Peripherally inserted central venous catheters and central venous catheters related thrombosis in post-critical patients.

BACKGROUND: Peripherally inserted central venous catheters (PICC) have been proposed as an alternative to central venous catheters (CVC). The aim of this study was to determine the thrombosis rate in relation to PICC placement in patients discharged from the intensive care unit (ICU). METHODS: Data of patients admitted to the ICU (Careggi Teaching Hospital, Florence, Italy; January-August 2008) and discharged with a central venous device were sequentially studied. During the first 4 months, CVCs were used (CVC group), whereas during the last 4 months, PICCs were used (PICC group). Demographic/clinical and catheter-related data were collected. Intensivists performed Doppler examination at ICU discharge and 7, 15, and 30 days after placement. RESULTS: Data of 239 patients were analyzed (125 of CVC group, 114 of PICC group). A total of 2,747 CVC-days and 4,024 PICC-days of observation were included. Patient characteristics were comparable between groups. Patients with PICC had a significantly higher incidence rate of deep venous thrombosis (DVT) than patients with CVC (27.2 vs. 9.6%, P = 0.0012). The rate of DVT/1,000 catheter days was 4.4 for CVCs and 7.7 for PICCs. Eighty percent of DVTs occurred within 2 weeks after insertion. Binary logistic analysis showed a two-fold increased risk for women and a three-fold increased risk when using the left basilic vein in the PICC group. CONCLUSIONS: In our post-critically ill population, PICCs were associated with a higher rate of DVT complications than CVCs. Routine ultrasound surveillance for the first 2 weeks after patient discharge from the ICU with a PICC and preferential use of CVC for these patients may be warranted.

Study of bradykinin conformation in the presence of model membrane by Nuclear Magnetic Resonance and molecular modelling.

The conformation of bradykinin (BK), Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9, was investigated by Nuclear Magnetic Resonance (NMR) spectroscopy and Monte Carlo simulation in two different media, i.e. in pure aqueous solution and in the presence of phospholipid vesicles. Monolamellar liposomes are a good model for biological membranes and mimic the environment experienced by bradykinin when interacting with G-protein coupled receptors (GPCRs). The NMR spectra showed that lipid bilayers induced a secondary structure in the otherwise inherently flexible peptide. The results of ensemble calculations revealed conformational changes occurring rapidly on the NMR time scale and allowed for the identification of different families of conformations that were averaged to reproduce the NMR observables. These structural results supported the hypothesis of the central role played by the peptide C-terminal domain in biological environments, and provided an explanation for the different biological behaviours observed for bradykinin

Electron spin resonance spectroscopy in drug delivery.

The finding of non-viral carriers for the delivery and release of pharmaceutical and biological compounds to ill organs and tissues is one of the most widely investigated topic in medicinal and biological chemistry in the last decades. Prior to being used as drug vehicles in the living organisms, all of the new carriers are required to be fully characterized from a physico-chemical point of view, with respect to stability, charge, size, mobility, etc. To this aim, several molecular and bulky techniques have been employed for characterization. This review considers the results obtained with a molecularly oriented spectroscopic method, i.e. electron spin resonance (ESR). The application of this technique in its various forms derived from continuous-wave (cw-ESR) and pulsed-wave (pw-ESR) modes are reviewed. In particular, carriers such as liposomes (intended for gene therapy, boron neutron capture therapy, oxymetry, and others), micelles, hydrogels, nanoparticles, dendrimers, cyclodextrins and cucurbit[n]urils are considered.

Insertion of a magnesium(II)-octacarboranyl(hexylsulfanyl) porphyrazine into liposomes: a physico-chemical study.

The synthesis, characterization and liposome insertion of a novel magnesium(II) carboranyl-porphyrazine, i.e. [2,3,7,8,12,13,17,18-octakis-(1,2-dicarba-closo-dodecaboranyl)-hexylthio-5,10,15,20-porphyrazine]magnesium(II) complex, MgHECSPz, are described. MgHECSPz was designed to improve the potentiality in multiple approach anticancer therapy. Liposomal formulations with different surface charge were prepared as delivering agents. The obtained loaded vectors were characterized by DLS, SAXS, SANS and zeta potential measurements in order to define the overall properties and structural details of loaded liposomes.

Effect of the preparation procedure on the structural properties of oligonucleotide/cationic liposome complexes (lipoplexes) studied by electron spin resonance and Zeta potential.

Lipoplexes with different surface charge were prepared from a short oligonucleotide (20 mer, dsAT) inserted into liposomes of 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE). The starting liposomes were prepared by two different procedures, i.e. progressive dsAT addition starting from plain liposomes (titration) and direct mixing of dsAT with pure liposomes (point to point preparation). Lipoplexes were characterized from a molecular point of view by Electron Spin Resonance (ESR) of a cationic spin probe and by Nuclear Magnetic Resonance. Structural and surface features were analysed by Zeta potential (zeta) measurements and Cryo-TEM micrographs. The complete set of results allowed to demonstrate that: i) the interactions between dsAT and cationic lipids were strong and occurred at the liposome surface; ii) the overall shape and physicochemical properties of liposomes did not change when short nucleic acid fragments were added before surface charge neutralization; iii) the bilayer structure of the lipids in lipoplexes was substantially preserved at all charge ratios; iv) the physical status of lipoplexes with electrical charge far from neutrality did not depend on the preparation method.

Small angle scattering and zeta potential of liposomes loaded with octa(carboranyl)porphyrazine.

In this work, the physicochemical characterization of liposomes loaded with a newly synthesized carboranyl porphyrazine (H2HECASPz) is described. This molecule represents a potential drug for different anticancer therapies, such as boron neutron capture therapy and for photodynamic therapy or photothermal therapy. Different loading methods and different lipid mixtures were tested. The corresponding loaded vectors were studied by small angle scattering, light scattering, and zeta potential. The combined analysis of structural data at various lengths of scales and the measurement of the surface charge allowed us to obtain a detailed characterization of the investigated systems. The mechanisms underlying the onset of differences in relevant physicochemical parameters (size, polydispersity, and charge) were also critically discussed.

DOTAP/DOPE and DC-Chol/DOPE lipoplexes for gene delivery studied by circular dichroism and other biophysical techniques.

Cationic liposomes give rise to stable complexes with DNA molecules (lipoplexes) that are of great interest for gene delivery applications. In particular, liposomes made up by a cationic lipid (DOTAP or DC-Chol) and a zwitterionic lipid (DOPE), produce stable adducts with single and double-stranded DNA oligonucleotides. Formation of these lipoplexes has been further addressed here by circular dichroism spectroscopy (CD) and by other independent biophysical methods. Titration of DNA oligonucleotides with cationic liposomes resulted into significant modifications of their circular dichroic bands. Such spectral modifications were ascribed to progressive DNA condensation and loss of native conformation, as a consequence of the electrostatic interactions taking place between the phosphate groups of DNA and the positively charged head groups of cationic lipids. In all cases, the loss of the CD feature characteristic of the native DNA conformation closely matched the inflection point of Zeta potential profiles. The resulting adducts showed peculiar and non-canonical CD spectra, while exhibiting appreciable stability at physiological pH.

Solution behavior of a sugar-based carborane for boron neutron capture therapy: a nuclear magnetic resonance investigation.

The physico-chemical properties of beta-lactosyl-closo-orthocarborane in water solution were investigated by multinuclear NMR, (13)C NMR relaxation, and ab-initio calculations. This molecule represents a potentially selective boron carrier in Boron Neutron Cancer Therapy (BNCT) and exhibits amphiphilic characteristics. Its structural and dynamic features were studied comparing NMR data acquired in both aggregating and non-aggregating conditions. Aggregates are characterized by rapid exchange with the bulk and by high sensitivity to temperature conditions. An unusually stable intra-molecular CH...O hydrogen bond was found to persist in water solution both for the free molecules and after aggregate formation. At the same time, inter-molecular specific CH()O interactions do not seem effective in the aggregate formation process, which appears to take place only on non-specific hydrophobic basis.

Physico-chemical characterization and transfection efficacy of cationic liposomes containing the pEGFP plasmid.

Cationic liposomes-DNA complexes (lipoplexes) are largely used in gene delivery. Deciphering specific chemical and physical properties of lipoplexes is a necessary step to unravel the mechanisms underlying transfection and to improve transfection efficacy in each experimental model. In the present paper we investigated the physico-chemical features of lipoplexes containing a plasmid encoding for the GFP protein, in order to correlate these results with transfection efficacy. Cationic unilamellar vesicles (mean diameter 100 nm) were prepared, from the cationic DC-Chol lipid and the zwitterionic phospholipid DOPE. The two components of the liposome bilayer were used at molar ratio close to unity. ESR spectra were recorded and zeta potential zeta was measured on liposomes complexed with the plasmid. One of the main points of interest in this paper resided in the fact that both kinds of measurements were carried out in the same conditions (i.e. lipid concentration, medium composition, and pH) employed for cell transfection experiments. Transfection was performed on CHO cells; the percentage of fluorescent cells was evaluated and compared with the above physico-chemical features. It emerged that the composition and pH of the medium, the lipoplex/cell ratio, as well as the amount of lipoplex added to the cell culture were critical parameters for transfection efficacy. Finally, lipoplex surface charge played a fundamental role to achieve a high transfection level.

ESR as a valuable tool for the investigation of the dynamics of EPC and EPC/cholesterol liposomes containing a carboranyl-nucleoside intended for BNCT.

Electron Spin Resonance (ESR) spectroscopy of long-chain nitroxides (5-, 7-, and 16-doxyl stearic acid) has been used to evaluate the perturbations induced by beta-5-o-carboranyl-2'-deoxyuridine (CDU) on the structure and dynamics of egg phosphatidylcholine (EPC) and EPC/cholesterol liposomes. Loaded liposomes are intended for the use in Boron Neutron Capture Therapy (BNCT). From a detailed analysis of the motional and order parameters determining the ESR line shape as a function of temperature and of CDU content in liposomes, an increased order and a hindered motion of the phospholipid membranes resulted in the presence of increasing CDU concentration. This occurred particularly at the liposome surface level. Both higher ordering and increased rigidity of the membrane lipids were the result of the constraints exerted by the embedded carboranyl-nucleoside.

Boronphenylalanine insertion in cationic liposomes for Boron Neutron Capture Therapy.

Cationic liposomes are widely used as carriers of biomolecules specifically targeted to the cell nucleus. p-Boronphenylalanine (BPA) is a powerful anti-tumor agent for Boron Neutron Capture Therapy (BNCT). In this paper, (1)H and (13)C NMR was used to study the insertion of BPA in mixed liposomes, made up by the positively charged 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) and the zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE). The boronated drug was distributed between the water phase and the liposomes. The location site of BPA into the lipid bilayer was investigated and the boron-substituted aromatic ring was found inserted in the hydrophobic region, whereas the amino acidic group was oriented towards the aqueous environment. Further information was given by proton spin-lattice relaxation rates.

Association of sugar-based carboranes with cationic liposomes: an electron spin resonance and light scattering study.

The possibility of cationic (di-oleoyltrimethylammonium propane, DOTAP)/(L-alpha-dioleoylphosphatidyl-ethanolamine, DOPE) liposomes to act as carriers of boronated compounds such as 1,2-dicarba-closo-dodecaboran(12)-1-ylmethyl](beta-D-galactopyranosyl)-(1-->4)-beta-D-glucopyranoside and 1,2-di-(beta-D-gluco-pyranosyl-ox)methyl-1,2-dicarba-closo-dodeca-borane(12) has been investigated by Electron Spin Resonance (ESR) of n-doxyl stearic acids (n-DSA) and Quasi-Elastic Light Scattering (QELS). Both these carboranes have potential use in Boron Neutron Capture Therapy (BNCT), which is a targeted therapy for the treatment of radiation resistant tumors. They were shown to give aggregation both in plain water and in saline solution. Carborane aggregates were, however, disrupted when DOTAP/DOPE liposome solutions were used as dispersing agents. The computer analysis of the ESR spectra from carborane-loaded liposomes allowed to establish an increase of the order degree in the liposome bilayer with increasing carborane concentration, together with a decreased mobility. The same discontinuities of both correlation time and order parameter with respect to temperature variations were observed in carborane-containing and carborane-free liposomes. This suggested that a homogeneous dispersion of nitroxides and carboranes occurred in the liposome bilayer. The ESR line shape analysis proved that no dramatic changes were induced in the liposome environment by carborane insertion. QELS data showed that the overall liposome structure was preserved, with a slight decrease in the mean hydrodynamic radius and increase in polydispersity caused by the guest molecules.

DOTAP/DOPE and DC-Chol/DOPE lipoplexes for gene delivery: zeta potential measurements and electron spin resonance spectra.

Non-viral vectors represent an important alternative in gene delivery. Among these vectors, cationic liposomes are widely studied, because of their ability to form stable complexes with DNA fragments (lipoplexes). In the present work, we report on the characterization by electron spin resonance (ESR) spectroscopy and zeta potential measurements of cationic liposomes and of their complexes with oligonucleotides. Liposomes were made with a zwitterionic lipid, DOPE, and a cationic lipid, either DOTAP or DC-Chol. Oligonucleotides were the 20-base single strand polyA, the 20-base single strand polyT, and the corresponding double strand dsAT. The zeta potential as a function of the oligonucleotide/lipid+ ratio gave an S-shaped titration curve. Well-defined surface potential changes took place upon charge compensation between the cationic lipid heads and the phosphate groups on the oligonucleotides. The inversion point depended on the specific system under study. The bilayer properties and the changes that occurred with the incorporation of DNA fragments were also monitored by ESR spectroscopy of appropriately tailored spin probes. For all the systems investigated, the ESR spectra showed that no major alteration took place after lipoplex formation and molecular packing remained substantially unchanged. Both zeta potential and ESR measurements were in favor of an external mode of packing of the lipoplexes.

Evidences of strong C-H...O bond in an o-carboranyl beta-lactoside in solution.

In this communication, the presence of a persistent intramolecular C-H....O bond in solution, has been evidenced by NMR spectroscopy and theoretical calculations. The molecules under study were o-carboranyl beta-glycoside derivatives, in which, the donor group was the activated CH of the carboranyl residue and the acceptor atom was the glycosidic oxygen. The strength of the interaction and the geometry of the atoms involved were determined by ab initio calculations.