No abstract

Gold nanorods (GNRs) exhibit promising potentials in therapeutics and diagnostics. A quartz crystal microbalance with dissipation (QCM-D) monitoring was used to study the influence of size and solution chemistry on the deposition of GNRs on a model cell membrane. Supported lipid bilayers (SLBs) comprising zwitterionic 1,2-dioleoyl-snglycero-3-phosphocholine were used as the model cell membrane. QCM-D results showed that the deposition mass of GNRs on SLBs increased with increasing GNR concentration from 1 to 50 μM. The GNRs with smaller size exhibited a higher deposition mass in comparison with the larger one when they had a similar zeta potential. Additionally, pH also influenced the deposition behavior of GNRs on SLBs because of the change in their electrostatic interaction. Under neutral pH conditions, the deposition masses of GNRs on SLBs increased with increasing concentrations of NaCl, which is probably attributed to the reduced electrostatic repulsive force. However, the deposition mass of GNRs decreased over a range of CaCl 2 concentration from 0.5 to 10 mM. In this case, the GNR aggregation and electrostatic repulsion between GNRs and SLBs may occur due to the charge reversal of SLBs. The deposition kinetic showed that the final deposition mass was positively correlated with the initial deposition rate. Furthermore, a possible mechanism was proposed. This study provides a good understanding of the deposition of GNRs with cell membranes.

Fly ash particles can contribute to haze and adverse health outcomes. In this study, two mucins, one from bovine submaxillary glands (bovine submaxillary mucin, BSM) and one from porcine stomach (porcine gastric mucin), as well as bovine serum albumin (BSA), which served as the physical barriers against foreign substances entering the tissues and the blood protein, respectively, were chosen as models for the investigations of the interactions between the proteins and the fly ash particles. Their adsorption behaviors were studied using spectroscopy and a quartz crystal microbalance with a dissipation monitor (QCM-D). The results indicated that the fly ash particles can induce the loosening of mucins and BSA, probably via the formation of complexes. Further, the secondary structure of proteins changed in the presence of fly ash particles. The α-helix content decreased with an increasing fly ash particle concentration. The addition of fly ash particles into protein solutions led to fluorescence quenching, which suggested that there were interactions between these particles and the mucins and BSA. The association constants ( K) for BSM and BSA were 5.35 and 4.18 L/g, respectively. Furthermore, the results of QCM-D analyses showed that the amount decreased on the mucin surface but increased slightly on the BSA surface, which indicated that the fly ash particles disrupted the mucin layer upon adsorption. These findings provide clear evidence of the interactions between the fly ash particles and the mucins and BSA, which can lead to structural changes. This study contributes to a better understanding of the interactions and adsorptions of atmospheric particulate pollutants with the proteins in the human body.