No abstract

To address the challenge from microbial resistance and biofilm, this work develops three gemini peptide amphiphiles with basic tetrapeptide spacers 12-(Arg)4-12, 12-(Lys)4-12, and 12-(His)4-12 and finds that they exhibit varied antimicrobial/antibiofilm activities. 12-(Arg)4-12 shows the best performance, possessing the broad-spectrum antimicrobial activity and excellent antibiofilm capacity. The antimicrobial and antibiofilm activities strongly depend on the membrane permeation and self-assembling structure of these peptide amphiphiles. Gemini peptide amphiphile with highly polar arginine as the spacer, 12-(Arg)4-12, self-assembles into short rods that are prone to dissociate into monomers for permeating and lysing membrane , leading to its broad-spectrum antimicrobial activity and high efficiency in eradicating biofilm. Long rods formed by relatively weaker polar 12-(Lys)4-12 are less prone to disassemble into monomers for further membrane permeation, which makes it selectively kill more negatively charged bacteria and endow it medium antibiofilm activity. Low polar 12-(His)4-12 aggregates into long fibers, which are very difficult to dissociate and they mainly electrostatically bind on the negative microbial surface, resulting in its weakest antimicrobial and antibiofilm activity. This study reveals the effect of the antimicrobial peptide structure and aggregation on the antimicrobial activities and would be helpful for developing high-efficient antimicrobial peptides with antibiofilm activity.

A coating with programmable multifunctionality based on application requirements is desirable. However, it is still a challenge to prepare a hard and flexible coating with a quick self-healing ability. Here, a hard but reversible Si–O–Si network enabled by aminopropyl-functionalized poly­(silsesquioxane) and triethylamine (TEA) was developed. On the basis of this Si–O–Si network, basic coatings with excellent transparency, hardness, flexibility, and quick self-healing properties can be prepared by filling soft polymeric micelles into hard poly­(silsesquioxane) networks. The highly cross-linked continuous network endows the coating with a hardness (H = 0.83 GPa) higher than those of most polymers (H < 0.3 GPa), while the uniformly dispersed micelles decrease the Young’s modulus (E = 5.89 GPa) to a value as low as that of common plastics, resulting in excellent hardness and flexibility, with an H/E of 14.1% and an elastic recovery rate (W e) of 86.3%. Scratches (∼50 μm) on the coating can be healed within 4 min. The hybrid composition of poly­(silsesquioxane) networks also shows great advantages in integration with other functional components to realize programmable multifunctionality without diminishing the basic properties. This nanocomposite design provides a route toward the preparation of materials with excellent comprehensive functions without trade-offs between these properties.