Hydrogel structure

Abstract

A hydrogel structure which has: (a) a one way penetrating polyurethane film layer; (b) a hydrophobic pressure sensitive adhesive layer; (c) a multi-directional elastic meltblown nonwoven; (d) an interpenetrating polymer network; and (e) a hydrogel; wherein the meltblown nonwoven and the hydrogel are laminated by UV curing to form the interpenetrating polymer network, part of fibers of the meltblown nonwoven are exposed and fit stably with the pressure sensitive adhesive film. The hydrogel structure can make dressings multi-directional elastic for multiple traumas. The hydrogel structure can provide an environment suitable for wound healing, shorten the healing time, antiseptic and reduce the chances of being infected for the wound dressing.

Claims

1. A hydrogel structure comprising: (a) a one way penetrating polyurethane film layer; (b) a hydrophobic pressure sensitive adhesive layer; (c) a multi-directional elastic meltblown nonwoven layer; (d) an interpenetrating polymer network; and (e) a hydrogel layer; wherein four layers, (a), (b), (c) and (e), are arranged in a sequential order, and the interpenetrating polymer network is formed by interpenetrating part of the meltblown nonwoven layer into the hydrogel layer and part of the hydrogel layer into the meltblown nonwoven layer by UV curing, thereby the remaining meltblown nonwoven layer being laminated with the pressure sensitive adhesive layer such that the (b), (c) and (e) layers being bound together by the interpenetrating polymer network.

2. The hydrogel structure of claim 1, wherein the hydrogel comprising: (a) a monomer; (b) a plasticizer; (c) a photoinitiator; (d) a cross-linking agent; and (e) a thickener.

3. The hydrogel structure of claim 2, wherein the thickener is glycerol.

4. The hydrogel structure of claim 2, wherein the photoinitiator generates free radical and completes polymerization under 1 to 50 seconds of UV light irradiating.

5. The hydrogel structure of claim 2, wherein the cross-linking agents are esters with unsaturated double functional groups.

6. The hydrogel structure of claim 2, wherein the ratio by weight of the acrylic amide monomer, the acrylic sulfonate monomer, the glycerol, the photoinitiator, and a monomer of the esters with unsaturated double functional groups is from 15:10:15:0.01:0.01 to 30:50:45:0.1:0.2.

7. The hydrogel structure of claim 2, wherein the monomer is acrylic amide monomer or acrylic sulfonate monomer.

8. The hydrogel structure of claim 7, wherein the acrylic sulfonate monomer provides the hydrogel antiseptic effect.

9. The hydrogel structure of claim 2, wherein the plasticizer is glycerol.

10. The hydrogel structure of claim 9, wherein the glycerol provides the hydrogel flexibility and increases the hydrophilicity.

11. The hydrogel structure of claim 1, wherein the hydrogel have an elongation rate from 200% to 1000%.

12. The hydrogel structure of claim 11, wherein the hydrogel have an elongation rate from 881% to 960%.

13. The hydrogel structure of claim 1, wherein the interpenetrating polymer network strengthens tension and adhesive ability for wound covering.

14. The hydrogel structure of claim 1, wherein the hydrogel absorb excess moisture or wound tissue fluid to maintain proper skin moisture.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the schematic diagram of the hydrogel structure. 10 is the Polyurethane film layer 20 is the pressure sensitive adhesive layer 30 is the meltblown nonwoven 40 is the hydrogel 50 is the interpenetrating polymer network

(2) FIG. 2 is the swelling ratio of the hydrogel (%).

(3) FIG. 3 is the wound area calculated by the software Image Pro Plus 4.5 (Area 2, value 355.096).

(4) FIG. 4 is the appearance of the wound on different timing after the dressings are applied.

(5) FIG. 5 is the percentage of the remaining wound area (%) after applying the dressings 14 days.

(6) FIG. 6 is the representative figures of epidermal growth after applying the dressings 14 days. A represents the control group. B represents LexiDerm Hydrogel Dressing.

(7) FIG. 7 is the representative figures of granulation growth and Inflammation after applying the dressings 14 days. A represents the control group. B represents LexiDerm Hydrogel Dressing.

(8) FIG. 8 is the representative figures of epidermal growth after applying the dressings 31 days. A represents the control group. B represents LexiDerm Hydrogel Dressing.

(9) FIG. 9 is the representative figures of granulation growth and Inflammation after applying the dressings 31 days. A represents the control group. B represents LexiDerm Hydrogel Dressing.

SUMMARY OF THE INVENTION

(10) The present invention relates to a hydrogel structure comprising: (a) a one way penetrating polyurethane film layer; (b) a hydrophobic pressure sensitive adhesive layer; (c) a multi-directional elastic meltblown nonwoven; (d) an interpenetrating polymer network; and (e) a hydrogel; wherein the meltblown nonwoven and the hydrogel are laminated by UV curing to form the interpenetrating polymer network, part of fibers of the meltblown nonwoven are exposed and fit stably with the pressure sensitive adhesive film.

DETAIL DESCRIPTION OF THE INVENTION

(11) The present invention provides a hydrogel structure for multiple traumas. The structure has better swollen properties; the surface stickiness changes based on the status of moisture aborting and can create the best healing environment. The hydrogel structure makes the wound dressing to keep a suitable environment for wound healing, shorten the healing time, antiseptic and reduce the chances of being infected.

(12) Hence, The present invention provides a hydrogel structure comprising: (a) a one way penetrating polyurethane film layer; (b) a hydrophobic pressure sensitive adhesive layer; (c) a multi-directional elastic meltblown nonwoven; (d) an interpenetrating polymer network; and (e) a hydrogel; wherein the meltblown nonwoven and the hydrogel are laminated by UV curing to form the interpenetrating polymer network, part of fibers of the meltblown nonwoven are exposed and fit stably with the pressure sensitive adhesive film.

(13) In one embodiment, the interpenetrating polymer network strengthens tension and adhesive ability for wound covering.

(14) In another embodiment, the hydrogel absorb excess moisture or wound tissue fluid to maintain proper skin moisture.

(15) In still another embodiment, the hydrogel have an elongation rate from 200% to 1000%.

(16) In still another embodiment, the hydrogel have an elongation rate from 881% to 960%.

(17) In still another embodiment, the hydrogel comprises: (a) a monomer; (b) a plasticizer; (c) a photoinitiator; (d) a cross-linking agent; and (e) a thickener.

(18) In still another embodiment, the monomer is acrylic amide monomer or acrylic sulfonate monomer.

(19) In still another embodiment, the acrylic sulfonate monomer provides the hydrogel antiseptic effect.

(20) In still another embodiment, the plasticizer is glycerol.

(21) In still another embodiment, the thickener is glycerol.

(22) In still another embodiment, the glycerol provides the hydrogel flexibility and increases the hydrophilicity.

(23) In still another embodiment, the photoinitiator generates free radical and completes polymerization under 1 to 50 seconds of UV light irradiating.

(24) In still another embodiment, the cross-linking agents are esters with unsaturated double functional groups.

(25) In still another embodiment, the weight ratios of the hydrogel are: 15 to 30 units of acrylic amide monomer; 10 to 50 units of acrylic sulfonate monomer; 15 to 45 units of glycerol; 0.01 to 0.1 units of photoinitiator; and 0.01 to 0.2 units of unsaturated double functional groups ester monomer.

(26) The meltblown nonwoven and the hydrogel of the present invention are irradiated by UV light, making them stuck together and formed an interpenetrating polymer network. The meltblown nonwoven fibers of the interpenetrating polymer network are hydrophobic and parts of them are exposed that can fit stably with the pressure sensitive adhesive layer and give the hydrogel multi-directional elasticity to adapt different skin parts.

(27) The interpenetrating polymer network includes part of the elastic meltblown non-woven, therefore strengthens tension. In this case, while the polyurethane film achieves multi-directional elasticity for proper wound covering, the hydrogel remain unbroken because of the better tension.

(28) The interpenetrating polymer network also strengthens adhesive ability. The hydrogel itself is easy to detach when absorbing liquid. However, since the interpenetrating polymer network includes part of the meltblown non-woven, better adhesion to skin is provided. As such, it avoids easy detachment which causes secondary damage.

(29) The UV curing step could also be achieved by other oxygen related procedure.

(30) The hydrogel of the present invention contacts with the trauma as the fitting surface of the wound, making the wound in the appropriate moist condition for accelerating healing. The moist healing environment is conducive to wound healing, if the wound dehydrates, the cells cannot survive. Although a variety of moist gauze or bandage can also provide a moist healing environment, the gauze or bandage type of dressings are required frequently change, making newly formed cells damaged easily, causing the wound second damage, and there is the risk of dehydration. The hydrogel of the present invention has the water-absorbing and sticky reducing features, and causes less damage compared to normal moist gauze or bandage such as Vaseline gauze in changing the dressings. Its water absorption ratio gives it the best moist condition that meets the requirements for wound healing. It absorbs excess moisture, keeping skin in proper humidity, and has more loading capacity for medicine.

(31) The polyurethane film layer of the present invention is a tension, waterproof, breathable one way penetrating membrane; it provides thermoplastic deformable elasticity and tensioning that meets various needs of the wound cover. Meanwhile, the polyurethane film layer provides waterproof, bacteria resistance, breathable and cooling effects for the wound. The pressure sensitive adhesive layer of the present invention is a hydrophobic material coated on the polyurethane film layer, making it fit with the skin.

(32) The present invention can be applied on all kinds of wound dressings, dressings for ring circumcision surgery, and electrode dressings.

(33) The beneficial effects of the present invention are that the hydrogel structure can make trauma dressings multi-directional elastic to meet the use for many wounds, providing a better environment for wound healing, shorten the healing time, antiseptic and reduce the chances of being infected.

(34) The following combined figures and specific implementing modalities that give the present invention further elaborations.

EXAMPLES

(35) The examples below are non-limiting and are merely representative of various aspects and features of the present invention.

Example 1

The Hydrogel Structure

(36) As shown in FIG. 1, the hydrogel structure had superimposed layers of the polyurethane film layer (10), the pressure sensitive adhesive layer (20), the meltblown nonwoven (30) and the hydrogel (40) that formed a interpenetrating polymer network (50), wherein the pressure sensitive adhesive layer (20) was coated on the polyurethane film layer (10), the meltblown nonwoven (30) and the hydrogel (40) were laminated by UV curing to make an interpenetrating polymer network (50), and part of the meltblown nonwoven fibers (30) were exposed and fit stably with the pressure sensitive adhesive layer (20) to form the hydrogel structure.

Example 2

The Hydrogel Formulation

(37) The hydrogel was made by the steps as follows:

(38) (a) providing a mixture comprising: (I) mixing the photoinitiator and the acrylic amide monomer to dissolve; (II) adding glycerol and mix to dissolve; (III) adding acrylic sulfonate monomer and mix to dissolve; (IV) adding glycerol and mix up.

(39) (b) further providing a mixture comprising: (I) mixing the photoinitiator and the unsaturated double functional groups ester monomer.

(40) (c) mixing up the mixture of step (a) and step (b).

(41) (d) crosslinked polymerizing the mixture of step (c) by UV light irradiating to form the hydrogel.

(42) The weight ratios of the above were

(43) TABLE-US-00001 Acrylic amide monomer 15 to 30 units Acrylic sulfonate monomer 10 to 50 units Glycerol 15 to 45 units Photoinitiator 0.01 to 0.1 units Unsaturated double functional 0.01 to 0.2 units groups ester monomer

Example 3

Tensile Test

(44) For the hydrogel structure (LexiDerm) of the present invention, the polyurethane film layer and the hydrogel composites were examined based on ASTM D 412-98a Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers-Tension, the results were as Table 1:

(45) TABLE-US-00002 TABLE 1 Tensile strength and elongation test (Examining Unit: TTRI) Maximum Fracture Tensile Sample/ strength strength 100% Modules 300% Modules strength Elongation Number Max (g) (g) (g/mm.sup.2) (g/mm.sup.2) (g/mm.sup.2) % Polyurethane 505.00 501.00 21.55 12.00 126.25 912.60 film layer/1 Polyurethane 1004.00 1004.00 25.56 13.43 251.00 1016.70 film layer/2 Polyurethane 1130.00 1130.00 24.34 11.98 282.50 1213.30 film layer/3 Polyurethane 661.00 647.00 26.26 12.85 165.25 950.05 film layer/4 Polyurethane 974.00 974.00 25.06 12.57 243.50 1111.70 film layer/5 Polyurethane 830.00 830.00 19.63 11.48 207.50 1113.10 film layer/6 Hydrogel 354.00 321.00 43.27 19.69 141.60 925.63 composites/1 Hydrogel 304.00 256.00 33.15 17.68 121.60 886.30 composites/2 Hydrogel 289.00 263.00 26.56 13.75 115.60 935.05 composites/3 Hydrogel 304.00 258.00 29.08 16.03 121.60 881.20 composites/4 Hydrogel 287.00 221.00 29.59 17.43 114.80 907.02 composites/5 Hydrogel 413.00 306.00 37.56 21.75 165.20 959.95 composites/6

Example 4

Breathability Test

(46) For the hydrogel structure (LexiDerm) of the present invention, the polyurethane film layer and the hydrogel composites were examined based on JIS L 1096, the results were as Table 2:

(47) TABLE-US-00003 TABLE 2 Breathability test (Examining Unit:TTRI) Polyurethane Hydrogel film layer composites Number (cm.sup.3/cm.sup.2/sec) (cm.sup.3/cm.sup.2/sec) 1 0.0035 0.0520 2 0.0028 0.0759 3 0.0035 0.0590 4 0.0030 0.0695 5 0.0028 0.0605 6 0.0025 0.0510

Example 5

Moisture Permeability Test

(48) For the hydrogel structure (LexiDerm) of the present invention, the moisture permeability were examined based on JIS L 1099 A1 Calcium Chloride upright Cup test, the results were as Table 3:
Permeability (g/m.sup.2 day)=(Second−First)*8488

(49) TABLE-US-00004 TABLE 3 Permeability test (Examining Unit:TTRI) First Second Sample/ weight weight Result Number (g) (g) (g/m.sup.2 day) Hydrogel 230.138 230.893 6408.44 composites/1 Hydrogel 230.914 231.58 5653.008 composites/2 Hydrogel 230.718 231.388 5686.96 composites/3 Hydrogel 238.172 239.04 7367.584 composites/4 Hydrogel 230.423 231.124 5950.088 composites/5 Polyurethane 227.869 227.963 797.872 film layer/1 Polyurethane 234.092 234.198 899.728 film layer/2 Polyurethane 226.27 226.373 874.264 film layer/3 Polyurethane 224.309 224.417 916.704 film layer/4 Polyurethane 228.073 228.179 899.728 film layer/5

Example 6

Absorption Rate

(50) For the hydrogel structure (LexiDerm) of the present invention, the absorption rate were examined. The hydrogel were weighted and put it into 25° C., pH=7.4 PBS, after fully swelled, the surface water was wiped out and the hydrogel were weighted. The hydrogel were removed every time interval and were weighted till the weight of the hydrogel stopped changing. The absorption rate was measured by the change of the hydrogel weight, the swelling rate %=[(weight of the wet hydrogel−weight of the original hydrogel)/weight of the original hydrogel]×100%, the results are as FIG. 2.

Example 7

Wound Healing Test

(51) Materials and Methods

(52) (1) Test Objects

(53) Gauze Control Group

(54) The hydrogel structure of present invention experimental group (LexiDerm)

(55) (2) Experimental Animals

(56) Three animal strains of LYD 2 months old pigs that have passed the examination of experimental animal and Management Group of Taichung veterans general hospital (Number: La99736).

(57) (3) Test Group

(58) Animals were divided into two groups, Day 14 (three pigs) and Day 31 (one pig). Every animal had three 3 cm×3 cm all skin excision wounds on left and right side of the back respectively, then giving the control or experimental dressings respectively.

(59) (4) Applying Methods

(60) Applied the experimental or control substances directly on the wound on animals' back, and changed the substances every 3-5 days.

(61) (5) In Vivo Animal Experiments

(62) Experiments carried out on 2 months old LYD three strains of pigs as experimental animals. Experimental equipments included shaving knife, autoclaved with high temperature and pressure surgical instruments (ratio scale, hole towel forceps, scissors, tweezers, clamps, scalpel and needle holder) and consumables (sterile hole towel, gauze, cotton, tincture of iodine, alcohol and sutures), the procedures were as follows:

(63) Each pig was giving leading anesthesia by ketamine (20 mg/kg) and xylazine (2 mg/kg), then by 1.0-2.0% isoflurane to maintain anesthesia. After shaving the back, sterilize with 70% Alcohol first, then with Betadine and covered with sterilized hole towels. Six 3 cm×3 cm all skin excision wounds with the depth to panniculus carnosis were created by scalpel. Covered the wounds with experimental or control dressings then with a layer of gauze and wrapped the wounds with elastic bandages or sutures to prevent infection caused by the broken of the dressings. Cleaned the wounds every 3-5 days after the surgery, changed new experimental or control dressings and then re-bandaged and fixed by the above methods. Postoperative care: In first 1-2 days, conducted postoperative analgesia by carprofen 2 mg/kg to relieve pain.

(64) As mentioned above, the pigs should be fed separately, free to water and feed regularly after the operation. The experiments were recorded by day and evaluated the pigs as follows on Day 3, 7, 10, 12 after the operation. Clinical wound assessment—observed the skin and wound healing process. Record the dressing binding situation on the pigs separately, the amount of secretion, the situation of the wound surrounding tissue, the growth situation of the wound and the changing difficulty of the dressings. In addition to text recording, took pictures for comparison and finally arranged and analyzed the results. Wound healing promoting assessment—put a ratio scale and took pictures of the wounds on each dressing changing point. Calculated the wound area after the correction of graphics software Image Pro Plus 4.5 by the ratio scale, as shown in FIG. 3, in which Area 2 was the entire wound area, the calculated value was 355.095; Area 4 was part of the wound area still in healing, the calculated value was 61.4683, and Area 3 was the partially healed wound area, the calculated value was 355.096 (Area 2)−61.4683 (Area 4)=273.628).

(65) Histological assessment—took out the normal tissue together with the implanted samples and underwent histopathological biopsy (if required). 14 days after the surgery, took 5 mm wedge biopsies, need to include the dressing, granulation tissue, connective tissue and the muscle below. Fix tissues in formaldehyde first, then underwent dehydrate, embedding, de-wax, slice and stained with H & E and picro-Sirius red. Observe the interaction of epithelial cells, dermal cells, neovascularblasts, inflammatory cells and fibroblasts to assess wound healing.

(66) Scoring Standard:

(67) Epidermis growing score: 0—No growth, 1—The growth of epidermis is smaller than ⅓ of the wound, 2—The growth of epidermis is between ⅓ and ½ of the wound, 3—The growth of epidermis is between ½ and ⅔ of the wound, 4—The growth of epidermis is more than ⅔ of the wound or completely healed.

(68) Granulation score: 0—No growth of granulation tissue, 1—Loose growth of granulation tissue, 2—Dense growth of granulation tissue, 3—Connective tissue formed. Inflammation score: 0—Severe inflammatory response (large infiltration of neutrophils and lymphocytes), 1—Moderate inflammatory response (multi infiltration of lymphocytes), 2—Mild inflammatory response (small infiltration of lymphocytes), 3—No inflammatory response (no infiltration of lymphocytes).

(69) Results:

(70) (1) Postoperative Clinical Symptoms and Wound Observation Assessment

(71) The first 1 to 2 days after pigs were conducted whole skin excision, giving them Capricorn 2 mg/kg for postoperative pain relieving by the principles of human experiments. During the experiment, pigs didn't show biting the wound portion and no dressing falling or frayed. On the dressing changing day, 3 and 6 days after the surgery, the dressings could not fully absorb the wound exudates and there were large amounts of exudates flowing out around the wounds in experimental and gauze control groups. The amounts of exudates were significantly reduced on the dressing changing day, 9 days after the surgery. In the adhesion condition between dressings and wounds, the gauzes adhered to the wound tissues easily and needed to rinse with saline solution to take them out during the experiment in the control group, but the dressings of the experimental group didn't have this situation.

(72) (2) Postoperative Wound Healing Visual Assessment

(73) The sizes of the wounds after conducted whole skin excision in pigs were between 28.72 to 32.52 mm.sup.2 6 days after dressings were applied; there was a little new skin tissue formed on the edge of the wound in the experimental group (FIG. 4, day 6). 12 days later, the wounds in each group were significantly reduced and the wound shapes were square and smooth. The newly formed skin tissue covered more than ½ of the wound in the experimental group on day 20. 28 days after dressings were applied; almost all the wounds had healed. The healing of the wounds in the gauze control group was mainly the distortion of the wound and few skin tissues were formed. However, in the experimental group, there were more new skin tissues formed, but the newly formed skin tissues of the wound were smooth (FIG. 4, day 28).

(74) (3) Postoperative Wound Promoting Healing Assessment

(75) After quantitative analysis of wound area, we could see the wounds were significantly reduced in the experimental group compared to gauze control group on day 6 of dressing applied (FIG. 5 and Table 4).

(76) TABLE-US-00005 TABLE 4 Group 0 day 3 day 6 day 9 day 12 day 14 day Control   100 ± 0.0 94.0 ± 13.5 81.0 ± 9.6  45.4 ± 9.7 25.0 ± 6.3 17.2 ± 6.9 LexiDerm 100.0 ± 0.0 100.1 ± 9.9  69.4 ± 11.2 26.6 ± 5.3 15.0 ± 4.6 11.0 ± 4.8 hydrogel The percentage of the remaining wound area to the original area after applying the dressings 14 days (%). *: P < 0.05, **: P < 0.01, ***: P < 0.001 Compared to the control group. Control (n = 3), LexiDerm hydrogel (n = 9).
(4) Histological Assessment of the Wound 14 Days after Applying Dressings

(77) Epidermis growing score: In the gauze control group, the growth of epidermis was near ⅓ of the wound and the score was 1. In other experimental groups, the growth of epidermis was between ⅓ and ½ of the wound, and the score was 2. The growth of epidermis in the experimental group was better than in the gauze control group (FIG. 6). Granulation score: The growth of granulation tissue in gauze control and experimental group was very dense and both the scores were 2 (FIG. 7). Inflammation score: The infiltration of lymphocytes in the gauze control group wasn't significant, and the wounds of the experimental group had small to medium lymphocyte infiltration. The endogenous in the experimental group was significant to the gauze control group (FIG. 7).

Example 8

Bacterial Preventing and Antiseptic Test

(78) For the hydrogel structure (LexiDerm) of the present invention, the bacterial preventing and antiseptic effects were examined based on JIS L1902:2008, the results were as Table 5 (strain: Staphylococcus) and Table 6 (strain: Klebsiella pneumoniae):

(79) TABLE-US-00006 TABLE 5 Result Test Article Control LexiDerm Staphylococcus Bacterial 1.8 × 10.sup.5 1.8 × 10.sup.5 ATCC 6538P planting concentration Ma .sup.1 3.9 × 10.sup.4 — Mb .sup.2 1.4 × 10.sup.7 — Mo .sup.3 — 2.8 × 10.sup.4 Mc .sup.4 — <20 Proliferation 2.6 — value .sup.5 Antiseptic — 5.7 activity value .sup.6 Bactericidal — 3.3 activity value .sup.7 * The test base on JIS L1902:2008 .sup.1 Ma = The amount of bacteria immediately after washing in the control group .sup.2 MB = The amount of bacteria 18 hours after culture in the control group .sup.3 Mo = The amount of bacteria immediately after washing in the experimental group .sup.4 Mc = The amount of bacteria 18 hours after culture in experimental group .sup.5 Proliferation value = logMb − logMa .sup.6 Antiseptic activity value = (logMb − logMa) − (logMc − logMo) .sup.7 Bactericidal activity value = logMa − logMc Source: TTRI Report 2010/07

(80) TABLE-US-00007 TABLE 6 Result Test Article Control LexiDerm Klebsiella Bacterial 1.6 × 10.sup.5 1.6 × 10.sup.5 pneumoniae planting ATCC 6538P concentration Ma .sup.1 2.8 × 10.sup.4 — Mb .sup.2 2.0 × 10.sup.7 — Mo .sup.3 — 2.9 × 10.sup.4 Mc .sup.4 — <20 Proliferation 2.9 — value .sup.5 Antiseptic — 6.0 activity value .sup.6 Bactericidal — 3.2 activity value .sup.7 * The test base on JIS L1902:2008 .sup.1 Ma = The amount of bacteria immediately after washing in the control group .sup.2 MB = The amount of bacteria 18 hours after culture in the control group .sup.3 Mo = The amount of bacteria immediately after washing in the experimental group .sup.4 Mc = The amount of bacteria 18 hours after culture in experimental group .sup.5 Proliferation value = logMb − logMa .sup.6 Antiseptic activity value = (logMb − logMa) − (logMc − logMo) .sup.7 Bactericidal activity value = logMa − logMc Source: TTRI Report 2010/07