Cisplatin-tethered gold nanoparticles that exhibit enhanced reproducibility, drug loading, and stability: a step closer to pharmaceutical approval?

Gold nanoparticles (AuNPs) can be used as delivery vehicles for platinum anticancer drugs, improving their targeting and uptake into cells. Here, we examine the appropriateness of different-sized AuNPs as components of platinum-based drug-delivery systems, investigating their controlled synthesis, reproducibility, consistency of drug loading, and stability. The active component of cisplatin was tethered to 25, 55, and 90 nm AuNPs, with the nanoparticles being almost spherical in nature and demonstrating good batch-to-batch reproducibility (24.37 ± 0.62, 55.2 ± 1.75, and 89.1 ± 2.32 nm). The size distribution of 25 nm AuNPs has been significantly improved, compared with a previous method that produces polydispersed nanoparticles. Attachment of platinum to the AuNP surface through a poly(ethylene glycol) (PEG) linker exhibits an increase in the drug loading with increasing particle size: 25 nm (815 ± 106 drug molecules per AuNP), 55 nm (14216 ± 880), and 90 nm (54487 ± 15996). The stability of the naked, PEGylated, and platinum-conjugated nanoparticles has been examined over time under various conditions. When stored at 4 °C, there is minimal variation in the diameter for all three AuNP sizes; variation after 28 days for the 25 nm AuNPs was 2.4%; 55 nm, 3.3%; and 90 nm, 3.6%. The 25 nm AuNPs also demonstrate minimal changes in UV-visible absorbance over the same time period.     

Infinitely many Gerretsen-Blundon style quadratic inequalities, all strongest in Blundon’s sense

Blundon has proved that if R, r and s are respectively the circumradius, the inradius and the semiperimeter of a triangle, then the strongest possible inequalities of the form q(R, r) ≤ s ² ≤ Q(R, r) that hold for all triangles becoming equalities for the equilaterals where q, Q real quadratic forms, occur for the Gerretsen forms q _B (R, r) = 16Rr ? 5r ² and Q _B (R, r) = 4R ² + 4Rr + 3r ²; strongest in the sense that if Q is a quadratic form and s ² ≤ Q(R, r) ≤ Q _B (R, r) for all triangles then Q(R, r) = Q _B (R, r), and similarly for q _B (R, r). In this paper we prove that Q _B (resp. q _B ) is just one of infinitely many forms that appear as minimal (resp. maximal) elements in the partial order induced by the comparability relation in a certain set of forms, and we conclude that all these minimal forms are strongest in Blundon’s sense. We actually find all possible such strongest forms. Moreover we find all possible quadratic forms q, Q for which q(R, r) ≤ s ² ≤ Q(R, r) for all triangles and which hold as equalities for the equilaterals.     

On the determination of a measure by the orbits generated by its logarithmic potential

We say that a logarithmic potential generates a curve in the plane if a unit mass traces the curve under the action of the potential. We consider the following problem: A one-parameter family of plane curves is given. We assume that these curves lie in the complement of a compact set . Find all measures supported in whose potentials generate each of the given curves. We solve this problem when is the unit circle in three specific cases: (a) when the given curves are straight lines through the origin, (b) when the curves are straight lines through a point on the unit circle, and (c) when the curves are circles centered at the origin. The solution involves the Poisson integral and its boundary behavior.

     

Interaction of (hydroxypropyl) cellulose with anionic surfactants in dilute regime

(Hydroxypropyl)cellulose (HPC) dilute aqueous solutions in the presence of sodium cholate (CS), sodium deoxycholate (DC), and sodium dodecylsulphate (SDS) were investigated. The hydrophobicity parameter (I ₁/I ₃) from fluorescence has shown a critical aggregation concentration (CAC) lower than the critical micellar concentration (CMC). One or two breakpoints were observed in the curve conductivity vs surfactant concentration. The thermodynamic parameters of aggregation (, and ) and the degree of counterion dissociation were calculated. Evidences for the secondary aggregation of CS/water system were found. The relative viscosity increases for HPC/bile salt solutions only at high surfactant concentrations, whereas for HPC/SDS, it passes through a maximum. The cloud points of both HPC/bile salt solutions at higher surfactant concentrations reach a temperature plateau value around 324 K, while for HPC/SDS, it exceeds 373 K at low SDS concentrations. Dynamic light scattering has demonstrated that the surfactants bind to HPC already at concentrations lower than CAC.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Experimental and theoretical investigations of new dinuclear palladium complexes as precatalysts for the amination of aryl chlorides

A series of new palladium dinuclear species with general formula [Pd2X(mu-X)[mu-P(t)Bu2(Bph-R)]] (X = Cl, Br; Bph = biphenyl; R = H, Me, NMe2) have been prepared. The two palladium centers in these species are bridged by one of the aromatic rings of the biphenyl group present in the corresponding phosphine. The X-ray crystal structure of one of these complexes has been obtained, providing a clear picture of the bonding pattern. The stability of these dimers in solution is shown to be highly dependent on the nature of the phosphine R group and also on the bridging halide. When R = NMe2, the dimers dissociate, yielding the palladium(II) compounds PdX2[P(t)Bu2(BPh-NMe2)] (X = Cl, Br), and the X-ray crystal structure of one of them (X = Br) has shown that the biphenyl group from the phosphine interacts directly with the metal center. This interaction seems to play an important role in stabilizing the otherwise coordinatively unsaturated palladium(II) complex. In contrast, when R = H or Me, the analogous monomeric palladium(II) complexes are unstable and undergo cyclometalation to generate a palladium(II) dinuclear species in which each of the two phosphines cyclometalates with the palladium centers forming a strained four-membered ring. In addition to their unusual structures, these aryl-bridged dimers have also proven to be excellent precatalysts for the amination of aryl chlorides. To rationalize some of the experimental results, a detailed DFT computational study has been carried out and is presented herein.     

A three-state model for the polymorphism in linear tricobalt compounds

The remarkable polymorphism exhibited by the linear tricobalt compounds, Co3(mu3-dpa)4Cl2 and Co3(mu3-dpa)4Br2, can be explained using a model involving three distinct electronic states. At high temperatures, symmetric and unsymmetric forms arise from the population of doublet (2A) and quartet (4B) states, respectively, the latter containing a localized high-spin Co(II) center. In the unsymmetric form, a reduction in temperature leads to a spin-crossover to a second quite distinct doublet state, 2B, where, uniquely, the d(x2-y2) character on the localized Co(II) center is distributed between the occupied and vacant manifolds. The variable population of the Co d(x2-y2) orbital gives rise to the continuous change in Co-Co and Co-N bond lengths as the temperature is decreased.     

Equilibrium desorption isotherms of water,ethanol, ethyl acetate,and toluene on a sodium smectite clay

Desorption isotherms for water, ethanol, ethyl acetate and toluene from a sodium smectite clay have been determined by both dynamic vapor sorption (DVS) measurements and Knudsen thermogravimetry (KTGA), at the exception of toluene that was measured only by the DVS method. The results obtained using these two methods were in satisfactory agreement, providing reliable insight into the desorption process, with certain lack of precision for ethyl acetate. The observed desorption behaviour suggests a liquid like phase at high volatile load, and a sorbed state in which molecules interact with the counter ions, at low volatile contents. However, the isotherms for water determined at various temperatures nearly superposed when plotted as a function of water activity, indicating the strength of the interactions in the clay–water system to remain of the same order of magnitude as that in bulk water, consistent with previous ab initio calculations.