Aggregation Kinetics of TiO₂ Nanoparticles in Human and Artificial Sweat Solutions: Effects of Particle Properties and Sweat Constituents

Abstract

Dermal penetration potentials of titanium dioxide nanoparticles (TiO2 NPs) may be affected by aggregation upon contact with sweat. This study investigated the aggregation kinetics of three TiO2 NPs in thirty human sweat samples and four artificial sweat standards. Effects of particle concentration, sweat type, and inorganic (sodium chloride, disodium hydrogen phosphate, and sodium dihydrogen phosphate) and organic (l-histidine, lactic acid, and urea) constituents were examined. Three TiO2 NPs remained colloidally stable in >20/30 human sweat samples and showed significant negative correlations (P < 0.01) between aggregation rates and |zeta potentials|. They aggregated rapidly over 20 min to >750 nm in three artificial sweat standards, while remained more stable in the International-Standard-Organization-pH-5.5 standard. Aggregation behaviors of three TiO2 NPs mostly followed the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, allowing for determining their critical coagulation concentrations in inorganic constituents (15–491 mM) and Hamaker constants (3.3–7.9 × 10–21 J). Higher concentrations of particles, inorganic constituents, and l-histidine destabilized three TiO2 NPs, whereas urea inhibited aggregation. Three TiO2 NPs adsorbed organic sweat constituents via complexation with amino or carboxyl groups, with isotherms following the Langmuir model. Correlation analyses further suggested that the adsorbed organic constituents may stabilize three TiO2 NPs against aggregation in sweat by steric hindrance.

Unveiling the Potential of Bioinoculants and Nanoparticles in Sustainable Agriculture for Enhanced Plant Growth and Food Security

“…Titanium Dioxide Nanoparticles. One of the most popular semiconductors with photocatalytic activity is titanium BioMed Research International dioxide (TiO 2 ), an oxide generated from a transition metal [85]. It also used in various household items, including food-packaging materials, cosmetics, ceramics, plastics, paper, and paint [63].…”

“…However, excessive metal uptake by plants can have significant consequences both for the plant itself and for human health when these plants are consumed. In this detailed overview, we will explore the conse-quences of metal uptake in plants and its potential effects on humans [46,85,104,105]. [112,114], and individuals with compromised immune systems or underlying health conditions are particularly vulnerable to the adverse effects of metal exposure [116].…”

Heat Transfer by Sweat Droplet Evaporation

“…Sweat is a complex biofluid that contains solvents, solutes, and biomolecules. It carries significant physiological information. − It is an ultradilute yet nutrient-rich fluid consisting of 98% water and 2% solutes that include various amino acids, metabolites, and inorganic components such as salts . The evaporation and deposition dynamics of biofluid droplets exhibit a high level of complexity. − The complexity inherent in biofluid droplets alters their evaporation dynamics by manipulating their hydrodynamic and thermodynamic properties.…”