This review focuses on the synthesis, protection, functionalization, and application of magnetic nanoparticles, as well as the magnetic properties of nanostructured systems. Substantial progress in the size and shape control of magnetic nanoparticles has been made by developing methods such as co-precipitation, thermal decomposition and/or reduction, micelle synthesis, and hydrothermal synthesis. A major challenge still is protection against corrosion, and therefore suitable protection strategies will be emphasized, for example, surfactant/polymer coating, silica coating and carbon coating of magnetic nanoparticles or embedding them in a matrix/support. Properly protected magnetic nanoparticles can be used as building blocks for the fabrication of various functional systems, and their application in catalysis and biotechnology will be briefly reviewed. Finally, some future trends and perspectives in these research areas will be outlined.

Magnetic nanoparticles: Synthesis, protection, functionalization, and application

In the last 10 years the field of molecular diagnostics has witnessed an explosion of interest in the use of nanomaterials in assays for gases, metal ions, and DNA and protein markers for many diseases. Intense research has been fueled by the need for practical, robust, and highly sensitive and selective detection agents that can address the deficiencies of conventional technologies. Chemists are playing an important role in designing and fabricating new materials for application in diagnostic assays. In certain cases assays based upon nanomaterials have offered significant advantages over conventional diagnostic systems with regard to assay sensitivity, selectivity, and practicality. Some of these new methods have recently been reviewed elsewhere with a focus on the materials themselves or as subclassifications in more generalized overviews of biological applications of nanomaterials.1-7 We intend to review some of the major advances and milestones in the field of detection systems based upon nanomaterials and their roles in biodiagnostic screening for nucleic acids, * To whom correspondence should be addressed. Phone: 847-4913907. Fax: 847-467-5123. E-mail: chadnano@northwestern.edu. Nathaniel L. Rosi earned his B.A. degree at Grinnell College (1999) and his Ph.D. degree from the University of Michigan (2003), where he studied the design, synthesis, and gas storage applications of metal−organic frameworks under the guidance of Professor Omar M. Yaghi. In 2003 he began postdoctoral studies as a member of Professor Mirkin’s group at Northwestern University. His current research focuses on the rational assembly of DNA-modified nanostructures into larger-scale materials.

/pdf/nanostructures-in-biodiagnostics-5553cs9yqw.pdf

Nanostructures in Biodiagnostics

Nanotechnology is a multidisciplinary field, which covers a vast and diverse array of devices derived from engineering, biology, physics and chemistry. These devices include nanovectors for the targeted delivery of anticancer drugs and imaging contrast agents. Nanowires and nanocantilever arrays are among the leading approaches under development for the early detection of precancerous and malignant lesions from biological fluids. These and other nanodevices can provide essential breakthroughs in the fight against cancer.

Cancer nanotechnology: opportunities and challenges.

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Integrated Nanoparticle–Biomolecule Hybrid Systems: Synthesis, Properties, and Applications

/pdf/nanoparticle-pegylation-for-imaging-and-therapy-45vkc0dds0.pdf

Nanoparticle PEGylation for imaging and therapy

The rapid and sensitive determination of pathogenic bacteria is extremely important in biotechnology, medical diagnosis, and the current fight against bioterrorism. Current methods either lack ultrasensitivity or take a long time for analysis. Here, we report a bioconjugated nanoparticle-based bioassay for in situ pathogen quantification down to single bacterium within 20 min. The bioconjugated nanoparticle provides an extremely high fluorescent signal for bioanalysis and can be easily incorporated with biorecognition molecules, such as antibody. The antibody-conjugated nanoparticles can readily and specifically identify a variety of bacterium, such as Escherichia coli O157:H7, through antibody–antigen interaction and recognition. The single-bacterium-detection capability within 20 min has been confirmed by the plate-counting method and realized by using two independent optical techniques. The two detection methods correlated extremely well. Furthermore, we were able to detect multiple bacterial samples with high throughput by using a 384-well microplate format. To show the usefulness of this assay, we have accurately detected 1–400 E. coli O157 bacterial cells in spiked ground beef samples. Our results demonstrate the potential for a broad application of bioconjugated nanoparticles in practical biotechnological and medical applications in various biodetection systems. The ultimate power of integrating bionanotechnology into complex biological systems will emerge as a revolutionary tool for ultrasensitive detection of disease markers and infectious agents.

https://www.pnas.org/content/pnas/101/42/15027.full.pdf

A rapid bioassay for single bacterial cell quantitation using bioconjugated nanoparticles

Sensitive DNA detection is extremely important in clinical diagnostics, gene therapy, and a variety of biomedical studies. We have developed a novel DNA bioanalysis method with a 0.8 fM (0.8 x 10-15 M) detection limit using a bioconjugated fluorescent nanoparticle-based sandwich assay. An organic dye silica nanoparticle is synthesized using a modified reverse microemulsion. The nanoparticles are highly fluorescent, extremely photostable, and easy for bioconjugation for bioanalysis. They exhibit an excellent signaling ability in the presence of trace amounts of DNA targets. With an effective surface modification, nonspecific binding and nanoparticle aggregation are minimized. In addition, the nanoparticle-based DNA bioanalysis assay can effectively discriminate one-base mismatched DNA sequences. We expect this nanoparticle-based assay to be widely useful in a number of biomedical applications where reproducible, selective, and ultrasensitive gene analysis is critical.

Ultrasensitive DNA detection using highly fluorescent bioconjugated nanoparticles.

Development of Organic‐Dye‐Doped Silica Nanoparticles in a Reverse Microemulsion

The glow and photostability, along with other advantages, of dye-doped silica nanoparticles make their future bright in bioanalytical applications.

Watching Silica Nanoparticles Glow in the Biological World

Silica-coated nanoparticles functionalized with biologically active molecules such as antibodies and nucleotides are used to label cells, to detect and isolate nucleic acid molecules having specific nucleotide sequences, and to separate a mixture of different nucleic acid molecules. The nanoparticles (10) comprise a core (12), a shell (14) coating core (12), and one or more functional groups (16) derivatized onto shell (14).

Xiaojun Zhao

Papers

A rapid bioassay for single bacterial cell quantitation using bioconjugated nanoparticles

Ultrasensitive DNA detection using highly fluorescent bioconjugated nanoparticles.

Development of Organic‐Dye‐Doped Silica Nanoparticles in a Reverse Microemulsion

Watching Silica Nanoparticles Glow in the Biological World

Functionalized nanoparticles and methods of use