Magnetische multifunktionale Nanopartikel für die Implantat-dirigierte Wirkstoffanlieferung

The targeted treatment of implant-associated infections and organ diseases represents great challenges for physicians concerning the demographic change. For systemic treatment, high drug levels are often necessary to achieve an adequate concentration at the target location, which in turn increases the risk of undesirable side effects and resistance to antimicrobial drugs. The focus of this dissertation is therefore the development, production and characterization of different magnetic core-shell particle systems as drug carriers for targeted, effective treatment. Implant-directed magnetic drug targeting (ID-MDT) offers a promising approach for the selective treatment of implant-associated infections. In this concept, magnetic nanoparticles serve as drug carriers with the combined utilization of an external magnetic field and magnetizable implants. In the first part of this work, magnetic nanoporous silica nanoparticles (MNPSNPs) with superparamagnetic cores and a multifunctional highly porous silica shell as drug carriers are presented. Here, the focus is on particle and pore size adjustment as well as a specific modification with organic fluorophores, polyethylene glycol (PEG), periodic mesoporous organosilica (PMO) and the characterization of the associated material properties. The second part describes the application of the presented multifunctional particles as drug release systems. Using the antibiotic drug enrofloxacin, the influence of different modifications on the release profile is shown. In the third and final part of this thesis, magnetic silica particles (MSPs) serve as drug carriers for another variant of magnetic drug targeting (MDT). Here, after particle uptake by macrophages, a controlled release of drugs for the targeted treatment of organ diseases using hyperthermia is possible.Die zielgerichtete Behandlung von Implantat-assoziierten Infektionen und Organerkrankungen stellt die Mediziner in Anbetracht des demographischen Wandels vor große Herausforderungen. So sind für eine systemische Behandlung häufig hohe Wirkspiegel für das Erreichen einer adäquaten Konzentration am Zielort notwendig, welche wiederum das Risiko von unerwünschten Nebenwirkungen und zunehmenden Resistenzen gegenüber antimikrobiellen Wirkstoffen erhöhen. Der Fokus der vorliegenden Dissertation liegt daher in der Entwicklung, Herstellung und Charakterisierung von unterschiedlichen magnetischen Kern-Schale-Partikelsystemen als Wirkstoffträger für eine zielgerichtete effektive Behandlung. Das Implantat-dirigierte magnetische Wirkstoff-Targeting (ID-MDT) bietet hier einen vielversprechenden Ansatz zur selektiven Behandlung von Implantat-assoziierten Infektionen. Bei diesem Prinzip dienen magnetische Nanopartikel als Wirkstoffträger unter kombinierten Einsatz eines externen angelegten magnetischen Feldes und magnetisierbaren Implantaten. Im ersten Teil dieser Arbeit werden magnetische nanoporöse Silica-Nanopartikel (MNPSNPs) mit superparamagnetischen Kernen und einer multifunktionalen hochporösen Silica-Schale als Wirkstoffträger vorgestellt. Dabei liegt der Schwerpunkt in der Partikel- und Porengrößeneinstellung sowie der gezielten Funktionalisierung mit organischen Fluorophoren, Polyethylenglycol (PEG), periodisch mesoporösem Organosilica (PMO) sowie der Charakterisierung der damit verbundenen Materialeigenschaften. Der zweite Teil beschreibt den Einsatz der vorgestellten multifunktionalen Partikel als Wirkstofffreisetzungssysteme. Anhand des Antibiotikums Enrofloxacin wird dabei der Einfluss unterschiedlicher Modifizierungen auf das Freisetzungsprofil gezeigt. Im dritten und letzten Teil dieser Dissertation dienen magnetische Silica-Partikel (MSPs) als Wirkstoffträger für eine weitere Variante des magnetischen Wirkstoff-Targetings (MDT). Hierbei ist nach einer Partikelaufnahme durch Makrophagen unter Einsatz von Hyperthermie eine gesteuerte Freisetzung von Wirkstoffen für die zielgerichtete Behandlung von Organerkrankungen möglich

Nanoporous hybrid core–shell nanoparticles for sequential release

In this article, a new type of core–shell nanoparticle is introduced. In contrast to most reported core–shell systems, the particles presented here consist of a porous core as well as a porous shell using only non-metal materials. The core–shell nanoparticles were successfully synthesized using nanoporous silica nanoparticles (NPSNPs) as the starting material, which were coated with nanoporous phenylene-bridged organosilica, resulting in a total particle diameter of about 80 nm. The combination of a hydrophilic nanoporous silica core and a more hydrophobic nanoporous organosilica shell provides regions of different chemical character and slightly different pore sizes within one particle. These different properties combined in one particle enable the selective adsorption of guest molecules at different parts of the particle depending on the molecular charge and polarity. On the other hand, the core–shell make-up of the particles provides a sequential release of guest molecules adsorbed at different parts of the nanoparticles. As a proof of concept, loading and release experiments with dyes were performed using non polar fluorescein and polar and charged methylene blue as model guest molecules. Non polar fluorescein is mostly adsorbed on the hydrophobic organosilica shell and therefore quickly released whereas the polar methylene blue, accumulated in the hydrophilic silica core, is only released subsequently. This occurs in small doses for an extended time corresponding to a sustained release over at least one year, controlled by the organosilica shell which acts as a diffusion barrier. An initial experiment with two drugs — non polar ibuprofen and polar and charged procaine hydrochloride — has been carried out as well and shows that the core–shell nanoparticles presented here can also be used for the sequential release of more relevant combinations of molecules

Biodistribution, biocompatibility and targeted accumulation of magnetic nanoporous silica nanoparticles as drug carrier in orthopedics

Background: In orthopedics, the treatment of implant-associated infections represents a high challenge. Especially, potent antibacterial effects at implant surfaces can only be achieved by the use of high doses of antibiotics, and still often fail. Drug-loaded magnetic nanoparticles are very promising for local selective therapy, enabling lower systemic antibiotic doses and reducing adverse side effects. The idea of the following study was the local accumulation of such nanoparticles by an externally applied magnetic field combined with a magnetizable implant. The examination of the biodistribution of the nanoparticles, their effective accumulation at the implant and possible adverse side effects were the focus. In a BALB/c mouse model (n = 50) ferritic steel 1.4521 and Ti90Al6V4 (control) implants were inserted subcutaneously at the hindlimbs. Afterwards, magnetic nanoporous silica nanoparticles (MNPSNPs), modified with rhodamine B isothiocyanate and polyethylene glycol-silane (PEG), were administered intravenously. Directly/1/7/21/42 day(s) after subsequent application of a magnetic field gradient produced by an electromagnet, the nanoparticle biodistribution was evaluated by smear samples, histology and multiphoton microscopy of organs. Additionally, a pathohistological examination was performed. Accumulation on and around implants was evaluated by droplet samples and histology. Results: Clinical and histological examinations showed no MNPSNP-associated changes in mice at all investigated time points. Although PEGylated, MNPSNPs were mainly trapped in lung, liver, and spleen. Over time, they showed two distributional patterns: early significant drops in blood, lung, and kidney and slow decreases in liver and spleen. The accumulation of MNPSNPs on the magnetizable implant and in its area was very low with no significant differences towards the control. Conclusion: Despite massive nanoparticle capture by the mononuclear phagocyte system, no significant pathomorphological alterations were found in affected organs. This shows good biocompatibility of MNPSNPs after intravenous administration. The organ uptake led to insufficient availability of MNPSNPs in the implant region. For that reason, among others, the nanoparticles did not achieve targeted accumulation in the desired way, manifesting future research need. However, with different conditions and dimensions in humans and further modifications of the nanoparticles, this principle should enable reaching magnetizable implant surfaces at any time in any body region for a therapeutic reason. © 2020 The Author(s)

A Low‐Temperature Approach for the Phase‐Pure Synthesis of MIL‐140 Structured Metal–Organic Frameworks

In a systematic investigation, the synthesis of metal–organic frameworks (MOFs) with MIL-140 structure was studied. The precursors of this family of MOFs are the same as for the formation of the well-known UiO-type MOFs although the synthesis temperature for MIL-140 is significantly higher. This study is focused on the formation of Zr-based MIL-140 MOFs with terephthalic acid (H2bdc), biphenyl-4,4′-dicarboxylic acid (H2bpdc), and 4,4′-stilbenedicarboxylic acid (H2sdc) and the introduction of synthesis field diagrams to discover parameters for phase-pure products. In this context, a MIL-140 network with H2sdc as linker molecule is first reported. Additionally, an important aspect is the reduction of the synthesis temperature to make MIL-140 MOFs more accessible even though linkers with a more delicate nature are used. The solvothermal syntheses were conducted in highly concentrated reaction mixtures whereby a targeted synthesis to yield the MIL-140 phase is possible. Furthermore, the effect of the often-used modulator approach is examined for these systems. Finally, the characteristics of the synthesized MOFs are compared with physisorption measurements, thermogravimetric analyses, and scanning electron microscopy

Long-term delivery of brain-derived neurotrophic factor (BDNF) from nanoporous silica nanoparticles improves the survival of spiral ganglion neurons in vitro.

Sensorineural hearing loss (SNHL) can be overcome by electrical stimulation of spiral ganglion neurons (SGNs) via a cochlear implant (CI). Restricted CI performance results from the spatial gap between the SGNs and the electrode, but the efficacy of CI is also limited by the degeneration of SGNs as one consequence of SHNL. In the healthy cochlea, the survival of SGNs is assured by endogenous neurotrophic support. Several applications of exogenous neurotrophic supply have been shown to reduce SGN degeneration in vitro and in vivo. In the present study, nanoporous silica nanoparticles (NPSNPs), with an approximate diameter of <100 nm, were loaded with the brain-derived neurotrophic factor (BDNF) to test their efficacy as long-term delivery system for neurotrophins. The neurotrophic factor was released constantly from the NPSNPs over a release period of 80 days when the surface of the nanoparticles had been modified with amino groups. Cell culture investigations with NIH3T3 fibroblasts attest a good general cytocompatibility of the NPSNPs. In vitro experiments with SGNs indicate a significantly higher survival rate of SGNs in cell cultures that contained BDNF-loaded nanoparticles compared to the control culture with unloaded NPSNPs (p<0.001). Importantly, also the amounts of BDNF released up to a time period of 39 days increased the survival rate of SGNs. Thus, NPSNPs carrying BDNF are suitable for the treatment of inner ear disease and for the protection and the support of SGNs. Their nanoscale nature and the fact that a direct contact of the nanoparticles and the SGNs is not necessary for neuroprotective effects, should allow for the facile preparation of nanocomposites, e.g., with biocompatible polymers, to install coatings on implants for the realization of implant-based growth factor delivery systems

In vitro and in vivo accumulation of magnetic nanoporous silica nanoparticles on implant materials with different magnetic properties

Abstract Background In orthopedic surgery, implant-associated infections are still a major problem. For the improvement of the selective therapy in the infection area, magnetic nanoparticles as drug carriers are promising when used in combination with magnetizable implants and an externally applied magnetic field. These implants principally increase the strength of the magnetic field resulting in an enhanced accumulation of the drug loaded particles in the target area and therewith a reduction of the needed amount and the risk of undesirable side effects. In the present study magnetic nanoporous silica core–shell nanoparticles, modified with fluorophores (fluorescein isothiocyanate/FITC or rhodamine B isothiocyanate/RITC) and poly(ethylene glycol) (PEG), were used in combination with metallic plates of different magnetic properties and with a magnetic field. In vitro and in vivo experiments were performed to investigate particle accumulation and retention and their biocompatibility. Results Spherical magnetic silica core–shell nanoparticles with reproducible superparamagnetic behavior and high porosity were synthesized. Based on in vitro proliferation and viability tests the modification with organic fluorophores and PEG led to highly biocompatible fluorescent particles, and good dispersibility. In a circular tube system martensitic steel 1.4112 showed superior accumulation and retention of the magnetic particles in comparison to ferritic steel 1.4521 and a Ti90Al6V4 control. In vivo tests in a mouse model where the nanoparticles were injected subcutaneously showed the good biocompatibility of the magnetic silica nanoparticles and their accumulation on the surface of a metallic plate, which had been implanted before, and in the surrounding tissue. Conclusion With their superparamagnetic properties and their high porosity, multifunctional magnetic nanoporous silica nanoparticles are ideal candidates as drug carriers. In combination with their good biocompatibility in vitro, they have ideal properties for an implant directed magnetic drug targeting. Missing adverse clinical and histological effects proved the good biocompatibility in vivo. Accumulation and retention of the nanoparticles could be influenced by the magnetic properties of the implanted plates; a remanent martensitic steel plate significantly improved both values in vitro. Therefore, the use of magnetizable implant materials in combination with the magnetic nanoparticles has promising potential for the selective treatment of implant-associated infections

Macrophage entrapped silica coated superparamagnetic iron oxide particles for controlled drug release in a 3D cancer model.

Targeted delivery of drugs is a major challenge in treatment of diverse diseases. Systemically administered drugs demand high doses and are accompanied by poor selectivity and side effects on non-target cells. Here, we introduce a new principle for targeted drug delivery. It is based on macrophages as transporters for nanoparticle-coupled drugs as well as controlled release of drugs by hyperthermia mediated disruption of the cargo cells and simultaneous deliberation of nanoparticle-linked drugs. Hyperthermia is induced by an alternating electromagnetic field (AMF) that induces heat from silica-coated superparamagnetic iron oxide nanoparticles (SPIONs). We show proof-of-principle of controlled release by the simultaneous disruption of the cargo cells and the controlled, AMF induced release of a toxin, which was covalently linked to silica-coated SPIONs via a thermo-sensitive linker. Cells that had not been loaded with SPIONs remain unaffected. Moreover, in a 3D co-culture model we demonstrate specific killing of associated tumour cells when employing a ratio as low as 1:40 (SPION-loaded macrophage: tumour cells). Overall, our results demonstrate that AMF induced drug release from macrophage-entrapped nanoparticles is tightly controlled and may be an attractive novel strategy for targeted drug release

Survival rates of spiral ganglion neurons after a cultivation of two days.

<p>Cells were cultivated in presence of the supernatants from the release experiments of BDNF-loaded amino-modified NPSNPs (NPSNP-NH₂-BDNF) or of amino-modified NPSNPs (NPSNP-NH₂) as control experiment. Values are given as mean ± standard error of the mean (<i>N</i> = 3, <i>n</i> = 3). Statistical assessment was performed using one-way ANOVA with Bonferroni´s multiple comparison test (n.s. = not significant, *p<0.05; **p<0.01; ***p<0.001). Asterisks over the bars indicate the significance of the survival rates of different conditions compared to the medium control (serum-free SGC medium). Asterisks between two bars indicate the significance between the different conditions.</p

BDNF release profile of amino-modified NPSNPs in PBS (0.1% BSA) over 80 days at 37°C.

<p>The left axis represents the cumulative BDNF release with regard to 1 mg of nanoparticles and the right axis shows the cumulative release of BDNF referred to 1 mL release medium.</p

Relative cell viabilities of NIH3T3 fibroblasts in the presence of unmodified and amino-modified nanoparticles in different concentrations determined by the NRU assay after an incubation for four days.

<p>Values are given as mean ± standard error of the mean (<i>n</i> = 3).</p