Bioactive glass combined with bisphosphonates provides protection against biofilms formed by the periodontal pathogen Aggregatibacter actinomycetemcomitans.

Biofilms play a pivotal role in the progression of periodontitis and they can be treated with antiseptics (i.e. chlorhexidine) or antibiotics, but these therapeutic alternatives are unable of ameliorating periodontal alveolar bone loss, which has been, on the other hand, successfully treated with bone-preserving agents. The improved bone formation achieved in animal models by the combination of two such agents: bioactive glass (BAG) and bisphosphonates has attracted the interest for further exploring dental applications. However, the antimicrobial effects that may result from combining them have not been yet investigated. Here, our aim was to explore the anti-biofilm effects that could result from combining BAG with bisphosphonates, particularly in a dental biofilm model. The experiments were performed with an oral cavity single-specie (Aggregatibacter actinomycetemcomitans) biofilm assay, which was optimized in this contribution. Risedronate displayed an intrinsic anti-biofilm effect, and all bisphosphonates, except clodronate, reduced biofilm formation when combined with BAG. In particular, the anti-biofilm activity of risedronate was significantly increased by the combination with BAG. Since it has been proposed that some of the antimicrobial effects of BAG are caused by local pH changes, studies of pH variations were performed to gain a mechanistic understanding. However, the observed anti-biofilm effects could not be explained with lowered pHs. Overall, these results do provide further support for the promising use of bisphosphonate-BAG combinations in dental applications. These findings are particularly relevant for patients undergoing cancer chemotherapy, or osteoporotic patients, which are known to be more vulnerable to periodontitis. In such cases, bisphosphonate treatment could play a double positive effect: local treatment of periodontitis (in combination with BAG) and systemic treatment of osteoporosis, prevention of hypercalcemia and metastases.

Protein and bacterial interactions with nanostructured polymer coatings.

Adsorption of proteins and adhesion of bacteria to a surface is affected by chemical and physical interactions. In this study, polymer coatings and their ability to adsorb avidin and Staphylococcus aureus were investigated. The surface chemistry and topography of the polymer coatings was modified by changing the weight ratio of the hydrophobic polystyrene (PS) and the hydrophilic acrylonitrile butadiene styrene (ABS) components in the polymer blend. Avidin adsorbed less to the ABS phase compared with the PS phase. The side-on orientation of avidin on the ABS surface, however, resulted in a higher specific binding of biotinylated bovine serum albumin. Steric effects and hydrophobic protein-surface interactions decreased the activity of avidin on the PS phase. The increased hydrophobicity and roughness of the polymer coatings enhanced the adhesion of S. aureus. The avidin-coated latex surface with 55% relative surface coverage of the PS phase showed anti-microbial behavior.

Enhanced protein adsorption and patterning on nanostructured latex-coated paper.

Specific interactions of extracellular matrix proteins with cells and their adhesion to the substrate are important for cell growth. A nanopatterned latex-coated paper substrate previously shown to be an excellent substrate for cell adhesion and 2D growth was studied for directed immobilization of proteins. The nanostructured latex surface was formed by short-wavelength IR irradiation of a two-component latex coating consisting of a hydrophilic film-forming styrene butadiene acrylonitrile copolymer and hydrophobic polystyrene particles. The hydrophobic regions of the IR-treated latex coating showed strong adhesion of bovine serum albumin (cell repelling protein), fibronectin (cell adhesive protein) and streptavidin. Opposite to the IR-treated surface, fibronectin and streptavidin had a poor affinity toward the untreated pristine latex coating. Detailed characterization of the physicochemical surface properties of the latex-coated substrates revealed that the observed differences in protein affinity were mainly due to the presence or absence of the protein repelling polar and charged surface groups. The protein adsorption was assisted by hydrophobic (dehydration) interactions.

Biocompatibility of printed paper-based arrays for 2-D cell cultures.

The use of paper-based test platforms in cell culture experiments is demonstrated. The arrays used for two-dimensional cell cultures were prepared by printing patterned structures on a paper substrate using a hydrophobic polydimethylsiloxane (PDMS) ink. The non-printed, PDMS-free areas formed the array for the cell growth experiments. Cell imaging was enabled by using a lipophilic staining agent. A set of coated paper substrates was prepared to study the effect of the physicochemical properties of the substrate (topography, roughness and surface energetics) on cell attachment and growth. The studied paper substrates were found to be cell-repellent or cell-supporting. Cell growth was supported by substrates with a large bearing area, low surface area ratio (Sdr), high total surface free energy and an intermediate electron donor surface energy component. The cells were grown to full confluency within 72 h.