Histogram analysis for smartphone-based rapid hematocrit determination

Quantification of Blood Viscoelasticity under Microcapillary Blood Flow

Blood elasticity is quantified using a single compliance model by analyzing pulsatile blood flow. However, one compliance coefficient is influenced substantially by the microfluidic system (i.e., soft microfluidic channels and flexible tubing). The novelty of the present method comes from the assessment of two distinct compliance coefficients, one for the sample and one for the microfluidic system. With two compliance coefficients, the viscoelasticity measurement can be disentangled from the influence of the measurement device. In this study, a coflowing microfluidic channel was used to estimate blood viscoelasticity. Two compliance coefficients were suggested to denote the effects of the polydimethylsiloxane (PDMS) channel and flexible tubing (C1), as well as those of the RBC (red blood cell) elasticity (C2), in a microfluidic system. On the basis of the fluidic circuit modeling technique, a governing equation for the interface in the coflowing was derived, and its analytical solution was obtained by solving the second-order differential equation. Using the analytic solution, two compliance coefficients were obtained via a nonlinear curve fitting technique. According to the experimental results, C2/C1 is estimated to be approximately 10.9-20.4 with respect to channel depth (h = 4, 10, and 20 µm). The PDMS channel depth contributed simultaneously to the increase in the two compliance coefficients, whereas the outlet tubing caused a decrease in C1. The two compliance coefficients and blood viscosity varied substantially with respect to homogeneous hardened RBCs or heterogeneous hardened RBCs. In conclusion, the proposed method can be used to effectively detect changes in blood or microfluidic systems. In future studies, the present method can contribute to the detection of subpopulations of RBCs in the patient's blood.

Analysis of Polarization Images in the Microphysical Blood Parameters Research for the Hematocrit Diagnostics

The development of non-invasive optoelectronic technologies for human blood monitoring is one of the important research areas for medicine. A critical analysis of optoelectronic methods of blood research and the micromechanical systems based on them is carried out in this article. A design realization of a polarizing portable system for non-invasive monitoring of hematocrit as one of the basic homeostatic constants of the human body containing information about the microphysical parameters of blood cells has been substantiated. A physical model of polarized radiation conversion in a video information system of laser sensing of a biological research object has been formed. Visual and quantitative differences in the spatial distribution of polarization parameters of the scattered radiation for the states of the body with different hematocrit levels have been revealed. A scheme of a multichannel imaging portable system, based on a smartphone using miniature optical and microelectronic components of information conversion for non-invasive monitoring of microphysical blood parameters, has been created. The system implements the principle of polarimetric blood photometry and a multiparametric analysis of the polarization properties of the laser radiation scattered by blood. The developed portable optoelectronic system, based on a smartphone, can be used for rapid blood diagnostics in disaster medicine and the presence of clinical contraindications to the formation of invasive tests. The proposed polarization-based approach is a promising automated alternative to traditional devices and systems for the research of microphysical blood parameters.

Back to the "Gold Standard": How Precise is Hematocrit Detection Today?

Introduction

The commonly used method for hematocrit detection, by visual examination of microcapillary tube, known as “micro-HCT”, is subjective but remains one of the key sources for fast hematocrit evaluation. Analytical automation techniques have increased the standardization of RBC index detection; however, indirect hematocrit measurements by blood analyzer, the automated HCT, do not correlate well with “micro-HCT” results in patients with hematological pathologies. We aimed to overcome those disadvantages in “micro-HCT” analysis using “ImageJ” processing software.

Methods

223 blood samples from the “general population” and 19 from sickle cell disease patients were examined in parallel for hematocrit values using the automated HCT, standard “micro-HCT,” and “ImageJ” micro-HCT methods.

Results

For the “general population” samples, the “ImageJ” values were significantly higher than the corresponding values evaluated by standard “micro-HCT” and automated HCT, except for the 0 to 2 month old newborns, in which the automated HCT results were similar to the “ImageJ” evaluated HCT. Similar to the “general population” cohort, we found significantly higher values measured by “ImageJ” compared to either “micro-HCT” or the automated HCT in SCD patients. Correspondent differences for the MCV and MCHC were also found.

Discussion

This study introduces the “micro-HCT” assessment technique using the image-analysis module of “ImageJ” software. This procedure allows overcoming most of the data errors associated with the standard “micro-HCT” evaluation and can replace the use of complicated and expensive automated equipment. The presented results may also be used to develop new standards for calculating hematocrit and associated parameters for routine clinical practice.

Smartphone-Integrated Label-Free Rapid Screening of Anemia from the Pattern Formed by One Drop of Blood on a Wet Paper Strip

Screening of anemic patients poses demanding challenges in extreme point-of-care settings where the gold standard diagnostic technologies are not pragmatic and the alternative point-of-care technologies suffer from compromised accuracy, prohibitive cost, process complexity, or reagent stability issues. As a disruption to this paradigm, here, we report the development of a smartphone-based sensor for rapid screening of anemic patients by exploiting the patterns formed by a spreading drop of blood on a wet paper strip wherein blood attempts to displace a more viscous fluid, on the porous matrix of a paper, leading to "finger-like" projections at the interface. We analyze the topological features of the pattern via smartphone-enabled image analytics and map the same with the relative occupancy of the red blood cells in the blood sample, allowing for label-free screening and classification of blood samples corresponding to moderate to severe anemic conditions. The accuracy of detection is verified by comparing with gold standard reports of hematology analyzer, showing a strong correlation coefficient (R²) of 0.975. This technique is likely to provide a crucial decision-making tool that obviates delicate reagents and skilled technicians for supreme functionality in resource-limited settings.

Microfluidic-Based Novel Optical Quantification of Red Blood Cell Concentration in Blood Flow

The optical quantification of hematocrit (volumetric percentage of red blood cells) in blood flow in microfluidic systems provides enormous help in designing microfluidic biosensing platforms with enhanced sensitivity. Although several existing methods, such as centrifugation, complete blood cell count, etc., have been developed to measure the hematocrit of the blood at the sample preparation stage, these methods are impractical to measure the hematocrit in dynamic microfluidic blood flow cases. An easy-to-access optical method has emerged as a hematocrit quantification technique to address this limitation, especially for the microfluidic-based biosensing platform. A novel optical quantification method is demonstrated in this study, which can measure the hematocrit of the blood flow at a targeted location in a microchannel at any given instant. The images of the blood flow were shot using a high-speed camera through an inverted transmission microscope at various light source intensities, and the grayscale of the images was measured using an image processing code. By measuring the average grayscale of the images of blood flow at different luminous exposures, a relationship between hematocrit and grayscale has been developed. The quantification of the hematocrit in the microfluidic system can be instant and easy with this method. The innovative proposed technique has been evaluated with porcine blood samples with hematocrit ranging from 5% to 70%, flowing through 1000 µm wide and 100 µm deep microchannels. The experimental results obtained strongly supported the proposed optical technique of hematocrit measurement in microfluidic systems.

Sequential quantification of blood and diluent using red cell sedimentation-based separation and pressure-induced work in a microfluidic channel

The erythrocyte sedimentation method has been widely used to detect inflammatory diseases. However, this conventional method still has several drawbacks, such as a large blood volume (∼1 mL) and difficulty in continuous monitoring. Most importantly, image-based methods cannot quantify RBC-rich blood (blood) and RBC-free blood (diluent) simultaneously. In this study, instead of visualizing interface movement in the blood syringe, a simple method is proposed to quantify blood and diluent in microfluidic channels sequentially. The hematocrit was set to 25% to enhance RBC sedimentation and form two layers (blood and diluent) in the blood syringe. An air cavity (∼300 μL) inside the blood syringe was secured to completely remove dead volumes (∼200 μL) in fluidic paths (syringe needle and tubing). Thus, a small blood volume (V_b = 50 μL) suctioned into the blood syringe is sufficient for supplying blood and diluent in the blood channel sequentially. The relative ratio of blood resident time (RBC-to-diluent separation) was quantified using λ_b, which was obtained by quantifying the image intensity of blood flow. After the junction pressure (P_j) and blood volume (V) were obtained by analyzing the interface in the coflowing channel, the averaged work (W_p [Pa mm³]) was calculated and adopted to detect blood and diluent, respectively. The proposed method was then applied with various concentrations of dextran solution to detect aggregation-elevated blood. The W_p of blood and diluent exhibited substantial differences with respect to dextran solutions ranging from C_dex = 10 to C_dex = 40 mg mL^-1. Moreover, λ_b did not exhibit substantial differences in blood with C_dex > 10 mg mL^-1. The variations in λ_b were comparable to those of the previous method based on interface movement in the blood syringe. In conclusion, the W_P could detect blood as well as diluents more effectively than λ_b. Furthermore, the proposed method substantially reduced the blood volume from 1 mL to 50 μL.

Artificial Intelligence-Controlled Microfluidic Device for Fluid Automation and Bubble Removal of Immunoassay Operated by a Smartphone

There have been tremendous innovations in microfluidic clinical diagnostics to facilitate novel point-of-care testing (POCT) over the past decades. However, the automatic operation of microfluidic devices that minimize user intervention still lacks reliability and repeatability because microfluidic errors such as bubbles and incomplete filling pose a major bottleneck in commercializing the microfluidic devices for clinical testing. In this work, for the first time, various states of microfluid were recognized to control immunodiagnostics by artificial intelligence (AI) technology. The developed AI-controlled microfluidic platform was operated via an Android smartphone, along with a low-cost polymer device to effectuate enzyme-linked immunosorbent assay (ELISA). To overcome the limited machine-learning capability of smartphones, the region-of-interest (ROI) cascading and conditional activation algorithms were utilized herein. The developed microfluidic chip was incorporated with a bubble trap to remove any bubbles detected by AI, which helps in preventing false signals during immunoassay, as well as controlling the reagents' movement with an on-chip micropump and valve. Subsequently, the developed immunosensing platform was tested for conducting real ELISA using a single microplate from the 96-well to detect the Human Cardiac Troponin I (cTnI) biomarker, with a detection limit as low as 0.98 pg/mL. As a result, the developed platform can be envisaged as an AI-based revolution in microfluidics for point-of-care clinical diagnosis.

Quantitative Monitoring of Dynamic Blood Flows Using Coflowing Laminar Streams in a Sensorless Approach

Determination of blood viscosity requires consistent measurement of blood flow rates, which leads to measurement errors and presents several issues when there are continuous changes in hematocrit changes. Instead of blood viscosity, a coflowing channel as a pressure sensor is adopted to quantify the dynamic flow of blood. Information on blood (i.e., hematocrit, flow rate, and viscosity) is not provided in advance. Using a discrete circuit model for the coflowing streams, the analytical expressions for four properties (i.e., pressure, shear stress, and two types of work) are then derived to quantify the flow of the test fluid. The analytical expressions are validated through numerical simulations. To demonstrate the method, the four properties are obtained using the present method by varying the flow patterns (i.e., constant flow rate or sinusoidal flow rate) as well as test fluids (i.e., glycerin solutions and blood). Thereafter, the present method is applied to quantify the dynamic flows of RBC aggregation-enhanced blood with a peristaltic pump, where any information regarding the blood is not specific. The experimental results indicate that the present method can quantify dynamic blood flow consistently, where hematocrit changes continuously over time.

Fully integrated rapid microfluidic device translated from conventional 96-well ELISA kit

In this work, a fully integrated active microfluidic device transforming a conventional 96-well kit into point-of-care testing (POCT) device was implemented to improve the performance of traditional enzyme-linked immunosorbent assay (ELISA). ELISA test by the conventional method often requires the collection of 96 samples for its operation as well as longer incubation time from hours to overnight, whereas our proposed device conducts ELISA immediately individualizing a 96-well for individual patients. To do that, a programmable and disposable on-chip pump and valve were integrated on the device for precise control and actuation of microfluidic reagents, which regulated a reaction time and reagent volume to support the optimized protocols of ELISA. Due to the on-chip pump and valve, ELISA could be executed with reduced consumption of reagents and shortening the assay time, which are crucial for conventional ELISA using 96-well microplate. To demonstrate highly sensitive detection and easy-to-use operation, this unconventional device was successfully applied for the quantification of cardiac troponin I (cTnI) of 4.88 pg/mL using a minimum sample volume of 30 µL with a shorter assay time of 15 min for each ELISA step. The limit of detection (LOD) thus obtained was significantly improved than the conventional 96-well platform.

O. Microfluidic Point-of-Care Devices: New Trends and Future Prospects for eHealth Diagnostics

Point-of-care (PoC) diagnostics is promising for early detection of a number of diseases, including cancer, diabetes, and cardiovascular diseases, in addition to serving for monitoring health conditions. To be efficient and cost-effective, portable PoC devices are made with microfluidic technologies, with which laboratory analysis can be made with small-volume samples. Recent years have witnessed considerable progress in this area with "epidermal electronics", including miniaturized wearable diagnosis devices. These wearable devices allow for continuous real-time transmission of biological data to the Internet for further processing and transformation into clinical knowledge. Other approaches include bluetooth and WiFi technology for data transmission from portable (non-wearable) diagnosis devices to cellphones or computers, and then to the Internet for communication with centralized healthcare structures. There are, however, considerable challenges to be faced before PoC devices become routine in the clinical practice. For instance, the implementation of this technology requires integration of detection components with other fluid regulatory elements at the microscale, where fluid-flow properties become increasingly controlled by viscous forces rather than inertial forces. Another challenge is to develop new materials for environmentally friendly, cheap, and portable microfluidic devices. In this review paper, we first revisit the progress made in the last few years and discuss trends and strategies for the fabrication of microfluidic devices. Then, we discuss the challenges in lab-on-a-chip biosensing devices, including colorimetric sensors coupled to smartphones, plasmonic sensors, and electronic tongues. The latter ones use statistical and big data analysis for proper classification. The increasing use of big data and artificial intelligence methods is then commented upon in the context of wearable and handled biosensing platforms for the Internet of things and futuristic healthcare systems.

Blood Viscoelasticity Measurement Using Interface Variations in Coflowing Streams under Pulsatile Blood Flows

Blood flows in microcirculation are determined by the mechanical properties of blood samples, which have been used to screen the status or progress of diseases. To achieve this, it is necessary to measure the viscoelasticity of blood samples under a pulsatile blood condition. In this study, viscoelasticity measurement is demonstrated by quantifying interface variations in coflowing streams. To demonstrate the present method, a T-shaped microfluidic device is designed to have two inlets (a, b), one outlet (a), two guiding channels (blood sample channel, reference fluid channel), and one coflowing channel. Two syringe pumps are employed to infuse a blood sample at a sinusoidal flow rate. The reference fluid is supplied at a constant flow rate. Using a discrete fluidic circuit model, a first-order linear differential equation for the interface is derived by including two approximate factors (F₁ = 1.094, F₂ = 1.1087). The viscosity and compliance are derived analytically as viscoelasticity. The experimental results showed that compliance is influenced substantially by the period. The hematocrit and diluent contributed to the varying viscosity and compliance. The viscoelasticity varied substantially for red blood cells fixed with higher concentrations of glutaraldehyde solution. The experimental results showed that the present method has the ability to monitor the viscoelasticity of blood samples under a sinusoidal flow-rate pattern.

Microfluidic-Based Biosensor for Sequential Measurement of Blood Pressure and RBC Aggregation Over Continuously Varying Blood Flows

Aggregation of red blood cells (RBCs) varies substantially depending on changes of several factors such as hematocrit, membrane deformability, and plasma proteins. Among these factors, hematocrit has a strong influence on the aggregation of RBCs. Thus, while measuring RBCs aggregation, it is necessary to monitor hematocrit or, additionally, the effect of hematocrit (i.e., blood viscosity or pressure). In this study, the sequential measurement method of pressure and RBC aggregation is proposed by quantifying blood flow (i.e., velocity and image intensity) through a microfluidic device, in which an air-compressed syringe (ACS) is used to control the sample injection. The microfluidic device used is composed of two channels (pressure channel (PC), and blood channel (BC)), an inlet, and an outlet. A single ACS (i.e., air suction = 0.4 mL, blood suction = 0.4 mL, and air compression = 0.3 mL) is employed to supply blood into the microfluidic channel. At an initial time (t < 10 s), the pressure index (PI) is evaluated by analyzing the intensity of microscopy images of blood samples collected inside PC. During blood delivery with ACS, shear rates of blood flows vary continuously over time. After a certain amount of time has elapsed (t > 30 s), two RBC aggregation indices (i.e., S_EAI: without information on shear rate, and erythrocyte aggregation index (EAI): with information on shear rate) are quantified by analyzing the image intensity and velocity field of blood flow in BC. According to experimental results, PI depends significantly on the characteristics of the blood samples (i.e., hematocrit or base solutions) and can be used effectively as an alternative to blood viscosity. In addition, S_EAI and EAI also depend significantly on the degree of RBC aggregation. In conclusion, on the basis of three indices (two RBC aggregation indices and pressure index), the proposed method is capable of measuring RBCs aggregation consistently using a microfluidic device.

Microfluidic Adapter Converting a 96-Well Cartridge into an Autonomous Microfluidic Device

In this study, an immunosensing platform by integrating a single array of conventional 96-well cartridges with low-cost polydimethylsiloxane (PDMS) pillars and thermoplastic chip was designed and developed to execute enzyme-linked immunosorbent assay (ELISA). The platform provides multiple (eight) reaction chambers for sequentially detecting multiple analytes under similar assay environments. For multiple immunoassays, the reaction chambers are consequently activated using a microvalve integrated with the sensing zones via the thermoplastic chip. Because the reaction zones are able to be selected and isolated from each other by the microvalve, multiple immunoassays can be implemented, avoiding cross-contamination. The performance of the sensing platform demonstrated its effectiveness in assaying with an optimal sample volume of 10 μL with an assay time of 10-15 min for different assay steps, which is much lower than the conventional immunoassay using 96-well plates. Thus, a low detection limit of 9.75 pg/mL is achieved using the developed platform to successfully detect the cardiac troponin I (cTnI). As a result, the cost-effectively made PDMS pillars and 96-well cartridge based hybrid immunosensing platform are widely applicable for high-throughput multiple lab-on-a-chip immunoassays.

Impact of big data on oral health outcomes

Biomedical big data amasses from different sources such as electronic health records, health research, wearable devices and social media. Recent advances in data capturing, storage and analysis techniques have facilitated conversion of a wealth of knowledge in biomedical big data into evidence-based actionable plans to enhance population health and well-being. The delay in reaping the benefits of biomedical big data in dentistry is mainly due to the slow adoption of electronic health record systems, unstructured clinical records, tattered communication between data silos and perceiving oral health as a separate entity from general health. Recent recognition of the complex interplay between oral and general health has acknowledged the power of oral health big data to glean new insights on disease prevention and management. This review paper summarizes recent advances, limitations and challenges in biomedical big data in health care with emphasis on oral health and discusses the potential future applications of oral health big data to improve the quality and efficiency of personalized health care.

A Disposable Blood-on-a-Chip for Simultaneous Measurement of Multiple Biophysical Properties

Biophysical properties are widely used to detect pathophysiological processes of vascular diseases or clinical states. For early detection of cardiovascular diseases, it is necessary to simultaneously measure multiple biophysical properties in a microfluidic environment. However, a microfluidic-based technique for measuring multiple biophysical properties has not been demonstrated. In this study, a simple measurement method was suggested to quantify three biophysical properties of blood, including red blood cell (RBC) deformability, RBC aggregation, and hematocrit. To demonstrate the suggested method, a microfluidic device was constructed, being composed of a big-sized channel (BC), a parallel micropillar (MP), a main channel, a branch channel, inlet, and outlets. By operating a single syringe pump, blood was supplied into the inlet of the microfluidic device, at a periodic on-off profile (i.e., period = 240 s). The RBC deformability index (DI) was obtained by analyzing the averaged blood velocity in the branch channel. Additionally, the RBC aggregation index (AIN) and the hematocrit index (HiBC) were measured by analyzing the image intensity of blood flows in the MP and the BC, respectively. The corresponding contributions of three influencing factors, including the turn-on time (Ton), the amplitude of blood flow rate (Q₀), and the hematocrit (Hct) on the biophysical indices (DI, AIN, and HiBC) were evaluated quantitatively. As the three biophysical indices varied significantly with respect to the three factors, the following conditions (i.e., Ton = 210 s, Q₀ = 1 mL/h, and Hct = 50%) were maintained for consistent measurement of biophysical properties. The proposed method was employed to detect variations of biophysical properties depending on the concentrations of autologous plasma, homogeneous hardened RBCs, and heterogeneous hardened RBCs. Based on the observations, the proposed method exhibited significant differences in biophysical properties depending on base solutions, homogeneous hardened RBCs (i.e., all RBCs fixed with the same concentration of glutaraldehyde solution), and heterogeneous hardened RBCs (i.e., partially mixed with normal RBCs and homogeneous hardened RBCs). Additionally, the suggested indices (i.e., DI, AIN, and HiBC) were effectively employed to quantify three biophysical properties, including RBC deformability, RBC aggregation, and hematocrit.

A disposable on-chip microvalve and pump for programmable microfluidics

In this work, a low-cost PDMS micro-pump and -valve have been designed and developed to control multiple reagents for enzyme-linked immunosorbent assay (ELISA) on a programmable lab-on-a-chip (LOC) platform. The micro pump and valves were precisely controlled by selectively pressurizing the PDMS channels and chamber to actuate the multiple reagents in a controlled manner. Selective pressurizing of the PDMS structures was initiated by a simple system that maneuvered a single roller bar operated by a programmed microprocessor. The performance of the micro-pump was fully characterized and a minimum fluid volume of 1 μL was controlled. Also, the on-chip microvalves were programmed to flow the multiple reagents to automatically process the multi-step ELISA procedures. By applying the proposed platform, 19.40 pg ml-1 cardiac troponin T (cTnT) was successfully detected on the LOC device by using multiple programmed valves as multiple steps of the enzyme-linked sandwich immunoassay. As a result, the developed micro-pump and -valve, which were successfully applied to actuate a series of solutions in a controlled manner, can be widely applied to lab-on-a-chip based bioassays.