Water vapor transmission rate (WVTR)

According to PEPPAS at al., 1987, the most problem in take care of the burned victim was the fact that the victim may lost of their body liquid due to evaporation and exudation.

These will affect the decrease of body temperature and accelerating the metabolism. Therefore the hydrogel wound dressing must avoids or at least reduces the body liquid lost i.e. by controlling absorption and transmission as well as to be able to kept the high humidity in wound area, in order to accelerate the formation of granule and epitelesation process. Based on Table I, it can be seen that the WVTR values of PVA-PVP blended hydrogel are around

80 to 200 gr/m²/h. These values seem to be an ideal range for wound dressing. The higher value of WVTR causes the faster the drying of wound. Although there are not an exact ideal value of WVTR for wound dressing, but in fact the value must not so high because it will make a dry condition in wound area. On the other hand, if the WVTR value is so low, then it will make the accumulation of exudates which may cause the deceleration of healing process and opening the risk of bacterial growth. For comparison, Table III shows WVTR for some commercial wound dressing values (Bruin, P., et al., 1990). According to Bruin, P. et al., 1990, an occlusive wound covering, such as Op Site (see Table 3) with a WVTR of 33 gr/m²/hr, has a weakness point, i.e. causes an accumulation of exudates under the covering and in turn causes infection.

FIG. 3. Relationship between water absorption (%) and immersion time (hr) at different irradiation dose.

TABLE III. THE VALUE OF WVTR OF SOME COMMERCIALIZED WOUND DRESSING Wound dressing types WVTR (g/m²/hr)

Biabrone 154

Metalline 53

Op Site 33

Omiderm 208

Human skin (we) 15

Pig skin (we) 9

3.5. Microbe penetration test

Based on the microbe penetration test, there was no bacteria passing through the hydrogel during day-by-day observation for 14 days. Without bacteria found on the TSA medium, the PVA-PVP blended hydrogel could be considered as a good barrier against microbes. This characteristic is very important for hydrogel dressing, especially in protecting the wound from further infection so that it may accelerate the healing of wound.

3.6.In vitro assessment

The macroscopic observations of the wound healing effect in term of comfortability and the excudate absorption performance of the hydrogel sample as compared to Sofratulle and Sterilized Gauze were done. It was found that the PVA-PVP blended hydrogel and Sofratulle have a better comfortability than that of the sterilized gauze when dressing are removed from the wound. The hydrogel adhered slightly to the wound and caused only a little hemorphagic.

The capability of the PVA-PVP blended hydrogel in absorbing wound exudates was observed as high as the Sterilized Gauze, while Sofratulle nearly did not absorbed any exudates.

Furthermore the PVA-PVP blended hydrogel was better in preventing the wound from contamination compared with the sterilized gauze and sofratulle. This is possible because it has a good comfortability that enables to cover the wound perfectly. It can be seen in Fig. 4, that the healing process which are reflected by the reduction of the wound surface area seems to be proceeded quite fast up to 10 days, then it will be slowly until the wound was fully recovered at the day of 18. There were no significant differences on the time of complete recovering of the wound. However, the surface of the recovered wound treated with PVA-PVP blended hydrogel or sofratulle was observed to be smoother than that of treated with sterilized gauze.

FIG. 4. Relationship between the mean surface area of the wound.

Histological study was done by microscopical observation of the wound healing process.

Microscopical observation of the formation of the new tissue at day 3, 7, 14 and 18 revealed that at Day 3, the wound shows no hair follicle and no sebaceous gland under the wound surface (see Fig. 5). The wound surface was covered by exudates layer which was consisted of the mixture of the fibrin, tissue debris and polymorpho nuclear cell (PMN). The tissue bond underwent oidema (macrophage) and blood vessel look hyperemis. Besides that, the initial granulation started to be formed. There were no bacteria of fungi colonies found. At day 7, all wounds either tested with PVA/PVP blended hydrogel, sofratulle or sterilized gauze showed a significant inflammatory reaction.

FIG. 5. Histology of wound after 3 days of treatment with PVA-PVP blended hydrogel: (a) the wound covered by fibrin, debris and PMN excudate, (b) hair follicles undergo degeneration and integration.

Magnification: 40 X.

FIG. 6. Histology of wound after 14 days of treatment with PVA-PVP blended hydrogel. Epidermis layer undergoes proliferation: (a) and information of dermis tissue bond which is consisted of PMN, eosinofil and macrophage (b) Magnification: 40 X..

At Day 14, although the wound healing was almost completely achieved and granulation tissue has been formed, the wound surfaces were still covered by PMA exudates (see Fig. 6).

The epidermis did not yet contain hair follicle and sebaceous gland, and the edge of the wound became thicker due to proliferation of the epitel cells. These macroscopic and microscopic observations under in vitro assessment revels that the PVA-PVP blended hydrogel can meet the efficacy requirement and its healing rate was comparable to that Sterile Gauze and Sofratulle. The hydrogel was also pleasant fell, comfortable, and does not disturb the formation of cells and new tissue on the skin.

4. CONCLUSION

The PVA-PVP blended hydrogel shows some properties thatcan meet the requirements of an ideal wound dressing. For example, it effectively absorbs the fluid, is pleasant to touch and painless to remove, exhibits high elasticity but good mechanical strength and good transparency, and can act as a barrier against microbes. This hydrogel wound dressing is highly potential for use in tropical environment.

ACKNOWLEDGEMENT

The author wishes to thank Prof. Dr. J.M. Rosiak and Dra. Nazly Hilmy, PhD., for their valuable suggestions. The authors also would like to appreciate Dr. Iwan Budiarso for his valuable discussion for in vitro assessment. Assistants to experiments by Ms. Dewi SP, Ms.

Yuharni, Ida and Rachmi are also acknowledged. This research work is partially supported by IAEA under a Research Contract No. 8978/R2/DPA.

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