Multifunctional nanoparticles have attracted a lot of attention since they can combine interesting properties like magnetism, fluorescence or plasmonic effects. As a core material, iron oxide nanoparticles have been the subject of intensive research. These cost-effective and non-toxic particles are used nowadays in many applications. We developed a heterobifunctional PEG ligand that can be used to introduce functional groups (carboxylic acids) onto the surface of the NP. Via click chemistry, a siloxane functionality was added to this ligand, for a subsequent covalent ligand exchange reaction. The functionalized nanoparticles have an excellent colloidal stability in complex environments like buffers and serum or plasma. Antibodies were coupled to the introduced carboxylic acids and these NP-antibody bioconjugates were brought into contact with Legionella bacteria for magnetic separation experiments.
Tumor necrosis factor (TNF)-alpha is a pleiotropic cytokine up-regulated in inflammatory bowel disease, rheumatoid arthritis and psoriasis. The introduction of anti-TNF drugs such as infliximab has revolutionized the treatment of these diseases. Recently, therapeutic drug monitoring (TDM) of infliximab has been introduced in clinical decision making to increase cost-efficiency. Nowadays, TDM is performed using radio-immunoassays, homogeneous mobility shift assays or ELISA. Unfortunately, these assays do not allow for insitu treatment optimization, because of the required sample transportation to centralized laboratories and the subsequent assay execution time. In this perspective, we evaluated the potential of fiber optic-surface plasmon resonance (FO-SPR). To achieve this goal, a panel of 55 monoclonal anti-infliximab antibodies (MA-IFX) was developed and characterized in-house, leading to the identification of nine different clusters. Based on this high diversity, 22 antibody pairs were selected and tested for their reactivity towards IFX, using one MA-IFX as capture and one MA-IFX for detection, in a sandwich type ELISA and FO-SPR. This study showed that the reactivity towards IFX of each antibody pair in ELISA is highly similar to its reactivity on FO-SPR, indicating that antibody pairs are easily transferable between both platforms. Given the fact that FO-SPR shows the potential for miniaturization and fast assay time, it can be considered a highly promising platform for on-site infliximab monitoring.
The development of highly specific markers for fluorescent microscopy has become a very popular research topic.
Organic fluorophores have several drawbacks, such as photobleaching and autofluorescence. Therefore increasing
interest in inorganic nanoparticles has been observed because of their unseen photostability, chemical robustness and
straightforward synthesis. The surface of iron oxide nanoparticles was coated with trialkoxy silanes, which introduced
functional groups for possible subsequent coupling reactions. An additional gold layer was added to the surface of the
particle to show the enhanced contrast improvement. The nanoparticles were imaged by an optical microscope, in dark
field mode, on a glass substrate and inside microorganisms. This proved that the reported method could have great
potential as a labelling technique, since it combines the non-photobleaching, photostable nanoparticles with a
straightforward and rapid imaging technique.
The performance of magnetic-field sensors and optical isolators is largely determined by the efficiency of the active
materials. This efficiency could be dramatically increased by integrating Faraday materials in photonic crystals. For this
purpose, monodisperse nanospheres were self-assembled into a colloidal photonic crystal and magnetic functionality was
introduced by dipping the photonic crystal in a suspension containing superparamagnetic nanoparticles. Reflection and
absorbance measurements of these magneto-photonic crystals revealed clear relationships between the time spent in
suspension and the position and strength of the photonic band gap. When additional magnetic material was introduced,
the band gap was red shifted and the strength of the band gap was decreased. Using Bragg's law and the Maxwell-Garnet
approximation for effective media, the filling fraction of the magneto-photonic crystals was calculated from the observed
red shift.
While superparamagnetic nanoparticles did confer magneto-optical properties to the photonic crystal, they also increased
the absorption, which can be detrimental as the Faraday effect is measured in transmission. Therefore a trade-off exists in
the optical regime between the amount of Faraday rotation and the absorption. By carefully controlling the filling
fraction, this trade-off was investigated and optimized for photonic crystals with different band gaps. Both polystyrene
and silica photonic crystals were filled with superparamagnetic nanoparticles. In case of the polystyrene photonic
crystals, it was found that the maximum achievable filling fraction was influenced by the size of the polystyrene
nanospheres. Smaller polystyrene nanospheres gave rise to smaller pore diameters and a faster onset of pore blocking
when filled with superparamagnetic nanoparticles. As a result, the maximum achievable filling fraction was also lower.
Pore blocking was found to be negligible in silica photonic crystals. Together with a higher mechanical strength, this
makes silica photonic crystals more suited for the fabrication of colloidal magneto-photonic crystals.
In this paper, a nanoscale engineering approach is described to carefully control the filling fraction of magneto-photonic
crystals. This allows fine-tuning the absorption and the position and strength of the photonic band gap. By tailoring the
properties of magneto-photonic crystals, the means for application-specific designs and a better description of Faraday
effects in 3D magneto-photonic crystals are provided.
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