Bimetallic silver-platinum nanoparticles with combined osteo-promotive and antimicrobial activity

Increased Cytotoxicity of Bimetallic Ultrasmall Silver-Platinum Nanoparticles (2 nm) on Cells and Bacteria in Comparison to Silver Nanoparticles of the Same Size

Ultrasmall nanoparticles (diameter 2 nm) of silver, platinum, and bimetallic nanoparticles (molar ratio of Ag:Pt 0:100; 20:80; 50:50; 70:30; 100:0), stabilized by the thiolated ligand glutathione, were prepared and characterized by transmission electron microscopy, differential centrifugal sedimentation, X-ray photoelectron spectroscopy, small-angle X-ray scattering, X-ray powder diffraction, and NMR spectroscopy in aqueous dispersion. Gold nanoparticles of the same size were prepared as control. The particles were fluorescently labeled by conjugation of the dye AlexaFluor-647 via copper-catalyzed azide-alkyne cycloaddition after converting amine groups of glutathione into azide groups. All nanoparticles were well taken up by HeLa cells. The cytotoxicity was assessed with an MTT test on HeLa cells and minimal inhibitory concentration (MIC) tests on the bacteria Escherichia coli and Staphylococcus xylosus. Notably, bimetallic AgPt nanoparticles had a higher cytotoxicity against cells and bacteria than monometallic silver nanoparticles or a physical mixture of silver and platinum nanoparticles. However, the measured release of silver ions from monometallic and bimetallic silver nanoparticles in water was very low despite the ultrasmall size and the associated high specific surface area. This is probably due to the surface protection by a dense layer of thiolated ligand glutathione. Thus, the enhanced cytotoxicity of bimetallic AgPt nanoparticles is caused by the biological environment in cell culture media, together with a polarization of silver by platinum.

Bioinspired silver nanoparticle-based nanocomposites for effective control of plant pathogens: A review

Plant pathogens, including bacteria, fungi, and viruses, pose significant challenges to the farming community due to their extensive diversity, the rapidly evolving phenomenon of multi-drug resistance (MDR), and the limited availability of effective control measures. Amid mounting global pressure, particularly from the World Health Organization, to limit the use of antibiotics in agriculture and livestock management, there is increasing consideration of engineered nanomaterials (ENMs) as promising alternatives for antimicrobial applications. Studies focusing on the application of ENMs in the fight against MDR pathogens are receiving increasing attention, driven by significant losses in agriculture and critical knowledge gaps in this crucial field. In this review, we explore the potential contributions of silver nanoparticles (AgNPs) and their nanocomposites in combating plant diseases, within the emerging interdisciplinary arena of nano-phytopathology. AgNPs and their nanocomposites are increasingly acknowledged as promising countermeasures against plant pathogens, owing to their unique physicochemical characteristics and inherent antimicrobial properties. This review explores recent advancements in engineered nanocomposites, highlights their diverse mechanisms for pathogen control, and draws attention to their potential in antibacterial, antifungal, and antiviral applications. In the discussion, we briefly address three crucial dimensions of combating plant pathogens: green synthesis approaches, toxicity-environmental concerns, and factors influencing antimicrobial efficacy. Finally, we outline recent advancements, existing challenges, and prospects in scholarly research to facilitate the integration of nanotechnology across interdisciplinary fields for more effective treatment and prevention of plant diseases.

Nanobiomaterials: exploring mechanistic roles in combating microbial infections and cancer

The initiation of the "nanotechnology era" within the past decade has been prominently marked by advancements in biomaterials. This intersection has opened up numerous possibilities for enhancing the detection, diagnosis, and treatment of various illnesses by leveraging the synergy between biomaterials and nanotechnology. The term "nano biomaterials" referring to biomaterials featuring constituent or surface feature sizes below 100 nm, presents a realm of extraordinary materials endowed with unique structures and properties. Beyond addressing common biomedical challenges, these nano biomaterials contribute unprecedented insights and principles that enrich our understanding of biology, medicine, and materials science. A critical evaluation of recent technological progress in employing biomaterials in medicine is essential, along with an exploration of potential future trends. Nanotechnology breakthroughs have yielded novel surfaces, materials, and configurations with notable applications in the biomedical domain. The integration of nanotechnology has already begun to enhance traditional biomedical practices across diverse fields such as tissue engineering, intelligent systems, the utilization of nanocomposites in implant design, controlled release systems, biosensors, and more. This mini review encapsulates insights into biomaterials, encompassing their types, synthesis methods, and the roles of organic and inorganic nanoparticles, elucidating their mechanisms of action. Furthermore, the focus is squarely placed on nano biomaterials and their versatile applications, with a particular emphasis on their roles in anticancer and antimicrobial interventions. This review underscores the dynamic landscape of nanotechnology, envisioning a future where nano biomaterials play a pivotal role in advancing medical applications, particularly in combating cancer and microbial infections.

Ultrastructure and Surface Composition of Glutathione-Terminated Ultrasmall Silver, Gold, Platinum, and Alloyed Silver-Platinum Nanoparticles (2 nm)

Alloyed ultrasmall silver-platinum nanoparticles (molar ratio Ag:Pt = 50:50) were prepared and compared to pure silver, platinum, and gold nanoparticles, all with a metallic core diameter of 2 nm. They were surface-stabilized by a layer of glutathione (GSH). A comprehensive characterization by high-resolution transmission electron microscopy (HRTEM), electron diffraction (ED), X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), differential centrifugal sedimentation (DCS), and UV spectroscopy showed their size both in the dry and in the water-dispersed state (hydrodynamic diameter). Solution NMR spectroscopy (1H, 13C, COSY, HSQC, HMBC, and DOSY) showed the nature of the glutathione shell including the number of GSH ligands on each nanoparticle (about 200 with a molecular footprint of 0.063 nm2 each). It furthermore showed that there are at least two different positions for the GSH ligand on the gold nanoparticle surface. Platinum strongly reduced the resolution of the NMR spectra compared to silver and gold, also in the alloyed nanoparticles. X-ray photoelectron spectroscopy (XPS) showed that silver, platinum, and silver-platinum particles were at least partially oxidized to Ag(+I) and Pt(+II), whereas the gold nanoparticles showed no sign of oxidation. Platinum and gold nanoparticles were well crystalline but twinned (fcc lattice) despite the small particle size. Silver was crystalline in electron diffraction but not in X-ray diffraction. Alloyed silver-platinum nanoparticles were almost fully amorphous by both methods, indicating a considerable internal disorder.

Inorganic nanoparticle-integrated mesenchymal stem cells: A potential biological agent for multifaceted applications

Mesenchymal stem cell (MSC)-based therapies are flourishing. MSCs could be used as potential therapeutic agents for regenerative medicine due to their own repair function. Meanwhile, the natural predisposition toward inflammation or injury sites makes them promising carriers for targeted drug delivery. Inorganic nanoparticles (INPs) are greatly favored for their unique properties and potential applications in biomedical fields. Current research has integrated INPs with MSCs to enhance their regenerative or antitumor functions. This model also allows the in vivo fate tracking of MSCs in multiple imaging modalities, as many INPs are also excellent contrast agents. Thus, INP-integrated MSCs would be a multifunctional biologic agent with great potential. In this review, the current roles performed by the integration of INPs with MSCs, including (i) enhancing their repair and regeneration capacity via the improvement of migration, survival, paracrine, or differentiation properties, (ii) empowering tumor-killing ability through agent loaded or hyperthermia, and (iii) conferring traceability are summarized. An introduction of INP-integrated MSCs for simultaneous treatment and tracking is also included. The promising applications of INP-integrated MSCs in future treatments are emphasized and the challenges to their clinical translation are discussed.

Metal Nanoparticles with Antimicrobial Properties: The Toxicity Response in Mouse Mesenchymal Stem Cells

Some metal nanoparticles (NP) are characterized by antimicrobial properties with the potential to be used as alternative antibiotics. However, NP may negatively impact human organism, including mesenchymal stem cells (MSC), a cell population contributing to tissue growth and regeneration. To address these issues, we investigated the toxic effects of selected NP (Ag, ZnO, and CuO) in mouse MSC. MSC were treated with various doses of NP for 4 h, 24 h, and 48 h and multiple endpoints were analyzed. Reactive oxygen species were generated after 48 h CuO NP exposure. Lipid peroxidation was induced after 4 h and 24 h treatment, regardless of NP and/or tested dose. DNA fragmentation and oxidation induced by Ag NP showed dose responses for all the periods. For other NP, the effects were observed for shorter exposure times. The impact on the frequency of micronuclei was weak. All the tested NP increased the sensitivity of MSC to apoptosis. The cell cycle was most affected after 24 h, particularly for Ag NP treatment. In summary, the tested NP induced numerous adverse changes in MSC. These results should be taken into consideration when planning the use of NP in medical applications where MSC are involved.

Inhibition of mycobacteria proliferation in macrophages by low cisplatin concentration through phosphorylated p53-related apoptosis pathway

BACKGROUND

Drug resistance is a prominent problem in the treatment of tuberculosis, so it is urgent to develop new anti- tuberculosis drugs. Here, we investigated the effects and mechanisms of cisplatin (DDP) on intracellular Mycobacterium smegmatis to tap the therapeutic potential of DDP in mycobacterial infection.

RESULTS

Macrophages infected with Mycobacterium smegmatis were treated with DDP alone or combined with isoniazid or rifampicin. The results showed that the bacterial count in macrophages decreased significantly after DDP (≤ 6 μg/mL) treatment. When isoniazid or rifampicin was combined with DDP, the number of intracellular mycobacteria was also significantly lower than that of isoniazid or rifampicin alone. Apoptosis of infected cells increased after 24 h of DDP treatment, as shown by flow cytometry and transmission electron microscopy detection. Transcriptome sequencing showed that there were 1161 upregulated and 645 downregulated differentially expressed genes (DEGs) between the control group and DDP treatment group. A Trp53-centered protein interaction network was found based on the top 100 significant DEGs through STRING and Cytoscape software. The expression of phosphorylated p53, Bax, JAK, p38 MAPK and PI3K increased after DDP treatment, as shown by Western blot analysis. Inhibitors of JAK, PI3K or p38 MAPK inhibited the increase in cell apoptosis and the reduction in the intracellular bacterial count induced by DDP. The p53 promoter Kevetrin hydrochloride scavenges intracellular mycobacteria. If combined with DDP, Kevetrin hydrochloride could increase the effect of DDP on the elimination of intracellular mycobacteria. In conclusion, DDP at low concentrations could activate the JAK, p38 MAPK and PI3K pathways in infected macrophages, promote the phosphorylation of p53 protein, and increase the ratio of Bax to Bcl-2, leading to cell apoptosis, thus eliminating intracellular bacteria and reducing the spread of mycobacteria.

CONCLUSION

DDP may be a new host-directed therapy for tuberculosis treatment, as well as the p53 promoter Kevetrin hydrochloride.

Phytochemical-Stabilized Platinum-Decorated Silver Nanocubes INHIBIT Adenocarcinoma Cells and Enhance Antioxidant Effects by Promoting Apoptosis via Cell Cycle Arrest

(1) Background: The increasing use of silver and platinum bimetallic nanoparticles in the diagnosis and treatment of cancer presents significant advances in biomedical applications due to their extraordinary physicochemical properties. This study investigated the role of aqueous phytochemical extract in stabilizing platinum nanodots-decorated silver nanocubes (w-Pt@AgNPs) for enhancing antioxidant activities and their mechanism. (2) Methods: UV-Vis, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) were used to characterize the formed w-Pt@AgNPs. LC-QToF-MS/MS was used to analyze the bioactive compounds, while DPPH, ABTS, and FRAP were used to detect the scavenging potential. Flow cytometric assays were performed to investigate the cytotoxicity and the mechanism of cell death. (3) Results: Morphological studies indicated that w-Pt@AgNPs were cube in shape, decorated by platinum nanodots on the surfaces. Compared to ethanolic extract-synthesized e-Pt@AgNPs, w-Pt@AgNPs exhibited the strongest antioxidant and cytotoxic activity, as data from Annexin V and Dead cell labeling indicated higher induction of apoptosis. Despite the high proportion of early apoptotic cells, the w-Pt@AgNPs triggered a decrease in G1/G0 cell cycle phase distribution, thereby initiating a G2/M arrest. (4) Conclusions: By enhancing the antioxidant properties and promoting apoptosis, w-Pt@AgNPs exhibited remarkable potential for improved cancer therapy outcomes.

Elemental (im-)miscibility determines phase formation of multinary nanoparticles co-sputtered in ionic liquids

Non-equilibrium synthesis methods allow the alloying of bulk-immiscible elements into multinary nanoparticles, which broadens the design space for new materials. Whereas sputtering onto solid substrates can combine immiscible elements into thin film solid solutions, this is not clear for sputtering of nanoparticles in ionic liquids. Thus, the suitability of sputtering in ionic liquids for producing nanoparticles of immiscible elements is investigated by co-sputtering the systems Au-Cu (miscible), Au-Ru and Cu-Ru (both immiscible), and Au-Cu-Ru on the surface of the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][(Tf)₂N]. The sputtered nanoparticles were analyzed to obtain (i) knowledge concerning the general formation process of nanoparticles when sputtering onto ionic liquid surfaces and (ii) information, if alloy nanoparticles of immiscible elements can be synthesized as well as (iii) evidence if the Hume-Rothery rules for solid solubility are valid for sputtered nanoparticles. Nanoparticle characteristics were found to depend on elemental miscibility: (1) nanoparticles from immiscible elemental combinations showed bigger mean diameters ranging from (3.3 ± 1.4) nm to (5.0 ± 1.7) nm in contrast to mean diameters of nanoparticles from elemental combinations with at least one miscible element pair ((1.7 ± 0.7) nm to (1.8 ± 0.6) nm). (2) Nanoparticles from immiscible combinations showed compositions with one element strongly dominating the ratio and very narrow differences between the highest and lowest fraction of the dominating element (Cu₉₄Ru₆ to Cu₁₀₀Ru₀; Au₉₆Ru₄ to Au₉₉Ru₁) in contrast to the other compositions (Au₆₄Cu₃₆ to Au₈₁Cu₁₉; Au₈₃Cu₁₃Ru₄/Au₇₅Cu₂₂Ru₃ to Au₈₇Cu₁₁Ru₂). Accompanying atomistic simulations using density-functional theory for clusters of different size and ordering confirm that the miscibility of Au-Cu and the immiscibility of Au-Ru and Cu-Ru govern the thermodynamic stability of the nanoparticles. Based on the matching experimental and theoretical results for the NP/IL-systems concerning NP stability, a formation model of multinary NPs in ILs was developed.

Bimetallic silver-platinum (AgPt) nanoparticles and chitosan fabricated cotton gauze for enhanced antimicrobial and wound healing applications

Wound healing is a significant clinical and socioeconomic problem that is often affected by microbial infection. Inappropriate monitoring leads to unfavorable concerns for surrounding tissues. Cotton gauzes have been used as low-cost wound dressing material but prolong healing owing to strong adherence and secondary microbial infections. Hence, we prepared the bimetallic (silver and platinum) nanoparticles (AgPt NPs) using citric acid (CA) as a reducing agent and then coated them on chitosan (CS) fabricated cotton gauze (CG) for enhanced antimicrobial and wound healing applications. The synthesis of AgPt NPs was evidenced UV-Visible spectroscopy, FE-TEM, and elemental mapping analysis. The average size of AgPt NPs was 21.48 ± 6.32 nm and spherical in structure. Besides, AgPt NPs showed a hydrodynamic size of 63.64 (d.nm) with a polydispersity index of 0.220 and a zeta potential of -28.1 mV. The FT-IR and XRD analysis demonstrated the functional changes and crystalline properties of AgPt NPs. The antimicrobial efficacy of AgPt NPs was significantly higher than standard antibiotic against bacteria, yeast, and filamentous fungi. Furthermore, the AgPt NPs-CS/CG exhibited a substantial hydrophobic nature with better antimicrobial and antioxidant activity. In addition, pH-dependent Ag and Pt release from the AgPt NPs-CS/CG was determined by ICP-MS analysis. The treatment of AgPt NPs-CS/CG augmented the in vitro wound healing in mouse embryonic fibroblast cells (NIH3T3). Hence, we concluded that AgPt NPs-CS/CG could be used to enhance antimicrobial and wound healing applications.

Formation of Catalytically Active Nanoparticles under Thermolysis of Silver Chloroplatinate(II) and Chloroplatinate(IV)

The thermal behaviour of Ag₂[PtCl₄] and Ag₂[PtCl₆] complex salts in inert and reducing atmospheres has been studied. The thermolysis of compounds in a helium atmosphere is shown to occur in two stages. At the first stage, the complexes decompose in the temperature range of 350–500 °C with the formation of platinum and silver chloride and the release of chlorine gas. At the second stage, silver chloride is sublimated in the temperature range of 700–900 °C, while metallic platinum remains in the solid phase. In contrast to the thermolysis of Ag₂[PtCl₆], the thermal decomposition of Ag₂[PtCl₄] at 350 °C is accompanied by significant heat release, which is associated with disproportionation of the initial salt to Ag₂[PtCl₆], silver chloride, and platinum metal. It is confirmed by DSC measurements, DFT calculations of a suggested reaction, and XRD. The thermolysis of Ag₂[PtCl₄] and Ag₂[PtCl₆] compounds is shown to occur in a hydrogen atmosphere in two poorly separable steps. The compounds are decomposed within 170–350 °C, and silver and platinum are reduced to a metallic state, while a metastable single-phase solid solution of Ag_0.67Pt_0.33 is formed. The catalytic activity of the resulting nanoalloy Ag_0.67Pt_0.33 is studied in the reaction of CO total (TOX) and preferential (PROX) oxidation. Ag_0.67Pt_0.33 enhanced Pt nano-powder activity in CO TOX, but was not selective in CO PROX.

Volatile Iridium and Platinum MOCVD Precursors: Chemistry, Thermal Properties, Materials and Prospects for Their Application in Medicine

Interest in iridium and platinum has been steadily encouraged due to such unique properties as exceptional chemical inertia and corrosion resistance, high biological compatibility, and mechanical strength, which are the basis for their application in medical practice. Metal-organic chemical vapor deposition (MOCVD) is a promising method to fabricate Ir and Pt nanomaterials, multilayers, and heterostructures. Its advantages include precise control of the material composition and microstructure in deposition processes at relatively low temperatures onto non-planar substrates. The development of MOCVD processes is inextricably linked with the development of the chemistry of volatile precursors, viz., specially designed coordination and organometallic compounds. This review describes the synthesis methods of various iridium and platinum precursors, their thermal properties, and examples of the use of MOCVD, including formation of films for medical application and bimetallics. Although metal acetylacetonates are currently the most widely used precursors, the recently developed heteroligand Ir(I) and Pt(IV) complexes appear to be more promising in both synthetic and thermochemical aspects. Their main advantage is their ability to control thermal properties by modifying several types of ligands, making them tunable to deposit films onto different types of materials and to select a combination of compatible compounds for obtaining the bimetallic materials.

In vitro evaluation of electrochemically bioactivated Ti6Al4V 3D porous scaffolds

Triply periodic minimal surfaces (TPMS) are known for their advanced mechanical properties and are wrinkle-free with a smooth local topology. These surfaces provide suitable conditions for cell attachment and proliferation. In this study, the in vitro osteoinductive and antibacterial properties of scaffolds with different minimal pore diameters and architectures were investigated. For the first time, scaffolds with TPMS architecture were treated electrochemically by plasma electrolytic oxidation (PEO) with and without silver nanoparticles (AgNPs) to enhance the surface bioactivity. It was found that the scaffold architecture had a greater impact on the osteoblast cell activity than the pore size. Through control of the architecture type, the collagen production by osteoblast cells increased by 18.9% and by 43.0% in the case of additional surface PEO bioactivation. The manufactured scaffolds demonstrated an extremely low quasi-elastic modulus (comparable with trabecular and cortical bone), which was 5-10 times lower than that of bulk titanium (6.4-11.4 GPa vs 100-105 GPa). The AgNPs provided antibacterial properties against both gram-positive and gram-negative bacteria and had no significant impact on the osteoblast cell growth. Complex experimental results show the in vitro effectiveness of the PEO-modified TPMS architecture, which could positively impact the clinical applications of porous bioactive implants.

Osteogenic effects of the bioactive small molecules and minerals in the scaffold-based bone tissue engineering

Reconstruction of the damaged bone is a striking challenge in the medical field. The bone grafts as a current treatment is associated with inherent limitations; hence, the bone tissue engineering as an alternative therapeutic approach has been considered in the recent decades. Bone tissue engineering aims at replacing the lost tissue and restoring its function by recapitulating the natural regeneration process. Concerted participation and combination of the biocompatible materials, osteoprogenitor/ stem cells and bioactive factors closely mimic the bone microenvironment. The bioactive factors regulate the cell behavior and they induce the stem cells to osteogenic differentiation by activating specific signaling cascades. Growth factors (GFs) are the most important bioactive molecules and mediators of the natural bone repair process. Although these soluble factors have approved applications in the bone regeneration, however, there are several limitations such as the instability, high dose requirements, and serious side effects which could restrict their clinical usage. Alternatively, a new generation of bioactive molecules with the osteogenic properties are used. The non-peptide organic or inorganic molecules are physiologically stable and non-immunogenic due to their small size. Many of them are obtained from the natural resources and some are synthesized through the chemical methods. As a result, these molecules have been introduced as the cost-effective osteogenic agents in the bone tissue regeneration. In this paper, three groups of these bioactive agents including the organic small molecules, minerals and metallic nanoparticles have been investigated, considering their function in accelerating the bone regeneration. We review the recent in vitro and in vivo studies that utilized the osteogenic molecules to promote the bone formation in the scaffold-based bone tissue engineering systems.

Therapeutic nanodendrites: current applications and prospects

Multidisciplinary efforts in the field of nanomedicine for cancer therapy to provide solutions to common limitations of traditional drug administration such as poor bioaccumulation, hydrophobicity, and nonspecific biodistribution and targeting have registered very promising progress thus far. Currently, a new class of metal nanostructures possessing a unique dendritic-shaped morphology has been designed for improved therapeutic efficiency. Branched metal nanoparticles or metal nanodendrites are credited to present promising characteristics for biomedical applications owing to their unique physicochemical, optical, and electronic properties. Nanodendrites can enhance the loading efficiency of bioactive molecules due to their three-dimensional (3D) high surface area and can selectively deliver their cargo to tumor cells using their stimuli-responsive properties. With the ability to accumulate sufficiently within cells, nanodendrites can overcome the detection and clearance by glycoproteins. Moreover, active targeting ligands such as antibodies and proteins can as well be attached to these therapeutic nanodendrites to enhance specific tumor targeting, thereby presenting a multifunctional nanoplatform with tunable strategies. This mini-review focuses on recent developments in the understanding of metallic nanodendrite synthesis, formation mechanism, and their therapeutic capabilities for next-generation cancer therapy. Finally, the challenges and future opportunities of these fascinating materials to facilitate extensive research endeavors towards the design and application were discussed.

Antimicrobial efficacy of platinum-doped silver nanoparticles

Silver nanoparticles (AgNPs) have been proposed to combat oral infection due to their efficient ionic silver (Ag+ ) release. However, concentrations required for antimicrobial efficacy may not be therapeutically viable. In this work, platinum-doped silver nanoparticles (Pt-AgNPs) were explored to evaluate their potential for enhanced Ag+ release, which could lead to enhanced antimicrobial efficacy against S. aureus, P. aeruginosa, and E. coli. AgNPs doped with 0.5, 1, and 2 mol% platinum (Pt0.5 -AgNPs, Pt1 -AgNPs, and Pt2 -AgNPs) were synthesized by a chemical reduction method. Transmission electron microscopy revealed mixed morphologies of spherical, oval, and ribbon-like nanostructures. Surface-enhanced Raman scattering revealed that the surface of Pt-AgNPs was covered with up to 93% Pt. The amount of Ag+ released increased 16.3-fold for Pt2 -AgNPs, compared to AgNPs. The initial lag phase in bacterial growth curve was prolonged for Pt-AgNPs. This is consistent with a Ag+ release profile that exhibited an initial burst followed by sustained release. Doping AgNPs with platinum significantly increased the antimicrobial efficacy against all species. Pt2 -AgNPs exhibited the lowest minimum inhibitory concentrations, followed by Pt1 -AgNPs, Pt0.5 -AgNPs, and AgNPs, respectively. Doping AgNPs with a small amount of platinum promoted the release of Ag+ , based on the sacrificial anodic effect, and subsequently enhanced their antimicrobial efficacy.

Ligand-free upconversion nanoparticles for cell labeling and their effects on stem cell differentiation

Recently, the wide application of upconversion nanoparticles (UCNPs) in the field of bioimaging has raised the requirement of biocompatibility. Current cytocompatibility studies on UCNPs mainly focus on cancer cells; however, their potential effects on normal cells are rarely addressed. Herein, the cellular effects of a trace amount of ligand-free NaYF₄:Yb/Er nanocrystals on the differentiation of rat bone mesenchymal stem cells (rBMSCs) were investigated. First, due to their excellent upconversion fluorescent properties, the cellular uptake of ligand-free NaYF₄:Yb/Er nanocrystals was confirmed by confocal laser scanning microscopy, and a homogeneous cytoplasmic distribution was imaged. Second, the viability of the rBMSCs cultured with a series of concentrations of nanoparticles (0, 30, 300, and 3000 ng ml^-1) was evaluated, and a dose threshold was determined. Third, the effects of ligand-free NaYF₄:Yb/Er nanocrystals on the osteogenesis of the rBMSCs were intensively characterized. The alkaline phosphatase activity assay, quantitative real time polymerase chain reaction for related osteogenic genes, and immunofluorescence staining of specific biomarkers and mineral deposits demonstrated that the ligand-free NaYF₄:Yb/Er nanocrystals at a proper concentration can enhance osteogenic differentiation. Finally, intracytoplasmic lipid detection showed that the adipogenic differentiation of rBMSCs might be inhibited in the presence of ligand-free NaYF₄:Yb/Er nanocrystals. Meanwhile, these results showed that the effects of ligand-free NaYF₄:Yb/Er nanocrystals on rBMSCs were concentration-dependent and reciprocal between osteogenic and adipogenic differentiation. This work provides new insights into the exploring the biocompatibility of UCNPs and will benefit the research community engaged in nanotechnology and biomedicine.

Enhanced dissolution of silver nanoparticles in a physical mixture with platinum nanoparticles based on the sacrificial anode effect

A strategy to reduce implant-related infections is the inhibition of the initial bacterial implant colonization by biomaterials containing silver (Ag). The antimicrobial efficacy of such biomaterials can be increased by surface enhancement (nanosilver) or by creating a sacrificial anode system for Ag. Such a system will lead to an electrochemically driven enhanced Ag ion release due to the presence of a more noble metal. Here we combined the enlarged surface of nanoparticles (NP) with a possible sacrificial anode effect for Ag induced by the presence of the electrochemically more noble platinum (Pt) in physical mixtures of Ag NP and Pt NP dispersions. These Ag NP/Pt NP mixtures were compared to the same amounts of pure Ag NP in terms of cell biological responses, i.e. the antimicrobial activity against Staphylococcus aureus and Escherichia coli as well as the viability of human mesenchymal stem cells (hMSC). In addition, Ag NP was analyzed by ultraviolet-visible (UV-vis) spectroscopy, cyclic voltammetry, and atomic absorption spectroscopy. It was found that the dissolution rate of Ag NP was enhanced in the presence of Pt NP within the physical mixture compared to a dispersion of pure Ag NP. Dissolution experiments revealed a fourfold increased Ag ion release from physical mixtures due to enhanced electrochemical activity, which resulted in a significantly increased toxicity towards both bacteria and hMSC. Thus, our results provide evidence for an underlying sacrificial anode mechanism induced by the presence of Pt NP within physical mixtures with Ag NP. Such physical mixtures have a high potential for various applications, for example as antimicrobial implant coatings in the biomedicine or as bactericidal systems for water and surface purification in the technical area.

Combinatorial Synthesis of Binary Nanoparticles in Ionic Liquids by Cosputtering and Mixing of Elemental Nanoparticles

Binary alloy nanoparticles were fabricated by two combinatorial methods: (I) cosputtering from elemental targets into the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [Bmim][(Tf)₂N] and (II) by mixing elemental nanoparticles after sputtering them separately into [Bmim][(Tf)₂N]. Both methods lead to the formation of Au-Cu nanoparticles (2.3 nm for cosputtered, 3.6 nm for mixed), however with different resulting compositions: cosputtered nanoparticles show a composition range of Au_80-90Cu_20-10; mixing of Au- and Cu-loaded ionic liquids leads to the formation of Au₇₅Cu₂₅ nanoparticles. Annealing the binary nanoparticles at 100 °C shows that the mixed nanoparticles grow to sizes of 4.1 nm, whereas the cosputtered nanoparticles grow only to 3 nm.