CA1045976A - Liquid membrane encapsulated medicinals and uses thereof - Google Patents

Abstract

ABSTRACT OF DISCLOSURE
A method for removing a toxin from the gastro-intestinal tract which comprises providing an emulsion in said gastro-intestinal tract which comprises an interior phase surrounded by a surfactant-containing exterior phase, said exterior phase being immiscible with the aqueous environment of said gastro-intestinal tract and permeable to said toxins, said emulsion being further characterized as being stable in said gastro-intestinal tract, and said interior phase comprising (a) a reactant capable of converting said toxin into a non-permeable form, whereby said toxin permeates the exterior phase of said emulsion into said interior phase and is converted into a non-permeable form or (b) a catalyst which is insoluble in said exterior phase and capable of converting said toxin, whereby said toxin permeates the exterior phase and is converted in said interior phase.

Description

- ~0 ~ ~ 7 1 BACKGROUND 0~` T~E P~IOR ART

2 FqELD OF ~ INVENTION

3 Thlq lnvention relates to the use of liquid mem~

4 brane technology in preparlng medicinals. The medicinals prepared by thls invention may be ingested and may be uti-6 lized as traps ~or toxins present in the GI (gastrointes-7 tinal) tract, or as slow release compositions of drugs, or 8 as reactors. In the trap embodiment the liquid membrane 9 encapsulated medicinal is an emulsion comprisin~ an ext ~ a phase which is immiscible with the liquids present in the 11 GI tract and permeable to the toxins therein, and an in-12 terior phase which comprises a reagent capable of convert-j 13 ing said toxin to a nonpermeable form. In addition, hydro-1~ philic adsorbents may be encapsulated such as a hydrophilic carbon or a silica gel. When the compositions of the in-16 stant invention are utilized as sloW release drugs, the 17 internal phase o~ the emulsion will comprise a drug which 18 is slightly soluble in the external phase of the emulsion 19 whereby said drug permeates through said exterior phase o~ `
the emulsion over a period of time lnto the GI tract. ~he 21 third method for utillzing the compositions of the instànt 22 invention comprises encapsulating a catalyst for a reaction ,.
23 whlch is desired to be ~arrled out in the~I tract. In 24 this embodiment the reactants present in the ~I tract ~ermeate through the external phase of the~emulsion into 26 an interior phase wherein said catalyst~ for example, an 27 enzyme is immobillzed and are converted to reaction prod-28 ucts which then may permeate throu~h~the external phase 29 back into the GI tract. In all cases~the 11quid membrane , encapsulated mèdicinals may be administered by either oral 31 ingestion or injection anywhere else into the GI tract.

SUMMARY OF ~ PRIOR ART
2 It is known in the ~rt that solid microcapsul'es 3 may be utillzed to encapsul~te medlcinal~. For example, 4 in the December 20, 1~71 issue o~ "The Jo~rnal of the American Medical Associatlon" in the "Medical News Section~', ' ~ ' 6 a revlew o~ the microencapsulated medicinal art is presented.
7 In this article, a technique ~or treating uremic wastes in - 8 the gastrointestinal tract with microencapsulated activated 9 carbon is disclosed. The microcapsule is permeable to the uremic wastes and said activated carbon ls utilized to ab-11 sorb some o~-the wastes. In thls technique, uric acid and 12 creatinine are removed. The above reference also teaches 13 a technique wherein urea is converted to ammonia and C02 by 14 the use o~ m1croencapsulated urease. The ammonia is then reacted with and trapped by a microencapsulated ethylene 16 malelc acid copolymer while the carbon dioxide is exhaled 17 through the lungs.
18 It is known in the ark of slow release medicinals 19 that medicinals can be encapsulated by varlous solid ma-~20 terials, for example, hydroxy alkyl cellulose ethers, as ' 21 taught in U.S. patent 39493,407, and'gelatin, as taught in 22 U.S. Patent 33526j682. In both o~ these patents, the 23 microencapsulated medicinal is released over a time period 24 into the GI tract by dissolution o~ the solid capsule material. ~ '''''`' '''' '' ~
26 There are various problems known in the art in ~;
27 using solid microcapsules as reactors~as traps and as~slow '~ 28 release compositions. One problem is that solid capsules -;
., ... ~ . ~ , 29 are prone to swell ~ollowed by rupture~and indeed various ~ ' methods to solve thls problem have been utilized,'includ~
31 lng crenation, etc. Thls process increases the cost o~ ' ; 32 microencapsulated systems and when long resldence times in ~(~45976 1 the GI tract are encountered, these crenated compounds or 2 compositlons stlll rupture to an undesirable extent.
3 Furthermore, the microencapsules which do not dissolve ln 4 the tract o~ten lead to ~ecal compactlon. In the composi-

5 tions of ~he instant invention, the encapsulating medium is

6 liquid; thus, expanslon of the internRl phase does no~ lead

7 to ruptue of tfie composltIon~as ~n tne solid~microencap-

8 sulated system disclosed above.

9 As pointed out in the patents cited above, when gelatin is utilized to encapsulate ~edicinals to provide 11 slow release, various conditlons encountered during stor-12 age can f~ect the rate of release in the GI tract, For 13 exampleg gelatin is very sensitive to temperature and 14 humidity, etc. In the emulsion systems o~ the instant invention, storage conditions do not substantially a~ect 16 the rate of release of the compositions in the GI tract.
17 U.S. 3,5389216 describes an invention in which --18 a thixotropic or gela~inous o~l containing a drug ~or 19 sustained release is injected into an anlmal. The instant invention is quite di~ferent in that a suspendable emul-21 sion is ingested.
22 SUMMARY OF_THE INVENTION
23 T~e instant invention relates to medicinal com-24 pounds which comprise a medicinal emulsi~ied in a water , ~ 25 immiscible external phase. me emulsion is designed to ; ~ ..
~l 26 be stable during pa~sage through the GI tract where said sl 27 medicinals will be ut~lized. To prepare the composition r 28 oP the~instant invention,-the medicinal is usually dis-~` 29 solved in an aqueous ~edium and the solution thereof emul-sified in an oil which is immiscible with the liquids ~ 31 present in the GI tract. The~ dl phase would generally !f~ 32 contain~a sur~actant to enable the preparation of~an ~
., ~ : :. . . .
4 - :
~ .

~0~7 ~
1 emulsion which Will be stable dur~ng passage through the 2 GI tract. The'external phase of the emulsion thu~ acts 3 llke a l~quld membrane surroundlne the internal phase.
4 In a preferred embodiment, the emulsion described 5 above is ~urther dispersed in a liquid which is immiscible ~' 6 with the exterior phflse of the emulsion9 ~or exa~ple, 7 water. This preferred embodiment allows the u~e of the 8 compositions o~ the instant invention in a ~orm wherein 9' dispersion o~ the emulsion in the GI tract is increased.

10 Furthermore~ because of the well known unpalatabilit~ of

11 the usual oils which are used to form the emulsions o~

12 the instant inve~tion9 the continuous phase comprising

13 water or water and ~lavorlng agents is desirable.

14 The compositions of the lnstant invention can be

15 utilized in three dl~ferent manners. For examplej to re

16 move toxins9 reactants and adsorbents can be emulsified in .
'' 17 the interior pha~e o~ an emulsion. The exterior phase o~-18 th~s emulsion will be designed to allow the toxins present 19 in 'the GI tract to permeate through and react With the 20 reactant or be adsorbed on the adsorbent present in the , ~
21 internal phase of the emulslon. In t'his manner, toxins 22 are continuously and irre~ersibly removed as the emulsion 23 pa~ses through the GI tract. In this te~ique, the mem-24 brane is designed to be impermeable to the reaction prod-25 ucts or adsorbed products formed in the interior phase o~
26 the emulsion.
27 In an alternate method, the liquid membrane is - . , ~. .
' 28 utilized to encapsulate catalysts which will~be used in 29 carrying out reactions while passing through the GI tract.' - . :
~ 30 The catalyst may be, for example9 an enzyme9 e.g. urease.
'1 31 Because of the liquid membrane encapsulating the catalysts, :: . . ; . , b 32 the catalyst ltsel~ can be used under conditions where the ~ ;

1~45~7~
i catalyst in an uncapsulated state Would be destroyed. For 2 example, urease could be protected from the loW pH present 3 ln the ~tomach o~ the GI tract by designing the liquid 4 membrane to exclude the passage o~ ions includIng hydrogen 5 ion.
6 In the third use of the compositionB of the in-7 stant in~ention9 medlcinals are released by perméating 8 through the exterior phase of the emulsion into the GI
9 tract during the passage of the emulsion through the GI
10 tract. In this embodlmentg the medic~nal compound is 11 emulsified in a liquid in which the medicinal is only 12 sparingly soluble. This low solubility in the external 13 phase o~ the emulsion allows passage o~ the medicinal into 14 the GI tract over lon~ time periods.
15 In preparing the compositions of the ~nstant in-16 vention~ it is desirable to incorporate a sur~actant in

17 the external phase. ThiS surfactant may be present in

18 amounts from .01 to 90% wt. o~ said external phase. Pref-, .
;~ 19 erably9 the surfacta~t will be present in amounts ~rom 1 to 5 wt. % ~ said extarnal phase. The external phase ~s ~.
, 21 generally made up of the sur~actant and an oil. The oil, ' .
22 o~ course9 is designed to be immiscible with the li~uids 23 present in the ~ tract. A ~urther quali~ication ~or~oils ?
" 24 wh~ch may be utilized in preparing the compositions of the 25 instant invention is that the oils must not be harm~ul to ; , .
26 the human body. These oils along with the surfactant ,~ 27 should also be ~airly inert so that they are not destroyed 28 by the envlronment in the GI tract. ~ ~
29 The body digests many o~ the natural animal and vegetable oils. These readily digested oils such as tri-31 glycerides cannot be ll~ed to form a large fraction of the ~
32 oil in the external phase. The natural~ digestive processes !, .

~ 4~
1 would be expected to rcmo~re these oils f~om the emul~ion 2 as~it pass~d throug~ the G~ trRct~
3 . It is well known ln the art that ~'most artl~iclal 4 or natural emul~ions are broken ln the stomach", See, ~or 5 example, Physiology of ~he Di~estive ~ract, H. ~. Da~enport, 6 3rd Ed. 1g71 Y~ar Book Medical Publishers, Inc~, ChicagoJ
7 I11., page 197. It requires a special type o~ emulsion com-8 position to pass through the GI tract intact. Some exam-~ 9 ples o~ oils which can be utilized in form~ng the com positions o the instant invention include hydrocarbon 11 oils, eOg. paraf~ins, isopara~fins, naphthenes, and aro-; 12 matics, having molecular weigh~s up to 1,000. Parti-13 cularly desirable are the mineral oils which have been 14 highly refined for use in human ingestion. Additionally, oils or trea~ed oils from animal or vegetable sources may 16 be u6ed if they can pass through the GI tract substantial-17 ly unconverted, for example, vegetable oils and animal 18 fats that are heavily hydrogen~ted so as to contain at least

19 10 wt. % more hydrogen than at normal saturation. Fur~her, .

20 sillcone Muids containing the repeating unit CH3 can

21 t

22 -Si-0-2~
2~ CH3 be used. P~r~luorinated hydrocarbons'may also be used.
26 Any o~ these oils should have a ~iscosity o~ 2 to 1000 .
27 cent~stokes at normal body t mperature. The pre~erable 28 range ls 10 to 150 centistokes. `
29 The surfactants must also be harmless to the ~ ;~
human body lf they are to be utiIlzed in the instant in-31 vention. The specif~c sur~actants which can be used in .-i 32 preparing the emulsions above include sorbitan monooleate .~ . ~ , , .
33 and other types o~ sorbitan`fatty acid esters, e.g. sorbi-34 tan, sorbitan monolaurat~ sorbltan monopalmitate~ sorbi~n ; ~
, ~ 4 ~
stearate, sorbltan trlste~rate, ~orbitan trioleate; poly-2 oxyethylene ~orbltan fatty acld esters; and mono- and di-3 glycerides.
4 It may also be desirable to use strengthening agents to improve the stability o~ the emulsions. Nonllmit-6 ing examples of strengthening agents include; polyisobut~
7 i.e. especially the lower molecular weights, e.g. a mol~-8 cular weight of about 900, polyisobutylene succinic anhy-9 dride-pentaerythritol adducts, ethylene-vinyl acetate co-polymers, sulfonated butyl rubber and decylmethacrylate-11 vinyl pyridine copolymers.

, 13 A controlled releese medic~nal (sodium _allcylabe.
14 In experlment 19 a solut1~n o~ 8 wt. % sodium salicylate and 8 wt. % sucrose in distilled water was used to form the 16 internal phase of the emulsionO Experiment 2 used 10 wt. %
17 sodium salicylate and 8 wt. % sucrose in water~ but was the 18 same as experiment l in all other respects.
19 These internal phases were added with ~igorous agitation, in an amount su~c~ent to ~orm 33 wt. % o~ the 21 ~inal emulsion, to an vil phase consisting o~:
22 2.0 wt. ~ Sorbitan monooleate 0.5 wt. % o~ a high molecular weight polyamine 24 with the structure:
2~ CH3 ~ CH3 ~ H ~ 0 H 0 27H-C - C - C - C ' ' " ' ' -' 2~ ~ H , ~ ~ N-(CH2-CH2-N)I~-C-CH3 2390 3~ C~I3~ /~ O

32 wherein m is an integer o~ about ~0 3~ 3.5 wt. % o~ fl polylsobutylene~with a molecular 3~ weight of about 900 94.0 wt. ~ o~ an isoparaffinic lubricating oil 36 stock with a viscoslty at 100F of about 100 37 Saybolt Uhiversal seconds.
38 200 grams o~ this emulslon was suspended in 600-grams o~ a 39 synthetic gut ~luid whlch comprised:
o.8 wt. % ~lbumin ~rom eggs 41 0.5 wt. ~ NaCl ' .

55~76 ~ o.4 wt. ~ NaHC03 2 98.3 wt. ~ distllled w~ter 3 with mlld agltation to slmul~te conditlon~ ln the small 4 intestine. The appearance o~ sodium salicylate and sucr~
, In the bulk synthetlc gut fluld were monitored with time 6 by analysis. The resu~ts are shown in Ta~le l below 7 Table 1 .
8 Controlled Release o~ M~dicinals (godium Sali~te) 9 by Diffusion in Liquid Membrane Concn. in % o~ Max. ~ ~ibrium 11 External Phase3 Concn. in 12 ~ tl) Outer Phase -1~ Time so~m ~ ~aium 14 H~_ S~ ~ su~se ~ Sucrose ~6 0.0 0.005 0.0 .5 17 80o.83 0.0~0 64.o l.o 18 Ex~t7 ~2 - 19 ~ 0.0 o.oo8 0.0 1.0 20 80 0.59 0.013 45.0 1.6 21 As can be seen ~rom the above table, the sucrose was at 22 least 98 percent contalned over the 80 hour period in both

23 the experiments whlch ind~cates that the emu~sions re-

24 mained substantially lntact. The controlled release of sodlum salicylate was demonstrated by releasing 64 and 45 26 percent respectively o~ the~maximum possible amounts over ;
-27 the 80 hour period~
28- -The selec.tlon of the internal phase o~ the ~j ;
39 emulsions of the lnstant invention is depe~dent on their 30 intended use. For exampleg toxlns present in the GI tract ~;~
, 31 may be removed by trapping them in ~k.~. ~n~ernal phase of-the 32 emulsion, i.e. conversion o~ a toxin which can permeate 33 the external phase of the emulsionJto an impermeable ~orm.
34 Toxins may also be converted9 ln the internal phase, to an innocuous form, or alternatively to a ~orm which may be 36 subsequently trapped. An e~ample of this technique is the 37 converslon o~ urea9 by use o~ urease, into carbon dioxide, ~ '.,, . ' ~ :

_ " ' ~ 145~76 whlch may be exh~le~, and ammonia, which may be tr~pped by 2 an encapsulated strong ~cid.
3 The varlous toxins which may be removed from the 4 GI tract by trapping in the internal phase o~ the compo~i-tions o~ the lnstant ~nvention include 6 Table 2 7 -^~ Toxin Removal with Reagents~
8 Encapsulated in Liquid Membranes ~ -`
9 Toxineagents Ammonia Acid - preferably hydro-11 chloric, sulfuric -12 : or citric 13 Phenol Base - preferably sodium 14 : hydroxide Phosphate Calcium Salts - pre~erably~
16 a combination of 17 calcium chloride 18 and calcium 19 hydroxide Lactic Acid Base - preferably sodium 21 . . hydroxide ~2 Iron ~ase - pre~erably sodium ~ `
23 hydroxide 24 copper : Sulfide - preferably sodium sulfide 26 Silver Sulfide - preferably ~ :
~7 sodium sulfide , 28 Mercury ~ Sulfide - preferably ':
29 . sodium sulfide Examples of using the instant invention to con-31 vert materials present in the GI tract into useful prod-32 ucts ~nclude: ' 33 ~ (1) The use of l~quid membrane encapsulated ~ .
34 amylase (an enzyme for the ~hydrolysis of starches for the ~ ~
35 digestion o~ starches), ' ~ : ' 36 (2) The use of liquid membrane encapsulate~d 37 11pase (~an enzyme for:the~hydrolysis of trlglycerides : ::~
38 for the digestion of triglyc'er1des)J

.

1~4~976 ( 3 ) The use o~ llquld membrane encapsulated 2 lactase to he;lp young children hydrolyze lacto~e, ; .
3 ~4) The us~ o~ liquld membrane encap~ulated 4 mixed pancreatic enzymes to promot~:,the digestlon ~nd utl-llzation o~ protelns in childre~ with cystic fibrosis.
6 Other examples of using the compositions o~ the .
7 instant invention as reactors,-wherein mater~s-which are : :
8 not capable of being trapped by reaction or adsorption ln : ~
9 the internal phase o~ emulsions o~ the instant invention : .-are converted into products which can be so trapped or ad-ll sorbed, include converting glucose to gluconic acid, and, 12 l~ctose to lactic.acid.
13 The compositions o~ the ins.tant invention may be .
14 utili ed as slow release medicinals~to release, for example, ~odium Salicylate, aæ described above, Trimethaphan Camphor~
16 sulfonate, Trimethadione, Metronidazole or Penicillin 0, ~ :
17 particularly the water soluble potassium salt~
l8 In the.preparation o~ products o~ this sort, the .-.
l9 emulsion is designed so that the medicinal is only slightly . ~ ;.
20 soluble in the exter~al phase so as to provide permeation ~.
21 of the medicinal through :the external phase into the GI
:22 tract over a period~of time. In general, emulsions o~
23 this sort are designed so that the medicin~a1l ls solub}e in 24 the external phase.~rom about O.OOOl wt. % to about IO.wt.
% at 37C.
26 In carrying out the process of the instant in- .
.. ..
27 véntionJ the internal phase i9 seledted according to the 28 above crlteria to enable the ekilled artisan to carry 29 out the desired operations. For example,:when it is-desired 30 to provide a composition for the removal of ammonia in the 31 GI~ tract, an internal phase comprising a lO normal aqueous 32 hydrochloric acld solution is~emulsified in a hydrocarbon~

: :

~.: ~~ : . . :
.

1~45~76 1 solution containing a nonlonic sur~actant along w~th a 2 thickener ~or the hydrocarbon phase. ThiS thlckener, as 3 will be ~urther described below, is utilized to prov~de 4 emulslons which do not break during passage to the ~I
tract since it would be quite evident to the skilled 6 art$san that the advant~ges o~ the instant invention will 7 not be obtained wlth emulsions that are not stable durlng 8 passage through the ~I tract. The aqueous and hydrocarbon 9 mixture is emulsified under vigorous agitation to form a stable emulsion. In this procedure, the aqueous phase is 11 added slowly to the hydrocarbon, sur~actant and thickener 12 solution over a period o~ time to form an-oil continuous 13 emulsion. This emulsion may be passed dirsctly by inges-1~ t~on through the GI tract; hGwever, in the pre~erred em-bodiment, thie emuleion will be mixed under conditions of 16 low agitation with water to provide a three-phase system.
17 Thi~ three-phase system may be then ingested and subse-18 quently passed through thè GI tract. This particular 19 emulsion will pass through the stomach into the intestines wherein ammonia present therein will permeate through the 21 external phase o~ the e~ulsion, i~e .9 the hydrocarbon con-22 tinuous phase, into the aqueous ~.ydrochloric ac~d phase 23 wherein~ the ammonia will be converted to ammonium chloride~
24 which is impermeable and thus trapped inthe lnternal phase.
The emulsion, belng stable during passage to the GI tract, 26 then wlll be passed out o~ the human body carrying t~e am-. .
27 monia trapped in the internal phase along with it.
28 The foLlowing are other speci~ic embodiments of ;
29 the instant invention, however, there is no intention to be bound b~ these embodiments since variations which would 31 be obvious to the skilled artisan may be made.

: :

,~: . .
': : : : ' ~. .

.. : ~ . . ... . ..
. ,: ; - :
; ' ' ' - . ~ . ~' EXAMPLE 2 - Ammonia Removal ._.
2 Liquld membrane encapsulation,that ls,utillzing 3 the exterlor phase o~ fln emulsion ~s ~ membrane allows one 4 to use effective ionic reagents such as hydrochlorlc acid, which cannot be used wlth other encapsulation methods. A
6 hydrocarbon base liquld membrane ls used. The ionic bar-7 rier character of this membrane prevents the hydrogen and -~
8 chlorine ions of this totally ionized strong acid ~rom 9 penetrating the membrane to the bulk fluid (whlch would be - ' the gut ~luid in this application). me species to be re-11 movedJ ammonia, always exists in equilibrium with the am--12 monium ion (NH3 ~ H+ = NH4+). Whlch ~orm 1s dominant 13 depends on the pH. Ammonia, the molecular spe'cles NH3, "~ ' . ' .
14 which exists at gut pHIs9 can readily penetrate the liquid membrane to contact the hydrochloric acid reagent. At the 16 very low pH o~ the encapsulated hydrochloric acid, the ' ' 17 molecular ammoni~ which has moved through the li~uid mem-18 brane is converted to ammonium (NH~). This ionic species 19 ls prevented ~rom trans~erring back out by the ion barrier properties of this liquid membrane.
21 The liquid membrane encapsulated hydrochloric 22 acid is shown to be e~fe~cti~e experimen~ally. For any re- ;
. . , ._ . .
23 agent system to be e~fective''in the gut, i~ must remove 2l~ ammonia from the very low cjoncentrations whlch are~ound in the gut. Tests with liquid membrane encapsulated hy-26' drochloric acld reduced the ammonia concentration o~ a 27 solution down to less th'an 3 mg %~ i.e. 3 mg per 100 ccls.
28 In addition to removing ammonia to low levels, 29 ~mall reagent volumes are highly desirable. This could be accomplished by using liquid membrane encapsulated con-31 ~-centrated, lO~normal, hydrochlorlc acid.~ In this experi-3? ment, the liquid membrane oil phase~was made ~rom~

. ' :
' " ', ', ~ . ' 1~4Si~76 ` .
1 2 ~m Or Sorbitan monooleate 2 O. 5 gm of a high ~olecular weight 3 polyamlne with the structure 4 CH /CH ~ H O
5 1 3 ' \ ' ~ H O
6H-C . C ~ C - C ~
3 3 \C~ C - C ~ N-(CH2-CH2-N)4-C-CH3 H H
11 4.5 gm of a polyisobutylene with an aver-12 ~ge molecular weight o~ about 900.
1~ 93.0 gm o~ an i~oparaffinic lubricat- ;
14 ing oil stock with a viscosity at 100F of about 600 Saybolt 16 Universal seconds 17 100 gm of oil phaseJ total 18 To the above 100 gm~. o~ oil pha~e, 50 gm of lON hydro-19 chloric acid was added in a progression of drops~with vigorous agitation to form an emulsion. One gram o~ this 21 emulsion was added to 100 gms of dilute ammonia solution 22 in a beaker. The combination was stirred with a propeller 23 at a very slow 50 rpm to give very mild agitation. This 24 agitatlon is probably milder than naturally occurs in the :
gut. As too mild an agitation can produce slow removal, , 26 it was a severe test.~ The-very encouraging rapid removal 27 o~ ammonia obtained i8 shown below in Table 3.
28 Table 3 29 Ammonia Removal by Li~uid Membranes Ammonia Concn.
31 Contact Tlme ln Bulk Phase 32 ~(Hours 33 0 ~ ~ 26 34 ~/2 21 2 ~ 10 36 ~ 24 ~ 6 37~ Note that the ammonla level was~reduced~Prom:26 mg ~ to 10 38 mg % in the ~rst two~hours o~ this gentle contacting~

. . ' .' 97 ~
The level dropped to 6 mg ~ in 24 hQurs. The e~fectiveness 2 o~ ammonia removal was al80 ~ulte encouraging. Based on 3 the ammonia removal achieved in this experiment wlth 1 gm -~
4 o~ liquid membrane encapsulated reagent, the quan,tity re~
quired to remove all o~ the nitrogen from 12 gm/day of urea ~6 was calculated. Only 300 cc of emulsion per day is re- -7 quired. The use of a liquid membrane suspensionJ i.e. the 8 above described emulsion suspended in an aqueous phaseJ
9 wherein 40 volume percent o~ the emulsion was concentrated hydrochloric acid, would lower the requirements to 100 11 cc's ~or remo~al of all the urea nitrogen.
12 ~ne liquid membrane must also ~unction in gut ~;
13 fluid. To test this9 a synthetic gut fluid was prepared.
14 me synthetic gut ~luid was made with 0.5 wt. ~ NaCl to simulate salt concentration, bu~fered with 0.4 wt. %
16 NaHCO~ to hold the proper pH and contained o.8 wt % egg 17 albumin to simulate protein content. The same type of 18 experiments described above were performed. '~he results, 19 below ln Table 4, show quite clearly that the liquid mem-brane encapsulated hydrochloric acid removes ammonia ~rom 21 synthetic gut fluid.
22 ,T,a~le 4 ~
23 Ammonia Removal_From ,Synthetic Gut Fluid 24 Ammonia Concn. in Contact Ti.~ ~y,nthetic ~ut F]Uid 2~ ~ ~ (mg %) ~~

29 21~ 20 31 Another quite interesting observation was made 32 when contacting the above-descr~bed emulsion with syn-: , 33~ thetic gut fluid. ~he stab~lity was enhanced. ThiS may , ~ , . - ~

~ - 15 -, ..... . .
.

~0~9~76 1 be a result of protein adsorption on the suRpended e~ul-2 sion droplets. The enhanced stabllity in gut ~luld may 3 play an important role ln the in ~ivo emulsion s~ability 4 discu~sed below. ~' The hydrochloric ~cid reagent could be replaced 6 with citric acid, or any other acld capable of neutrallz-7 ing ammonia, in the above example.
8 EXAMPLE 3 - Urease Encapsulation 9 The approach discussed above concerned the re- ~
10 moval o~ ammonia which had been generated ~rom urea by the ~' -11 enzyme urease. Substantial urease activity in the gut has 12 been establlshed by the literature. However,' it'has not 13 been conclusively pro~ed that there is sufflcien~ urease 14 activity to convert all the urea that must be removed each '~
15 day. It might be necessary to in~roduce more urease '~
16 activlty'to the gut. Simple in~ection of'unencapsulated 17 urease would not be likely to be e~ective as the low pH o 18 the stomach would denature much o the enzyme. Therefore the 19 encapsulation of urease was tested in a neutral solution by an ion excluding liquid membrane. The ion exclusion .
21 nature of ~he liquid membrane would prevent the hydrogen 22 ions present at the low pH o the s~omach rom penetrating .... . . . . .
23 the membrane and damaging the urease. The molecular spe-24 cies~ ureaJ however~ co~ld readil~ trans~er through the mem-

25 brane where it would be hydrolyzed to ammonia and carbon ;

26 dioxide. The carbon dioxide, aga~n a molecular species,

27 could trans~er back out through the membrane. The 9 grams

28 per da~ o~ carbon dioxide produced from 12 gms per~day'o~ ''

29 u~rea could readily be'handled by the lungs.~ The ammonia ''~
- ~ .
produced~by the urease~encapgulated~1n the liquid membrane 31'~-could transfer out through the liquid membrane.` This~oc~
32 curs because the phase'encapsulated ln these-membranes is ; ' , ' . . .

1~)4597~i 1 near neutrfll. At near neutral pH'S the main species is 2 un-ionlzed ammonia which can trans~er out o~ the ion b~r-' 3 rier liquid membrane. The ~mmonia le~vlng the encapsul~d 4 urease may then be removed from the gut fluid by the pre- ~;
viously discussed ammoniR trapping.
6 The system described above was experimentally 7 checked for the transfer of reactant and products into and 8 out o~ the urease containing internal phase as well as the 9 activity and e~ective isolation of the urease. A liquid membrane forming emulslon was made by dissolving o.o46 wt.
11 % urease in water and addlng it dropwise into an oil phase 12 under vigorous agitation. The oil phase consisted o~:-13 2 wt. % Sorbitan monooleate 14 3 wt. % ~igh molecular weight polyamlne with the structure 16 C~3 / CH3~ H 0 17 ' l ~ H 0 18 ~C~ C - C - C ~ ' "

21 ~ CH3~ C ~ N-(CH~C~l2-~)4-C C~I3 23 95 wt. ~ Isoparaf~inic lubricating oil 24 ~ stock with a viscosity at 100F of 2~ about 100 Saybolt Universal Seconds~
26 In the final emulsion9 the weight ratio o~ the urease 27 solution to oil phase was 0~82. TWo ml o~ the above emul-28 sion was added to 30 ml o~ a solution contalning 0.43 29 Molar Urea, 0 1 Molar NaCl, o~ooo8 Molar phosphate bu~fer

30 and containing O.lU 0~ Clelands reagent. Moderate stir- ~ ;

31 ring was used to disperse the e~ulsion in liquid membrane

32 form. ~he pH o~ this bulk urea containing solution was

33 held at 6.7 ~ 0.05 b~ an automatic titrator whioh neu-

34 tralized the~excess product ammonia~with lO normal HCl.
(At the 6.7 pH one-half o~ the~ammonia produced is in ex~
36 cess~over the quantity forming blcarbonate~with the carbon - 17 - ~

.

1 dioxide.) In the~e experiments, t~e quantity of HCl re-2 quired to baL~nce the excess product ammonia wa~ recordcd 3 with t~me. The liquid membrances were removed durlng 4 the experiments and relntroduced at a later time.
Increasing the HCl was required initially, 6 indicating that the enzyme ~atalyzed reaction as well as the 7 tr~nsfer of urea lnto and carbon dioxide and ammonia out 8 of the uresse containing internal phase was occurring.
9 When the emulsions were removed, the reactio~ stopped. This shows that the enzyme did not penetrate the liquid membrane 11 to ~he bulk phase and that the initial measured reaction 12 rate was that produced by liquid membrane encapsulated 13 urease. Reintroduction of the emulsion started the re-14 ~ction again. The formatlon o ammonia in these experiments wa~ also confirmed by independent specific analysis o 16 ammonia built up with time.
17 The ra~es of reaction were abo~t 1/50 of those 18 measured under similar conditions with freshly dissolved 19 urease in the unprotected bulk phase. This is a reasonable rate and the reduction from bulk phase includes the effects 21 of ~everal factors. The denaturation o~ the enæyme during 22 encapsulation, and any limitations in transerring material 23 through the liquid membrane or inside the encapsulated 24 phase would all decrease the measured urease ac~ivity.
EXAMPLE 4- Phosphate Removal 26 Since the phosphate ion is difficult to remove 27 by hemodialysis an adj~nct method of removal would be 28 particularly useful. The reagent system selected for en 29 capsulatlon is suggested by nature. Excess phosphate in the body can precipitate with calcium in non-physiologic ~ 18 - ~ -:

.
: :

1~45976 1 modes. Th~ system selected encapsul~tes calclum salt~ in 2 an anion transferrlng liquid membrane. The catlon calclum 3 is retained in the llquid membrane. The flnlon phosphate 4 transfers through the liquid membrane to react with the calcium ~orming the calcium phosphate precipitate which i8 6 trapped in the internal emulsion phase.
7 mis ~y~tem was experlmentally tested~using a--15 8 weight percent CaC12 and a 5 weight percent Ca(0~)2 reagent ~ -9 encapsulated in an anion transporting liquid membrane.
~ne oil phase o~ this emulslon consisted o~
11 95 wt. % Isoparaf~in lubricating oil 12 sto~k with a vlscos~ty at 100F o~
13 about 100 Saybolt Uhi~ersal Seconds 14 2 wt. % Mixture o~ primary and secondary aminas with a molecular 16 weight range o~ 353 to 393 which 17 has an ion exchange capacity of 18 about 2.7 meg/gm.g e.g. Amberlite 19 IA 2 available ~rom Rohm and Haas 2 wt. ~ Polyamine with a molecular 21 weight o~ about 2000 w~th the 22 s~ructure 23 CH3 CH H 0 ;~
24 ' , 3 ` ~ H 0 2~H-C` - C - , C - C ` ' "
27 ~ 3 ~ CH3 C - C ,- N (C~{2-CH2-~)4-C-~H3 29 ~ H H 0 30 . 1 wt. ~ Sorbitan monooleate 31 The aqueous phase was added to the oil to'~orm 33 wt. % o~
32 the tota~. aqueous plu~ oil pha~e~with vigorous agitation.
33~ m is emulsion (281 gms) was then dlspers~ed in a phosphate 34 solution t500 gm). ~he rapid phosphate removal is shown in Table 5 below.

5~7~ - :
Table 5 2Rapid Phosphate Removal 3 ` Tlme ~i Phosphate , ,~
4 ~ ',` (wt.
0 0.273 2 0.123 ~ 1~ 0 07 9 ~4 0.004 Assuming the removal o~ all the phosphate ion 11 (1/2 gms/day as phosphorous) was desiredJthe quantity of 12 liquid membrane suspension, iOe~ the emulsion suspended in 13 an aqueous phase, requlred can be calculated. Based on 14 the above reagent concentration and the reagent occupying 15 40 volume percent o~ a liquld membrane suspension~ 57 cc ;~
16 would be required per dayO
17 Exar~ e 5 - In V~yo Stability o~ Em_lsions '' 18 Emulsions that are used to treat chronic uremia , 19 by ingestlon must be stable throughout the gastrointestlnal tract. As'a critlcal test of stability, high doses o~ a 21 poison were encapsulated in an emulsion to see i~ the ''~ , 22 stability of the liquid membrane barrler was su~ficient to 23 prevent killing test animals. The poison selected was 24 'sodium cyanide at 10 tlmes the lethal dose (10 X LD 50). ~`
25 The liquid membrane formulatlon was'the same ion excluding ~' 26 ~ormulation whlch was used in remo~ing ammonia ~rom solu~
: '., 27 tion and synthetic gut ,M Uid. Wistar strain~ albino rats 28 'were used ~or this study. In addition'to the rats used to 29 determine the LD 50 of this popu~ation, three groups o~ 10 ''~
rats were used. One group recelved distilled water en-31 capsulated in the liquld membrane. A second group re- ~ `
.
32 'ceived 10 times the lethal dose of sodlum cyanide encapsu~
33 lated in the liquid membrane~ The encapsulated aqueous 34 phase was 0.5 wt. ~ sod~um cyanide. This sodium cyanide ~' ~: ., . .................... . : ~ .
.. ~ , . . .... . .

1~45976 1 801ution w~s emul8ified a~ ~ 33 wt. % level in the 8ame 2 oil phase composition a~ u~ual in the ammonia removal 3 examples. Thi8 emulsion was then suspended in an equal 4 volume o~ water prior to administrat~on. In the third group~ the hydrocarbon solution and the sodium cyanide 6 solution were introduced as ~epara~e liquids so there 7 we~e no liquid membranes. All the materials were admin-8 istered by oral intubation. The result~ are summ~rized 9 below in Table 60 ~ .

I L~

'.

.

' ' : - 21 - ~

~0~1~9S7~

~ .
~ o IY ) O r~J
R
o ~ c ~ ~ ~ O ~ -~
C~ ~ S~
~ ~ ~i ~1 U:~ O rl r-l :~ ca ~:
O .
:'` ~ ~ t~O bl~ bD bD bD ~.D
V
~Z h ~~5 ~ r H N .0 ~ ~D.~ C) ~1) ~; a)a)Q) ~I) tD a) ~u~
~ . ~ ~ ~ q~ r~ q ~ ~ q~ .. `:
H O r-l H . ~ q .
~ ~ r~ ~ c c~ C~
E~ ~ c) ~n ~ ~a1 C15 ~ C~ tl5 ~ . ' ,:
Ed Q~ 01bDbD bD ~Db~ ~ `
W t~ ~r7;~ r~ ro ro ~S ~;
H r-l.D ~Q~ > Q~ .
P ~ o ~a~ o Q~ ~ Q~
~ ~ tu ~~ ~ . ~ : ~;
~:1 O ~ q q .~ q : h ~ ::~Q~ ~ a) Q~a~ Q) W ~ ~ +~
V V C~' V ~ V
S:l w W 1 ~
~:1 ..

, . ~ ..
O
Q~ ~ o . u~
~ W SS ~ ~ ~ b"
~ h q~l ¢ ~ E~ ' ~, S S
~'~ ~ ~n r~
~1 '~ : : ' :
' ~ :
" ¢ . : ' .

r~l CU t~ D ~00 ~ O r,-l 22 ~
:........... : ; ~ : :

1~45976 Additionally, the ra~s administered 10 times the 2 lethal dosage of NaCN in the emulsion were. observed to 3 hAve no slgns of toxiclty or pharmocologlc erfects through-4 out the test. It was concluded that the emulslons o~ the `~
5 lnstant inventlon have good stability in vlvo. - ~
' ~:

: ~, ' ' ' .

. . . ~
h,:, ..

," ' ~ ' :

. ~ ,

Claims (9)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An emulsion useful in removing or converting a toxin of the gastro-intestinal tract which comprises an interior phase surrounded by an exterior phase, said exterior phase being immisci-ble with the aqueous environment of said gastrointestinal tract and permeable to said toxin, said exterior phase comprising an oil-soluble surfactant component and an oil component, said oil-soluble surfactant component and said oil component being harmless to the human body, said oil-soluble surfactant component being present in said exterior phase from about 0.01 wt. % to 90 wt. % of said exterior phase, said oil component having a viscosity between about 2 and about 1,000 centistokes at normal body temperature and selected from the group consisting of vegetable oils and animal fats that are heavily hydrogenated to contain at least 10% more hydrogen than normal saturation, perfluorinated hydrocarbons, silicone fluids containing the repeating unit and hydrocarbon oils refined to remove toxic ingredients and com-prising molecular weights up to 1,000, selected from the group con-sisting of paraffins, isoparaffins, naphthenes, and aromatics and said interior phase comprising a non-permeating reactant capable of converting said toxin into non-permeating form or a catalyst which is insoluble in said exterior phase and capable of converting said toxin into a non-toxin.

2. The emulsion of claim 1 wherein said oil-soluble surfactant component is present in said exterior phase from about 0.01 wt. % to 10 wt. % of said exterior phase.

3. The emulsion of claim 1 wherein said emulsion is suspended in a liquid which is not harmful to the human body and said liquid is immiscible with said exterior phase of said emulsion.

4. The emulsion of claim 1 wherein a strengthening agent is included in said emulsion to improve said emulsion s stability.

5. The emulsion of claim 1 wherein said toxin is ammonia.

6. The emulsion of claim 1 or 5 wherein said reactant is an acid.

7. The emulsion of Claim 1 wherein the aqueous interior phase comprises an enzyme catalyst.

8. The emulsion of Claim 7 wherein said interior phase comprises urease which is available to convert urea.

9. The emulsion of Claim 1 wherein said oil component is a hydrocarbon oil refined to remove toxic ingredients and comprises molecular weights up to 1,000, selected from the group consisting of paraffins, isoparaffins, naphthenes, and aromatics.