Preparation And Property Of A Novel Foam Made Of SA And SF Impregnated Of AgNPs Combined With VSD And Its Therapeutic Effect On Infected Wound Model

Backgroundrthe combat casualty can’t be treated completely under fire and in tactical filed. The medical resource is limited in the process of evacuation, therefore, our army need an effective and convenient caring production that has multifunction including prophylaxis and curing of infection, promoting cure of wound and decrease the nursing cost. Vacuum sealing drainage (VSD) and dressing containing silver are ordinary technique for anti-infection. No combination of these two technique in the use to treat combat casualty wound has been reported. The effect and the cost of nursing of it are remaining to require further investigation. Polyurethane is the conventional ingredient to produce foam of VSD. In the process of producing polyurethane foam, several poisonous materials have to be added as ingredient. Sodium alginate (SA) and silk fibroin (SF) are natural high molecular material which are excellent ingredient for preparation of novel foam.Objectives.to research and develop a novel foam of VSD using SA, SF and silver nanoparticles (AgNPs) as ingredients, toinvestigate the ratio and concentration that will make the foam do better in the performance of mechanical property, biocompatibility and anti-bacteria and to evaluate therapeutic effect and nursing cost of the combination the foam and VSD on wound infection.Method:I. Prepare the SA/SF solution according to the quality ratio of 1/0, 1/0,5/1,2/1,1/1,1/2,1/5,0/1 and then produce the foam. In the same method, prepare foam as quality ratio 5:1 with the concentration of 8%,6% and 4%. Choose a group with better property according the mechanical property test. Conduct examination of porosity, hydroscopicity, humectancy, and cytotoxicity to the preferred group.2. Add AgNPs with concentration of 0.25%,0.5% and 1% to the preferred group to choose a group with better performance of anti-bacteria according to the anti-bacteria vitro test. Perform cytotoxicity and AgNPs release vitro test to the preferred group.3.Establish the rabbit model of soft tissue staphylococcus aureus infection. Perform therapeutic experiment on 5 groups. Group a-AgNPs foam plus VSD, group b-AgNPs foam, group c-VSD, group d-infection control, group e-non-infection control. Evaluate the therapeutic effect according to the outcomes of bacteria count at multiple time point, ratio of infection clearance within one week and duration of wound curing.Result:1. the foam with the ratio of SA/SF between 5:1 and 2:1 and the SA concentration between 4%-8% faced the need of VSD. We choose 5:1 and 8%.0.5% AgNPs foam has good performance of vitro anti-bacteria test and cytotoxicity test. The foam can slowly release AgNPs in the vitro test.2. The bacteria counts of rabbit wound that were smeared 24 hours later were more than 105CFU/g; the incidence of infection clearance within 1 week of group a, b and c were 100%、37.5% and 25%, respectively; the average duration until wounds cured were 13.6,16.5 and 17.3 days. Difference between group a and both group b and c was significant. No difference was between group b and c.Conclusion:The silver foam made with SA and SF has faced the requirement that was needed as an VSD foam. When the AgNPs concentration was 0.5%, the foam had no cytotoxicity, can release AgNPs to the wound and had excellent performance of anti-bacteria in vitro. the combination of the foam and VSD had excellent therapeutic effect and low nursing cost on the infecting model of combat casualty wound.