Sarcosine is an amino acid that has been listed as a new indicator for prostate cancer. We present here two low-cost tools with the potential to detect this biomarker excreted in urine. The first one is a paper-based microfluidic device manufactured by wax printing technology in which an enzymatic assay is performed. The enzymatic assay comprises two coupled enzymatic reactions between sarcosine oxidase and horseradish peroxidase, with the ABTS redox indicator oxidized when sarcosine is present in the sample. This enzymatic assay on paper could be used as a preliminary screening method and presents a linear range up to 1 mmol L⁻¹, with a sensitivity of 21.2 A.U. (mmol L⁻¹)⁻¹; LOD = 0.21 mmol L⁻¹; LOQ = 0.61 mmol L⁻¹ and r² = 0.8898. The second bioanalytical approach consists of a capillary electrophoresis method with capacitively coupled contactless conductivity detection (CE-C⁴D). This method proved to be useful to separate sarcosine from 12 amino acids typically found in normal human urine using 10 mmol L⁻¹ of triethylamine (TEA) as the background electrolyte. This method could be used as a follow-up method after the initial screening and presented a stable baseline, LOD = 0.034 mmol L⁻¹ and LOQ = 0.069 mmol L⁻¹. Migration time reproducibility (RSD) for intraday and inter-day assays was smaller than 0.6% and 4.4%, respectively. Both tools were able to analyze this potential tumor marker for prostate cancer, with capabilities of miniaturization and low-cost, essential characteristics for point-of-care testing (POCT) technology. Paper-based devices are inexpensive and simple, making them ideal for screening tests and telemedicine, while separation by CE-C⁴D presents high sensitivity and throughput, useful characteristics for exploratory studies.

Congenital anomalies are already the second cause of infant mortality in Brazil, as in many other middle-income countries in Latin America. Birth defects are a result of both genetic and environmental factors, but a multifactorial etiology has been more frequently observed. Here, we address the environmental causes of birth defects – or teratogens – as a public health issue and present their mechanisms of action, categories and their respective maternal-fetal deleterious effects. We also present a survey from 2008 to 2013 of Brazilian cases involving congenital anomalies (annual average of 20,205), fetal deaths (annual average of 1,530), infant hospitalizations (annual average of 82,452), number of deaths of hospitalized infants (annual average of 2,175), and the average cost of hospitalizations (annual cost of $7,758). Moreover, we report on Brazilian cases of teratogenesis due to the recent Zika virus infection, and to the use of misoprostol, thalidomide, alcohol and illicit drugs. Special attention has been given to the Zika virus infection, now proven to be responsible for the microcephaly outbreak in Brazil, with 8,039 cases under investigation (from October 2015 to June 2016). From those cases, 1,616 were confirmed and 324 deaths occurred due to microcephaly complications or alterations on the central nervous system. Congenital anomalies impact life quality and raise costs in specialized care, justifying the classification of teratogens as a public health issue.

Paper-based devices are an excellent match for low-cost point-of-care testing (POCT) tools. Their user-friendliness, portability, and short time of analysis, coupled with ease of local manufacture make these devices the best option for inexpensive diagnostic testing tools. However, despite all their positive features, these low-cost diagnostic devices must present good performance indicators, such as sensitivity, specificity, and accuracy. We developed and validated a paper-based ELISA for toxoplasmosis diagnosis through the detection of Toxoplasma gondii immunoglobulin G (IgG) antibodies in 100 human serum samples. From among the different ways to define the cut-off value, we chose Youden's J index (cut-off = 21.73 A.U.), which presented a higher sensitivity value. Our paper-based assay presented a sensitivity of 0.96, a specificity of 0.87, and a gray zone comprising 16 samples (±15% of the cut-off value, with 3 false positive outputs). The accuracy of the test was estimated by using ROC curves (AUC = 0.97). We also created a macro in Microsoft Excel® to estimate the accuracy of the test (m-Accuracy) based on a non-parametric method, which evidenced a value = 0.88, which classifies our test as moderately to highly accurate. We also provide the m-Accuracy macro for download and the paper-based microplate designs for printing, in order to collaborate with the scientific community and facilitate further studies using this platform. The improvement of these diagnostic tools can bring this technology for those who need it, contributing to population health and well-being.