SURFACE CHARACTERIZATION OF TISSUE ADHESIVES APPLIED TO HUMAN SKIN

摘要

Since the details of adhesive bonding often dictate the failure mechanisms observed, it is important to note those details as possible limitations of the results from the studies we have so far completed. Under an approved human subjects protocol, five test zones were identified on each of the forearms of each of the volunteers. Four different pre-cleaning procedures were employed, using a single procedure/reagent for each arm on each of four visits to the hospital laboratory, one visit every two weeks. The washing procedures utilized commercial Dial, or Neutrogena, products or Betadine (a surgical scrub product) or generic rubbing alcohol. Five adhesives were applied and separated from each of the volunteers' forearm skin surfaces on each of their visits to the laboratory. All the adhesives were tested as 3/4" (19 mm) square patches with identical, stiff tabs at one edge for gripping by a clip from the mechanical testing unit. The adhesives were uniformly pressed to the skin surfaces by rolling a 3.75 lb cylindrical weight across the back of each applied adhesive square, 5 times. On the second and fourth visits of each volunteer, glistening wound sites were created on the forearm test areas by tape-stripping of epidermal layers from the stratum comeum, each wound about 35mm square. To these sites, only approved wound adhesive preparations were applied, and counted as 2 of the 5 adhesives tested on those occasions. All adhesives were allowed to remain in place on the selected skin site surfaces for 30 minutes, before removing each adhesive with a 90-degree peel test while recording the force (less than 2 pounds) generated at a peel rate of 20 mm/minute. The re-exposed skin surfaces were promptly applied to the germanium prism surface already calibrated and standing by in an adjacent infrared spectrophotometer. Later, the peeled adhesive face was analyzed against the same, re-cleaned prism surface. In view of these experimental limits, it is seen from Figures 1 and 2 how both the path and force of mechanical separation of a common acrylic-based "sports strip" adhesive are differentially displayed from a female versus a male volunteer's skin. The results are not only conditioned by the precleaning regimen applied, but also seldom show the same prompt detachment from females as from males. This is a general feature of our substantial body of experimental data now being examined both systematically and statistically for later publication. Tables 1 and 2, data from the infrared spectra characterizing the separated surfaces for the same skin/adhesive combinations for a female volunteer, show that the modes of failure shift. There is essentially purely adhesive failure-through the acrylic phase-for alcohol-cleaned skin, to partial delamination of the skin stratum corneum layers from one another (transferring skin cells to the acrylic) for Betadine-cleaned skin. Table 1 also shows, typical of the results with male volunteers, delamination through the horny stratum corneum layer to characterize even the most strongly bonded alcohol-cleaned skin surfaces (a result seldom seen with female volunteers). Table 1 further documents similar findings for the same adhesive system applied to alcohol-cleaned human neonatal foreskin. When the skin of male volunteers is tape-stripped to remove the superficial horny layers, producing a moist wound bed, relatively clean delamination of a wound- care adhesive is noted as typified in Figure 3. Again, the contrast with the results for female volunteers is interesting, as Figure 4 documents the transfer of some biological material (protein-based) to the same adhesive surface. Finally, Figure 5 illustrates the case of mixed adhesive failure when a particular combination of wound cleaning and application of a hydrocolloid gel skin care product leads to patchy transfer of biological debris to the gel adhesive and retention of the adhesive in the wound bed. These methods should allow rapid evaluation of new c