the types of materials that neutralize harmful agents use three main modes of action : oxidation , reduction or hydrolysis . operating criteria , however , restricts the selection of the active materials . thus , the active moiety must not irritate the skin , react with insecticides or camouflage paints or be lack thermal or temporal stability . this restriction eliminates many of the most active species . furthermore , the active moiety must be incorporated into a highly fluorinated environment that is not amenable to many reaction pathways . table 1 is a list of formulations containing amines , polyalkenimines and / or its derivatives and other active materials that are acceptable for use in the present invention : examples of polyalkenimines are the polyethylenimines . these materials are available from basf corporation ( 4330 chesapeake dr ., charlotte , n . c .) under the trade name lupasols .™ lupasols ( polyethylenimines , pei ) are multi - functional branched or spherical non - toxic cationic and neutral polymers . they are synthesized by the ring - opening polymerization of aziridine ( ethylenimine ). depending on polymerization conditions , lupasols contain various ratios of primary , secondary , and tertiary amines along the polymer backbone . molecular weights also range from 800 to 2 , 000 , 000 . polyethylenimines are synthesized from the ring opening polymerization of the nitrogen homologue of ethylene oxide . the resulting product is a highly branched , spherical polymer , which is easily protonated to form the most highly charged cationic polymer . as a result of their spherical shape and high cationic charge density , polyethylenimines are able to strongly bind onto anionic and polar surfaces . in addition , non - protonated amino groups are available to form hydrogen bonds or undergo further chemical reactions . examples are given below : the percent values assigned to the above listed components of the example skin protectant formulations in table 1 are given for example only . these values may be adjusted up or down and still embody the spirit of the invention if the herein described qualities of efficacy and composition of the present invention are met . all active moieties listed above are useful for both liquid and vapor challenges . the amount of each varies with each formulation . the object is to optimize the quantity of active moiety in the base cream without losing the barrier properties of the base cream . the amount of active moiety can vary from about 1 - 30 %. the amount of perfluorinated polyether oil can vary from about 30 to 60 %. the amount of poly ( tetrafluoroethylene ) can vary from about 20 to 50 %. one criterion for selection of the active materials is increased efficacy against hd and / or gd vapor . most the listed formulations have significantly ( p = 0 . 05 ) increased protection compared to serpacwa ( icd 3004 ) in the penetration cell model against hd and / or gd and are listed in the results sections . the polyalkenimines must also be incorporated into the tsp matrix without degradation of the barrier properties . these materials were incorporated into the cream either as solids or aqueous suspensions . typically they are dispersed into the perfluorinated oil followed by sequential addition of the appropriate amount of f5a poly ( tetrafluoroethylene ). the tsp can contain individual polyalkenimines or mixtures of two or more polyalkenimines . serpacwa ( icd3004 ) consists of fine particles of poly ( tetrafluoroethylene ) resin dispersed in perfluorinated polyether oil . the excellent barrier properties of this high molecular weight polymer formulation are related to the low solubility of most materials in it . only highly fluorinated solvents like freon ® have been observed to show appreciable solubility . this aprotic non - polar polymer mixture provides a unique medium for active moieties of the invention . reaction mechanisms that do not involve charged transition states should be favored in this chemical environment . base creams formed from about 20 - 50 % fine particulates of certain poly ( tetrafluoroethylene ) ptfe resins dispersed in perfluorinated polyether oils ( pfpe ) having viscosities from about 20 cst to about 500 cst afford good protection against chemical warfare agents such as hd , lewisite ( l ), sulfur mustard / lewisite mixtures ( hl ), pinacolyl methylphosphonofluoridate ( soman or gd ), thickened soman ( tgd ) and o - ethyl s -( 2 - diisopropylaminoethyl ) methylphosphonothiolate ( vx ). ptfe and pfpe are available commercially from ausimont ( morristown , n . j .) and dupont ( wilmington , del .). the base creams used in the invention are suspensions of 20 - 50 % finely divided ptfe having a surface area below about 6 m 2 / g in a perfluorinated polyether base oil prepared from poly ( perfluoropropylene oxide ), which has a viscosity between about 20 and about 500 cst . more preferred compositions comprise from about 20 % to about 50 % of finely divided ptfe having an average particle size from about 0 . 1 μm to about 10 μm and a surface area below about 4 m 2 / g in a perfluorinated polyether base oil from 30 % to 60 % having a viscosity between about 20 and about 500 cst . suitable perfluorinated polyether oils are fomblin ® hc - and y - oils ( ausimont ) and krytox ® oils ( dupont ). the fomblin ® oils are mixtures of linear polymers based on poly ( perfluoropropylene oxide ) having the following chain structure : cf 3 -[( ocf ( cf 3 ) cf 2 ) n -( ocf 2 cf 2 ) m ] ocf 3 . the krytox ® oils are mixtures of linear polymers also based on perfluoropropylene oxide and have the chemical structure f -[( cf ( cf 3 ) cf 2 o )] m cf 2 cf 3 . fomblin ® z oils having the formula : cf 3 -[( ocf 2 cf 2 ) n -( ocf 2 ) m ]- ocf 3 , may also be useful in the practice of the invention . the indices n and m indicate the average number of repeating polymeric subunits in the oil molecules . the oils may have a viscosity of about 20 cst to about 500 cst or more . the creams were generally prepared according to u . s . pat . no . 5 , 607 , 979 , incorporated herein in its entirety . other additives to the base cream are water and surfactant and other chemicals necessary to maintain activity . the surfactant facilitates the mixing of the water with the base cream . examples of typical surfactants are perfluoropolyalkylether ( krytox ® cas # 60164 - 51 - 4 from dupont ), fluorolink ® 7004 ( 1 , propene , 1 , 1 , 2 , 3 , 3 , 3 - hexafluoro -, telomers with chlorotrifluoroethene , oxidized , reduced , ethyl ester , hydrolyzed , cas # 220182 - 27 - 4 from ausimont ), and fluorolink ® 7005 ( a perfluoropolyether derivative from ausimont , cas # not assigned ). additional materials may also be incorporated as long as they do not reduce effectiveness of the topical protectant , such as stabilizers , camouflage paints , and sunscreens . a further understanding of the composition of the topical protectant of the invention can be obtained by reference to certain specific example formulations set forth in table 1 . these examples are provided herein for purposes of illustration only and are not intended to be limiting . many active moieties require the presence of water as a reagent for the hydrolysis of hd and gd . the active moieties that react by a hydrolysis mechanism require the presence of water . when the topical protectant is applied to the skin of a user , moisture in the form of perspiration may also aid in the hydrolysis of hd and gd . the addition of perfluorinated polyether surfactants to the base cream facilitates the addition of water . temperature and mixing sheer should be monitored to maintain the base cream at the desired consistency and quality . the active tsps are typically prepared at ambient temperature using mechanical mixing or at controlled temperatures using either a single screw or dual screw commercial extruder ( haake ® rheomix extruder ). mixing times of 10 - 20 minutes are usually sufficient for dispersal of polyalkenimines into the pfpe / ptfe matrix . a typical procedure for the preparation of an active tsp with a polyalkenimine is presented below : in a polypropylene container is added the appropriate amount of polyalkenimine ( 1 - 30 % by weight ) and y25 ( 30 - 60 % by weight ) perfluorinated oil . the suspension is mixed with a mechanical stirrer at ambient temperature for 5 to 15 minutes or with a magnetic stirrer for 10 to 20 hours . to the suspension is added f5a poly ( tetrafluoroethylene ) in three portions with vigorous mechanical stirring for 5 to 10 minutes between each addition . after final addition the container is tightly capped and sealed with parafilm ®. commercial extruders or other high - shear mixing techniques can improve the quality of the final product . although an active tsp can be applied directly to the skin , the application of a powder ( or liquid ) that is a polyalkenimine sprinkled on the skin , or an active moiety in a base cream wherein the cream is spread on the skin , a multilayering approach can also be used . the multilayer approach would be to use the active tsp as the first layer and a solid active moiety powder ( or liquid or other reactive matrix ) as the second layer . the second layer would be a thin coating of the active moiety sprinkled over the active tsp cream . this approach would provide a concentrated decontamination material at the surface of the barrier cream , which would accelerate the neutralization process of cwas coming in contact with the surface . alternatively , the first layer can be a thin coating of the active moiety followed by a second layer of the active tsp . evaluation of formulations was conducted with a decision tree network ( dtn ) that describes the path that active tsps follow during evaluation ( fig1 ). the dtn is divided into two pathways : one for vesicants and the other for nerve agents . within these pathways there are three blocks each with a decision point . the first block consists of a series of three mechanical ( in vitro ) modules used to determine the initial efficacy of candidate formulations and to eliminate non - effective candidates before animal testing , the second block consists of in vivo modules and the third block consists of an advanced animal module to determine the influence of time , water , sweat , and interactions with other products . the m8 paper test is used to evaluate the barrier resistance of liquid cwa challenges , including hd , pinacolyl methylphosphonofluoridate ( soman , gd ), and o - ethyl s -( 2 - diisopropylaminoethyl ) methylphosphonothioate ( vx ). in this test a 0 . 15 mm layer of active tsp is placed over a well - defined area of m8 chemical detection paper and challenged with an 8 μl droplet of cwa . when agent penetrates the active tsp barrier and reaches the m8 paper , a colored spot develops on the paper . the test assemblies are observed for 6 hr and the breakthrough time is reported for each sample . a total of nine replicates are run for each test , and a standard reference compound is included each day for quality control . the penetration cell test is used to evaluate the barrier properties against both liquid and vapor cwa challenges ( braue , e . h . jr . journal of applied toxicology , 1999 , 19 ( s ), s47 - s53 ). in this test the lower half of a reifenrath diffusion cell ( reifenrath consulting and research , richmond , calif .) is used . a 0 . 15 mm thick layer of active tsp is supported by nitrocellulose paper on top of the cell . the active tsp layer is challenged with a 10 - μl liquid droplet of hd or an 8 μl droplet of gd , or a saturated vapor cup of hd or gd . breakthrough of cwa into the lower chamber of the diffusion cell is monitored using a miniature continuous air monitoring system ( minicams , cms research , birmingham , ala .). this system has been automated to allow continuous monitoring of five cells in a 40 - min cycle . the test runs for 20 hr and the accumulated amounts of agent that break through the active tsp barrier are calculated . from these data , we obtained two values : the cumulative amount of cwa that penetrates through the active tsp , and the time at which a “ breakthrough ” occurs . we defined “ breakthrough ” values at the minimum amount of hd ( 1000 ng ) and gd ( 1000 ng ) that results in a physiological response . minimal amount of hd for vesication is 1000 ng . see f . r . sidell , j . s . urbanetti , w . j . smith , and c . g . hurst in textbook of military medicine , medical aspects of chemical and biological warfare , edited by f . r . sidell , e . t . takafuji , and d . r . franz ( office of the surgeon general at tmm publications , washington , d . c . 1997 ) p 201 . the ld 50 for soman ( gd ) is 350 mg / 70 kg man . see f . r . sidell in textbook of military medicine , medical aspects of chemical and biological warfare , edited by f . r . sidell , e . t . takafuji , and d . r . franz ( office of the surgeon general at tmm publications , washington , d . c . 1997 ) p 141 . these two values allow us to rank the active tsp formulations and to select the appropriate component for advanced development . the proof - of - neutralization test is used to verify that active tsp formulations actually neutralize cwas into less toxic materials . this test uses the headspace solid phase microextraction ( hs - spme ) technique for the collection of cwas . samples collected on the extraction filament are analyzed by gas chromatography / mass spectroscopy . 100 mg of active tsp formulation are challenged with 0 . 1 μl of neat cwa ( hd , gd , or vx ) in a small vial . the headspace above the mixture is sampled periodically to determine the amount of cwa remaining in the flask . efficacy is determined by the % loss of cwa . other analytical techniques such as nuclear magnetic resonance ( nmr ) and fourier - transform infrared spectrometry ( ftir ) have also been used in this module . formulations that pass this initial set of screens are moved into the second phase of testing using animal models . the weakling pig test for hd vapor evaluates a 0 . 15 mm thick layer of active tsp spread on the depilated dorsa . the standard saturated vapor cup is used for a 30 min challenge . the effectiveness of the active tsp is determined by measuring the degree of erythema that developed on the skin exposure site . erythema is measured objectively using a reflectance calorimeter ( see braue , e . h . jr . journal of applied toxicology , 1999 , 19 ( s ), s47 - s53 ). the rabbit lesion area ratio ( lar ) test is used to evaluate a challenge by hd liquid . in this test , a 0 . 15 mm layer of active tsp spread on the clipped dorsa is challenged with 1 . 0 μl of liquid hd spread by a 12 mm disk . the effectiveness of the active tsp is determined by measuring the lesion areas of protected and non - protected sites . the rabbit lethality test is used to evaluate a challenge by gd vapor . in this test , a 0 . 15 mm layer of active tsp spread on the clipped dorsa is challenged with two vapor cups ( 7 cm 2 each ) containing 28 mg gd per kg of body weight . the liquid gd is saturated onto filter paper fitted into the top of the cap so that liquid can not run down . the caps are left in place for 4 hours . after the exposure period the caps are removed and the exposure sites decontaminated . this exposure dose is lethal to all animals not protected with active tsp . the effectiveness of the active tsp is determined by lethality 1 , 2 , 3 , 4 and 24 hr following exposure . the guinea pig lethality test is performed by applying a 0 . 15 mm thick layer of active tsp on the clipped dorsa of guinea pig followed by a fixed dose of gd , tgd or vx . the effectiveness of the active tsp is determined by lethality 1 , 2 , 3 , 4 and 24 hr following exposure . candidate formulations that pass the in vivo test modules move into advanced animal testing . these tests are similar to the initial animal tests with the addition of stresses for wear - time and washing with a simulated sweat solution . interactions with other products that a warfighter might use are also evaluated . these products include camouflage paints , sunscreens and insecticides . the polyalkenimines are effective active moieties reducing the amount of hd vapor by & gt ; 99 % relative to the tsp alone . although the exact mechanisms for hd neutralization are not clear , they may react by hydrolysis , direct alkylation of the polyalkenimine , or dehydrohalogenation ( scheme 1 ). against gd vapor the polyalkenimines reduced the amount of gd by & gt ; 99 % compared to tsp alone . in this case , it is likely that the polyalkenimines are active as nucleophiles or else accelerate hydrolysis through general base catalysis ( scheme 2 ). many of the listed active tsps contain water , and the in model reactions with a gd simulant , diisopropylfluorophosphate , ( dfp ), the products have ft - ir and 31 p nmr spectra that are consistent with hydrolysis . another possibility is that adventitious adsorbed water in formulations that did not have water added directly act as a reagent for this hydrolysis . the increase in protection for the polyalkenimines was impressive against gd vapor as seen by the decrease in total ng that breakthrough the active tsp as compared to serpacwa ( icd3004 ) ( fig6 ). fig6 shows a total amount of gd vapor that penetrates a 0 . 15 mm thick atsp barrier in 20 hr . icd3004 ( serpacwa ) is off scale with a value of 6672 ng . many of the formulations reduce the amount of gd vapor by & gt ; 99 %. most samples display significantly ( p = 0 . 05 ) increased protection compared to serpacwa ( icd 3004 ) in the penetration cell model against gd vapor . the increase in protection for atsps formulations containing polyalkenimines was also remarkable against hd vapor as demonstrated by the decrease in total ng that break through the active tsp in 20 hours as compared to serpacwa ( icd3004 ) ( fig7 ). as clearly seen in fig7 , most of the formulations containing polyalkenimines have shown outstanding protection against hd vapor in the penetration cell model . many offer significantly better ( p = 0 . 05 ) protection against hd vapor compared to serpacwa ( icd 3004 ). to roughly determine the resistance of atsps containing polyalkenimines , the m8 paper test was performed . all formulations tested against hd liquid proved impervious over the duration of the test ( 360 min ) but showed variable resistance against gd liquid ( fig8 ). limited penetration cell testing has also been accomplished against hd and gd liquid . in this module , the aforementioned a tsps performed well against gd but were ineffective against hd ( fig9 ). in addition to the penetration cell model , certain active tsp containing polyalkenimines were tested in the headspace solid phase micro - extraction gas chromatography / mass spectrometry ( hs - spme / gc - ms ) test against hd . in this module significant efficacy was seen against hd , gd , and vx ( fig1 ). for fig1 , evaluation of active tsps containing polyalkenimines against hd , gd , and vx liquid using headspace solid phase micro - extraction gas chromatography / mass spectrometry ( hs - spme - gc / ms ). percent of control is the ratio ( expressed as %) of the headspace concentration of the cwa determined for each formulation divided by the headspace concentration determined for serpacwa . possible neutralization pathways of these amines , polyalkenimines , and derivatives were probed using nmr with diisopropylfluorophosphate ( dfp ) as a gd simulant and cees as an hd simulant . to determine the relative activity of different polyalkenimines towards organophosphates , the first experiments monitored the hydrolysis of dfp in deuterated water ( d 2 o ). 31 p nmr spectra were obtained displaying both the native dfp ( d , − 11 . 6 ppm ) and it hydrolysis product ( s , − 2 . 5 ppm ). these spectra were obtained at regular intervals over 14 hours ( fig2 ). the extent of hydrolysis was determined by taking the ratio of the integrations of the signals for dfp and its hydrolysis product . by plotting the percent hydrolysis versus time , we were able to perform an initial ranking of the polyalkenimines ( fig1 ). to determine the possible reaction pathways for the neutralization of hd by polyalkenimines , we performed a series of experiments measuring the degree of hydrolysis in an hd simulant , 2 - chloroethylethylsulfide ( cees ). first , we obtained the 1 h nmr spectra of cees in d 6 - dmso ( fig3 ). next , we added 100 equivalents of d 2 o to the nmr tube and obtained 1 h spectra after 18 hours giving us a baseline extent of hydrolysis ( fig4 ). finally , we prepared a standard solution of cees in d 6 - dmso and added a 2 . 5 wt % solution of polyalkenimine in d 2 o ( still 100 eq d 2 o ). peak at ˜ 4 . 1 ppm is from d 2 o , broad peak from 2 . 5 to 3 . 0 ppm is from the lupasol wf ( fig5 ). by comparing the spectra of cees , cees / d 2 o and cees / polyalkenimine / d 2 o , it is evident that significant hydrolysis occurs by the disappearance of cees signals ( 3 . 75 , 2 . 85 , 2 . 55 , 1 . 17 ppm ). most of the active tsps containing polyalkenimines also show excellent efficacy in the weanling pig hd vapor model ( table 2 ). the best active tsps containing polyalkenimines almost completely eliminated erythema in this test . all of the active tsps containing polyalkenimines tested against hd liquid in the lesion area ratio ( lar ) test showed significant ( p & lt ; 0 . 05 ) protection compared to un - protected skin ( fig1 ). lesion area ratio is the measure of the protection given by the atsp and compares the lesion size between sites protected by atsp with sites not protected by atsp . several of the formulations also demonstrate significantly improved protection compared to serpacwa ( icd3004 ). a limited number of the active tsps containing polyalkenimines were also tested in the rabbit lethality test for gd vapor . many show excellent efficacy . lethality at 1 , 2 , 3 , 4 and 24 hours post exposure from 2 vapor caps each containing 28 mg gd / kg for 4 hrs . ( fig1 ). a limited number of the active tsps containing polyalkenimines were also tested in the rabbit lethality test for vx liquid . lethality at 1 , 2 , 3 , 4 and 24 hr . post exposure to 0 . 5 mg vx / kg for 4 hrs . all were significantly ( p & lt ; 0 . 05 ) better than no protection ( fig1 ). having now fully described the invention , it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the spirit or scope of the invention as set forth herein .
a topical skin protectant formulation containing a barrier cream and an active moiety for protecting warfighters and civilians against all types of harmful chemicals , specifically chemical warfare agents . the active moiety is an amine , polyalkenimines and / or derivatives . the topical skin protectant offers a barrier property and an active moiety that serves to neutralize chemical warfare agents into less toxic agents .