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Macrophage activation can be modulated by biomaterial topography according to the biological scale (micrometric and nanometric range). In this study, we investigated the effect of fiber diameter and fiber alignment of electrospun poly(L-lactic) (PLLA) scaffolds on macrophage RAW 264.7 activation and secretion of proinflammatory cytokines and chemokines at 24 h and 7 days. Macrophages were cultured on four different types of fibrous PLLA scaffold (aligned microfibers, aligned nanofibers, random microfibers, and random nanofibers) and on PLLA film (used as a reference). Substrate topography was found to influence the immune response activated by macrophages, especially in the early inflammation stage. Secretion of proinflammatory molecules by macrophage cells was chiefly dependent on fiber diameter. In particular, nanofibrous PLLA scaffolds minimized the inflammatory response when compared with films and microfibrous scaffolds. The histological evaluation demonstrated a higher number of foreign body giant cells on the PLLA film than on the micro- and nanofibrous scaffolds. In summary, our results indicate that the diameter of electrospun PLLA fibers, rather than fiber alignment, plays a relevant role in influencing in vitro macrophage activation and secretion of proinflammatory molecules.

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Summary Staphylococcus aureus is a leading cause of infective endocarditis (IE). Platelet activation promoted by

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In order to endow mesoporous bioactive glass, characterized by excellent bioactive properties, with additional biological functions, Cu-doped mesoporous SiO-CaO glass (Cu-MBG) in the form of nanoparticles was prepared by an ultra-sound assisted one pot synthesis. The analysis of the bacterial viability, using different bacterial strains, and the morphological observation of the biofilm produced by the Staphylococcus epidermidis, revealed the antimicrobial effectiveness of the Cu-MBG and the relative ionic extracts against both the bacterial growth and the biofilm formation/dispersion, providing a true alternative to traditional antibiotic systemic therapies. The proposed multifunctional agent represents a promising and versatile platform for bone and soft tissues regeneration.

Extracellular DNA (eDNA) is an important biofilm component that was recently discovered. Its presence has been initially observed in biofilms of Pseudomonas aeruginosa, Streptococcus intermedius, Streptococcus mutans, then Enterococcus faecalis and staphylococci. Autolysis is the common mechanism by which eDNA is released. In P. aeruginosa eDNA is generated by lysis of a bacterial subpopulation, under control of quorum sensing system. In E. faecalis autolysis proceeds in a fratricide mode, resulting from a process similar to necrosis of eukaryotic cells. In Staphylococcus aureus autolysis originates by an altruistic suicide, i.e., a programmed cell death similar to apoptosis of eukaryotic cells. In S. aureus autolysis is mediated by murein hydrolase, while in S. epidermidis by the autolysin protein AtlE. In P. aeruginosa eDNA is located primarily in the stalks of mushroom-shaped multicellular structures. In S. aureus the crucial role of eDNA in stabilizing biofilm is highlighted by the disgregating effect of DNase I. eDNA represents an important mechanism for horizontal gene transfer in bacteria. eDNA and other microbial structural motifs are recognized by the innate immune system via the TLR family of pattern recognition receptors (PRRs).

Binding of the fibronectin-binding protein FnBPA fromStaphylococcus aureus to the human protein fibronectin has previously been implicated in the development of infective endocarditis, specifically in the processes of platelet activation and invasion of the endothelium. We recently proposed a model for binding of fibronectin to FnBPA in which the bacterial protein contains 11 potential binding sites (FnBPA-1 to FnBPA-11), each composed of motifs that bind to consecutive fibronectin type 1 modules in the N-terminal domain of fibronectin. Here we show that six of the 11 sites bind with dissociation constants in the nanomolar range; other sites bind more weakly. The high affinity binding sites include FnBPA-1, the sequence of which had previously been thought to be encompassed by the fibrinogen-binding A domain of FnBPA. Both the number and sequence conservation of the type-1 module binding motifs appears to be important for high affinity binding. The in vivo relevance of the in vitro binding studies is confirmed by the presence of antibodies in patients with S. aureus infections that specifically recognize complexes of these six high affinity repeats with fibronectin.Staphylococcus aureus is one of the most important bacterial pathogens to affect humans. Clinical manifestations of infection range from superficial skin infections (1) to life-threatening conditions, such as endocarditis (2, 3) and difficult to treat infections of the bones and joints (4, 5). The increasing virulence and antibiotic resistance exhibited by this major source of both community and hospital-acquired infection presents an urgent challenge. Furthering our understanding of the mechanism by which staphylococcal pathogenesis occurs is thus imperative for the development of novel therapeutic and preventative strategies.Since attachment to host tissue is a critical early step in infection, one particular group of targets for intervention is the microbial surface components recognizing adhesive matrix molecules (MSCRAMM) 4 family of surface-expressed adhesins (6, 7). These proteins exploit extracellular matrix proteins, such as fibronectin (Fn), using them as a bridge between the bacterial cell surface and host cell receptors that effect downstream signaling (8, 9). Although classically regarded as an exclusively extracellular pathogen, S. aureus has been shown to adhere to and invade several host cell types (10 -14), and the Fn-binding subfamily of MSCRAMMs (FnBPs) appears to be involved in this process (15). There is an emerging view that S. aureus can exist intracellularly, hijacking and invading host cells to establish persistence (16). Conceivably, this mechanism could facilitate rapid and effective bloodstream dissemination while allowing the bacterium to evade antibiotics and host immune surveillance, an apposite theory given the prevalence of bacterial metastasis (3) and infection relapse in staphylococcal disease (17).Fn is a large glycoprotein present in a soluble form in human plasma and other body fluids and in an insoluble form in...