Micro–nanoparticles magnetic trap: Toward high sensitivity and rapid microfluidic continuous flow enzyme immunoassay

Abstract

In this work, we developed a microfluidic system for immunoassays where we combined the use of magnetic nanoparticles as immunosupport, a microfluidic magnetic trap, and a fluorogenic substrate in continuous flow for detection which, together with the optimization of the functionalization of surfaces to minimize nonspecific interactions, resulted in a detection limit in the order of femtomolar and a total assay time of 40 min for antibiotin antibody detection. A magnetic trap made of carbonyl-iron microparticles packaged inside a 200 μm square microchannel was used to immobilize and concentrate nanoparticles. We functionalized the surface of the iron microparticles with a silicapolyethylene glycol (PEG) shell to avoid corrosion and unspecific protein binding. A new one-step method was developed to coat acrylic microchannels with an organofunctional silane functionalized with PEG to minimize unspecific binding. A model immunoassay was performed using nanoparticles decorated with biotin to capture antibiotin rabbit Immunoglobulin G (IgG) as target primary antibody. The detection was made using antirabbit IgG labeled with the enzyme alkaline phosphatase as a secondary antibody, and we measured fluorescence with a fluorescence microscope. All steps of the immunoassay were performed inside the chip. A calibration curve was obtained in which a detection limit of 8 pg/ml of antibiotin antibody was quantified. The simplicity of the device and the fact that it is made of acrylic, which is compatible with mass production, make it ideal for Point-Of-Care applications.

Optofluidic Particle Manipulation: Optical Trapping in a Thin-Membrane Microchannel

“…Magnetic trapping works similarly to electrical but is implemented instead with a magnetic field. A field gradient is generated by magnets on chip and is then used to hold molecules that are bound to magnetic nanobeads [ 5 ]. Optical trapping can be implemented using on-chip counter propagating dual beam divergence and loss-based traps to hold particles for further manipulation [ 6 , 7 , 8 ].…”

Development of Phantoms for Multimodal Magnetic Resonance Imaging and Magnetic Particle Imaging

“…Some studies have used AM methods to generate physiological structures filled with MNP for MPI but have not investigated their suitability for MRI [ 9 , 10 , 11 ]. In addition, special consideration should be given to the interaction of phantom materials with the MPI tracer, since nonspecific absorption on the material surface [ 12 , 13 ] may lead to signal alterations of the immobilized tracer [ 14 ]. Furthermore, it is important to ensure that these materials do not produce magnetic signals [ 15 ].…”