Interfacial Nanoprecipitation toward Stable and Responsive Microbubbles and Their Use as a Resuscitative Fluid

A new approach has been developed to prepare stable microbubbles (MBs) by interfacial nanoprecipitation of bioabsorbable polymers at air/liquid interfaces. This facile method offers robust control over the morphology and chemophysical properties of MBs by simple chemical modifications. This approach is amenable to large‐scale manufacturing, and is useful to develop functional MBs for advanced biomedical applications. To demonstrate this, a MB‐based intravenous oxygen carrier was created that undergoes pH‐triggered self‐elimination. Intravenous injection of previous MBs increased the risk of pulmonary vascular obstruction. However, we show, for the first time, that our current design is superior, as they 1) yielded no evidence of acute risks in rodents, and 2) improved the survival in a disease model of asphyxial cardiac arrest (from 0 to 100 %), a condition that affects more than 100 000 in‐hospital patients, and carries a mortality of about 90 %.     

Configurational Isomerism in Polyoxovanadates

A water‐soluble derivative of the polyoxovanadate {V₁₅E₆O₄₂} (E=semimetal) archetype enables the study of cluster shell rearrangements driven by supramolecular interactions. A reaction unique to E=Sb, induced exclusively by ligand metathesis in peripheral [Ni(ethylenediamine)₃]²⁺ counterions, results in the formation of the metastable α₁* configurational isomer of the {V₁₄Sb₈O₄₂} cluster type. Contrary to all other polyoxovanadate shell architectures, this isomer comprises an inward‐oriented vanadyl group and is ca. 50 and 12 kJ mol^?1 higher in energy than the previously isolated α and β isomers, respectively. We discuss this unexpected reaction in light of supramolecular Sb?O???V and Sb?O???Sb contacts manifested in {V₁₄Sb₈O₄₂}₂ dimers detected in the solid state. ESI MS experiments confirm the stability of these dimers also in solution and in the gas phase. DFT calculations indicate that other, as of yet elusive isomers of {V₁₄Sb₈}, might be accessible as well.     

Optimizing Antimicrobial Peptide Dendrimers in Chemical Space

We used nearest‐neighbor searches in chemical space to improve the activity of the antimicrobial peptide dendrimer (AMPD) G3KL and identified dendrimer T7 , which has an expanded activity range against Gram‐negative pathogenic bacteria including Klebsiellae pneumoniae, increased serum stability, and promising activity in an in vivo infection model against a multidrug‐resistant strain of Acinetobacter baumannii. Imaging, spectroscopic studies, and a structural model from molecular dynamics simulations suggest that T7 acts through membrane disruption. These experiments provide the first example of using virtual screening in the field of dendrimers and show that dendrimer size does not limit the activity of AMPDs.     

Enzymatic determination of phenols using peanut peroxidase

The influence of phenol and its derivatives on the kinetics of oxidation of aryldiamines (indicator-substrates) catalyzed by novel plant peroxidase—cationic peanut peroxidase—was studied. The character of influence of phenols on the kinetics of enzymatic oxidation of benzidine, o-dianisidine, and 3,3′,5,5′-tetramethylbenzidine (TMB) with hydrogen peroxide was found to depend on a correlation between redox properties of phenols and the indicator-substrate of peroxidase. Thus, the catalytic activity of peanut peroxidase is inhibited by phenols with redox potentials higher than that of aryldiamines mentioned above, whereas phenols with potentials below those of aryldiamines, play the role of second substrates of the enzyme. The enzymatic procedures for the determination of numerous phenols on the level of their concentrations 0.05–80 μM were developed using the reactions of benzidine, o-dianisidine, and TMB oxidation. Different analytical signals—the indicator reaction rate and the induction period duration—were used for the determination of phenols, belonging to various groups—the inhibitors and second substrates of the enzyme, respectively.     

Infrared and Raman spectra, conformational stability, ab initio calculations, and vibrational assignments for methylaminothiophosphoryl difluoride

Infrared spectra (4000–50 cm⁻¹) of the vapor, amorphous and crystalline solids and Raman spectra (3600–10 cm⁻¹) of the liquid with qualitative depolarization data as well as the amorphous and crystalline solids of methylaminothiophosphoryl difluoride, CH₃N(H)P(=S)F₂, and three deuterated species, CD₃N(H)P(=S)F₂, CH₃N(D)P(=S)F₂, and CD₃N(D)P(=S)F₂, have been recorded. The spectra indicate that in the vapor, liquid and amorphous solid a small amount of a second conformer is present, whereas only one conformer remains in the low temperature crystalline phase. The near-infrared spectra of the vapor confirms the existence of two conformers in the gas phase. Asymmetric top contour simulation of the vapor shows that the trans conformer is the predominant vapor phase conformer. From a temperature study of the Raman spectrum of the liquid the enthalpy difference between the trans and near-cis conformers was determined to be 368±15 cm⁻¹ (4.41±0.2 kJ/mol), with the trans conformer being thermodynamically preferred. Ab Initio calculations with structure optimization using the 6-31G(d) and 6-311+G(d,p) basis sets at the restricted Hartree–Fock (RHF) and/or with full electron correlation by the perturbation method to second order (MP2) support the occurrence of near-trans (5° from trans) and near-cis (20° from cis) conformers. From the RHF/6-31G(d) calculation the near-trans conformer is predicted to be the more stable form by 451 cm⁻¹ (5.35 kJ/mol) and from the MP2/6-311+G(d,p) calculation by 387 cm⁻¹ (4.63 kJ/mol). All of the normal modes of the near-trans rotamer have been assigned based on infrared band contours, depolarization values and group frequencies and the assignment is supported by the normal coordinate calculation utilizing harmonic force constants from the MP2/6-31G(d) ab initio calculations.     

Lipophilicity in PK design: methyl, ethyl, futile

Lipophilicity, often expressed as distribution coefficients (log D) in octanol/water, is an important physicochemical parameter influencing processes such as oral absorption, brain uptake and various pharmacokinetic (PK) properties. Increasing log D values increases oral absorption, plasma protein binding and volume of distribution. However, more lipophilic compounds also become more vulnerable to P450 metabolism, leading to higher clearance. Molecular size and hydrogen bonding capacity are two other properties often considered as important for membrane permeation and pharmacokinetics. Interrelationships among these physicochemical properties are discussed. Increasing size (molecular weight) often gives higher potency, but inevitably also leads to either higher lipophilicity, and hence poorer dissolution/solubility, or to more hydrogen bonding capacity, which limits oral absorption. Differences in optimal properties between gastrointestinal absorption and uptake into the brain are addressed. Special attention is given to the desired lipophilicity of CNS drugs. In examples using -blockers, Ca channel antagonists and peptidic renin inhibitors we will demonstrate how potency and pharmacokinetic properties need to be balanced.     

Fluorescence imaging and spectroscopy of ethyl nile blue A in animal models of (pre)malignancies

Discrimination between normal and premalignant tissues by fluorescence imaging and/or spectroscopy may be enhanced by a tumor-localizing fluorescent drug. Ethyl Nile Blue A (EtNBA), a dye with no phototoxic activity, was investigated for this purpose. The pharmacokinetics and tissue-localizing properties were investigated in a rat palate model with chemically induced premalignant mucosal lesions (0.5 mg/kg EtNBA intravenous [i.v.]), a hairless mouse model with UVB-induced premalignant skin lesions (1 mg/kg EtNBA intraperitoneal) and in a rat skin-fold observation chamber model on the back of a rat with a transplanted solid tumor (2.5 mg/kg EtNBA i.v.). Fluorescence images and spectra were recorded in vivo (600 nm excitation, 665-900 nm detection) and in frozen tissue sections at several time points after EtNBA administration. In the rat palate the EtNBA fluorescence was maximum almost immediately after injection, whereas in the mouse skin and the observation chamber the fluorescence maximum was reached between 2 and 3 h after injection. EtNBA cleared from tissues after 8-24 h. EtNBA localizes in the transplantable solid tumor, but is not targeted specifically to the dysplastic location in the rat palate and mouse skin. However, in the rat palate the EtNBA fluorescence increased significantly with increasing dysplasia, apparently due to the increasing thickness of the upper keratinized layer of the epithelium where the dye was found to localize. Localization in this layer occurred both in the rat palate and in hairless mouse skin.     

Gas chromatography/combustion/isotope-ratio-monitoring mass spectrometric analysis of methylboronic derivatives of monosaccharides: a new method for determining natural 13C abundances of carbohydrates

Monosaccharides were derivatized using methylboronic acid and N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA), and the delta13C values of these derivatives measured by gas chromatography/combustion/isotope-ratio-monitoring mass spectrometry to determine the original 13C-content of the monosaccharides. Comparison with the measured off-line delta13 values of the monosaccharides shows that no fractionation in 13C takes place during derivatization. The methylboronic derivatization method has proven to be a new method for natural abundance isotopic analysis of intact monosaccharides (arabinose, xylose, fucose, fructose and glucose). The method is rapid, does not involve isotopic fractionation during derivatization, and gives more precise delta13C values than other methods reported. The method was successfully applied to determine the delta13C value of glucose of the freshwater alga Scenedesmus communis.     

Determination of zinc in pharmaceutical products by use of a sequential injection analysis system

A sequential injection analysis (SIA) system is proposed for the determination of zinc in pharmaceutical samples. The method is based on the spectrophotometric detection of zinc using xylenol orange as a colour reagent at 568 nm. The system can be used to monitor zinc at a frequency of 30 samples h(-1) with an average recovery of +/-98.5% and a relative standard deviation of less than 1%. A linear relationship between peak height and zinc concentration is obtained between 10 and 60 mg L(-1). The results obtained are in good agreement with those obtained by use of a standard method.     

Melanin offers protection against induction of cyclobutane pyrimidine dimers and 6-4 photoproducts by UVB in cultured human melanocytes

The goal of this investigation was to correlate the melanin content in human pigmentary cells with the generation of UVB-induced photoproducts and to examine the relationship between the melanin content and the removal of the photoproducts. Cultured melanocytes from light-skinned individuals synthesized less melanin and produced more cyclobutane pyrimidine dimers and 6-4 photoproducts upon UVB exposure than did melanocytes from black skin. Tyrosine-stimulated melanogenesis provided protection against DNA damage in both cell types. In another set of pigmented cell lines a ratio between eumelanin and pheomelanin was determined. The assessment of association between DNA damage induction and the quantity and quality of melanin revealed that eumelanin concentration correlated better with DNA protection than pheomelanin. Skin type-I and skin type-VI melanocytes, congenital nevus (CN)-derived cells and skin type-II melanocytes from a multiple-melanoma patient were grown in media with low or high L-tyrosine concentration. The cells were irradiated with 200 J/m2 UVB, and the levels of the photoproducts were determined immediately and after 6 and 24 h. Once again the induction of the photoproducts was mitigated by increased melanogenesis, and it was inversely correlated with the skin type. No significant differences were found for the removal of photoproducts in the cultures of skin types I and VI and CN cells. No indications of a delay in the removal of photoproducts in the melanocytes from the multiple-melanoma patient were found either.