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Grunewald, Germany

Mykhaylyk O.,TU Munich | Sobisch T.,LUM GmbH | Almstatter I.,TU Munich | Sanchez-Antequera Y.,TU Munich | And 8 more authors.
Pharmaceutical Research | Year: 2012

Purpose: To optimize silica-iron oxide magnetic nanoparticles with surface phosphonate groups decorated with 25-kD branched polyethylenimine (PEI) for gene delivery. Methods: Surface composition, charge, colloidal stabilities, associations with adenovirus, magneto-tranduction efficiencies, cell internalizations, in vitro toxicities and MRI relaxivities were tested for the particles decorated with varying amounts of PEI. Results: Moderate PEI-decoration of MNPs results in charge reversal and destabilization. Analysis of space and time resolved concentration changes during centrifugation clearly revealed that at >5% PEI loading flocculation gradually decreases and sufficient stabilization is achieved at >10%. The association with adenovirus occurred efficiently at levels over 5% PEI, resulting in the complexes stable in 50% FCS at a PEI-to-iron w/w ratio of ≥7%; the maximum magneto-transduction efficiency was achieved at 9-12%PEI. Primary silica iron oxide nanoparticles and those with 11.5% PEI demonstrated excellent r2* relaxivity values (>600 s-1(mM Fe)-1) for the free and cell-internalized particles. Conclusions: Surface decoration of the silica-iron oxide nanoparticles with a PEI-to-iron w/w ratio of 10-12% yields stable aqueous suspensions, allows for efficient viral gene delivery and labeled cell detection by MRI. © Springer Science+Business Media, LLC 2012.

Sobisch T.,LUM GmbH | Lerche D.,LUM GmbH | Buske N.,Magnetic Fluids
AIP Conference Proceedings | Year: 2010

Carefully designed colloidal properties are the prerequisite for successful diagnostic and therapeutic applications of magnetic fluids (MF). A high degree of dispersion (small particle size, absence of agglomeration) and stability is required. Multisample analytical centrifugation with high resolution photometric detection was applied to characterize the quality of a range of differently stabilized MF's. Comparison of the 'fingerprints' gives a fast overview over differences in MF quality (quality of particle stabilization against aggregation, separation stability). Sedimentation kinetics and the distribution of sedimentation velocity allow for a more detailed quantitative comparison and ranking between different products and batches. Even without any material properties well dispersed samples with narrow distribution can be discriminated from samples with broader distribution and oversized particles (agglomeration). © 2010 American Institute of Physics.

Lerche D.,LUM GmbH | Sobisch T.,LUM GmbH
Journal of Dispersion Science and Technology | Year: 2011

Formulation of products as well as process and quality control is in need of fast and efficient measurement techniques of the state of dispersion products. We review the basics of experimental techniques of stability assessment of suspensions and emulsions, procedures of accelerated stability testing, and discuss the relationship between results of "accelerated" tests and the outcome under normal conditions of storage and usage (shelf life). Experimental results of the accelerated formulation testing are given with the focus on optical methods measuring stability based on space and time resolved changes of the volume concentration within the entire sample (STEP-Technology). In particular, acceleration of stability assessment acceleration by inclination and analytical centri-fugation is demonstrated for diverse types of formulations. If the rate limiting step of destabilization is not sedimentation or creaming a combination with other established aging tests (temperature storage, freeze-thaw-cycles, physicochemical conditions, etc.) is suggested to reduce evaluation time. © Taylor & Francis Group, LLC.

KOchler S.,LUM GmbH | Sobisch T.,LUM GmbH | Detloff T.,LUM GmbH | Lerche D.,LUM GmbH
CFI Ceramic Forum International | Year: 2011

Modern high performance ceramics, such as dental or artificial bone materials, tiles and technical ceramics are often based on complex suspensions. Composition and pre-processing of the suspension are essential for a consistent high quality of the final product. The evaluation of the sedimentation behaviour of dispersed particles delivers important information on the properties of ceramic dispersions, including separation stability and particle interactions. This paper introduces STEP-Technology®, combined with multisam-ple analytical centrifugation, as a technique to evaluate and quantify directly dispersion characteristics for ceramic suspensions in original concentration. Shear dependent sedimentation rate, consolidation and packing behaviour are directly analyzed. The particle size distribution can be obtained with high resolution. Application studies on kaolin, silicon carbide and silica dis-persions show the high potential of this method.

Mykhaylyk O.,TU Munich | Lerche D.,LUM GmbH | Vlaskou D.,TU Munich | Schoemig V.,TU Munich | And 6 more authors.
IEEE Magnetics Letters | Year: 2015

Magnetophoretic velocity of magnetic nano-objects for biomedical applications was characterized by measuring space-and time-resolved extinction profiles (STEP-Technology) using a customized LUMiReader device equipped with a set of permanent magnets (STEP-MAG). The resulting magnetic fields and gradients in a sample volume enable the operator to choose measurement conditions for magnetic micro-and nanoparticles and their assemblies. The dependence of magnetophoretic velocity on concentration and optical wavelengths indicated assembly of the nano-objects upon magnetophoresis. The method has potential applications in biomedicine to develop advanced materials and protocols for cell separation, tissue engineering, and drug/nucleic acid targeting. © 2015 IEEE.

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