State of Dispersion of Magnetic Nanoparticles in an Aqueous Medium: Experiments and Monte Carlo Simulation

Abstract

Monte Carlo simulation results predicting the state of dispersion (single, dimer, trimer, and so on) of coated superparamagnetic iron oxide (Fe(3)O(4)) nanoparticles in an aqueous medium are compared with our experimental data for the same. Measured values of the volume percentage of particles in the dispersion, core particle diameter, coating-shell thickness, grafting density of the coating agent, saturation magnetization, and zeta potential for the citric acid-coated and poly(acrylic acid) [PAA]-coated particles have been used in our simulation. The simulation was performed by calculating the total interaction potential between two nanoparticles as a function of their interparticle distance and applying a criterion for the two particles to aggregate, with the criterion being that the minimum depth of the secondary minima in the total interaction potential must be at least equal to k(B)T. Simulation results successfully predicted both experimental trends-aggregates for citric acid-coated particles and an individual isolated state for PAA-coated particles. We have also investigated how this state changes for both kind of coating agents by varying the particle volume percentage from 0.01 to 25%, the particle diameter from 2 to 19 nm, the shell thickness from 1 to 14 nm, and grafting density from 10(15) to 10(22) molecules/m(2). We find that the use of a lower shell thickness and a higher particle volume percentage leads to the formation of larger aggregates. The possible range of values of these four variables, which can be used experimentally to prepare a stable aqueous dispersion of isolated particles, is recommended on the basis of predictions from our simulation.

Targeting wild‐type and drug‐resistant mycobacteria in infected macrophages using drug‐coated nanoparticles

“…First, uncoated Fe 3 O 4 nanoparticles were synthesized by co‐precipitation . Briefly, a solution of FeCl 3 .6H 2 O (8.6 mmol) and FeCl 2 .4H 2 O (4.3 mmol), maintained in an inert environment, was reduced to IONPs using 25% (v/v) NH 4 OH solution.…”

Biocompatible citric acid‐coated iron oxide nanoparticles to enhance the activity of first‐line anti‐TB drugs in Mycobacterium smegmatis

“…Citric acid‐coated magnetite nanoparticles were synthesized by the chemical co‐precipitation method . Briefly 8.6 mmol of FeCl 3 .…”

“…Citric acid-coated magnetite nanoparticles were synthesized by the chemical co-precipitation method. 23 Briefly 8.6 mmol of FeCl 3 .6H 2 O and 4.3 mmol of FeCl 2 .4H 2 O (i.e. in 2:1 ratio) were placed in 100 mL of water in a round-bottom flask.…”

“…To this end, citric acid‐coated iron oxide (magnetite) nanoparticles (CA‐MNP) were synthesized and used in combination with INH or RIF in overcoming the intrinsic antibacterial resistance of M. smegmatis , which is known to have similar MDR profile to M. tuberculosis and hence is used in the screening of various anti‐TB agents . CA‐MNP's were chosen based on their properties of biocompatibility and stability in aqueous dispersions . Furthermore, citric acid is a potent permeabilizing agent for Gram negative bacteria .…”

“…22 CA-MNP's were chosen based on their properties of biocompatibility and stability in aqueous dispersions. 23 Furthermore, citric acid is a potent permeabilizing agent for Gram negative bacteria. 24 Thus, we have explored whether these nanoparticles can help drugs overcome the permeability barrier in mycobacteria, by investigating their uptake by M. smegmatis and its effectiveness with INH or RIF in terms of growth inhibition.…”