OBJECTIVETo investigate the biological characteristics of xenogenic acellular dermal matrix( Xeno-ADM) incorporated with silver, and to observe its effect in grafting.

METHODSXeno-ADM was prepared with 0. 25% trypsin and 0. 5% triton X-100 , and then it was immersed in 2 g/L silver nitrate solution to prepare xeno-ADM incorporated with silver. The bacterial inhibitory effect of two kinds of xeno-ADM on burn wound was determined, and the histological characteristic of the wounds was observed with optical microscope, transmission electron microscope and scanning electron microscope. The Ag+ content in the xeno-ADM incorporated with silver was measured with atomic absorption spectrometer. Twenty-seven rabbits with full-thickness skin defects on the back were randomly divided into three groups, i. e. split-thickness skin autograft only( group A, n = 9) , xeno-ADM with overlying split-thickness skin autograft( group B, n = 9) , xeno-ADM incorporated with silver with overlying split-thickness skin autograft ( group C, n = 9). The skin specimens from grafted area in each group were harvested at 2,4 and 6 post-operation weeks( POW) and examined under light microscope and transmission electron microscope. The condition of the graft, the contraction degree of the grafts and the historical changes in grafting area were observed at 2,4,6 POW. The survival rate of the grafts was calculated and the proliferative activity of the lymphocyte in each group was determined at 2 POW.

RESULTS1. Compared with xeno-ADM, the anti-bacterial effect of xeno-ADM incorporated with silver was much better ( P < 0. 05). No epidermis was seen in both types of xenografts ,and the collagen fibers were even in size and arranged regularly, with no obvious degeneration, and the dermis was also devoid of cells and cellular components. The Ag + content in xeno-ADM incorporated with silver measured (2. 7+/-0. 7) mg/g. 2. The grafts in B and C groups presented similar color to that of normal skin at 6 POW, and it was smooth, with fine texture and no scarring. The collagen fibers was arranged regularly, and conjunction between epidermis and dermis, the structure of basal cell desmosome and semi-desmosome were well reconstructed. The grafts in A group was in dark red color, with obvious contraction, and easily broken. The contraction rate in A group at 2,4 and 6 POW were obviously higher than those in B and C groups( P < 0. 05), while no obvious difference was observed between B and C groups. ( P >0. 05). The overall survival rate of the grafts in C group at 2 POW was 91.7% , which was evidently higher than that in A (77.8%) and B (80. 6% ) groups. The lymphocyte proliferative activity exhibited no difference among A, B and C groups( P >0.05).

CONCLUSIONThe xeno-ADM incorporated with silver has good anti-bacterial effect. In addition, it preserves the basic tissue structure and integral collagen fiber scaffold, without cells to induce rejection, so that it can be used as an ideal dermal substitute.