3D Visualisation of Navigation Catheters for Endovascular Procedures Using a 3D Hub and Fiber Optic RealShape Technology: Phantom Study Results

Objective

Fiber Optic RealShape (FORS) is a new technology that visualises the full three dimensional (3D) shape of guidewires using an optical fibre embedded in the device. Co-registering FORS guidewires with anatomical images, such as a digital subtraction angiography (DSA), provides anatomical context for navigating these devices during endovascular procedures. The objective of this study was to demonstrate the feasibility and usability of visualising compatible conventional navigation catheters, together with the FORS guidewire, in phantom with a new 3D Hub technology and to understand potential clinical benefits.

Methods

The accuracy of localising the 3D Hub and catheter in relation to the FORS guidewire, was evaluated using a translation stage test setup and a retrospective analysis of prior clinical data. Catheter visualisation accuracy and navigation success was assessed in a phantom study where 15 interventionists navigated devices to three pre-defined targets in an abdominal aortic phantom using an Xray or computed tomography angiography (CTA) roadmap. Additionally, the interventionists were surveyed about the usability and potential benefits of the 3D Hub.

Results

The location of the 3D Hub and catheter along the FORS guidewire was detected correctly 96.59% of the time. During the phantom study, all 15 interventionists successfully reached the target locations 100% of the time and the error in catheter visualisation was 0.69 mm. The interventionists agreed or strongly agreed that the 3D Hub was easy to use and the greatest potential clinical benefit over FORS is in offering interventionists choice over which catheter they used.

Conclusion

This set of studies has shown that FORS guided catheter visualisation, enabled by a 3D Hub, is accurate and easy to use in a phantom setting. Further evaluation is needed to understand the benefits and limitations of the 3D Hub technology during endovascular procedures.

Characterization of atmospheric particulate: relationship between chemical composition, size, and emission source

Physicochemical characterization of particulate matter fractionated into eight samples by size from 10 to 0.43 microm was performed by HS-SPME/GC-MS for the organic (semi-)volatile components and SEM X-ray microanalysis (SEM/EDX) for analysis of the elemental composition. The HS-SPME technique was shown to be efficient with respect to requiring an extremely low amount of material, being selective and clean and avoiding use of any solvents. Particulate matter was collected at four sites characterized by particular environmental locations and different pollution levels around the city of L'Aquila in central Italy. The results reveal a tight correlation between the particle composition, size, and the emission source. The analyses show also that the finer the particle, the higher its content of elemental carbon and organic compounds. Well-known carcinogens such as PAHs were detected among the identified organic compounds from both the rural and highly polluted sites.

A new microperoxidase from Marinobacter hydrocarbonoclasticus

The preparation and characterization of a new microperoxidase obtained from proteinase K-treated cytochrome c(552) from Marinobacter hydrocarbonoclasticus (previously known as Pseudomonas nautica) are presented. This microperoxidase (MMP-5) has novel structural properties relative to previously reported microperoxidases, as the two intervening amino acid (X) residues within the consensual CXXCH c-type heme binding motif are missing, yielding a heme-pentapeptide with increased solubility in aqueous solvents and a 1-2 order of magnitude higher stability of the monomeric state relative to canonical microperoxidases. The electronic spectra in the near-UV and visible regions have been studied as a function of MMP-5 concentration and pH. The spectroscopic properties of MMP-5 are typical of microperoxidases with high-spin hexa- or pentacoordinate heme species dominant in the 1-8 pH range and low-spin states prevailing at higher pH values. In the presence of hydrogen peroxide, MMP-5 displays peroxidatic activities towards several compounds.

Molecular recognition by mass spectrometry

A recent major advance in the field of mass spectrometry in the biomolecular sciences is represented by the study of the supramolecular interactions among two or more partners in the gas phase. A great deal of chemistry and most of biochemistry concerns molecular interactions taking place in solution. The electrospray technique, which allows direct sampling from solution, and soft ionization of the solute without deposition into the analyte of large amounts of energy, guarantees in many cases the survival of noncovalent bondings and, hence, the direct analysis of the supramolecular complexes present in the condensed phase. The proper preparation of the solution to be studied and also the expert and accurate setting and use of the instrumental parameters are the prerequisites for gaining results as to the specific interactions between, for instance, a protein conformationally modified by its specific metal ion, eventually, and a ligand molecule. The analysis of the charge state of the protein itself and of the modifications of the complex integrity by activating collisions are also methods for studying the biomolecule-molecule interactions. Accordingly, this new mass spectrometric approach to the supramolecular chemistry, which could be also defined as 'supramolecular mass spectrometry', allows the study of ion-protein, protein-protein, protein-ligand and DNA-drug interactions. Chiral recognition can also be performed in the gas phase, studying by electrospray mass spectrometry the fragmentation of diastereomeric complex ions. Not the least, a deep insight can also be obtained into the formation and nature of inclusion complexes like those formed with crown ethers, cyclodextrins and calixarenes as host molecules. All these topics are treated to a certain extent in this special feature article.

Characterization of a novel microperoxidase from Marinobacter hydrocarbonoclasticus by electrospray ionization tandem mass spectrometry

Microperoxidases are small heme-peptides obtained by proteolytic digestion of cytochrome c, exhibiting peroxidase activity. They consist of a short- or medium-length polypeptide chain, covalently linked to an iron protoporphyrin IX moiety via two thioether bonds involving Cys residues at the c-porphyrin A and B pyrrole rings. These small molecules are interesting for a wide range of possible applications. We have structurally characterized, by means of electrospray ionization (ESI) mass and tandem mass spectrometric experiments, a novel microperoxidase called MMP-5 (Marinobacter MicroPeroxidase-5), obtained by proteolytic digestion of cytochrome c552, a monoheminic electron-transfer protein isolated from Marinobacter hydrocarbonoclasticus. This microperoxidase, which still maintains the functional peptide moieties for peroxidase activity, is devoid of the two amino acids intercalating the Cys residues linked to the c-porphyrin, thus increasing its water solubility. Once submitted to the ESI source potential, MMP-5 showed an interesting tendency for the reduction of the iron protoporphyrin substructure. This behaviour was clearly evidenced by the mass shift exhibited by the reduced form.

Mass spectrometry in the biosynthetic and structural investigation of lignins

Lignin, a resistant cell-wall constituent of all vascular plants that consists of ether and carbon-linked methoxyphenols, is still far from being structurally described in detail. The main problem in its structural elucidation is the difficulty of isolating lignin from other wood components without damaging lignin itself. Furthermore, the high number and variegated forms of linkages that occur between the monomeric units and the chemical resistance of certain ether bonds limit the extent to which analytical and degradation procedures can be used to elucidate the lignin structure. Most of our present knowledge about the molecular structure of lignin is based on the analysis of monomers, dimers or, at the most, tetramers of degraded isolated lignins. Mass spectrometry (MS), which offers advantages in terms of speed, specificity, and sensitivity, has revealed to be a very powerful technique in the structural elucidation of lignins, in combination with the great number of chemical and thermal degradation methods available in the study of lignin. Moreover, the recent development of new ionization techniques in MS-electrospray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-MS-has provided new possibilities to also analyze the undegraded lignin macromolecule.

Investigation by solid-phase microextraction and gas chromatography/mass spectrometry of trail pheromones in ants

The Dufour's gland content of workers of two ant species of the genus Messor has been analyzed by solid-phase microextraction and gas chromatography with mass spectrometry (GC/MS). The structures of the compounds in the pheromonal mixtures have been determined. In both cases only one intact gland, inserted in a properly dimensioned capillary vial, is sufficient to produce a clean and fully interpretable GC/MS profile. It is worth noting that, for the first time in Messor ants, farnesol has been detected as a minor component of glandular secretion in Messor capitatus.

ESI-MS in the study of the activity of α-chymotrypsin in aqueous surfactant media

The catalytic activity of alpha-chymotrypsin on a model and a peptide substrate, in the supramolecular system "enzyme-surfactant" in water solution, has been studied by electrospray ionization mass spectrometry. Hydrolysis of N-succinyl-L-phenylalanine p-nitroanilide as the model compound, catalysed by alpha-chymotrypsin in the presence of monomeric cetyltributylammonium bromide, has been followed by UV and ESI-MS detection. Kinetic data, which are essentially identical independent of their determination techniques, show a twelve fold improvement of the enzyme catalytic efficiency when compared with the reaction carried out in the absence of the additive. Once validated, the ESI-MS technique was used to study the hydrolytic activity of the enzyme on a peptide substrate like substance P: it is worth emphasising that the spectrophotometric detection cannot be employed on peptides, where the chromophores are untouched by the hydrolytic process. Substance P hydrolyses in aqueous surfactant following dichotomic kinetics, which are initially rapid but then slow down as the reaction progress. The results presented in this paper are expected to extend studies on biocatalysis in aqueous surfactant media to a wide range of substrates, independent of their spectroscopic properties.

Investigation by solid-phase microextraction and gas chromatography/mass spectrometry of secondary metabolites in lichens deposited on stone monuments

Lichens are ubiquitous organisms formed by symbiotic associations of fungal hyphas and algae that also grow under often extreme environmental conditions. They produce secondary metabolites, the so-called lichen substances, whose structural characterization can give an important contribution to lichen taxonomy. Lichens are also widely employed as biomonitors of atmospheric pollution; being epiphyte organisms they tend, in fact, to accumulate exogenous compounds. Moreover, it could be questioned if the environmental stress alters their secondary metabolites production. Therefore, a new strategy for the analysis of the organic substances absorbed or metabolized by lichens has been developed. This method exploits the dry solid-phase microextraction (SPME) headspace technique coupled with gas chromatography/mass spectrometry (GC/MS). Lichens coating the stone surfaces of monuments, located in small towns between high mountains and far away from urban environments, have been investigated. In the field of cultural heritage, this study can contribute to the knowledge of the state of conservation of outdoor exposed historical monuments.

The first gas chromatographic resolution of carnitine enantiomers

The enantiomers of carnitine are converted on-line in the injection port of a gas chromatograph into beta-hydroxy-gamma-butyrolactones and are separated on a derivatized beta-cyclodextrin chiral stationary phase.