NMR metabolomics to study the metabolic response of human osteoblasts to non-poled and poled poly (L-lactic) acid

Untargeted nuclear magnetic resonance (NMR) metabolomics was employed, for the first time to our knowledge, to characterize the metabolome of human osteoblast (HOb) cells and extracts in the presence of non-poled or negatively poled poly-L-lactic acid (PLLA). The metabolic response of these cells to this polymer, extensively used in bone regeneration strategies, may potentially translate into useful markers indicative of in vivo biomaterial performance. We present preliminary results of multivariate and univariate analysis of NMR spectra, which have shown the complementarity of lysed cells and extracts in terms of information on cell metabolome, and unveil that, irrespective of poling state, PLLA-grown cells seem to experience enhanced oxidative stress and activated energy metabolism, at the cost of storage lipids and glucose. Possible changes in protein and nucleic acid metabolisms were also suggested, as well as enhanced membrane biosynthesis. Therefore, the presence of PLLA seems to trigger cell catabolism and anti-oxidative protective mechanisms in HOb cells, while directing them towards cellular growth. This was not sufficient, however, to lead to a visible cell proliferation enhancement in the presence of PLLA, although a qualitative tendency for negatively poled PLLA to be more effective in sustaining cell growth than non-poled PLLA was suggested. These preliminary results indicate the potential of NMR metabolomics in enlightening cell metabolism in response to biomaterials and their properties, justifying further studies of the fine effects of poled PLLA on these and other cells of significance in tissue regeneration strategies.     

Weber-like interactions and energy conservation

Velocity-dependent forces varying as (such as Weber force), here calledWeber-like forces, are examined from the point of view of energy conservation and it is proved that they are conservative if and only ifγ=2μ. As a consequence, it is shown that gravitational theories employing Weber-like forces cannot be conservative and also yield both the precession of the perihelion of Mercury as well as the gravitational deflection of light.     

Host–guest interactions and their role in enantioselective hydrogenation of α-keto esters: An analysis of model systems

The interaction between cinchonidine and methyl pyruvate has been proposed as the key step leading to enantiodifferentiation in the enantioselective hydrogenation of α-ketoesters. In the present work, we employ ab initio MP2/6-31G(d) and MP2/6-31G(d,p) methods to carry out an analysis of the most relevant kind of interactions operating in representative model systems. These interactions are discussed in terms of orbital superposition and dipolar interaction. When approaching H₂CO to NH₃ at distances lower than 3.4 Å, orbital superposition is the predominant interaction, while at distances above 3.4 Å, both orbital superposition and dipolar interactions may contribute to stabilization, with a small prevalence of dipolar interactions. The stabilization energy at large distances (above 4.5 Å) is very small (about 0.5 kcal mol⁻¹), probably not enough to be responsible for the enantiodifferentiation process. Semiempirical calculations on the parent systems were also unable to reveal any special interaction which could be attributed to the enantiodifferentiation process.     

Effect of lectins from Diocleinae subtribe against oral Streptococci

Surface colonization is an essential step in biofilm development. The ability of oral pathogens to adhere to tooth surfaces is directly linked with the presence of specific molecules at the bacterial surface that can interact with enamel acquired pellicle ligands. In light of this, the aim of this study was to verify inhibitory and antibiofilm action of lectins from the Diocleinaesubtribe against Streptococcus mutans and Streptococcus oralis. The inhibitory action against planctonic cells was assessed using lectins from Canavaliaensi formis (ConA), Canavalia brasiliensis (ConBr), Canavalia maritima (ConM), Canavalia gladiata (CGL) and Canavalia boliviana (ConBol). ConBol, ConBr and ConM showed inhibitory activity on S. mutans growth. All lectins, except ConA, stimulated significantly the growth of S. oralis. To evaluate the effect on biofilm formation, clarified saliva was added to 96-well, flat-bottomed polystyrene plates, followed by the addition of solutions containing 100 or 200 μg/mL of the selected lectins. ConBol, ConM and ConA inhibited the S. mutans biofilms. No effects were found on S. oralis biofilms. Structure/function analysis were carried out using bioinformatics tools. The aperture and deepness of the CRD (Carbohydrate Recognition Domain) permit us to distinguish the two groups of Canavalia lectins in accordance to their actions against S. mutans and S. oralis. The results found provide a basis for encouraging the use of plant lectins as biotechnological tools in ecological control and prevention of caries disease.     

Rolling circle amplification-templated DNA nanotubes show increased stability and cell penetration ability

DNA nanotubes hold promise as scaffolds for protein organization, as templates of nanowires and photonic systems, and as drug delivery vehicles. We present a new DNA-economic strategy for the construction of DNA nanotubes with a backbone produced by rolling circle amplification (RCA), which results in increased stability and templated length. These nanotubes are more resistant to nuclease degradation, capable of entering human cervical cancer (HeLa) cells with significantly increased uptake over double-stranded DNA, and are amenable to encapsulation and release behavior. As such, they represent a potentially unique platform for the development of cell probes, drug delivery, and imaging tools.     

Assessment of ethanol and acetonitrile in 18F-FDG preparations by means of liquid chromatography

Introduction Acetonitrile (ACN) and ethanol (EtOH) are common solvents used in radiopharmaceutical production. In accordance to official compendia, the concentration of these solvents should be assessed by gas chromatography. In the present paper, an optimized method, based on Koziorowski (2010), is validated. Methods ACN and EtOH concentrations and retention times (Rt) were obtained by a HPLC system equipped with a refractive index detector (RID), an ion exclusion column and ultrapure water as mobile phase. The methodology was validated following the ICH Q2(R1) requirements. Results The solvents EtOH and ACN were eluted at 23.22 and 26.32 minutes, respectively, with a final run time of 30 minutes. The validation parameters (accuracy, precision, linearity, specificity, robustness, detection and quantification limits) were obtained. Conclusions A reproducible HPLC method for the quantification of residual solvents in preparations of 2-deoxy-2-[fluorine-18]fluoro-D-glucose (¹⁸F-FDG) was described and validated. The method was precise, accurate, selective, robust and linear over a wide range. In addition, this method showed a high sensitivity, with limits of detection and quantitation comparable to the usual methods by gas chromatography.