Dot-Elisa for evaluation of hydatid cyst wall, protoscoleces and hydatid cyst fluid antigens in the serodiagnosis of cystic echinococcosis

The aim of the present study is to evaluate cyst wall and protoscolex as an alternate source of antigen in serodiagnosis of cystic echinococcosis (CE). A total of 90 blood samples, 30 each of confirmed CE cases, disease controls and healthy controls were collected. Dot-ELISA using cyst wall, protoscolex and cyst fluid were used to demonstrate anti-hydatid antibodies. The sensitivity of Dot-ELISA using cyst wall, protoscolex and cyst fluid was 96.66%, 86.66% and 93.33% respectively and the specificity of the assay was 70% for Dot-ELISA using cyst fluid, protoscolex and cyst wall antigens. Results of the present study show that cyst wall and protoscolex can also be an useful source of antigen in detection of hydatid antibodies in the serodiagnosis of CE.

Frequency of human toxocariasis in a rural population from Cajamarca, Peru determined by DOT-ELISA test

The aim of this study was to estimate the frequency of human toxocariasis in Cauday district, Cajamarca, Peru, using a dot-ELISA test. From June to October 2005, a total of 256 adult subjects were studied. Blood samples were collected for serology by a dot-ELISA test and for hematological examination. Parasitological examination was also carried out in stool samples to check cross-reactions in the dot-ELISA. The frequency observed was 44.92%, with a significant higher proportion of positivity in male subjects. From subjects with positive serology, 45.6% had respiratory symptoms, 40.44% abdominal pain, 32.35% hepatic symptoms, 14.7% cutaneous signs, 13.23% ocular manifestations, 43.38% eosinophilia, and all of these were statistically associated to serology. Among the population evaluated, 90.23% (231/256) were parasitized. From subjects with positive serology, 92.17% had at least one intestinal parasite and the most frequent were: Blastocystis hominis (68.38%), Giardia lamblia (28.68%), Hymenolepis nana (20.0%), Ascaris lumbricoides (15.65%), Entamoeba histolytica/E. dispar (13.24%), Cyclospora cayetanensis (4.41%), Cryptosporidium sp. (1.47%), Enterobius vermicularis (0.87%), Strongyloides stercoralis (0.87%), Taenia sp. (0.87%), and Trichuris trichiura (0.87%). The rate of false positives in the dot-ELISA test was improved by serum absorption each with A. suum antigens, with a decrease of cross-reactions. In conclusion, human toxocariasis is highly frequent in this population and some risk factors like dog/cat ownership, presence of pets within house, and previous history of geophagia were observed in the present study.

IgG AVIDITY WESTERN BLOT USING Toxoplasma gondii rGRA-7 CLONED FROM NUCLEOTIDES 39-711 FOR SERODIAGNOSIS OF ACUTE TOXOPLASMOSIS

Toxoplasmosis is an important cause of congenital infection. The present study was performed to evaluate the usefulness of recombinant (r) GRA-7 cloned from nucleotides (n) 39-711 in discriminating between acute and chronic toxoplasmosis. First, commercial IgM, IgG and IgG avidity ELISAs were used to determine the serological profile of the sera. Serum samples were from 20 symptomatic patients with acute infection (low IgG avidity, IgM positive), 10 with chronic infection (high IgG avidity, IgM negative) and 10 with indeterminate IgG avidity (IgM positive) which were tested for IgG avidity status with an in-house developed IgG avidity Western blot using the rGRA-7 recombinant antigen. All 20 sera from cases of probable acute infection showed bands which either faded out completely or reduced significantly in intensity after treatment with 8 M urea, whereas the band intensities of the 10 serum samples from chronic cases remained the same. Of the 10 sera with indeterminate IgG avidity status, after treatment with 8 M urea the band intensities with six sera remained the same, two sera had completely faded bands and another two sera had significantly reduced band intensities. Discrimination between acute and chronic toxoplasmosis was successfully performed by the in-house IgG avidity Western blot.

Dot enzyme-linked immunosorbent assay (dot-ELISA) for schistosomiasis diagnosis using dacron as solid-phase

Dacron and nitrocellulose were evaluated as matrices for the dot enzyme linked immunosorbent assay (dot-ELISA) for schistosomiasis and compared to indirect immunofluorescence (IMF). Titration of sera from 18 schistosomiasis patients against soluble worm antigen preparation (SWAP) was carried out and sera from healthy individuals from non-endemic areas were used as controls. The IMF was less sensitive than the dot-ELISAs, although the difference was not statistically significant (p > 0.05). The dot-ELISA based on nitrocellulose was as sensitive as that using dacron. Stability did not differ between nitrocellulose and dacron. Specificity was lower when dacron was used than when nitrocellulose was used, although the difference was not statistically significant (p > 0.05). In conclusion, this work showed that nitrocellulose and dacron performed similarly in dot-ELISA, suggesting that they may be used alternatively in population surveillance in endemic areas.

Observações sobre o TESA blot no diagnóstico sorológico da doença de Chagas

Comparamos o TESA blot com a hemaglutinação indireta, imunofluorescência indireta e ELISA. Nos 30 soros de pessoas infectadas pelo Trypanosoma cruzi, as quatro técnicas foram positivas em todos, e nos 30 não-infectados, totalmente negativas. Nos soros indeterminados e nos de leishmaniose visceral, comprovamos muitas positividades falsas, em quantidade bastante menor com o TESA blot.

Solution processed quantum dot photodetectors

To find sustainable solutions for the production of energy, it is necessary to create photovoltaic technologies that make every photon count. To pursue this necessity, in the present work photodetectors of zinc oxide embedded with nano-structured materials, that significantly raise the conversion of solar energy to electric energy, were developed. The novelty of this work is on the development of processing methodologies in which all steps are in solution: quantum dots synthesis, passivation of their surface and sol-gel deposition. The quantum dot solutions with different capping agents were characterized by UVvisible absorption spectroscopy, spectrofluorimetry, dynamic light scattering and transmission electron microscopy. The obtained quantum dots have dimensions between 2 and 3nm. These particles were suspended in zinc acetate solutions and used to produce doped zinc oxide films with embedded quantum dots, whose electric response was tested. The produced nano-structured zinc oxide materials have a superior performance than the bulk, in terms of the produced photo-current. This indicates that an intermediate band material should have been produced that acts as a photovoltaic medium for solar cells. The results are currently being compiled in a scientific article, that is being prepared for possible submission to Energy and Environmental Science or Nanoscale journals.

Strain induced edge magnetism at zigzag edge of a graphene quantum dot

We study the temperature dependent magnetic susceptibility of a strained graphene quantum dot by using the determinant quantum Monte Carlo method. Within the Hubbard model on a honeycomb lattice, our unbiased numerical results show that a relative small interaction $U$ may lead to a edge ferromagnetic like behavior in the strained graphene quantum dot, and a possible room temperature transition is suggested. Around half filling, the ferromagnetic fluctuations at the zigzag edge is strengthened both markedly by the on-site Coulomb interaction and the strain, especially in low temperature region. The resultant strongly enhanced ferromagnetic like behavior may be important for the development of many applications.

El ensayo inmunoenzimatico en microgotas sobre nitrocelulosa (Dot-ELISA) en el diagnostico de la enfermedad de Chagas: I. Estudio comparativo de dos preparaciones antigenicos de Trypanosoma cruzi

Se estudia el Ensayo Inmunoenzimático en Microgotas sobre Nitrocelulosa (Dot-ELISA)comparando dos preparados antigénicos de formas epimastigotas de cultivo de T. cruzi: 1) la fracción citoplasmática (antígeno citoplasmático y 2) el parásito total fijado previamente con formaldehido (antígeno integral). Se usaron sueros de: 95 pacientes chagásicos con serología convencional positiva, cardiopatía crónica y algunos con xenodiagnóstico positivo; 42 personas sanas y 32 con miocardipatía crónica con serología negativa y 74 pacientes con diferentes patologías incluyendo: sífilis, toxoplasmosis, lupus eritematoso diseminado, con factor reumatoide, leishmaniasis visceral, y leishmaniasis cutánea. Definidos los títulos diagnósticos (cut-off) de 1:512 con antígeno citoplasmático y de 1: 128 con antígeno integral, la especificidad fue 96% para el primero y de 100% para el segundo; mientras que la sensibilidad fue de 100% para ambas. En el estudio comparativo con las pruebas serológicas convencionales examinando 147 sueros tomados de personas referidas al laboratório, Dot-ELISA con antígeno citoplasmático presentó índices deco-positividad de 1,0, co-negatividad de 0,989 y eficiencia 0,993. Dot-ELIS con antígeno integral dió 1,0, 0,979 y 0,986 respectivamente. De acuerdo con esta evaluación, la técnica Dot-ELISA con antígeno integral se presenta como una alternativa práctica para el diagnóstico serológico de la enfermedad de Chagas.

El ensayo inmunoenzimatico en microgotas sobre nitrocelulosa (Dot-ELISA) en el diagnostico de la enfermedad de Chagas: II. Estudio seroepidemiologico en cuatro comunidades rurales de Venezuela

Se realizó estudio seroepidemiológico sobre la infección por Trypanosoma cruzi en habitantes de cuatro comunidades rurales de Venezuela, que presentan diferentes situaciones epidemiológicas en relación a la Enfermedad de Chagas, con la finalidad de evaluar la técnica de Dot-ELISA y compararla con las pruebas serológicas convencionales. En los caseríos de Kamana y caño Hondo del estado Zulia, donde no existe transmisión, la seropositividad fue 15,7% en adultos solamente. En las comunidades de las Rosas y Solano del estado Cojedes, área de alta endemicidad, la seropositividad en los menores de 14 años fue 8,9% y en los mayores de 15,51,6%. En el estudio comparativo con las pruebas serolgicas convencionlaes, Dot-ELISA presentó altos índices de co-positividad, co-negatividad y eficiencia. El valor predictivo positivo de la prueba fue de 66% y 60% con al antígeno citoplasmático e integral respectivamente, en el estado Zulia y 100% y 95% en el estado Cojedes. Estos resultados sugieren que Dot-ELISA puede ser una alternativa práctica para estudios seroepidemiológicos sobre la infección por Trypanosoma cruzi en los paises en desarrollo.

The use of dacron plates for DOT enzyme-linked immunosorbent assay (DOT-ELISA)

Dacron (polyethylenetherephthalate) is proposed as a matrix for dot-ELISA procedures, as an alternative to nitrocellulose. Plates of dacron were partially hydrazinolyzed and hydrazide groups introduced were converted to azide groups. The derivative dacron-antigen was covalently linked on to the plates through these azide groups. The derivative dacron-antigen was exaustively washed according to CROOK and antigen was still fixed onto the plates. Protein F1A purified from Yersinia pestis was used as a model. Triration of sera from immunized and non immunized rabbits against this protein was carried out by employing the dot-ELISA method. No significant difference was observed using dacron-antigen and nitrocellulose-antigen preparations. However, both procedures showed to have a significant better performance in comparasion with the passive hemagglutination method. The specificity and reproductibility of the dot-ELISA assay using both preparations showed a similar behaviour. Nitrocellulose preparation was stable at 4ºC, 28ºC and -20ºC for 90 days, whereas the dacron-antigen derivative was stable only when stored at 4ºC. Dacron-antigen derivative could be re-used when the spot developing was proceeded using 4-chloro-1-naphtol as substrate.

Dot-dye-immunoassay for the diagnosis of schistosomiasis mansoni

A new serological assay dot-dye-immunoassay (dot-DIA) was evaluated for the diagnosis of schistosomiasis mansoni. This method consist of four steps: (a) biding of antigens to a nitrocellulose membrane (NC); (b) blocking of free sites of the NC; (c) incubation in specific primary antibody; (d) detection of primary antibody reactivity by color development using second antibody coupled to textile dyes. Sera from 82 individuals, 61 with Schistosoma mansoni eggs in the stool and 21 stool negative were tested by ELISA, dot-ELISA, and dotDIA. A high level of agreement between the methods tested was observed for all sera tested: ELISA x dot-ELISA: 95.1%, ELISA x dot-DIA: 92.7% and dot-ELISA x dot-DIA: 97.6%. In this study, dot-DIA proved to be a feasible, sensitive, rapid and practical test for the diagnosis of shcistosomiasis.