PD Dr. med. vet. Janin Reifenrath
Specialist in laboratory animal science
PD Dr. rer. nat. Elmar Willbold
Dr. med. vet. Nina Angrisani (Veterinarian)
Hilke Catherina Janßen (Veterinarian)
Diana Strauch (lab technician)
Mattias Reebmann (lab technician)
Merle Marie Kempfert (PhD-student)
Orthopedic implants are routinely used in clinics, e.g. in treatment of bone fractures, malalignment or arthroplasties. Nevertheless, difficulties can occur, like foreign body reactions against the implant, osteolytic processes due to stress shielding effects or implant-associated infections. These and other complications can lead to the necessity of implant removal, which is associated with a high patient burden.
Research focuses: degradable implants and implant-associated infections
The research group deals with two major focuses: „biodegradable und bioactive orthopedic implants“. The first is the development of dissolving („biodegradable“) implant materials to supersede a second surgery for implant removal. The second is the evaluation of new concepts for better tissue ingrowth of materials and prevention of implant infections by testing modified (bioactive) implant surfaces. Additionally, new therapeutic strategies are developed. Key questions of biomechanical stability and biocompatibility are examined in this context. Research goal is the development of optimized orthopedic implants and therewith an increased patient safety and quality of life.
Multiple projects, funded by different funding agencies like German Research Foundation (key project was the collaborative research centre 599 „Sustainable bioresorbable and permanent implants of metallic and ceramic materials“), charitable trusts or economical sponsors resulted in a broad spectrum of established and validated methods for implant research and development with special focus on preclinical testing procedures concerning biocompatibility and functionality.
Used methods in this context are in vitro test systems for the evaluation of degradation kinetics or cell-culture experiments to estimate cytotoxicity in a first step. Necessary stability of implants is tested by biomechanical testing procedures like tensile and bending testing as well as cyclic testing. In the further process of preclinical testing, a variety of different specific animal models are established. For detailed quantitative evaluation, for example of implant degradation or bony integration at different time points after surgery, in vivo and ex vivo imaging like radiology, µ-computed tomography, fluorescence imaging or magnetic resonance imaging is used in cooperation with different partners (e.g. Institute of Laboratory Animal Science, Clinic for Laryngology, Rhinology and Otology, both Hannover Medical School or the Veterinary University of Hannover).
Additionally, a variety of histological methods is available. Besides different stainings including fluorescence microscopy, confocal laser scanning microscopy is used in collaboration with the Research Core Unit for Laser Microscopy of MHH for implant surface examination.
In the research focus of implant-associated infections, prophylactic and therapeutic approaches are tested. As prophylactic approach, surface modifications of implants, e.g. by laser structuring (cooperation with Laser Zentrum Hannover), intend to reduce bacterial load while simultaneously increasing tissue integration in bony environment.
In the research focus of new therapeutic strategies for implant infections, a system called „magnetic drug targeting“ is adapted for implant materials. In this strategy, special magnetisable nanoparticles are loaded with chemotherapeutics and accumulated magnetically at the desired location. The advantage shall be a reduction of undesired side effects of medication and a better effectiveness by accumulation at the implant surface and in the direct implant interface. Especially the possibility for treatment at any desired time point after implantation with adequate drug levels around the implant is a promising option which might avoid removal of infected implants.
Services and collaboration
Determination of degradation rates of degradable materials in vitro
Biomechanical testing of implant materials:
After specific intervals
In cyclic testing systems
Determination of enzyme activity
Preclinical testing of materials in different animal models
Magnetic resonance tomographic examination
Confocal laser scanning examination of implant surfaces
In vivo fluorescence staining and examination of bone parameters
Histological processing and evaluation of hard and soft tissue (paraffin and plastic embedding) including residual implant material
Staining procedures including antibody staining
Microscopic evaluation and documentation by
Transmitted light microscopy
Dark field microscopy
Phase contrast microscopy
Reflectance light microscopy
Semiquantitative evaluation of standardised bone parameter
Histological-electrochemical dissolving of metals
Graded implants (FOR 2180) --- Tendon to bone interfaces (funder DFG)
Implant-directed magnetic drug targeting: antibiotic therapy of periimplant infections (funder DFG)
Examination of molecular processes of hip necrosis in comparison to coxarthrosis for the analysis of new therapeutic strategies (funder Erwin Röver Stiftung)
reatment of degenerative chondral lesions by the use of osteoproliferative Mg-beads in the subchondral bone plate (funder DFG)
In vitro and in vivo accumulation of magnetic nanoporous silica nanoparticles on implant materials with different magnetic properties.
Janßen HC, Warwas DP, Dahlhaus D, Meißner J, Taptimthong P, Kietzmann M, Behrens P, Reifenrath J, Angrisani N.
J Nanobiotechnology. 2018 Nov 27;16(1):96. doi: 10.1186/s12951-018-0422-6.
Differential Expression of Cholinergic System Components in Human Induced Pluripotent Stem Cells, Bone Marrow-Derived Multipotent Stromal Cells, and Induced Pluripotent Stem Cell-Derived Multipotent Stromal Cells.
Weist R, Flörkemeier T, Roger Y, Franke A, Schwanke K, Zweigerdt R, Martin U, Willbold E, Hoffmann A.
Stem Cells Dev. 2018 Feb 1;27(3):166-183. doi: 10.1089/scd.2017.0162. Epub 2018 Jan 3.
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