Multicolor, fluorescent self-healing
gels were constructed through
reacting carbon dots produced from different aldehyde precursors with
branched polyethylenimine. The self-healing gels were formed through
Schiff base reaction between the aldehyde units displayed upon the
carbon dots’ surface and primary amine residues within the
polyethylenimine network, generating imine bonds. The dynamic covalent
imine bonds between the carbon dots and polymeric matrix endowed the
gels with both excellent self-healing properties as well as high mechanical
strength. Moreover, the viscoelastic properties of the gels could
be intimately modulated by controlling the ratio between the carbon
dots and polymer. The distinct fluorescence emissions of the gels,
originating from the specific carbon dot constituents, were employed
for fabrication of light emitters at different colors, particularly
generating white light.
Carbon dots (C-dots) prepared through heating of aminoguanidine and citric acid enable bimodal (colorimetric and fluorescence) detection of nitric oxide (NO) in aqueous solutions. The C-dots retained the functional units of aminoguanidine, which upon reaction with NO produced surface residues responsible for the color and fluorescence transformations. Notably, the aminoguanidine/citric acid C-dots were noncytotoxic, making possible real-time and high sensitivity detection of NO in cellular environments. Using multiprong spectroscopic and chromatography analyses we deciphered the molecular mechanism accounting for the NO-induced structural and photophysical transformations of the C-dots, demonstrating for the first time N release and azo dye formation upon the C-dots' surface.
Pseudomonas aeruginosa is a highly virulent bacterium, particularly associated with the spread of multidrug resistance. Here we show that carbon dots (C-dots), synthesized from aminoguanidine and citric acid precursors, can selectively stain and inhibit the growth of P. aeruginosa strains. The aminoguanidine-C-dots were shown both to target P. aeruginosa bacterial cells and also to inhibit biofilm formation by the bacteria. Mechanistic analysis points to interactions between aminoguanidine residues on the C-dots' surface and P. aeruginosa lipopolysaccharide moieties as the likely determinants for both antibacterial and labeling activities. Indeed, the application of biomimetic membrane assays reveals that LPS-promoted insertion and bilayer permeation constitute the primary factors in the anti-P. aeruginosa effect of the aminoguanidine-C-dots. The aminoguanidine C-dots are easy to prepare in large quantities and are inexpensive and biocompatible and thus may be employed as a useful vehicle for selective staining and antibacterial activity against P. aeruginosa.
A hybrid carbon-dot (C-dot)-hydrogel matrix was constructed and employed for detection of bacteria. The transduction mechanism is novel, based upon cleavage of ester bonds within the hydrogel scaffold by bacterially-secreted esterases; the ensuing fluidization of the hydrogel resulted in aggregation of the embedded C-dots and consequent quenching of their fluorescence. We show that the C-dot-hydrogel exhibits high sensitivity and can distinguish among bacterial species through modulation of the emitted fluorescence, depending upon their esterase secretions.
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