MRI-based material testing of biodegradable hybrid materials with incorporated magnetic nanoparticles for in vivo applications

• Applicant: Professorin Dr. Ioana Slabu
• Subject Area: Medical Physics, Biomedical Technology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467959793

Biodegradable implants are expected to gain immense importance in therapy. They promise to combine the advantages of high mechanical stability (as for synthetic implants) and low adverse effect rates (as for biological implants). Although a few biodegradable implant types obtained CE marking, they could not prevail in the market. Clinical studies showed that the success of therapeutic applications of biodegradable implants for structural support, regeneration and healing of tissues is often impeded by premature degradation of the implants.In this research project, a method for future in vivo determination of the relevant implant properties (especially its degradation state) is established by means of in vitro measurements. In these measurements, magnetic nanoparticles (MNP) inside the implants will be used as sensors in the magnetic field of a magnetic resonance imaging (MRI) device. This method targets at determining and monitoring the degradation state of implants via MRI, so detailed information can be non-invasively and reliably gained for future therapy planning.Incorporating the MNP into the biodegradable material creates a modified implant with new material properties. The new properties must be assessed, and the fundamental dependencies must be determined. Due to the envisaged application in MRI, the influence of magnetic fields must also be identified.The MRI methods for the quantitative determination of the degradation state are developed using single filaments of an implant and specific MR phantoms. For any MNP type, the MR phantoms allow for systematic analysis of the MR signal dependencies on different MNP sizes and agglomeration states as well as on different MNP concentrations and immobilization states to find an appropriate and precise measurement technique. For each of the degradation states, mechanical testing is performed to estimate the functionality of the implants in structural support of tissue. The MR examinations will be supplemented by extensive physicochemical and mechanical examinations in order to gain deeper understanding of the information generated by MR imaging. Furthermore, the precision of the MR measurement is checked by comparison measurements on reference samples with spectroscopic methods.The aim of the research project is to deduce physical relations for the behavior of the biodegradable implant material (e. g. for the interaction of MNP with the surrounding filament matrix at different degradation states and mechanical properties) from the collected data and to predict effects on the MR signal. This should allow both controlled production of biodegradable implants and future quantitative in vivo determination of their mechanical function using MRI.

• DFG Programme: Research Grants