Figure 6. Proposed mechanism of suture degradation with the help of 4HR.

Because 4HR is an amphiphilic chemical, it has both hydrophobic and hydrophilic regions. A hydrophobic long alkyl group can interact with the hydrophobic domain of silk sutures. To interact with the hydrophilic domain of silk sutures, 4HR competes with water, and a high-density 4HR micelle forms in vicinity of the hydrophilic domain of the silk suture through preferential hydration. Most of the high-density 4HR micelles are mostly released within a short period of time after implantation because the hydrogen bond of 4HR with silk protein is weak compared to that with water. Firmly bound 4HR in a hydrophobic domain is exposed during the wound remodeling phase by macrophages. The released 4HR induces MMPs in macrophages and produces MMPs that can digest silk suture material.