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ACS Appl Mater Interfaces ; 13(33): 39806-39818, 2021 Aug 25.
Artigo em Inglês | MEDLINE | ID: mdl-34387459


Silver nanomaterials have attracted a great deal of interest due to their broad-spectrum antimicrobial activity. However, it is still challenging to balance the high antibacterial efficiency with low damage to biological cells of silver nanostructures, especially when the diameter decreases to less than 10 nm. Here, we developed a new type of Ag nanohybrid material via a unimolecular micelle template method, which presents amazing antibacterial activities and almost noncytotoxicity. First, water-soluble multiarm star-shaped brushlike copolymer α-CD-g-[(PEO40-g-PAA50)-b-PEO5]18 was precisely synthesized and its micelle behavior in different solvents was revealed. Then, nanocrystal clusters assembled by Ag grains (Ag@Template NCs) were prepared through an in situ redox route using the unimolecular micelle of α-CD-g-[(PEO40-g-PAA50)-b-PEO5]18 as the soft template, AgNO3 as a precursor, and tetrabutylammonium borohydride (TBAB) as the reducing agent. The overall size of the achieved Ag@Template NCs is controlled by the template structure at around 40 nm (Dh in DMF), and the size of the Ag grain can be easily regulated from ∼1 to ∼5 nm by adjusting the feeding ratio of AgNO3/acrylic acid (AA) units in the template from 1:10 to 1:1. Benefitting from the structural design of the template, all Ag@Template NCs prepared here exhibit excellent dispersibility and chemical stability in different aqueous environments (neutral, pH = 5.5, and 0.9% NaCl physiological saline solution), which play a crucial role in the long-term storage and potential application in a complex physiological environment. The antibacterial and cytotoxicity tests indicate that Ag@Template NCs display much better performance than Ag nanoparticles (Ag NPs), which have a comparable overall size of ∼25 nm. The inhibitory capability of Ag@Template NCs to bacteria strongly depends on the grain size. Specifically, the Ag@Template-1 NC assembled by the smallest grains (1.6 ± 0.3 nm) presents the best antibacterial activity. For E. coli (-), the MIC value is as low as 5 µg/mL (0.36 µg/mL of Ag), while for S. aureus (+), the value is around 10 µg/mL (0.72 µg/mL of Ag). The survival rate of L02 cells and lactate dehydrogenase assay together illustrate the low cytotoxicity possessed by the prepared Ag@Template NCs. Therefore, the proposed Ag@Template NC structure successfully resolves the high reactivity, instability, and fast oxidation issues of the ultrasmall Ag nanoparticles, and integrates high antibacterial efficiency and nontoxicity to biological cells into one platform, which implies its broad potential application in biomedicine.

Antibacterianos/efeitos adversos , Antibacterianos/química , Nanopartículas Metálicas/química , Prata/química , Antibacterianos/metabolismo , Boroidretos/química , Sobrevivência Celular/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Tamanho da Partícula , Polímeros/química , Compostos de Amônio Quaternário/química , Staphylococcus aureus/efeitos dos fármacos , Propriedades de Superfície , Nanomedicina Teranóstica
Chemistry ; 27(38): 9814-9819, 2021 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-33834537


Based on the DFT-level-calculated molecular volume (Vmol ) of pyrrole and its liquid density, pyrrole manifests the highest liquid density coefficient LDc (defined as [Vmol ×density ×0.6023]/FW) value of 0.7. Normal liquids have LDc <0.63. This very high LDc is due to the strong N-H⋅⋅⋅π interactions in solution, and hence pyrrole can be considered to be a pseudo-crystalline liquid. When trapped inside the confined space of a crystalline sponge, a reorientation of the N-H⋅⋅⋅π interaction is observed leading to specific cyclic N-H⋅⋅⋅π tetramers and N-H⋅⋅⋅π dimers, as verified by single-crystal X-ray crystallographic and computational methods. These tetramers are of the same size as four pyrrole molecules in the solid-state of pyrrole, yet the cyclic N-H⋅⋅⋅π intermolecular interactions are circularly oriented instead of being in the linear zigzag structure found in the X-ray structure of a solid pyrrole. The confinement thus acts as an external driving force for tetramer formation.

Pirróis , Cristalografia por Raios X , Modelos Moleculares