic review and meta-analysis aims to elucidate the possible antibacterial properties of the surface in question compared to the untreated titanium surface.

SOURCES

For that purpose, was performed a systematic search on the bases PubMed, Lilacs, Embase, Web Of Science, Cinahl, and Cochrane Central, as well as, manual searches and gray literature.

STUDY SELECTION

The searches resulted in 742 articles, of which 156 followed for full-text reading. Then, 37 were included in the systematic review and 8 were included in meta-analysis.

RESULTS

Fifteen studies revealed significant antibacterial protection using TiO2 nanotube surfaces, while 15 studies found no statistical difference between control and nanotextured surfaces. Meta-analysis of in vitro studies demonstrated relevant bacterial reduction only for studies investigating Staphylococcus aureus in a period of 6 h. Meta-analysis of in vivo studies revealed three times lower bacterial adhesion and proliferation on TiO2 nanotube surfaces.

CONCLUSIONS

TiO2 nanotube topography as a surface for dental implants in preclinical research has demonstrated a positive relationship with antibacterial properties, nevertheless, factors such as anodization protocols, bacteria strains, and mono-culture methods should be taken into consideration, consequently, further studies are necessary to promote clinical translatability.

Unraveling the potential of 3D bioprinted immunomodulatory materials for regulating macrophage polarization: State-of-the-art in bone and associated tissue regeneration

Macrophage-assisted immunomodulation is an alternative strategy in tissue engineering, wherein the interplay between pro-inflammatory and anti-inflammatory macrophage cells and body cells determines the fate of healing or inflammation. Although several reports have demonstrated that tissue regeneration depends on spatial and temporal regulation of the biophysical or biochemical microenvironment of the biomaterial, the underlying molecular mechanism behind immunomodulation is still under consideration for developing immunomodulatory scaffolds. Currently, most fabricated immunomodulatory platforms reported in the literature show regenerative capabilities of a particular tissue, for example, endogenous tissue (e.g., bone, muscle, heart, kidney, and lungs) or exogenous tissue (e.g., skin and eye). In this review, we briefly introduced the necessity of the 3D immunomodulatory scaffolds and nanomaterials, focusing on material properties and their interaction with macrophages for general readers. This review also provides a comprehensive summary of macrophage origin and taxonomy, their diverse functions, and various signal transduction pathways during biomaterial-macrophage interaction, which is particularly helpful for material scientists and clinicians for developing next-generation immunomodulatory scaffolds. From a clinical standpoint, we briefly discussed the role of 3D biomaterial scaffolds and/or nanomaterial composites for macrophage-assisted tissue engineering with a special focus on bone and associated tissues. Finally, a summary with expert opinion is presented to address the challenges and future necessity of 3D bioprinted immunomodulatory materials for tissue engineering.

Antimicrobial and anti-viral effects of selenium nanoparticles and selenoprotein based strategies: COVID-19 and beyond

Deficiency of selenium (Se) has been described in a significant number of COVID-19 patients having a higher incidence of mortality, which makes it a pertinent issue to be addressed clinically for effective management of the COVID-19 pandemic. Se nanoparticles (SeNPs) provide a unique option for managing the havoc caused by the COVID-19 pandemic. SeNPs possess promising anti-inflammatory and anti-fibrotic effects by virtue of their nuclear factor kappa-light-chain-stimulator of activated B cells (NFκB), mitogen-activated protein kinase (MAPKs), and transforming growth factor-beta (TGF-β) modulatory activity. In addition, SeNPs possess remarkable immunomodulatory effects, making them a suitable option for supplementation with a much lower risk of toxicity compared to their elemental counterpart. Further, SeNPs have been shown to curtail viral and microbial infections, thus, making it a novel means to halt viral growth. In addition, it can be administered in the form of aerosol spray, direct injection, or infused thin-film transdermal patches to reduce the spread of this highly contagious viral infection. Moreover, a considerable decrease in the expression of selenoprotein along with enhanced expression of IL-6 in COVID-19 suggests a potential association among selenoprotein expression and COVID-19. In this review, we highlight the unique antimicrobial and antiviral properties of SeNPs and the immunomodulatory potential of selenoproteins. We provide the rationale behind their potentially interesting properties and further exploration in the context of microbial and viral infections. Further, the importance of selenoproteins and their role in maintaining a successful immune response along with their association to Se status is summarized.

A Review of the Antibacterial, Fungicidal and Antiviral Properties of Selenium Nanoparticles

The resistance of microorganisms to antimicrobial drugs is an important problem worldwide. To solve this problem, active searches for antimicrobial components, approaches and therapies are being carried out. Selenium nanoparticles have high potential for antimicrobial activity. The relevance of their application is indisputable, which can be noted due to the significant increase in publications on the topic over the past decade. This review of research publications aims to provide the reader with up-to-date information on the antimicrobial properties of selenium nanoparticles, including susceptible microorganisms, the mechanisms of action of nanoparticles on bacteria and the effect of nanoparticle properties on their antimicrobial activity. This review describes the most complete information on the antiviral, antibacterial and antifungal effects of selenium nanoparticles.

CuS Hybrid Hydrogel for Near-Infrared-Enhanced Infected Wound Healing: A Gelatin-Assisted Synthesis and Direct Incorporation Strategy

Developing antibacterial hydrogels, with good mechanical strength and self-healing ability to resist bacterial invasion and accelerate skin regeneration, is critical for infected full-thickness skin wound treatment. Herein, we report a gelatin-assisted synthesis and direct incorporation strategy to construct a CuS hybrid hydrogel for infected wound healing applications. CuS nanodots (NDs) were synthesized directly inside a gelatin host matrix (Gel-CuS), and these tightly confined and evenly distributed CuS NDs displayed superb dispersibility and stability against oxidation. Gel-CuS was then used to crosslink with oxidized dextran (ODex) to form a Gel-CuS-8/ODex hydrogel (8 stands for the concentration of CuS, in mM) via a facile Schiff-base reaction, which exhibited improved mechanical properties, excellent adhesion and self-healing ability, suitable swelling and degradation behavior, and good biocompatibility. The Gel-CuS-8/ODex hydrogel can act as an efficient antibacterial agent due to its photothermal and photodynamic properties under a 1064 nm laser irradiation. Furthermore, in animal experiments, when being applied as wound dressing, the Gel-CuS-8/ODex hydrogel significantly promoted infected full-thickness cutaneous wound healing through improved epidermis and granulation tissue formation and accelerated generation of new blood vessels, hair follicles, and collagen deposition after proper near-infrared irradiation treatment. This work provides a promising strategy to synthesize functional inorganic nanomaterials tightly and evenly embedded inside modified natural hydrogel networks for wound healing applications.

Osteogenic and anti-inflammatory effects of SLA titanium substrates doped with chitosan-stabilized selenium nanoparticles via a covalent coupling strategy

Osseointegration is a prerequisite for the function of dental implants, and macrophage-dominated immune responses triggered by implantation determine the outcome of ultimate bone healing mediated by osteogenic cells. The present study aimed to develop a modified titanium (Ti) surface by covalently immobilizing chitosan-stabilized selenium nanoparticles (CS-SeNPs) to sandblasted, large grit, and acid-etched (SLA) Ti substrates and further explore its surface characteristics as well as osteogenic and anti-inflammatory activities in vitro. CS-SeNPs were successfully prepared by chemical synthesis and characterized their morphology, elemental composition, particle size, and Zeta potential. Subsequently, three different concentrations of CS-SeNPs were loaded to SLA Ti substrates (Ti-Se1, Ti-Se5, and Ti-Se10) using a covalent coupling strategy, and the SLA Ti surface (Ti-SLA) was used as a control. Scanning electron microscopy images revealed different amounts of CS-SeNPs, and the roughness and wettability of Ti surfaces were less susceptible to Ti substrate pretreatment and CS-SeNP immobilization. Besides, X-ray photoelectron spectroscopy analysis showed that CS-SeNPs were successfully anchored to Ti surfaces. The results of in vitro study showed that the four as-prepared Ti surfaces exhibited good biocompatibility, with Ti-Se1 and Ti-Se5 groups showing enhanced adhesion and differentiation of MC3T3-E1 cells compared with the Ti-SLA group. In addition, Ti-Se1, Ti-Se5, and Ti-Se10 surfaces modulated the secretion of pro-/anti-inflammatory cytokines by inhibiting the nuclear factor kappa B pathway in Raw 264.7 cells. In conclusion, doping SLA Ti substrates with a modest amount of CS-SeNPs (1-5 mM) may be a promising strategy to improve the osteogenic and anti-inflammatory activities of Ti implants.

Titania-Nanotube-Coated Titanium Substrates Promote Osteogenesis and Suppress Osteoclastogenesis via Integrin ανβ3

The balance of bone turnover mediated by osteoclastogenesis and osteogenesis implants that could suppress osteoclastogenesis and promote osteogenesis is an appropriate treatment strategy for osteoporosis patients. Titanium is one of the most applied materials in implants. In this study, titania nanotubes (Ti-NTs) were produced by anodization at 10, 40, and 60 V. We found that Ti-NTs were nontoxic to bone marrow mesenchymal stem cells (BMSCs). Ti-NTs suppressed osteoclast formation and function in a diameter dependent manner in vitro. Furthermore, Ti-NTs enhanced the activity of osteogenesis, expressions of osteogenesis-related marker genes were increased and β-Catenin pathway was active. Alkaline phosphatase (ALP) activity and matrix mineralization were also promoted in vitro. To explore the possible mechanisms, we performed a series of experiments to indicate the effects of Ti-NTs on cytoskeletal organization and integrin ανβ3 expression of osteoclasts and osteoblasts. The results demonstrated that 90-nm-diameter Ti-NTs could suppress the expression of integrin ανβ3 in osteoclast precursor cells. Interestingly, it revealed an opposite effect on BMSCs. Moreover, 90 nm-diameter Ti-NTs prevented ovariectomy (OVX)-induced bone loss. These findings indicated that Ti-NTs could inhibit osteoclastogenesis and enhance osteogenesis; it was mediated via regulation of integrin ανβ3─90 nm-diameter Ti-NT revealed a good biological ability especially suited for osteoporosis treatment.

Green Orange Peel-Mediated Bioinspired Synthesis of Nanoselenium and Its Antibacterial Activity against Methicillin-Resistant Staphylococcus aureus

In this study, green orange peel (GOP) was feasibly evidenced in preparing selenium nanoparticles (SeNPs). Acting as reducing agents, polyphenolic compounds were extracted from GOP at the optimal extraction conditions (at 70 °C for 1.5 h, mass ratio of dried orange peel/distilled water of 5/100). The formation of SeNPs was observed at the wavelength range of 250-300 nm by ultraviolet-visible spectroscopy (UV-vis), and their highest yield could be reached at the following conditions: volume ratio of extract/selenious acid solution (V _Ext/V _Se) of 40/10, synthesis duration of 4 h, selenious acid concentration (C _Se) of 80 mM, and reaction temperature of 120 °C. The highly crystalline structure of SeNPs in the hexagonal phase was characterized by powder X-ray diffraction (XRD) with a lattice parameter of 4.3 Å; meanwhile, their spheres with an average crystal size of 18.3 nm were estimated by high-resolution transmission electron microscope (HR-TEM). The rationale of bioreducing agents extracted from green orange peel for the formation of SeNPs was also recognized by Fourier-transform infrared spectroscopy (FT-IR). The antibacterial investigation of the SeNP sample was assessed against antibiotic-resistant bacteria, typically methicillin-resistant Staphylococcus aureus (MRSA), by executing the zone of inhibition and the minimum inhibitory concentration (MIC) tests. The SeNP sample demonstrated excellent antibacterial activity with an average diameter of inhibition zones of 20.0 ± 0.7 mm and an MIC of 4.94 μg/L. A comparison of the physicochemical properties of SeNPs synthesized from GOP extract by the hydrothermal method with SeNP products from other green reducing agents and other methods as well as its antibacterial activity compared with other nanoparticles and some antibiotics was conducted to highlight the superiority of GOP-mediated green-synthesized SeNPs.

EGCG-coated silver nanoparticles self-assemble with selenium nanowires for treatment of drug-resistant bacterial infections by generating ROS and disrupting biofilms

Bacterial infections pose a serious threat to human health, and the development of new antibiotics has not kept pace with the development of bacterial resistance. Therefore, there is an urgent need to design antibiotic-like nano-formulations that break through bacterial resistance mechanisms. In this work, we successfully synthesized a safe and effective antibacterial nano-formulation of Se@Ag@EGCG by self-assembly of epigallocatechin gallate (EGCG)-coated silver nanoparticles (Ag) on the surface of selenium nanowires (Se). Thein vitrobacteriostatic results showed that 40μg ml^-1Se@Ag@EGCG had significant antibacterial activity against drug-resistantStaphylococcus aureus(S. aureus) andEscherichia coli(E. coli) by destroying the formation of bacterial biofilm, promoting the production of high concentration reactive oxygen species and destroying bacterial cell wall. In addition, the results ofin vivoantibacterial experiments showed that subcutaneous administration of 10 mg kg^-1of Se@Ag@EGCG could promote wound healing by reducing apoptosis and inflammatory responses in infected wounds. It is worth mentioning that the reduced and modified Se@Ag@EGCG by this natural product has negligiblein vivotoxicity. This development strategy of nano-antibacterial materials, which breaks through the drug resistance mechanism, provides new ideas for the development of drugs for drug-resistant bacterial infections.

Antimicrobial potential and osteoblastic cell growth on electrochemically modified titanium surfaces with nanotubes and selenium or silver incorporation

Titanium nanotube surfaces containing silver, zinc, and copper have shown antimicrobial effects without decreasing osteoblastic cell growth. In this in-vitro study we present first results on the biological evaluation of surface modifications by incorporating selenium and silver compounds into titanium-dioxide (TiO₂) nanotubes by electrochemical deposition. TiO₂-nanotubes (TNT) and Phosphate-doped TNT (pTNT) were grown on the surface of Ti6Al4V discs by anodization. Hydroxyapatite (HA), selenium (Se) and silver (Ag) compounds were incorporated by electrochemical deposition. Colony forming units of Staphylococcus epidermidis (DSM 3269) were significantly decreased in SepTNT (0.97 ± 0.18 × 10⁶ CFU/mL), SepTNT-HA (1.2 ± 0.39 × 10⁶ CFU/mL), AgpTNT (1.36 ± 0.42 × 10⁶ CFU/mL) and Ag₂SepTNT (0.999 ± 0.12 × 10⁶ CFU/mL) compared to the non-modified control (2.2 ± 0.21 × 10⁶ CFU/mL). Bacterial adhesion was calculated by measuring the covered area after fluorescence staining. Adhesion was lower in SepTNT (37.93 ± 12%; P = 0.004), pTNT (47.3 ± 6.3%, P = 0.04), AgpTNT (24.9 ± 1.8%; P < 0.001) and Ag₂SepTNT (14.9 ± 4.9%; P < 0.001) compared to the non-modified control (73.7 ± 11%). Biofilm formation and the growth of osteoblastic cells (MG-63) was observed by using Crystal Violet staining. Biofilm formation was reduced in SepTNT (22 ± 3%, P = 0.02) and Ag₂SepTNT discs (23 ± 11%, P = 0.02) compared to the non-modified control (54 ± 8%). In comparison with the non-modified control the modified SepTNT-HA and pTNT surfaces showed a significant higher covered area with osteoblastic MG-63-cells. Scanning electron microscope (SEM) images confirmed findings regarding bacterial and osteoblastic cell growth. These findings show a potential synergistic effect by combining selenium and silver with titanium nanotubes.

Comparison of antimicrobial effect of selenium nanoparticles and silver nanoparticles coated orthodontic mini-implants – An in vitro study

Objectives:

Mini-implants have earned a significant role in orthodontic treatment, by augmenting anchorage requirements. Peri-implantitis contributes to miniscrew failures where progressive peri-implant bone loss occurs in conjunction with soft-tissue inflammation due to the growth of microorganisms such as Streptococcus and Lactobacillus. Nanoparticles have increased surface area and have increased interactions with biological targets like bacteria. This study aims to investigate the antimicrobial activity of silver nanoparticles (AgNP) and selenium nanoparticles (SeNPs) on orthodontic mini-implants.

Material and Methods:

Mini-implant (Ti-6Al-4V) was coated with AgNP and SeNP with biopolymer (Ti-BPAgNP and Ti-BPSeNP) by dip-coating technique. The crystal structure and crystallite size of AgNPs and SeNPs were characterized by the X-ray diffraction (XRD) method. The size distribution and morphology of SeNP and AgNP were determined by a scanning electron microscope (SEM). The antibacterial activity of Ti-BP-AgNP and Ti-BPSeNP was detected from the zone of inhibition by disk diffusion assay.

Results:

The SEM image of AgNP was roughly spherical, uniformly distributed and SeNPs were spherical, well distributed on the biopolymer surface. The area of the zone of inhibition of Ti-BP-SeNP-coated mini-implants shows a negligible difference in antibacterial activity compared to Ti-BPAgNP-coated mini-implants.

Conclusion:

Ti-BP-AgNP and Ti-BP-SeNP showed that a strong antibacterial activity was against Lactobacillus and Staphylococcus aureus. Antibacterial activity against Streptococcus mutans was slightly less than observed in other bacteria. SeNP shows only a marginal difference in antibacterial activity when compared to AgNP.

Interactions between the foreign body reaction and Staphylococcus aureus biomaterial-associated infection. Winning strategies in the derby on biomaterial implant surfaces

Biomaterial-associated infections (BAIs) are an increasing problem where antibiotic therapies are often ineffective. The design of novel strategies to prevent or combat infection requires a better understanding of how an implanted foreign body prevents the immune system from eradicating surface-colonizing pathogens. The objective of this review is to chart factors resulting in sub-optimal clearance of Staphylococcus aureus bacteria involved in BAIs. To this end, we first describe three categories of bacterial mechanisms to counter the host immune system around foreign bodies: direct interaction with host cells, modulation of intercellular communication, and evasion of the immune system. These mechanisms take place in a time frame that differentiates sterile foreign body reactions, BAIs, and soft tissue infections. In addition, we identify experimental interventions in S. aureus BAI that may impact infectious mechanisms. Most experimental treatments modulate the host response to infection or alter the course of BAI through implant surface modulation. In conclusion, the first week after implantation and infection is crucial for the establishment of an S. aureus biofilm that resists the local immune reaction and antibiotic treatment. Although established and chronic S. aureus BAI is still treatable and manageable, the focus of interventions should lie on this first period.

The Advancing of Selenium Nanoparticles Against Infectious Diseases

Infectious diseases, caused by the direct exposure of cellular or acellular pathogens, are found to be closely associated with multiple inflammation and immune responses, keeping one of the top threats to human health. As an indispensable trace element, Selenium (Se) plays important roles in antioxidant defence and redox state regulation along with a variety of specific metabolic pathways. In recent decades, with the development of novel nanotechnology, Selenium nanoparticles (Se NPs) emerged as a promising agent for biomedical uses due to their low toxicity, degradability and high bioavailability. Taking the advantages of the strong ability to trigger apoptosis or autophagy by regulating reactive oxygen species (ROS), Se NPs have been widely used for direct anticancer treatments and pathogen killing/clearance in host cells. With excellent stability and drug encapsulation capacity, Se NPs are now serving as a kind of powerful nano-carriers for anti-cancer, anti-inflammation and anti-infection treatments. Notably, Se NPs are also found to play critical roles in immunity regulations, such as macrophage and T effector cell activation, which thus provides new possibilities to achieve novel nano-immune synergetic strategy for anti-cancer and anti-infection therapies. In this review, we summarized the progress of preparation methods for Se NPs, followed by the advances of their biological functions and mechanisms for biomedical uses, especially in the field of anti-infection treatments. Moreover, we further provide some prospects of Se NPs in anti-infectious diseases, which would be helpful for facilitating their future research progress for anti-infection therapy.

Visible light-induced antibacterial and osteogenic cell proliferation properties of hydrogenated TiO2 nanotubes/Ti foil composite

We successfully fabricated the hydrogenated TiO₂ nanotubes/Ti foil (H-TNTs/f-Ti) composite via one-step anodization and two-step annealing. H-TNTs/f-Ti composite had a higher visible light-induced photoelectric response and more hydroxyl functional groups compared with Ti foil and unmodified TiO₂ nanotubes/Ti foil composite, which contributed to limiting the proliferation of Streptococcus mutans and Porphyromonas gingivalis, promoting the proliferation of MC3T3-E1 cell on the hydroxylated surface, and improving the biocompatibility with osteogenic cells. Our study provides a simple and effective method for significantly improving dental implant efficacy.

Tailoring Materials for Modulation of Macrophage Fate

Human immune system acts as a pivotal role in the tissue homeostasis and disease progression. Immunomodulatory biomaterials that can manipulate innate immunity and adaptive immunity hold great promise for a broad range of prophylactic and therapeutic purposes. This review is focused on the design strategies and principles of immunomodulatory biomaterials from the standpoint of materials science to regulate macrophage fate, such as activation, polarization, adhesion, migration, proliferation, and secretion. It offers a comprehensive survey and discussion on the tunability of material designs regarding physical, chemical, biological, and dynamic cues for modulating macrophage immune response. The range of such tailorable cues encompasses surface properties, surface topography, materials mechanics, materials composition, and materials dynamics. The representative immunoengineering applications selected herein demonstrate how macrophage-immunomodulating biomaterials are being exploited for cancer immunotherapy, infection immunotherapy, tissue regeneration, inflammation resolution, and vaccination. A perspective on the future research directions of immunoregulatory biomaterials is also provided.

Mixed oxide nanotubes in nanomedicine: A dead-end or a bridge to the future?

Nanomedicine has seen a significant rise in the development of new research tools and clinically functional devices. In this regard, significant advances and new commercial applications are expected in the pharmaceutical and orthopedic industries. For advanced orthopedic implant technologies, appropriate nanoscale surface modifications are highly effective strategies and are widely studied in the literature for improving implant performance. It is well-established that implants with nanotubular surfaces show a drastic improvement in new bone creation and gene expression compared to implants without nanotopography. Nevertheless, the scientific and clinical understanding of mixed oxide nanotubes (MONs) and their potential applications, especially in biomedical applications are still in the early stages of development. This review aims to establish a credible platform for the current and future roles of MONs in nanomedicine, particularly in advanced orthopedic implants. We first introduce the concept of MONs and then discuss the preparation strategies. This is followed by a review of the recent advancement of MONs in biomedical applications, including mineralization abilities, biocompatibility, antibacterial activity, cell culture, and animal testing, as well as clinical possibilities. To conclude, we propose that the combination of nanotubular surface modification with incorporating sensor allows clinicians to precisely record patient data as a critical contributor to evidence-based medicine.

Green Synthesis of Selenium and Tellurium Nanoparticles: Current Trends, Biological Properties and Biomedical Applications

The synthesis and assembly of nanoparticles using green technology has been an excellent option in nanotechnology because they are easy to implement, cost-efficient, eco-friendly, risk-free, and amenable to scaling up. They also do not require sophisticated equipment nor well-trained professionals. Bionanotechnology involves various biological systems as suitable nanofactories, including biomolecules, bacteria, fungi, yeasts, and plants. Biologically inspired nanomaterial fabrication approaches have shown great potential to interconnect microbial or plant extract biotechnology and nanotechnology. The present article extensively reviews the eco-friendly production of metalloid nanoparticles, namely made of selenium (SeNPs) and tellurium (TeNPs), using various microorganisms, such as bacteria and fungi, and plants' extracts. It also discusses the methodologies followed by materials scientists and highlights the impact of the experimental sets on the outcomes and shed light on the underlying mechanisms. Moreover, it features the unique properties displayed by these biogenic nanoparticles for a large range of emerging applications in medicine, agriculture, bioengineering, and bioremediation.

The rationale for selenium supplementation in inflammatory bowel disease: A mechanism-based point of view

Management of inflammatory bowel disease (IBD) has always been a challenge for physicians. Current treatment protocols may cause numerous adverse effects. Selenium is known for its putative antiinflammatory properties. Selenium is needed for the biosynthesis of enzymatically active selenoproteins, which contribute to antioxidative defense, and effective function of immune systems. Several studies have shown that patients with IBD have a lower selenium level compared to healthy subjects. Hence, experimental studies mimicking ulcerative colitis and Crohn's disease investigated the effect of selenium supplementation on IBD. Previous studies indicated the following: 1) Selenoproteins can curb the inflammatory response and attenuate oxidative stress. This antiinflammatory property caused remission in animal models of colitis. 2) Selenium supports protective gut microbiota, which indirectly improves management of IBD. 3) Selenium may block some of the predominant tumorigenesis pathways proposed in colitis-associated colorectal cancer. 4) Selenium supplementation showed promising results in preliminary clinical studies, particularly in patients with selenium deficiency. While selenium supplementation seems to be beneficial for IBD, clinical studies have remained too preliminary in this regard. Randomized clinical trials are needed to measure the short-term and long-term effects of selenium on both active and quiescent IBD, particularly in patients with IBD who have documented selenium deficiency.

In situ synthesis of silver or selenium nanoparticles on cationized cellulose fabrics for antimicrobial application

In this study, we developed a method to prepare inorganic nanoparticles in situ on the surface of cationized cellulose using a rapid microwave-assisted synthesis. Selenium nanoparticles (SeNPs) were employed as a novel type of antimicrobial agent and, using the same method, silver nanoparticles (AgNPs) were also prepared. The results demonstrated that both SeNPs and AgNPs of about 100 nm in size were generated on the cationized cellulose fabrics. The antibacterial tests revealed that the presence of SeNPs clearly improved the antibacterial performance of cationized cellulose in a similar way as AgNPs. The functionalised fabrics demonstrated strong antibacterial activity when assessed using the challenge test method, even after repeated washing. Microscopic investigations revealed that the bacterial cells were visually damaged through contact with the functionalised fabrics. Furthermore, the functionalised fabrics showed low cytotoxicity towards human cells when tested in vitro using an indirect contact method. In conclusion, this study provides a new approach to prepare cationic cellulose fabrics functionalised with Se or Ag nanoparticles, which exhibit excellent antimicrobial performance, low cytotoxicity and good laundry durability. We have demonstrated that SeNPs can be a good alternative to AgNPs and the functionalised fabrics have great potential to serve as an anti-infective material.

Multifunctional Antimicrobial Polypeptide-Selenium Nanoparticles Combat Drug-Resistant Bacteria

Antibiotic-resistant bacteria are a severe threat to human health. The World Health Organization's Global Antimicrobial Surveillance System has revealed widespread occurrence of antibiotic resistance among half a million patients across 22 countries, with Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae being the most common resistant species. Antimicrobial nanoparticles are emerging as a promising alternative to antibiotics in the fight against antimicrobial resistance. In this work, selenium nanoparticles coated with the antimicrobial polypeptide, ε-poly-l-lysine, (Se NP-ε-PL) were synthesized and their antibacterial activity and cytotoxicity were investigated. Se NP-ε-PL exhibited significantly greater antibacterial activity against all eight bacterial species tested, including Gram-positive, Gram-negative, and drug-resistant strains, than their individual components, Se NP and ε-PL. The nanoparticles showed no toxicity toward human dermal fibroblasts at the minimum inhibitory concentrations, demonstrating a therapeutic window. Furthermore, unlike the conventional antibiotic kanamycin, Se NP-ε-PL did not readily induce resistance in E. coli or S. aureus. Specifically, S. aureus began to develop resistance to kanamycin from ∼44 generations, whereas it took ∼132 generations for resistance to develop to Se NP-ε-PL. Startlingly, E. coli was not able to develop resistance to the nanoparticles over ∼300 generations. These results indicate that the multifunctional approach of combining Se NP with ε-PL to form Se NP-ε-PL is a highly efficacious new strategy with wide-spectrum antibacterial activity, low cytotoxicity, and significant delays in development of resistance.

Anti-Oxidant and Anti-Endothelial Dysfunctional Properties of Nano-Selenium in vitro and in vivo of Hyperhomocysteinemic Rats

Purpose

Elevation of blood homocysteine (Hcy) level (hyperhomocysteinemia) is a risk factor for cardiovascular disorders and is closely associated with endothelial dysfunction. The present study aims to investigate the protective effect and underlying mechanism of nanoscale selenium (Nano-Se) in Hcy-mediated vascular endothelial cell dysfunction in vitro and in vivo.

Materials and Methods

By incubating vascular endothelial cells with exogenous Hcy and generating hyperhomocysteinemic rat model, the effects of Nano-Se on hyperhomocysteinemia-mediated endothelial dysfunction and its essential mechanisms were investigated.

Results

Nano-Se inhibited Hcy-induced mitochondrial oxidative damage and apoptosis by preventing the downregulation of glutathione peroxidase enzyme 1 and 4 (GPX1, GPX4) in the vascular endothelial cells, thus effectively prevented the vascular damage in vitro and in vivo in the hyperhomocysteinemic rats. Nano-Se possessed similar protective effects but lower toxicity against Hcy in vascular endothelial cells when compared with other forms of Se.

Conclusion

The application of Nano-Se could serve as a novel promising strategy against Hcy-mediated vascular dysfunction with reduced risk of Se toxicity.

In vitro evaluation of bone cements impregnated with selenium nanoparticles stabilized by phosphatidylcholine (PC) for application in bone

One of the most common prophylactic techniques to solve prosthetic joint infection (PJI) is incorporation of antibiotics into acrylic bone cement to prevent bacterial colonization and proliferation by providing local antibiotic delivery directly at the implant site. Further, there has been a significant concern over the efficacy of commonly used antibiotics within bone cement due to the rise in multi-drug resistant (MDR) microorganisms. Selenium is an essential trace element that has multiple beneficial effects for human health and its chemotherapeutic action is well known. It was reported that nanostructured selenium enhanced bone cell adhesion and has an increased osteoblast function. In this context, we used the selenium nanoparticles (SeNPs) to improve antibacterial and antioxidant properties of poly (methyl methacrylate) (PMMA) and tri calcium phosphate (TCP)-based bone cements, and to reduce of the infection risk caused by orthopedic implants. As another novelty of this study, we proposed phosphatidylcholine (PC) as a unique and natural stabilizer in the synthesis of selenium nanoparticles. After the structural analysis of the prepared bone cements was performed, in vitro osteointegration and antibacterial efficiency were tested using MC3T-E1 (mouse osteoblastic cell line) and SaOS-2 (human primary osteogenic sarcoma) cell lines, and S. aureus (Gram positive) and E.coli (Gram negative) strains, respectively. More importantly, PC-SeNPs-reinforced bone cements exhibited significant effect against E. coli, compared to S. aureus and a dose-dependent antibacterial activity against both bacterial strains tested. Meanwhile, these bone cements induced the apoptosis of SaOS-2 through increased reactive oxygen species without negatively influencing the viability of the healthy cell line. Furthermore, the obtained confocal images revealed that PC-SeNPs (103.7 ± 0.56 nm) altered the cytoskeletal structure of SaOS-2 owing to SeNPs-induced apoptosis, when MC3T3-E1 cells showed a typical spindle-shaped morphology. Taken together, these results highlighted the potential of PC-SeNPs-doped bone cements as an effective graft material in bone applications.

Enhanced Antibacterial Activity of Se Nanoparticles Upon Coating with Recombinant Spider Silk Protein eADF4(κ16)

PURPOSE

Selenium nanoparticles (Se NPs) are promising antibacterial agents to tackle the growing problem of antimicrobial resistance. The aim of this study was to fabricate Se NPs with a net positive charge to enhance their antibacterial efficacy.

METHODS

Se NPs were coated with a positively charged protein - recombinant spider silk protein eADF4(κ16) - to give them a net positive surface charge. Their cytotoxicity and antibacterial activity were investigated, with negatively charged polyvinyl alcohol coated Se NPs as a control. Besides, these eADF4(κ16)-coated Se NPs were immobilized on the spider silk films, and the antibacterial activity of these films was investigated.

RESULTS

Compared to the negatively charged polyvinyl alcohol coated Se NPs, the positively charged eADF4(κ16)-coated Se NPs demonstrated a much higher bactericidal efficacy against the Gram-negative bacteria E. coli, with a minimum bactericidal concentration (MBC) approximately 50 times lower than that of negatively charged Se NPs. Cytotoxicity testing showed that the eADF4(κ16)-coated Se NPs are safe to both Balb/3T3 mouse embryo fibroblasts and HaCaT human skin keratinocytes up to 31 µg/mL, which is much higher than the MBC of these particles against E. coli (8 ± 1 µg/mL). In addition, antibacterial coatings were created by immobilising the eADF4(κ16)-coated Se NPs on positively charged spider silk films and these were shown to retain good bactericidal efficacy and overcome the issue of low particle stability in culture broth. It was found that these Se NPs needed to be released from the film surface in order to exert their antibacterial effects and this release can be regulated by the surface charge of the film, such as the change of the spider silk protein used.

CONCLUSION

Overall, eADF4(κ16)-coated Se NPs are promising new antibacterial agents against life-threatening bacteria.

Novel Hybrid Composites Based on PVA/SeTiO2 Nanoparticles and Natural Hydroxyapatite for Orthopedic Applications: Correlations between Structural, Morphological and Biocompatibility Properties

The properties of poly(vinyl alcohol) (PVA)-based composites recommend this material as a good candidate for the replacement of damaged cartilage, subchondral bone, meniscus, humeral joint and other orthopedic applications. The manufacturing process can be manipulated to generate the desired biomechanical properties. However, the main shortcomings of PVA hydrogels are related to poor strength and bioactivity. To overcome this situation, reinforcing elements are added to the PVA matrix. The aim of our work was to develop and characterize a novel composition based on PVA reinforced with Se-doped TiO2 nanoparticles and natural hydroxyapatite (HA), for possible orthopedic applications. The PVA/Se-doped TiO2 composites with and without HA were structurally investigated by FTIR and XRD, in order to confirm the incorporation of the inorganic phase in the polymeric structure, and by SEM and XRF, to evidence the ultrastructural details and dispersion of nanoparticles in the PVA matrix. Both the mechanical and structural properties of the composites demonstrated a synergic reinforcing effect of HA and Se-doped TiO2 nanoparticles. Moreover, the tailorable properties of the composites were proved by the viability and differentiation potential of the bone marrow mesenchymal stem cells (BMMSC) to osteogenic, chondrogenic and adipogenic lineages. The novel hybrid PVA composites show suitable structural, mechanical and biological features to be considered as a promising biomaterial for articular cartilage and subchondral bone repair.

Improved Immunoregulation of Ultra-Low-Dose Silver Nanoparticle-Loaded TiO2 Nanotubes via M2 Macrophage Polarization by Regulating GLUT1 and Autophagy

Introduction

The bone regeneration of endosseous implanted biomaterials is often impaired by the host immune response, especially macrophage-related inflammation which plays an important role in the bone healing process. Thus, it is a promising strategy to design an osteo-immunomodulatory biomaterial to take advantage of the macrophage-related immune response and improve the osseointegration performance of the implant.

Methods

In this study, we developed an antibacterial silver nanoparticle-loaded TiO₂ nanotubes (Ag@TiO₂-NTs) using an electrochemical anodization method to make the surface modification and investigated the influences of Ag@TiO₂-NTs on the macrophage polarization, osteo-immune microenvironment as well as its potential molecular mechanisms in vitro and in vivo.

Results

The results showed that Ag@TiO₂-NTs with controlled releasing of ultra-low-dose Ag⁺ ions had the excellent ability to induce the macrophage polarization towards the M2 phenotype and create a suitable osteo-immune microenvironment in vitro, via inhibiting PI3K/Akt, suppressing the downstream effector GLUT1, and activating autophagy. Moreover, Ag@TiO₂-NTs surface could improve bone formation, suppress inflammation, and promote osteo-immune microenvironment compared to the TiO₂-NTs and polished Ti surfaces in vivo. These findings suggested that Ag@TiO₂-NTs with controlled releasing of ultra-low-dose Ag⁺ ions could not only inhibit the inflammation process but also promote the bone healing by inducing healing-associated M2 polarization.

Discussion

Using this surface modification strategy to modulate the macrophage-related immune response, rather than prevent the host response, maybe a promising strategy for implant surgeries in the future.

Construction of selenium-embedded mesoporous silica with improved antibacterial activity

In this work, different concentrations of Se-incorporated mesoporous silica nanospheres (MSNs) (5Se/MSNs and 10Se/MSNs) were successfully synthesized via an in-situ one-pot method. Their physicochemical properties were characterized by X-ray diffraction (XRD), transmission electron microscopy, and X-ray photoelectron spectroscopy (XPS). The release behaviors of Se and Si were investigated in a phosphate-buffered saline (pH = 5.5, 7.4) solution (PBS). In vitro antibacterial properties of the prepared samples were evaluated with Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The cytocompatibilities of the samples were then assessed using L929 cells. Se nanoparticles were successfully loaded onto the outer and inner surfaces of hierarchical mesoporous silica. The sizes of the Se/MSNs nanoparticles were approximately 120 nm for 5Se/MSNs and 210 nm for 10Se/MSNs. The XRD and XPS results showed that Se mainly existed in the form of Se⁰ in the samples. The Se/MSNs exhibited stable and sustained release of both Si and Se in PBS solution. In vitro antibactericidal tests indicated that the Se/MSNs could exhibit better antibacterial activity against S. aureus than pure Se nanoparticles after 6 and 24 h of culturing. The minimal inhibitory concentration (MIC) of 10Se/MSN was 100 μg mL^-1. However, the Se/MSNs exhibited no inhibitory effect on E. coli bacteria. Furthermore, all the samples exhibited excellent cell viability. These studies demonstrate initial in vitro antibacterial activity and good cytocompatibility of Se/MSNs and their potential application in antibacterial nanomedicine.

Macrophage-Targeted Isoniazid-Selenium Nanoparticles Promote Antimicrobial Immunity and Synergize Bactericidal Destruction of Tuberculosis Bacilli

Pathogenesis hallmarks for tuberculosis (TB) are the Mycobacterium tuberculosis (Mtb) escape from phagolysosomal destruction and limited drug delivery into infected cells. Several nanomaterials can be entrapped in lysosomes, but the development of functional nanomaterials to promote phagolysosomal Mtb clearance remains a big challenge. Here, we report on the bactericidal effects of selenium nanoparticles (Se NPs) against Mtb and further introduce a novel nanomaterial-assisted anti-TB strategy manipulating Ison@Man-Se NPs for synergistic drug-induced and phagolysosomal destruction of Mtb. Ison@Man-Se NPs preferentially entered macrophages and accumulated in lysosomes releasing Isoniazid. Surprisingly, Ison@Man-Se/Man-Se NPs further promoted the fusion of Mtb into lysosomes for synergistic lysosomal and Isoniazid destruction of Mtb. Concurrently, Ison@Man-Se/Man-Se NPs also induced autophagy sequestration of Mtb, evolving into lysosome-associated autophagosomal Mtb degradation linked to ROS-mitochondrial and PI3K/Akt/mTOR signaling pathways. This novel nanomaterial-assisted anti-TB strategy manipulating antimicrobial immunity and Mtb clearance may potentially serve in more effective therapeutics against TB and drug-resistant TB.

Green Synthesized BSA-Coated Selenium Nanoparticles Inhibit Bacterial Growth While Promoting Mammalian Cell Growth

Background

Selenium is an essential trace element that is critical for many biological processes. Selenium nanoparticles (SeNPs) have shown more promise than other forms of selenium due to their low cytotoxicity and high bioavailability.

Methods

In this work, a one-step method was demonstrated for fabricating bovine serum albumin (BSA) stabilized SeNPs using ascorbic acid as the reductant. Human dermal fibroblasts were used to assess mammalian cytotoxicity, and Staphylococcus aureus and Escherichia coli were used to assess antibacterial performance.

Results

These SeNPs demonstrated increased fibroblast growth and reduced Staphylococcus aureus growth with a fibroblast IC₅₀ value (>681 μg/mL) 1 order of magnitude higher than that for bacteria at day 1.

Conclusion

This study demonstrated the promise of this synthesis process in achieving controllable selenium nanoparticle sizes without the use of strong basic solvents for improved antibacterial properties.

Antibacterial activity of AgNPs–TiO2 nanotubes: influence of different nanoparticle stabilizers

Enhanced antibacterial properties of nanomaterials such as TiO₂ nanotubes (TNTs) and silver nanoparticles (AgNPs) have attracted much attention in biomedicine and industry. The antibacterial properties of nanoparticles depend, among others, on the functionalization layer of the nanoparticles. However, the more complex information about the influence of different functionalization layers on antibacterial properties of nanoparticle decorated surfaces is still missing. Here we show the array of ∼50 nm diameter TNTs decorated with ∼50 nm AgNPs having different functionalization layers such as polyvinylpyrrolidone, branched polyethyleneimine, citrate, lipoic acid, and polyethylene glycol. To assess the antibacterial properties, the viability of Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) has been assessed. Our results showed that the functional layer of nanoparticles plays an important role in antibacterial properties and the synergistic effect such nanoparticles and TiO₂ nanotubes have had different effects on adhesion and viability of G⁻ and G⁺ bacteria. These findings could help researchers to optimally design any surfaces to be used as an antibacterial including the implantable titanium biomaterials.

Synergictic antibacterial effect of AgNPs–TiO₂ nanotubes is influenced by different nanoparticle stabilizers.

Bacteria-Responsive Biomimetic Selenium Nanosystem for Multidrug-Resistant Bacterial Infection Detection and Inhibition

Multidrug-resistant (MDR) bacterial infections are a severe threat to public health owing to their high risk of fatality. Noticeably, the premature degradation and undeveloped imaging ability of antibiotics still remain challenging. Herein, a selenium nanosystem in response to a bacteria-infected microenvironment is proposed as an antibiotic substitute to detect and inhibit methicillin-resistant Staphylococcus aureus (MRSA) with a combined strategy. Using natural red blood cell membrane (RBCM) and bacteria-responsive gelatin nanoparticles (GNPs), the Ru-Se@GNP-RBCM nanosystem was constructed for effective delivery of Ru-complex-modified selenium nanoparticles (Ru-Se NPs). Taking advantage of natural RBCM, the immune system clearance was reduced and exotoxins were neutralized efficiently. GNPs could be degraded by gelatinase in pathogen-infected areas in situ; therefore, Ru-Se NPs were released to destroy the bacteria cells. Ru-Se NPs with intense fluorescence imaging capability could accurately monitor the infection treatment process. Moreover, excellent in vivo bacteria elimination and a facilitated wound healing process were confirmed by two kinds of MRSA-infected mice models. Overall, the above advantages proved that the prepared nanosystem is a promising antibiotic alternative to combat the ever-threatening multidrug-resistant bacteria.

Selenium Nanoparticle Protection of Fibroblast Stress: Activation of ATF4 and Bcl-xL Expression

Background

In recent years, selenium nanostructures have been researched due to their antibacterial properties, low toxicity to mammalian cells, and high biological efficacy. However, the clinical implementation of the use of selenium has received mixed results, and there is much work needed to improve the understanding of the biological mechanisms involved in the observed cellular responses.

Materials and methods

In this work, an investigation into the mechanistic pathways of selenium nanoparticles (SeNPs) in biological systems was conducted by studying the changes in gene expression of ATF4, Bcl-xL, BAD2, HSP70, and SOD2 in non-cancerous human dermal fibroblasts (HDF) under oxidative stress, nutrient deprivation stress, and no treatment (control) conditions.

Results

This study revealed that SeNP incubation led to reduced internal reactive oxygen species (ROS) generation for all conditions tested, thus, providing a protective environment for HDF. At the stress conditions, the expression of ATF4 and Bcl-xL increased for cells treated with SeNP incubation, leading to attenuation of the cells under stress. These results also hint at reductive stress causing a detrimental impact to cell proliferation under routine cell passaging conditions.

Conclusion

In summary, this study highlights some possible mechanistic pathways implicated in the action of SeNPs that warrant further investigation (specifically, reducing stress conditions for HDF) and continues to support the promise of SeNPs in a wide range of medical applications.

Zn-incorporation with graphene oxide on Ti substrates surface to improve osteogenic activity and inhibit bacterial adhesion

The poor osseointegration and postoperative bacterial infection are prominently responsible for the failure of titanium (Ti)-based implant in clinic. To address above issues, methacryloyl modified graphene oxide (GOMA) as zinc ions (Zn²⁺ ) reservoir and release platform was fabricated on the Ti substrates with cathode electrophoresis deposition (EPD). Afterward, phenylboronic acid (PBA) functionalization methacryloyl-gelatin (GelMA-PBA) was reacting with GOMA through in situ free-radical polymerization to prepare GO-Zn/GelMA-PBA coating. The obtained coating was confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, and Zn ions release property, respectively. in vitro cellular experiments including cell activity, alkaline phosphatase, collagen secretion, extracellular matrix (ECM) mineralization, osteogenic genes and proteins, revealed that GO-Zn/GelMA-PBA coating was beneficial for enhancing the adhesion, proliferation, and differentiation of osteoblasts. The positive results were related to the existence of gelatin, formation of boronic ester between PBA groups, and carbohydrates of osteoblasts surface. Meanwhile, antibacterial assay against Staphylococcus aureus and Pseudomonas aeruginosa confirmed that GO-Zn/GelMA-PBA coating on Ti substrates had superior antibacterial capacity, availably inhibited the bacterial adhesion, and prevented formation of biofilm. Hence, the study provides a promising strategy for designing pro-osteogenesis and antibacterial coating on Ti substrates for orthopedic applications.

Antibacterial potential associated with drug-delivery built TiO2 nanotubes in biomedical implants

The fast evolution of surface treatments for biomedical implants and the concern with their contact with cells and microorganisms at early phases of bone healing has boosted the development of surface topographies presenting drug delivery potential for, among other features, bacterial growth inhibition without impairing cell adhesion. A diverse set of metal ions and nanoparticles (NPs) present antibacterial properties of their own, which can be applied to improve the implant local response to contamination. Considering the promising combination of nanostructured surfaces with antibacterial materials, this critical review describes a variety of antibacterial effects attributed to specific metals, ions and their combinations. Also, it explains the TiO2 nanotubes (TNTs) surface creation, in which the possibility of aggregation of an active drug delivery system is applicable. Also, we discuss the pertinent literature related to the state of the art of drug incorporation of NPs with antibacterial properties inside TNTs, along with the promising future perspectives of in situ drug delivery systems aggregated to biomedical implants.

Enhanced antibacterial and anticancer properties of Se-NPs decorated TiO2 nanotube film

Selenium nanoparticle modified surfaces attract increasing attention in the field of tissue engineering. Selenium exhibits strong anticancer, antibacterial and anti-inflammatory properties and it maintains relatively low off-target cytotoxicity. In our paper, we present the fabrication, characterization and cytocompatibility of titanium oxide (TiO₂) nanotube surface decorated with various surface densities of chemically synthesized selenium nanoparticles. To evaluate antibacterial and anti-cancer properties of such nanostructured surface, gram negative bacteria E. coli, cancerous osteoblast like MG-63 cells and non-cancerous fibroblast NIH/3T3 were cultured on designed surfaces. Our results suggested that selenium nanoparticles improved antibacterial properties of titanium dioxide nanotubes and confirmed the anticancer activity towards MG-63 cells, with increasing surface density of nanoparticles. Further, the selenium decorated TiO₂ nanotubes suggested deteriorating effect on the cell adhesion and viability of non-cancerous NIH/3T3 cells. Thus, we demonstrated that selenium nanoparticles decorated TiO₂ nanotubes synthesized using sodium selenite and glutathione can be used to control bacterial infections and prevent the growth of cancerous cells. However, the higher surface density of nanoparticles adsorbed on the surface was found to be cytotoxic for non-cancerous NIH/3T3 cells and thus it might complicate the integration of biomaterial into the host tissue. Therefore, an optimal surface density of selenium nanoparticles must be found to effectively kill bacteria and cancer cells, while remaining favorable for normal cells.

Copper-nanoparticle-embedded hydrogel for killing bacteria and promoting wound healing with photothermal therapy

Bacterial infections at wound tissue sites usually delay the wound healing process and even result in severe life-threatening complications. Therefore, it is imperative to develop an efficient strategy to simultaneously enhance the antibacterial abilities and improve the wound healing process. Here, we report a composite hydrogel composed of methacrylate-modified gelatin (Gel-MA) and N,N-bis(acryloyl)cystamine (BACA)-chelated Cu nanoparticles (Cu NPs) via radical polymerization with a photoinitiator. The Cu NPs could effectively convert NIR laser irradiation (808 nm) energy into localized heat due to the localized surface plasmon resonance (LSPR) effect for effecting photothermal therapy. In vitro antimicrobial experiments revealed that the hybrid hydrogel exhibited predominant antibacterial efficacy against both Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria, while Cu-NP-embedded hydrogel + laser group exhibited superior antibacterial capacity. The excellent antibacterial properties can be attributed to the synergistic effect of photothermal performance and rapid release of copper ions (Cu²⁺) because of the laser irradiation of Cu NPs. Moreover, the released Cu²⁺ could stimulate NIH-3T3 fibroblast proliferation without any inflammatory responses. Moreover, chronic wound healing process of S. aureus-infected model was significantly accelerated with prominent antibacterial ability, reduced inflammatory response, and promoted angiogenesis ability in vivo. In summary, Cu-NP-embedded hydrogels are a promising candidate for skin tissue regeneration and potentially valuable for clinical applications.

Application of Antimicrobial Nanoparticles in Dentistry

Oral cavity incessantly encounters a plethora of microorganisms. Plaque biofilm-a major cause of caries, periodontitis and other dental diseases-is a complex community of bacteria or fungi that causes infection by protecting pathogenic microorganisms from external drug agents and escaping the host defense mechanisms. Antimicrobial nanoparticles are promising because of several advantages such as ultra-small sizes, large surface-area-to-mass ratio and special physical and chemical properties. To better summarize explorations of antimicrobial nanoparticles and provide directions for future studies, we present the following critical review. The keywords "nanoparticle," "anti-infective or antibacterial or antimicrobial" and "dentistry" were retrieved from Pubmed, Scopus, Embase and Web of Science databases in the last five years. A total of 172 articles met the requirements were included and discussed in this review. The results show that superior antibacterial properties of nanoparticle biomaterials bring broad prospects in the oral field. This review presents the development, applications and underneath mechanisms of antibacterial nanoparticles in dentistry including restorative dentistry, endodontics, implantology, orthodontics, dental prostheses and periodontal field.

Novel mechanisms of selenate and selenite reduction in the obligate aerobic bacterium Comamonas testosteroni S44

Selenium oxyanion reduction is an effective detoxification or/and assimilation processes in organisms, but little is known the mechanisms in aerobic bacteria. Aerobic Comamonas testosteroni S44 reduces Se(VI)/Se(IV) to less-toxic elemental selenium nanoparticles (SeNPs). For Se(VI) reduction, sulfate and Se(VI) reduction displayed a competitive relationship. When essential sulfate reducing genes were respectively disrupted, Se(VI) was not reduced to red-colored SeNPs. Consequently, Se(VI) reduction was catalyzed by enzymes of the sulfate reducing pathway. For Se(IV) reduction, one of the potential periplasm molybdenum oxidoreductase named SerT was screened and further used to analyze Se(IV) reduction. Compared to the wild type and the complemented mutant strain, the ability of Se(IV) reduction was reduced 75% in the deletion mutant ΔserT. Moreover, the Se(IV) reduction rate was significantly enhanced when the gene serT was overexpressed in Escherichia coli W3110. In addition, Se(IV) was reduced to SeNPs by the purified SerT with the presence of NADPH as the electron donor in vitro, showing a V_max of 61 nmol/min·mg and a K_m of 180 μmol/L. A model of Se(VI)/Se(IV) reduction was generated in aerobic C. testosteroni S44. This work provides new insights into the molecular mechanisms of Se(VI)/Se(IV) reduction activities in aerobic bacteria.

Antibacterial activity and inflammation inhibition of ZnO nanoparticles embedded TiO2 nanotubes

Titanium (Ti) with nanoscale structure on the surface exhibits excellent biocompatibility and bone integration. Once implanted, the surgical implantation may lead to bacterial infection and inflammatory reaction, which cause the implant failure. In this work, irregular and nanorod-shaped ZnO nanoparticles were doped into TiO₂ nanotubes (TNTs) with inner diameter of about 50 nm by electro-deposition. The antibacterial properties of ZnO incorporated into TiO₂ nanotubes (TNTs/ZnO) were evaluated using Staphylococcus aureus (S. aureus). Zn ions released from the nanoparticles and the morphology could work together, improving antibacterial effectiveness up to 99.3% compared with the TNTs. Macrophages were cultured on the samples to determine their respective anti-inflammatory properties. The proliferation and viability of macrophages were evaluated by the CCK-8 method and Live&Dead stain, and the morphology of the cells was observed by scanning electron microscopy. Results indicated that TNTs/ZnO has a significant inhibitory effect on the proliferation and adhesion of macrophages, which could be used to prevent chronic inflammation and control the inflammatory reaction. Besides, the release of Zn ions from the ZnO nanoparticles is a long-term process, which could be beneficial for bone integration. Results demonstrate that ZnO deposited into TNTs improved the antibacterial effectiveness and weakened the inflammatory reaction of titanium-based implants, which is a promising approach to enhance their bioactivity.

Deferoxamine loaded titania nanotubes substrates regulate osteogenic and angiogenic differentiation of MSCs via activation of HIF-1α signaling

To develop biomaterials for inducing osteogenic and angiogenic differentiation of mesenchymal stem cells (MSCs) is crucial for bone repair. In this study, we employed titania nanotubes (TNT) as drug nanoreservoirs to load deferoxamine (DFO), and then deposited chitosan (Chi) and gelatin (Gel) multilayer as coverage structure via layer-by-layer (LBL) assembly technique, resulting in TNT-DFO-LBL substrates. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements were employed to characterize the physical and chemical properties of the substrates. The results proved the successful fabrication of multilayer coating on TNT array. DFO released from the TNT arrays in a sustained manner. The drug-device combination titanium (Ti) substrates positively improved the adhesion, proliferation, osteogenic/angiogenic differentiation of MSCs and mediated the growth behavior of human umbilical vein endothelial cells (HUVECs). Moreover, the TNT-DFO-LBL substrates up-regulated osteogenic and angiogenic differentiation related genes expression of MSCs by activating HIF-1α signaling pathway. The approach presents here has a potential impact on the development of high quality Ti-based orthopedic implants.

Proteins enriched in charged amino acids control the formation and stabilization of selenium nanoparticles in Comamonas testosteroni S44

Elemental selenium nanoparticles (SeNPs) are useful in medicine, environmental remediation and in material science. Biosynthesized SeNPs (BioSeNPs) by bacteria are cheap, eco-friendly and have a lower cytotoxicity in comparison with chemically synthesized ones. Organic matters were found to cap on the surface of BioSeNPs, but the functions were still not entirely clear. The purified BioSeNPs were coated in a thick layer of organic substrates observed by transmission electron microscopy (TEM). Fourier Transform Infrared (FT-IR) and quantitative detection of the coating agents showed that one gram of purified BioSeNPs bound 1069 mg proteins, 23 mg carbohydrates and only very limited amounts of lipids. Proteomics of BioSeNPs showed more than 800 proteins bound to BioSeNPs. Proteins enriched in charged amino acids are the major factor thought to govern the formation process and stabilization of BioSeNPs in bacteria. In view of the results reported here, a schematic model for the molecular mechanism of BioSeNPs formation in bacteria is proposed. These findings are helpful for the artificial green synthesis of stable SeNPs under specific condition and guiding the surface modification of SeNPs for medicine application.

Investigation of osteogenic responses of Fe-incorporated micro/nano-hierarchical structures on titanium surfaces

Fe incorporated micro/nano topographical titanium substrates are fabricated to synergistically regulate osteogenic responses in vitro and osseointegration in vivo.

M2 macrophages contribute to osteogenesis and angiogenesis on nanotubular TiO2 surfaces

The monocyte/macrophage system plays an essential role in the host response and the fate of endosseous implanted materials. Macrophage behavior was thought to be regulated by nanostructured titanium which has been considered as a very promising candidate for dental implants. However, there is little known for subsequent effects of these activated macrophages on osteogenesis and angiogenesis which were essential for bone integration. Here we presented two different dimensions of titanium nanotubes generated by anodic oxidation at 10 V (NT 10) and 20 V (NT 20), respectively. The behavior of macrophages on the surfaces was evaluated, and their conditioned medium (CM) was collected to stimulate MC3T3 and HUVECs, with commercially pure titanium (cp Ti) as control. We found that NT 20 induced macrophage activation similar to the anti-inflammatory M2 macrophage state with the enhanced expression of IL-10 and ARG, while NT 10 was associated with M1 macrophage phenotype characterized by high levels of IL-1β, iNOS and TNF-α. Furthermore, the osteogenic capacity of MC3T3 in CM from NT 20 was enhanced (NT 20 > NT 10 ≈ cp Ti) and the tube formation capacity of HUVECs was promoted in CM from nanotubular surfaces with increasing tube dimensions (NT 20 > NT 10 > cp Ti). Our data suggest that dental implants with the large nanotube dimension surface could result in a favorable osteoimmunomodulatory microenvironment for the establishment of osseointegration.

H2O2-Depleting and O2-Generating Selenium Nanoparticles for Fluorescence Imaging and Photodynamic Treatment of Proinflammatory-Activated Macrophages

Macrophages have a pivotal role in chronic inflammatory diseases (CIDs), so imaging and controlling activated macrophage is critical for detecting and reducing chronic inflammation. In this study, photodynamic selenium nanoparticles (SeNPs) with photosensitive and macrophage-targeting bilayers were developed. The first layer of the photosensitive macromolecule was composed of a conjugate of a photosensitizer (rose bengal, RB) and a thiolated chitosan (chitosan-glutathione), resulting in a plasmonic coupling-induced red shift and broadening of RB absorption bands with increased absorption intensity. Electron paramagnetic resonance (EPR) and diphenylanthracene (DPA) quenching studies revealed that the SeNPs that were coated with the photosensitive layer were more effective than RB alone in producing singlet oxygen (¹O₂) under photoirradiation. The second layer of the activated macrophage-targetable macromolecule was synthesized by conjugation of hyaluronic acid with folic acid using an ethylenediamine linker. Proinflammatory-activated macrophages rapidly internalized the SeNPs that were covered with the targeting ligand, exhibiting a much stronger fluorescence signal of the SeNPs than did the nonactivated macrophages. Since proinflammatory-activated macrophage was known to generate a substantial amount of H₂O₂ while the inflamed site generally caused inflammation-associated tissue hypoxia, the SeNPs were further modified with O₂ self-sufficient function for photodynamic therapy. Catalase was immobilized on the SeNPs by the formation of disulfide bonds. Intracellular reduction of disulfide bonds induced the subsequent release of catalase, which catalyzed the decomposition of H₂O₂. The H₂O₂-depleting and O₂-generating photodynamic SeNPs efficiently killed activated macrophages and quenched the intracellular H₂O₂ and NO that are associated with inflammation. The SeNPs may have potential as a theranostic nanomaterial to image and control the activation of macrophages.