Carbon Quantum Dot Surface-Chemistry-Dependent Ag Release Governs the High Antibacterial Activity of Ag-Metal–Organic Framework Composites

Abstract

Nanocomposites and hybrid materials of Ag−1,3,5benzenetricarboxylic acid metal−organic frameworks (MOFs) with Sand N-carbon quantum dots (CQDs) were synthesized and evaluated for their antibacterial activity against representative Gram-positive (Bacillus subtilis) and Gram-negative (Escherichia coli) bacterial strains using the qualitative disk-diffusion approach and the quantitative minimum inhibitory concentration test. The composites and hybrids were found to be nontoxic to living cells. The composite formation fostered a synergistic effect that enhanced their antibacterial activity compared with those of their pristine components. Charge transfer from AgMOF to CQDs facilitated the electrostatic interactions of the composites and hybrids with the bacterial cell membranes. Enhanced bactericidal activity was linked to morphological features (a nanorod-like morphology) and specific surface chemistry. The latter affected the release of silver. Silver on the surface of the MOFs rather than silver in the bulk was found to be important. The destruction of the MOF component in the extracellular environment led to the release of silver ions, which have a high affinity to S compounds of the cell physiology. The formation of metallic silver (Ag°) and silver sulfides (Ag 2 S) was suggested as essential for the ability of the composites and hybrids to inhibit bacterial growth. To the best of our knowledge, this is the first study that introduces the bactericidal effect of AgMOF−CQDs composites and hybrids.

Paramagnetic solid-state NMR assignment and novel chemical conversion of the aldehyde group to dihydrogen ortho ester and hemiacetal moieties in copper(ii)- and cobalt(ii)-pyridinecarboxaldehyde complexes

“…Similar shi values have been previously reported for water molecules in many different systems. 7,53,54 Particularly, Gul-E-Noor et al assigned proton resonances of water molecules in the range of d 1 H ¼ 15-4 ppm for Cu 3 (BTC) 2 MOF structures. 55,56 The main difficulty in studying the chemical functionalization of the ligand in the Cu(II) complex obtained in water is that single crystals for structural characterization could not be obtained.…”

Silver Covalently Bound to Cyanographene Overcomes Bacterial Resistance to Silver Nanoparticles and Antibiotics

“…Inorganic [ 4–9 ] and carbon‐based nanomaterials, [ 9–12 ] polymers and peptides, [ 13,14 ] as well as light‐activated nanomaterials [ 15,16 ] have emerged as promising antimicrobial agents for treatment and prevention of infectious diseases. Particularly silver colloids can inhibit growth of pathogens at very low concentrations.…”

Carbon Dots as an Emergent Class of Antimicrobial Agents

“…For example, the addition of polyamines [ 16 , 62 ], amino acids [ 63 , 64 , 65 , 66 , 67 ], or biomass such as plant leaves and fungi [ 68 , 69 , 70 , 71 , 72 , 73 , 74 ], food [ 75 , 76 , 77 , 78 , 79 ], and industrial [ 80 ] and waste derivatives [ 81 , 82 ], among others, have been used for the preparation of doped CDs. In this context, two independent comparative studies from the Kang [ 83 ] and Bandosz [ 84 ] research groups highlighted that N- or S-doped CDs exhibit very different antibacterial properties. The authors demonstrated that the increased S-doping content correlates with an increase in repulsive forces between the less positively charged CDs (when compared to N-doped CDs) and the negatively charged bacterial surfaces.…”