Rapid identification and high sensitive detection of cancer cells on the gold nanoparticle interface by combined contact angle and electrochemical measurements

In this study, we have proposed a novel strategy for the rapid identification and high sensitive detection of different kinds of cancer cells by means of electrochemical and contact angle measurements. A simple, unlabeled method based on the functionalized Au nanoparticles (GNPs) modified interface has been utilized to distinguish the different cancer cells, including lung cancer cells, liver cancer cells, drug sensitive leukemia K562/B.W cells and drug resistant leukemia K562/ADM cells. The relevant results indicate that under optimal conditions, this method can provide the quantitative determination of cancer cells, with a detection limit of ∼10³ cells mL⁻¹. Our observations demonstrate that the difference in the hydrophilic properties for target cellular surfaces and in the uptake efficiency of the anticancer drug daunorubicin for different cancer cells could be readily chosen as the elements of cancer identification and sensitive detection. This raises the possibility to advance the promising clinic diagnosis and monitoring of tumors with the aim of successful chemotherapy of human cancers.     

Recent progress in the determination of solid surface tensions from contact angles

Advancing contact angles of different liquids measured on the same solid surface fall very close to a smooth curve when plotted as a function of liquid surface tension, i.e., gamma(lv)costheta versus gamma(lv). Changing the solid surface, and hence gamma(sv), shifts the curve in a regular manner. These patterns suggest that gamma(lv)costheta depends only on gamma(lv) and gamma(sv). Thus, an "equation of state for the interfacial tensions" was developed to facilitate the determination of solid surface tensions from contact angles in conjunction with Young's equation. However, a close examination of the smooth curves showed that contact angles typically show a scatter of 1-3 degrees around the curves. The existence of the deviations introduces an element of uncertainty in the determination of solid surface tensions. Establishing that (i) contact angles are exclusively a material property of the coating polymer and do not depend on experimental procedures and that (ii) contact angle measurements with a sophisticated methodology, axisymmetric drop shape analysis (ADSA), are highly reproducible guarantees that the deviations are not experimental errors and must have physical causes. The contact angles of a large number of liquids on the films of four different fluoropolymers were studied to identify the causes of the deviations. Specific molecular interactions at solid-vapor and/or solid-liquid interfaces account for the minor contact angle deviations. Such interactions take place in different ways. Adsorption of vapor of the test liquid onto the solid surface is apparently the only process that influences the solid-vapor interfacial tension (gamma(sv)). The molecular interactions taking place at the solid-liquid interface are more diverse and complicated. Parallel alignment of liquid molecules at the solid surface, reorganization of liquid molecules at the solid-liquid interface, change in the configuration of polymer chains due to contact with certain probe liquids, and intermolecular interactions between solid and liquid molecules cause the solid-liquid interfacial (gamma(sl)) tension to be different from that predicted by the equation of state, i.e., gamma(sl) is not a precise function of gamma(lv) and gamma(sv). In other words, the experimental contact angles deviate from the "ideal" contact angle pattern. Specific criteria are proposed to identify probe liquids which eliminate specific molecular interactions. Octamethylcyclotetrasiloxane (OMCTS) and decamethylcyclopentasiloxane (DMCPS) are shown to meet those criteria, and therefore are the most suitable liquids to characterize surface tensions of low energy fluoropolymer films with an accuracy of +/-0.2 mJ/m2.     

Photometric determination of thioglycolic acid in cosmetics by using a stopped-flow reverse flow-injection system and the formation of gold nanoparticles

The positive effect of thiol compounds as reducing agents in the synthesis of gold nanoparticles in the presence of a micellar medium of Triton X-100 has been photometrically studied using a reverse flow-injection system which operates in the stopped-flow mode (SF-rFIA). The analytical usefulness of this new system has been assessed by its application to the determination of thioglycolic acid (TGA), which was chosen as the analyte model. The dynamic range of the calibration graph was 5.97–80 μmol L^?1, and the detection limit was 1.73 μmol L^?1. The behaviour of other thiol compounds on the system has been also studied. The precision of the method, expressed as relative standard deviation, ranged between 1.5 and 2.3%. The method was applied to the determination of TGA in several cosmetic samples with acceptable recoveries in all instances, which ranged between 90.32 and 101.46%.     

Specific adsorption of anions in the course of underpotential and bulk depositions and alloy formation of cadmium on a smooth gold support in acid medium

 The specific adsorption of ³⁶Cl-labelled Cl⁻ ions and ³⁵S-labelled HSO₄ ⁻ ions was studied in 1 mol dm⁻³ HClO₄ supporting electrolyte in the presence of Cd²⁺ ions at a gold support over a wide potential range corresponding to electrodeposition, alloy formation, underpotential deposition of Cd species and existence of an adatom-free surface. The distinct sections in the potential dependence of the adsorption of anions together with the potential versus time curves obtained under open circuit conditions reflect the changes in the state of the electrode surface, the dissolution of the bulk Cd phase and the slow elimination of Cd species from the Cd/Au alloy. Received: 16 March 1999 / Accepted: 5 May 1999