Therapy of bacterial urinary tract infections (UTIs) and catheter associated urinary tract infections (CAUTIs) is still a great challenge because of the resistance of bacteria to nowadays used ...antibiotics and encrustation of catheters. Bacterial cellulose (BC) as a biocompatible material with a high porosity allows incorporation of different materials in its three dimensional network structure. In this work a low molecular weight chitosan (Chi) polymer is incorporated in BC with different concentrations. Different characterization techniques are used to investigate structural and optical properties of these composites. Radical scavenging activity test shows moderate antioxidant activity of these biocompatible composites whereas
in vitro
release test shows that 13.3% of chitosan is released after 72 h. Antibacterial testing of BC-Chi composites conducted on Gram-positive and Gram-negative bacteria causing UTIs and CAUTIs (
Escherichia coli
,
Pseudomonas aeruginosa
,
Klebsiella pneumoniae
) and encrustation (
Proteus mirabilis
) show bactericidal effect. The morphology analysis of bacteria after the application of BC-Chi shows that they are flattened with a rough surface, with a tendency to agglomerate and with decreased length and width. All obtained results show that BC-Chi composites might be considered as potential biomedical agents in treatment of UTIs and CAUTIs and as a urinary catheter coating in encrustation prevention.
Bacterial cellulose-chitosan composite with antibacterial and moderate antioxidant activity for potential UTI/CAUTI treatment and catheter coating in encrustation prevention.
Due to controversial reports concerning antibacterial activity of different graphene based materials it is very important to investigate their antibacterial action on a wide range of Gram-positive ...and Gram-negative bacteria. In this paper we have investigated the structure induced phototoxic antibacterial activity of four types of graphene based materials: graphene oxide (GO), graphene quantum dots (GQDs), carbon quantum dots (CQDs) and nitrogen doped carbon quantum dots (N-CQDs). Antibacterial activity was tested on 19 types of bacteria. It is found that nanometer-size CQDs and N-CQDs are the most potent agents whereas micrometer-size GO has very poor antibacterial activity. Electron paramagnetic resonance measurements confirmed photodynamic production of singlet oxygen for all types of used quantum dots. Detailed analysis has shown that N-CQDs are an excellent photodynamic antibacterial agent for treatment of bacterial infections induced by
Enterobacter aerogenes
(
E. aerogenes
),
Proteus mirabilis
(
P. mirabilis
),
Staphylococcus saprophyticus
(
S. saprophyticus
),
Listeria monocytogenes
(
L. monocytogenes
),
Salmonella typhimurium
(
S. typhimurium
) and
Klebsiella pneumoniae
.
Antibacterial potentials of four graphene based nanomaterials are tested on a wide range of bacteria.
Kinetics and thermodynamics of the phenolic O-H and the C-ring C-H bond breaking in dihydrokaempferol, a natural flavonoid compound, was investigated using a density functional based approach. The ...rate constants calculated using the variational transition state theory with multidimensional tunneling corrections indicate 4′-OH phenolic hydrogen as operative in the inactivation of a hydroperoxyl radical (&z.rad;OOH). The proton coupled electron transfer (PCET) mechanism appears as preferred in O-H bond breaking by &z.rad;OOH, while the hydrogen atom transfer (HAT) mechanism is involved in the C-H bond cleavage. Comparison of the antioxidant potency of dihydrokaempferol
vs.
kaempferol proves the superiority of the latter and the negligible role of the C-ring hydrogens of dihydrokaempferol in radical scavenging. The obtained results confirm the traditional view that O-H groups of polyphenols are responsible for radical inactivation contrary to recent proposals that the aliphatic C-ring hydrogens also contribute to this activity.
In order to correctly estimate hydrogen atom abstraction from polyphenols, kinetic analysis including suitable tunneling effects should be mandatory.
It has been generally accepted that, due to high ionization potential values, single electron transfer followed by proton transfer (SET-PT) is not a plausible mechanism of antioxidant action in ...flavonoids. In this paper the SET-PT mechanism of quercetin (Q) was examined by revealing possible reaction paths of the once formed quercetin radical cation (Q
+
&z.rad;) at the M0-52X/6311+G(d,p) level of theory. The deprotonation of Q
+
&z.rad; was simulated by examining its chemical behavior in the presence of three bases: methylamine (representative of neutral bases), the MeS anion (CH
3
S
−
) and the hydroxide anion (representative of anionic bases). It was found that Q
+
&z.rad; will spontaneously be transformed into Q in the presence of bases whose HOMO energies are higher than the SOMO energy of Q
+
&z.rad; in a given medium, implying that Q cannot undergo the SET-PT mechanism in such an environment. In the reaction with the MeS anion in both gaseous and aqueous phases and the hydroxide anion in the gaseous phase Q
+
&z.rad; accepts an electron from the base, and so-formed Q undergoes the hydrogen atom transfer mechanism. On the other hand, SET-PT is a plausible mechanism of Q in the presence of bases whose HOMO energies are lower than the SOMO energy of Q
+
&z.rad; in a given medium. In such cases Q
+
&z.rad; spontaneously donates a proton to the base, with energetic stabilization of the system. Our investigation showed that Q conforms to the SET-PT mechanism in the presence of methylamine, in both gaseous and aqueous phases, and in the presence of the hydroxide anion, in the aqueous solution.
SET-PT is a plausible mechanism of quercetin in the presence of bases whose HOMO energies are lower than the SOMO energy of the quercetin radical cation.
Combined spectroscopic (UV/visible, MS and EPR), electrochemical (CV) and theoretical approaches were used to evaluate the relevant interactions of morin and quercetin, as well as their respective ...iron(
iii
) complexes with DPPH, tempone, hydroxyl and superoxide radicals. The results on iron complexation specify the stoichiometry and the relevant structural forms entering the chelation of the molecules. The spectroscopic DPPH assay shows better antioxidant activity of quercetin and its iron complex both in terms of EC
50
values and stoichiometry. The results of 2-deoxyribose degradation suggest that antioxidant activities of morin and quercetin may originate from their combined effect of iron chelation and radical scavenging. The distinctive difference in the EPR spectra of morin and quercetin radicals suggests different positions of the radical centers which may account for different sequences of their activities towards investigated radicals. Activity ranking of quercetin and morin, established by cyclic voltammetry, confirms their activity sequence obtained by EPR results and is also in agreement with the results of conformational analysis. The equilibrium geometries, optimized with the M052X functionals and 6-311G(d,p) basis set, predict structural modifications between the ligand molecules in the free state and in the complex structures. The arguments gained through experimental results can also be rationalized in terms of overall molecular geometry and structural features governing antioxidant behavior
i.e.
substitution pattern of the ring B.
Combined spectroscopic, electrochemical and theoretical approaches are used to evaluate interactions of morin, quercetin and their iron complexes with radical species.
Background. The aim of the study was to investigate the antihypertensive effects of angiotensin II type-1 receptor blocker, losartan, and its potential in slowing down renal disease progression in ...spontaneously hypertensive rats (SHR) with adriamycin (ADR) nephropathy. Methods. Six-month-old female SHR were randomly selected in six groups. Two control groups (SH6, SH12) received vehicle. Groups ADR6, ADR+LOS6 and ADR12, and ADR+LOS12 received ADR (2 mg/kg/b.w. i.v.) twice in a 3-week interval. Group ADR+LOS6 received losartan (10 mg/kg/b.w./day by gavages) for 6 weeks and group ADR+LOS12 for 12 weeks after second injection of ADR. Animals were killed after 6 or 12 weeks, respectively. Haemodynamic measurements were performed on anaesthetized animals, blood and urine samples were taken for biochemical analysis and the left kidney was processed for morphological studies. Results. Short-term losartan treatment, besides antihypertensive effect, improved glomerular filtration rate and ameliorated glomerulosclerosis resulting in decreased proteinuria. Prolonged treatment with losartan showed further reduction of glomerulosclerosis associated with reduced progression of tubular atrophy and interstitial fibrosis, thus preventing heavy proteinuria and chronic renal failure. Losartan reduced uraemia and increased urea clearance in advanced ADR nephropathy in SHR. Histological examination showed that losartan could prevent tubular atrophy, interstitial infiltration and fibrosis in ADR nephropathy. Conclusion. Losartan reduces the rate of progression of ADR-induced focal segmental glomerulosclerosis to end-stage renal disease in SHR.
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