| United States Patent Application |
20030035848
|
| Kind Code
|
A1
|
|
Batarseh, Kareem I.
; et al.
|
February 20, 2003
|
Microbicidal formulations and methods to control microorganisms
Abstract
Microbicidal formulations are described which are preferably ecologically
friendly and non-toxic to mammals, and are highly effective against a
broad spectrum of detrimental pathogenic microorganisms. The microbicidal
formulation contains complexes having the formula R-M, wherein R is at
least one organic chelating moiety and M is at least one metal ion which
is microbicidal to at least one microorganism. These complexes can
disrupt microorganism activities by penetrating the natural protecting
bio-films of such microorganisms through the reaction of the R-group with
the organic constituents of these microorganisms while releasing M into
their intra-cellular media. Thus, this process exhibits its biocidal
activities from the inside-out, contrary to other methods which rely on
damaging the protective biofilms. These microbicidal formulations can be
diluted in suitable proportions into aqueous systems to produce the
desired dosages for each individual case, depending on the level and the
severity of the contamination. The microbicidal formulations can be
applied by conventional methods, e.g., spraying, soaking, fogging,
impregnation, and the like. The formulations can also be used as
preservatives, such as for fresh or cut flowers and plants. These
microbiocides can also be made as gel or solids in different forms by
using techniques available to those skilled in the art.
| Inventors: |
Batarseh, Kareem I.; (Fairfax Station, VA)
; Ai-Kayed, Marwan; (Naur, JO)
|
| Correspondence Name and Address:
|
KILYK & BOWERSOX, P.L.L.C.
53A Lee Street
Warrenton
VA
20186
US
|
| Serial No.:
|
761561 |
| Series Code:
|
09
|
| Filed:
|
January 17, 2001 |
| U.S. Current Class: |
424/618; 514/184; 514/495 |
| U.S. Class at Publication: |
424/618; 514/184; 514/495 |
| Intern'l Class: |
A61K 033/38; A61K 031/555; A61K 031/28 |
Claims
What is claimed is:
1. A microbicidal composition comprising a complex of the formula R-M,
wherein R is at least one organic chelating moiety and M is at least one
metal ion, and where R is present in an at least equimolar amount based
on the amount of M, and M is microbicidal to at least one microorganism.
2. The microbicidal composition of claim 1, further comprising an aqueous
solution.
3. The microbicidal composition of claim 1, wherein said at least one
metal ion is a silver ion or
colloidal silver or both.
4. The microbicidal composition of claim 1, wherein said at least one
metal ion of copper, zinc, mercury, chromium, manganese, nickel, cadmium,
arsenic, cobalt, aluminum, lead, selenium, platinum, gold, titanium, tin,
barium, vanadium, bismuth, iron, strontium, antimony, and the like, and
combinations thereof.
5. The microbicidal composition of claim 1, wherein said at least one
organic chelating moiety comprises at least one amino acid.
6. The microbicidal composition of claim 1, further comprising at least
one disinfectant.
7. The microbicidal composition of claim 1, wherein said at least one
organic chelating moiety is formed from an alpha-amino acid.
8. The microbicidal composition of claim 1, wherein said at least one
organic chelating moiety is selected from isoleucine, phenylalanine,
leucine, lysine, methionine, threonine, tryptophan, valine, alanine,
glycine, arginine, histidine, and mixtures thereof.
9. A method to control the growth of microorganisms comprising contacting
the microorganisms with a microbicidal composition comprising the
microbicidal composition of claim 1, and wherein said composition kills
said microorganisms intracellularly.
10. A method to control biofouling in a system, comprising introducing an
effective amount of said microbicidal composition of claim 1 to said
system to control said biofouling.
11. The microbicidal composition of claim 1, wherein the molar ratio of R
to M is from about 1:1 to about 2:1.
12. The microbicidal composition of claim 2, wherein said microbicidal
composition is present in said aqueous solution at a concentration of
from about 0.001% to about 10% by total volume.
13. A method to prepare the microbicidal composition of claim 1 comprising
dissolving a salt containing metal in at least one inorganic acid and an
aqueous source; and adding at least one organic chelating compound
containing R to form a metal complex having the formula R-M, wherein the
preparation of the composition occurs at a pH of about 2.0 or less.
14. The microbicidal composition of claim 6, wherein said at least one
disinfectant comprises one or more of chlorhexidine gluconate,
chlorhexidine digluconate, chlorhexidine dihydrochloride, and
chlorhexidine diacetate.
15. The microbicidal composition of claim 6, wherein said at least one
disinfectant comprises one or more of isopropyl alcohol and hydrogen
peroxide.
16. A microbicidal composition comprising a product obtained by combining
at least one metal ion (M) with at least an equimolar amount of at least
one organic chelating moiety (R) based on the amount of M, wherein M is
microbicidal to at least one microorganism.
17. The microbicidal composition of claim 16, wherein said at least one
organic chelating moiety comprises an amino acid.
18. The microbicidal composition of claim 16 wherein said at least one
metal ion is a silver ion or
colloidal silver.
19. A method to control the growth of a microorganism susceptible to
treatment with a metal ion, said method comprising: treating said
microorganism with the microbicidal composition of claim 16.
20. A method of controlling biofouling in a system, comprising introducing
to said system an effective amount of the microbicidal composition of
claim 16.
21. A microbicidal composition comprising a complex of the formula R-M,
wherein R is at least one organic chelating moiety and M is at least one
metal ion, and where R is present in an at least equimolar amount based
on the amount of M, and M is microbicidal to at least one microorganism,
wherein said at least one organic chelating moiety is formed from an
amino acid, and said organic chelating moiety has a carboxylic group
which forms a dative covalent bond with M.
22. The microbicidal composition of claim 21, wherein M is complexed
through the doubled bonded oxygen of the carboxylic group.
23. A method for preserving cut flowers or plants from pathological
microorganisms comprising: treating said flowers and plants with the
microbicidal composition of claim 1.
24. The method of claim 23, wherein the flowers and plants are treated by
immersing a portion of the flower or plant in an aqueous solution of the
composition of claim 1.
25. The method of claim 23, wherein the flowers and plants are sprayed
with an aqueous solution of the composition of claim 1.
26. A method for protecting living flowers or plants comprising treating
said flowers and plants with the microbicidal composition of claim 1.
27. The method of claim 23, wherein the flowers or plants are treated by
introducing into a container of water a tablet comprising the
microbicidal composition of claim 1.
28. A microbicidal composition comprising an organo-metallic chelate of
silver cations and glutamic acid cations, wherein the chelate exhibits
the structural spectra depicted in FIGS. 1, 2, or 3, or combinations
thereof.
29. The microbicidal composition of claim 1, further comprising artificial
or natural colors or flavors.
30. The microbicidal composition of claim 1, wherein said composition is a
gel or solid.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/294,143, filed Apr. 20, 1999, and also is a
continuation-in-part of International Patent Application No.
PCT/US00/10665, both incorporated herein in their entirety by reference.
FIELD OF THE INVENTION
[0002] The present invention relates in general to controlling
microorganisms and more particularly relates to microbicides which are
preferably environmentally friendly and non-toxic to mammals and which
are highly effective against viruses, amoebea, bacteria (both
gram-negative and -positive), fungi, algae, spores, and the like. The
present invention specifically relates to organo-metallic microbicidal
formulations; their microbicidal applications, and methods of
preparation.
BACKGROUND OF THE INVENTION
[0003] Water is the most important element of life since it comprises
almost 80% of the human body. In addition, food hygiene depends solely on
water, and therefore contamination of water is a common vehicle for the
transport of epidemic diseases to humans like Typhoid, food poisoning,
and Dysentery. For example, Psychrophilic bacteria's presence in the
micro-flora in water can affect refrigerated food and spoil it. Hence,
water contamination cannot be overlooked and extreme measures should be
taken to assure a high quality of water to sustain life.
[0004] With the advent of technology, clean water is becoming a scarce
commodity. Water contamination is unequivocally becoming a worldwide
problem with unknown ramifications, and billions of U.S. dollars are
spent annually to improve its quality. Contamination of waters is not
only restricted to industrialized countries, but includes developing
nations as well. Therefore, there is an immediate need to find poignant
solutions to maintain and preserve water sources.
[0005] Recently, there has been a growing interest among scientists and
engineers to develop new water and food disinfectant technologies to
clean water from dangerous microorganisms. Various methods have been
employed which are divided into two categories; namely, physical,
chemical, or both. The physical category is represented by techniques
utilizing ultrafiltration, reverse osmosis, radiation, freezing, heating,
and ultrasound. Although these methods have proved to be effective, the
drawbacks include the large electricity requirements and expensive
equipment. On the other hand, the chemical category relies on the use of
chemical adjuvants which exhibit biocidal properties such as aldehydes,
phenols, alcohol, potassium permanganate, and chlorine and certain
chlorine containing compounds. Some of these chemicals have many
disadvantages associated with them and are now considered poisonous
compounds. For instance, people coming into contact with these substances
can develop skin irritation and suffer from long time illnesses which in
some cases can be fatal; not to mention the unpleasant taste and odor
associated with these chemicals. In addition, formation of mutagenic and
carcinogenic agents, and genetic resistance are also some of their
disadvantages. Notwithstanding, such compounds have afforded a way to
battle these harmful microorganisms and their effectiveness have been
unequivocally demonstrated.
[0006] Other methods have relied upon the use of ultra-violet irradiated
silver fluoride solutions containing silver as a source of germicide
activities, such as U.S. Pat. No. 3,422,183, incorporated herein in its
entirety by reference. However, such techniques require expensive
equipment and large amounts of electricity.
[0007] Hydrogen peroxide is a strong oxidizing agent, and it has been used
for the past 40 years as a disinfectant. Its main advantage is that it
does not produce toxic residue or by-products. It has been used
ubiquitously as an indirect food additive, as a disinfectant in
hospitals, as a decontamination and purification agent of industrial
waste water, and as a cleaning agent for exhaust air. Nonetheless, it
decomposes readily to form water and oxygen, and has high sensitivity to
sunlight and UV rays. Therefore, it is not suited for long-term use since
recontamination cannot be circumvented.
[0008] In 1880, the Swiss botanist Carl van Nageli observed that highly
diluted silver solutions have an algicidal effect. To describe this
effect he coined the term "Oligodynamic".
Colloidal silver, which is a
pure, all-natural substance consisting of sub-microscopic clusters of
silver ions held in suspension in de-ionized water by tiny positive
charges on the silver ions, is a powerful prophylactic antibiotic which
was used for years with no known side effects. It acts as an inhibitor
disabling particular enzymes which bacteria, fungi, and viruses used in
their mode of metabolism.
[0009] Based on this oligodynamic property, U.S. Pat. No. 4,915,955,
incorporated in its entirety herein by reference, combines the germicidal
effects of hydrogen peroxide with silver, an inorganic acid, and an
organic stabilizer at concentrations of 10-35 mg/l against many forms of
bacteria and viruses. The process is based on silver ions, with the aid
of hydrogen peroxide, damaging the protective biofilms of these
microorganisms. Hence, this method depends solely on killing germs
intercellularly. Accordingly, there is a need to develop a new generation
of microbicidal agents that overcome one or more of the above-described
disadvantages.
SUMMARY OF THE INVENTION
[0010] The present invention relies on using metal ions (M). A chemical
matrix or complex is formed wherein these metal ions are attached to an
organic-chelating moiety (R), to be used in stoichiometric amounts or
more to form complexes, which serves as carriers for M into the
intra-cellular medium of such microorganisms. These concentrated
complexes can then be mixed with water to form suitable disinfectants.
This process is different from previous methods found in the literature
where the metal ion remains freely suspended in solution.
[0011] A particularly useful application of the disinfectant of the
present invention is in the preservation of flowers and plants, as a
general disinfectant, sterilization of articles and surfaces and areas,
including, but not limited to, food, liquids, (e.g., water, beverages),
animal feed, pharmaceuticals, hospitals, surgical equipment, swimming
pools, saunas, fish, poultry, cattle, and other farming uses, and the
like.
[0012] It is to be understood that the preceding general discussion and
the discussion which follows are considered explanatory and exemplary in
nature, and are solely intended to give additional merits of the current
invention, as claimed.
DESCRIPTION OF THE FIGURES
[0013] FIG. 1 is a differential scanning calorimetry spectrum of a
silver-glutamic acid organo metallic complex of the present invention.
[0014] FIG. 2 is a proton NMR spectrum of the silver-glutamic acid
organo-metallic complex of the present invention.
[0015] FIG. 3 is a carbon NMR organo-metallic complex of the present
invention.
[0016] The present invention may be more fully understood with reference
to the accompanying figures. The figures, which are incorporated in and
constitute a part of this specification describe the physical properties
of an embodiment of the present invention and together with the
description, serve to explain the principles of the present invention.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0017] The present invention provides a suitable concentrate of
organo-metal compounds that form suitable disinfectants upon admixing
with water or other aqueous sources. The basic principle that governs the
formation of such a concentrate is the fact that the metal ions are
attached to an organic-chelating R group used in stoichiometric amounts
or more that forms organic complexes. These organic complexes can
penetrate the protective biofilms of germs and other microorganisms. Once
the R-M complex is inside the biofilm, it can then exhibit its germicidal
or biocidal effects by releasing M into their intra-cellular media and,
hence, disrupt microbial activities. In the most general terms, this
scenario can be depicted as giving these germs a "poisonous pill." Thus,
unlike other methods which attribute their biocidal effects through
damaging the protective biofilms (from the outside-in, i.e.,
inter-cellularly), the present invention does the opposite; specifically,
killing microorganisms from the inside-out, i.e., intracellularly.
[0018] To enhance its activity, the concentrated organic complex can be
mixed with other disinfectants, including, but not limited to,
isopropanol, chlorhexidine gluconate, chlorhexidine digluconate,
chlorhexidine dihydrochloride, chlorhexidine diacetate, and/or hydrogen
peroxide, though it is not necessary. In addition, natural and artificial
color and flavor additives as well as other additives can be added as
well.
[0019] Of course, the microbicidal formulations of the present invention
can be used either directly, by introduction to a system, e.g., a
swimming pool, or can be diluted with aqueous solutions, like distilled
and/or deionized water to provide the necessary biocidal activity,
depending on the application.
[0020] With respect to the organic complex, R-M, the R group is an organic
group which can complex with one or more metal ions, and is preferably a
group which is amphoteric. Also, the R group is preferably of a chemical
nature which microorganisms would find nurishable. Preferably, the R
group includes at least one amino acid or can be formed from at least one
amino acid.
[0021] The amino acids are preferably amphoteric, that is, they can react
either as acids or as bases, depending on the circumstances. They exist
primarily as neutral dipolar ions or zwitterions (Z.dbd.H.sub.3N.sup.+--C-
RH--COO.sup.-). Hence, at low pH, the zwitterions exist as cations, and at
high pH they exist as anions; therefore at a certain pH, the amino acids
preferably exist primarily as zwitterions. This point is called the
isoelectric point which depends on the structure of the given amino acid.
Primary, secondary, or tertiary amines can all be used here as long as
the amine is compatible with (M) in the formation of the complex. The
amino acids are preferably chosen so as to make use of the lone pair of
electrons on the nitrogen atom where the metal ions (the Lewis acid,
electron pair acceptor) can form dative covalent bonds (also known as a
coordinate covalent bond) with the carboxylic group of the amino acid. In
essence, these metal ions, or Lewis acids, can share an electron pair
donated by the amino acid, that is, the ligand, or Lewis base.
Preferably, the double bonded oxygen of the carboxylic group of the amino
acid is complexed (or forms a dative covalent bond with the double bonded
oxygen) to the metal (M), and not to the hydroxy group of the carboxylic
group of the amino acid. This is preferably accomplished by forming the
complex under low pH conditions (e.g., acidic conditions) and preferably
at pH conditions of pH 2.0 or less and more preferably at a pH 1.5 or
less.
[0022] Preferably, examples of amino acids or compounds containing amino
acids which can be used as the R group or to form the R group include,
but are not limited to, .alpha.-amino acids. Specific examples include,
but are not limited to, isoleucine, phenylalanine, leucine, lysine,
methionine, threonine, tryptophan, valine, alanine, glycine, arginine,
histidine, hydroxyproline, .alpha.-aminobutyric acid, asparagine,
aspartic acid, cysteine, glutamic acid, glutamine, pherylalanine,
proline, serine, tyrosine, and derivatives thereof and mixtures thereof.
[0023] With respect to the other part of the complex which is M, M
represents at least one monovalent or polyvalent metal ion or cation,
which is microbicidal to at least one microorganism. Preferably, the
metal ion is microbicidal to a multitude of microorganisms. Examples of
the metal ion include, but are not limited to, cations of silver
including
colloidal silver, copper, zinc, mercury, manganese, chromium,
nickel, cadmium, arsenic, cobalt, aluminum, lead, selenium, platinum,
gold, titanium, tin, barium, bismuth, vanadium, iron, strontium,
antimony, and the like. More than one type of R group and more than one
type of M can be used to form the R-M complex, also, mixtures of
different R-M complexes can also be used.
[0024] The composition provided here may be prepared from various
complexes that may form together a more complicated complex and/or
complexes. The aqueous solution obtained may be concentrated and dried,
and the concentrate can be made as a gel or solid in different forms
using conventional methods available to those skilled in the art.
[0025] The complex of the present invention can be prepared by forming the
metal ion from at least one metal salt compound and the organic chelating
moiety from at least one organic compound which is preferably at least
one amino acid. In the preferred process of making the organic complex of
the present invention, a metal salt compound is mixed with at least one
inorganic acid preferably at room temperature (e.g., about 20.degree. C.
to about 30.degree. C.) and preferably in the presence of an aqueous
solution like a distilled and deionized water. Then, at least an
equimolar basis of the organic containing compound such as an amino acid
is added to form the metal complex preferably while homogenizing the
mixture. This preparation preferably occurs under low pH conditions, such
as pH of about 2.0 or less and more preferably at a pH of 1.5 or less.
The resulting solution can then be further diluted with aqueous solution
and preferably distilled and deionized water and further disinfectants or
other additives can be added to form the microbicidal compositions of the
present invention. Other parameters can vary, such as the temperature for
preparation purposes.
[0026] According to the present invention, controlling the growth of at
least one microorganism includes both the reduction and/or prevention of
such growth. It is to be further understood that by "controlling," the
growth of at least one microorganism is inhibited. In other words, there
is no growth or substantially no growth of at least one microorganism.
"Controlling" the growth of at least one microorganism includes
maintaining a microorganism population at a desired level (including
undetectable levels such as zero population), reducing a microorganism
population to a desired level, and/or inhibiting or slowing the growth of
at least one microorganism. Thus, materials and mediums susceptible to
attack by at least one microorganism are preserved and/or protected from
this attack and the resultant deleterious effects. The present invention
also provides a method for controlling the growth of at least one
microorganism in or on a material or medium susceptible to attack by the
microorganism which comprises the step of adding to the material or
medium a composition of the present invention in an amount effective to
control the growth of the microorganism.
[0027] The mode as well as the rates of application of the composition of
this invention could vary depending upon the intended use. The
composition could be applied by spraying or brushing onto the material or
product. The material or product in question could also be treated by
dipping in a suitable formulation of the composition. In a liquid or
liquid-like medium, the composition could be added into the medium by
pouring or by metering with a suitable device so that a solution or
dispersion of the composition can be produced. As these terms are used
herein, "preventing" (which includes mitigating) spoilage or effects is
to be understood that the present invention in effect "controls" the
growth of at least one microorganism, responsible, at least in part, for
the spoilage. It is to be further understood that by "controlling" (i.e.,
preventing), the growth of at least one of these types of microorganisms
is inhibited. In other words, there is no growth or essentially no growth
of at least one microorganism. "Controlling" the growth of at least one
microorganism maintains the microorganism population at a desired level,
reduces the population to a desired level (even to undetectable limits,
e.g., zero population), and/or inhibits the growth of the microorganism.
Thus, the substrates or materials susceptible to attack by these types of
microorganisms are preserved from this attack and the resulting spoilage
or other detrimental effects caused by the microorganisms. Further, it is
to be understood that "controlling" the growth of at least one
microorganism also includes biostatically reducing and/or maintaining a
low level of microorganisms such that the attack by microorganisms and
any resulting spoilage or other detrimental effects are mitigated, i.e.,
the microorganism growth rate or microorganism attack rate is slowed down
or eliminated.
[0028] Microorganisms, as used herein, include, but are not limited to
bacteria, (both gram-positive and-negative), fungi, algae, viruses,
amoebae, spores, and the like, and include both yeast and molds.
[0029] Preferably, at least an equimolar portion of the chosen amino acid
is used in preparing the solution, preferably in excess of the sequester
univalent metal ions (e.g., Ag); at least twice as much for bivalent
metals (e.g. Cu), and so on. Any source of ionic M in the form of salts
can be used in the present invention. For the case of silver,
colloidal
silver can be used as well.
[0030] The aqueous solution may be condensed and dried using conventional
methods available to those skilled in the art to produce gels, tablets,
or powders.
[0031] The biocides or microbicidal compositions of the present invention
described herein have a plethora of applications and uses. They are
suitable for the sterilization of drinking water, suitable for the
beverage and food industry, suitable for sterilizing exposed surfaces,
exhaust air and ventilation components, animal feed, suitable for use in
the pharmaceutical industry, in hospitals, for surgical equipment, in
swimming pools, in saunas, and for fish, poultry, and cattle farming, and
the like.
[0032] The present invention is also effective in controlling biofouling.
The microbicidal formulations of the present invention can be introduced
directly into the source of where the biofouling is occurring or can be
mixed with aqueous solutions and introduced into the area where
biofouling is occurring by employing methods known to those skilled in
the art.
[0033] Another beneficial use of the present invention is with respect to
preserving or extending the life of flowers and plants. The present
invention can be used as a preservative for cut flowers and cut plants by
including the formulation of the present invention in the water in which
the cut flowers or plants are placed into or can be formulated into a
powder or tablet which can be introduced into the containing holding the
cut flowers or plants. Also, the formulations of the present invention
can be used as a spray which is applied to living plants and flowers and
acts as an agent to control pests, insects, and/or microorganisms and
thus preserves a living plant and protects the plant from plant diseases,
bacteria, viruses, fungus, algae, insects, and the like. The amount of
the formulation which is used depends upon the plant or flowers and as
described above, is typically a diluted aqueous formulation containing
the microbicidal compositions of the present invention.
[0034] The present invention is further illustrated by the following
examples. These experiments constitute some of the embodiments of the
invention herein disclosed. After the preparation of these disinfectants
according to the present technique, their efficacy with respect to
toxicity was then tested and evaluated against a broad spectrum of
pathogenic microorganisms.
[0035] METHODOLOGY
[0036] I. Chemical
[0037] Under minimum light, and at room temperature, a silver ion solution
of 1.1.times.10.sup.5 ppm was prepared by dissolving 400 mg of silver
nitrate in 2.045 ml of double distilled-de-ionized water and 0.255 ml of
85% phosphoric acid. This solution was then used for the proceeding
experiments.
EXAMPLE 1
Preparation of Silver-glutamic Acid Complex
[0038] By using a micropipet, 230 .mu.l of the above prepared solution was
placed in a microtube where 34.61 mg of glutamic acid was added, and the
mixture was stirred thoroughly. This amount of glutamic acid represents
an equimolar amount of amino acid with respect to the silver ions in the
above prepared solution. Instantly, an insoluble material was observed.
This insoluble dispersant has microbial killing activities. This prepared
solution was then mixed with 50 ml of double distilled-de-ionized water.
The solution was mixed continuously until homogenization was achieved.
Then, the product was poured into a dark bottle. This desired product can
be added to or proportioned into aqueous systems and diluted to achieve
the required germicidal potency, depending on its intended use.
EXAMPLE 2
Preparation of Silver-Leucine Complex
[0039] The same procedure in Example 1 above was duplicated, but the amino
acid used was leucine instead of glutamic acid. The amount of leucine
used in this case was 30.84 mg which again represents an equimolar amount
of the amino acid with respect to the silver ions.
EXAMPLE 3
Preparation of Silver-Arginine Complex
[0040] The same procedure from Example 1 was again repeated, but the amino
acid used was arginine. The amount of arginine used in this case was
40.97 mg which again represents an equimolar amount.
[0041] To study the effect of hydrogen peroxide on increasing the potency
of these disinfectants, the three prepared solutions (Example I-III) were
mixed with 50 ml of 50% H.sub.2O.sub.2 rather than water. Again, these
prepared solutions were poured into dark bottles.
[0042] II. Biological
[0043] 1. Efficacy of Examples 1-3 Disinfectant
[0044] The above concludes the preparation of these disinfectants.
However, to utilize these mixtures as bactericides, 5 ml of each bottled
solution was added to 45 ml of double distilled-de-ionized water (10% by
volume). Without the presence of H.sub.2O.sub.2, this constitutes an
active concentration of about 51 ppm of complex silver which proved to be
sufficient to readily kill bacteria. The upper and lower concentration
limits may be different if desired, depending on the nature of the
desired application. For the samples where H.sub.2O.sub.2 is present, the
active concentration of the disinfectant should be around 56,000 ppm.
[0045] The diluted solutions were then tested on several kinds of actively
growing pathogenic bacteria to ascertain their effectiveness. Different
strains of pathogenic bacteria were employed for the testing; namely, E.
coli, Stafelococus, Bascillus, and Salmonella. For all the bacteria used,
the microbial killing activity was readily observed. The arginine-complex
showed the most potency followed by the leucine-complex, and finally the
glutamic acid-complex.
[0046] With respect to the presence of H.sub.2O.sub.2 in relation to its
absence, the difference on the average was roughly around 3 times greater
even though the active concentration was almost 1098 times greater than
that for the case of an absence of H.sub.2O.sub.2. The difference in
biocidal activity is not reflected in this value (1098 times greater
while the increase is tripled). This is indicative that the biocidal
activity is almost solely due to the R-M complex of the present
invention. The order of efficacy with respect to the amino acid used was
the same as when H.sub.2O.sub.2 was absent.
[0047] 3. Organo-Metallic Disinfectant or Preservative for Cut Flowers and
Plants
[0048] A sample was prepared in accordance with the procedure described in
Example 1, where the resultant disinfectant was diluted with tap water,
and was used to study its effects on the preservation of cut flowers and
plants. A silver concentration of approximately 166 ppb was used. Both
inoculated and controlled samples were tested in which freshly-cut roses
were placed in the prepared solution and tap water, respectively. Cut
roses were chosen because they are very susceptible to slight changes in
the surrounding area and are equally susceptible to chemicals. For
comparative purposes, other preservative type chemicals were also tested;
namely, silver thiosulfate and hypochlorite.
[0049] All the samples were examined after 15 days, and it was found that
the present invention is far more superior than all the other chemicals
used, including the controlled samples, in that there were no black or
brown burns on the petals and there were no wilted flowers, and the stems
and leaves were in good condition. In the case of the two other chemicals
used, it was observed that there was discoloration of the petals, loss of
leaves and petals, and dehydration.
[0050] III. Structural Analysis of Microbicide
[0051] Following the procedure described in Example 1, a sample of
silver-glutamic acid complex was prepared and analyzed as follows:
[0052] Under minimum light, and at room temperature, an aliquot of silver
ion solution of 1.1.times.10.sup.5 ppm was prepared by dissolving 2.0 g
of silver nitrate in 10.225 ml of doubled distilled-de-ionized water and
1.275 ml of 85% H.sub.3PO.sub.4. Following that, on an equimolar basis
with respect to silver, 1.73 g of glutamic acid was added to the solution
where the solution was thoroughly mixed and homogenized. Instantly, a
yellowish-tan insoluble precipitate was observed. The liquid of the
aqueous amino acid/silver sample was then decanted from the yellowish-tan
solid. The solid was dried in an oven. This sample was submitted for
structural analyses of the precipitates.
[0053] A. DSC Analyses: (Perkin-Elmer/DSC Series 7)
[0054] DSC is a technique used to analyze material when heated. It is used
to study the thermal transitions of a certain material as functions of
temperatures and heat flows. Such measurements provide quantitative as
well as qualitative information about the chemical, i.e., melting point
temperature and heat of melting, glass transition temperature,
crystallization studies, and identification of phase transformation.
[0055] Accordingly, three events were observed: the first two were
exothermic transitions at 184.degree. C. and 250.degree. C. The last
occurrence was an endothermic melting transition at 352.degree. C. This
is depicted in FIG. 1.
[0056] B. NMR Analyses:
[0057] Nuclear Magnetic Resonance Spectroscopy (NMR) is an important
method for material characterization. The importance of NMR arises in
part because the signal can be assigned to specific atoms. The properties
of NMR signals depend on the magnetic environment of the NMR active
nuclei and the local fields they experience. Since the NMR spectrum is
determined by local forces, this method provides valuable information at
an atomic scale.
[0058] Another portion of this solid was subjected to NMR studies using
Bruker/AC270. It was found, however, that this material was insoluble in
water (acid), dimethylsulfoxide, tetrahydrofuran, and dimethylformamide.
Another portion of this solid was then mixed with dilute sodium
deuteroxide (NaOD) in deuterium oxide (D.sub.2O). The yellowish-tan solid
soon turned black as the silver "crashed out" the solution. The resulting
mixture was subjected to proton and carbon NMR analyses; this is shown in
FIGS. 2 and 3, respectively. Characteristic resonances of the amino acid,
which was glutamic acid, were observed.
[0059] In the proton NMR spectrum (FIG. 2), the glutamic resonances were
found at 3.07 (dd, --CH.sub.2CH(NH.sub.2)C(O)--), 2.04 (t,
--CH.sub.2CH.sub.2C(O)--) and 1.66 (m, --CH.sub.2CH.sub.2CH--) ppm. The
.sup.13C NMR spectrum (FIG. 3) confirmed the presence of glutamic acid
with resonances at 185.01 (HOC.sub..delta. (O)--), 36.31
(--CH.sub.2C.sub..gamma.H.sub.2C(O)--), 33.98 (--CH.sub.2C.sub..beta.H.su-
b.2CH--), and 58.10 (--CH.sub.2C.sub..alpha.H(NH.sub.2)C(O)--) ppm.
However, the other carbonyl resonance was not observed. Thus, the sample
appears to be comprised of glutamic acid coordinated to silver.
[0060] C. Results
[0061] As stated earlier, the DSC results show two exothermic transition
states (troughs) and one endothermic melting transition state (peak),
FIG. 1. Careful examination of FIG. 1 reveals some interesting and novel
features: A) this material appears not to exhibit a glass transition
state which is only observed for amorphous materials (materials whose
chains are not arranged in an orderly manner, but are just strewn around
in any fashion; i.e., random) because the DSC profile is smooth and
lacking a sudden jump in temperature and heat flow which is a signature
of this state; B) since only exothermic transition states were observed,
there appears to be no glass transition state, and the material may be
composed of crystals only, and therefore maybe in a crystalline state
(materials that are arranged in an orderly manner); and C) two exothermic
states appear to take place at two distinct temperatures at 184.degree.
C. and 250.degree. C. This is somewhat unusual since it may imply that
there are may be two distinct crystalline structures with two different
crystalline temperatures in the material, or there may be chemical
interactions that are taking place such as a decomposition, or chemical
reactions.
[0062] The proton NMR provided in FIG. 2 shows three different resonances.
Several of these protons are enantiotopic, due to the chiral center of
glutamic acid, which in turn complicates the spectrum. The two carboxylic
acid protons are not observed since the experiment was conducted in
deuterated water.
[0063] The .sup.13C spectrum shown in FIG. 3 appears to confirm the
presence of glutamic acid. However, the fact that the other carbonyl
carbon was not observed, and possibly the silver may have distorted
and/or disrupted this bond.
[0064] On the bases of the above experimental observations, it can be seen
that such complexes demonstrate novel and peculiar structural
characteristics and features.
[0065] Although the present invention has been described with reference to
certain preferred embodiments, other variations are possible. Therefore,
the spirit and scope of the appended claims should not be limited to the
description contained herein.
[0066] The previous explanation and the illustrations and procedures set
forth above are solely intended for the purpose of setting out the
generic and general embodiments of the present invention. Therefore, it
is to be understood that the present invention by no means is limited to
the specific features disclosed herein, and such details can be varied by
those skilled in the art in consideration of the present specification
and practiced without departing from the true scope and merits of the
invention.
[0067] Having thus described the present invention, the true scope and
spirit of it is therefore presented by the following claims:
