Identifying abnormalities in red blood cells can provide important medical clues for the diagnosis, prognosis, and treatment of some health disorders. A common test used to examine the conditions of erythrocytes in humans is osmotic fragility. The standard technique to determine the osmotic fragility of red blood cells is laborious and time-consuming, and provides only approximate values with a few experimental data. In this work, we propose and investigate a way to measure the osmotic fragility of erythrocytes, rapidly and in a straightforward, more quantitative and less laborious way, with an optical sensor. The basic idea is monitoring in real time the refractive index of a suspension of erythrocytes to follow the kinetics of their lysis as the hemoglobin-rich cytosol is released from the erythrocytes in the surrounding hypotonic solution during hemolysis, resulting in an increase of the refractive index. We propose a device to measure in real time the refractive index and demonstrate the feasibility of monitoring the hemolysis process with high resolution. Our results show that the release of hemoglobin-rich cytosol during the progress of the hemolysis of erythrocytes in hypotonic media is generally an exponential-like function of time. We provide a mathematical model that reproduces experimental curves effectively. We show results for erythrocytes obtained from human blood stored in a blood bank and from volunteers diagnosed with two different types of anemia: hemolytic and drepanocytic. We define times, measurable from the kinetics of the refractive index signal, to quantify the progress of hemolysis as a possible new method of measuring osmotic fragility.

Today, visual classification of the degree of lipemia in blood samples is frequently performed in clinical laboratories. However, achieving standardization of this classification at low cost and with fewer resources is an objective that is still under development. In this work, a comparison is made between the visual inspection and optical measurements of blood plasma for quantifying lipemia. The plasma refractive index’s real part was measured using an Abbe refractometer and transmittance measurements were made at a 589 nm wavelength and wavelengths ranging from 320 to 1100 nm in the spectral region, respectively. Taking the slope of the transmittance spectrum at two specific wavelengths, it is possible to establish a more standardized selection criterion and implement it quickly using low-cost optical devices. Furthermore, using the proposed transmittance-spectrum-slope method, statistically significant differences (p < 0.05) were found between healthy blood samples and lipemia 1, 2, 3, and 4. However, there were no statistical differences between lipemia 1 and 2.

This study presents an extensive evaluation of the accuracy of the anomalous diffraction approximation in modeling light scattering by small particles, covering a broad range of particle sizes and refractive indices typical of biological systems. To the best of our knowledge, no comprehensive study has assessed the approximation’s accuracy across multiple relevant optical scattering parameters for biological particles. We present detailed maps that highlight the relative error of the anomalous diffraction approximation across various particle scattering calculations. The goal of this work is to offer a more thorough understanding of the approximation’s accuracy in modeling light scattering by individual particles than has been previously explored.

Detecting alterations in the electrical response of human biofluids can provide valuable information in the early stages on pathological conditions in a patient. Developing techniques for obtaining rapid information on the electrical resistivity of common ionic biofluids by non-invasive techniques can improve medicare through a rapid and more precise diagnosis. In this work, we analyze the use of an electrical device consisting of a cell formed of flat parallel steel plates to measure the resistivity of these substances. When the electrical cell is filled with a biofluid an electrical double layer (EDL) is formed on the electrodes/biofluid interface. Then, we measure the electrical response and examine the general conditions under which the EDL does not interfere with the assesment of the biofluid’s resistivity. The electrical response is analyzed in terms of an equivalent circuit model. Also, a simplified theoretical model of a suspension of biological cells considering spherical particles with a membrane is discussed to validate measurements and theoretically exhibit the contribution of the cell’s membrane to the effective resistivity. We present measurements of the resistance of the electrical cell filled with electrolyte solutions, blood plasma, and diluted suspensions of erythrocytes in a hypotonic solution. Results show that the resistance of the electrical cell is sensitive to the volume density of biological cells suspended between the parallel plate electrodes, producing a signal with a high signal to noise ratio. From the measured resistance of a suspension of erythrocytes in a isotoinc solution and the simplified theoretical model, we estimate the value of the conductivity of the interior of the erythrocytes. The results show that measured resistance varies with blood samples and hemolysis progression. The device’s sensitivity to the number of erythrocytes passing between the electrodes makes it useful for measuring sedimentation kinetics.