Nanotechnology for Biosensing Applications
Authors: Zhou H. Susan 
Published: February 2020

Nanomaterials, notable for their extremely small feature size (normally in the range of 1 - 100 nm), exhibit new chemical, physical and electronic properties that are different from those of bulk materials. Nanomaterials research is expected to present new possibilities for the development in many areas including energy, manufacturing, space exploration, medicineand medical devices, chemical analysis, and environmental monitoring.

Nanotechnology has drawn much interest recently in the field of biomedical applications. Gold Nanoparticle (AuNP) and Magnetic Nanoparticle (MNP) are the two that have been studied most extensively due to its unique properties. For biomedical applications, AuNP is ideal for targets due to its low reactivity, high chemical stability, and biocompatibility, as well as its affinity for binding to amine (-NH2) or thiol (-SH) terminal groups of organic molecules.Magnetic nanoparticles (MNPs) have been receiving increasing attention because of its great potentials in separation.

This talk will give an overview of biosensor researches that are taking place at the microfluidics and bionanotechnology lab at WPI. A system of adenosine/its aptamer that is tagged by Au NPs was used to construct a SPR sensor to detect adenosine. They also explored the ability of aptamer-Au NPs conjugates in increasing the sensitivity of SPR for the detection of large biomolecules. They further investigated the application of SPR spectroscopy for fast, ultrasensitive and in situ detection of the MNPs-enriched biomolecules. They have successfully developed an amplification technique using MNPs for enhanced SPR bioassay, for both small molecule detection and immunoassay.

Clostridium difficileis a frequent cause of infectious colitis, usually occurring as a complication of antibiotic therapy, in elderly hospitalized patients. The diagnosis of C. difficileinfection still remains a challenge. Searching for a selective and specific technique for determination of its level in biological samples is crucial for regular clinical tests. The current diagnostic modalities mainly consist of the detection of the C. difficileorganisms and of their toxins in fecal samples. However, these methods are often time consuming and require sophisticated equipment. With recent advances in nanotechnology, various nanoparticles in different structures, shapes and composites provide good potential for their application in diagnostics and therapy. Nowadays, electrochemical biosensors based on nanoparticles have attracted extensive interest for sensing the formation of antigen–antibody, because of their fast and precise response, high sensitivity and simple pretreatment procedures. Herein, we developed an electrochemical sensor with gold nanoparticles labeled antibody as the amplifying probe for detecting clostridium difficiletoxins. Initially capture antibody was immobilized on gold electrode using conventional amine coupling chemistry. After clostridium difficiletoxins were attached on the capture antibody, gold nanoparticle labeled detect antibody as the amplifying probe was used to optimize the immunosensing performance by a sandwich immunoassay. In order to evaluate the electrochemical characteristics of modified electrode, cyclic voltammetry (CV) data were collected for each step. Compared with the traditional method, our method can be operated very simply and rapidly, thus it may possess great potential for clinical applications in the future.