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Summary. The Elution of Iodine Out of a Hydrophilic Wound Dressing. Discussion.

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The Elution of Iodine Out of a Hydrophilic Wound Dressing


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 24-hour 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 time-release system.

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:

Proving an I2 Dressing will kill E. Coli Bacteria

Calculating the Effective Concentration of I2 in the Dressing

The elution concentrations were plotted as a function of time, to show the elution characteristics of I2 from the dressing.

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:

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 back in the incubator, and microscopic inspection proved that there still was no bacterial growth within the original area of inhibition after 80 hours of incubation.

Table 2

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:

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.

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.

Determining I2 Elution Rate From a Dressing Using UV/Vis Spectroscopy


  • Created calibration curve at 287 nm:

    • Created 5 dilutions of a 3.12×10-4 M solution of I2 in d-water.

    • 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.

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.


A hydrophilic wound dressing, embedded with 3.75 x 10-6 moles I2/gram dressingcan 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.

12 mLs of d-H2O in each:

Liquid drawn at time:

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:

Future Research


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.

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.

  • Designed an elution experiment:

    • Created a 31.5 g dressing with the previously discovered lethal dose of 1.5 grams of I2 per 31.5 grams of dressing.

    • Cut the dressing into seven 1g pieces, and placed each of these pieces into a separate glass bottle.

    • Using a calibrated pipetter, placed 12 mL of d-water into each bottle.

    • 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.

    • Compared each solution’s absorbance at 287 nm with the calibration curve, to obtain that sample’s I2 concentration.

  • There were two purposes of the research.

    • 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.

    • 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.

Figure 4: This is a visual description of the unique procedure used to determine the rate of I2 eluting out of a dressing.

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