Effect of molecular Stokes shift on polariton dynamics.

When the enhanced electromagnetic field of a confined light mode interacts with photoactive molecules, the system can be driven into the regime of strong coupling, where new hybrid light-matter states, polaritons, are formed. Polaritons, manifested by the Rabi split in the dispersion, have shown potential for controlling the chemistry of the coupled molecules. Here, we show by angle-resolved steady-state experiments accompanied by multi-scale molecular dynamics simulations that the molecular Stokes shift plays a significant role in the relaxation of polaritons formed by organic molecules embedded in a polymer matrix within metallic Fabry-Pérot cavities. Our results suggest that in the case of Rhodamine 6G, a dye with a significant Stokes shift, excitation of the upper polariton leads to a rapid localization of the energy into the fluorescing state of one of the molecules, from where the energy scatters into the lower polariton (radiative pumping), which then emits. In contrast, for excitonic J-aggregates with a negligible Stokes shift, the fluorescing state does not provide an efficient relaxation gateway. Instead, the relaxation is mediated by exchanging energy quanta matching the energy gap between the dark states and lower polariton into vibrational modes (vibrationally assisted scattering). To understand better how the fluorescing state of a molecule that is not strongly coupled to the cavity can transfer its excitation energy to the lower polariton in the radiative pumping mechanism, we performed multi-scale molecular dynamics simulations. The results of these simulations suggest that non-adiabatic couplings between uncoupled molecules and the polaritons are the driving force for this energy transfer process.

Effect of S53P4 bone substitute on staphylococcal adhesion and biofilm formation on other implant materials in normal and hypoxic conditions.

To study the effect of bioactive glass bone substitute granules (S53P4) on bacterial adhesion and biofilm formation on other simultaneously used implant materials and the role of the hypoxic conditions to the adhesion. Bacterial and biofilm formation were studied on materials used both in middle ear prostheses and in fracture fixtures (titanium, polytetrafluoroethylene, polydimethylsiloxane and bioactive glass plates) in the presence or absence of S53P4 granules. The experiments were done either in normal atmosphere or in hypoxia simulating atmospheric conditions of middle ear, mastoid cavity and sinuses. We used two collection strains of Staphylococcus aureus and Staphylococcus epidermidis. In the presence of bioglass and hypoxic conditions the adhesion of the planktonic bacterial cells was decreased for most of the materials. The biofilm formation was decreased for S. epidermidis on titanium and polydimethylsiloxane in both atmospheric conditions and on bioglass plates in normoxia. For S. aureus the biofilm formation was decreased on bioglass plates and polytetrafluoroethylene in normoxia. Hypoxia produces a decrease in the biofilm formation only for S. aureus on polytetrafluoroethylene and for S. epidermidis on bioglass plates. However, in none of the cases bioactive glass increased the bacterial or biofilm adhesion. The presence of bioglass in normoxic and hypoxic conditions prevents the bacterial and biofilm adhesion on surfaces of several typical prosthesis materials in vitro. This may lead to diminishing postoperative infections, however, further in vivo studies are needed.

Effects of S53P4 bioactive glass on osteoblastic cell and biomaterial surface interaction.

To study the effect of bioactive glass bone substitute granules (S53P4) and hypoxic atmospheric conditions on human osteoblastic cell adhesion on different biomaterials. Cellular adhesion and cytoskeletal organization were studied on titanium, polytetrafluoroethylene, polydimethylsiloxane and S53P4 plates in the presence or absence of S53P4 granules. Cells used were human osteoblast-like SaOS-2 cells. The experiments were done either in normal atmospheric conditions or in hypoxia which simulates conditions prevailing in chronically infected bone or bone cavities. Vinculin-containing focal adhesions, organization of actin cytoskeleton and nuclear staining of cells on biomaterial surfaces were studied at 4.5 h, 2 and 4 days. In normoxic conditions S53P4 granules alkalinized the cell culture medium but cellular adhesion and cytoskeletal organization were usually not affected by their presence. Hypoxic conditions associated with lower pH and impaired cellular adhesion, vinculin-containing focal adhesion formation and rearrangement of the actin filaments to actin cytoskeleton. On most materials studied in hypoxic conditions, however, S53P4 granules prevented this impairment of cellular adhesion and cytoskeletal reorganization. The S53P4 granules promote the adhesion of SaOS-2 cells to various biomaterial surfaces especially in hypoxic conditions, in which S53P4 granules increase pH. The presence of S53P4 granules may protect biomaterial surface from bacterial colonization and promote osteointegration of implants used together with S53P4 granules for fixation and weight bearing.

Expression of ADAM9 (meltrin-gamma) around aseptically loosened total hip replacement implants.

OBJECTIVE: To investigate the involvement of a disintegrin and the metalloproteinase ADAM9 (meltrin-gamma) in the formation of multinuclear giant cells and osteoclasts in aseptic loosening of hip replacement implants. METHODS: We used in situ hybridization, immunohistochemical staining and western blotting of interface membrane surrounding loosened hip implants, macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor kappaB ligand (RANKL) costimulation and polymethyl methacrylate (PMMA) particle stimulation of human monocytes followed by immunofluorescence staining and flow cytometric analysis. RESULTS: Morphometric analysis revealed that the ADAM9+ area in the revision total hip replacement (THR) interface was larger than in primary THR samples (37.6+/-5.1 vs 5.2+/-0.8%, P=0.002). Double immunofluorescence staining showed that CD68+ interface tissue macrophages and multinuclear giant cells were ADAM9+. ADAM9 mRNA containing mononuclear and multinuclear cells was often seen in a close spatial relationship with other ADAM9+ cells. Western blotting disclosed a 50 kDa ADAM9 band in tissue extracts. Upon M-CSF and RANKL costimulation of human monocytes, the ADAM9 staining pattern changed over time and ADAM9+ cells formed bi- and multinuclear cells. Flow cytometry disclosed that cells of the monocyte/macrophage lineage changed from ADAM9-negative cells into strongly positive cells during a 3-day culture. CONCLUSION: ADAM9 is expressed in interface tissues around aseptically loosened THR implants. ADAM9 may play a role as a fusion molecule in the formation of multinuclear giant cells and osteoclasts from mononuclear precursors in diseases characterized by bone tissue destruction.

Poly(dimethylsiloxane) electrospray devices fabricated with diamond-like carbon-poly(dimethylsiloxane) coated SU-8 masters.

This study presents coupling of a poly(dimethylsiloxane) (PDMS) micro-chip with electrospray ionization-mass spectrometry (ESI-MS). Stable electrospray is generated directly from a PDMS micro-channel without pressure assistance. Hydrophobic PDMS aids the formation of a small Taylor cone in the ESI process and facilitates straightforward and low-cost batch production of the ESI-MS chips. PDMS chips were replicated with masters fabricated from SU-8 negative photoresist. A novel coating, an amorphous diamond-like carbon-poly(dimethylsiloxane) hybrid, deposited on the masters by the filtered pulsed plasma arc discharge technique, improved significantly the lifetime of the masters in PDMS replications. PDMS chip fabrication conditions were observed to affect the amount of background peaks in the MS spectra. With an optimized fabrication process (PDMS curing agent/silicone elastomer base ratio of 1/8 (w/w), curing at 70 degree C for 48 h) low background spectra were recorded for the analytes. The performance of PDMS devices was examined in the ESI-MS analysis of some pharmaceutical compounds and amino acids.