Abstract:In this study, spontaneous synthesis of a gold (Au) colloid using cells of Cupriavidus metallidurans CH34 is reported, and compared with results obtained using cells of the model bacterium Escherichia coli MG1655. To investigate the synthesis mechanism, bacterial biomass and secretomes from both strains were incubated with Au(III) ions. Only CH34 cells were capable of producing extracellular dispersions of Au nanoparticles (NPs). Transmission electron microscopy images showed that AuNPs morphology was dominate… Show more
“…Size distributions for each nanocomposite were obtained as follows: three TEM images for each sample were obtained and analyzed with a home-made image processing software developed with Matlab® and the nanoparticle count was 500 for Acyl-CO-AuNPs, 1000 for CO-AuNPs, and 100 for COS@n-AuNP series. The average size for each sample is summarized in Table 2, column “Average TEM diameter (nm).” It is worth to point out that AuNPs synthesized with chitosan oligosaccharide resulted spherical, with a better size distribution as compared with similar ones obtained with other green synthesis methodologies reported in the literature [36, 38, 41–43]. Fig.…”
Currently, gold nanoparticles have found applications in engineering and medical sciences, taking advantage from their properties and characteristics. Surface plasmon resonance, for instance, is one of the main features for optical applications and other physical properties, like high density, that represents the key for cellular uptake. Among other applications, in the medical field, some diseases may be treated by using gene therapy, including monogenetic or polygenetic disorders and infections. Gene adding, suppression, or substitution is one of the many options for genetic manipulation. This work explores an alternative non-viral method for gene transfer by using gold nanoparticles functionalized with organic polymers; two routes of synthesis were used: one of them with sodium borohydride as reducing agent and the other one with chitosan oligosaccharide as reducing and stabilizing agent. Gold nanoparticles conjugated with chitosan, acylated chitosan and chitosan oligosaccharide, were used to evaluate transfection efficiency of plasmid DNA into cell culture (HEK-293). Physical and chemical properties of gold nanocomposites were characterized by using UV-Vis Spectroscopy, ξ
-
potential, and transmission electron microscopy. Furthermore, the interaction between gold nanoparticles and plasmid DNA was demonstrated by using agarose gel electrophoresis. Transfection tests were performed and evaluated by β-galactosidase activity and green fluorescence protein expression. The percentage of transfection obtained with chitosan, acylated chitosan, and chitosan oligosaccharide were of 27%, 33%, and 60% respectively.
“…Size distributions for each nanocomposite were obtained as follows: three TEM images for each sample were obtained and analyzed with a home-made image processing software developed with Matlab® and the nanoparticle count was 500 for Acyl-CO-AuNPs, 1000 for CO-AuNPs, and 100 for COS@n-AuNP series. The average size for each sample is summarized in Table 2, column “Average TEM diameter (nm).” It is worth to point out that AuNPs synthesized with chitosan oligosaccharide resulted spherical, with a better size distribution as compared with similar ones obtained with other green synthesis methodologies reported in the literature [36, 38, 41–43]. Fig.…”
Currently, gold nanoparticles have found applications in engineering and medical sciences, taking advantage from their properties and characteristics. Surface plasmon resonance, for instance, is one of the main features for optical applications and other physical properties, like high density, that represents the key for cellular uptake. Among other applications, in the medical field, some diseases may be treated by using gene therapy, including monogenetic or polygenetic disorders and infections. Gene adding, suppression, or substitution is one of the many options for genetic manipulation. This work explores an alternative non-viral method for gene transfer by using gold nanoparticles functionalized with organic polymers; two routes of synthesis were used: one of them with sodium borohydride as reducing agent and the other one with chitosan oligosaccharide as reducing and stabilizing agent. Gold nanoparticles conjugated with chitosan, acylated chitosan and chitosan oligosaccharide, were used to evaluate transfection efficiency of plasmid DNA into cell culture (HEK-293). Physical and chemical properties of gold nanocomposites were characterized by using UV-Vis Spectroscopy, ξ
-
potential, and transmission electron microscopy. Furthermore, the interaction between gold nanoparticles and plasmid DNA was demonstrated by using agarose gel electrophoresis. Transfection tests were performed and evaluated by β-galactosidase activity and green fluorescence protein expression. The percentage of transfection obtained with chitosan, acylated chitosan, and chitosan oligosaccharide were of 27%, 33%, and 60% respectively.
“…Heavy metals such as cadmium destroy thiol groups in proteins, triggering an oxidative stress response in bacteria (Harrison et al, 2007; Nies, 2016). It has been proposed that the synthesis of gold nanoparticles from Au (III) ions by CH34 cells is catalyzed by sulfur-rich proteins, which are oxidized (Montero-Silva et al, 2018). Cadmium probably also oxidizes sulfur-rich proteins in CH34 cells, causing oxidative stress and inducing a specific PDE that decreases c-di-GMP concentration.…”
Section: Discussionmentioning
confidence: 99%
“…Strain CH34 has been used for bioremediation, recovery, and reduction of heavy metals (Mergeay et al, 1985; Collard et al, 1994; Janssen et al, 2010). C. metallidurans CH34 harbors numerous heavy metal resistance determinants involved in diverse mechanisms, including complexation, efflux systems, reduction, and reductive precipitation, which enable cell detoxification and survival (Nies, 2016; Maes et al, 2017; Montero-Silva et al, 2018). A high number of CH34 gene products confer tolerance to high concentrations of heavy metals, including the CzcCBA, CzcD, CzcP, and CadA proteins that are involved in cadmium resistance (Nies, 2016).…”
Cadmium is a highly toxic heavy metal for biological systems.
Cupriavidus metallidurans
CH34 is a model strain to study heavy metal resistance and bioremediation as it is able to deal with high heavy metal concentrations. Biofilm formation by bacteria is mediated by the second messenger
bis
-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP). The aim of this study was to characterize the response of
C. metallidurans
CH34 planktonic and biofilm cells to cadmium including their c-di-GMP regulatory pathway. Inhibition of the initiation of biofilm formation and EPS production by
C. metallidurans
CH34 correlates with increased concentration of cadmium. Planktonic and biofilm cells showed similar tolerance to cadmium. During exposure to cadmium an acute decrease of c-di-GMP levels in planktonic and biofilm cells was observed. Transcription analysis by RT-qPCR showed that cadmium exposure to planktonic and biofilm cells induced the expression of the
urf2
gene and the mercuric reductase encoding
merA
gene, which belong to the Tn
501
/Tn
21 mer
operon. After exposure to cadmium, the
cadA
gene involved in cadmium resistance was equally upregulated in both lifestyles. Bioinformatic analysis and complementation assays indicated that the protein encoded by the
urf2
gene is a functional phosphodiesterase (PDE) involved in the c-di-GMP metabolism. We propose to rename the
urf2
gene as
mrp
gene for
m
etal
r
egulated
P
DE. An increase of the second messenger c-di-GMP content by the heterologous expression of the constitutively active diguanylate cyclase PleD correlated with an increase in biofilm formation and cadmium susceptibility. These results indicate that the response to cadmium in
C. metallidurans
CH34 inhibits the initiation of biofilm lifestyle and involves a decrease in c-di-GMP levels and a novel metal regulated PDE.
“…In this study, the value of MIC was defined as the minimum quinolone concentration that inhibited bacterial growth as determined by spectrophotometric inspection [7].…”
This work determined the potency of hexyl-ciprofloxacin molecules that reversibly interact with gold nanoparticles (AuNPs) passivated with 11-mercaptoundecanoic acid (MUA) on Escherichia coli cells. For this, partition of modified antibiotic between different compartments of the gold colloid was determined using analytical techniques. First, concentration of hexylciprofloxacin was determined in the continuous phase of the colloid. Subsequently, the colloid was exposed to a volume of organic immiscible solvent and concentration of the transferred molecules was determined in the organic phase. Comparison of the amount of hexyl-ciprofloxacin in each phase revealed that interaction between molecules and nanoparticles was reversible. Later, this work determined the potency of a population of hexyl-ciprofloxacin molecules contained in a volume of the colloid, and the potency of other population of molecules that only interact with the continuous phase of the colloid. The absolute difference between these two values was proportional to the potency of a number of molecules that interact with the nanoparticles of the colloid.
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