Preparation of Magnetic Hydrogel Microparticles with Cationic Surfaces and Their Cell-Assembling Performance

Abstract

Cationic magnetic hydrogel microparticles with high retention on cell surfaces were prepared using a two-step procedure. Using these magnetic hydrogel microparticles, cells were clustered with each other, and cell aggregates were prepared effectively. Cross-linked poly­(vinyl alcohol) (PVA) hydrogel microparticles containing iron oxide nanoparticles were prepared. The diameter of the microparticles was in the range of 200–500 nm. Water-soluble cationic polymers containing both trimethyl ammonium (TMA) groups and phenylboronic acid (PBA) groups were synthesized for the surface modification of the microparticles. To regulate the composition, electrically neutral phosphorylcholine groups were introduced into the polymer. Covalent bonds were formed between the hydroxy groups of PVA microparticles and PBA groups in the polymer. The surface zeta potential of the microparticles reflected the composition of the TMA groups. The particles responded to an external magnetic field and clustered rapidly. Microparticles were adsorbed on the floating cell surface and induced cell aggregation quickly when a magnetic field was applied. Under the most effective conditions, the diameter of the cell aggregates increased to approximately 1 mm after 30 min. Denser cell aggregates were formed by the synergistic effects of the magnetic field and the properties of the microparticles. The formed cell aggregates continued to grow for more than 4 days under an applied magnetic field, indicating that the ability of the cells in the aggregate to proliferate was well maintained.

Fabrication of polymeric microspheres for biomedical applications

“…Recently, the reverse (or inverse) phase emulsion method using a W/O emulsion has emerged. 38,39 During the polymerization process, the monomer droplets which are also called mini-emulsions are the principal locus of microparticle nucleation. And the initiators, surfactants, and oils used in this process can affect the kinetic mechanism, thus resulting in the different physical characteristics of the microparticles.…”

Design and Control of the Magnetically Actuated Micro/Nanorobot Swarm toward Biomedical Applications

“…[62] To enable magnetically actuated micro/nanorobot swarms to perform specific biomedical tasks, functional materials need to be modified on magnetic particles to improve their biocompatibility. [59,60,81,103,104] The hydrogel-based magnetic microrobots facilitate not only biocompatibility but also exhibit responsiveness under magnetic, [105][106][107] biological, [108] pH, [103,[109][110][111] and photothermal stimuli, [112,113] rendering them the most widely employed biocompatible materials. For example, Zhang et al developed a pH-responsive selfhealing hydrogel magnetic swarm which is prepared by the co-crosslinking of acrylyl-6-aminocaproic acid monomer and N-isopropylacrylamide with bis-acrylamide (BIS).…”

Versatile magnetic hydrogel soft capsule microrobots for targeted delivery

“…Hydrogel-based biocompatible materials are increasingly attractive due to their considerable biocompatibility and potential multifunctionality. 37 , 38 , 39 , 40 , 41 Responsive disintegration of hydrogel materials provides a good candidate for capsule structure designs, enabling controllable release by magnetic response, 39 , 40 , 42 , 43 biological reaction response, 44 pH response, 45 , 46 , 47 and light-heat response 48 , 49 ( Table 1 ). For in vivo operations in deeper tissues, magnetic hydrogel materials are mainly utilized for actuation and delivery, 39 , 40 , 42 , 43 while light penetration depth severely limits the light-heat response mechanisms.…”

“… 37 , 38 , 39 , 40 , 41 Responsive disintegration of hydrogel materials provides a good candidate for capsule structure designs, enabling controllable release by magnetic response, 39 , 40 , 42 , 43 biological reaction response, 44 pH response, 45 , 46 , 47 and light-heat response 48 , 49 ( Table 1 ). For in vivo operations in deeper tissues, magnetic hydrogel materials are mainly utilized for actuation and delivery, 39 , 40 , 42 , 43 while light penetration depth severely limits the light-heat response mechanisms. 42 , 48 The relatively stable human internal environments cannot always fulfill the requirements for the pH and biological reaction response mechanisms.…”