Biological synthesis of iron nanoparticles using hydrolysates from a waste-based biorefinery.

The purpose of this work was to produce iron nanoparticles (Fe-NP) by microbial pathway from anaerobic bacteria grown in anaerobic fluidized bed reactors (AnFBRs) that constitute a new stage of a waste-based biorefinery. Bioparticles from biological fluidized bed reactors from a biorefinery of organic fraction of municipal solid wastes (that produces hydrolysates rich in reducing sugars) were nanodecorated (embedded nanobioparticle or nanodecorated bioparticle, ENBP) by biological reduction of iron salts. Factors "origin of bioparticles" (either from hydrogenogenic or methanogenic fluidized bed reactor) and "type of iron precursor salt" (iron chloride or iron citrate) were explored. SEM and high-resolution transmission electron microscopy (HRTEM) showed amorphous distribution of nanoparticles (NP) on the bioparticles surface, although small structures that are nanoparticle-like could be seen in the SEM micrographs. Some agglomeration of NPs was confirmed by DLS. Average NP size was lower in general for NP in ENBP-M than ENBP-H according to HRTEM. The factors did not have a significant influence on the specific surface area of NPs, which was high and in the range 490 to 650 m2 g-1. Analysis by EDS displayed consistent iron concentration 60-65% iron in nanoparticles present in ENBP-M (bioparticles previously grown in methanogenic bioreactor), whereas the iron concentration in NPs present in ENBP-H (bioparticles previously grown in hydrogenogenic bioreactor) was more variable in a range from 8.5 to 62%, depending on the iron salt. X-ray diffraction patterns showed the typical peaks for magnetite at 35° (3 1 1), 43° (4 0 0), and 62° (4 0 0); moreover, siderite diffraction pattern was found at 26° (0 1 2), 38° (1 1 0), and 42° (1 1 3). Results of infrared analysis of ENBP in our work were congruent with presence of magnetite and occasionally siderite determined by XRD analysis as well as presence of both Fe+2 and F+3 (and selected satellite signal peaks) observed by XPS. Our results on the ENBPs hold promise for water treatment, since iron NPs are commonly used in wastewater technologies that treat a wide variety of pollutants. Finally, the biological production of ENBP coupled to a biorefinery could become an environmentally friendly platform for nanomaterial biosynthesis as well as an additional source of revenues for a waste-based biorefinery.

Greater osteoblast densities due to the addition of amphiphilic peptide nanoparticles to nano hydroxyapatite coatings.

BACKGROUND: In vitro and in vivo studies have shown that metallic implants coated with nano hydroxyapatite (HA) reduce the time needed for complete osseointegration compared to metallic implants coated with conventional or micron-sized HA. Moreover, due to their biologically inspired nanometer dimensions, amphiphilic peptide nanoparticles (APNPs) can also promote osteoblast attachment and enhance other cell functions if used as a coating material. Coatings made of HA and APNPs could improve osteoblast functions, but have never been tested. PURPOSE: The objective of this study was to prepare coatings of nanocrystalline HA and APNPs on poly(2-hydroxyethyl methacrylate) (pHEMA) coatings in order to improve osteoblast (bone-forming cells) adhesion and cell density. METHODS: HA was synthesized by a wet chemical process. Coatings were synthesized with different conditions and components. RESULTS: X-ray diffraction infrared spectroscopy, transmission electron microscopy, and electron diffraction showed that nanocrystalline HA was synthesized with an expected nano size and shape distribution but with low impurities. pHEMA hydrogels with HA and APNPs increased osteoblast densities after 3 days compared to controls. CONCLUSION: Since cell proliferation is a prerequisite function for bone formation, these results imply that the current materials should be tested for a wide range of orthopedic applications.