Thermoplastic polyurethane effective antibacterial wound dressing

Developing an ideal Meltblown TPU Nonwovens for the wound care applications dressing that meets the multiple demands of good biocompatibility, an appropriate porous structure, mechanical property and outstandingly good antibacterial activity against drug-resistant bacteria is highly desirable for clinical wound care. Biocompatible thermoplastic polyurethane  membranes are promising candidates as a scaffold; however, their lack of a suitable porous structure and antibacterial activity has limited their application. Antibiotics are generally used for preventing bacterial infections, but the global emergence of drug-resistant bacteria continues to cause social concer.Consequently, we prepared a flexible dressing based on a TPU membrane with a specific porous structure and then modified it with a biomimetic polydopamine coating to prepare in situ a nano-silver based composite via a facile and eco-friendly approach. SEM images showed that the  membranes were characterized by an ideal porous structure  that was decorated with nano-silver particles.

ATR-FITR and XRD spectroscopy further confirmed the stepwise deposition of polydopamine and nano-silver. Water contact angle measurement indicated improved surface hydrophilicity after coating with polydopamine. Tensile testing demonstrated that the  membranes had an acceptable mechanical strength and outstandingly good flexibility. Subsequently, bacterial suspension assay, plate counting methods and Live/Dead staining assays demonstrated that the optimized  membranes possessed outstandingly good antibacterial activity against P. aeruginosa, E. coli, S. aureus and MRSA bacteria, while CCK8 testing, SEM observations and cell apoptosis assays demonstrated that they had no measurable cytotoxicity toward mammalian cells. Moreover, a steady and safe silver-releasing profile recorded by ICP-MS confirmed these results. Finally, by using a bacteria-infected (MRSA or P. aeruginosa) murine wound model, we found that TPU/NS2.5 membranes could prevent in vivo bacterial infections and promote wound healing via accelerating the re-epithelialization process, and these membranes had no obvious toxicity toward normal tissues.Wound dressings play a critical role in the management of cutaneous wounds because they can protect the wounds and promote the regeneration of dermal and epidermal tissues.

Due to an increasing number of people suffering from burns, diabetic ulcers, venous ulcers  the demand for better dressings is growing dramatically. Generally, an ideal dressing should possess non-toxicity, biocompatibility, robust mechanical properties and suitable permeability for gas and water exchange. As natural biomaterials, collagen, gelatin, alginate and chitosan have been extensively used to prepare various types of dressings  due to their biocompatibility and biodegradability. However, their poor mechanical properties make it difficult for them to meet rigorous clinical requirements.Thermoplastic polyurethane  is a biocompatible and biodegradable elastomer that has been approved by the FDA, and has been widely applied in biomedical science . It has been reported that TPU can be used for catheters, vascular grafts and drug delivery carriers. Moreover, TPU also exhibits remarkable chemical stability and good mechanical properties. These performances indicate that TPU is a promising candidate for wound dressings.

However, lacking antibacterial activity would limit its application in wound care, as bacterial infections always pose a severe threat to the wound bed.A feasible way to solve this problem is to incorporate antibiotics such as amoxicillin, vancomycin or gentamicin into wound dressings. Nevertheless, the emergence of drug-resistance worldwide due to the overuse of antibiotics continues to threaten public health. Thus, alternative antibacterial agents are urgently needed. Nano-silver  as an outstandingly goodantibacterial agent with robust and broad-spectrum bactericidal activity against both Gram-positive and Gram-negative bacteria, including multi-drug-resistant bacteria such as methicillin-resistant staphylococcus aureus. More importantly, it has been proposed that nano-silver destroys bacteria through various mechanisms (cell membrane disruption, DNA replication interference, respiratory function inhibition without causing drug-resistance . However, the toxicity of nano-silver towards mammalian cells is a concern. Recent studies have demonstrated that the toxic effects of nano-silver occur only at high concentrations, and the incorporation of nano-silver into materials mitigates the toxicity. Consequently, nano-silver is considered as an ideal antibacterial agent for inclusion in biomaterials.