Zinc is an essential trace element and co-factor for many cellular processes. Uptake of Zn 2+ in peripheral tissues depends on its total content in the circulation, and on mechanisms facilitating delivery to tissues in its labile form. Understanding mechanisms of Zn 2+ delivery has been hindered by the absence of techniques to detect labile Zn 2+ in the circulation. In this study, we report the use of the fluorescent zinc-binding dye, ZnAF-2, to detect changes in labile Zn 2+ in the circulating plasma of the rat under standardized conditions, including exogenous infusions to raise plasma Zn 2+ , and infusion of the chelator, citrate, to lower labile Zn 2+ in the plasma without altering total Zn2+ content. In a model of mild surgical stress (unilateral femoral arterial ligation), plasma levels of total and labile Zn 2+ decreased significantly 24 hours following operation. Ultrafiltration of plasma into high and low molecular weight macromolecule fractionations indicated that binding capacity of zinc in the high molecular weight fraction is impaired for the entire 24 hour interval following induction of mild surgical stress. Affinity of the filtrate fraction was rapidly and reversibly responsive to anesthesia alone, decreasing significantly at 4 hours and recovering at 24 hours; in animals subjected to moderate surgical stress this responsiveness was lost. These are the first reported measurements of labile Zn 2+ in the circulation in any form of mild systemic stress. Zinc undergoes substantial redistribution in the plasma, response to surgical stress, leading to increased availability in lower molecular weight fractions and in its labile form.

Monochloramine (NH(2)Cl) is a potent, thiol-directed oxidant capable of oxidizing thiol (S-H) residues in a wide variety of proteins. Generated in the stomach by the interaction of bacterial and host products, monochloramine has been shown to dysregulate Ca(2+) homeostasis and disrupt mucosal integrity. In this report, we show that monochloramine also leads to disturbances in intracellular free zinc concentration ([Zn(2+)](i)) in the gastric gland of the rabbit and that the increased Zn(2+) within the cell causes an independent decrease in cell viability. Changes in [Zn(2+)](i) were measured by using the fluorescent reporter FluoZin-3, whereas cell viability was assessed by measuring the conversion of calcein-AM to fluorescent calcein, an assay that is not affected by intracellular oxidation state. Cell death was confirmed using propidium iodide and YO-PRO-1 dye uptake measurements. Our experiments demonstrate that [Zn(2+)](i) is increased in gastric glands exposed to NH(2)Cl and that elevated [Zn(2+)](i) decreases cell viability. Chelation of Zn(2+) with tetrakis-(2-pyridylmethyl) ethylenediamine decreases the toxicity of NH(2)Cl, but only when administered concurrently. These findings suggest that the toxic effect of thiol oxidants present during chronic gastritis is partially due to dysregulation of [Zn(2+)](i) early in the process and that zinc chelation can protect, but not rescue, gastric glands exposed to toxic doses of NH(2)Cl.

Targeted delivery of drugs and sensors into cells is an attractive technology with both medical and scientific applications. Existing delivery vehicles are generally limited by the complexity of their design, dependence on active transport, and inability to function within cellular compartments. Here, we developed self-assembled nanofibrous hydrogel fibers using a biologically inert, low-molecular-weight amphiphile. Self-assembled nanofibrous hydrogels offer unique physical/mechanical properties and can easily be loaded with a diverse range of payloads. Unlike commercially available E. coli membrane particles covalently bound to the pH reporting dye pHrodo, pHrodo encapsulated in self-assembled hydrogel-fibers internalizes into macrophages at both physiologic (37°C) and sub-physiologic (4°C) temperatures through an energy-independent, passive process. Unlike dye alone or pHrodo complexed to E. coli, pHrodo-SAFs report pH in both the cytoplasm and phagosomes, as well the nucleus. This new class of materials should be useful for next-generation sensing of the intracellular milieu.