Recent research has looked to develop innovative, powerful and novel biofunctionalized nanoparticles, controlling and tailoring their properties in a very predictable manner to meet the needs of clinic immunoassays in the biomedical field. This minireview briefly summarizes recent advances covering the last 3 years, exploiting nanoparticle-based electrochemical, optical, mass-sensitive, colorimetric and immunodipstick assays. The enormous signal enhancement associated with the use of nanoparticles and formation of nanoparticle-antibody-antigen assemblies provide the basis for sensitive detection of disease-related proteins or biomarkers. Rather than being exhaustive, this minireview focuses on selected examples to illustrate novel concepts and promising applications. Finally, a small amount of speculation of possible future developments in nanoparticle-based immunoassays is provided.

A facile and simple electrochemical immunoassay for ultrasensitive determination of streptomycin residues (STR) in food was designed by using nanogold-assembled mesoporous silica (GMSNs) as bionanolabels on a three-dimensional redox-active organosilica-functionalized sensing interface. To construct such a sensing interface, we initially synthesized organosilica colloids by using wet chemical method, and then utilized the prepared colloidal organosilica nanocomposites for the immobilization of monoclonal anti-STR antibodies on a glassy carbon electrode based on a sol-gel method. The bionanolabels were prepared based on coimmobilization of horseradish peroxidase (HRP) and STR-bovine serum albumin conjugates (STR-BSA) on the GMSNs. With a competitive-type immunoassay format, the assay toward STR analyte was carried out in pH 5.5 acetate acid buffer (ABS) by using redox-active organosilica nanocomposites as electron mediators, biofunctionalized GMSNs as traces, and hydrogen peroxide (H(2)O(2)) as enzyme substrate. Under optimal conditions, the reduction current of the electrochemical immunosensor decreased with the increase in STR level in the sample, and displayed a wide dynamic range of 0.05-50 ng mL(-1) with a low detection limit (LOD) of 5 pg mL(-1) at 3s(B). Intra- and interassay coefficients of variation were less than 8.7 and 9.3% for STR detection, respectively. In addition, the methodology was validated with STR spiked samples including honey, milk, kidney, and muscle, receiving a good correspondence with the results obtained from high-performance liquid chromatography (HPLC).

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Herein, we describe a new method for the detection of hydrogen peroxide (H 2 O 2 ) in food by using an electrochemical biosensor. Initially, ultrafine gold nanoparticles dispersed on graphene oxide (AuNP-GO) were synthesized by the redox reaction between AuCl 4 À and GO, and thionine-catalase conjugates were then assembled onto the AuNP-GO surface on a glassy carbon electrode. With the aid of the AuNP-GO, the as-prepared biosensor exhibited good electrocatalytic efficiency toward the reduction of H 2 O 2 in pH 5.8 acetic acid buffer. Under optimal conditions, the dynamic responses of the biosensor toward H 2 O 2 were achieved in the range from 0.1 mM to 2.3 mM, and the detection limit (LOD) was 0.01 mM at 3s B . The Michaelis-Menten constant was measured to be 0.98 mM. In addition, the repeatability, reproducibility, selectivity and stability of the biosensor were investigated and evaluated in detail. Finally, the method was applied for sensing H 2 O 2 in spiked or naturally contaminated samples including sterilized milk, apple juices, watermelon juice, coconut milk, and mango juice, receiving good correspondence with the results from the permanganate titration method. The disposable biosensor could offer a great potential for rapid, cost-effective and on-field analysis of H 2 O 2 in foodstuff.

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