Effect of pH and dye concentration on the n-octanol/water distribution ratio of phenothiazine dyes: a microelectrode voltammetry study

Effect of air bubbles on the membrane filtration of rhodamine B

Effect of air bubbles on the membrane filtration of a basic dye, rhodamine B (RB), using a hydrophilic PTFE membrane filter (pore size: 0.20 μm) was studied. The air bubbles were generated by vigorously mixing the aqueous solution containing 0.05% (v/v) of 1-butanol with a shaft generator of a homogenizer. RB being far smaller than the pore size of the membrane filter could not be rejected without air bubbles, but it was rejected by the membrane filter in the presence of air bubbles. The rejection ratio increased with increasing the rotation speed of the shaft generator because of the increase in the amount of air bubbles and therefore the increase in the surface area of air bubbles for the adsorption of RB. On the other hand, another basic dye, methylene blue (MB), was negligibly rejected in the same condition. Dynamic surface tension measurement of aqueous solutions containing different amounts of dye indicated that RB strongly adsorbed to the air-water interface, while MB hardly adsorbed. The results obtained in the present study strongly suggest the potential usefulness of air bubbles for the selective microfiltration of dissolved organic molecules or ions.

Enhanced and long-term CT imaging tracking of transplanted stem cells labeled with temperature-responsive gold nanoparticles

Gold nanoparticles (AuNPs) have been extensively employed for computed tomography (CT) imaging in cell labeling and tracking because of their strong X-ray attenuation coefficient and excellent biocompatibility. However, the design and synthesis of stimuli-responsive AuNPs to modulate their endocytosis and exocytosis for optimal cell labeling and tracking are promising but challenging. Herein, we report an innovative labeling strategy based on temperature-responsive AuNPs (TRAuNPs) with high cell labeling efficiency and extended intracellular retention duration. We have manifested that the TRAuNP labeling imposes a negligible adverse effect on the function of human mesenchymal stem cells (hMSCs). Further experiment with idiopathic pulmonary fibrosis (IPF) model mice has demonstrated the feasibility of TRAuNP labeling for long time CT imaging tracking of transplanted hMSCs. What's more, the survival of transplanted hMSCs could also be monitored simultaneously using bioluminescence imaging after the expression of luciferase reporter genes. Therefore, we believe that this dual-modal labeling and tracking strategy enables visualization of the transplanted hMSCs in vivo, which may provide an important insight into the role of stem cells in the IPF therapy.

Molecular Dynamics Modeling of Methylene Blue-DOPC Lipid Bilayer Interactions

We present a coarse-grained MARTINI model for methylene blue (MB) and investigate the interactions of MB with dioleylphosphatidylcholine (DOPC) lipid bilayers by molecular dynamics simulations. Our results show that the charge state of MB and the oxidation degree of the DOPC bilayer play critical roles on membrane properties. Oxidation of the DOPC bilayer significantly increases permeability of water and MB molecules, irrespective of the charge state of MB. The most significant changes in membrane properties are obtained for peroxidized lipid bilayers in the presence of cationic MB, with ∼11% increase in the membrane area per lipid head group and ∼7 and 44% reduction in membrane thickness and lateral diffusivity, respectively.

New insights about the self-aggregation of benzoporphyrin derivatives: A theoretical and experimental investigation

The self-aggregation process and its overcoming remain a barrier for the employment of many molecules as photosensitizers (PS) in photodynamic therapy (PDT). The B-ring isomer co-produced during the synthesis of the Verteporfin[Formula: see text] (A-ring) is an example. Although both isomers possess similar in vitro/in vivo efficiency, the strong and not well-understood self-aggregation process of the B-ring derivative impairs its clinical use. This paper reports the use of theoretical calculus and its correlation with experimental analysis to find the main differences between the A and B-ring isomers. For that purpose, micelles of Pluronic[Formula: see text] P-123 and Sodium Dodecyl Sulfate were chosen as simple membrane models and possible drug delivery system, as in the case of P-123. At physiological pH, the main reason for the high self-aggregation tendency is associated with the higher (22%) molecular volume of the B ring, which increases the van der Waals interactions. However, at mildly acidic conditions, the B ring possesses a shallow dihedral angle between the methyl ester group and the tetrapyrrolic macrocycle that favors the approach of units in the aggregate. These discrepancies directly affect the binding and stability of the isomers in the micelles. However, P-123 micelles were able to readily incorporate and monomerize/stabilize both PS over long periods. NOESY experiments confirmed a deep location of both PS inside P-123 micelles, which justifies their efficiency in preventing the self-aggregation process. These findings may substantiate new studies involving the marginalized B-ring isomers and encourage new development in formulations for their use in PDT.