Enabling high-quality transparent conductive oxide on 3D printed ZrO2 architectures through atomic layer deposition

The conformal atomic layer deposition of a transparent conductive oxide composed of Al-doped ZnO (AZO) over three-dimensional (3D) shaped ZrO2 microarchitectures produced using two-photon lithography (TPL) is reported here for the first time. The effect of ZrO2 morphology, surface roughness, and crystallographic phase (tetragonal and monoclinic) on the quality and properties of the deposited ZnO and AZO thin films is investigated. No discontinuities, domains, or areas differing from the desired chemical composition have been found in films grown over the 3D structures. Three different Al dopant concentrations (4.0 %, 4-5 %, and 5.0 % Al doping cycles) are examined and compared to undoped ZnO. AZO and ZnO optical and electrical properties are studied using cathodoluminescence (CL) and Hall effect measurements. The CL study confirms that the observed emissions from the ZnO and AZO films are associated with the near band emission of ZnO and defects, i.e., zinc and oxygen vacancies and interstitial oxygen. The AZO films exhibit n-type semiconductor behavior, and a minimum resistivity of 1.2 x 10-3 Ω cm is achieved. From a broad perspective, AZO deposition on 3D microarchitectures opens a new route towards dimensionally refined optoelectronic devices in which the ZrO2/AZO can serve a key enabling role for the production of electrodes

Nanomaterials to aid wound healing and infection control

The management and treatment of infectious bacterial diseases in wound healing have both become significant research areas in the biomedical field. While current treatments show limitations related to toxicity and exposure time, nanotechnology has become a potential alternative to overcome such challenges. The application of different nanomaterials, with a wide range of elemental compositions, morphologies, and features, has become an essential tool in managing wound healing infections. This book chapter shows an updated view of the newest trends in the control and treatment of bacterial proliferation in the wound bed by utilizing various metal- and nonmetal-based nanostructures

Composition-Dependent Cytotoxic and Antibacterial Activity of Biopolymer-Capped Ag/Au Bimetallic Nanoparticles against Melanoma and Multidrug-Resistant Pathogens

Nanostructured silver (Ag) and gold (Au) are widely known to be potent biocidal and cytotoxic agents as well as biocompatible nanomaterials. It has been recently reported that combining both metals in a specific chemical composition causes a significant enhancement in their antibacterial activity against antibiotic-resistant bacterial strains, as well as in their anticancer effects, while preserving cytocompatibility properties. In this work, Ag/Au bimetallic nanoparticles over a complete atomic chemical composition range were prepared at 10 at% through a green, highly reproducible, and simple approach using starch as a unique reducing and capping agent. The noble metal nanosystems were thoroughly characterized by different analytical techniques, including UV-visible and FT-IR spectroscopies, XRD, TEM/EDS, XPS and ICP-MS. Moreover, absorption spectra simulations for representative colloidal Ag/Au-NP samples were conducted using FDTD modelling. The antibacterial properties of the bimetallic nanoparticles were determined against multidrug-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus, showing a clear dose-dependent inhibition even at the lowest concentration tested (5 µg/mL). Cytocompatibility assays showed a medium range of toxicity at low and intermediate concentrations (5 and 10 µg/mL), while triggering an anticancer behavior, even at the lowest concentration tested, in a process involving reactive oxygen species production per the nanoparticle Au:Ag ratio. In this manner, this study provides promising evidence that the presently fabricated Ag/Au-NPs should be further studied for a wide range of antibacterial and anticancer applications.The groups at CSIC and Tecnologico de Monterrey acknowledge the i-Link+2019 program (ref. LINKB20024 “NANOBIO-ROJA”) for financial support. AM acknowledges the Spanish Ministry of Science (RYC2018-024561-I), the regional government of Aragon (E13_20R), the European Union’s Horizon 2020 research and innovation programme (823717– ESTEEM3) and the National Natural Science Foundation of China (NSFC- 21835002).Peer reviewe

Nickel-Based Electrocatalysts for Water Electrolysis

Currently, hydrogen production is based on the reforming process, leading to the emission of pollutants; therefore, a substitute production method is imminently required. Water electrolysis is an ideal alternative for large-scale hydrogen production, as it does not produce any carbon-based pollutant byproducts. The production of green hydrogen from water electrolysis using intermittent sources (e.g., solar and eolic sources) would facilitate clean energy storage. However, the electrocatalysts currently required for water electrolysis are noble metals, making this potential option expensive and inaccessible for industrial applications. Therefore, there is a need to develop electrocatalysts based on earth-abundant and low-cost metals. Nickel-based electrocatalysts are a fitting alternative because they are economically accessible. Extensive research has focused on developing nickel-based electrocatalysts for hydrogen and oxygen evolution. Theoretical and experimental work have addressed the elucidation of these electrochemical processes and the role of heteroatoms, structure, and morphology. Even though some works tend to be contradictory, they have lit up the path for the development of efficient nickel-based electrocatalysts. For these reasons, a review of recent progress is presented herein

Green Synthesis of a Synergetic Structure of Tellurium Nanowires and Metallic Nanoparticles for Biomedical Applications

Trabajo presentado en el AIChE Annual Meeting (2019), celebrado en Orlando, Florida (Estado Unidos), del 10 al 15 de noviembre de 2019Statement of Purpose: Health care system is facing significant concerns nowadays such as antimicrobial resistance and cancer. New approaches should be considered, and nanotechnology has been found as a powerful solution to them. Current synthetic methodologies for production of nanoparticles, based on physicochemical standards are known to be easy-to-get straightforward. Nevertheless, there is a cost associated with the limitations that should be overcome from these approaches, such as the production of toxic by-products or the lack of biocompatibility of the products. Therefore, new methods are needed, and green chemistry offers itself as a suitable and novel answer, achieving a safe and environmentally-friendly design, manufacture and use of chemical products. In this research, tellurium nanowires were synthesized using a green synthesis methodology (TeNWs). They were characterized in terms of structure and composition and tested for anticancer, antibacterial and cytotoxicity properties. Then, TeNWs were used for the synthesis of metallic nanoparticles in an easy and straightforward method with no need of reducing agent that was completed within 1 minute of reaction. Nanoparticles were characterized, and the synthetic process was compared with the ones described in literature, with the aim to compare the methods in terms of chemical needed, reaction conditions and economic implications. Methods: Tellurium nanowires were prepared using a hydrothermal reaction. The environmentally-friendly approach led to the use of telluric acid and starch as a unique reducing agent. Once purified, tellurium nanowires were used as a template for the growth of metallic nanoparticles (such as platinum and palladium) in a quick method with no need of additional reducing agent at room temperature. The structure containing both metallic nanoparticles and nanowires was known as synergy. Besides, biocompatibility and anticancer tests of both structures – the synergy and the nanowires - with human tissue were accomplished, growing human dermal fibroblast (HDF) cells and melanoma cells in media in the presence of both nanosystems. After an incubation time of 5 days, the cell growth was analyzed using MTS assay. Furthermore, antibacterial properties were tested against Escherichia Coli and Staphyloccocus Aureus. Results: It was demonstrated that green synthesized tellurium nanowires can be used as a template for the growth of metallic nanoparticles in a quick reaction that takes places in 1 minute, at room temperature with no need of stirring and reducing agent. TEM images of both tellurium nanowires and metallic nanoparticles were taken (Fig.1), showing nanoparticles with a constant distribution size attached to the tellurium nanowires, which were quickly released from the structure. The chemistry of the samples was confirmed using EDX analysis, showing the distinct peaks of tellurium and the ones corresponding to each one of the metals. In vitro cytotoxicity assays were performed with human dermal fibroblasts (HDF) cells. The experiments showed that the use of green nanostructures, enhanced the growth of the cells in comparison with the control. Furthermore, anticancer and antimicrobial studies showed an improved performance of the synergetic structure compared to the bare nanowires structures, causing a higher depletion of cell viability. Conclusions: Current and main methods to synthesize nanostructures, both nanowires and nanoparticles, use approaches which employ chemical methods. The weakness of these procedures (extreme reaction conditions, production of toxic byproducts…) calls for a necessity of alternative approaches. Green chemistry can be used to overcome these drawbacks. Here, green-synthesized tellurium nanowires were compared with chemically-synthesized structures to show that the first ones have an enhanced biocompatibility and anticancer properties over the ones synthesized using traditional methods. Besides, it was demonstrated that tellurium nanowires synthesized using starch can be used for the controllable and quick growth of metallic nanoparticles

Nickel-Based Electrocatalysts for Water Electrolysis

Currently, hydrogen production is based on the reforming process, leading to the emission of pollutants; therefore, a substitute production method is imminently required. Water electrolysis is an ideal alternative for large-scale hydrogen production, as it does not produce any carbon-based pollutant byproducts. The production of green hydrogen from water electrolysis using intermittent sources (e.g., solar and eolic sources) would facilitate clean energy storage. However, the electrocatalysts currently required for water electrolysis are noble metals, making this potential option expensive and inaccessible for industrial applications. Therefore, there is a need to develop electrocatalysts based on earth-abundant and low-cost metals. Nickel-based electrocatalysts are a fitting alternative because they are economically accessible. Extensive research has focused on developing nickel-based electrocatalysts for hydrogen and oxygen evolution. Theoretical and experimental work have addressed the elucidation of these electrochemical processes and the role of heteroatoms, structure, and morphology. Even though some works tend to be contradictory, they have lit up the path for the development of efficient nickel-based electrocatalysts. For these reasons, a review of recent progress is presented herein

Aloe Vera-Mediated Green Synthesis of Tellurium Nanostructures with Both Antimicrobial and Anticancer Activity

Trabajo presentado en el AIChE Annual Meeting (2019), celebrado en Orlando, Florida (Estado Unidos), del 10 al 15 de noviembre de 2019Antimicrobial resistance to antibiotics is a huge concern that presents significant challenges to modern healthcare. Thus, an alternative solution that does not require the use of antibiotics is needed. One of the most promising methodologies comes from the implementation of nanotechnology. Unlike antibiotics, bacteria are unable to develop resistance to nanoparticles. Many methods for synthesis of various types of nanostructures have been reported. Nevertheless, they are often accompanied by significant drawbacks such as cost, harsh processing conditions, and production of toxic by-products that are a concern for both the environment and society. In this work, an environmentally-friendly and cost-effective approach for synthesis of tellurium nanorods in aqueous media have been developed using aloe vera extract as a unique reducing agent. Nanorods were characterized using Transmission Electron Microscopy and Energy-Dispersive X-Ray Spectroscopy to determine size, morphology and composition. Resulting nanoparticles with a length 100±19 nm and width of 5±2 were produced. Nanoparticles were also characterized and tested for their ability to inhibit bacterial growth. A decay in bacterial growth after 24 hours was achieved for both Staphylococcus aureus and Escherichia coli at tellurium nanoparticle concentrations from 5 to 75 µg/mL. Biocompatibility assays were also performed, and the nanoparticles showed no cytotoxic effects for human dermal fibroblast cells after 48 hours. Anticancer properties were tested as well, and results indicated that the nanoparticles (in concentrations ranging from 5 to 75 µg/mL) were able to delay cancer cell proliferation. Aloe vera extracts afforded synthesis of tellurium nanoparticles in a quick, cost-effective and completely green approach that showed both antimicrobial and anticancer effects with low cytotoxicity for healthy cells

In Situ Generation of Metal-Oxide Nanoparticles on Top of a Green- Synthesized Tellurium Nanowire Template and the Biomedical Study of the Synergetic Structure

Trabajo presentado en el AIChE Annual Meeting, celebrado de forma virtual del 16 al 20 de noviembre de 2020Two of the major concerns that the healthcare system is facing nowadays are cancer and antimicrobial resistance (AMR) to antibiotics. Nanotechnology appears as a suitable solution, which might overcome some limitations of current available treatments. Despite of the advances in the nanoscale, there is a need to find alternatives to the traditional synthesis of nanomaterials, which suppose a threat to both the environment and society. In this context, Green Nanotechnology is presented as an answer, with cost-effective and environmentally-friendly approaches for nanoparticles synthesis. In the present work, starch-mediated Tellurium nanowires were employed as a template for the in-situ growth of palladium and platinum nanostructures. The noble metal-chalcogenide nanocomposites were characterized for their biomedical applications, with both green-mediated synergetic composites showing antibacterial activity against AMR bacterial strains, both Gram negative (MDR Escherichia coli) and positive (Methicillin resistant Staphylococcus aureus) bacteria, at concentrations from 10 to 100 µg/mL over a 24-hour time period. Moreover, cell studies were done with human dermal fibroblast (HDF) and melanoma cells for 5 days, showing no significant cytotoxic effect at concentrations up to 25 µg/mL, while triggering a dose-dependent anticancer effect in the same rage of concentrations. Therefore, the use of noble metalchalcogenide nanocomposites is proposed as a novel green nanotechnologicalbased platform for biomedical applications

Comparison of cytocompatibility and anticancer properties of traditional and green chemistry-synthesized tellurium nanowires

[Background] Tradiditional physicochemical approaches for the synthesis of compounds, drugs, and nanostructures developed as potential solutions for antimicrobial resistance or against cancer treatment are, for the most part, facile and straightforward. Nevertheless, these approaches have several limitations, such as the use of toxic chemicals and production of toxic by-products with limited biocompatibility. Therefore, new methods are needed to address these limitations, and green chemistry offers a suitable and novel answer, with the safe and environmentally friendly design, manufacturing, and use of minimally toxic chemicals. Green chemistry approaches are especially useful for the generation of metallic nanoparticles or nanometric structures that can effectively and efficiently address health care concerns.[Objective] Here, tellurium (Te) nanowires were synthesized using a novel green chemistry approach, and their structures and cytocompatibility were evaluated.[Method] An easy and straightforward hydrothermal method was employed, and the Te nanowires were characterized using transmission electron microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, and optical microscopy for morphology, size, and chemistry. Cytotoxicity tests were performed with human dermal fibroblasts and human melanoma cells (to assess anticancer properties). The results showed that a treatment with Te nanowires at concentrations between 5 and 100 µg/mL improved the proliferation of healthy cells and decreased cancerous cell growth over a 5-day period. Most importantly, the green chemistry -synthesized Te nanowires outperformed those produced by traditional synthetic chemical methods.[Conclusion] This study suggests that green chemistry approaches for producing Te nanostructures may not only reduce adverse environmental effects resulting from traditional synthetic chemistry methods, but also be more effective in numerous health care applications.Dr María Ujué González reports grants from MINECO, MINECO + EU, and the Government of Autonomous Region of Madrid, CM, during the conduct of the study. Dr Yves Huttel reports grants from MINECO during the conduct of the study. Dr José Miguel García-Martín reports grants from MINECO, MECD, and Fulbright Commission, during the conduct of the study.Peer reviewe

Starch-mediated synthesis of mono- and bimetallic silver/gold nanoparticles as antimicrobial and anticancer agents

Background and aim: Bimetallic silver/gold nanosystems are expected to significantly improve therapeutic efficacy compared to their monometallic counterparts by maintaining the general biocompatibility of gold nanoparticles (AuNPs) while, at the same time, decreasing the relatively high toxicity of silver nanoparticles (AgNPs) toward healthy human cells. Thus, the aim of this research was to establish a highly reproducible one-pot green synthesis of colloidal AuNPs and bimetallic Ag/Au alloy nanoparticles (NPs; Ag/AuNPs) using starch as reducing and capping agent. Methods: The optical properties, high reproducibility, stability and particle size distribution of the colloidal NPs were analyzed by ultraviolet (UV)–visible spectroscopy, dynamic light scattering (DLS) and ζ-potential. The presence of starch as capping agent was determined by Fourier transform infrared (FT-IR) spectroscopy. The structural properties were studied by X-ray diffraction (XRD). Transmission electron microscopy (TEM) imaging was done to determine the morphology and size of the nanostructures. The chemical composition of the nanomaterials was determined by energy-dispersive X-ray spectroscopy (EDS) and inductively coupled plasma mass spectrometry (ICP-MS) analysis. To further study the biomedical applications of the synthesized nanostructures, antibacterial studies against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA) were conducted. In addition, the NPs were added to the growth media of human dermal fibroblast (HDF) and human melanoma cells to show their cytocompatibility and cytotoxicity, respectively, over a 3-day experiment. Results: UV–visible spectroscopy confirmed the highly reproducible green synthesis of colloidal AuNPs and Ag/AuNPs. The NPs showed a face-centered cubic crystal structure and an icosahedral shape with mean particle sizes of 28.5 and 9.7 nm for AuNPs and Ag/AuNPs, respectively. The antibacterial studies of the NPs against antibiotic-resistant bacterial strains presented a dose-dependent antimicrobial behavior. Furthermore, the NPs showed cytocompatibility towards HDF, but a dose-dependent anticancer effect was found when human melanoma cells were grown in presence of different NP concentrations for 72 hours. Conclusion: In this study, mono- and bimetallic NPs were synthesized for the first time using a highly reproducible, environmentally friendly, cost-effective and quick method and were successfully characterized and tested for several anti-infection and anticancer biomedical applications