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One of the greatest challenges for science nowadays is the protection of the natural environment. Synthetic nanoparticles are released into the environment with industrial and household wastes, and their release can be expected to increase constantly with increasing use of nanoparticles in industry and their increasing share in various consumer products. The penetration of nanoparticles into the water, soil, or air ecosystems may disturb seriously the functioning of the natural environment. In the present study we examined how the active aluminum nano-oxide in the gamma form used as a neutral carrier for the praseodymium (Pr) nanoparticles affected their behavior. Praseodymium is very useful in many branches of science and in everyday life, although in its free form, it is commonly considered to be cyto-toxic, eco-toxic, and phyto-toxic. Our experiments were aimed to find whether the aluminum nano-oxide can act as a nano-stabilizer for the metal nanoparticles, and also to examine whether their bounding on the carrier decreases or eliminates their toxicity to the soil or water microorganisms present in the natural environment. Our experiments have shown that the aluminum nano-oxide is suitable to function as a nano-stabilizer for the Pr nanoparticles. The Al2O3/Pr nanoparticles produced by the dry (conducted in an organic solvent) thermal decomposition of an organic precursor, are not ecotoxic, or less ecotoxic to bacteria isolated from environmental samples, in particular to gram-positive caryopsis of the Micrococcus and Staphylococcus genera isolated from air samples.

Ion-selective electrodes can either be classified according to the membrane material used or the type of electrode body arrangement. Both classifications show that neutral carrier-based liquid membrane microelectrodes represent a very special type of electrode out of a vast variety of sensors. The unique features of carrier membranes as well as those of microelectrode bodies clearly illustrate the advantages of this type of electrode for intracellular studies in electrophysiology.

Liquid membranes based on classical anion exchangers normally exhibit roughly the same selectivity sequence with a preference for lipophilic and a rejection of hydrophilic anions [6]. The same holds for the response to cations of electrodes based on classical liquid cation exchangers, e.g., tetraphenylborates [12]. This is in contrast to neutral carrier membrane systems for cations where the ion selectivity is highly dependent on the free energy of the interaction of the ions with the ligand [1, 8]. If neutral carriers for anions are incorporated into solvent polymeric membranes, a wide variety of ion selectivities is expected to be made accessible [13].

The widespread use of neutral carrier-based microelectrodes in physiology is illustrated in Tab. 10.1. Only selected contributions are given so that the list is far from complete. The 230 examples disclose several aspects and trends in the applications of neutral carrier-based microelectrodes.

Ion-selective electrodes permit the potentiometric measurement of the activity of a given ion in the presence of other ions. Two general arrangements of potentiometric liquid membrane electrode cells are shown in Fig. 5.1. The ion-selective electrode consists of a galvanic half-cell containing the liquid membrane, the internal filling solution and the internal reference electrode. The other half-cell is represented by an external reference electrode in contact with a reference electrolyte. Such a cell assembly is described in (Eq. 5.1)

The introduction [1] of a reliable liquid membrane ion-selective micropipette (ISM) for H+ has opened up an important new window onto ion and metabolic homeostasis in brain tissue. Formerly, glass membrane ISMs were commonly used [14], but frequently the response was too slow to capture H+ transients. They were also difficult to fabricate as double-barrelled electrodes, i. e., with an integral reference barrel [2]. An alternative type of ISM for H+ employed antimony as the sensor and has been variously configured (e.g., [5]). This sensor, however, is subject to a variety of ill-defined interferences [10]. The liquid membrane ISM overcomes virtually all the deficiencies of previous sensors (note, however, that dinitrophenol and presumably other lipophilic proton transporting anions, destabilize the ISM). We have made an extensive study of pH changes in the cerebellar microenvironment of the in vivo rat [4]. More recently, we have studied the microenvironment of the in vitro turtle cerebellum. We shall draw on both these studies here.

The central nervous system (CNS) of both vertebrates and invertebrates comprises three compartments: the intracellular media of nerve and of glial cells, and the extracellular space. The composition of each of these three compartments can be quite variable, and may even change within the same system during activity [1,7]. The regulation of ion activities in all three compartments seems to be essential for proper neuronal functioning [2,14]. It follows that a study concerned with ionic homeostasis in the CNS should take into account all three compartments.

The alterations in brain extracellular ionic composition during spreading depression (SD), anoxia, ischemia, and profound hypoglycemia have been clarified to a large extent through the use of double-barrelled liquid ion exchanger (LIX) microelectrodes. Recently, a neutral carrier H+- LIX has become available, permitting examination of the extracellular pH (pHe) changes associated with these events [1, 9]. Construction of pH microelectrodes with this exchanger provide the specific advantages of double-barreled LIX microelectrodes, i. e., small tip diameters (2–4 pm as used in these studies), an immediately adjacent reference electrode, and rapid transient response (90% response in ≤ 2 s). We examined the pHe changes during SD and also the pHe changes during events which are initiated by altered substrate supplies, i. e., cerebral ischemia, terminal anoxia, and profound hypoglycemia (the hypoglycemia experiments are work in progress by W. A. C. Mutch in association with A. R. Gardner-Medwin).