Micrococcal Nuclease stimulates Staphylococcus aureus Biofilm Formation in a Murine Implant Infection Model

Advancements in contemporary medicine have led to an increasing life expectancy which has broadened the application of biomaterial implants. As each implant procedure has an innate risk of infection, the number of biomaterial-associated infections keeps rising. Staphylococcus aureus causes 34% of such infections and is known as a potent biofilm producer. By secreting micrococcal nuclease S. aureus is able to escape neutrophil extracellular traps by cleaving their DNA-backbone. Also, micrococcal nuclease potentially limits biofilm growth and adhesion by cleaving extracellular DNA, an important constituent of biofilms. This study aimed to evaluate the impact of micrococcal nuclease on infection persistence and biofilm formation in a murine biomaterial-associated infection-model with polyvinylidene-fluoride mesh implants inoculated with bioluminescent S. aureus or its isogenic micrococcal nuclease deficient mutant. Supported by results based on in-vivo bioluminescence imaging, ex-vivo colony forming unit counts, and histological analysis it was found that production of micrococcal nuclease enables S. aureus bacteria to evade the immune response around an implant resulting in a persistent infection. As a novel finding, histological analysis provided clear indications that the production of micrococcal nuclease stimulates S. aureus to form biofilms, the presence of which extended neutrophil extracellular trap formation up to 13 days after mesh implantation. Since micrococcal nuclease production appeared vital for the persistence of S. aureus biomaterial-associated infection, targeting its production could be a novel strategy in preventing biomaterial-associated infection

A Universal Nanogel-Based Coating Approach for Medical Implant Materials

Coatings are essential for biomedical applications antifouling and antimicrobialproperties, supporting cell adhesion and tissue integration and particularlyinteresting in this field are nanogel (nGel)-based coatings. Since biomaterialsdiffer in physiochemical properties, specific nGel-coating strategies need to bedeveloped for every distinct material, leading to complex coating strategies.Hence, the solution lies in adopting a universal strategy to apply the same nGelcoating with the same function on a wide range of implant surfaces. To this end, auniversal nGel-based coating approach provides the same coating using a singlemethod on implant materials including stiff polymer materials, metals, ceramics,glass, and elastomers. The coating formation is achieved by electrostatic interactionsbetween oxygen plasma–activated surfaces and positively charged nGelsusing a spray-deposition method. Fluorescent labels are introduced into thenGels as a model for post-modification capabilities to increase the functionality ofthe coating. The coating is highly stable under in vitro physiological conditionswith the retention of its function on different clinically relevant materials.Meanwhile, the in vivo study indicates that the nGel coating on a polyvinylidenefluoride hernia mesh is stable and biocompatible, therefore, making the coatingand the coating strategy, a highly impactful approach for future clinicaldevelopments