High-resolution laser ablation inductively coupled plasma mass spectrometry used to study transport of metallic nanoparticles through collagen-rich microstructures in fibroblast multicellular spheroids

We have efficiently produced collagen-rich microstructures in fibroblast multicellular spheroids (MCSs) as a three-dimensional in vitro tissue analog to investigate silver (Ag) nanoparticle (NP) penetration. The MCS production was examined by changing the seeding cell number (500 to 40,000 cells) and the growth period (1 to 10 days). MCSs were incubated with Ag NP suspensions with a concentration of 5 μg mL⁻¹ for 24 h. For this study, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to visualize Ag NP localization quantitatively. Thin sections of MCSs were analyzed by LA-ICP-MS with a laser spot size of 8 μm to image distributions of ¹⁰⁹Ag, ³¹P, ⁶³Cu, ⁶⁶Zn, and ⁷⁹Br. A calibration using a NP suspension was applied to convert the measured Ag intensity into the number of NPs present. The determined numbers of NPs ranged from 30 to 7200 particles in an outer rim of MCS. The particle distribution was clearly correlated with the presence of ³¹P and ⁶⁶Zn and was localized in the outer rim of proliferating cells with a width that was equal to about twice the diameter of single cells. Moreover, abundant collagens were found in the outer rim of MCSs. For only the highest seeding cell number, NPs were completely captured at the outer rim, in a natural barrier reducing particle transport, whereas Eosin (⁷⁹Br) used as a probe of small molecules penetrated into the core of MCSs already after 1 min of exposure.

Fibroblast MCS could build up the barrier only for nanoparticles

     

Evaluation of laser ablation threshold in polymer samples using pulsed photoacoustic technique

The acoustic signals generated in solids due to interaction with pulsed laser beam is used to determine the ablation threshold of bulk polymer samples of teflon (polytetrafluoroethylene) and nylon under the irradiation from a Q-switched Nd:YAG laser at 1.06μm wavelength. A suitably designed piezoelectric transducer is employed for the detection of photoacoustic (PA) signals generated in this process. It has been observed that an abrupt increase in the amplitude of the PA signal occurs at the ablation threshold. Also there exist distinct values for the threshold corresponding to different mechanisms operative in producing damages like surface morphology, bond breaking and melting processes at different laser energy densities.     

On the preparation of 4-mercapto-azetidinones

4-Dithioazetidinone and 4.7-diaza-2-thiabicyclo[3.2.0]hept-2-en-6-one derivatives were prepared from penam-3-isocyanates, which are useful intermediates to 4-mercapto-azetidinones.     

Synthesis, modeling, and anti-tubulin activity of a D-seco paclitaxel analogue

[reaction: see text] We have previously described a model of paclitaxel-microtubule binding that led to the prediction that analogues of paclitaxel lacking any D ring could stabilize microtubules as well as paclitaxel if the substituent present at C4 did not have unfavorable steric interactions with the binding pocket. We report the synthesis of a 4-methyl paclitaxel analogue, compound 1, which bears this prediction out. Compound 1 is as potent as paclitaxel at microtubule stabilization in vitro; however, it has only about one-four-hundredth the cytotoxicity of paclitaxel.     

A systematic SAR study of C10 modified paclitaxel analogues using a combinatorial approach

A library with 63 paclitaxel analogues modified at the C10 position of paclitaxel has been prepared using parallel solution phase synthesis. Most of the C10 analogues were slightly less active than paclitaxel in the tubulin assembly assay and had reduced potency in the B16 melanoma and MCF-7 cell line cytotoxicity assays. These modifications at C10, however, did not lead to the total loss of activity, indicating that the C10 moiety of paclitaxel may not be directly involved in the drug-microtubule interactions, but could influence its binding affinity to P-glycoprotein. Approximately 50% of the analogues demonstrated better activity against the drug resistant cell line MCF7-ADR. However, the increase in activity was 10-fold at most. This result demonstrates that the cytotoxicity against this drug resistant cancer cell line is sensitive to structural changes at the C10 position of paclitaxel. It was also found that the presence of a nitrogen atom in the C10 substituent might play a role in the interaction of analogues with microtubules.     

Synthesis, characterization, DNA binding and cleavage studies of mixed-ligand Cu(II) complexes of 2,6-bis(benzimidazol-2-yl)pyridine

Four novel copper(II) complexes of the composition [CuLX] where L = 2,6-bis(benzimidazole-2yl)pyridine, X = dipyridophenazine (L₁), 1,10-phenanthroline (L₂), hydroxyproline (L₃) and 2,6-pyridine dicarboxylic acid (L₄) were synthesized and characterized by using elemental analysis, FT-IR, UV–vis, ESI-MS, molar conductance and magnetic susceptibility measurements. The complexes [CuLL₁](NO₃)₂ [1], [CuLL₂](NO₃)₂ [2], [CuLL₃](NO₃) [3] and [CuLL₄] (NO₃) [4] are stable at room temperature. In DMSO the complexes [1] and [2] are 1:2 electrolytes, [3] and [4] are 1:1 electrolytes. Based on elemental and spectral studies five coordinated geometry is assigned to all the four complexes. The interaction of four copper ion complexes with calf thymus DNA were carried out by UV–vis titrations, fluorescence spectroscopy, thermal melting and viscosity measurements .The binding constant (K_b) of the above four metal complexes were determined as 5.43 × 10⁴ M_,⁻¹ 2.56 × 10⁴ M⁻¹, 1.21 × 10⁴ M⁻¹ and 1.57 × 10⁴ M⁻¹ respectively. Quenching studies of the four complexes indicates that these complexes strongly bind to DNA, out of all complex 1 is binding more strongly. Viscosity measurements indicate the binding mode of complexes with CT DNA by intercalation through groove. Thermal melting studies also support intercalative binding. The nuclease activity of the above metal complexes shows that 1, 2 and 3 complexes cleave DNA through redox chemistry.     

Ruthenium‐Catalyzed Oxidant‐Free Allylation of Aromatic Ketoximes with Allylic Acetates at Room Temperature

Substituted aromatic ketoximes reacted efficiently with allylic acetates in the presence of {[RuCl₂(p‐cymene)]₂} and AgSbF₆ in 1,2‐dichloroethane at ambient temperature, providing ortho‐allyl aromatic ketoximes in a highly regioselective manner without an oxidant. In the reaction, the acetate group of allyl acetate acts as a base to activate the C?H bond of aromatics. Later, ortho‐allyl aromatic ketoximes were converted into ortho‐allyl aromatic ketones in the presence of HCl.     

Mannich Reactions of Cephalosporin Sulphoxides and Sulphones with Imonium Salts. An Improved Synthesis of 2-Methylene-cephalosporins

2-Methylenecephem-1-oxides (4) or -1,1-dioxides (6) can be very conveniently obtained through the use of dimethyl(methylene)imonium salts, which can be prepared in situ or in advance from bis(N,N-dimethylamino)methane (2) and a reactive acid derivative.     

Synthesis of Symmetrical Bis(5‐substituted oxadiazolyl/thiadiazolyl/triazolylmethyl)sulfones

A new class of bis(oxadiazolyl/thiadiazolyl/triazolylmethyl)sulfones were prepared by the cyclocondensation of sulfonyldiacetic acid with aryl acid hydrazide and arylmethanesulfonylacetic acid hydrazide.