Accelerated Particle-Based Target Capture—The Roles of Volume Transport and Near-Surface Alignment

Abstract

The upcoming generations of high-sensitive and miniaturized biosensing systems need target capture methods that are as efficient and as rapid as possible, with targets ranging from molecules to cells. Capture of the targets can be achieved using particles coated with affinity molecules, but there are still fundamental questions as to the processes that limit the association rates. In this paper we quantify and compare the reaction rates of particle-based target capture with different types of actuation, namely (i) passive thermal transport, (ii) fluid agitation by vortex mixing, and (iii) actively rotating particles. In the experiments, we use fluorescent nanoparticles as targets which are biochemically captured by magnetic microparticles, and the capture efficiency is quantified using fluorescence microscopy with single target resolution. The data unravel the contributions of volume transport, near-surface alignment, and the chemical reaction to the overall rate constant of association. Vortex mixing versus passive transport gives an increase of the reaction rate constant by more than an order of magnitude, implying that the encounter frequency as well as the near-surface alignment probability are increased. The importance of near-surface alignment is underscored by the data of active particle rotation; the binding probability per encounter is 4-fold enhanced on rotating capture particles. We discuss the implications of our results for different biological systems and for the development of novel actuation methods in particle-based target capture.

Integrated lab-on-chip biosensing systems based on magnetic particle actuation – a comprehensive review

“…So, the bimolecular reaction involves the binding between a reactive particle and a protein, where the biochemical specificity to the targeted protein is determined by the capture proteins coupled to the particle. We have performed an experimental study 57 to identify to what extent the different stages of the binding process are limiting. In particular, the diffusional encounter step was split up into the process of diffusional transport through the fluid volume and the process of near-surface alignment (see Fig.…”

Glancing angle metal evaporation synthesis of catalytic swimming Janus colloids with well defined angular velocity

“…As an example of the potential for rotating devices, micron sized spinning colloids have been shown to influence the directional growth of neurons in vitro, 10 induce cell death by bursting lysosomes through the generation of shear forces, 11 and enhance surface protein binding rates. 12 However, these demonstrations required external actuation of the rotational behaviour, achieved via applying circularly polarized light with angular momentum to an optically trapped bead, using dynamic magnetic fields to rotate superparamagnetic iron oxide nanoparticles, and the rotation of magnetic colloids using a quadrupole magnet respectively. Another tested scheme for inducing rapid rotation assembled arrays of nanowire rotors onto patterned nanomagnetic bearings, actuated by quadrupole microelectrodes, which resulted in controlled rotation over 18 000 rpm.…”

How Actuated Particles Effectively Capture Biomolecular Targets

“…This is consistent with a previous study that we performed on the process of particle-based target capture. In that study, we used a model system with 200 nm particles as targets 14 and we found that the capture process is limited by both the translational and rotational diffusion of the reacting species.…”