Biocompatible Magnetic Micro‐ and Nanodevices: Fabrication of FePt Nanopropellers and Cell Transfection

Abstract

The application of nanoparticles for drug or gene delivery promises benefits in the form of single‐cell‐specific therapeutic and diagnostic capabilities. Many methods of cell transfection rely on unspecific means to increase the transport of genetic material into cells. Targeted transport is in principle possible with magnetically propelled micromotors, which allow responsive nanoscale actuation and delivery. However, many commonly used magnetic materials (e.g., Ni and Co) are not biocompatible, possess weak magnetic remanence (Fe3O4), or cannot be implemented in nanofabrication schemes (NdFeB). Here, it is demonstrated that co‐depositing iron (Fe) and platinum (Pt) followed by one single annealing step, without the need for solution processing, yields ferromagnetic FePt nanomotors that are noncytotoxic, biocompatible, and possess a remanence and magnetization that rival those of permanent NdFeB micromagnets. Active cell targeting and magnetic transfection of lung carcinoma cells are demonstrated using gradient‐free rotating millitesla fields to drive the FePt nanopropellers. The carcinoma cells express enhanced green fluorescent protein after internalization and cell viability is unaffected by the presence of the FePt nanopropellers. The results establish FePt, prepared in the L10 phase, as a promising magnetic material for biomedical applications with superior magnetic performance, especially for micro‐ and nanodevices.

Medical Micro/Nanorobots in Precision Medicine

“…Intracellular transfection of plasmid was used by active targeting of carcinoma by inducing cell expression of green fluorescent protein. [ 303 ] Magnetic nanorobots have also been used for intracellular surface‐enhanced Raman spectroscopy. [ 304 ] The development of biocompatible magnetic materials is of great importance to reduce risk and improved performance.…”

Nanomotors Sense Local Physicochemical Heterogeneities in Tumor Microenvironments**

“…Ab rief description of the experimental setup,nanomotor fabrication and motion in rBM can be found in the supplementary information (SI:S ection S1).The helical structures (see Figure 1a inset) were made of silica with embedded iron particles,a nd were fabricated by Glancing Angle Deposition. [24] These were confirmed to be biocompatible [34,43] (see SI:S ection S2). Cell-embedded matrix scaffolds along with nanomotors was placed inside the Helmholtz coil and observed through af luorescence microscope.T he nanomotors were moved unidirectionally up to am illimeter for 30 minutes under ar otating magnetic field of constant strength and frequency.A ss hown in Figure 1a,w eobserved that almost all of the nanomotors approaching CC adhered to the ECM in its vicinity ( % 10-40 mm) (also see Movie M1 and SI: Figure S2 for additional images of adhered nanomotors imaged at higher magnification).…”

Trends in Micro‐/Nanorobotics: Materials Development, Actuation, Localization, and System Integration for Biomedical Applications

“…The component design of the m‐bots should also depend on the propulsion regime. In the case of magnetically actuated m‐bots, magnetic materials such as Fe 3 O 4 , Ni, γ‐Fe 2 O 3 , and FePt, [ 28,45,54,103 ] should be considered. For bubble‐propelled m‐bots in the environment that contains fuel, catalytic materials such as Au, Pt, Ag, MnO 2 , TiO 2 , and enzyme may need be used to obtain asymmetric bubble propulsion.…”