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Adenosine-Monophosphate-Assisted Homogeneous Silica Coating of Silver Nanoparticles in High Yield
Publication . Fernández-Lodeiro, Carlos; Tambosi, Reem; Fernández-Lodeiro, Javier; Fernández-Lodeiro, Adrián; Nuti, Silvia; Ouchane, Soufian; Kébaïli, Nouari; Pérez-Juste, Jorge; Pastoriza-Santos, Isabel; Lodeiro, Carlos; DQ - Departamento de Química; LAQV@REQUIMTE; MDPI AG
In this study, we propose a novel approach for the silica coating of silver nanoparticles based on surface modification with adenosine monophosphate (AMP). Upon AMP stabilization, the nanoparticles can be transferred into 2-propanol, promoting the growth of silica on the particle surfaces through the standard Stöber process. The obtained silica shells are uniform and homogeneous, and the method allows a high degree of control over shell thickness while minimizing the presence of uncoated NPs or the negligible presence of core-free silica NPs. In addition, AMP-functionalized AgNPs could be also coated with a mesoporous silica shell using cetyltrimethylammonium chloride (CTAC) as a template. Interestingly, the thickness of the mesoporous silica coating could be tightly adjusted by either the silica precursor concentration or by varying the CTAC concentration while keeping the silica precursor concentration constant. Finally, the influence of the silica coating on the antimicrobial effect of AgNPs was studied on Gram-negative bacteria (R. gelatinosus and E. coli) and under different bacterial growth conditions, shedding light on their potential applications in different biological environments.
Tailoring Mesoporous Silica-Coated Silver Nanoparticles and Polyurethane-Doped Films for Enhanced Antimicrobial Applications
Publication . Nuti, Silvia; Fernández-Lodeiro, Adrián; Galhano, Joana; Oliveira, Elisabete; Duarte, Maria Paula; Capelo-Martínez, José Luis; Lodeiro, Carlos; Fernández-Lodeiro, Javier; DQ - Departamento de Química; LAQV@REQUIMTE; MEtRICS - Centro de Engenharia Mecânica e Sustentabilidade de Recursos; MDPI AG
The global increase in multidrug-resistant bacteria poses a challenge to public health and requires the development of new antibacterial materials. In this study, we examined the bactericidal properties of mesoporous silica-coated silver nanoparticles, varying the core sizes (ca. 28 nm and 51 nm). We also investigated gold nanoparticles (ca. 26 nm) coated with mesoporous silica as possible inert metal cores. To investigate the modification of antimicrobial activity after the surface charge change, we used silver nanoparticles with a silver core of 28 nm coated with a mesoporous shell (ca. 16 nm) and functionalized with a terminal amine group. Furthermore, we developed a facile method to create mesoporous silica-coated silver nanoparticles (Ag@mSiO2) doped films using polyurethane (IROGRAN®) as a polymer matrix via solution casting. The antibacterial effects of silver nanoparticles with different core sizes were analyzed against Gram-negative and Gram-positive bacteria relevant to the healthcare and food industry. The results demonstrated that gold nanoparticles were inert, while silver nanoparticles exhibited antibacterial effects against Gram-negative (Escherichia coli and Salmonella enterica subsp. enterica serovar Choleraesuis) and Gram-positive (Bacillus cereus) strains. In particular, the larger Ag@mSiO2 nanoparticles showed a minimum inhibitory concentration (MIC) and a minimum bactericidal concentration (MBC) of 18 µg/mL in the Salmonella strain. Furthermore, upon terminal amine functionalization, reversing the surface charge to positive values, there was a significant increase in the antibacterial activity of the NPs compared to their negative counterparts. Finally, the antimicrobial properties of the nanoparticle-doped polyurethane films revealed a substantial improvement in antibacterial efficacy. This study provides valuable information on the potential of mesoporous silica-coated silver nanoparticles and their applications in fighting multidrug-resistant bacteria, especially in the healthcare and food industries.
Synthesis and Structural Characterization of Branched Bimetallic AuPd Nanoparticles with a Highly Tunable Optical Response
Publication . Nuti, Silvia; Fernández-Lodeiro, Adrián; Chinchilla, Lidia E.; Hungría, Ana B.; Capelo-Martinez, José Luis; Lodeiro, Carlos; Fernández-Lodeiro, Javier; DQ - Departamento de Química; LAQV@REQUIMTE; ACS - American Chemical Society
Bimetallic nanostructures composed of gold (Au) and palladium (Pd) have garnered increased interest for their applications in heterogeneous catalysis. This study reports a simple strategy for manufacturing Au@Pd bimetallic branched nanoparticles (NPs), which offer a tunable optical response, using polyallylamine-stabilized branched AuNPs as template cores for Pd overgrowth. The palladium content can be altered by manipulating the concentration of PdCl42- and ascorbic acid (AA) that are injected, which permit an overgrowth of the Pd shell up to ca. 2 nm thick. The homogeneous distribution of Pd at the surfaces of Au NPs can be carried out regardless of their size or branching degree, which allows for an adjustment of the plasmon response in the near-infrared (NIR) spectral range. As a proof of concept, the nanoenzymatic activity of pure gold and gold-palladium NPs was compared, exploring their peroxidase-like activity in the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). The bimetallic AuPd NPs demonstrate an increase in the catalytic properties attributed to the presence of palladium at the surface of gold.
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SFRH/BD/144618/2019