silicon and resazurin

The up-regulation of L-lactate dehydrogenase (LDH), an intracellular enzyme present in most of all body tissues, is indicative of several pathological conditions and cellular death. Herein, we demonstrate LDH detection using porous silicon (pSi) microcavities as a luminescence-enhancing optical biosensing platform. Non-fluorescent resazurin was covalently attached onto the pSi surface via thermal hydrocarbonisation, thermal hydrosylilation and acylation. Each surface modification step was confirmed by means of FTIR and the optical shifts of the resonance wavelength of the microcavity. Thermal hydrocarbonisation also afforded excellent surface stability, ensuring that the resazurin was not reduced on the pSi surface. Using a pSi microcavity biosensor, the fluorescence signal upon detection of LDH was amplified by 10 and 5-fold compared to that of a single layer and a detuned microcavity, respectively, giving a limit of detection of 0.08 U/ml. The biosensor showed a linear response between 0.16 and 6.5 U/ml, covering the concentration range of LDH in normal as well as damaged tissues. The biosensor was selective for LDH and did not produce a signal upon incubation with another NAD-dependant enzyme L-glutamic dehydrogenase. The use of the pSi microcavity as a sensing platform reduced reagent usage by 30% and analysis time threefold compared to the standard LDH assay in solution.

Topics: Biosensing Techniques; Equipment Design; Equipment Failure Analysis; L-Lactate Dehydrogenase; Miniaturization; Oxazines; Porosity; Reproducibility of Results; Sensitivity and Specificity; Silicon; Spectrometry, Fluorescence; Surface Plasmon Resonance; Xanthenes

Topics: Biosensing Techniques; Catalysis; Cell Adhesion; Cell Line; Cell Movement; Cells, Cultured; Drug Carriers; Electrophoresis, Agar Gel; Humans; Metal Nanoparticles; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Nanowires; Oxazines; Silicon; Xanthenes

The use of silicon-substituted hydroxyapatite (Si-HA) as a biomaterial has been reported recently. In vivo testing has shown that Si-HA promotes early bonding of the bone/implant interface. In order to extend its usage to major load-bearing applications such as artificial hip replacement implants, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of the biocompatibility of magnetron co-sputtered silicon-containing hydroxyapatite (Si-HA) coatings on a metallic substrate. Magnetron co-sputtered Si-HA films of thickness 600 nm with a Si content of approximately 0.8 wt% were produced on titanium substrates. X-ray diffraction analysis showed that the as-deposited Si-HA films were either amorphous or made up of very small crystals. The crystallinity of Si-HA films was increased after post-deposition heat treatment at 700 degrees C for 3 h, and the principal peaks were attributable to HA. The formation of nano-scale silicon-calcium phosphate precipitates was noted on the heat-treated films. In vitro cell culture has demonstrated that human osteoblast-like cells attached and grew well on all films, with the highest cell growth and signs of mineralisation observed on the heat-treated Si-HA films. In addition, many focal contacts were produced on the films and the cells had well-defined actin cytoskeletal organisation. This work shows that as-deposited and heat-treated Si-HA films have excellent bioactivity and are good candidates when rapid bone apposition is required. Furthermore, heat-treated Si-HA films have improved biostability compared to as-deposited films under physiological conditions.

Topics: Actins; Calcium Phosphates; Cell Proliferation; Cells, Cultured; Coated Materials, Biocompatible; Cytoskeleton; Durapatite; Focal Adhesions; Hot Temperature; Humans; Hydroxyapatites; In Vitro Techniques; Indicators and Reagents; Materials Testing; Microscopy, Confocal; Microscopy, Electron; Microscopy, Electron, Scanning; Microscopy, Fluorescence; Osteoblasts; Oxazines; Silicon; Spectroscopy, Fourier Transform Infrared; Surface Properties; Time Factors; Vinculin; X-Ray Diffraction; Xanthenes