The Department focuses on development of various particles of regular shape and size as multimodal imaging agents or solid reaction supports. This includes surface-engineered light-upconverting and magnetic nano- and microspheres containing a ligand (e.g., for targeting and capture of circulating tumor cells), markers of Alzheimer’s and Parkinson’s disease, proteins, enzymes; optionally, the particles are suitable for separation of toxic metal ions or other molecules from waste water or complex biological milieu, such as blood, plasma or cerebrospinal fluid. As an example, the magnetic particles are becoming an integral part of lab-on-chip medical devices for in vitro molecular diagnostics. Both light-upconverting and magnetic cores, such as lanthanide fluorides or iron oxides, are encapsulated within the polymer shell to avoid aggregation, provide biocompatibility, suppress non-specific interactions, and introduce required functionalities.
Monodisperse lanthanide-based nanocrystals are gaining a considerable attention in various biological applications due to their unique luminescent properties, which can be easily controlled by varying the lanthanide ion dopants and their concentration. Light-upconverting nanoparticles (UCNPs) prepared by thermal decomposition of lanthanide organic precursors are distinguished by upconversion of low-energy NIR irradiation into high-energy visible or ultraviolet light via anti-Stokes emission, which allows for deep tissue penetration of NIR radiation due to reduced light absorption in the tissue, low autofluorescence and photon scattering. Compared to conventional fluorescence nanomaterials (organic dyes, metal complexes, etc.), UCNPs have additional advantages, such as high chemical stability, narrow emission lines, no blinking, and no bleaching. UCNPs have thus a great potential in a variety of applications, ranging from photovoltaics, photocatalysis, security systems, and display technology to in vitro and in vivo tissue bioimaging, image-guided surgery, background-free biosensors, light-triggered drug and gene delivery, optogenetics, or NIR-triggered photodynamic therapy of tumours. Recent trend pursued in our Department involves multimodal imaging (MRI, fluorescence, SPECT/CT and/or PET) of cells and tissues in one system. However, to be applicable, the particles have to be surface-modified with silica derivatives, peptides or various polymers, preferably containing bisphosphonate groups with strong affinity to UCNP surface.
Monodisperse silica-modified hexagonal lanthanide-based upconverting nanoparticles exhibit fluorescence at 480 nm in mRoGFP HeLa cells.
Photoluminescence of upconverting nanoparticles and SPECT/CT image of a mouse after intravenous injection of the 125I-labeled NaYF4:Yb3+/Er3+@PEG nanoparticles.
Schematic view of uptake of RGDS- and TAT-conjugated upconverting NaYF4:Yb3+/Er3+@SiO2 nanoparticles in human epithelioid cervix carcinoma cells.
Phthalocyanine-conjugated upconverting NaYF4:Yb3+/Er3+@SiO2 nanospheres for NIR-triggered photodynamic therapy in a tumor mouse model.
Magnetic colloids are distinct by their unique magnetic properties, large surface-to-volume ratio, small size (in nanometers), and ability to function at the cellular level. These characteristics make them appropriate candidates for medical applications, such as contrast agents for magnetic resonance imaging, magnetically guided carriers for drug delivery, or heat mediators for hyperthermia. The magnetically labeled cells can be transplanted into the damaged tissues enabling non-invasive and long-term monitoring of cell introduction, migration, proliferation and differentiation. Magnetic nanomaterials, in particular, maghemite (γ-Fe2O3) and magnetite (Fe3O4), prepared in our Department by thermal decomposition of organic precursors or coprecipitation of metal salts with a base, exhibit low toxicity, biocompatibility and can be easily modified with polymers (e.g., poly(L-lysine) or ATRP/RAFT-fabricated macromolecules), drugs (doxorubicin) and/or targeting peptides, and imaging ligands. The nanoparticles are easily functionalized also by various polymers containing reactive functional groups (amino, carboxyl, vinyl and ethynyl), chelates, etc. In the Department, we focus on the synthesis of antibacterial, antioxidant, and/or cancerostatic nanoparticles.
Schematic preparation of antibacterial Fe3O4@SiO2-Ag nanoparticles.
Schematic view of hydrogen peroxide and superoxide radical scavenging due to a Ce3+/Ce4+ redox shift on antioxidant γ-Fe2O3/CeOx@PEG nanoparticles.
Doxorubicin‐conjugated cancerostatic iron oxide nanoparticles.
Polymer particles (e.g., from poly(glycidyl or 2-hydroxyethyl methacrylate), cellulose) are obtained in the Department by a range of methods including sol-gel transition, suspension, emulsion, miniemulsion, seeded or multistep-swelling polymerization. Advantage of the latter technique is that it produces uniform polymer particles (in micrometers) with the same physicochemical and biological properties and high reproducibility of experiments. The method is suitable for preparation of efficient chromatographic packings and/or magnetic polymer microspheres containing various functional groups, such as NH2, COOH, SH, tosyl or RGDS peptide. The particles are applicable in bioassays, enabling simple manipulation by a magnet during washing and reagent exchange. Moreover, it is feasible to adapt usage of magnetic particles in automated protocols. Coating of the microspheres with poly(ethylene glycol), betaines, or silica derivatives suppresses undesirable nonspecific protein adsorption. The microspheres are used also in microchips for diagnostics of circulating tumor cells, in proximity ligation assays and rolling circle amplifications, for diagnosis of neurodegenerative disorders and autoimmune diseases, capture of DNAs, separation of biomolecules, control of food quality, etc.
Schematic view of immobilization of p46/Myo1C antigen on a magnetic poly(glycidyl methacrylate)-NH2 microsphere and capture of anti-p46/Myo1C auto-antibodies from blood serum.
Modification of magnetic poly(glycidyl methacrylate)-NH2 microspheres with dendrimer, 4-pentynoic acid, and click reaction with 125I-N3-RGDS peptide.
Ephesia system principle. (a) Design of the chip, (b) the bottom layer of the chip: anchoring points, (c) self-assembly of magnetic beads under the magnetic field, (d) immunomagnetic-based capture of cancer cells.
Hydrogel Scaffolds for Tissue Engineering
Synthetic hydrogels are water‐swollen networks consisting of hydrophilic polymers, e.g., poly(ethylene glycol), poly(vinyl alcohol), poly[N‐(2‐hydroxypropyl) methacrylamide], and poly(2‐hydroxyethyl methacrylate) (PHEMA), that make them suitable for tissue engineering applications. There, the hydrogels must interact with cells to support their adhesion, proliferation, migration, and differentiation. Moreover, the hydrogel surface has to be modified, e.g., with adhesive peptides to mimic a tissue‐specific cell environment. 3-D superporous hydrogel scaffolds are promising for cultivation of stem and neural cells in tissue engineering and regenerative medicine, such as healing of damaged spinal cord.
(a) Ammonium oxalate and (b) sodium chloride crystals used as a porogen for preparation of PHEMA scaffolds with oriented porosity and superporosity, respectively.
(a) PHEMA and (b) alginate hydrogel scaffolds with oriented porosity.
Preparation of reductively degradable PHEMA hydrogels.
- University of Regensburg, Germany
- Institute of Condensed Matter Chemistry and Technologies for Energy, National Research Council (CNR), Padova, Italy
- Chang Gung University, Taoyuan, Taiwan
- Wroclaw University of Science and Technology, Poland
- Institute of Experimental Medicine, Czech Academy of Sciences, Prague
- Institute for Clinical and Experimental Medicine, Prague
- Masaryk University, Brno
- Center for Advanced Preclinical Imaging, Charles University, Prague
- Institute of Physiology, Czech Academy of Sciences
- Grant Agency of the Czech Republic, No. 19-00676S, 20-07015S, 20-02177J, 21-04420S
- Academy of Science of the Czech Republic, CNR-19-16
- Ministry of Education, Youth and Sports of the Czech Republic, INTER-ACTION LTAB19011