The combination of nanotechnology and molecular biology has developed into an emerging research area: nanobiotechnology. Magnetic nanoparticles are well-established nanomaterials that offer controlled size, ability to be manipulated externally, and enhancement of contrast in magnetic resonance imaging (MRI). As a result, these nanoparticles could have many applications in biology and medicine, including protein purification, drug delivery, and medical imaging. Because of the potential benefits of multimodal functionality in biomedical applications, researchers would like to design and fabricate multifunctional magnetic nanoparticles. Currently, there are two strategies to fabricate magnetic nanoparticle-based multifunctional nanostructures. The first, molecular functionalization, involves attaching antibodies, proteins, and dyes to the magnetic nanoparticles. The other method integrates the magnetic nanoparticles with other functional nanocomponents, such as quantum dots (QDs) or metallic nanoparticles. Because they can exhibit several features synergistically and deliver more than one function simultaneously, such multifunctional magnetic nanoparticles could have unique advantages in biomedical applications. In this Account, we review examples of the design and biomedical application of multifunctional magnetic nanoparticles. After their conjugation with proper ligands, antibodies, or proteins, the biofunctional magnetic nanoparticles exhibit highly selective binding. These results indicate that such nanoparticles could be applied to biological medical problems such as protein purification, bacterial detection, and toxin decorporation. The hybrid nanostructures, which combine magnetic nanoparticles with other nanocomponents, exhibit paramagnetism alongside features such as fluorescence or enhanced optical contrast. Such structures could provide a platform for enhanced medical imaging and controlled drug delivery. We expect that the combination of unique structural characteristics and integrated functions of multicomponent magnetic nanoparticles will attract increasing research interest and could lead to new opportunities in nanomedicine.

Spherical superparamagnetic iron oxide nanoparticles have been developed as T 2 -negative contrast agents for magnetic resonance imaging in clinical use because of their biocompatibility and ease of synthesis; however, they exhibit relatively low transverse relaxivity. Here we report a new strategy to achieve high transverse relaxivity by controlling the morphology of iron oxide nanoparticles. We successfully fabricate size-controllable octapod iron oxide nanoparticles by introducing chloride anions. The octapod iron oxide nanoparticles (edge length of 30 nm) exhibit an ultrahigh transverse relaxivity value (679.3±30 mM À 1 s À 1 ), indicating that these octapod iron oxide nanoparticles are much more effective T 2 contrast agents for in vivo imaging and small tumour detection in comparison with conventional iron oxide nanoparticles, which holds great promise for highly sensitive, early stage and accurate detection of cancer in the clinic.

Multifunctional nanocomposites have the potential to integrate sensing, diagnostic, and therapeutic functions into a single nanostructure. Herein, we synthesize Fe 3 O 4 @polydopamine core-shell nanocomposites (Fe 3 O 4 @PDA NCs) through an in situ self-polymerization method. Dopamine, a melanin-like mimic of mussel adhesive proteins, can self-polymerize to form surface-adherent polydopamine (PDA) films onto a wide range of materials including Fe 3 O 4 nanoparticles used here. In such nanocomposites, PDA provides a number of advantages, such as near-infrared absorption, high fluorescence quenching efficiency, and a surface for further functionalization with biomolecules. We demonstrate the ability of the Fe 3 O 4 @PDA NCs to act as theranostic agents for intracellular mRNA detection and multimodal imaging-guided photothermal * Address correspondence to hhyang@fio.org.cn, gangliu.cmitm@xmu.edu.cn.. Conflict of Interest:The authors declare no competing financial interest. Supporting Information Available:Additional information as noted in the text. This material is available free of charge via the Internet at http://pubs.acs.org. Messenger RNA (mRNA), a single-stranded ribonucleic acid, is also the blueprint for the cellular production of proteins. Moreover, some mRNAs are disease-relevant and can be utilized as markers to determine the stage of the disease. 22 Recently, several methods such as microarray analysis 23 and real-time polymerase chain reaction (RT-PCR) 24 have been developed for mRNA detection. Although these methods are effective for detecting mRNA expression in bulk samples, they are incapable of identifying cell-to-cell mutations. Significantly, many important biological processes not only are related with bulk mRNA expression, but also rely highly on cell-to-cell variations in mRNA. 25 Thus, it is necessary to develop useful approaches for detecting mRNA in living cells. [26][27][28][29][30][31][32] In this work, we fabricated multifunctional Figure 1a). Furthermore, we demonstrated that PDA can adsorb dye-labeled singlestranded DNA (ssDNA) probe and effectively quench the fluorescence of the dye. In the presence of the target, the specific binding between the dye-labeled ssDNA probe and its Figure 1c). Our results suggest a high potential for the use of PDA in the construction of multifunctional nanocomposites for simultaneous diagnosis and therapy of cancer. HHS Public Access RESULTS AND DISCUSSIONFe 3 O 4 NPs were easily coated with a uniform PDA shell by dispersing them in an alkaline DA solution and mildly shaking at room temperature for 4 h. Transmission electron microscopy (TEM) revealed that approximately a 4 nm thick PDA shell was wrapped on the surface of the Fe 3 O 4 NPs after self-polymerization of the DA ( Figure 2a). The dynamic light scattering (DLS) data showed that the hydrodynamic diameter of the Fe 3 O 4 NPs was increased after the PDA coating (Supporting Information Figure S1), which is consistent with the TEM results. Moreover, the Fe 3 O 4 @PDA NCs exhibited excelle...

On the basis of a fundamental property of nanoparticles, the self-assembling at a liquid-liquid interface to form "colloidosomes", a heterogeneous reaction takes place on the exposed surface of the nanoparticles to produce the heterodimers of two distinct nanospheres, which can be modified by two different functional molecules in a particle-specific manner.