PH-responsive release of chlorhexidine from modified nanoporous silica nanoparticles for dental applications

A pH-sensitive stimulus-response system for controlled drug release was prepared by modifying nanoporous silica nanoparticles (NPSNPs) with poly(4-vinylpyridine) using a bismaleimide as linker. At physiological pH values, the polymer serves as gate keeper blocking the pore openings to prevent the release of cargo molecules. At acidic pH values as they can occur during a bacterial infection, the polymer strains become protonated and straighten up due to electrostatic repulsion. The pores are opened and the cargo is released. The drug chlorhexidine was loaded into the pores because of its excellent antibacterial properties and low tendency to form resistances. The release was performed in PBS and diluted hydrochloric acid, respectively. The results showed a considerably higher release in acidic media compared to neutral solvents. Reversibility of this pH-dependent release was established. In vitro tests proved good cytocompatibility of the prepared nanoparticles. Antibacterial activity tests with Streptococcus mutans and Staphylococcus aureus revealed promising perspectives of the release system for biofilm prevention. The developed polymer-modified silica nanoparticles can serve as an efficient controlled drug release system for long-term delivery in biomedical applications, such as in treatment of biofilm-associated infections, and could, for example, be used as medical implant coating or as components in dental composite materials

Development of a flow chamber system for the reproducible <i>in vitro</i> analysis of biofilm formation on implant materials

<div><p>Since the introduction of modern dental implants in the 1980s, the number of inserted implants has steadily increased. Implant systems have become more sophisticated and have enormously enhanced patients’ quality of life. Although there has been tremendous development in implant materials and clinical methods, bacterial infections are still one of the major causes of implant failure. These infections involve the formation of sessile microbial communities, called biofilms. Biofilms possess unique physical and biochemical properties and are hard to treat conventionally. There is a great demand for innovative methods to functionalize surfaces antibacterially, which could be used as the basis of new implant technologies. Present, there are few test systems to evaluate bacterial growth on these surfaces under physiological flow conditions. We developed a flow chamber model optimized for the assessment of dental implant materials. As a result it could be shown that biofilms of the five important oral bacteria <i>Streptococcus gordonii</i>, <i>Streptococcus oralis</i>, <i>Streptococcus salivarius</i>, <i>Porphyromonas gingivalis</i>, and <i>Aggregatibacter actinomycetemcomitans</i>, can be reproducibly formed on the surface of titanium, a frequent implant material. This system can be run automatically in combination with an appropriate microscopic device and is a promising approach for testing the antibacterial effect of innovative dental materials.</p></div

Biofilm heights on titanium substrata in the flow chamber system.

<p>In each diagram, the mean biofilm heights for five independent experiments are shown. <b>A</b> = <i>S</i>. <i>gordonii</i>, <b><i>B</i></b> = <i>S</i>. <i>oralis</i>, <b>C</b> = <i>S</i>. <i>salivarius</i>, <b>D</b> = <i>P</i>. <i>gingivalis</i>, and <b>E</b> = <i>A</i>. <i>actinomycetemcomitans</i>.</p

3D reconstruction of biofilms in side view.

<p>The cells were stained live/dead and analysed by CLSM. Vital cells are depicted in yellow, viable cells in blue. <b>A)</b> <i>S</i>. <i>gordonii</i>, <b>B)</b> <i>S</i>. <i>oralis</i>, <b>C)</b> <i>S</i>. <i>salivarius</i>, <b>D)</b> <i>P</i>. <i>gingivalis</i>, and <b>E)</b> <i>A</i>. <i>actinomycetemcomitans</i>.</p

Sketch of the flow chamber and flow chamber system.

<p>A) Assembly drawing with test specimen; B) General setup of the closed circuit system. The red arrows indicate the direction of the flow.</p

The Peri-Implant and Periodontal Microbiota in Patients with and without Clinical Signs of Inflammation

Late implant failures, caused by the inflammation of surrounding tissues are a problem in implant dentistry. The path of bacterial transmission from teeth to implants is not completely understood. Therefore, the purpose of this study was to analyze intraindividual bacterial transmission characterizing subgingival microbiomes in teeth and implants, both in healthy subjects and in those with signs of periodontitis or peri-implantitis. Samples of peri-implant and dental sulcus fluid were collected. To identify the predominant microbiota, amplified fragments of bacterial 16S rRNA gene were separated by single strand conformation polymorphism analysis, sequenced and taxonomically classified. A total of 25 different predominant genera were found in the diseased group and 14 genera in the healthy group. Species richness did not differ significantly between implants, neighboring teeth and teeth with largest probing depth in the diseased group. Additionally, no differences between teeth and implants in the healthy group were detected. In contrast, microbial diversity varied between the different sampling points. Species richness is similar in healthy and diseased sites, but the composition of the bacterial community differed within the individual subjects. The underlying analyses strongly suggest that complete transmission from neighboring teeth to implants is unlikely