A new, heavier-than-water silicone oil: a solution of perfluorohexyloctane in polydimethylsiloxane.

PURPOSE: To pre p a re and explore new solutions of semifluorinated alkane in silicone oil, which have a specific gravity slightly higher than silicone oil and vitreous fluid (referred to in the following as heavier-than-water silicone oils (HWSs), and to investigate, in vitro, whether HWSs can be used to plug retina holes, while allowing dehydration of the subretinal space. METHODS: HWS solutions were pre p a red with silicone oil 5000 and perfluorohexyloctane (F6H8). The stability was investigated under different conditions. The viscosity was determined by means of a capillary viscometer. The surface and interface tension were measured using the ring method. RESULTS: HWSs are insoluble in an aqueous medium. Densiron(R)68 (HWS 1.06) is a transparent homogeneous liquid which is slightly heavier (1.06 g/cm3) than water and has a refractive index close to that of vitreous liquid. Densiron68 (HWS 1.06) has a low viscosity (1480 mPas) and interface tension (40.82 mN/m), making it an effective tamponade in the surgical treatment of an inferior detached retina. In addition, the interfaces between Densiron68 and other perfluorocarbon liquids are clearly visible. However, the interface layer between Densiron68 and water is not clear. Finally, all HWSs are stable over the long term at ambient temperatures, as well as physically and thermally resistant. CONCLUSIONS. Due to its physiochemical properties, Densiron68 could meet the requirements for a heavier-than-water tamponade.

[Substances for staining biological tissues: use of dyes in ophthalmology]. / Substanzen zur Anfärbung von biologischem Gewebe -- Farbstoffe in der Ophthalmologie.

The azo dye trypan blue and the cyanine dye indocyanine green have been used in ophthalmology since the 1980 s to dye the anterior capsule in cataract operations and to stain epiretinal membranes in order to remove the membrana limitans interna (ILM). By means of a standardized in vitro test in accordance with DIN EN ISO 10993, it has now been shown that both dyes and the theoretically possible alternatives - the anthrachinone alizarincyanine green and the trityl dyes fast green and lissamine green - are cytotoxic in the normal concentrations of maximum 1.5 g/l. On the other hand, the new product Blueron(R) with the trityl dye patent blue, which has been developed to dye the anterior capsule, is completely biocompatible, even at a high dosage of up to 2.8 g/l.

A new, heavier-than-water silicone oil: A solution of perfluorohexyloctane in polydimethylsiloxane.

PURPOSE: To pre p a re and explore new solutions of semifluorinated alkane in silicone oil, which have a specific gravity slightly higher than silicone oil and vitreous fluid (referred to in the following as heavier-than-water silicone oils (HWSs), and to investigate, in vitro, whether HWSs can be used to plug retina holes, while allowing dehydration of the subretinal space. METHODS: HWS solutions were pre p a red with silicone oil 5000 and perfluorohexyloctane (F6H8). The stabiliy was investigated under different conditions. The viscosity was determined by means of a capillary viscometer. The surface and interface tension were measured using the ring method. RESULTS: HWSs are insoluble in an aqueous medium. Densiron68 (HWS 1.06) is a transparent homogeneous liquid which is slightly heavier (1.06 g/cm3) than water and has a refractive index close to that of vitreous liquid. Densiron68 (HWS 1.06) has a low viscosity (1480 mPas) and interface tension (40.82 mN/m), making it an effective tamponade in the surgical treatment of an inferior detached retina. In addition, the interfaces between Densiron68 and other perfluorocarbon liquids are clearly visible. However, the interface layer between Densiron68 and water is not clear. Finally, all HWSs are stable over the long term at ambient temperatures, as well as physically and thermally resistant. CONCLUSIONS: Due to its physiochemical properties, Densiron68 could meet the requirements for a heavier-than-water tamponade. (Eur J Ophthalmol 2005; 15: 627-37).

A system establishment compatibility profiles for artificial oxygen carriers and other substances.

Worldwide, great efforts are being made to develop a clinically useful artificial oxygen carrier. Toxicological and immunological compatibility is generally tested using animal experiments but inflammatory parameters in particular show large species-specific differences. Therefore, we developed an in vitro system using human components to establish a compatibility profile of unknown compounds. The test system comprises induction of hemolysis, activation of complement (C3a), induction/suppression of cytokine production, influence on cell proliferation, direct toxicity on peripheral leukocytes, and phagocytosis of the material under test and of microbes. The test system will be described, along with results of various perfluorocarbon emulsions. When testing lecithin-based perfluorodecalin (PFD) emulsions, and comparing them to Pluronic-based PFD emulsions, we could show that Pluronic-based emulsions were virtually untoxic to peripheral human leukocytes. They neither inhibited cell proliferation nor caused any hemolysis, but caused mild to moderate inhibition of endotoxin-induced cytokine production. At the same time, lecithin-based PFD emulsion caused substantial cytotoxicity in phagocytic cells like monocytes (60-100% after 24 h incubation) and granulocytes (10-20% after 24 h incubation). They also suppressed endotoxin-induced cytokine production in monocytes to more than 98% and inhibited cell proliferation of an endothelial (ECV 304) and a monocytic cell line (MonoMac6) to more than 95%.

Semifluorinated symmetrical diethers for intraocular use: synthesis, characterization, and in vitro biocompatibility.

Semifluorinated symmetrical diethers were synthesized using the William ether synthesis. These diethers should have similar properties to perfluorocarbons as are chemical inertness and high oxygen solubility, but in contrast a considerably lower density. With their lower density the damaging of the choroidal tissue of the eye observed with perfluorocarbons should be avoided. The synthesized diethers are inert compounds being stable against nucleophiles, oxidiziers and strong bases. Their density is in the range of 1.1-1.2 g/cm3. Besides the physical and chemical tests we conducted several in vitro biocompatibility tests. The tests comprised induction of hemolysis, the generation of C3a complement, the influence on the production of interleukin1beta, the influence on cell proliferation of a Raji and a Hela cell line (3H-Thymidine uptake) and finally the direct cytotoxic effect on these cell lines. All tested symmetrical diethers were positive in one or more tests and can be expected to be incompatible in vivo. Especially the "short" semifluorinated diethers [(CF3CH2O)2(CH2)3-6] showed a nearly total inhibition of cell proliferation or interleukin1beta release. Further variation of the compounds will be necessary to generate better biocompatible derivates.

Semifluorinated alkanes--a new class of compounds with outstanding properties for use in ophthalmology.

Semifluorinated alkanes, R(F)R(H), have a perfluorocarbon and a hydrocarbon segment in the molecule. R(F)R(H) are physically, chemically and physiologically inert, colorless, laser stable liquids with substantially reduced densities--between 1.1 and 1.7 g/cm3--and very low surface and interface tensions. R(F)R(H) are useful for unfolding a retina or for permanent tamponade. They are soluble in perfluorocarbon liquids (PFCL), hydrocarbons and silicone oils. For the first time residues of silicone oil can be extracted from the eye because R(F)R(H) are solubilizers for PFCLs and silicone oils, so they can be used as solvents or solubilizers for drugs and medicaments. Therefore R(F)R(H) are excellent candidates for use in the ophthalmic field.

Semifluorinated alkanes A new class of compounds with outstanding properties for use in ophthalmology.

Semifluorinated alkanes, RFRH, have a perfluorocarbon and a hydrocarbon segment in the molecule. RFRH are physically, chemically and physiologically inert, colorless, laser stable liquids with substantially reduced densities - between 1.1 and 1.7 g/cm3 - and very low surface and interface tensions. RFRH are useful for unfolding a retina or for permanent tamponade. They are soluble in perfluorocarbon liquids (PFCL), hydrocarbons and silicone oils. For the first time residues of silicone oil can be extracted from the eye because RFRH are solubilizers for PFCLs and silicone oils, so they can be used as solvents or solubilizers for drugs and medicaments. Therefore RFRH are excellent candidates for use in the ophthalmic field. (Eur J Ophthalmol 2000; 10: 189-97).

A new way of removing silicone oil from the surface of silicone intraocular lenses.

PURPOSE: This study was performed to ascertain the efficacy of Perfluorhexyl-octan, C14F13H17 (F6H8), in dissolving silicone oil from the surface of silicone intraocular lenses. So far F6H8 is the only solvent of silicone oil that is tolerated by intraocular tissues. MATERIALS AND METHODS: Intraocular silicone lenses (Domilens) were examined after application of small droplets of silicone oil of two different viscosities (AdatoSIL-OL 1000 and 5000) followed by rinsing with F6H8. To allow distinction between silicone oil and F6H8 the silicone oil was stained. Microscopic examination was carried out under video control. RESULTS: One hundred microliters of AdatoSIL-OL 1000 could be easily removed with about 800 microl of F6H8; 50 microl of AdatoSIL-OL 5000 also disappeared after 800 microl of F6H8. A larger drop of the latter oil could not be removed even after application of 2 ml of F6H8. CONCLUSION: Silicone oil 1000 can be easily dissolved by F6H8, whereas silicone oil 5000 is more difficult to remove because of its higher viscosity.

Temporary vitreous gas tamponade by perfluoromethylcyclopentane.

Using perfluoromethylcyclopentane (FMCP; US patent no. 5,441,989, granted 1995) we have developed a new vitreous gas tamponade in a rabbit model that allows complete filling of the vitreous cavity without vitrectomy and without a significant increase in intraocular pressure. In humans this procedure would allow the blockage of inferior and posterior retinal holes without special positioning of the patient. Perfluoromethylcyclopentane (FMCP), a liquid perfluorocarbon with a boiling point slightly above body temperature, is injected in minute volumes into the vitreous cavity, where it vaporizes, thereby filling a gas volume approximately 500 times its liquid volume. FMCP was injected into the midvitreous in six rabbits (six eyes). After 2-3 days a complete gas tamponade was achieved in three eyes. Two eyes showed 75-90% filling, and one eye was filled only 50% with gas. Intraocular pressure was highest in the completely filled eyes, ranging from 26.6 to 38.8 mmHg. In all eyes the maximum expansion of the gas bubble lasted 2 weeks. One eye developed a retinal detachment. All eyes showed transient subcapsular cataracts. The results of this study showed that intravitreal injection of FMCP, a new perfluorocarbon liquid, results in a complete gas tamponade of the vitreous cavity which lasts 2 weeks without severe intraocular pressure rise and without vitrectomy. This procedure will be especially useful for eyes that have retinal detachment from inferior or posterior retinal holes. Injection of a conventional gas such as SF6 or C3F8 usually does not block retinal holes in inferior or posterior locations without tedious positioning and risk of (transient) glaucoma. Since the mechanism of transition of FMCP from liquid to gas in the vitreous is poorly understood, we are currently studying FMCP vaporization in an in vitro eye model.

Effects of a novel perfluorocarbon emulsion on neutrophil chemiluminescence in human whole blood in vitro.

The effects have been studied of a novel perfluorochemical (PFC) emulsion (18.5% perfluorodecalin, 1.5% perfluorodimorpholine propane, 2.5% lecithin) on phorbol 12-myristate 13-acetate (PMA; 100 micrograms ml-1)-induced neutrophil chemiluminescence in citrated human whole blood in vitro. A transient, dose-dependent, decrease in chemiluminescence, to a maximum of 54% after 12 min (P < 0.05), occurred when blood was pre-incubated with 10-40 microliters of the PFC emulsion, compared to saline controls. The mean (+/- s.e.m., n = 6) chemiluminescence of neutrophils incubated with 30 microliters emulsion at 12 min following PMA stimulation (9.5 +/- 1.3 mV) was significantly lower (P < 0.05) than control (24.2 +/- 2.2 mV). Incubation of blood with lecithin up to 16 mg ml-1 and Pluronic F-68 or Pluronic PE 6800 up to 65 mg ml-1 did not affect chemiluminescence.

Chemical and physical stability of perfluorocarbons with laser treatment.

Physical and toxicological aspects of different perfluorocarbons and semifluorinated compounds are discussed. The urgent need for ultrapurification of perfluorocarbons is demonstrated. In vitro laser treatment simulating physiological conditions of two ultrapurified perfluorocarbons used for temporary tamponade and mechanical fixation of unfolded retina in case of giant tears, and one semifluorinated diether resulted in no detectable chemical alteration. Cytotoxic examinations of both laser treated and untreated probes showed no difference in cell proliferation.

ERA-experiment "Space Biochemistry".

The general goal of the experiment was to study the response of anhydrobiotic (metabolically dormant) microorganisms (spores of Bacillus subtilis, cells of Deinococcus radiodurans, conidia of Aspergillus species) and cellular constituents (plasmid DNA, proteins, purple membranes, amino acids, urea) to the extremely dehydrating conditions of open space, in some cases in combination with irradiation by solar UV-light. Methods of investigation included viability tests, analysis of DNA damages (strand breaks, DNA-protein cross-links) and analysis of chemical effects by spectroscopic, electrophoretic and chromatographic methods. The decrease in viability of the microorganisms was as expected from simulation experiments in the laboratory. Accordingly, it could be correlated with the increase in DNA damages. The purple membranes, amino acids and urea were not measurably effected by the dehydrating condition of open space (in the dark). Plasmid DNA, however, suffered a significant amount of strand breaks under these conditions. The response of these biomolecules to high fluences of short wavelength solar UV-light is very complex. Only a brief survey can be given in this paper. The data on the relatively good survival of some of the microorganisms call for strict observance of COSPAR Planetary Protection Regulations during interplanetary space missions.

Perfluorodecalin emulsion tested for biocompatibility in macrophages by means of a magnetometric method.

The effect of a stable perfluorodecalin (FDC) emulsion, based on addition of 0.2-0.5% (W/V) of perfluoroperhydrophenanthrene and 4% egg yolk lecithin was tested for its influence on Kupffer cells in vivo by means of a magnetometric procedure in rats. It was also compared with the effect of a perfluoro-chemical emulsion (PFC) of the first generation (FluosolR-DA, FDA). While doses of 0.1 g/kg body weight of both PFCs caused a small increase of activity in these cells (as measured by an increase in a ratio factor r after magnetization), doses of 1 g/kg b.wt. led to a significant retardation of intracellular movements after FDC and FDA for two and four days, respectively. A dose of 3 g/kg b.wt. of FDC effected a significant depression for 8 days, whereas after the same dose of Fluosol-DA the intracellular motility remained depressed for as long as 32 days.

The use of semifluorinated alkanes in blood-substitutes.

Semifluorinated alkanes are useful for blood-substitutes in two different ways: as co-surfactant to stabilize emulsions with perfluorocarbons as oxygen-carrier and as oxygen-carrier instead of perfluorocarbons. Semifluorinated alkanes act as co-surfactants in low concentrations because they are enriched at the interface perfluorodecalin/water. Emulsions with semifluorinated alkanes dissolve about the same amount of oxygen as emulsions with perfluorocarbons. The stability of these emulsions depends on the nature of the alkyl and the perfluoroalkyl chain. Semifluorinated alkanes do not eliminate hydrogen fluoride under clean-up conditions of perfluorocarbons. According to toxicity tests against human carcinoma cells semifluorinated alkanes with alkyl chains are harmless in the examined range from C6 to C10.

Biocompatibility of synthetic oxygen carriers and fluorosurfactants.

A system for testing the biocompatibility of synthetic oxygen carriers is described including tests of hemolysis, complement activation and proliferation of cell lines or lymphocytes. Of 17 surfactants tested in this system, 6 were compatible in all tests while the other compounds showed individually differing patterns of incompatibility. We conclude that, in order to conduct a meaningful screening, a series of different assays has to be applied. In addition to our system, further assays, covering cytokine induction and phagocytosis should be attempted.

Biocompatibility of synthetic oxygen carriers and fluorosurfactants.

A system for testing the biocompatibility of synthetic oxygen carriers is described including tests of hemolysis, complement activation and proliferation of cell lines or lymphocytes. Of 17 surfactants tested in this system, 6 were compatible in all tests while the other compounds showed individually differing patterns of incompatibility. We conclude that, in order to conduct a meaningful screening, a series of different assays has to be applied. Addition to our system of further assays covering cytokine induction and phagocytosis should be attempted.

On the perfluorocarbon emulsions of second generation.

Perfluorocarbon-emulsions of second generation were prepared by means of new perfluorocarbons (F-dimorpholines, F-dipiperidines and F-cyclohexylmorpholine), acting both as oxygen carriers and as interfacial active compounds (IFACs). The stabilizing effect of these IFACs is interpreted and a new theory is introduced. Also new classes of fluorosurfactants were synthesized and tested for biocompatibility. In PFC mixtures compounds of the type RFRH (RF = CmF2m + 1, RH = CnH2n + 1) are acting as IFACs but also as anchor-groups for lipophilic surfactants.

Syntheses, interfacial active properties and toxicity of new perfluoroalkylated surfactants.

New surfactants have been synthesized with perfluorohexyl-groups as hydrophobic tail, a polyethyleneglycol-methylether as hydrophilic head and a prolongator between them. The prolongator units are -C4H8-, -C2H4OC5H10-, -C2H4OC3H6C(O)- and -CH2CH(OEt)CH2-. The surface tension, CMC and the interfacial tension water/perfluorocarbon were measured and the surface excess concentrations of the surfactant molecules were calculated. The influence of the surfactants on in vitro proliferation of human cell lines Hela and Molt 4 was investigated as a parameter for biocompatibility. The influence of the surfactants led to a reduction of cell proliferation depending on the concentration and chemical nature of the surfactant. Thus the prolongators changed the properties of the surfactants. They reduced the interfacial tension water/perfluorocarbon and improved the biocompatibility of surfactants.

On the perfluorocarbon emulsions of second generation.

For formulation of perfluorocarbon-emulsions (PFC-emulsions) of second generation new perfluorocarbons (F-dimorpholines, F-dipiperidines and F-cyclohexylmorpholine) were synthesized, acting both as oxygen carriers and as interfacial active compounds (IFACs). The stabilizing effect of these IFACs is interpreted and a new theory is introduced. Also new classes of fluorosurfactants were synthesized and tested for biocompatibility. In PFC mixtures compounds of the type RFRH (RF = CmF2m + 1, RH = CnH2n + 1) are acting as IFACs but also as anchor-groups for lipophilic surfactants.