Navegando por Assunto "Silver nanoparticles"
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Item Antibacterial activity of silver nanoparticles functionalized with amikacin applied against multidrug-resistant acinetobacter baumannii(Elsevier) Camargo, Larissa de Oliveira; Fontoura, Inglid; Veriato, Thaís da Silva; Raniero, Leandro José; Castilho, Maiara LimaBackground: Multidrug-resistant bacteria are one of the world's biggest health problems; therefore, improving the spectrum of action of antibiotics could be necessary to reverse this situation. Amikacin and silver salts have well-known antimicrobial properties. However, both drugs lost their effectiveness against some bacteria, such as Acinetobacter baumannii. This work aims to develop a nanodrug from silver nanoparticles (AgNPs) functionalized with Amikacin against multidrug-resistant Acinetobacter baumannii. Methods: AgNPs were produced using the bottom-up methodology and functionalized with Amikacin modified by the carbodiimide-based chemistry, forming AgNPs@Amikacin. Susceptibility tests were performed using Amikacin-resistant Acinetobacter baumannii strains to assess the bacteriostatic and bactericidal potential of the developed nanodrug. The clinical strains were induced to form a biofilm, and biomass quantification and the metabolic activity were determined. Results: The AgNPs have a hydrodynamic diameter of the particles with a bimodal distribution, with a size of 37.84 nm. The FT-IR spectrum of AgNPs@Amikacin exhibits vibrational modes corresponding to Amikacin, confirming the conjugation to AgNPs. Susceptibility testing demonstrated a minimal inhibitory and bactericidal concentration of < 0.5 µg/mL. The AgNPs@Amikacin reduced the biofilm metabolic activity of Acinetobacter baumannii at rates ≥ 50%, characterized by the minimal biofilm inhibition concentrations. Conclusions: Results demonstrate a promising development of a new nanodrug with lower concentrations, less toxicity, and greater efficacy against multidrug-resistant Acinetobacter baumannii.Item Study of SERS-Active substrates for low-concentration detection(2023-08-31) Raniero, Leandro José; Dors Junior, Oli Luiz; Oliveira Filho, Irapuan Rodrigues de; Herreño Fierro, Cesar Aurelio; Espírito Santo, Ana Maria do; Murcia Correa, Luz Stefany; São José dos CamposSurface-enhanced Raman scattering (SERS) is a highly efficient technique due to its ability to detect several analytes at low concentrations, such as proteins, pesticides, heavy metals, environmental monitoring, food safety, biochemical sensing, and others. One of the most critical applications of SERS detection is herbicides. Glyphosate (GLP) is the herbicide with the highest global commercialization, and historical use (NOVOTNY, 2022; MARTINS-GOMES et al., 2022). Even though numerous studies have found the substance harmless, current research demonstrates that GLP might affect human health (RIVAS-GARCIA et al., 2022). For this reason, researchers are concentrating on alterna- tives for analytical quantification, such as SERS. In this work, DVD-R@AgNPs and PSi@AgNPs SERS-actives substrates were produced by the Cathodic Cage Plasma Deposition (CCPD) technique, which allowed a thin film layer deposition of silver nanoparticles (AgNPs) on the polycarbonate (PC) grating structure from Digital Video/Versatile Disc Recordable (DVD-R) and on the porous silicon (PSi) structure. Scanning Electron Microscopy with energy-dispersive X-ray spectroscopy was used to characterize the substrates and chemical changes on the surfaces after AgNPs de- position. DVD-R@AgNPs and PSi@AgNPs substrates were used to detect standard crystal violet (CV), standard GLP, and RoundupTM GLP (GLP-RU) using Raman Spectroscopy measurements. The CV was used as a control dye molecule to calculate the enhance- ment factors, which value was in the order of ~105 for both substrates. To evaluate the efficiency of the SERS substrates, the analytes limit of detection was calculated. For DVD-R@AgNPs, the lowest concentration detected was ~10-10 M for CV, 10-7 and 10-8 M for GLP and 10-6 M for GLP-RU. While for PSi@AgNPs, ~10-12 M for CV and 10-2 M for GLP-RU were the lowest concentrations obtained. Despite this value, PSi@AgNPs is a good SERS platform for AgNPs deposition, via CCPD, and it needs to enhance the sensitivity for herbicide traces detection as GLP-RU. Accordingly, the DVD-R@AgNPs SERS sensor is a low-cost and promising substrate that analyzes traces of commercial GLP, demonstrating high SERS sensitivities.Item Tribocorrosion studies on DLC films with silver nanoparticles for prosthesis applications(IOP Publishing) Radi, Polyana Alves; Vieira, Lúcia; Leite, Priscila Maria Sarmeiro Corrêa Marciano; Trava-Airoldi, Vladimir Jesus; Massi, Marcos; Reis, Danieli Aparecida PereiraMetals and their alloys are very important for orthopedic applications, and the basic requirements for a successful implant are chemical stability, mechanical behavior, and biocompatibility in body fluids and tissues. For prosthesis applications, the corrosion resistance of metals is one of the major prerequisites to avoid impairment of the material properties due to degradation. The combined action of corrosion and wear on the material is called tribocorrosion and DLC (Diamond-Like Carbon) films have been extensively studied to increase prosthesis biocompatibility and to protect from corrosion. Additionally, DLC coatings can prevent the prosthesis to release toxic elements due to plastic deformation and corrosion. This paper is about tribocorrosion studies on DLC and DLC-Ag (DLC containing silver nanoparticles) on Ti-6Al-4V substrates. These films were obtained by PECVD (Plasma Enhanced Chemical Vapor Deposition) using hexane as a precursor. The tribocorrosion behavior of uncoated and coated samples was investigated in the reciprocating mode in Ringer's lactate solution. From the polarization test results, the protective efficiency of the film was calculated. Silver nanoparticles improved the corrosion resistance of the films. The protective efficiency was 15 and 19% for DLC and DLC-Ag films, respectively.