Download Figure 2 - Greenwich Public Schools

Problem
Currently one of the most innovative wound dressings on the market,
Cardiotech’s dressing is known as a “smart dressing.” When this
dressing is placed on a wound that has liquid material on it already, the
dressing is able to absorb this possibly infectious material. At the same
time, the dressing, which is made of a Hydromed-G polymer, which can
hold up to three times its weight in water, is able to time release this
water onto the wound.
While the dressings do provide a sterile environment, if bacteria
are already present on a wound, the Cardiotech dressing is ineffective at
killing off the infection that is deep within the wound. Cardiotech will
not perform research on antibiotic medicated dressings because Food &
Drug Administration (FDA) regulations prohibit approval of them due
to fear that bacteria could ultimately become resistant to the antibiotic
agent. If an independent researcher can prove that these dressings are
effective in killing bacteria, and preventing further infection of a
wound, with little bacterial resistance, then these medicated dressings
could improve people’s health.
Purposes
There were two purposes of the research.
1. To demonstrate that a dressing, with I2 embedded within it, will
destroy weak bacteria such as E. coli, and ensure that this bacteria
cannot re-grow over a short period of time.
2. To demonstrate that an effective concentration of I2 will elute out
of the wound dressing, in order to kill neighboring bacteria, and
prevent further growth for a reasonable amount of time.
The Elution of Iodine Out
of a Hydrophilic Wound
Dressing
Proving an I2 Dressing will kill E. Coli
Bacteria
Figure 1: Successful I2
dressing with its evident area of
inhibition after 26 hours on E.
Coli culture.
Figure 2: Same culture
of E. Coli 80 hours
after removal of the I2
dressing.
The purpose of the procedure involving soaking 1 gram
dressings in d-water within a glass bottle was to simulate an
aqueous wound environment. Since testing with human test
subjects is not permitted, immersing a dressing within water
was the best way to determine the elution rate of iodine from
the dressing. It was also effective since the aliquots taken
from the elution experiment could easily be measured on the
UV-Vis spectrometer.
The Absorbance at 287 nm for each elution sample was
compared with the previous calibration curve to determine the
concentration of I2 in each elution trial. Table 2. illustrates the
Absorbance (at 287 nm) versus the calculated concentration
for each elution trial:
Concentrat
Calculating the Effective
Concentration of I2 in the Dressing
A dressing with 3.75×10-6 moles I2/g
dressing (determined from the new
formula of a dressing) ironed to be
0.5 cm thick and cut to have a radius
of 1.7 cm successfully killed the E.
coli when observed after 26 hours of
incubation. The entire area of
inhibition had a radius of 2 cm,
meaning the area extended 0.3 cm
beyond the dressing. The dressing
was then removed, the culture placed
b a c k i n t h e i n c ub a t o r, a n d
microscopic inspection proved that
there still was no bacterial growth
within the original area of inhibition
a ft e r 8 0 hour s o f i nc uba t i on .
To determine the effective molarity of I2 within the dressing, moles I2/gram dressing
was determined for each 1 gram of polymer, keeping in mind that iodine tincture is
2% I2:
Created calibration curve at 287 nm:
1. Created 5 dilutions of a 3.12×10-4 M solution of I2 in dwater.
2. Obtained the UV-Vis spectrum and created a Beer’s Law
plot of A287 versus concentration (Molarity of I2) for the
entire series of dilutions.
Using the Effective Concentration in
an Elution Experiment
Since the I2 within the 1 gram dressing would elute out into 12 mLs of d-water, a
dressing with an effective amount of I2 (3.75 x 10-6 moles I2/gram dressing) was
used. The maximum molarity of I2 within the elution bottle, assuming all has eluted
from the 1 gram dressing, is:
Concentration
of I2 M
A287
3.12E-04
1.192
2.57E-04
1.0190
1.26E-04
0.4413
1
1.10E-04
0.3825
0.8
7.85E-05
0.2351
0.6
6.28E-05
0.1486
Concentration of Iodine vs. Absorbance
at 278 nm
1.4
y = 4214.2x - 0.0949
1.2
2
R = 0.9974
0.4
0.2
0
0.00E+00
1.00E-04
2.00E-04
3.00E-04
Conc (M) of Iodine
4.00E-04
1 gram of
dressing
1 gram of
dressing
1 gram of
dressing
1 gram of
dressing
30 min
ion of I2
(M)
10 min
0.021
3.24E-05
30 min
0.036
3.44E-05
1 hour
0.060
3.98E-05
2 hours
0.057
3.91E-05
6 hours
0.132
5.61E-05
12 hours
0.374
1.11E-04
24 hours
1.326
3.26E-04
Table 2
1 hour
2 hr
6 hr
12 hr
Liquid drawn at
time:
24 hr
1.50
1.4
y = 3E-05e
3.00E-04
0.0959x
2
R = 0.9963
2.50E-04
2.00E-04
1.50E-04
1.00E-04
5.00E-05
0.00E+00
0
10
20
30
Time (Hours)
A hydrophilic wound dressing, embedded with 3.75 x 10-6 moles
I2/gram dressing can successfully kill E. coli bacteria within 26 hours.
It has been shown that E. coli did not re-grow within the area of
inhibition even within an 80 hour period. This effective dosage of I2
can be embedded into a wound dressing and elute out within 24 hours.
These results are important to the field of wound care because they
provide the basis for the creation of time release medicated dressings
that can affectively create a sterile environment for a wound while
simultaneously administering medicine that will inhibit bacterial
growth and infection. This research indicates that these dressings can
provide continual medication of a wound through a topical vessel, for a
period of at least 24 hours.
Table 1. Abs287 and
Concentration (M) of
Elution Trials.
Figure 3: Since the maximum concentration of Iodine that
would be found in the elution experiment was 3.12 x 10-4 M, a
Beer’s Law plot of A287 nm versus Concentration of I2 was
created with the highest point at this concentration. Six dilutions
were made, and the UV-Vis spectrum of each dilution was
collected. The Absorbance at 287 nm for each dilution, or
standard, was plotted against the concentration of I2 (M) to
create a Beer’s Law calibration curve:
3.50E-04
Conclusions
1 gram of
dressing
1 gram of
dressing
12 mLs of d-H2O in
each:
10 min
A287
nm
Figure 5: This graph shows the results of the elution experiment. It
is clear that after 24 hours, the entire maximum concentration of I2
(3.12×10-4 M) had eluted out of the dressing. The actual calculated
concentration at 24 hours was 3.26×10-4 M, but this difference is
well within the instrumental error of the UV spectrometer.
Dressing Elution Experiments
1 gram of
dressing
The elution concentrations were
plotted as a function of time, to
show the elution characteristics
of I2 from the dressing.
Elution
Time
Iodine Concentration vs. Time
Determining I2 Elution Rate From a Dressing Using UV/Vis Spectroscopy
Abs (278 nm)
A revolutionary type of hydrophilic wound dressing has been
developed that can hold unusually high amounts of liquid, and allow
for the time release of these liquids onto a covered wound. These
dressings have been found to be very useful in maintaining a sterile
environment above a variety of different wounds, most specifically
burns or bedsores. In a non-sterile environment, these dressings will
do nothing to curb or prevent the spread of bacterial infection.
Research on the time release of anti-bacterial medication from these
dressings has been limited. The purpose of this project is to
successfully infuse I2 into a wound dressing, and demonstrate that this
dressing will time release adequate medication to kill and prevent the
re-growth of E. Coli.
To create the dressings, Hydromed-G
polyurethane, propylene glycol, distilled water, and iodine tincture
were mixed together, heated, and then ironed so that the substance was
more malleable. It was then placed upon a culture of E. Coli, and later
determined that a concentration of 3.75×10-6 moles I2/g dressing would
successfully kill E. Coli with a 20 mm radius of the area of inhibition
(extending 3 mm beyond the dressing) after 26 hours. A similar
concentration of I2 was embedded into a wound dressing, and the rate
of elution from the wound dressing was determined. One gram pieces
of I2-loaded dressings were placed in d-water, and the UV-Vis spectra
of aliquots at 10 minutes, 30 minutes, 1 hour, 2 hours, 6 hours, 12
hours, and 24 hours were collected. The absorbance at 278 nm for
each of these aliquot’s spectrum was compared to a Beer’s Law plot of
Absorbance278 nm versus concentration (up to 0.0003 M) of I2 in
solution. Analysis of the elution solutions indicates that the optimal
concentration of I2 for inhibiting bacterial growth elutes out over a 24hour period. It can be concluded that time-release antimicrobial wound
dressings provide a sterile environment, and successfully kill off
bacteria with no re-growth after an 80 hour period. It has been
demonstrated that these dressings can release a sufficient amount of
medicine within 24 hours, effectively killing off bacteria in a timerelease system.
Discussion
Concentration (M)
Summary
1.3260
Iodine Dressing Elution Study
1.3
Future Research
1.2
1.1
1.0
0.9
Designed an elution experiment:
1. Created a 31.5 g dressing with the previously discovered
lethal dose of 1.5 grams of I2 per 31.5 grams of dressing.
2. Cut the dressing into seven 1g pieces, and placed each of
these pieces into a separate glass bottle.
3. Using a calibrated pipetter, placed 12 mL of d-water
into each bottle.
4. Collected an elution sample at 10 minutes, 30 minutes, 1
hour, 2 hours, 6 hours, 12 hours, and 24 hours, and
subsequently obtained the UV-Vis spectrum of each.
5. Compared each solution’s absorbance at 287 nm with
the calibration curve, to obtain that sample’s I2
concentration.
Additional research using alternative medications can be conducted
to demonstrate how well these other medicines elute out to kill and
inhibit future growth of bacteria within a reasonable time.
0.8
A
0.7
0.6
0.5
0.37374
0.4
0.13200
0.3
Figure 4: This is a visual
description of the unique
procedure used to
determine the rate of I2
eluting out of a dressing.
0.2
0.060320
0.1
0.00
250.0
300
350
400
450
500
550
600
nm
IODTIME1.SP IODTIME2.SP IODTIME3.SP IODTIME4.SP IODTIME5.SP IODTIME6.SP IODTIME7.SP -
2/8/2007
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2/8/2007
2/8/2007
2/8/2007
2/8/2007
2/9/2007
- iodine after 10 minutes
- iodine after 30 minutes
- iodine after 1 hour
- iodine after 2 hour
- iodine after 6 hours
- iodine after 12 hours
- iodine after 24 hours
650
700
750
800
850
900.0
There are many applications that show beneficent potential. These
dressings can be applied to Poison Ivy or fungal disease, hopefully
showing that a gradual application and time release of medicine in a
sterile environment onto this sort of wound will aid in the healing
process.