United States Patent (19) 11) Patent Number: 4,859,363 Davis Et Al

United States Patent (19) 11) Patent Number: 4,859,363 Davis et al. (45) Date of Patent: Aug. 22, 1989

54 EMULSIONS OF PERFLUOROCARBONS IN (56) References Cited AQUEOUSMEDIA U.S. PATENT DOCUMENTS (75) Inventors: Stanley S. Davis, Nottingham; David 3,775,489 11/1973 Margrave et al...... 570/130 E. M. Wotton, Bristol, both of United 3,778,381 12/1973 Rosano et al...... 252/32 X Kingdom 3,823,091 7/1974 Samejima et al. ... o os e s vs 252/312 73) Assignee: I.S.C. Chemicals Limited, London, 3,911,138 10/1975 Clark, Jr...... 514/756 X United Kingdom 3,993,581 11/1976 Yokoyama et al...... 252/312 21 Appl. No.: 143,282 Primary Examiner-Richard D. Lovering Attorney, Agent, or Firm-Fleit, Jacobson, Cohn, Price, 22 Filed: Jan. 7, 1988 Holman & Stern Related U.S. Application Data (57) ABSTRACT 63 Continuation of Ser. No. 833,017, Feb. 26, 1986, aban Increased stability is conferred on oil-in-water emul doned. sions of perfluorocarbons by addition of a minor (30) Foreign Application Priority Data (0.1-5% w/v) amount of a fluorinated compound of higher boiling point than the perfluorocarbon being Feb. 26, 1985 GB United Kingdom ...... 8504916 emulsified. The added fluorinated compound is prefera 51) Int. Cl." ...... A61K9/10; A61K 31/25; bly a perfluorinated saturated polycyclic hydrocarbon. B01J 13/00 The most preferred additive is perfluoroperhydrofluo 52 U.S. C...... 252/312; 514/755; ranthene. 514/832 58) Field of Search ...... 252/312; 514/755, 832; 570/130 6 Claims, 2 Drawing Sheets U.S. Patent Aug. 22, 1989 Sheet 1 of 2 4,859,363

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O2 4,859,363 1. 2. Ostwald ripening (see e.g. Davis et al. (1981) J. Colloid EMUSONS OF PERFLUOROCARBONS IN Interface Sci. 80:508). AQUEOUSMEDIA Molecular diffusion will occur if the oil has a finite solubility in water and if the particles are very small. It This is a continuation of application Ser. No. 5 will occur even if the droplets have excellent barriers to 06/833/017, filed Feb. 26, 1986, now abandoned. coalescence but can be prevented in hydrocarbon emul This invention relates to emulsions of perfluorocar sions using mixed oil systems, that is by the addition of bons in aqueous media, to provide emulsions suitable for a very small quantity of higher boiling point material carrying oxygen or other gases, e.g. in an artificial (e.g. soyabean oil). Thus, if molecular diffusion is the blood application. 10 cause of instability in perfluorodecalin emulsions, at It has long been hypothesised that emulsions of cer tempts at creating even more effective barriers to co tain perfluorocarbons in aqueous media could constitute alescence will be to no avail. Similar considerations ideal blood substitutes, chiefly because of their inertness apply to any pure perfluorocarbon system. and their ability to transport oxygen and other life-sup porting materials around a human or animal body. 15 BRIEF DESCRIPTION OF THE DRAWINGS Normally such emulsions are formed with the aid of FIGS. 1-4 show the stability of the emulsions as a a non-ionic surface-active agent such as those known as function of the presence of C13 and C16 at different times polaxamers (as hereinafter defined) or a phosphatide and at different temperatures. (egg or soy lecithin). However a problem inherent in such emulsion tech 20 DETALED DESCRIPTION OF THE nology is the tendency of the emulsion to de-stabilize on INVENTION storage and for the emulsion droplets to grow in size. According to the present invention there is provided For some time, various workers have been studying an oil-in-water emulsion of a perfluorinated hydrocar the properties of perfluorochemicals and their potential 25 bon in an aqueous medium, wherein the emulsion is use as blood substitutes, not only for blood transfusion stabilized by the addition of a minor amount of a fluori but also for tissue oxygenation (cancer chemotherapy), nated compound of a higher boiling point than the per treatment of infarct, as scanning agents in nuclear mag fluorinated compound being emulsified. netic resonance, and for the preservation of organ trans Preferably the fluorinated compound of higher boil plants. The literature contains a wealth of information 30 ing point is a perfluorinated saturated polycyclic hydro on the preparation of various emulsion systems, the carbon, such as one of the following: properties of various fluorocarbon liquids and their perfluoroperhydrofluorene, C13F22 clearance from the body of animals, as well as some perfluoroperhydrophenanthrene, C14F24 limited clinical studies conducted in Japan and else perfluoroperhydrofluoranthene, C16F26 where. At the present time, the Green Cross Corpora 35 Of the above, perfluoroperhydrofluoranthene is par tion of Japan have available two commercial emulsion ticularly preferred. systems that seem to show good promise in clinical The fluorinated compound of higher boiling point is studies. However a major problem still exists with re suitably added in an amount of from 0.1 to 5% (w/v) of gard to the stability of emulsions produced with fluoro the stabilized emulsion, more preferably from 0.5% to carbons that have acceptable clearance characteristics. 40 2% (w/v). By far the most information available exists on the The perfluorinated hydrocarbon forming the emul material perfluorodecalin. This seems to be ideal in sion is preferably perfluorodecalin. terms of its low biological toxicity as well as its accept Other examples of fluorinated compounds of higher able clearance from the body after administration. Un boiling point include materials sold under the trade fortunately this compound does not give emulsions,. 45 names KRYTOX (RTM) and GALDEN (RTM) (per stable at room temperature for extended periods, with fluoroethylene oxide/propylene oxide copolymers). out resorting to complex mixtures of emulsifying sub It is believed that the higher boiling component of the stances or to mixtures of fluorocarbons. As a conse emulsion acts to stabilize the composition by dissolving quence, a detailed effort is being made, by various re n the fluorocarbon oil and thus by suppressing the de search groups, to produce an emulsion which has better 50 stabilizing "Ostwald ripening" effect which is inherent physiological and stability characteristics. In some in such an oil-in-water emulsion and gives rise to insta cases, the physiological requirements have even taken bility problems in other commercial formulations such second place to the stability requirement. as FLUOSOL-DA (RTM). We believe that the two aspects of stability and physi Preferably the emulsion is formed with the aid of a ological behaviour may not be separable; that is a per 55 surface active agent of the poloxamer type. Poloxamers fluorocarbon which gives the required physiological are a class of non-ionic surface active agents being po effects will, as a consequence, also be somewhat unsta lyoxyethylene-polyoxypropylene-polyoxyethylene ble when emulsified, and moreover, that other research block co-polymeric surfactants, sold under the trade groups appear to have considered emulsion stability in a name pluronic. - too simplistic way. The major way in which the drop 60 lets in emulsions can grow in size is by a process of The invention in another aspect provides the use as a droplet coalescence. Normally, this can be retarded, blood substitute of an emulsion of a perfluorocarbon in and practically eliminated, by using emulsifying agents an aqueous medium, according to the first aspect of the that can form electrostatic and mechanical barriers at invention. the oil/water interface. However, a much more subtle 65 The invention in a further aspect provides a method means of instability can occur in which the small parti of stabilizing an oil-in-water emulsion of a perfluori cles become small and the large particles become bigger nated hydrocarbon in an aqueous medium, wherein through a process of molecular diffusion, known as there is added to the said emulsion a minor amount of a 4,859,363 3 4. fluorinated compound of higher boiling point than the TABLE 1. perfluorinated compound emulsified. Stability Testing of Fluorocarbon Emulsions The invention will be further described with refer Coulter Counter Analysis: reported as % change in cumulative percentage oversize after 7 days storage at ence to the following illustrative Examples, which de 5 roon ten perature. scribe the making of typical formulations according to Change in this invention (Examples 1a to 1c), together with the percentage procedure used to test the emulsions for stability (Ex Example greater than ample 2 and Table 1). No. Emulsion type 0.83 um 1.05 um O la Perfluorodecalin -- EXAMPLE 1 Perfluoroperhydrofluorene O - 4 b Perfluorodecalin -- Preparation of perfluorochemical emulsions with Perfluoroperhydrofluoranthene 2 c Perfluorodecalin -- enhanced stability Perfluorperhydrophenanthene 4. 2 Emulsions were prepared using an ultrasonic 15 d Perfluorodecain alone homogeniser (Dawe Soniprobe) (10 minutes homogeni (as control) 14 10 sation at setting 5). The formulae were as follows for 50 The invention will be further described with refer ml of emulsion: ence to the accompanying drawings, wherein FIGS. 1 Example la 20 to 4 are bar charts (histograms) which illustrate the stability of emulsions formed from perfluorodecalin in Perfluorodecalin, 10 mi (20g) aqueous media without addition of a higher-boiling Pluronic F108 (Poloxamer 388), 1 g component and with the addition of higher-boiling Perfluoroperhydrofluorene, 0.5 ml (1 g)(2% w/v) components defined as follows: r Distilled water to 100%, to 50 m 25 C13: Perfluoroperhydrofluorene (C13F22) C16: Perfluoroperhydrofluoranthene (C16F26) Example lb In these bar-charts stability is expressed as a fraction of perfect stability (i.e. no separation) which is taken to be Perfluorodecalin, 10 ml (20g) unity, the unshaded areas representing the stability of Pluronic F108 (Poloxamer 338), 1 g 30 the emulsion at O' C. and the shaded areas representing Perfluoroperhydrofluoranthene, 0.5 ml (1 g)(2% stability at 37 C. "Day” represents the day of sizing w/v) after preparation of the emulsion. Distilled water to 100%, to 50 ml With reference to the bar charts: FIG. 1 represents stability figures at Day 10 based on emulsions contain Example lic 35 1ng: Perfluorodecalin, 10 ml (20g) Perfluorodecalin, 20% (w/v), Pluronic F108 (Poloxamer 388) 1 g Pluronic F-68 (Surfactant), 1% (w/v) Perfluorperhydrophenanthrene, 0.5 ml (1 g)(2% Higher boiling additive, 1% (w/v) (as defined) w/v) 40 Distilled water to, 100% (w/v) Distilled water to 100% to 50 ml FIG. 2 represents emulsion stability at Day 44 based on emulsions containing Example 1d (Formulation of a control emulsion without Perfluorodecalin, 20% (w/v) added stabilizer) Pluronic F-68 (Surfactant), 4% (w/v) Perfluorodecalin, 10 ml (20g) 45 Higher-boiling additive, 1% (w/v) Pluronic F108 (Poloxamer 388) 1 g (as defined) Distilled water to, 100% (w/v) Distilled water to 100%, to 50 ml FIG.3 represents emulsion stability at Day 8 based The boiling points of the fluorinated compounds re on emulsions as defined for FIG. 2 above. ferred to above are as follows: 50 FIG. 4 represents emulsion stability at Day 14 based Perfluorodecalin, 140-142 C. on emulsions containing components as defined for Perfluoroperhydrofluorene, 190-192 C. FIG. 1 but with the higher-boiling additive at a level of Perfluoroperhydrophenanthrene, 215 C. 0.5% (w/v) of the emulsion. Perfluoroperhydrofluoranthene, 242-244 C. 55 Pluronic F-68=a polyethylene oxide surfactant Example 2 From FIGS. 1 to 4 it can be seen that the higher Testing of the perfluorochemical emulsions for stability boiling additive confers improved stability on the emul sions both at 0° C. and 37 C., the effect being most The emulsions prepared in Example 1 were stored for marked for the C16 additive (i.e. perfluoroperhydrofluo a period of 7 days at room temperature and the particle 60 ranthene). size determined using a Coulter Counter (Model TAII) It is also noteworthy that the concentration of the higher boiling additive can also affect stabilization. fitted with a 30 micron orifice tube. The change in the Thus a 1% level of additive confers greater stability percentage of particles greater than two arbitrary size than a 0.5% level of additive. limits was used as an indicator of stability. The results 65 For emulsion preparations stored at high tempera given in Table 1 below show that the added fluorinated tures of 37 C. (accelerated stability test) a relatively compounds boiling point gave an improved stability to marked increase in stability is observed for emulsions the emulsion system. containing the higher boiling point additives. This is 4,859,363 5 6 strongly apparent for emulsions containing per emulsion according to the invention or Fluosol-DA. fluoroperhydrofluoranthene. However, the haematocrit decreased slightly in all ani The experimental details of preparation and sizing of mals during the course of the experiments. Changes in the emulsions on which the bar charts of FIGS. 1 to 4 organ weights occurred in animals injected with the are based are as follows: 5 emulsion according to the invention and these were Perfluorocarbon emulsions were prepared using an comparable to those seen after administration of Fluo ultrasonic homogeniser (Dawe Soniprobe); the experi sol-DA. mental conditions were 30 minutes homogenisation at We claim: setting 6. Formulations in weight/volume for the emul 1. An oil-in-water emulsion of perfluorodecalin in an sion types are listed above. 10 aqueous medium, wherein the emulsion is stabilized by Emulsions were sized using the photon Correlation the addition of a fluorinated compound of a higher Spectroscopy Method (PCS-Malvern Instruments boiling point than perfluorodecalin, wherein the fluori Limited) on preparation, and stored at either a tempera nated compound of higher boiling point is selected from ture of 0° C. or 37 C. (37° C. constitutes an accelerated the group consisting of: stability test). The emulsions were periodically assessed 15 perfluoroperhydrofluorene C13F22; for a relative change in size. perfluoroperhydrophenanthrene C14F24; and The stability parameter is described as the ratio perfluoroperhydrofluoranthene C16F26; Dt/Do where Do corresponds to the initial particle size and wherein said fluorinated compound of high boil of the formulation and Dt is the size at time t (days). It ing point is added in an amount of from 0.1% to 5% follows that on the day of initial sizing Dt = Do and the 20 weight/volume of the emulsion. stability parameter will equal 1. An increase in particle 2. The emulsion according to claim 1, wherein the size is therefore described by a stability parameter value fluorinated compound of higher boiling point is added greater than 1. in an amount of from 0.5% to 2% weight/volume of the The "Absolute Stability” parameter plotted along the emulsion. vertical axis of the bar charts of FIGS. 1 to 4 is the 25 reciprocal of this stability parameter. 3. The emulsion according to claim 1, wherein the The suitability of the emulsions of the invention for emulsion is formed with the aid of a surface active agent use as blood-substitutes in animals is illustrated by the of the poloxamer type. following biological experimental data. 4. An oil-in-water emulsion of perfluorodecalin in an A 20% w/v emulsion of perfluorodecalin containing 30 aqueous medium, wherein the emulsion is stabilized by 1% high boiling point oil (C16F26) was used. Female the addition of perfluoroperhydrofluoranthene, C16F26, Wistar rats (body weight: 140-160 g) were injected added in an amount of from 0.1% to 5% weight volume either intravenously (i.v.) via a tail vein or intraperito of the emulsion. neally (i.p.) with 10 mi.kg body weight emulsion 5. A method of stabilizing an oil-in-water emulsion of which had been prewarmed to about 37° C. Blood sam 35 perfluorodecalin in an aqueous medium, comprising ples (about 0.5 ml) were removed from the retro-orbital adding to said emulsion a fluorinated compound of a plexus under light ether anaesthesia on days 0, +3 and higher boiling point than the perfluorodecalin, wherein --5. On day 7, animals were also anaesthetized with the fluorinated compound of higher boiling point is ether and then exsanguinated by cardiac puncture. selected from the group consisting of: They were then sacrificed for detailed postmortem and perfluoroperhydrofluorene C13F22; the wet weights of liver, spleen, thymus and mesenteric perfluoroperhydrophenanthrene C14F24; and lymph nodes (MLN) were recorded. Measurements perfluoroperhydrofluoranthene C16F26; were made of packed cell volume (haematocrit) and and wherein said fluorinated compound of high boil "fluorocrit' on whole blood samples. Additional groups ing point is added in an amount of from 0.1% to 5% of animal were injected i.v. or i.p. with an identical dose 45 weight/volume of the emulsion. of either Fluosol-DA 20% (Green Cross, Japan) or 6. A method of stabilizing an oil-in-water emulsion of physiological saline solution (0.9% w/v NaCl) as con perfluorodecalin in an aqueous medium, comprising trols. adding to said emulsion perfluoroperhydrofluoranthene All animals survived in an apparently healthy condi C16F26, in an amount of from 0.1% to 5% weight tion throughout the experiments. No fluorocrit was 50 /volume of the emulsion. detected in the blood of animals injected with either the k k ck 3k xk