Colorimetric Detection of MPT64 Antibody Based on an Aptamer Adsorbed Magnetic Nanoparticles for Diagnosis of Tuberculosis.

We have developed a colorimetric biosensing system for the detection of antibody against MPT64, a protein secreted by Mycobacterium tuberculosis, using aptamer DNA adsorbed Fe3O4 magnetic nanoparticles (MNPs) for diagnosis of tuberculosis (TB). In this system, MNPs were first incubated with single stranded (ss) DNA-type aptamer having a high affinity toward target antibody against MPT64 (anti-MPT64), resulting in quick inhibition of the peroxidase-like activity of MNPs via the adsorption of aptamer on the surface of MNPs. By the addition of sample solutions containing anti-MPT64, aptamer bound on the surface of MNPs would strongly interact with free anti-MPT64 and be detached from the MNPs, thereby increasing the available surface area of the MNPs and consequently yielding enhanced peroxidase activity. Using this strategy, target anti-MPT64 was successfully detected by displaying increased colorimetric intensities from the higher oxidation of employed peroxidase substrate, 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulfonic acid) (ABTS). Based on these results, we anticipate that aptamer adsorbed MNPs can serve as a potent probe system for the detection of clinically important target molecules.

Highly sensitive colorimetric detection of allergies based on an immunoassay using peroxidase-mimicking nanozymes.

Nanomaterials that exhibit enzyme-like characteristics, which are called nanozymes, have recently attracted significant attention due to their potential to overcome the intrinsic limitations of natural enzymes, such as low stability and relatively high cost for preparation and purification. In this study, we report a highly efficient colorimetric allergy detection system based on an immunoassay utilizing the peroxidase-mimicking activity of hierarchically structured platinum nanoparticles (H-Pt NPs). The H-Pt NPs had a diameter of 30 nm, and were synthesized by a seed-mediated growth method, which led to a significant amount of peroxidase-like activity. This activity mainly occurs because of the high catalytic power of the Pt element, and the fact that the H-Pt NPs have a large surface area available for catalytic events. The H-Pt NPs were conjugated to an antibody for the detection of immunoglobulin E (IgE) in the analytes; IgE is a representative marker for the diagnosis of allergies. They were then successfully integrated into a conventionally used allergy diagnostic test, the ImmunoCAP diagnostic test, as a replacement for natural signaling enzymes. Using this strategy, total and specific IgE levels were detected within 5 min at room temperature, with high specificity and sensitivity. The practical utility of the immunoassay was also successfully verified by correctly determining the levels of both total and specific IgE in real human serum samples with high precision and reproducibility. The present H-Pt NP-based immunoassay system would serve as a platform for rapid, robust, and convenient analysis of IgE, and can be extended to the construction of diagnostic systems for a variety of clinically important target molecules.

Cerium Aminoclay-A Potential Hybrid Biomaterial for Anticancer Therapy.

In this study, novel biomedical properties of Ce-aminoclay (CeAC) were investigated through in vitro and in vivo assays. CeAC (≥500 µg/mL) can selectively kill cancer cells (A549, Huh-1, AGS, C33A, HCT116, and MCF-7 cells) while leaving most normal cells unharmed (WI-38 and CCD-18Co cells). Notably, it displayed a high contrast of simultaneous imaging in HeLa cells by blue photoluminescence without any fluorescence dye. Its anticancer mechanism has been fully demonstrated through apoptosis assays; herein CeAC induced high-level apoptosis (16%), which promoted the expression of proapoptotic proteins (Bax, p53, and caspase 9) in tumor cells. Besides, its biological behavior was determined through antitumor effects using intravenous and intratumoral administration routes in mice implanted with HCT116 cells. During a 40 day trial, the tumor volume and tumor weight were reduced by a maximum of 92.24 and 86.11%, respectively. The results indicate that CeAC exhibits high bioavailability and therapeutic potential based on its unique characteristics, including high antioxidant capacity and electrostatic interaction between its amino functional groups and the mucosal surface of cells. In summary, it is suggested that CeAC, with its high bioimaging contrast, can be a promising anticancer agent for future biomedical applications.

Nanohybrids consisting of magnetic nanoparticles and gold nanoclusters as effective peroxidase mimics and their application for colorimetric detection of glucose.

Although protein-stabilized gold nanoclusters (AuNCs) have gathered recent attention as biocompatible peroxidase mimics, their practical utility has been critically limited by the low catalytic activity. Here, the authors have developed a nanohybrid material to significantly enhance the catalytic activity of AuNCs by combining them with other inorganic enzyme mimetics, Fe3O4 magnetic nanoparticles (MNPs), through electrostatic attraction. Owing to the synergistic effect by incorporating AuNCs and MNPs, the constructed nanohybrids yielded highly enhanced catalytic activity and enabled rapid catalytic oxidation of 3,3',5,5'-tetramethylbenzidine substrate to produce a blue-colored solution in proportional to the amount of H2O2. Moreover, a highly sensitive and selective glucose biosensing strategy was developed based on the coupled catalytic action between glucose oxidase and the nanohybrids. Using this method, target glucose was successfully detected in a linear concentration range from 150 to 750 µM with a detection limit as low as 100 µM. Along with excellent linearity, high precision and reproducibility were achieved by employing real human blood serums, which enables its use for the reliable quantification of glucose in practical use. Based on these results, the authors anticipate that the nanohybrids consisting of MNPs and AuNCs can serve as potent peroxidase mimics for the detection of clinically important target molecules.