3 research outputs found
Exploiting Micelle-Driven Coordination To Evaluate the Lipophilicity of Molecules
We present a systematic study based on the calculation
of complexation
constants between a Zn-complex solubilized in Triton X-100 micellar
solutions and a series of linear mono- and dicarboxylic acids, under
physiological pH conditions, that allowed the evaluation of the lipophilicity
of these molecules. This empirical lipophilicity parameter describes
conveniently the partition of organic molecules between hydrophobic
microdomains and water. The results can be used to predict the lipophilicity
of molecules with similar structure and allows the distinction of
intrinsic contributions of the carboxylates and of the methylene groups
to the lipophilicity of the molecule
Optical Method for Predicting the Composition of Self-Assembled Monolayers of Mixed Thiols on Surfaces Coated with Silver Nanoparticles
With a simple optical
method, based on UV–vis absorption spectra on glass slides,
it is possible to predict the composition of self-assembled monolayers
of mixed thiols, grafted on monolayers of silver nanoparticles. Glass
slides are modified with the layer-by-layer technique, first forming
a monolayer of mercaptopropyltrimethoxysilane, then grafting a monolayer
of silver nanoparticles on it. These surfaces are further coated by
single or mixed thiol monolayers, by dipping the slides in toluene
solutions of the chosen thiols. Exchange constants are calculated
for the competitive deposition between the colorless 1-dodecanethiol
or PEG5000 thiol and BDP-SH, with the latter being a thiol-bearing
molecule containing the strongly absorbing BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene)
moiety, synthesized on purpose. The constants are calculated by determining
the fraction of BDP-SH deposited on the surface from a solution with
a given molar fraction, directly measuring the absorption spectra
of BDP-SH on the slides. Then, the exchange constant for the competitive
deposition between 1-dodecanethiol and PEG5000 thiol is calculated
by combining their exchange constants with BDP-SH. This allows to
predict the fraction of the two colorless thiols coating the silver
nanoparticles slides obtained from a toluene solution with a given
molar fraction, for example, of PEG5000 thiol. The correctness of
the calculated surface fraction is verified by studying the coating
competition between 1-dodecanethiol and a PEG5000 thiol remotely modified
with a strongly absorbing fluorescein fragment
Antibacterial Activity of Glutathione-Coated Silver Nanoparticles against Gram Positive and Gram Negative Bacteria
In the present paper, we study the mechanism of antibacterial
activity
of glutathione (GSH) coated silver nanoparticles (Ag NPs) on model
Gram negative and Gram positive bacterial strains. Interference in
bacterial cell replication is observed for both cellular strains when
exposed to GSH stabilized colloidal silver in solution, and microbicidal
activity was studied when GSH coated Ag NPs are (i) dispersed in colloidal
suspensions or (ii) grafted on thiol-functionalized glass surfaces.
The obtained results confirm that the effect of dispersed GSH capped
Ag NPs (GSH Ag NPs) on Escherichia coli is more intense because it can be associated with the penetration
of the colloid into the cytoplasm, with the subsequent local interaction
of silver with cell components causing damages to the cells. Conversely,
for Staphylococcus aureus, since the
thick peptidoglycan layer of the cell wall prevents the penetration
of the NPs inside the cytoplasm, the antimicrobial effect is limited
and seems related to the interaction with the bacterial surfaces.
Experiments on GSH Ag NPs grafted on glass allowed us to elucidate
more precisely the antibacterial mechanism, showing that the action
is reduced because of GSH coating and the limitation of the translational
freedom of NPs