Note: Descriptions are shown in the official language in which they were submitted.
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HYPERTONIC AQUEOUS SOLUTIONS OF POLYBAS1C ACID SALTS
Background
Field of the lnvention
The present invention relates to novel simple salt solutions of one or two
polybasic acids with at least three acid functionalities having a pH between
about 1 and
3 and an ionic strength exceeding 5~. The novel solutions of the present
invention are
useful for a number of applications, including, but not limited to, use as a
cold sterilant,
disinfectant and antiviral agent.
2: Description of the Background
Low pH acidic compositions consisting essentially of combinations of
strong inorganic acids and weaker organic acids and having an overall pH of
less than
2 have been described as being suitable for use in various pharmaceutical,
biomedical and
industrial applications (U.S. Patent 5,512,200, 1996, and cited patents
therein). These
compositions are described as multicomponent solutions of acids having a range
of
dissociation constants, thereby allowing for the formation of conjugates
between the
strong acids and the relatively weak acids. These multicomponent solutions
typically
contain four acids or more. In addition to requiring a multiplicity of
components, these
compositions also appear to require an exceptionally low pH to be effective in
many of
the claimed applications. As a result of the complexity of the compositions
and their
exceptionally low pl-I requirement, their utility is limited.
Summary of the Invention
The present invention overcomes the limitations of existing formulations
and provides for simpler solutions with a broader pH range useful in a number
oftailored
applications. Such solutions are more effective than conventional solutions,
at least in
part, as a result of controlled use of their hypertonicity.
More specifically, the present invention is directed to simple salt solutions
containing one or two polybasic acids with at least three acid
functionalities. The
solutions of the invention have a pI-1 between about 1.0 and 3.0 and an ionic
strength
exceeding S~c. These solutions are useful for a number ofapplications,
including, but not
limited to, use as a cold sterilant, disinfectant, or antiviral agent.
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Accordingly, one embodiment of the invention is directed to a hypertonic
aqueous solution containing one or two polybasic acids and a base. The acids
each have
at least three acid functionalities per molecule. The base is added in an
amount sufficient
to at least partially neutralize the solution to achieve a pH of between about
1 to about
3 and an ionic strength of at least S~c.
Another embodiment is directed to a method for inhibiting viability of
biological organisms, such as bacteria, virus or fungus, on a surface
comprising
contacting the surface with an aqueous solution according to the invention for
a period
of time effective to sterilize, disinfect or otherwise inhibit the viability
of the biological
1 U organisms on the surface.
Other embodiments and advantages of the invention are set forth in
part in the description which follows, and in part, will be obvious from this
description, or may be learned from the practice of the invention.
Description of the Invention
1 S The present invention is directed to hypertonic aqueous solutions of
polycarboxylic acid salts, and more specifically, to hypertonic aqueous
solutions of one
or two polybasic acids with three or more acid functionalities per molecule
that are
partially neutralized with an inorganic or organic base to achieve a pH
between about
l to about 3 and an ionic strength of more than S~. The one or two polybasic
acids may
20 be selected from the group consisting of phosphoric acid, citric acid,
isocitric acid,
polyacrylic acid, an N-succinylated chitosan, hyaluronic acid, alginic acid,
and
carboxymethyl cellulose.
In a preferred embodiment, the solution of one or two polybasic acids
and a base is a mixture of citric acid or phosphoric acid, partially
neutralized with an
25 inorganic base. For example, one preferred composition uses only citric
acid and a base,
such as zinc oxide. Another preferred solution is a mixture of phosphoric acid
and a
base, such as zinc oxide. The latter is particularly useful as a cold
sterilant.
Other preferred compositions are based on a mixture of both citric and
phosphoric acids and a base, such as zinc oxide.
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In a preferred embodiment, the solution comprises a cationic component
of the salt. The cationic component is preferably a monovalent cation such as
Na' and
K' or a divalent canon such as Mgl2 and 7,n'2, or mixtures of them. In a
preferred
embodiment, the cationic component is comprised of both Na' and Zn~ Z.
Alternately, in
S another preferred embodiment, the solution may comprise citrate anions and
Zni2. For
example, in one preferred embodiment, the solution comprises 30 percent citric
acid by
weightlvolume that is partially neutralized with zinc oxide. This embodiment
is also
particularly useful as a cold sterilant. The solutions ofthe present invention
may be used
in a number of applications, including, but not limited to, as a cold
sterilant, a
disinfectant, and an antiviral agent.
The following examples are offered to illustrate embodiments of the
invention, and should not be viewed as limiting the scope of the invention.
Examples
Example 1- Efficacy Testing, of Solutions
I S Culture medium - Soil extract nutrient broth was prepared by adding
one pound of garden soil to IL distilled water. This mixture was filtered six
times
through Whatman #43 filter paper and then 8 grams of Nutrient broth (Difco)
and 5
grams NaCI was added. The medium was boiled for 20 minutes, diluted to 1 L,
and
adjusted pH to 6.9 with l N NaOH. This solution was filtered once more through
Whatman #43 filter paper before autoclaving for 20 min. at 121 °C and I
5 psi.
Preparation of Suture Loop Carrier - Standard loops were prepared by
wrapping size 3-0 surgical silk suture (black braided Al 84. USP. Ethicon,
Inc.) around
a pencil three times. This loop was then tied and knotted with another piece
of suture
before slipping off the end of the pencil. The ends of the' sutures were cut
to within
2mm, and prepared loops were then placed in 300 ml chloroform and incubated at
room
temperature for 24 hours while rotating at 100 rpm. The loops were then air-
dried at
room temperature under a hood. After drying, the suture loops were added to
100 ml
of O. SN HC 1 and incubated for 10 minutes. After 1 U minutes, loops were
washed three
times with distilled water ( 15 min. per wash) until the pH was neutral. Loops
were
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finally dried on filter paper at room temperature for 24 hours and then
sterilized by
autoclave (20 min. 121 °C, 15 psi).
Growth of Bacillus subtilis and Preparation of Suture Loos - A
purified colony offreshly growing Bacillus subtilis (ATCC # 19659) from
Nutrient agar
plates (Difco), was used to inoculate 500 ml soil extract nutrient broth.
Inoculated
medium was incubated with shaking (200 rpm) for 72 hours at 37°C. After
incubation
time, culture was poured into a tissue grinder, macerated, and filtered
through a sterile
funnel containing moist glass wool. Approximately 10 ml of culture was added
to
several sterile 50 cc centrifuge tubes (VWR) and then 10 sterile prepared
suture loops
were added to each 10 ml of bacterial culture. Suture loops were incubated for
15
minutes at room temperature and then removed with sterile forceps to a Petri
dish lined
with 2 layers of Whatman #43 filter paper. All suture loops contaminated with
B.
.suhtilis were placed in a vacuum oven at room temperature containing calcium
chloride
for 20 minutes, then dried under vacuum for an additional 24 hours. These
loops were
used within 24 hours of preparation.
Verification of Spore Viability-10 ml of2.5 N HCl was added to four
separate sterile glass vials and five contaminated suture loops were added to
each vial.
After 2, 5, 10, or 20 minutes, five suture loops were transferred to
thioglycolate
subculture broth for 20 seconds. Each suture loop was subsequently transferred
to 10
ml offresh sterile thioglycolate broth and incubated at 37°C.
Incubation was continued
for a total of 21 days.
Testing~of A-queous Sterilizing Aggnt - The following solutions,
referred to as PC-1, PC-2, and PC-3, were prepared and tested for their
ability to act as
an aqueous sporicidal agent.
The control hydrochloric acid solutions were prepared by diluting
commercial 1 ON hydrochloric acid solution with deionized water. The sterilant
solutions
PC-1, PC-2, and PC-3 were prepared as follows: ( 1 ) to prepare sterilant
solution PC-1,
solid citric acid was dissolved in deionized water at about 10% weight/volume,
to
produce a sterilant solution having a pH of 1.2; (2) to prepare sterilant
solution PC-2,
approximately 30% weight/volume solution ofcitric acid was first prepared by
dissolving
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solid citric acid in deionized wst~r, and then diasolviug solid sodium
hydrogen
phosphate is the said solution in small aliqtats tattil s pH of 1.2 was
achieved; and (3)
to prepare sterilattc solution PC-3, solid citric acid war dissolved in
daonized water at
30% level weiShtlvolurne, and then small aliquots of zinc oxide were dissolved
in the
acid solution until a pH of 1.2 was achieved.
Clean sterile vials oontainiag 5 ml of either control or the indicated
stcrilam PC solution wens incubated with Sve coatatxtinated suture loops at
28°C for
either six or sixty minutes. At the end of each incubation time, suture loops
were
removed with sterile forceps and placed in 5 mi thyoglycolate broth for 20
seconds.
Suture loops were sabseqtiently traaafernd to 10 ml fresh thyoglycolatc broth
and
incubated. Incubation was continued for a total of 21 days. At the end of the
21 days,
the tubes were heat-shacked for 20 minutes at 80°C and reiacubattd for
72 hourr at
37°C.
Table 1: Effectiveness of Liquid Sterilants (PC) and Control Hydrochloric Acid
Against Bacillus ar~bttlts Spores
Sample Type Iaeubation C3~Ow~ (pos./ae~.)
Time
(
~.SN He ~ (as Control) z s of s positive
2.SN HC t (a~ Control) S S of 5 positive
2.3N HC t (as Coturol) 10 3 oP S positive
2.SN HCI (as Conuol) 20 3 of 3 poaictve
pc.l, t09s claie geld s s of s e~aofve
(pH 1.2)
(Comparative Example) 60 5 of 3 neQatws
PC-2, 30~i tick acldINaHrPO,6 S of S ncatuive
(pH i .2)
60 5 of S negative
PC-3. 30'Nr citric rcid/Za06 5 of 5 ne~t(ve
(pH 1.2)
60 5 oI S ae~adve
Otbcr embodimcias and uses oFme invention wits oe apparcntto those
skilled in the art from consideration of the speci&cation and practice of the
invention
p~d;1 ~ pl-;,g~~: AMENDED SH EET
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disclosed herein. The speci$cation and examples should be considered exemplary
only
with the true scope and spirit of the invention indicated by the following
claims. All
references cited herein, including all U.S. and foreign patents and patent
applications,
including, but not limited to, U. S. Patent Application entitled "Multi-
Purpose Acid
S Compositions" filed contemporaneously herewith, are specifically and
entirely
incorporated herein by reference. As will be easily understood by those of
ordinary skill
in the art, variations and modifications of each of the disclosed embodiments
can be
easily made within the scope of this invention as defined by the following
claims.
