The Regenerative Medicine Materials Research Group of the Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, successfully prepared a new type of tissue engineering scaffold and orthopedic implant material that can be magnetically degraded by utilizing the magnetocaloric effect of magnetic nanoparticles under an alternating magnetic field. This study synthesized magnetically responsive ferroferric oxide nanoparticles and compounded them with polylactic acid-polyglycolic acid copolymer (PLGA). The resulting magnetic composite scaffold has the unique property of accelerating degradation under an alternating magnetic field and can be adjusted by Frequency, current and other parameters can control the degradation behavior of implanted materials in real time, solving the problem that the degradation rate of polymer tissue engineering implanted materials cannot be controlled in real time after being implanted in the body. This research work was recently published in the internationally renowned magazine Advanced Functional Materials (Adv. Funct. Mater. 2021, DOI:10.1002/adfm.202009661), with a current impact factor of 16.836. This research result has applied for a Chinese invention patent (201911249311.0).

Ferric oxide nanoparticles have been widely used in magnetic hyperthermia, nuclear magnetic imaging, drug delivery, biological separation and other fields due to their good biocompatibility and high saturation magnetic susceptibility. Among them, magnetic hyperthermia uses the magnetocaloric effect of magnetic materials to achieve therapeutic effects. That is, in an alternating magnetic field, magnetic materials generate heat through eddy current loss, hysteresis, magnetic vector rotation and the physical rotation of the particles themselves to kill tumors. cell. According to the fact that the degradation behavior of degradable polyester materials mostly has obvious temperature dependence, the research team introduced ferric oxide nanoparticles into degradable tissue engineering materials to prepare magnetic composite scaffolds, and studied its performance under an alternating magnetic field. degradation behavior. In vitro degradation experiments show that the degradation rate of magnetic scaffolds can be significantly accelerated under an alternating magnetic field. Among them, oleic acid-modified ferric oxide nanoparticles (IO-OA NPs), which have good interfacial compatibility with hydrophobic polymer matrices, The effect of accelerating stent degradation under the same alternating magnetic field is more significant. In addition, coarse-grained molecular dynamics simulations were used to study the impact of the properties (size, surface modification, etc.) of high-frequency vibrating nanoparticles on the heating efficiency of the polymer matrix. The results show that small particles with grafted chains have a more obvious heating effect on the system when subjected to alternating forces. This may be because the enhanced motion correlation between the magnetic nanoparticles and the polymer matrix can accelerate energy transfer. The introduction of magnetic nanomaterials makes up for the problem of uncontrollable degradation behavior of degradable polymer tissue engineering scaffolds in vivo. Molecular dynamics simulations further provide optimization strategies for nanomaterials to achieve higher heating efficiency. Magnetic-controlled degradation is expected to become a new strategy for artificially regulating the degradation behavior of implants. It can design a portable wearable device with the advantages of non-invasiveness and spatio-temporal treatment to achieve clinical precision treatment and personalized treatment.

Based on the above research results, the research group is further studying the feasibility of clinical application of this technology.

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Figure 1. Schematic illustration of magneto-controlled degradation in polymer implants. a) The preparation methods of magnetic nanoparticles (NPs) and composite scaffolds. b) The degradation device model of scaffolds under alternating magnetic field (AMF). c) Utilizing the magnetocaloric effect of magnetic NPs to regulate the hydrolysis rate of biodegradable polymers. d) The micro-mechanism of the difference in energy transfer caused by the properties of magnetic NPs (within the hands), and corresponding degradation status of scaffolds (out of the hands). e) An expected apparatus to decide the fate of biodegradable polymer implants with the advantages of portable, wearable, noninvasive and spatiotemporal therapy.

Figure 2. a) Temperature changes of the scaffolds and PBS media under AMF+. b). Changes in mass loss of the scaffolds at 0-16 weeks during degradation. c). Micro-CT scanned axial graphs (mapping) of the scaffolds after degradation for 0 and 12 weeks.

Figure 6. Model and results of Molecular dynamics simulation. a) Schematic representation of the simulation models, where the red dots represent PLGA with length N = 120 (the pink and orange beads are two representations). The blue and green beads denote IO nanoparticles and the grafted OA chains, respectively. Bonded and non-bonded interactions between different beads are shown in the right column. An alternating force is applied on the blue beads in the z direction to simulate the application of AMF. b) The temperature of PLGA matrix T_matrix as a function of simulation time t in different systems.