This study describes the synthesis of bifunctional nanomaterials that can both inhibit bacterial bioluminescence, an indicator for the bacterial fitness, and, simultaneously, improve the proliferation of eukaryotic cells, a property that is desired for biomedical devices such as implants. To prepare this functional nanomaterial, the pores of the periodic mesoporous organosilica (PMO) nanocontainers are first functionalized with dexamethasone (Dex), which has anti‐inflammatory and cell proliferation properties. Then, the external surface of the PMO is functionalized with the antibacterial and cell adhesive bipolymer poly‐d‐lysine (PDL). The results show that cofunctionalization of the PMO surfaces with both Dex and PDL have beneficial additive and/or synergistic effects on cell proliferation and bacterial bioluminescence inhibition.
Alphaproteobacteria belonging to the group of the sphingomonads are frequently found in biofilms colonizing pure-water systems, where they cause technical and hygienic problems. In this study, physiological properties of sphingomonads for biofilm formation on plastic surfaces were analysed.
Sphingomonas
sp. strain S2M10 was isolated from a used water-filtration membrane and submitted to transposon mutagenesis for isolating mutants with altered biofilm formation. Mutants showing strongly decreased biofilm formation carried transposon insertions in genes for the biosynthesis of the polysaccharide sphingan and for flagellar motility. Flagella-mediated attachment was apparently important for biofilm formation on plastic materials of intermediate hydrophobicity, while a mutant with defect in spnB, encoding the first enzyme in sphingan biosynthesis, showed no biofilm formation on all tested materials. Sphingan-dependent biofilm formation was induced in the presence of specific carbon sources while it was not induced in complex medium with yeast extract and tryptone. The regulation of sphingan-based biofilm formation was investigated by interfering with the CckA/ChpT/CtrA phosphorelay, a central signal-transduction pathway in most Alphaproteobacteria. Construction and ectopic expression of a kinase-deficient histidine kinase CckA caused cell elongation and massive sphingan-dependent cell aggregation. In addition, it caused increased activity of the promotor of spnB. In conclusion, these results indicate that sphingan-based biofilm formation by sphingomonads might be triggered by specific carbon sources under prototrophic conditions resembling a milieu that often prevails in pure-water systems.
Biomaterial-associated
infections are a major cause of biomaterial
implant failure. To prevent the initial attachment of bacteria to
the implant surface, researchers have investigated various surface
modification methods. However, most of these approaches also prevent
the attachment, spread, and growth of mammalian cells, resulting in
tissue integration failure. Therefore, the success of biomaterial
implants requires an optimal balance between tissue integration (cell
adhesion to biomaterial implants) and inhibition of bacterial colonization.
In this regard, we synthesize bifunctional nanomaterials by functionalizing
the pores and outer surfaces of periodic mesoporous organosilica (PMO)
with antibacterial tetracycline (Tet) and antibacterial and cell-adhesive
bipolymer poly-d-lysine (PDL), respectively. Then, the fabricated TetPMO-PDL nanomaterials are incorporated into alginate-based
hydrogels to create injectable and 3D-printable nanocomposite (NC)
hydrogels (AlgL-TetPMO-PDL). These bifunctional nanomaterial
and 3D-printable NC hydrogel show pH-dependent release of Tet over
7 days. They also enhance the proliferation of eukaryotic cells (fibroblasts). TetPMO-PDL is inactive in reducing Pseudomonas
aeruginosa, Staphylococcus aureus, and Enterococcus faecalis biofilms.
However, AlgL-TetPMO-PDL shows significant antibiofilm
activity against P. aeruginosa. These
results suggest that the incorporation of TetPMO-PDL into
AlgL may have a synergistic effect on the inhibition of the Gram-negative
bacterial (P. aeruginosa) biofilm,
while this has no effect on the reduction of the Gram-positive bacterial
(S. aureus and E. faecalis) biofilm.
In the biomedical field, silicon-based materials are widely used as implants, biomedical devices, and drug delivery systems. Although these materials show promise for implant technologies and clinical applications, many of them fail to simultaneously possess key properties, such as mechanical stability, biostability, stretchability, cell adhesiveness, biofilm inhibition, and drug delivery ability. Therefore, there is considerable need for the development and improvement of new biomaterials with improved properties. In this context, we describe the synthesis of a new hybrid nanocomposite material that is prepared by incorporating bifunctional nanomaterials onto glass and polydimethylsiloxane surfaces. The results show that our hybrid nanocomposite material is elastic, stretchable, injectable, biostable, has pH-controlled drug delivery ability, and display improved cell adhesion and proliferation and, at the same time, impacted bacterial biofilm formation on the respective surfaces.
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