Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

Abstract

Tunable pores (TPs) have been used for resistive pulse sensing of 1 lm superparamagnetic beads, both dispersed and within a magnetic field. Upon application of this field, magnetic supraparticle structures (SPSs) were observed. Onset of aggregation was most effectively indicated by an increase in the mean event magnitude, with data collected using an automated thresholding method. Simulations enabled discrimination between resistive pulses caused by dimers and individual particles. Distinct but time-correlated peaks were often observed, suggesting that SPSs became separated in pressure-driven flow focused at the pore constriction. The distinct properties of magnetophoretic and pressure-driven transport mechanisms can explain variations in the event rate when particles move through an asymmetric pore in either direction, with or without a magnetic field applied. Use of TPs for resistive pulse sensing holds potential for efficient, versatile analysis and measurement of nano-and microparticles, while magnetic beads and particle aggregation play important roles in many prospective biosensing applications.

Microscopy and tunable resistive pulse sensing characterization of the swelling of pH-responsive, polymeric expansile nanoparticles

“…For example, Willmott et al used magnetic fields to cause aggregation and increased translocation rates of super-paramagnetic beads with blockades characterized by multiple overlapped peaks and thus overall increased TD. 54 However, in the current study, the overall particle concentration (and thus translocation rate) decreases with eNP swelling (Fig. 11) thus making the likelihood of multiple, nearly simultaneous, overlapping translocations negligible.…”

A tunable nanopore sensor for the detection of metal ions using translocation velocity and biphasic pulses

“…31 As with all RPS sensors the only consumable is the tunable pore, eliminating the need for a carrier gas, fluidics, or optics. TRPS has been validated to accurately determine the concentration, size and surface charge of dispersed inorganic particles 24,[32][33][34][35][36][37] as well as the concentration of a range of biological analytes, which have been reviewed previously. 38,39 Conical nanopores, as used within TRPS, exhibit ionic rectification properties.…”

Tunable Resistive Pulse Sensing: Potential Applications in Nanomedicine

“…The authors concluded that the system demonstrates promise as an effective drug vehicle in targeted and controlled inhalation therapy. The ability of TRPS to characterise SPIONs was also studied by Willmott and colleagues [18,70]. SPIONS are widely used in molecular identification, purification, separation and aggregation.…”

“…TRPS is an adaptation of RPS in which utilises a conical tunable elastomeric pore that can be stretched or relaxed to change the pore size to suit the sample [11,13,[15][16][17][18][19]. Tunable pore membranes are made of thermoplastic polyurethane and the pores are introduced by mechanical puncture.…”

“…Some initial studies by Willmott and Platt [18] have shown that some information of length of asymmetric particles (cylinders) or clusters of spherical particles can be extracted from peak width/ pulse duration. Other groups have also used the flexible TRPS pore to deform and characterise soft polymer like particles [23].…”