Novel Sensing Strategies Based on Monolayer Protected Gold Nanoparticles for the Detection of Metal Ions and Small Molecules.

Monolayer protected gold nanoparticles (AuNPs) have a huge potential for the development of innovative sensing systems for the detection of metal ions and small molecules. The organic ligand shell, primarily utilized to stabilize the gold core, can be rationally designed to promote selective interactions with a desired analyte. In addition, the outstanding physical and optical properties of AuNPs can be exploited to obtain analytically useful signals upon analyte binding. In this account, we review recent advances in AuNP-based sensing systems emphasizing on the rational design of the ligand shell for detection of heavy metal ions and small molecules. We examine various strategies of detection by evaluating their improvements in terms of sensitivity, selectivity and applicability to real samples.

Core-Shell Silver Nanoparticles in Endodontic Disinfection Solutions Enable Long-Term Antimicrobial Effect on Oral Biofilms.

To achieve effective long-term disinfection of the root canals, we synthesized core-shell silver nanoparticles (AgNPs@SiO2) and used them to develop two irrigation solutions containing sodium phytate (SP) and ethylene glycol-bis(ß-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA), respectively. Ex vivo studies with instrumented root canals revealed that the developed irrigation solutions can effectively remove the smear layer from the dentinal surfaces. Further in vitro experiments with single- and multispecies biofilms demonstrated for the first time that AgNPs@SiO2-based irrigation solutions possess excellent antimicrobial activities for at least 7 days, whereas the bare AgNPs lose the activity almost immediately and do not show any antibacterial activity after 2 days. The long-term antimicrobial activity exhibited by AgNPs@SiO2 solutions can be attributed to the sustainable availability of soluble silver, even after 7 days. Both solutions showed lower cytotoxicity toward human gingival fibroblasts compared to the conventionally used solution (3% NaOCl and 17% EDTA). Irrigation solutions containing AgNP@SiO2 may therefore be highly promising for applications needing a long-term antimicrobial effect.

A silica-based magnetic platform decorated with mixed ligand gold nanoparticles: a recyclable catalyst for esterification reactions.

A novel and convenient synthetic strategy for the preparation of magnetically responsive silica nanospheres decorated with mixed ligand protected gold nanoparticles is described. Gold nanoparticles are attached to the silica surface via stable amide bond formation. The hierarchical nanospheres show promising results as reusable and efficient catalysts for esterification reactions and they can be recovered through a simple magnetic separation.