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Trust, Manchester M20 9BX, UK; 2Department of Surgical Gastroenterology, Manchester Royal Infirmary, Manchester M13 9WL, UK.Summary Low-level direct electric current has been shown to be capable of destroying tumour tissue. Using an early-passage subcutaneous murine mammary carcinoma, the relationships between the volume of tumour destruction, charge and polarity have been examined. The results revealed a direct correlation between charge passed and absolute volume regression when the intratumoral electrode was made either an anode or a cathode. Tumour destruction for a given charge was significantly greater following anodic than cathodic treatment. A direct correlation was also observed between the percentage volume of prompt treatment-induced regression and the in situ end point of tumour growth delay. During the course of these experiments, a highly reproducible toxic effect was discovered, which has not been previously reported for this modality. An anodic charge greater than 10.6 coulombs or a cathodic charge greater than 21.6 coulombs resulted in 100% mortality at 24-72 h, while lower charges had no influence on mortality. Quantitative assays of a number of blood parameters showed that mortality was associated with serum electrolyte imbalances and appeared to be the result of the metabolic load of tumour breakdown products. These effects are similar to the tumour lysis or surgical crush syndromes and should not constitute a significant problem in clinical practice, where the tumour mass to total body mass ratio will normally be much smaller.Direct current therapy (DCT) offers considerable promise as a low-cost, minimally invasive anti-tumour treatment. While the tissue-destructive effects of low, direct electrical currents have been known for many years, development of a clinically acceptable therapy has been slow, hindered, for example, by uncertainties regarding the quantitation of the dose-response relationship. Our previous qualitative study demonstrated that both anodic and cathodic treatments caused prompt and massive tumour necrosis (Dodd et al., 1993). The present work provides an absolute and relative quantitation of the extent of tumour regression/necrosis with charge and polarity. In common with previous workers, we noted that tumour lysis and volume decrease was extremely rapid after DCT. For other therapies, it has been observed clinically that an undesirable 'tumour lysis syndrome' may result in these circumstances (van der Hoven et al., 1992). Accordingly, we also examine here the potential systemic consequences of treating tumours by DCT. Materials and methodsAll procedures to be described complied with the Animals (Scientific Procedures) Act 1986 (UK). Male B6DF21 (Paterson) mice, 6-8 weeks old, weight approximately 25 g, were inoculated subcutaneously with a suspension of cells from a low-passage, syngeneic murine mammary carcinoma, T50/80 (Moore, 1988). Tumours were treated by DCT 6-10 weeks after inoculation when they were approximately spherical and 6-1O mm in diameter. Tumour size was...

Advanced in vitro culture from tissues of different origin includes three-dimensional (3D) organoid micro structures that may mimic conditions in vivo. One example of simple 3D culture is spheroids; ball shaped structures typically used as liver and tumour models. Oxygen is critically important in physiological processes, but is difficult to quantify in 3D culture: and the question arises, how small does a spheroid have to be to have minimal micro-environment formation? This question is of particular importance in the growing field of 3D based models for toxicological assessment. Here, we describe a simple non-invasive approach modified for the quantitative measurement and subsequent evaluation of oxygen gradients in spheroids developed from a non-malignant fish cell line (i.e. RTG-2 cells) using Electron Paramagnetic Resonance (EPR) oximetry. Sonication of the paramagnetic probe Lithium phthalocyanine (LiPc) allows for incorporation of probe particulates into spheroid during its formation. Spectra signal strength after incorporation of probe into spheroid indicated that a volume of 20 μl of probe (stock solution: 0.10 mg/mL) is sufficient to provide a strong spectra across a range of spheroid sizes. The addition of non-toxic probes (that do not produce or consume oxygen) report on oxygen diffusion throughout the spheroid as a function of size. We provide evidence supporting the use of this model over a range of initial cell seeding densities and spheroid sizes with the production of oxygen distribution as a function of these parameters. In our spheroid model, lower cell seeding densities (∼2,500 cells/spheroid) and absolute size (118±32 μm) allow control of factors such as pre-existing stresses (e.g. ∼ 2% normoxic/hypoxic interface) for more accurate measurement of treatment response. The applied methodology provides an elegant, widely applicable approach to directly characterize spheroid (and other organoid) cultures in biomedical and toxicological research.

It is well-established that exposure of aqueous suspensions of titanium dioxide (TiO(2)) nanoparticles to ultraviolet A (UVA) light produces reactive oxygen species which leads to biological damage. However, there is disagreement in the literature as to the exact nature of these species and how they are formed. Using a number of different spin traps (i.e. PBN, POBN, DMPO, DEPMPO), we have shown that the primary damaging species produced on irradiation of an aqueous suspension of TiO(2) is the hydroxyl radical, which is formed at the valence band hole under both aerobic and hypoxic conditions. Hydroxyl radical production is enhanced by the presence of oxygen which probably reacts with the conduction band electrons or resultant Ti(3+), inhibiting hole-electron recombination, although we find no evidence of reaction of oxygen to form free superoxide radical anions or of the formation of any other radical at that site. The present results suggest that the resulting O(2)(•-) species may not be as labile as previously thought and may possibly undergo further reduction to the O(2)(2-) dianion. Hydroxyl radicals formed at the surface of the TiO(2) readily react with substrates containing an abstractable hydrogen to produce secondary radicals that, in biological systems, could lead to cell damage.