The ultimate goal of tissue engineering (TE) is to completely restore the damaged tissue to its pre-injury state, while reducing healing time and medical complications. For this reason, the field relies on the development of artificial composite materials (stents) that can provide structural support during the initial stages of tissue formation. These engineering scaffolds should have the following characteristics: (i) simulate the complex structure of natural tissue from nanometer to macroscopic; (ii) meet the mechanical, electrical and structural characteristics of the tissue, which are heterogeneous in almost all cases; (iii) ) Provide the required biophysical and biochemical clues to induce the growth, proliferation and differentiation of the required encapsulated cells; (iv) Ensure the technical scalability of the scaffold design on demand.



Most tissues of the human body have highly anisotropic physical properties and biological tissues. The inherent properties of magnetic nanoparticles enable them to be used as magneto-mechanical remote actuators to control the behavior of cells encapsulated in hydrogels under the action of an external magnetic field. Recently, the team of Professors Rui M. A. Domingues and Manuela E. Gomes of the University of Minho in Portugal published a review titled  Magnetic Nanocomposite Hydrogels for Tissue Engineering: Design Concepts and Remote Actuation Strategies to Control Cell Fate on  ACS Nano . They combined a detailed summary of the main strategies for preparing magnetic nanoparticles that exhibit controlled properties, and the analysis of different methods for incorporating them into hydrogels. The applications of magnetically responsive nanocomposite hydrogels in different tissue engineering are also reviewed.







Figure 1. Schematic diagram: Using magnetic hydrogels to engineer different tissues of the human body.





Figure 2. Transmission electron microscope images of different MNPs





Figure 3. (a) Typical magnetization versus applied magnetic field (MvsH) curves of iron/ferrimagnetic, superparamagnetic, diamagnetic and paramagnetic materials. (B) A schematic diagram of the direction of the atomic magnetic moments in spherical and cubic MNPs when an external magnetic field is applied. (C) Schematic diagram of the effect of zinc doping on MNP of magnetite. (D) Ligand exchange, replacing the original ligand (blue) and (e) a schematic diagram of a polymer coating (MNP is surrounded by a polymer layer (red)). The initial oleic acid-terminated MNP is in (g) hexane (top)-water (bottom) mixture before and after polymer coating with poly(maleic acid-alt-anhydride) grafted dodecylamine Medium stable.





Figure 4. The static magnetic field that generates anisotropic biomaterials





Figure 5. (a) Schematic diagram of different strategies that can be used to prepare hydrogels loaded with MNPs. (B) The concentration of the influence of incorporation of different numbers of perpendicular and parallel magnetically responsive cellulose nanocrystals on the storage modulus of gelatin hydrogels. (D) The effect of isotropic and anisotropic gelatin hydrogel on the arrangement of inoculated human adipose-derived stem cells (hASC). (E) After encapsulation of human mesenchymal stem cells, the cartilage protein markers aggrecan (red), SOX9 (green) and collagen II (green) are up-regulated in the magnetic hydrogel.





Figure 6. Microscope image of an anisotropic hydrogel prepared by doping a magnetically responsive material and then applying an external magnetic field. The upper image shows the sample under static conditions, and the lower image shows the sample under the action of a magnetic field.





Figure 7 Cartilage. (A) Schematic diagram of the anisotropic structure of cartilage tissue. (B) Application of magnetic hydrogel in cartilage TE: the development of bioprinting two-layer collagen-based hydrogel.





Figure 8 (a) Schematic diagram of the hierarchical structure of bone tissue from macroscopic to nanoscale. (B) Application of magnetic hydrogel in bone TE.



Figure 9 Tendons and tendons to bone. (A) Schematic view of tendon-bone interface and (b) tendon/ligament tissue. (C) Application of magnetic hydrogel in tendon-bone TE.

Paper link:

doi.org/10.1021/acsnano.0c08253


Information Source: Polymer Materials Science

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