Introduction: Gold nanoparticles (AuNPs) are often used as biosensors in biological markers and also in diagnostic kits. Spherical shaped AuNPs are red. These nanoparticles have high binding affinity with proteins, antibodies and antigens forming stable bioconjugates. Are widely used in lateral flow immunochromatography platform. Therefore, AuNPs are currently one of the main raw materials used to produce various diagnostic kits, including Sars-CoV-2. The assessment of their correct stability directly affects the customized production and quality of the diagnostics kits.Objectives: Evaluate the stability of in-house prepared gold nanoparticle solutions used in the manufacture of diagnostic tests using statistical methods for determining the appropriate shelf life under established storage conditions. Methodology:In-house based on adapted Turkevish method (1951), a gold nanoparticle (AuNP) solution was synthesized and characterized by ultraviolet-visible spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS), dynamic scattering (DLS) and laser Doppler electrophoresis (LDE). The solution was analyzed at the time of manufacture (T0) and every 15 days for 90 days, under thermal stress conditions. The evaluation of the stability of the AuNP solution was based on the ISO Guide 35, which statistically evaluates the time that significant change occurs of the evaluation parameters, indicating the end of shelf life at a significance level of 0.05. Results:Statistical analysis shows that at T90 days, one of the evaluated parameters showed a significant change at a significance level of 0.05. |b1| > t95%, n-2 * s(b1) and, therefore, there is statistical evidence that proves that the final solution lost stability in this time. Arrhenius equation was used to determine the shelf life. Where, Storage=25°C, Stress=40°C, Activation Energy (Ea)=3, and then: Thermal Kinetic Ratio (Qt) = 5.2. That is, 2.5 months at 40°C is equivalent to 13 months at 25°C. Conclusion:AuNPs produced in-house have a shelf life of 1 month at room temperature. Based on the analysis of the main control parameters and statistical application, the validity attributable to the AuNP solution under study is 13 months at 25°C, bringing great savings to the production process, without loss of quality. New strategies for evaluating the stability of solutions should be considered in the future.
Leishmaniasis is a neglected vector-borne disease with a worldwide distribution. Among its different clinical manifestations, the Visceral Leishmaniasis (VL) is the most severe form, which is caused by Leishmania infantum in Brazil. When not treated properly, it can evolve to death and for this reason, early diagnosis followed by adequate treatment is of upmost importance. Currently, the gold standard diagnostic is the parasitological examination, but it has several disadvantages such as low sensitivity. It is known that diagnostic tests can play a major role in patient management, disease surveillance and epidemiological studies, however, accurate human VL diagnosis remains a world problem.Objectives: Aiming to improve the national public health system, the objective of this study was to evaluate the performance of different antigens in immunochromatographic rapid test platform for serological diagnosis of human VL.Methodology: Three recombinant proteins (A1, B1 and C1) that displayed good performance in the enzyme immunoassay (ELISA) in previous studies were tested in a lateral flow platform. The optimal membrane, buffer and protein quantity per test were assessed to identify the best test condition for each protein. The C1 protein was cut off of the study in this phase due to the incompatibility with all tested buffers. After establishing the parameters for proteins A1 and B1, an internal assessment was conducted. After that, a prototype of each test was sent to external evaluation. Results:In the internal evaluation, 50 positive and 40 negative sera were tested. Another 10 samples positive for Trypanosoma cruzi and negative for VL were tested. The A1 protein obtained a sensitivity of 86% and specificity of 100%. The B1 protein obtained sensitivity of 88% and specificity of 100%. Both proteins did not cross reaction with T. cruzi. In the external evaluation, 48 negative and 52 positive sera were tested. The A1 protein obtained sensitivity of 98% and specificity of 90% and B1 obtained sensitivity of 98% and specificity of 92%. Conclusion:These results indicate a potential applicability of the protein B1 in the field. The rapid detection of L. infantum infection will certainly improve the patient's prognosis, preventing fatal resolutions.
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