Multiparameter Affinity Microchip for Early Sepsis Diagnosis Based on CD64 and CD69 Expression and Cell Capture

Microfluidic systems for infectious disease diagnostics

Microorganisms, encompassing both uni- and multicellular entities, exhibit remarkable diversity as omnipresent life forms in nature. They play a pivotal role by supplying essential components for sustaining biological processes across diverse ecosystems, including higher host organisms. The complex interactions within the human gut microbiota are crucial for metabolic functions, immune responses, and biochemical signalling, particularly through the gut-brain axis. Viruses also play important roles in biological processes, for example by increasing genetic diversity through horizontal gene transfer when replicating inside living cells. On the other hand, infection of the human body by microbiological agents may lead to severe physiological disorders and diseases. Infectious diseases pose a significant burden on global healthcare systems, characterized by substantial variations in the epidemiological landscape. Fast spreading antibiotic resistance or uncontrolled outbreaks of communicable diseases are major challenges at present. Furthermore, delivering field-proven point-of-care diagnostic tools to the most severely affected populations in low-resource settings is particularly important and challenging. New paradigms and technological approaches enabling rapid and informed disease management need to be implemented. In this respect, infectious disease diagnostics taking advantage of microfluidic systems combined with integrated biosensor-based pathogen detection offers a host of innovative and promising solutions. In this review, we aim to outline recent activities and progress in the development of microfluidic diagnostic tools. Our literature research mainly covers the last 5 years. We will follow a classification scheme based on the human body systems primarily involved at the clinical level or on specific pathogen transmission modes. Important diseases, such as tuberculosis and malaria, will be addressed more extensively.

Combined CD25, CD64, and CD69 Biomarker in 3D-Printed Multizone Millifluidic Device for Sepsis Detection in Clinical Samples

Sepsis is a serious medical condition that arises from a runaway response to an infection, which triggers the immune system to release chemicals into the bloodstream. This immune response can result in widespread inflammation throughout the body, which may cause harm to vital organs and, in more severe cases, lead to organ failure and death. Timely and accurate diagnosis of sepsis remains a challenge in analytical diagnostics. In this work, we have developed and validated a sepsis detection device, utilizing 3D printing technology, which incorporates multiple affinity separation zones. Our device requires minimal operator intervention and utilizes CD64, CD69, and CD25 as the biomarker targets for detecting sepsis in liquid biopsies. We assessed the effectiveness of our 3D-printed multizone cell separation device by testing it on clinical samples obtained from both septic patients (n = 35) and healthy volunteers (n = 8) and validated its performance accordingly. Unlike previous devices using poly(dimethyl siloxane), the 3D-printed device had reduced nonspecific binding for anti-CD25 capture, allowing this biomarker to be assayed for the first time in cell separations. Our results showed a statistically significant difference in cell capture between septic and healthy samples (with p values of 0.0001 for CD64, CD69, and CD25), suggesting that 3D-printed multizone cell capture is a reliable method for distinguishing sepsis. A receiver operator characteristic (ROC) analysis was performed to determine the accuracy of the captured cell counts for each antigen in detecting sepsis. The ROC area under the curve (AUC) values for on-chip detection of CD64+, CD69+, and CD25+ leukocytes were 0.96, 0.92, and 0.88, respectively, indicating our diagnostic test matches clinical outcomes. When combined for sepsis diagnosis, the AUC value for CD64, CD69, and CD25 was 0.99, indicating an improved diagnostic performance due to the use of multiple biomarkers.

An autonomous microchip for real-time, label-free immune cell analysis

Characterization of cell populations and identification of distinct subtypes based on surface markers are needed in a variety of applications from basic research and clinical assays to cell manufacturing. Conventional immunophenotyping techniques such as flow cytometry or fluorescence microscopy require immunolabeling of cells, expensive and complex instrumentation, skilled operators, and are therefore incompatible with field deployment and automated cell manufacturing systems. In this work, we introduce an autonomous microchip that can electronically quantify the immunophenotypical composition of a cell suspension. Our microchip identifies different cell subtypes by capturing each in different microfluidic chambers functionalized against the markers of the target populations. All on-chip activity is electronically monitored by an integrated sensor network, which informs an algorithm determining subpopulation fractions from chip-wide immunocapture statistics in real time. Moreover, optimal operational conditions within the chip are enforced through a closed-loop feedback control on the sensor data and the cell flow speed, and hence, the antibody-antigen interaction time is maintained within its optimal range for selective immunocapture. We apply our microchip to analyze a mixture of unlabeled CD4⁺ and CD8⁺ T cell sub-populations and then validated the results against flow cytometry measurements. The demonstrated capability to quantitatively analyze immune cells with no labels has the potential to enable not only autonomous biochip-based immunoassays for remote testing but also cell manufacturing bioreactors with built-in, adaptive quality control.

High-recovery sorting of cancer cells from whole blood via periodic-focusing inertial microchip

Inertial microfluidic devices continue to show promise for label-free separation of cells from liquid biopsies and other biological samples.

Toward Rapid Detection of Viable Bacteria in Whole Blood for Early Sepsis Diagnostics and Susceptibility Testing

Sepsis is a serious bloodstream infection where the immunity of the host body is compromised, leading to organ failure and death of the patient. In early sepsis, the concentration of bacteria is very low and the time of diagnosis is very critical since mortality increases exponentially with every hour after infection. Common culture-based methods fail in fast bacteria determination, while recent rapid diagnostic methods are expensive and prone to false positives. In this work, we present a sepsis kit for fast detection of bacteria in whole blood, here achieved by combining selective cell lysis and a sensitive colorimetric approach detecting as low as 10³ CFU/mL bacteria in less than 5 h. Homemade selective cell lysis buffer (combination of saponin and sodium cholate) allows fast processing of whole blood in 5 min while maintaining bacteria alive (100% viability). After filtration, retained bacteria on filter paper are incubated under constant illumination with the electrochromic precursors, i.e., ferricyanide and ferric ammonium citrate. Viable bacteria metabolically reduce iron(III) complexes, initiating a photocatalytic cascade toward Prussian blue formation. As a proof of concept, we combine this method with antibiotic susceptibility testing to determine the minimum inhibitory concentration (MIC) using two antibiotics (ampicillin and gentamicin). Although this kit is used to demonstrate its applicability to sepsis, this approach is expected to impact other key sectors such as hygiene evaluation, microbial contaminated food/beverage, or UTI, among others.

Detection of Blood Cell Surface Biomarkers in Septic Mice

Sepsis arises when an infection induces a dysregulated immune response, resulting in organ damage. New methods are urgently needed to diagnose patients in the early stages of sepsis, and identify patients with a poor disease prognosis. One promising approach is to identify the rapid changes in cell surface antigens (biomarkers) that occur during sepsis, as a consequence of leukocyte mobilization and activation. This chapter describes the method for staining whole blood with fluorescently conjugated antibodies that detect cell surface biomarkers, and performing flow cytometry analysis to quantify biomarker-positive cells. Our protocol is designed to detect blood cell surface biomarkers in septic mice, but could also be applied to study potential biomarkers in blood obtained from human patients with sepsis and other medical conditions.

Fully Automated, Sample-to-Answer Leukocyte Functional Assessment Platform for Continuous Sepsis Monitoring via Microliters of Blood

We report a fully automated, sample-to-answer, and label-free leukocyte activation analysis platform for monitoring immune responses in sepsis, by integrating the multidimensional double spiral (MDDS) and isodielectric separation (IDS) subplatforms. The integrated platform can provide rapid and fully automated identification of clinically diagnosed sepsis patients from only 50 μL of peripheral blood volume within 25 min. Many critical innovations were implemented in direct interconnection between the two subplatforms, such as intermediate sample storage and sample transfer, addressing flow rate mismatch (from mL/min to μL/min), and integration of a ridge array for upstream cell focusing in the IDS subplatform. The ridge array in the IDS subplatform can prevent the distortion of electrical profiling due to the residual red blood cells even after the MDDS process. We showed that the integrated platform can separate leukocytes (up to >99.9% red blood cell removal) in the MDDS subplatform and automatically transfer them to the downstream ridge-integrated IDS subplatform for their activation analysis without any apparent ex vivo cell activation and any human intervention. We also demonstrated that the integrated platform can identify differences between leukocytes from human sepsis and healthy subjects significantly (p = 0.0024, 95% confidence interval) by looking into differences in the intrinsic electrical properties of leukocytes. The integrated platform could enable monitoring of host leukocyte function daily or even hourly as a bedside assessment tool, which is currently a critical yet unmet need for managing many critical care patients.

Assessment of continuous neutrophil CD64 index measurement for diagnosing sepsis and predicting outcome in a Chinese pediatric intensive care unit: a prospective study

BACKGROUND

The high affinity immunoglobulin-Fc fragment receptor I CD64 on neutrophils is widely assumed to be a useful biomarker in the early identification of sepsis, and it improves outcomes. We aimed to determine its ability to diagnose sepsis and predict its prognosis with continuous measurements.

METHODS

A total of 335 patients admitted to a Chinese PICU were prospectively stratified into two groups according to the presence of sepsis (defined by clinical criteria for sepsis) between 2018 and 2019. Serum concentrations of the nCD64 index, C-reactive protein (CRP), and procalcitonin (PCT) were measured. Sensitivity, specificity and receiver operating characteristic (ROC) curves were calculated to evaluate the diagnostic value for sepsis. A multiple logistic regression model was used to estimate the prognostic value of continuous nCD64 index measurement for in-hospital death.

RESULTS

The baseline nCD64 index and levels of PCT and CRP were significantly higher in septic children than in nonseptic children (P<0.05). The nCD64 index presented a higher sensitivity (0.90), specificity (0.78) and area under the ROC curve [0.91 (0.90, 0.93)] than CRP and PCT in discriminating septic children with an optimal cutoff value of 5.78. The nCD64 index decreased with the progression of sepsis, and the baseline nCD64 index was strongly associated with in-hospital death (OR: 2.18, 95% CI: 1.02-4.74). Moreover, the more rapidly the nCD64 index declined, the lower the in-hospital death rate was (OR: 0.89, 95% CI: 0.63-1.35) after adjusting for the baseline nCD64 index and other confounders.

CONCLUSIONS

The nCD64 index was not only effective for the early diagnosis of childhood sepsis but also positively associated with the prognosis of sepsis. Moreover, the nCD64 decline was inversely associated with the in-hospital death rate.

Microfluidic Chips for Sepsis Diagnosis

This chapter discusses two microfluidic-based approaches for early sepsis detection that achieve a higher accuracy than traditional blood culture analysis. Patient blood samples were included in this work to validate the performance of our chips in diagnosing sepsis. The single-parameter chip demonstrated the increased accuracy if using CD64 as a biomarker for sepsis detection compared with C-reactive protein (CRP) and procalcitonin (PCT) when applied alone. In addition, a multiparameter chip measuring a combined panel of CD25, CD64, and CD69, and achieved a high accuracy with an Area Under the Receiver Operating Characteristic Curve (AUROC) of 0.978. The combined panel was also able to detect culture-negative patients and provided a faster diagnosis. Besides, microfluidics has advantages of less time consuming, easier to manufacture, less sample loading, less complex, and portable. Therefore, our approach is of great potential to become a bedside sepsis detection method.

A comparison of transferrin-receptor and epithelial cellular adhesion molecule targeting for microfluidic separation of cancer cells

Microfluidic, flow cytometry, and immunomagnetic methods for cancer cell isolation have heavily relied on the Epithelial Cellular Adhesion Molecule (EpCAM) for affinity separation. While EpCAM has been used extensively for circulating tumor cell isolation, it cannot be used to isolate non-epithelial cells. The human transferrin receptor (CD71) can also be used for cancer cell isolation and has the advantage that as an affinity target it can separate virtually any cancer cell type, regardless of disease origin. However, direct comparison of the capture ability of EpCAM and CD71 has not been reported previously. In this work, cell capture with both EpCAM and CD71 were studied using a novel higher-throughput herringbone cell separation microfluidic device. Five separation chip models were designed and the one with the highest capture efficiency (average 90 ± 10%) was chosen to compare antigen targets for cell capture. Multiple cancer cell lines including CCRF-CEM, PC-3 and MDA-MB-231 were tested for cell capture performance using both ligands (anti-CD71 and anti-EpCAM) in the optimized chip design. PC-3 and MDA-MB-231 cells were spiked into blood at concentrations ranging from 0.5%-10%. PC-3 cells were separated by anti-CD71 and anti-EpCAM with 32-37% and 31-50% capture purity respectively, while MDA-MB-231 were separated with 35-53% and 33-56% capture purity using anti-CD71 and anti-EpCAM for all concentrations. The enrichment factor for the lowest concentrations of cells in blood ranged from 66-74X. The resulting enrichment of cancer cells shows that anti-CD71 was found to be statistically similar to anti-EpCAM for epithelial cancer cells, while anti-CD71 can be further used for non-epithelial cells, where anti-EpCAM cannot be used.

Microfluidics for sepsis early diagnosis and prognosis: a review of recent methods

Sepsis is a complex disorder of immune system response to infections that can be caused by a wide range of clinical contexts. Traditional methods for sepsis detection include molecular diagnosis, biomarkers either based on protein concentration or cell surface expression, and microbiological cultures. Development of point-of-care (POC) instruments, which can provide high accuracy and consume less time, is in unprecedented demand. Within the past few years, applications of microfluidic systems for sepsis detection have achieved excellent performance. In this review, we discuss the most recent microfluidic applications specifically in sepsis detection, and propose their advantages and disadvantages. We also present a comprehensive review of other traditional and current sepsis diagnosis methods to obtain a general understanding of the present conditions, which can hopefully direct the development of a new sepsis roadmap.

Recent trends in sorbents for bioaffinity chromatography

Isolation or enrichment of biological molecules from complex biological samples is mostly a prerequisite in proteomics, genomics, and glycomics. Different techniques have been used to advance the efficiency of the purification of biological molecules. Bioaffinity chromatography is one of the most powerful technique that plays an important role in the isolation of target biological molecules by the specific interactions with ligands that are immobilized on different support materials. This review examines the recent developments in bioaffinity chromatography particularly over the past 5 years in the literature. Also properties of supports, immobilization techniques, types of binding agents, and methods used in bioaffinity chromatography applications are summarized.

Evaluating the Timeliness and Specificity of CD69, CD64, and CD25 as Biomarkers of Sepsis in Mice

ABSTRACT

Sepsis occurs when an infection induces a dysregulated immune response, and is most commonly bacterial in origin. This condition requires rapid treatment for successful patient outcomes. However, the current method to confirm infection (blood culture) requires up to 48 h for a positive result and many true cases remain culture-negative. Therefore, new diagnostic tests are urgently needed. Recent clinical studies suggest that CD69, CD64, and CD25 may serve as useful biomarkers of sepsis. In this study, we evaluated the cecal ligation and puncture and cecal slurry mouse models as tools to study these biomarkers in young and aged mice, and elucidate the timeliness and specificity of sepsis diagnosis. Fluorescence-activated cell sorting analysis revealed that all three biomarkers were elevated on blood leukocytes during sepsis. CD69 was specifically upregulated during sepsis, while CD64 and CD25 were also transiently upregulated in response to sham surgery. The optimal biomarker, or combination of biomarkers, depended on the timing of detection, mouse age, and presence of surgery. CD69 demonstrated an excellent capacity to distinguish sepsis, and in some scenarios the diagnostic performance was enhanced by combining CD69 with CD64. We also analyzed biomarker expression levels on specific cell populations (lymphocytes, monocytes, and neutrophils) and determined the cell types that upregulate each biomarker. Elevations in blood biomarkers were also detected via microfluidic analyses; in this case CD64 distinguished septic mice from naive controls. Our results suggest that CD69 and CD64 are valuable biomarkers to rapidly detect sepsis, and that mouse models are useful to study and validate sepsis biomarkers.

An inflammatory vascular endothelium-mimicking microfluidic device to enable leukocyte rolling and adhesion for rapid infection diagnosis

Recruitment of circulating leukocytes to sites of infection is of utmost importance in the development, propagation, and outcome of sepsis. These multi-step processes are mediated by interactions between adhesion receptors of leukocytes and cell adhesion molecules (CAMs) of endothelial cells, such as P-selectin, E-selectin and ICAM-1. However, the potential utility of the CAMs-facilitated leukocyte capture has not been thoroughly investigated as an index of the host response to infection for diagnostic purposes. Here, we report that the systemic infection affects the expression of CAMs ligands on leukocytes, upregulating the expression of P-selectin ligand-1 (PSGL-1) and increasing the number of PSGL-1- and E-selectin ligand-1 (ESL-1)-expressing leukocyte levels in septic blood. We leveraged this finding to determine infection by measuring the increased adhesion of leukocytes to an inflammatory vascular endothelium-mimicking microchannel coated with CAMs. We successfully validated that the proposed method can significantly differentiate infection in bacteremia and endotoxemia models in rats as early as an hour post-infection using a finger-prick volume of blood (50 μL), which were unachievable with the conventional diagnostic methods.

Esmolol inhibits inflammation and apoptosis in the intestinal tissue via the overexpression of NF-κB-p65 in the early stage sepsis rats

BACKGROUND/AIMS

Accumulating evidence reveals esmolol could protect the gut mucosa through the regulation of immune response and inflammation in patients with sepsis. However, its underlying mechanism is not fully understood.

MATERIALS AND METHODS

Diamine oxidase (DAO), intestinal fatty acid-binding protein (I-FABP), interleukin (IL)-6, and IL-10 in the plasma of rats were detected by ELISA assay. Western blotting was utilized to measure the expression levels of NF-kappa B-p65, Bcl-2, and cleaved caspase-3 in the intestinal tissues. The survival analysis was performed in each group.

RESULTS

The plasma levels of DAO and IL-10 levels were increased, whereas that of I-FABP and IL-6 were decreased in the sepsis rats after esmolol treatment, indicating that after the esmolol treatment, the intestinal inflammation and damages were remarkably reduced as compared to those in the normal saline treated sepsis rats. NF-κB-p65 and Bcl-2 were highly expressed, but cleaved caspase-3 showed lower expression in the esmolol treated groups. However, at the same time, we observed contrasting results in the normal saline treated group. Western blotting data indicated that the esmolol treatment inhibited the inflammation and apoptosis in the intestinal tissue due to the overexpression of NF-κB-p65 in the celiac sepsis rats. The survival analysis results indicate that the esmolol infusion should be used in the early stages sepsis rats.

CONCLUSION

Esmolol can suppress inflammation and apoptosis in the intestinal tissue via the overexpression of NF-kappa B-p65 in the early stage sepsis rats. kappa BEarly-stage use of esmolol might be an ideal treatment method for sepsis.

Combinatorial Immunophenotyping of Cell Populations with an Electronic Antibody Microarray

Immunophenotyping is widely used to characterize cell populations in basic research and to diagnose diseases from surface biomarkers in the clinic. This process usually requires complex instruments such as flow cytometers or fluorescence microscopes, which are typically housed in centralized laboratories. Microfluidics are combined with an integrated electrical sensor network to create an antibody microarray for label-free cell immunophenotyping against multiple antigens. The device works by fractionating the sample via capturing target subpopulations in an array of microfluidic chambers functionalized against different antigens and by electrically quantifying the cell capture statistics through a network of code-multiplexed electrical sensors. Through a combinatorial arrangement of antibody sequences along different microfluidic paths, the device can measure the prevalence of different cell subpopulations in a sample from computational analysis of the electrical output signal. The device performance is characterized by analyzing heterogeneous samples of mixed tumor cell populations and then the technique is applied to determine leukocyte subpopulations in blood samples and the results are validated against complete blood cell count and flow cytometry results. Label-free immunophenotyping of cell populations against multiple targets on a disposable electronic chip presents opportunities in global health and telemedicine applications for cell-based diagnostics and health monitoring.

Leukocyte function assessed via serial microlitre sampling of peripheral blood from sepsis patients correlates with disease severity

Dysregulated leukocyte responses underlie the pathobiology of sepsis, which is a leading cause of death. However, measures of leukocyte function are not routinely available in clinical care. Here we report the development and testing of an inertial microfluidic system for the label-free isolation and downstream functional assessment of leukocytes from 50 μl of peripheral blood. We used the system to assess leukocyte phenotype and function in serial samples from 18 hospitalized patients with sepsis and 10 healthy subjects. The sepsis samples had significantly higher levels of CD16^dim and CD16⁻ neutrophils and CD16⁺ ‘intermediate’ monocytes, as well as significantly lower levels of neutrophil-elastase release, O₂⁻ production and phagolysosome formation. Repeated sampling of sepsis patients over 7 days showed that leukocyte activation (measured by isodielectric separation) and leukocyte phenotype and function were significantly more predictive of the clinical course than complete-blood-count parameters. We conclude that the serial assessment of leukocyte function in microlitre blood volumes is feasible and that it provides significantly more prognostic information than leukocyte counting.

The serial assessment of the functional parameters of leukocytes isolated via an inertial microfluidic system from 50 μl of peripheral blood from sepsis patients provides significantly more prognostic information than leukocyte counting.

Smartphone-imaged microfluidic biochip for measuring CD64 expression from whole blood

Sepsis, a life-threatening syndrome that contributes to millions of deaths annually worldwide, represents a moral and economic burden to the healthcare system. Although no single, or even a combination of biomarkers has been validated for the diagnosis of sepsis, multiple studies have shown the high specificity of CD64 expression on neutrophils (nCD64) to sepsis. The analysis of elevated nCD64 in the first 2-6 hours after infection during the pro-inflammatory stage could significantly contribute to early sepsis diagnosis. Therefore, a rapid and automated device to periodically measure nCD64 expression at the point-of-care (POC) could lead to timely medical intervention and reduced mortality rates. Current accepted technologies for measuring nCD64 expression, such as flow cytometry, require manual sample preparation and long incubation times. For POC applications, however, the technology should be able to measure nCD64 expression with little to no sample preparation. In this paper, we demonstrate a smartphone-imaged microfluidic biochip for detecting nCD64 expression in under 50 min. In our assay, first unprocessed whole blood is injected into a capture chamber to immunologically capture nCD64 along a staggered array of pillars, which were previously functionalized with an antibody against CD64. Then, an image of the capture channel is taken using a smartphone-based microscope. This image is used to measure the cumulative fraction of captured cells (γ) as a function of length in the channel. During the image analysis, a statistical model is fitted to γ in order to extract the probability of capture of neutrophils per collision with a pillar (ε). The fitting shows a strong correlation with nCD64 expression measured using flow cytometry (R² = 0.82). Finally, the applicability of the device to sepsis was demonstrated by analyzing nCD64 from 8 patients (37 blood samples analyzed) along the time they were admitted to the hospital. Results from this analysis, obtained using the smartphone-imaged microfluidic biochip were compared with flow cytometry. Again, a correlation coefficient R² = 0.82 (slope = 0.99) was obtained demonstrating a good linear correlation between the two techniques. Deployment of this technology in ICU could significantly enhance patient care worldwide.

Point of care technologies for sepsis diagnosis and treatment

Sepsis is a rapidly progressing, life threatening immune response triggered by infection that affects millions worldwide each year. Current clinical diagnosis relies on broad physiological parameters and time consuming lab-based cell culture. If proper treatment is not provided, cases of sepsis can drastically increase in severity over the course of a few hours. Development of new point of care tools for sepsis has the potential to improve diagnostic speed and accuracy, leading to prompt administration of appropriate therapeutics, thereby reducing healthcare costs and improving patient outcomes. In this review we examine developing and commercially available technologies to assess the feasibility of rapid, accurate sepsis diagnosis, with emphasis on point of care.