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

The unique chemical and physical properties of nanoparticles make them extremely suitable for designing new and improved sensing devices, especially electrochemical sensors and biosensors. Many kinds of nanoparticles, such as metal, oxide and semiconductor nanoparticles have been used for constructing electrochemical sensors and biosensors, and these nanoparticles play different roles in different sensing systems. The important functions provided by nanoparticles include the immobilization of biomolecules, the catalysis of electrochemical reactions, the enhancement of electron transfer between electrode surfaces and proteins, labeling of biomolecules and even acting as reactant. This minireview addresses recent advances in nanoparticle-based electrochemical sensors and biosensors, and summarizes the main functions of nanoparticles in these sensor systems.

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Application of Nanoparticles in Electrochemical Sensors and Biosensors

To demonstrate their applications in biological and medical fields such as in immunoassays, magnetic separation of cells or proteins, drug or gene delivery, and magnetic resonance imaging, the template-free syntheses of water-soluble and surface functionalized magnetic nanomaterials have become essential and are challenging. Herein, we developed a facile one-pot template-free method for the preparation of amine-functionalized magnetite nanoparticles and hollow nanospheres by using FeCl(3)6 H(2)O as single iron source. These magnetic nanomaterials were characterized by TEM, SEM, XRD, and FTIR technologies. Their magnetic properties were also studied by using a superconducting quantum interference device (SQUID) magnetometer at room temperature. Then the amine-functionalized magnetite nanoparticles were applied to immunoassays and magnetic resonance imaging in live mice.

One-pot synthesis and bioapplication of amine-functionalized magnetite nanoparticles and hollow nanospheres

Iron oxide nanoparticles–chitosan composite based glucose biosensor

Multifunctional Nanoparticles Possessing A “Magnetic Motor Effect” for Drug or Gene Delivery

Fe3O4 nanoparticles cast on pyrolytic graphite (PG) electrodes were used to immobilize hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP). The Fe3O4 nanoparticles provided a favorable microenvironment for the proteins to directly transfer electrons with electrodes. The protein–Fe3O4 films were used to electrochemically catalyze the reduction of oxygen, trichloroacetic acid, nitrite and hydrogen peroxide, and showed a potential applicability in fabricating biosensors. Transmission electron microscopy (TEM), UV–visible absorption and reflectance absorption infrared (RAIR) spectroscopy, and cyclic and square wave voltammetry, were used to characterize the films.

Electrochemical biosensors utilising electron transfer in heme proteins immobilised on Fe3O4 nanoparticles.

In this work, a novel two-step construction strategy for protein layer-by-layer assembly films was proposed. In the first step, positively charged hemoglobin (Hb) or myoglobin (Mb) at pH 5.0 was adsorbed on the negatively charged surface of 500 nm diameter-sized polystyrene (PS) latex beads, forming core-shell structured PS–protein particles. In the next step, the PS–protein particles were further assembled layer by layer with oppositely charged poly(styrene sulfonate)
				(PSS) on various solid surfaces under suitable conditions. Cyclic voltammetry (CV), quartz crystal microbalance (QCM), and UV-vis spectroscopy were used to monitor the growth of {(PS–protein)/PSS}n films. The stable {(PS–protein)/PSS}n films modified on pyrolytic graphite (PG) electrodes demonstrated good electroactivity in protein-free buffer, which was originated from protein heme Fe(III)/Fe(II) redox couples, and the electroactivity extended to six (PS–protein)/PSS bilayers. UV-vis spectroscopy showed that Hb and Mb in the films retained their near-native structure in the medium pH range. {(PS–protein)/PSS}n films catalyzed electrochemical reduction of oxygen, hydrogen peroxide, trichloroacetic acid (TCA) and nitrite with a significant lowering of overpotential, and displayed better catalytic activity than corresponding cast PS–protein films.

Naifei Hu

Papers

Electrochemical biosensors utilising electron transfer in heme proteins immobilised on Fe3O4 nanoparticles.

Electroactive layer-by-layer films of heme protein-coated polystyrene latex beads with poly(styrene sulfonate).