In this study, we assessed the cytotoxic effect of 1,3-diphenyl-2-allyl-1,3-propanedione (DPAP) on B16F10 and Tm5 melanoma cells and investigated its interaction with DNA (deoxyribonucleic acid) using optical tweezers. The compound showed to be effective against B16F10 cells with selectivity index (SI) of 7.92 and interaction to the outer surface of the double helix, probably at the minor groove of DNA. This likely induced a bending deformation of the polymer chain, decreasing persistence length, and indicated that each DPAP molecule occupies a single base pair upon binding to the double helix.

Leptospirosis is a zoonotic disease caused by bacteria of the genus Leptospira, which can cause lipid changes in the erythrocyte membrane. Optical tweezers were used to characterize rheological changes in erythrocytes from patients with leptospirosis in the late stage. Biochemical methods were also used for quantification of plasma lipid, erythrocyte membrane lipid, and evaluation of liver function. Our data showed that the mean elastic constant of erythrocytes from patients with leptospirosis was around 67% higher than the control (healthy individuals), indicating that patient’s erythrocytes were less elastic. In individuals with leptospirosis, several alterations in relation to control were observed in the plasma lipids, however, in the erythrocyte membrane, only phosphatidylcholine showed a significant difference compared to control, increasing around 41%. With respect to the evaluation of liver function of individuals with leptospirosis, there was a significant increase in levels of alanine transaminase (154%) and aspartate transaminase (150%), whereas albumin was 43.8% lower than control (P<0.01). The lecithin-cholesterol acyltransferase fractional activity was 3.6 times lower in individuals with leptospirosis than in the healthy individuals (P<0.01). The decrease of the erythrocyte elasticity may be related to the changes of erythrocyte membrane phospholipids composition caused by disturbances that occur during human leptospirosis, with phosphatidylcholine being a strong candidate in the erythrocyte rheological changes.

Racional : Apendicite aguda é a emergência cirúrgica mais comum na prática diária, sendo em muitos centros, abordada por laparoscopia. Esforços têm sido voltados para o desenvolvimento de técnicas minimamente invasivas, reduzindo o trauma tecidual e melhorando os resultados cosméticos, dentre essas, a "single incision laparoscopic surgery" (SILS). Objetivo : Apresentar técnica minimamente invasiva para apendicectomia com incisão única e com instrumentos convencionais. Método : Onze pacientes foram atendidos em serviço de emergência devido à dor abdominal em fossa ilíaca direita sugestiva de apendicite. Procedeu-se a investigação diagnóstica, incluindo exames físico, laboratoriais e de imagem (tomografia computadorizada com contraste venoso ou ecografia de abdome total), cujos resultados foram compatíveis com apendicite aguda. Assim, após consentimento, esses pacientes foram submetidos à apendicectomia por SILS, sob anestesia geral, com dois trocárteres de 10 mm e um de 5 mm, com uso de pinças laparoscópicas convencionais e ótica de 10 mm e 30 º. A base e o pedículo do apêndice foram ligados com clipes de titânio LT 400, sem intercorrências. Critérios de inclusão foram pacientes com apendicite aguda mas sem peritonite generalizada com índice de massa corpórea menor que 35 e ausência de comorbidades graves e ou sepse. Resultados : Foram operados sete homens e quatro mulheres com idade média de 25,7 anos com esta técnica. A duração média do procedimento foi de 37,2 min. Em relação aos achados cirúrgicos, três pacientes apresentavam apendicite em fase 1, quatro em fase 2 e quatro em fase 3. Todos evoluíram bem, sem complicações cirúrgicas e não houve necessidade de conversão da operação para técnica aberta ou mesmo para laparoscopia convencional. Conclusão : Apendicectomia por "single Incision Laparoscopic Surgery" é técnica viável e promissora, podendo ser realizada com instrumentos da laparoscopia convencionais.

Background : Acute appendicitis is the most common surgical emergency in daily practice, and is approached laparoscopically in many centers. Efforts have been undertaken for the development of minimally invasive techniques that reduce tissue trauma and offer improved cosmetic results, one of such being the single-incision laparoscopic surgery (SILS). Aim : To present a minimally invasive technique for appendectomy (SILS) undertaken with conventional instruments. Method : Eleven patients were treated in the emergency care center presenting abdominal pain in the right iliac fossa that was suggestive of appendicitis. Diagnostic investigation was subsequently conducted, including physical examination, laboratory and imaging exams (CT scan with intravenous contrast or total abdominal ultrasound), and the results were consistent with acute appendicitis. Thus, after consent, these patients underwent SILS appendectomy under general anesthesia with three trocars (two 10 mm and one 5 mm), using conventional and optical laparoscopic tweezers (10 mm, 30º). The base and pedicle of the appendix were ligated with titanium LT 400 clips. The procedure occurred uneventfully. Inclusion criteria were absence of diffuse peritonitis, BMI (body mass index) less than 35 and absence of serious comorbidities or sepsis. Results : Seven men and four women were operated with average age of 25.7 years and underwent appendectomy through this technique. Mean procedure duration was of 37.2 min. Regarding surgical findings, three had appendicitis in stage 1, four in stage 2 and four in stage 3. All patients improved well, without surgical complications, and did not require conversion to open surgery or conventional laparoscopy technique. Conclusion : Appendectomy conducted through Single Incision Laparoscopic Surgery is a feasible and promising technique that can be performed with conventional laparoscopic instruments.

It is now well known that matter may be trapped by optical fields with high intensity gradients. Once trapped, it is then possible to manipulate microscopic particles using such optical fields, in so-called optical tweezers. Such optical trapping and tweezing systems have found widespread application across diverse fields in science, from applied biology to fundamental physics. In this article we outline the design and construction of an optical trapping and tweezing system, and show how the resulting interaction of the laser light with microscopic particles may be understood in terms of the transfer of linear and angular momentum of light. We demonstrate experimentally the use of our optical tweezing configuration for the measurement of microscopic forces and torques. In particular, we make use of digital holography to create so-called vortex laser beams, capable of transferring orbital angular momentum to particles. The use of such novel laser beams in an optical trapping and tweezing set-up allows for the control of biological species at the single-cell level.

Hemagglutination is widely used in transfusion medicine and depends on several factors including antigens, antibodies, electrical properties of red blood cells and the environment of the reaction. Intermolecular forces are involved in agglutination with cell clumping occurring when the aggregation force is greater than the force of repulsion. Repulsive force is generated by negative charges on the red blood cell surface that occur due to the presence of the carboxyl group of sialic acids in the cell membrane; these charges create a repulsive electric zeta potential between cells. In transfusion services, specific solutions are used to improve hemagglutination, including enzymes that reduce the negative charge of red blood cells, LISS which improves the binding of antibodies to antigens and macromolecules that decrease the distance between erythrocytes. The specificity and sensitivity of immunohematological reactions depend directly on the appropriate use of these solutions. Knowledge of the electrical properties of red blood cells and of the action of enhancement solutions can contribute to the immunohematology practice in transfusion services.

Optical experimental devices allow to observe and manipulate several micron-sized objects, for instance, condensed phase domains formed in Langmuir monolayers at the air/water interface. In this paper, an experimental instrument designed to trap and manipulate those domains is presented. This instrument consists of optical tweezers, colloidal beads as handles and Brewster angle microscopy (BAM) to observe the trapped domains. With this instrument it was possible to trap and observe small domains (20 - 30 μm) of nervonic acid monolayers.

Los dispositivos experimentales ópticos permiten observar y manipular diversos objetos de escalas microscópicas como, por ejemplo, dominios de fases condensadas formados en monocapas de Langmuir en la intercara aire/agua. En este artículo se presenta un instrumento experimental diseñado para atrapar y manipular dichos dominios utilizando pinzas (ópticas, microesferas coloidales como sujetadores y microscopía de ángulo de Brewster (MAB) para observarlos. Con este instrumento fue posible atrapar y observar dominios pequeños (20 - 30 μm) de monocapas de ácido nervónico.

Apresentamos uma revisão de duas novas técnicas para estudar propriedades biofísicas de moléculas únicas e células únicas. Um laser incidindo em uma objetiva de microscópio de grande abertura numérica é capaz de aprisionar pequenas partículas dielétricas na região próxima ao foco. Este aparato é chamado de pinça óptica. Esta técnica tem a grande vantagem de permitir a manipulação de um objeto individual. Usamos a pinça óptica para medir a elasticidade entrópica de uma molécula única de DNA em sua interação com o fármaco Psoralen. A pinça óptica também é usada para segurar uma célula renal MDCK fora do substrato, permitindo medidas precisas do volume dessa célula única durante um choque osmótico. Este processo nos permite obter informações sobre a permeabilidade osmótica da membrana e o crescimento do volume regulatório. A microscopia de desfocalização é uma técnica recente inventada em nosso laboratório, que nos permite observar objetos transparentes simplesmente desfocalizando o microscópio de uma maneira controlada. Nosso modelo físico de um microscópio desfocalizado mostra que o contraste da imagem observado neste caso é proporcional à distância da desfocalização e à curvatura do objeto transparente. A microscopia de desfocalização é muito útil para estudar a motilidade e as propriedades mecânicas das células. Mostramos aqui a aplicação da microscopia de desfocalização em medidas de flutuações na superfície de macrófagos e sua influência na fagocitose.

We present a review on two new tools to study biophysical properties of single molecules and single cells. A laser incident through a high numerical aperture microscope objective can trap small dielectric particles near the focus. This arrangement is named optical tweezers. This technique has the advantage to permit manipulation of a single individual object. We use optical tweezers to measure the entropic elasticity of a single DNA molecule and its interaction with the drug Psoralen. Optical tweezers are also used to hold a kidney cell MDCK away from the substrate to allow precise volume measurements of this single cell during an osmotic shock. This procedure allows us to obtain information about membrane water permeability and regulatory volume increase. Defocusing microscopy is a recent technique invented in our laboratory, which allows the observation of transparent objects, by simply defocusing the microscope in a controlled way. Our physical model of a defocused microscope shows that the image contrast observed in this case is proportional to the defocus distance and to the curvature of the transparent object. Defocusing microscopy is very useful to study motility and mechanical properties of cells. We show here the application of defocusing microscopy to measurements of macrophage surface fluctuations and their influence on phagocytosis.