The purpose of this investigation was to examine the inhibitory effects of aqueous extracts derived from the bark-containing sticks (Neem stick) of Azadirachta indica upon bacterial aggregation, growth, adhesion to hydroxyapatite, and production of insoluble glucan, which may affect in vitro plaque formation. Neem stick extracts were screened for minimal bacterial growth inhibition (MIC) against a panel of streptococci by means of a broth dilution assay. Initial bacterial attachment was quantified by the measurement of the adhesion of 3H-labeled Streptococcus sanguis to saliva-conditioned synthetic hydroxyapatite. The effect of the Neem stick extract upon insoluble glucan synthesis was measured by the uptake of radiolabeled glucose from 14C-sucrose. Aggregating activity of the Neem stick extracts upon a panel of streptococci was also examined. No inhibition of bacterial growth was observed among the streptococcal strains tested in the presence of < or = 320 micrograms/mL of the Neem stick extract. The pre-treatment of S. sanguis with the Neem stick extract or the gallotannin-enriched extract from Melaphis chinensis at 250 micrograms/mL resulted in a significant inhibition of the bacterial adhesion to saliva-conditioned hydroxyapatite. Pre-treatment of saliva-conditioned hydroxyapatite with the Neem stick or gallotannin-rich extract prior to exposure to bacteria yielded significant reductions in bacterial adhesion. The Neem stick extract and the gallotannin-enriched extract from Melaphis chinensis inhibited insoluble glucan synthesis. Incubation of oral streptococci with the Neem stick extract resulted in a microscopically observable bacteria aggregation. These data suggest that Neem stick extract can reduce the ability of some streptococci to colonize tooth surfaces.
The last decades have witnessed a major advancement and development in three-dimensional (3D) printing technology. In the future, the trend’s utilization of 3D printing is expected to play an important role in the biomedical field. This work presents co-extrusion of the polylactic acid (PLA), its derivatives (sPLA), and chitosan with the aim of achieving filaments for printing 3D objects, such as biomedical tools or implants. The physicochemical and antimicrobial properties were evaluated using SEM, FT-IR, DSC, instrumental mechanical test, and based on the ASTM E2149 standard, respectively. The addition of chitosan in the PLA and sPLA filaments increased their porosity and decreased density. The FT-IR analysis showed that PLA and chitosan only formed a physical mixture after extrusion. The addition of chitosan caused deterioration of the mechanical properties of filaments, especially elongation at break and Young’s modulus. The addition of chitosan to the filaments improved their ability to crystallize and provide their antimicrobial properties against Escherichia coli and Staphylococcus aureus.
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