Resazurin dye has been broadly used as indicator of cell viability in several types of assays for evaluation of the biocompatibility of medical and dental materials. Mitochondrial enzymes, as carriers of diaphorase activities, are probably responsible for the transference of electrons from NADPH + H+ to resazurin, which is reduced to resorufin. The level of reduction can be quantified by spectrophotometers since resazurin exhibits an absorption peak at 600 ηm and resorufin at 570 ηm wavelengths. However, the requirement of a spectrophotometer and specific filters for the quantification could be a barrier to many laboratories. Digital cameras containing red, green and blue filters, which allow the capture of red (600 to 700 ηm) and green (500 to 600 ηm) light wavelengths in ranges bordering on resazurin and resorufin absorption bands, could be used as an alternative method for the assessment of resazurin and resorufin concentrations. Thus, our aim was to develop a simple, cheap and precise method based on a digital CCD camera to measure the reduction of resazurin. We compared the capability of the CCD-based method to distinguish different concentrations of L929 and normal Human buccal fibroblast cell lines with that of a conventional microplate reader. The correlation was analyzed through the Pearson coefficient. The results showed a strong association between the measurements of the method developed here and those made with the microplate reader (r² = 0.996; p < 0.01) and with the cellular concentrations (r² = 0.965; p < 0.01). We concluded that the developed Colorimetric Quantification System based on CCD Images allowed rapid assessment of the cultured cell concentrations with simple equipment at a reduced cost.

Background: Since successful treatment of superficial bladder cancer with BCG requires proper induction of Th1 immunity, we have developed a rBCG-S1PT strain that induced a stronger cellular immune response than BCG. This preclinical study was designed to compare the modulatory effects of BCG and rBCG-S1PT on bladder TNF-α and IL-10 expression and to evaluate antitumour activity. Methods: For Experiment I, the MB49 bladder cancer cell line was used in C57BL/6 mice. Chemical cauterization of the bladder was performed to promote intravesical tumor implantation. Mice were treated by intravesical instillation with BCG, rBCG-S1PT or PBS once a week for four weeks. After 35 days the bladders were removed and weighed. TNF-〈 and IL-10 cytokine responses were measured by qPCR. Experiment II was performed in the same manner as Experiment I, except the animals were not challenged with MB49 tumor cells. Results: rBCG-S1PT immunotherapy resulted in bladder weight reduction, compared to the BCG and control group. There were increases in TNF-α in the BCG-treated group, as well as increases in TNF-α and IL-10 mRNA in the rBCG-S1PT group. Conclusion: These data indicate a significant reduction of bladder tumor volume for the rBCG group, compared to the BCG and PBS groups. This suggests that rBCG could be a useful substitute for wild-type BCG and that the potential modulation between TNF-α and IL-10 cytokine productions may have therapeutic value.

Toxicity studies in mammals continue to be the most appropriate model for predicting risk in humans, but they tend to be expensive and time-consuming. In the aftermath of the genetic sequencing of zebrafish (Danio rerio), this species is highly genetically homologous to humans. The use of the zebrafish model to assess food toxicity is already a reality as it is capable of biological processes difficult to reproduce in vitro. Studies of complex mechanisms of absorption, distribution, metabolism, and excretion as well as cellular and tissue interactions are of great information value resulting in time, space and cost savings, when compared to studies with rodents. This review addresses the relevance of zebrafish model in food safety research, both in the use of ingredients and approved and generally recognized as safe food additives as well as for establishing levels of safe food contaminant residues present in the environment. Toxicological screening using the zebrafish model integrate the evaluation of teratogenicity, cardiotoxicity, hepatotoxicity, genotoxicity, neurotoxicity, endocrine toxicity, reproductive and behavioral aspects. These are important endpoints for food safety assessment, which take substantially less time than in mammalian tests. Furthermore, it serves well as a screening test follow-up for validating favorable results in murine models, hence accelerating the risk assessment process of products submitted for approval and registration, prioritizing safe compounds and reducing unnecessary costs in subsequent mammalian studies. In conclusion, the zebrafish model can be a useful tool for food safety tests; however, additional studies are needed to further validate this model for registration of new food ingredients and additives.