Improving the therapeutic characteristics of antibiotics is an effective strategy for controlling the growth of multidrug-resistant Gram-negative microorganisms. The purpose of this study was to ...develop a colistin (CT) delivery system based on hyaluronic acid (HA) and the water-soluble cationic chitosan derivative, diethylaminoethyl chitosan (DEAECS). The CT delivery system was a polyelectrolyte complex (PEC) obtained by interpolymeric interactions between the HA polyanion and the DEAECS polycation, with simultaneous inclusion of positively charged CT molecules into the resulting complex. The developed PEC had a hydrodynamic diameter of 210-250 nm and a negative surface charge (ζ-potential = -19 mV); the encapsulation and loading efficiencies were 100 and 16.7%, respectively. The developed CT delivery systems were characterized by modified release (30-40% and 85-90% of CT released in 15 and 60 min, respectively) compared to pure CT (100% CT released in 15 min). In vitro experiments showed that the encapsulation of CT in polysaccharide carriers did not reduce its antimicrobial activity, as the minimum inhibitory concentrations against
of both encapsulated CT and pure CT were 1 μg/mL.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The thermal effect of a model oxo-transfer reaction with the participation of a tungsten-containing synthetic analog of the enzyme active site, WO
2
(mnt)
2
2−
(mnt = maleonitriledithiolate), has ...been determined for the first time. The value of the thermal effect indicates that the driving force of the oxo-transfer is the enthalpy factor. To determine the thermal effect of oxo-transfer, the dissolution enthalpies of the reaction participants in acetonitrile were determined:
Δ
H
sol
0
PPh
3
=
24.9
±
0.8
kJ mol
−1
,
Δ
H
sol
0
OPPh
3
=
18.9
±
0.6
kJ mol
−1
, and
Δ
H
sol
0
(Bu
4
N
2
WO
2
(mnt)
2
) = (70.8 ± 1.9) kJ mol
−1
. In this study, the thermal effect of the transfer process of an oxygen atom from the tungsten complex WO
2
(mnt)
2
2−
to the PPh
3
substrate was determined at different ratios of reagents: Δ
r
H
0
= (− 109 ± 4) kJ mol
−1
. The catalytic cycle of PPh
3
oxidation with oxygen in the presence of WO
2
(mnt)
2
2−
in acetonitrile solution was described calorimetrically. The absence of the reduced form of tungsten in the solution after the oxo-transfer reaction was shown spectroscopically, which confirms the role of the tungsten complex in the PPh
3
oxidation as the catalyst.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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Aqueous solutions of nonionic surfactants are of interest for bioprocesses, particularly as solubilizing agents for hydrophobic substances. To design such processes, the data on ...partition coefficients of solutes between micelles and their aqueous surrounding (Pmw) are of high value. An extended understanding of the partition behavior can be achieved from the structural information such as the micelle size and micelles composition.
In this work, mixtures of nonionic surfactants Triton X-100 and Brij 35 were under study. The data on critical micelle concentrations showed partly non-ideal behavior of the solutions. The compositions of mixed micelles at different molar Brij 35/Triton X-100 ratios in the surfactant mixture were estimated from the data on self-diffusion coefficients (NMR diffusometry) and were calculated within the regular solution approach and predicted by Motomura’s model. The change of the mixed micelle composition in dependence on the total surfactant concentration was observed. It has been found, that the average value of the mixed micelles radii is ∼4nm. Whereas, the polydispersity indexes and the aggregation numbers increased with Triton X-100 fraction. Moreover, the Pmw values of different non-dissociated solutes (phenyl derivatives with various functional groups) were determined by means of micellar liquid chromatography (MLC) and were predicted using the thermodynamic model COSMOmic, an extension of COSMO-RS. In general, it has been proved that COSMOmic is able to predict Pmw in the mixed micellar system formed by nonionic surfactants.
The obtained data show the possibility of modulating the partition behavior of solutes using the mixtures of nonionic surfactants. Apart from the hydrophobicity, the «surfactants – solute» specific interactions play an important role in the partition behavior of the investigated systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Polyelectrolyte complexes (PECs) based on polysaccharides, including hyaluronic acid (HA) and chitosan (CS), are promising delivery systems for antimicrobial agents, including oral administration of ...the peptide antibiotic colistin (CT). Modification of CS with different targeting ligands to improve intestinal permeability is a suitable way to improve the oral bioavailability of polyelectrolyte particles. This study describes the procedure for obtaining CT-containing PECs based on HA and CS modified with cyanocobalamin (vitamin B12). In this case, vitamin B12 is used as a targeting ligand because it is absorbed in the ileum via specific transporter proteins. The resulting PECs had a hydrodynamic size of about 284 nm and a positive ζ-potential of about 26 mV; the encapsulation efficiency was 88.2 % and the CT content was 42.2 μg/mg. The developed systems provided a two-phase drug release: about 50 % of the CT was released in 0.5–1 h, and about 60 % of the antibiotic was cumulatively released in 5 h. The antimicrobial activity of encapsulated CT was maintained at the same level as the pure drug for at least 24 h (minimum inhibitory concentration against Pseudomonas aeruginosa was 2 μg/mL for both). In addition, the apparent permeability coefficient of CT in the PEC formulation was 2.4 × 10−6 cm/s. Thus, the incorporation of CT into HA- and vitamin B12-modified CS-based PECs can be considered as a simple and convenient method to improve the oral delivery of CT.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This work describes interaction of a family of Pt(N∧C)(PR3)Cl complexes with imidazole (Im), possible application of this chemistry for regioselective labeling of proteins through imidazole rings ...of histidine residues and employment of the resulting phosphorescent products in bioimaging. It was found that the complexes containing aliphatic phosphines display reversible substitution of chloride ligand for imidazole function that required considerable excess of imidazole to obtain full conversion into the substituted Pt(ppy)(PR3)(Im) product, whereas the substitution in the complexes with aromatic phosphines readily proceeds in 1:1.5 mixture of reagents. Rapid, selective, and quantitative coordination of imidazole to the platinum complexes enabled regioselective labeling of ubiquitin. X-ray protein crystallography of the {Pt(ppy)(PPh3)/ubiquitin} conjugate revealed direct bonding of the platinum center to unique histidine-68 residue through the nitrogen atom of imidazole function, the coordination being also supported by noncovalent interaction of the ligands with the protein secondary structure. The variations of the cyclometalating N∧C ligands gave a series of Pt(N∧C)(PPh3)Cl complexes (N∧C = 2-phenylpyridine, 2-(benzofuran-3-yl)pyridine, 2-(benzobthiophen-3-yl)pyridine, methyl-2-phenylquinoline-4-carboxylate), which were used to investigate the impact of N∧C-ligand onto photophysical properties of the imidazole complexes and conjugates with human serum albumin (HSA). The chloride ligand substitution for imidazole and formation of the conjugates results in ignition of the platinum chromophore luminescence with substantially higher quantum yield in the latter case. Variation of the metalating N∧C-ligand made possible the shift of the emission to the red region of visible spectrum for both types of the products. Cell-viability tests revealed low cytotoxicity of all {Pt(N∧C)(PPh3)Cl/HSA} conjugates, while PLIM experiments demonstrated their high potential for oxygen sensing.
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IJS, KILJ, NUK, PNG, UL, UM
Nanotechnology-based modification of known antimicrobial agents is a rational and straightforward way to improve their safety and effectiveness. The aim of this study was to develop colistin ...(CT)-loaded polymeric carriers based on hyaluronic acid (HA) for potential application as antimicrobial agents against multi-resistant gram-negative microorganisms (including ESKAPE pathogens). CT-containing particles were obtained via a polyelectrolyte interaction between protonated CT amino groups and HA carboxyl groups (the CT-HA complex formation constant logKCT-HA was about 5.0). The resulting polyelectrolyte complexes had a size of 210–250 nm and a negative charge (ζ-potential −19 mV), with encapsulation and loading efficiencies of 100% and 20%, respectively. The developed CT delivery systems were characterized by modified release (45% and 85% of CT released in 15 and 60 min, respectively) compared to pure CT (100% CT released in 15 min). In vitro tests showed that the encapsulation of CT in polymer particles did not reduce its pharmacological activity; the minimum inhibitory concentrations of both encapsulated CT and pure CT were 1 μg/mL (against Pseudomonas aeruginosa).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Left: critical micelle concentration of NaDS in aqueous solutions containing C
4mimPF
6, C
6mimBF
4 or C
10mimBr versus the ionic liquid solvent-free mole fraction;
T
=
298.15
K. Right: mixed micelle ...of NaDS–C
10mimBr.
Experimental data on micellization in aqueous solutions of 1-alkyl-3-methylimidazolium salts C
n
mimX and their mixtures with sodium dodecyl sulfate (NaDS) are reviewed. New results (the critical micelle concentration and enthalpy of micellization) are presented for mixtures of C
4mimPF
6, C
6mimBF
4, C
6mimBr and C
10mimBr with NaDS. Our data cover a wide range (from 0 to 0.9) of solvent-free based mole fractions of ionic liquid (IL). Even very small addition of ILs substantially decreases the cmc of NaDS due to the combined effect of electrostatic and hydrophobic interactions, and formation of mixed micelles. It is shown that the quasichemical aggregation model by Nagarajan and Ruckenstein may be successfully applied to aqueous solutions of long-chain ILs and their mixtures with NaDS. The local structure of micelles is obtained from all-atom MD simulations for C
n
mimBr and C
n
mimX
+
NaDS in aqueous medium.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
By the example of single‐walled carbon nanotubes (SWCNT) stabilized by sodium deoxycholate in “water + polyvinyl alcohol” medium, the impact of aggregative peculiarities of a stabilizer on the ...efficacy of dispersing the photoactive agent is investigated. This feature is collated with respect to alternative common anionic surfactants in SWCNT suspensions. The temporal stability of dispersions of the nanocarbon (SWCNT vs carbon black) stabilized by sodium deoxycholate in a medium with controlled viscosity is juxtaposed. The optical power limiting characteristics of these dispersions versus concentration of a polymer dopant (0–3 wt%) is also monitored. In particular, the resistibility of such materials regarding bleaching phenomena in a pulse‐periodic regime (pulse repetition rate 10 Hz) of nanosecond laser irradiation (wavelength 532 nm) is addressed. It is demonstrated that optimal concentration of a polymer dopant (≈1.0 wt%) ensures elimination of bleaching with respect to the irradiation conditions studied.
The optical power limiting performance of nanocarbon (single‐walled nanotubes or carbon black) in aqueous and aqueous‐polymer (polyvinyl alcohol) solutions is examined regarding three factors: 1) choice of a stabilizing surfactant; 2) concentration of a polymer dopant in fluid matrix; 3) aggregation degree of a photoactive agent.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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•MD simulations of 3-methyl-1-dodecylimidazolium bromide micellization in aqueous solutions.•Ethanol, butanol-1 and octanol-1 distribution between the micelle and the aqueous ...surrounding.•Ethanol at low concentration demonstrates the cosolvent properties, at high concentrations cosurfactant properties.•Butanol and octanol are cosurfactants in the investigated concentrations range.•Ethanol distribution coefficient is equal to 0.30, butanol and octanol coefficients depend on their concentrations.
The molecular dynamics simulation of micellization of 3-methyl-1-dodecyl imidazolium bromide in its aqueous solution was carried out. Structural parameters of micelle and the degree of counterions binding were estimated. The simulation of the distribution of normal alcohols (ethanol, butanol-1, octanol-1) at various concentrations between micelle and its aqueous surrounding was carried out. The influence of alcohol additives on the structural characteristics of the micelle was studied, the distribution coefficients were estimated and their dependencies on the alcohols concentrations were defined. The calculated characteristics are in a good agreement with the available experimental data. Evidently, the applied methods of calculations can be extended to the description of the behavior of different dialkylimidazolim ionic liquids in water and to the estimations of the solubilization of a wide range of substances by these ionic liquids (ILs).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Immobilization of Ni2+ ions at the inner surface of monodisperse spherical mesoporous SiO2 particles.•Monodisperse spherical mesoporous SiO2/Ni particles of 500±25nm diameter as metal affinity ...sorbents.•Diclofenac extraction by IMAC technique.•Addition of PFOS to IMAC eluents improves the recovery degree of diclofenac (up to 98%).•The obtained thermodynamics analysis data indicate the chemical nature of the DCF interaction with the surface of the sorbent.
In this research, a novel IMAC sorbent with high specificity for chlorine-containing compounds was developed. Ni-functionalized monodisperse spherical mesoporous silica particles of 500±25nm diameter were synthesized and their metal affinity properties were studied with the use of diclofenac as the model substance. The particles were aggregatively stable in the pH range of 3–12. The sorbent demonstrated a high adsorption capacity (0.60±0.06μg of DCF per 1mg of the sorbent) and high adsorption/desorption rate (20 and 5min was enough for the sorbent saturation and desorption of DCF, correspondingly). A mixture of eluents with addition of PFOS providing the almost complete recovery (98%) of diclofenac was first proposed. The monodispersity and the high sedimentation and aggregative stability of the particles provide the formation of a stable hydrosol even under ultrasound treatment which makes the mSiO2/Ni particles suitable for batch chromatography.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
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