Perfluorodecalin-soluble fluorescent dyes for the monitoring of circulating nanocapsules with intravital fluorescence microscopy.

Perfluorodecalin (PFD) is an established artificial oxygen carrier due to its physical capability to solve the respiratory gases oxygen and carbon dioxide. PFD-filled poly(n-butyl-cyanoacrylate) (PACA) nanocapsules are already discussed as effective artificial oxygen carriers, and their principal suitability for intravenous administration had been shown. To further elucidate their action in vivo, it is imperative to characterise their preclinical safety and particularly their biodistribution. For these purposes, intravital fluorescence microscopy would display an attractive technique in order to monitor the PACA nanocapsules in vivo, but unfortunately, it is impossible to stain the PACA nanocapsules with a fluorescent dye fulfilling special criteria required for in vivo microscopy. In order to develop such a dye, a long-chained fluorinated thiol was used to modify a BODIPY derivative that is a highly fluorescent organic compound belonging to the difluoro-boraindacene family, as well as to functionalise mesoscopic systems, such as CdSe/ZnS-quantum dots and gold nanoparticles. Furthermore, a functionalisation of porphyrin derivatives was investigated by placing divalent ions in the centre of these systems. Due to the high solubility of all synthesised dyes in PFD, it should be possible to stain PFD-filled particles in general. However, only the functionalised BODIPY derivative was suitable for in vivo monitoring of the PFD-filled PACA nanocapsules.

The necessity for the coating of perfluorodecalin-filled poly(lactide-co-glycolide) microcapsules in the presence of physiological cholate concentrations: Tetronic-908 as an exemplary polymeric surfactant.

Recently, we demonstrated that biodegradable poly(lactide-co-glycolide) (PLGA) micro- and nanocapsules with a liquid content of perfluorodecalin are principally useful for the development of artificial oxygen carriers. In order to solve a decisive and well-known problem with PLGA microcapsules, i.e. the spontaneous agglomeration of the capsules after depletion of the emulsifying agent (i.e. cholate), coating with the ABA block copolymer, Tetronic-908 was studied. After Tetronic-908 treatment at concentrations that were harmless to cultured cells, the clustering of the microcapsules was prevented, the adsorption of opsonins was decreased and the attachment to cells was inhibited, but the oxygen transport capacity of PLGA microcapsules was even increased. The present data clearly show that perfluorodecalin-filled PLGA microcapsules must be coated before decreasing the emulsifying agent cholate to physiological concentrations, in order to develop a solution that has the capabilities to function as a potential artificial oxygen carrier suspension.

Perfluorocarbon-filled poly(lactide-co-gylcolide) nano- and microcapsules as artificial oxygen carriers for blood substitutes: a physico-chemical assessment.

The physico-chemical suitability of perfluorocarbon-filled capsules as artificial oxygen carriers for blood substitutes is assessed on the example of biodegradable poly(lactide-co-gylcolide) micro- and nanocapsules with a liquid content of perfluorodecalin. The morphology of the capsules is studied by confocal laser scanning microscopy using Nile red as a fluorescent marker. The mechanical stability and the wall flexibility of the capsules are examined by atomic force microscopy. The permeability of the capsule walls in connection with the oxygen uptake is detected by nuclear magnetic resonance. It is shown that the preparation in fact leads to nanocapsules with a mechanical stability which compares well with the one of red blood cells. The capsule walls exhibit sufficient permeability to allow for the exchange of oxygen in aqueous environment. In the fully saturated state, the amount of oxygen dissolved within the encapsulated perfluorodecalin in aqueous dispersion is as large as for bulk perfluorodecalin. Simple kinetic studies are presently restricted to the time scale of minutes, but so far indicate that the permeability of the capsule walls could be sufficient to allow for rapid gas exchange.

Measures to control blood activation during assisted circulation.

Major improvements in heart assist devices have allowed prolonged mechanical circulatory support with successful subsequent weaning or heart transplantation. The contact of blood with biomaterials used in life-sustaining devices and numerous biomaterial-independent factors elicit a systemic inflammatory response, which involves activation of various plasma protein systems and blood cells. Prolonged mechanical circulatory support elicits a systemic inflammatory response and hemostatic perturbations similar to that reported during cardiopulmonary bypass. However, in the setting of prolonged assistance, time has a complex and ill-known influence on blood activation. Methods to reduce blood activation during prolonged assisted circulation are derived from cardiopulmonary bypass investigations. Improving the biocompatibility of artificial devices can be achieved either by biomaterial surface modifications, by inhibition of biologic cascades leading to blood activation, or by controlling end points of biologic cascades. However, the necessity to respect the integrity of the organism during prolonged assistance precludes most systemic interventions and limits the control of blood activation to the area of the device.

Kinetics of phosphatidylinositol-specific phospholipase C with vesicles of a thiophosphate analogue of phosphatidylinositol.

1,2-Dimyristoyloxypropane-3-thiophospho(1D-1-myo-inositol) (D-thio-DMPI) was synthesized as a substrate for the continuous spectrophotometric assay of phosphatidylinositol-specific phospholipase C (PI-PLC) from Bacillus cereus. Release of thio-diglyceride is followed by a coupled reaction with 4,4'-dithiopyridine to produce a chromophore, 4-thiopyridine, measured by its absorption at 324 nm. Sonicated vesicles of D-thio-DMPI gave sigmoidal Michaelis-Menten kinetics with PI-PLC as a function of bulk concentration of substrate (Hill plot: Vmax = 132 mumol min-1 mg-1, apparent Km = 0.115 mM, h = 1.8). Addition of dimyristoyl phosphatidylcholine (DMPC) or dimyristoyl phosphatidylmethanol to vesicles of D-thio-DMPI resulted in an initial increase in rate followed by a decrease at higher concentrations of non-substrate lipid. Binding of PI-PLC to vesicles of DMPC with 10 mol% of N-dansyl phosphatidylethanolamine was demonstrated by fluorescence resonance energy transfer from tryptophan in the enzyme to the dansyl lipid probe.

Preoperative devascularization of a circumferential osteogenic metastasis to the upper cervical spine by direct percutaneous needle puncture: a technical note.

Direct percutaneous needle puncture (DPNP) for presurgical devascularization of head and neck as well as skull base tumours is an established, yet not widespread method. We present a case of a large and highly vascularized metastasis with partial destruction of the first two cervical vertebrae and encasement of the spinal cord that was successfully treated by DPNP for preoperative devascularization after an attempted endovascular embolization had failed. The lesion was safely and effectively devascularized, which facilitated the surgical removal. The case presented illustrates the technique and furthermore demonstrates its value.