High throughput detection and characterization of red blood cells deformability by combining optical tweezers with microfluidic technique / 生物医学工程学杂志

A high throughput measurement method of human red blood cells (RBCs) deformability combined with optical tweezers technology and the microfluidic chip was proposed to accurately characterize the deformability of RBCs statistically. Firstly, the effective stretching deformation of RBCs was realized by the interaction of photo-trapping force and fluid viscous resistance. Secondly, the characteristic parameters before and after the deformation of the single cell were extracted through the image processing method to obtain the deformation index of area and circumference. Finally, statistical analysis was performed, and the average deformation index parameters (

Single Molecule Method for Molecular Biology

In order to understand biological phenomena accurately, single molecule techniques using a physical research approach to molecular interactions have been developed, and are now widely being used to study complex biological processes. In this review, we discuss some of the single molecule methods which are composed of two major parts: single molecule spectroscopy and manipulation. In particular, we explain how these techniques work and introduce the current research which uses them. Finally, we present the oral biology research using the single molecule methods.

Dielectrophoretic force measurement of red blood cells exposed to oxidative stress using optical tweezers and a microfluidic chip

Red blood cell (RBC) dysfunction is often associated with a pathological intervention, and it has been proposed as a critical risk factor for certain lethal diseases. Examining the cell viability of RBCs under various physiological conditions is essential and of importance for precise diagnosis and drug discovery in the field of medicine and pharmacy. In this paper, we report a new analytical method that employs dielectrophoretic (DEP) force measurements in absolute units to assess the viability, and potentially the functionality of RBCs. We precisely quantify the frequency-dependent DEP forces of the RBCs by using a micro-electrode embedded chip combined with optical tweezers. DEP characteristics are known to be well-correlated with the viability of biological cells, and DEP forces are measured in both fresh and long-term stored RBCs to investigate the effect that the storage period has on the cell viability. Moreover, we investigate the DEP behavior of RBCs when exposed to oxidative stress and verify whether EDTA protects the RBCs from an oxidant. From the experiments, it is found that the fresh RBCs without oxidative stress display very high DEP forces over the entire frequency range, exhibiting two cutoff frequencies. However, both the RBCs stored for the long-term period and exposed to oxidative stress reveals that there exist no significant DEP forces over the frequency range. The results indicate that the DEP forces can serve as a useful parameter to verify whether the RBCs in certain blood are fresh and not exposed to oxidative stress. Therefore, it is believed that our system can be applied to a diagnostic system to monitor the cell viability of the RBCs or other types of cells.

Electrical properties of the red blood cell membrane and immunohematological investigation

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.

Uso de pinças ópticas para avaliação do potencial zeta de hemácias em EDTA, CPD-SAGM e estocadas / Use of optical tweezers for evaluation of szeta potential of red blood cells in EDTA, CPD-SAGM and stored in blood banks

A hemácia é carregada negativamente, principalmente devido ao ácido siálico que gera um potencial elétrico denominado Potencial Zeta que impede a aglutinação intravascular. Os testes de hemaglutinação na rotina transfusional, necessitam de substâncias potencializadoras, das quais muitas agem diminuindo o Potencial Zeta para se ter maior sensibilidade. Através da pinça óptica, ferramenta capaz de capturar células utilizando a luz, foi proposta uma metodologia para quantificar o potencial zeta e aplicar em hemácias coletadas com EDTA e estocadas em CPD-SAGM (visando avaliar alterações de cargas da membrana relacionadas a lesões de armazenamento. Os potenciais zeta em CPD-CAGM foram superiores (-14,8 mV) aos em EDTA (-7,9 mV) e decrescentes a partir do primeiro dia de armazenamento, estabilizando-se a partir da terceira semana com potencial zeta -7,6 mV. Hemácias com CPD-SAGM apresentaram potencial zeta maior, pois possivelmente este conservante evitou lesões mais significativas da membrana que poderiam alterar as cargas. A redução do potencial zeta no armazenamento pode ser consequência de enzimas liberadas de leucócitos lisados que tenham alterado as glicoforinas da membrana. A metodologia permitiu avaliar o potencial zeta em diferentes condições e poderá contribuir na padronização de técnicas de hemaglutinação com diferentes meios potencializadores e no melhor conhecimento das lesões de estocagem para fins transfusionais.

Study of P. falciparum-infected erythrocytes and induced anisotropies under optical and fluid forces.

BACKGROUND & OBJECTIVES: The effect of P. falciparum on erythrocytes has been studied for a long time at the population level but actual studies at the single cell level remain largely unexplored. The aim of this study was to address the host-parasite relationship at the single cell level under two different kinds of forces, an optical force and a fluid force. The questions addressed were about the basic host-parasite interactions, but our findings have larger implications in diverse fields of parasite biology. METHODS: Erythrocytes were monitored under optical forces (using optical tweezers) and fluid forces (using microfluidic chambers) and dynamical images were captured in real-time video clips. These videos were then split into their respective frames so as to yield temporal information and various parameters pertaining to membrane structure, ionic imbalance and interaction with different forces were studied. RESULTS: The results of this study mainly bring to fore the inherent differences between infected and normal cell populations at the single cell level under various external forces. We probed three different criteria folding times, rotation speeds and rolling frequency to show inherent difference in various cell populations and also the dependence of the above to the cycle of the parasite. INTERPRETATION & CONCLUSION: This study portrays the importance of single cell observations pertaining to the host-parasite relationship. It shows the effect the malarial parasite has on erythrocytes and how the intrinsic property of the infected and its neighbouring uninfected cells change as compared to normal erythrocytes. There are thus implications in the fields of cytoadherence, parasite invasions and host immune evasion.

Study of Raman spectroscopy of optically trapped human red blood cell affected by direct current / 生物医学工程学杂志

Laser tweezers Raman spectroscopy (LTRS) system is a combination of spectroscopy and laser tweezers; It is a new method of studying cells; It can trap single living cell and make Raman spectrum of single living cell. From the positions, intensities, and line widths of the Raman peaks in the spectra, we can get useful information about composition, structure and interactions of complexes inside the living cells. External agents may change cell's physiological state and this changed information can also be got from Raman spectra. This article is a study of Raman spectra of human red blood cell (RBC) affected by different intensity direct current (DC); from the result, distinct change of Raman spectra of RBC have been got. These changes characterize the changes of the internal information of the cells. This article give some academic reference of physical therapy using DC in the level of molecule.