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.

Sequential addition of sulfur and Cd(acac)2 into the colloid solution of FePt nanoparticles ( approximately 2.5 nm) under a reductive environment generates heterodimers of CdS and FePt with sizes of approximately 7 nm. The heterodimers exhibit both superparamagnetism and fluorescence, indicating that the discrete properties of the individual parts of the dimers are preserved. This simple methodology may lead to the production of large quantities of various heterostructures with tailored properties on the nanoscale.

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.

N-(Fluorenyl-9-Methoxycarbonyl) dipeptides form supramolecular hydrogels via hydrogen bonding and hydrophobic interactions. These hydrogels respond to a ligand-receptor interaction as well as to thermal or pH perturbation and also exhibit chiral recognition.

Covalent organic frameworks (COFs) with well-defined and customizable pore structures are promising templates for the synthesis of nanomaterials with controllable sizes and dispersity. Herein, a thioether-containing COF has been rationally designed and used for the confined growth of ultrafine metal nanoparticles (NPs). Pt or Pd nanoparticles (Pt NPs and Pd NPs) immobilized inside the cavity of the COF material have been successfully prepared at a high loading with a narrow size distribution (1.7 ± 0.2 nm). We found the crystallinity of the COF support and the presence of thioether groups inside the cavities are critical for the size-controlled synthesis of ultrafine NPs. The as-prepared COF-supported ultrafine Pt NPs and Pd NPs show excellent catalytic activity respectively in nitrophenol reduction and Suzuki-Miyaura coupling reaction under mild conditions and low catalyst loading. More importantly, they are highly stable and easily recycled and reused without loss of their catalytic activities. Such COF-supported size-controlled synthesis of nanoparticles will open a new frontier on design and preparation of metal NP@COF composite materials for various potential applications, such as catalysis and development of optical and electronic materials.

Here we report the synthesis of vancomycin (Van)-capped Au nanoparticles (Au@Van) and their enhanced in vitro antibacterial activities. Au@Van presumably acts as a rigid polyvalent inhibitor of vancomycin-resistant enterococci (VRE). It also has unexpected activity against an E. coli strain. Our results suggest that gold nanoparticles may serve as a useful model system to explore multi/polyvalent interactions of ligand−receptor pairs.

Recent successful syntheses of monodispersed magnetic nanoparticles have offered a unique opportunity to control and probe biological interactions using magnetic force. This paper highlights a general strategy to generate biofunctional magnetic nanoparticles, illustrates applications for these nanoparticles in protein separation and pathogen detection, and analyzes the high sensitivity and high selectivity achieved by this system.

Covalently linked to vancomycin (Van), chemically stable and highly magnetic anisotropic FePt magnetic nanoparticles (3-4 nm) become water-soluble and capture vancomycin-resistant enterococci (VRE) and other Gram-positive bacteria at concentrations approximately 10(1) cfu/mL via polyvalent ligand-receptor interactions. When a pyramidal end of a magnet "focuses" the nanoparticles into approximately 1 mm(2) area, the bacteria can be observed by an optical microscope and further identified by electron micrograph (EM). Compared to the conventional use of magnetic particles (with the sizes of 1-5 microm) in biological separation or drug delivery, magnetic nanoparticles, combined with specific receptor-ligand interactions, promise a sensitive and rapid protocol to detect pathogens.