Polymerized crystalline colloidal array chemical-sensing materials for detection of lead in body fluids

Abstract

We have developed intelligent polymerized crystalline colloidal array (IPCCA) chemical-sensing materials for detection of Pb²⁺ in high ionic-strength environments such as body fluids with a detection limit of <500 nmol L^–1 Pb²⁺ (100 ppb). This IPCCA lead sensor consists of a mesoscopically periodic array of colloidal particles polymerized into an acrylamide hydrogel. The array Bragg-diffracts light in the visible spectral region because of the periodic spacing of the colloidal particles. This material also contains a crown ether chelating agent for Pb²⁺. Chelation of Pb²⁺ by the IPCCA in low-ionic-strength solutions results in a Donnan potential that swells the gel, which red-shifts the diffracted light in proportion to the Pb²⁺ concentration. At high ionic strength the Donnan potential is, unfortunately, swamped and no static response occurs for these sensors. We demonstrate, however, that we can determine Pb²⁺ at high ionic strength by incubating these IPCCA in a sample solution and then measuring their transient response on exposure to pure water. The non-complexed ions diffuse from the IPCCA faster than the bound Pb²⁺. The resulting transient IPCCA diffraction red-shift is proportional to the concentration of Pb²⁺ in the sample. These IPCCA sensors can thus be used as sensing materials in optrodes to determine Pb²⁺ in high-ionic-strength solutions such as body fluids.