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In many technological areas, especially in the medical sector, stainless steel parts are being used due to their longevity, good biocompatibility, and high resistance against hygrothermal conditions related to sterilization procedures. Numerous medical products include an adhesive bond that have to reliably withstand these harsh conditions encountered, for example, during autoclaving. However, well established adherent treatment procedures require hazardous chemicals or are not suitable for small fragile parts, for example, components of endoscopes. Therefore, efficient alternatives are necessary. This publication thus presents a combined surface treatment procedure of laser ablation/structuring and flame silicatization. The investigations demonstrate that the resistance to hygrothermal ageing of stainless steel adhesive joints can be significantly increased by pulsed laser irradiation. However, a drastic improvement can only be achieved when the laser fluence exceeds a certain threshold value and, in addition, a nanoporous oxide layer with a reduced chromium content is formed. For substrates of this surface type, ageing resistance can be increased even further by subsequent flame silicatization treatment. The combined methods have proven to be superior as compared to well established processes like sand blasting and coating or corundum blasting. [ABSTRACT FROM AUTHOR]

The rising number of antibiotic‐resistant bacteria requires alternative antibacterial substances as therapeutics. However, besides a strong effect against bacteria, they should not exhibit cytotoxicity towards human cells. Typically, both properties are tested in separate in vitro experiments that do not take into account naturally occurring interactions. To analyze whether the bacteria‐cell interaction influences the results of antibacterial and cytotoxic testing, surfactant‐free antibacterial silver‐gold alloy nanoparticles produced by laser ablation in liquid were examined both separately and in a straightforward coculture setup. Whereas different commensal bacteria and human skin cells exhibited reduced metabolic activity at comparable concentrations when treated separately, their response completely differed when analyzed in a combined coculture. For the combination of oral keratinocytes and Staphylococcus aureus, reduced cytotoxicity with increasing cell numbers, but a similar antibacterial effect quantified by standard plate counting could be observed. In contrast, coculture of keratinocytes and Porphyromonas gingivalis resulted in a complete absence of cytotoxicity and antibacterial effect, probably due to bacterial invasion of cells. These results clearly showed that the bacteria‐cell interaction greatly influences the results of antibacterial and cytotoxic testing and highlight the importance of more complex in vitro experiments to reliably characterize novel antibacterial substances for efficient clinical translation. [ABSTRACT FROM AUTHOR]

Elemental silver nanoparticles are an effective antibacterial substance and are found as additive in various medical applications. Gold nanoparticles are used due to their optical properties in microscopy and cancer therapy. These advantages might be combined within alloyed nanoparticles of both elements and thereby open new fields of interest in research and medical treatment. In this context, laser ablation of solid alloys in liquid gives access to colloidal silver-gold alloy nanoparticles with a homogeneous ultrastructure. Elemental and alloy silver-gold nanoparticles with increasing molar fractions of silver (50, 80, and 100%) were produced and stabilized with citrate or albumin (BSA). Particles were embedded in agar at concentrations of 3-100 [micro]g [cm.sup.-3] and tested on clinical relevant Staphylococcus aureus regarding their antibacterial properties. Cytotoxic effects were measured within the same particle concentration range using human gingival fibroblasts (HGFib). As expected, a reduced fraction of silver in the nanoalloys decreased the antibacterial effect on S. aureus according to the evaluated minimal inhibitory concentrations. However, this decrease turned out stronger than expected by its relative mass per particle, due to the electrochemical, disproportionally high effect of gold on the bioresponse to silver within silver-gold nanoalloy particles. BSA was able to stabilize all colloids and maintain antibacterial activity, whereas sodium citrate reduced antibacterial effects and cytotoxicity even at high nanoparticle concentrations. The alloying of silver with gold by laser ablation in liquid produced nanoparticles with both reduced antibacterial and cytotoxic properties in comparison to silver nanoparticles but still retains the application spectrum of both elements combined in one colloid. In particular, alloying with gold may render silver nanoparticles more biocompatible, and allows bioconjugation via established thiol chemistry. Keywords AgAu * nanotoxicology * antibacterial * nanocolloids, Introduction Alloying of metals has been established for centuries in material science and metallurgy, aiming at the optimization of material properties and functionality. Multifunctional materials attract a lot of attention [...]

With the aim to design bioactive dental restorative material, the present study investigated the influence of the antimicrobial agents chlorhexidine diacetate (CHX) and octinidine (di)hydrochloride (ODH) when incorporated in two different materials. Selected parameters were polymerization enthalpy, short‐term drug release, and the effect on Streptococcus mutans as well as human gingival fibroblasts. Samples were made by mixing a nano‐hybrid ormocer (O) and a methacrylate‐based nano‐hybrid composite (C), each with a mass fraction of 2% CHX or ODH. Release profiles and concentrations of active agents from the resins were assessed, and the cell proliferation of human gingival fibroblasts as well as Streptococcus mutans cultured with the eluates were evaluated. The influence on polymerization was assessed by means of differential scanning calorimetry. Both drugs, especially ODH, showed a decreasing effect on polymerization enthalpies associated with a lowered crosslinking degree. At the same time ODH appeared to be released more persistently than CHX. Moreover, ODH was more efficient with regard to bacteria growth inhibition but also more cytotoxic in terms of reduction of cell viability. ODH is deemed more appropriate for application in a dental resin‐based drug delivery system, because of the more persistent drug release than seen for CHX. [ABSTRACT FROM AUTHOR]

Oral innate immunity is led by neutrophils. It is still unclear how their main antimicrobial mechanisms against different biofilms may contribute to balance or dysregulation in the oral cavity. We investigated the capacity of commensal (Streptococcus oralis) and pathogenic (Porphyromonas gingivalis or Aggregatibacter actinomycetemcomitans) monospecies biofilms to induce or to inhibit selected antimicrobial mechanisms of neutrophils. S. oralis induced neutrophil extracellular traps (NETs) formation, reactive oxygen species (ROS) production, and matrix metalloproteinases (MMPs) 8 and 9 secretion. However, these responses were partially reduced in PMA-activated neutrophils indicating a balance-like neutrophil response, which might be important for the maintenance of oral health. P. gingivalis generally induced ROS. Reduced NET formation and significantly decreased MMP secretion were detectable in activated neutrophils highlighting P. gingivalis' nucleolytic and proteolytic activity, which might support bacterial colonization and pathogenesis of periodontitis. In contrast, A. actinomycetemcomitans did not affect the levels of antimicrobial factors in activated neutrophils and induced NET formation, ROS production, and secretion of MMP-8 and -9 in neutrophils alone, which might contribute to tissue destruction and disease progression. In summary, neutrophil responses to biofilms were species-specific and might support either maintenance of oral health or pathogenesis of periodontitis depending on the species. [ABSTRACT FROM AUTHOR]