Anti-aquaporin-4 immunoglobulin G colorimetric detection by silver nanoparticles

Neuromyelitis optica spectrum disorder (NMOSD) is an inflammatory and autoimmune disease whose biomarker is the anti-AQP4-IgG autoantibody that binds to aquaporin-4 (AQP4) protein. We introduced a nanosensor with a sensitivity of 84.6%, higher than the CBA's 76.5%. Using silver nanoparticles (AgNPs), we detected not only seropositive but also some false-negative patients previously classified with CBA. It consisted of AgNPs coated with one of a panel of 5 AQP4 epitopes. The ability in detecting the anti-AQP4-IgG in NMOSD patients depended on the epitope and synergy could be obtained by combining different epitopes. We demonstrated that NMOSD patients could easily be distinguished from healthy subjects and patients with multiple sclerosis. Using the most sensitive AQP4_61-70 peptide, we established a calibration curve to estimate the concentration of anti-AQP4-IgG in seropositive NMOSD patients. The ability to enhance the accuracy of the diagnosis may improve the prognosis of 10-27% of anti-AQP4-IgG seronegative patients worldwide.

Immobilization and unbinding investigation of the antigen-antibody complex using theoretical and experimental techniques

Experimental results for the antibody known as immunoglobulin G - IgG interacting with phenobarbital were obtained via atomic force microscopy (AFM) and thereafter investigated using computer simulation modeling tools. Using molecular dynamics simulation and docking calculations, the energetically stable configurations of an immobilized antibody over a silicon surface were searched. Six stable configurations of the immobilized antibody over the silicon nitride surface covered by linker molecules were found. Although, only three of them (P1, P2, P5) maintained the Fragment antigen binding available for antigen interaction. Therefore, these configurations were equilibrated after reaching 100 ns molecular dynamics trajectory. The average interaction energy between the surface and the immunoglobulin G - IgG antibody in the P1, P2 and P5 configurations were -62.4 ± 2.4 kcal/mol; -54.3 ± 5.7 kcal/mol, and -360.9 ± 4.2 kcal/mol respectively. Phenobarbital was docked within the Fab domain of P1, P2, and P5 immobilized configurations and equilibrated with molecular dynamics for binding energy estimation. Then, steered molecular dynamics was performed to evaluate unbinding energy pathway between phenobarbital and IgG in each of the three-oriented IgG configurations. No significant differences were observed in the rupture force values (EP1 = 591 ± 13 pN, EP2 = 605 ± 18 pN, and EP5 = 610 ± 45 pN). In comparison, the average AFM experimental results were (641.6 ± 363.3 pN). Therefore, it is worth noting that P5 is the configuration with highest protein-surface interaction. Therefore, the force value calculated for the P5 orientation is statistically more favorable and it is the one to be compared to the experimental data. The agreement between experimental and theoretical results indicates a favorable presented for this study opening new perspectives for antigen-antibody evaluation.

Nanobiosensors exploiting specific interactions between an enzyme and herbicides in atomic force spectroscopy

The development of sensitive methodologies for detecting agrochemicals has become important in recent years due to the increasingly indiscriminate use of these substances. In this context, nanosensors based on atomic force microscopy (AFM) tips are useful because they provide higher sensitivity with operation at the nanometer scale. In this paper we exploit specific interactions between AFM tips functionalized with the enzyme acetolactate synthase (ALS) to detect the ALS-inhibitor herbicides metsulfuron-methyl and imazaquin. Using atomic force spectroscopy (AFS) we could measure the adhesion force between tip and substrate, which was considerably higher when the ALS-functionalized tip (nanobiosensor) was employed. The increase was approximately 250% and 160% for metsulfuron-methyl and imazaquin, respectively, in comparison to unfunctionalized probes. We estimated the specific enzyme-herbicide force by assuming that the measured force comprises an adhesion force according to the Johnson-Kendall-Roberts (JKR) model, the capillary force and the specific force. We show that the specific, biorecognition force plays a crucial role in the higher sensitivity of the nanobiosensor, thus opening the way for the design of similarly engineered tips for detecting herbicides and other analytes.

Eye pigments of the blood-sucking insect, Triatoma infestans klug (Hemiptera, Reduviidae)

The pigmentation of black (wild) and red (mutant) eyes of Triatoma infestans was studied spectrophotometrically and compared with red-eyed (wild) and white-eyed (mutant) forms of Drosophila melanogaster. The spectral absorption profiles of the black and red eye pigments of T. infestans were similar to each other and to that of the wild-type eyes of D. melanogaster. The similarity to the wild form of D. melanogaster indicated that both eye forms of T. infestans contained ommochromes of the xanthommatin type, a finding confirmed by ascending paper chromatography. Pteridines, melanins, and ommins were not detected as eye pigments in T. infestans. The eye color difference in T. infestans was assumed to be a function of the xanthommatin concentration, with a smaller content of ommochrome in red eyes, although this probably did not affect the insect's visual acuity. These data support other findings regarding the similarities between black- and red-eyed specimens of T. infestans for other characteristics.

Trypanosoma evansi control and horse mortality in the Brazilian Pantanal

The impact of three treatment strategies for Trypanosoma evansi control on horse mortality in the Brazilian Pantanal based on four size categories of cattle ranches is explored. The region's 49,000 horses are indispensable to traditional extensive cattle ranching and T. evansi kills horses. About 13% of these horses would be lost, annually, due to T. evansi if no control were undertaken. One preventive and two curative treatment strategies are financially justifiable in the Pantanal. The best available technology for the treatment of T. evansi from a horse mortality perspective is the preventive strategy, which spares 6,462 horses, annually. The year-round cure spares 5,783 horses, and the seasonal cure saves 5,204 horses on a regional basis relative to no control strategy. Regardless of the strategy adopted, 39% of the costs or benefits fall to the largest ranches, while 18% fall to the smallest ranches.

A financial analysis of treatment strategies for Trypanosoma evansi in the Brazilian Pantanal

The Brazilian Pantanal is a 138,000 km2 tropical seasonal wetland located in the center of South America bordering Bolivia and Paraguay. The Pantanal contains approximately 1100 cattle ranches, 3 million cattle, 49,000 horses and a unique diversity of wildlife. Cattle ranching is the most important economic activity in the Pantanal. This study explores the direct financial impacts of the adoption of seven treatment strategies for the control of Trypanosoma evansi in the Brazilian Pantanal. T. evansi adversely affects the health of the horse population in the region. Horses are indispensable to the cattle ranching industry in the Pantanal. Estimated costs include risk of infection, costs of diagnosis, alternative treatments, collecting animals for treatment, and costs of animal losses. The estimated total cost of T. evansi to the Pantanal region's cattle ranchers is about US$2.4 million and 6462 horses/yr. Results indicate that one preventive and two curative treatment strategies are financially justifiable. The best available technology for the treatment of T. evansi from an economic perspective is a curative treatment employed year-round. This treatment represents an annual net benefit of more than US$2 million or US$1845/ranch and spares about 5783 horses. It represents an annual net benefit of over US$200,000 and 600 horses relative to the currently most widely adopted strategy.