Magnetic Nanoparticle Based Biosensors for Pathogen Detection and Cancer Diagnostics

Sammanfattning: This thesis describes several magnetic nanoparticle (MNP)-based biosensing strategies which take advantage of different magnetic sensors, molecular tools and nanotechnologies. Proposed biosensors can be classified into three groups, i.e., immunoassay-based, molecular amplification-based, and nanoparticle assembly-based. The principal motivation is to develop and optimize biosensors for out-of-lab and point-of-care testing.Immunoassay-based biosensors described in this thesis employ antibodies as the bio-recognition element for the detection of bacteria cells/fragments or proteins. Two typical immunoassay formats, i.e., direct and competitive format, are studied and compared for bacteria detection. In addition, in the protein biomarker detection, MNP chains are formed in the presence of target analytes as well as in the external rotating magnetic field. The high shape/magnetic anisotropy of the chains provides better optomagnetic performance.Two different molecular amplification methods, i.e., rolling circle amplification (RCA) and loop-mediated isothermal amplification (LAMP), are described under the topic of molecular amplification-based biosensors. In RCA-based biosensors, DNA probe modified MNPs bind to the amplicons after amplification. In LAMP-based biosensors, MNPs are either modified with primers that keep growing during the amplification, or are co-precipitated with the by-product (Mg2P2O7) of the amplification.The design of the nanoparticle assembly-based biosensors described in this thesis is based on duplex-specific nuclease (DSN)-assisted target recycling and core-satellite magnetic superstructures. In the presence of target microRNA, DSN cuts the DNA scaffold of the core-satellite assembly, releasing MNP satellites that can be quantified by the sensor.Different kinds of target analytes, i.e., pathogens or cancer biomarkers, are detected at the aiming for rapid, low-cost and user-friendly diagnostics.