The present study describes a novel antimicrobial surface using anodic oxidation of titanium and biofunctional detonation nanodiamonds (ND). ND have been loaded with antibiotics (amoxicillin or ampicillin) using poly(diallyldimethylammonium chloride) (PDDA). Successful conjugation with PDDA was determined by dynamic light scattering, which showed increase in the hydrodynamic diameter of ND agglomerates and shift of zeta potential towards positive values. The surface loading of amoxicillin was determined using UV–vis spectroscopy and the maximum of 44% surface loading was obtained. Biofunctional ND were immobilized by anodic oxidation within a titanium oxide layer, which was confirmed by scanning electron microscopy. The in vitro antimicrobial properties of ND suspensions were examined using Kirby-Bauer test with E. coli. Modified titanium surfaces comprising biofunctional ND were evaluated with E. coli inoculum by live/dead assay staining. Both biofunctional ND suspensions and modified titanium surfaces presented inhibition of bacteria growth and increase in bacteria lethality.
Bacterial surface layer proteins (S-layer) possess unique binding properties for metal ions. By combining the binding capability of S-layer proteins with the optical properties of gold nanoparticles (AuNP), namely plasmonic resonance, a colorimetric detection system for metal and metalloid ions in water was developed. Eight Slayer proteins from different bacteria species were used for the functionalization of AuNP. The thus developed biohybrid systems, AuNP functionalized with S-layer proteins, were tested with different metal salt solutions, e.g. Indium(III)-chloride, Yttrium(III)-chloride or Nickel(II)-chloride, to determine their selective and sensitive binding to ionic analytes. All tested S-layer proteins displayed unique binding affinities for the different metal ions. For each S-layer and metal ion combination markedly different reaction patterns and differences in concentration range and absorption spectra were detected by UV/vis spectroscopy. In this way, the selective detection of tested metal ions was achieved by differentiated analysis of a colorimetric screening assay of these biohybrid systems. A highly selective and sensitive detection of yttrium ions down to a concentration of 1.67 × 10 −5 mol/l was achieved with S-layer protein SslA functionalized AuNP. The presented biohybrid systems can thus be used as a sensitive and fast sensor system for metal and metalloid ions in aqueous systems.
Abstract. The biotechnological use of bacterial cells and cell components for the detection and accumulation of valuable substances, such as metals and rare earth elements in aqueous systems, is possible by utilizing innate binding characteristics of microorganisms. We have studied the bacteria cells of Lysinibacillus sphaericus JG-B53 and Sporosarcina ureae ATCC 13881 to assess their potential applicability for the detection of rare earth elements, base metals or precious metals in water. First, we have demonstrated the interactions of the cells with the metal complexes of Au, Ho and Y by studying the color changes of the respective solutions, scanning electron microscopy (SEM) imaging of the metal cluster decoration on the cell surfaces and cell growth tolerance tests. Based on these results, we have developed two potential sensor systems. A colorimetric sensor was established by applying gold nanoparticles (AuNPs) functionalized with surface-layer (S-layer) proteins SslA of S. ureae ATCC 13881 or Slp1 of L. sphaericus JG-B53 for the selective detection of YCl 3 up to 1.67 × 10 −5 mol L −1 in water. Additionally, a regenerative sensor layer of S-layer proteins on a thin gold film was developed for the detection of 1 × 10 −4 mol L −1 YCl 3 in water by surface plasmon resonance (SPR) spectroscopy.
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