Application of Magnetic Nanoparticles in Protein Expression
The past two decades have seen breakthroughs in understanding molecular biology, genomics, and nanotechnology. The intersection of these three disciplines has opened up a new field of research - bionanotechnology and nano biomedical technology. Additionally, tremendous advances in the synthesis and characterization of nanomaterials have enabled scientists to understand and control nanomaterials (including nanowires, nanofibers, nanoparticles, nanoribbons, and nanotubes) at the molecular or cellular level in relation to biological entities ( Interactions between nucleic acids, proteins or cells). These advances have guaranteed great achievements in the field of life sciences. For example, the recently successfully synthesized monodisperse magnetic nanoparticles (MNPs), originally used in high-density magnetic storage media, provide a basis for further developing MNPs in biomedical applications. Weissleder and his team demonstrated that MNPs can be applied in MRI to monitor specific enzymes and detect viruses. Cheon et al. reported the application of multifunctional magnetic nanocrystals for cancer detection in vivo. Willner et al. showed that MNPs can act as magnetic switches, induce selective bioelectrocatalysis, detect cancer, and amplify DNA detection. The above examples demonstrate the potential of MNPs in life sciences.
Protein Separation Using Magnetic Nanoparticles
Efficient manipulation of proteins is critical for life science research and applications. Especially for proteomics, the routine work of purifying native or recombinant proteins does take a long time. However, the successful synthesis of NTA-terminated MNPs provides a simple and versatile platform for protein isolation. In addition, due to the characteristics of high surface-to-volume ratio, fast movement, and good dispersion of MNPs (8-10 nm), they perform better than micron-sized resins or microbeads applied in metal chelate affinity chromatography (MCAC), and can be used in Greatly improve the binding rate between Ni-NTA and histidine-tagged protein. In addition, the high surface-to-volume ratio also enhances the protein-binding ability of nanoparticles (NPs). Target proteins rapidly cover the surface of NPs, which can rapidly reduce the overall unoccupied surface area available for nonspecific protein uptake. Therefore, NPs have much higher specificity than microparticles. In addition, NTA-terminated MNPs can eliminate the pretreatment of cell lysates since the magnets can easily separate target proteins (Figure 1).
Figure 1: Magnet attracts FePt- NTA - Ni (II) ( NTA- terminated FePt MNPs) and FePt- NTA-Ni (II)-6xHis-GFP images
Pathogen Detection Using Magnetic Nanoparticles
MNPs enable rapid and ultrasensitive detection of pathogens such as bacteria and viruses without the need for incubation or Time-consuming procedures, such as PCR amplification, which have shown clear clinical benefits. However, this assay cannot detect bacteria at low concentrations (eg, 102 cfu/mL) before the bacteria are pre-enriched (by the inoculation process). Using FePt-V and MNPs (attached vancomycin to FePt MNPs) can capture and detect a variety of bacteria at concentrations below 102 cfu/mL within one hour. After incubating the FePt-Van MNPs with the bacterial solution for 10 min, the bacteria bound to the FePt-Van MNPs could be easily attracted using a spot magnet. Then, bacteria and FePt-Van MNPs form aggregates under the action of magnetic force. The same procedure was performed using FePt- NH2 (FePt NPs reacted with cystamine) as a control (Fig. 2) . It was found that FePt-V and MNPs did capture bacterial strains, while FePt- NH2 could not bind to any bacteria.
Figure 2: (a) FePt-Van MNPs capture bacteria via rational multivalent interactions and (b) corresponding control experiments
Further Applications of Magnetic Nanoparticles
In addition to their unique ability to isolate targets from mixtures with high specificity and sensitivity, MNPs can also elucidate specific biological interactions in electron micrographs by conjugating antibodies as affinity tags.
The ability of biologically functional MNPs to serve as markers to localize ligand-receptor interactions on cells suggests that it would be worthwhile to couple MNPs with other markers to expand readout methods beyond TEM or SEM. Quantum dots are one of the attractive labeling candidates because of their excellent optical properties. However, it is impossible to attach single reactive groups or molecules to MNPs or QDs, and it is very difficult to directly link MNPs to QDs using organic linkers without cross-linking. Therefore, the researchers devised a simple strategy to link MNPs and quantum dots as heterodimers. The heterodimer of the two nanocrystals retained the properties of their discrete parts (FePt and CdS). In other words, the heterodimer has both the superparamagnetic behavior of FePt and the fluorescence of CdS. Coupling FePt to bioactive molecules to construct biologically functional heterodimers should be possible. Another attractive label is the silver NPs because of their value in probing biological systems via surface-enhanced Raman spectroscopy (SERS) signals.
References
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3. Xu, C., Xu, K., Gu, H., Zhong, X., Guo, Z., & Zheng, R., et al. （2004）. Nitrilotriacetic acid-modified magnetic nanoparticles as a general agent to bind histidine-tagged proteins. Journal of the American Chemical Society, 126（11）, 3392-3393.https://doi.org/10.1021/ja031776d
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https://doi.org/10.1039/B514130C