Navegando por Assunto "Nanoparticles"

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    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 Campos
    Surface-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.
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    Zinc phthalocyanine tetrasulfonate-loaded polyelectrolytic PLGA nanoparticles for photodynamic therapy applications
    (Elsevier) Toledo, Maria Cristina Modesto Clementino de; Abreu, Alexandro da Silva; Carvalho, Janicy Arantes; Ambrósio, Jéssica Aparecida Ribeiro; Godoy, Daniele da Silva; Pinto, Bruna Cristina dos Santos; Beltrame Junior, Milton; Simioni, Andreza Ribeiro
    Background: Photodynamic Therapy (PDT) is a modality for the treatment of neoplastic tissues, which is based on the administration of a phototherapeutic agent and light irradiation at an appropriate wavelength, aiming to locate and destroy the target cell with the formation of reactive oxygen species. Nanoencapsulation technology presents itself as a tool for incorporation of bioactive substances aiming to improve their solubility in physiological environment, obtain a longer circulation time in the organism, administration of lower dosages and the minimization of side effects. The present work aimed at the development of poly (lactic acid-glycolic acid) (PLGA) nanoparticles coated with polyelectrolyte film layers for encapsulating zinc phthalocyanine tetrasulfonated (ZnPcSO4) as a bioactive substance model. Methods: PLGA nanoparticles were produced by the double emulsion/solvent evaporation technique and polyelectrolytic coating was performed using polyalkylamine hydrochloride (PAH) as a weak polycation and poly (4- styrene sulfonate) (PSS) as a strong polyanion by layer-by-layer self-assembly technique (known as layer-by-layer-LbL). The nanoparticulate system was studied by scanning electron microscopy, steady-state, and their biological activity was evaluated using in vitro cancer cell lines by classical MTT assay. Results: The polyelectrolytic PLGA nanoparticles had an average diameter of 384.7 ± 138.6 nm, restricted distribution size with a polydispersity index. The obvious change in zeta potential indicates successful alternation in polycation (PAH) and polyanion (PSS) deposition directly in PLGA nanoparticles. Scanning electron microscopy (SEM) analysis showed that the formed system had morphology spherical, typical of these release systems. The loading efficiency was 82.1 % ± 1.2 %. The polyelectrolytic nanoparticles loaded with phthalocyanine maintained their photophysical behavior after encapsulation. Cell viability was determined, obtaining 90 % cell death. Conclusions: Therefore, the presented work depicts ZnPcSO4-loaded polyelectrolytic PLGA nanoparticles as a promise drug delivery system for phototherapeutic agent, which are thus expected to have superior therapeutic efficiency than free drug.