Integrated nanoplasmonic sensing for cellular functional immunoanalysis using human blood

Development of gold nanocluster complex for the detection of tumor necrosis factor-alpha based on immunoassay

Tumor necrosis factor-alpha, TNF-α, a cytokine recognized as a key regulator of inflammatory responses, is primarily produced by activated monocytes and macrophages. Measuring TNF-α levels serves as a valuable indicator for tracking several diseases and pathological states. Gold nanotechnology has been identified as a highly effective catalyst with unique properties for measuring inflammatory cytokines. This study aimed to synthesize gold nanoclusters (AuNCs) and the AuNCs-streptavidin system, along with their characterizations and spherical morphology. The detection of TNF-α antigen with AuNCs was determined, and a new immunoassay-based AuNCs analytical platform was studied. In this study, it was demonstrated that the synthesized AuNCs and AuNCs-streptavidin showed a bright-yellow appearance with absorption peaks at A600 and A610 nm, respectively. The approximately spherical shape was observed by TEM analysis. The AuNCs demonstrated a sensitivity limit for the detection of the TNF-α antigen, with a linear dose-dependent detection range of less than 1.25 ng/mL. The products of the band sizes and band intensities were proportional to the amount of TNF-α in the range of ∼80 kDa, ∼55 kDa, and ∼ 25 kDa in western blot analysis. The TNF-α in cell lysate was successfully detected using an immunoassay after the activation of RAW264.7 cells with lipopolysaccharide (LPS). This assay may serve as a viable alternative for TNF-α detection with high speed, sensitivity, and qualities, ensuring its broad applications.

Supremacy of nanoparticles in the therapy of chronic myelogenous leukemia

Background and purpose

The reciprocal translocation of the ABL gene from chromosome 9 to chromosome 22 near the BCR gene gives rise to chronic myelogenous leukemia (CML). The translocation results in forming the Philadelphia chromosome (BCR-ABL) tyrosine kinase. CML results in an increase in the number of white blood cells and alteration in tyrosine kinase expression. CML prognosis includes three stages, namely chronic, accelerated, and blast. The diagnosis method involves a CT scan, biopsy, and complete blood count. However, due to certain disadvantages, early diagnosis of CML is not possible by traditional methods. Nanotechnology offers many advantages in diagnosing and treating cancer.

Experimental approach

We searched PubMed, Scopus and Google Scholar using the keywords Philadelphia chromosome, bionanotechnology, tyrosine kinase pathway, half-life, passive targeting, and organic and inorganic nanoparticles. The relevant papers and the classical papers in this field were selected to write about in this review.

Key results

The sensitivity and specificity of an assay can be improved by nanoparticles. Utilizing this property, peptides, antibodies, aptamers, etc., in the form of nanoparticles, can be used to detect cancer at a much earlier stage. The half-life of the drug is also increased by nanoformulation. The nanoparticle-coated drugs can easily escape from the immune system.

Conclusion

Depending on their type, nanoparticles can be categorized into organic, inorganic and hybrid. Each type has its advantages. Organic nanoparticles have good biocompatibility, inorganic nanoparticles increase the half-life of the drugs. In this review, we highlight the nanoparticles involved in treating CML.

Reconstructing the cytokine view for the multi-view prediction of COVID-19 mortality

BACKGROUND

Coronavirus disease 2019 (COVID-19) is a rapidly developing and sometimes lethal pulmonary disease. Accurately predicting COVID-19 mortality will facilitate optimal patient treatment and medical resource deployment, but the clinical practice still needs to address it. Both complete blood counts and cytokine levels were observed to be modified by COVID-19 infection. This study aimed to use inexpensive and easily accessible complete blood counts to build an accurate COVID-19 mortality prediction model. The cytokine fluctuations reflect the inflammatory storm induced by COVID-19, but their levels are not as commonly accessible as complete blood counts. Therefore, this study explored the possibility of predicting cytokine levels based on complete blood counts.

METHODS

We used complete blood counts to predict cytokine levels. The predictive model includes an autoencoder, principal component analysis, and linear regression models. We used classifiers such as support vector machine and feature selection models such as adaptive boost to predict the mortality of COVID-19 patients.

RESULTS

Complete blood counts and original cytokine levels reached the COVID-19 mortality classification area under the curve (AUC) values of 0.9678 and 0.9111, respectively, and the cytokine levels predicted by the feature set alone reached the classification AUC value of 0.9844. The predicted cytokine levels were more significantly associated with COVID-19 mortality than the original values.

CONCLUSIONS

Integrating the predicted cytokine levels and complete blood counts improved a COVID-19 mortality prediction model using complete blood counts only. Both the cytokine level prediction models and the COVID-19 mortality prediction models are publicly available at http://www.healthinformaticslab.org/supp/resources.php .

Biosensors integrated 3D organoid/organ-on-a-chip system: A real-time biomechanical, biophysical, and biochemical monitoring and characterization

As a full-fidelity simulation of human cells, tissues, organs, and even systems at the microscopic scale, Organ-on-a-Chip (OOC) has significant ethical advantages and development potential compared to animal experiments. The need for the design of new drug high-throughput screening platforms and the mechanistic study of human tissues/organs under pathological conditions, the evolving advances in 3D cell biology and engineering, etc., have promoted the updating of technologies in this field, such as the iteration of chip materials and 3D printing, which in turn facilitate the connection of complex multi-organs-on-chips for simulation and the further development of technology-composite new drug high-throughput screening platforms. As the most critical part of organ-on-a-chip design and practical application, verifying the success of organ model modeling, i.e., evaluating various biochemical and physical parameters in OOC devices, is crucial. Therefore, this paper provides a logical and comprehensive review and discussion of the advances in organ-on-a-chip detection and evaluation technologies from a broad perspective, covering the directions of tissue engineering scaffolds, microenvironment, single/multi-organ function, and stimulus-based evaluation, and provides a more comprehensive review of the progress in the significant organ-on-a-chip research areas in the physiological state.

Evaluation of SARS-CoV-2-Specific T-Cell Activation with a Rapid On-Chip IGRA

Interferon-gamma release assays (IGRAs) that measure pathogen-specific T-cell response rates can provide a more reliable estimate of protection than specific antibody levels but have limited potential for widespread use due to their workflow, personnel, and instrumentation demands. The major vaccines for SARS-CoV-2 have demonstrated substantial efficacy against all of its current variants, but approaches are needed to determine how these vaccines will perform against future variants, as they arise, to inform vaccine and public health policies. Here we describe a rapid, sensitive, nanolayer polylysine-integrated microfluidic chip IGRA read by a fluorescent microscope that has a 5 h sample-to-answer time and uses ∼25 μL of a fingerstick whole blood sample. Results from this assay correlated with those of a comparable clinical IGRA when used to evaluate the T-cell response to SARS-CoV-2 peptides in a population of vaccinated and/or infected individuals. Notably, this streamlined and inexpensive assay is suitable for high-throughput analyses in resource-limited settings for other infectious diseases.

Photonic Sensors in Chemical and Biological Applications

Biosensors are described as analytical devices in which biological substances are detected by using various physicochemical detection systems [...].

Enhanced Label-Free Nanoplasmonic Cytokine Detection in SARS-CoV-2 Induced Inflammation Using Rationally Designed Peptide Aptamer

Rapid and precise serum cytokine quantification provides immense clinical significance in monitoring the immune status of patients in rapidly evolving infectious/inflammatory disorders, examplified by the ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic. However, real-time information on predictive cytokine biomarkers to guide targetable immune pathways in pathogenic inflammation is critically lacking, because of the insufficient detection range and detection limit in current label-free cytokine immunoassays. In this work, we report a highly sensitive localized surface plasmon resonance imaging (LSPRi) immunoassay for label-free Interleukin 6 (IL-6) detection utilizing rationally designed peptide aptamers as the capture interface. Benefiting from its characteristically smaller dimension and direct functionalization on the sensing surface via Au-S bonding, the peptide-aptamer-based LSPRi immunoassay achieved enhanced label-free serum IL-6 detection with a record-breaking limit of detection down to 4.6 pg/mL, and a wide dynamic range of ∼6 orders of magnitude (values from 4.6 to 1 × 106 pg/mL were observed). The immunoassay was validated in vitro for label-free analysis of SARS-CoV-2 induced inflammation, and further applied in rapid quantification of serum IL-6 profiles in COVID-19 patients. Our peptide aptamer LSPRi immunoassay demonstrates great potency in label-free cytokine detection with unprecedented sensing capability to provide accurate and timely interpretation of the inflammatory status and disease progression, and determination of prognosis.

Spectral image contrast-based flow digital nanoplasmon-metry for ultrasensitive antibody detection

Background

Gold nanoparticles (AuNPs) have been widely used in local surface plasmon resonance (LSPR) immunoassays for biomolecule sensing, which is primarily based on two conventional methods: absorption spectra analysis and colorimetry. The low figure of merit (FoM) of the LSPR and high-concentration AuNP requirement restrict their limit of detection (LOD), which is approximately ng to μg mL⁻¹ in antibody detection if there is no other signal or analyte amplification. Improvements in sensitivity have been slow in recent for a long time, and pushing the boundary of the current LOD is a great challenge of current LSPR immunoassays in biosensing.

Results

In this work, we developed spectral image contrast-based flow digital nanoplasmon-metry (Flow DiNM) to push the LOD boundary. Comparing the scattering image brightness of AuNPs in two neighboring wavelength bands near the LSPR peak, the peak shift signal is strongly amplified and quickly detected. Introducing digital analysis, the Flow DiNM provides an ultrahigh signal-to-noise ratio and has a lower sample volume requirement. Compared to the conventional analog LSPR immunoassay, Flow DiNM for anti-BSA detection in pure samples has an LOD as low as 1 pg mL⁻¹ within only a 15-min detection time and 500 μL sample volume. Antibody assays against spike proteins of SARS-CoV-2 in artificial saliva that contained various proteins were also conducted to validate the detection of Flow DiNM in complicated samples. Flow DiNM shows significant discrimination in detection with an LOD of 10 pg mL⁻¹ and a broad dynamic detection range of five orders of magnitude.

Conclusion

Together with the quick readout time and simple operation, this work clearly demonstrated the high sensitivity and selectivity of the developed Flow DiNM in rapid antibody detection. Spectral image contrast and digital analysis further provide a new generation of LSPR immunoassay with AuNPs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01188-6.

Recent Development of Optofluidics for Imaging and Sensing Applications

Optofluidics represents the interaction of light and fluids on a chip that integrates microfluidics and optics, which provides a promising optical platform for manipulating and analyzing fluid samples. Recent years have witnessed a substantial growth in optofluidic devices, including the integration of optical and fluidic control units, the incorporation of diverse photonic nanostructures, and new applications. All these advancements have enabled the implementation of optofluidics with improved performance. In this review, the recent advances of fabrication techniques and cutting-edge applications of optofluidic devices are presented, with a special focus on the developments of imaging and sensing. Specifically, the optofluidic based imaging techniques and applications are summarized, including the high-throughput cytometry, biochemical analysis, and optofluidic nanoparticle manipulation. The optofluidic sensing section is categorized according to the modulation approaches and the transduction mechanisms, represented by absorption, reflection/refraction, scattering, and plasmonics. Perspectives on future developments and promising avenues in the fields of optofluidics are also provided.

On Demand Biosensors for Early Diagnosis of Cancer and Immune Checkpoints Blockade Therapy Monitoring from Liquid Biopsy

Recently, considerable interest has emerged in the development of biosensors to detect biomarkers and immune checkpoints to identify and measure cancer through liquid biopsies. The detection of cancer biomarkers from a small volume of blood is relatively fast compared to the gold standard of tissue biopsies. Traditional immuno-histochemistry (IHC) requires tissue samples obtained using invasive procedures and specific expertise as well as sophisticated instruments. Furthermore, the turnaround for IHC assays is usually several days. To overcome these challenges, on-demand biosensor-based assays were developed to provide more immediate prognostic information for clinicians. Novel rapid, highly precise, and sensitive approaches have been under investigation using physical and biochemical methods to sense biomarkers. Additionally, interest in understanding immune checkpoints has facilitated the rapid detection of cancer prognosis from liquid biopsies. Typically, these devices combine various classes of detectors with digital outputs for the measurement of soluble cancer or immune checkpoint (IC) markers from liquid biopsy samples. These sensor devices have two key advantages: (a) a small volume of blood drawn from the patient is sufficient for analysis, and (b) it could aid physicians in quickly selecting and deciding the appropriate therapy regime for the patients (e.g., immune checkpoint blockade (ICB) therapy). In this review, we will provide updates on potential cancer markers, various biosensors in cancer diagnosis, and the corresponding limits of detection, while focusing on biosensor development for IC marker detection.

Nanoplatforms for Sepsis Management: Rapid Detection/Warning, Pathogen Elimination and Restoring Immune Homeostasis

Sepsis, a highly life-threatening organ dysfunction caused by uncontrollable immune responses to infection, is a leading contributor to mortality in intensive care units. Sepsis-related deaths have been reported to account for 19.7% of all global deaths. However, no effective and specific therapeutic for clinical sepsis management is available due to the complex pathogenesis. Concurrently eliminating infections and restoring immune homeostasis are regarded as the core strategies to manage sepsis. Sophisticated nanoplatforms guided by supramolecular and medicinal chemistry, targeting infection and/or imbalanced immune responses, have emerged as potent tools to combat sepsis by supporting more accurate diagnosis and precision treatment. Nanoplatforms can overcome the barriers faced by clinical strategies, including delayed diagnosis, drug resistance and incapacity to manage immune disorders. Here, we present a comprehensive review highlighting the pathogenetic characteristics of sepsis and future therapeutic concepts, summarizing the progress of these well-designed nanoplatforms in sepsis management and discussing the ongoing challenges and perspectives regarding future potential therapies. Based on these state-of-the-art studies, this review will advance multidisciplinary collaboration and drive clinical translation to remedy sepsis.

Ultrasensitive Multiparameter Phenotyping of Rare Cells Using an Integrated Digital-Molecular-Counting Microfluidic Well Plate

Integrated microfluidic cellular phenotyping platforms provide a promising means of studying a variety of inflammatory diseases mediated by cell-secreted cytokines. However, immunosensors integrated in previous microfluidic platforms lack the sensitivity to detect small signals in the cellular secretion of proinflammatory cytokines with high precision. This limitation prohibits researchers from studying cells secreting cytokines at low abundance or existing at a small population. Herein, the authors present an integrated platform named the "digital Phenoplate (dPP)," which integrates digital immunosensors into a microfluidic chip with on-chip cell assay chambers, and demonstrates ultrasensitive cellular cytokine secretory profile measurement. The integrated sensors yield a limit of detection as small as 0.25 pg mL-1 for mouse tumor necrosis factor alpha (TNF-α). Each on-chip cell assay chamber confines cells whose population ranges from ≈20 to 600 in arrayed single-cell trapping microwells. Together, these microfluidic features of the dPP simultaneously permit precise counting and image-based cytometry of individual cells while performing parallel measurements of TNF-α released from rare cells under multiple stimulant conditions for multiple samples. The dPP platform is broadly applicable to the characterization of cellular phenotypes demanding high precision and high throughput.

Plasmonic sensing, imaging, and stimulation techniques for neuron studies

Studies to understand the structure, functions, and electrophysiological properties of neurons have been conducted at the frontmost end of neuroscience. Such studies have led to the active development of high-performance research tools for exploring the neurobiology at the cellular and molecular level. Following this trend, research and application of plasmonics, which is a technology employed in high-sensitivity optical biosensors and high-resolution imaging, is essential for studying neurons, as plasmonic nanoprobes can be used to stimulate specific areas of cells. In this study, three plasmonic modalities were explored as tools to study neurons and their responses: (1) plasmonic sensing of neuronal activities and neuron-related chemicals; (2) performance-improved optical imaging of neurons using plasmonic enhancements; and (3) plasmonic neuromodulations. Through a detailed investigation of these plasmonic modalities and research subjects that can be combined with them, it was confirmed that plasmonic sensing, imaging, and stimulation techniques have the potential to be effectively employed for the study of neurons and understanding their specific molecular activities.

Bubbles in microfluidics: an all-purpose tool for micromanipulation

In recent decades, the integration of microfluidic devices and multiple actuation technologies at the microscale has greatly contributed to the progress of related fields. In particular, microbubbles are playing an increasingly important role in microfluidics because of their unique characteristics that lead to specific responses to different energy sources and gas-liquid interactions. Many effective and functional bubble-based micromanipulation strategies have been developed and improved, enabling various non-invasive, selective, and precise operations at the microscale. This review begins with a brief introduction of the morphological characteristics and formation of microbubbles. The theoretical foundations and working mechanisms of typical micromanipulations based on acoustic, thermodynamic, and chemical microbubbles in fluids are described. We critically review the extensive applications and the frontline advances of bubbles in microfluidics, including microflow patterns, position and orientation control, biomedical applications, and development of bubble-based microrobots. We lastly present an outlook to provide directions for the design and application of microbubble-based micromanipulation tools and attract the attention of relevant researchers to the enormous potential of microbubbles in microfluidics.

Novel voltammetric tumor necrosis factor-alpha (TNF-α) immunosensor based on gold nanoparticles involved in thiol-functionalized multi-walled carbon nanotubes and bimetallic Ni/Cu-MOFs

TNF-α, as a pro-inflammatory cytokine, regulates some physiological and pathological courses. TNF-α level increases in some important diseases such as cancer, arthritis, and diabetes. In addition, it displays an important function in Alzheimer's and cardiovascular diseases. Herein, a novel, sensitive, and selective voltammetric TNF-α immunosensor was prepared by using gold nanoparticles involved in thiol-functionalized multi-walled carbon nanotubes (AuNPs/S-MWCNTs) as sensor platform and bimetallic Ni/Cu-MOFs as sensor amplification. Firstly, the sensor platform was developed on glassy carbon electrode (GCE) surface by using mixture of thiol-functionalized MWCNTs (S-MWCNTs) and AuNPs. Then, capture TNF-α antibodies were conjugated to sensor platform by amino-gold affinity. After capture TNF-α antibodies' immobilization, a new-type voltammetric TNF-α immunosensor was developed by immune reaction between AuNPs/S-MWCNTs immobilized with primer TNF-α antibodies and bimetallic Ni/Cu-MOFs conjugated with seconder TNF-α antibodies. The prepared TNF-α immunosensor was characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD) method, x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), thermogravimetric analysis, Fourier transform infrared spectroscopy (FTIR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). A linearity range of 0.01-1.0 pg mL^-1 and a low detection limit of 2.00 fg mL^-1 were also obtained for analytical applications.

Nanoplasmonic-Nanofluidic Single-Molecule Biosensors for Ultrasmall Sample Volumes

Detection of small amounts of biological compounds is of ever-increasing importance but also remains an experimental challenge. In this context, plasmonic nanoparticles have emerged as strong contenders enabling label-free optical sensing with single-molecule resolution. However, the performance of a plasmonic single-molecule biosensor is not only dependent on its ability to detect a molecule but equally importantly on its efficiency to transport it to the binding site. Here, we present a theoretical study of the impact of downscaling fluidic structures decorated with plasmonic nanoparticles from conventional microfluidics to nanofluidics. We find that for ultrasmall picolitre sample volumes, nanofluidics enables unprecedented binding characteristics inaccessible with conventional microfluidic devices, and that both detection times and number of detected binding events can be improved by several orders of magnitude. Therefore, we propose nanoplasmonic–nanofluidic biosensing platforms as an efficient tool that paves the way for label-free single-molecule detection from ultrasmall volumes, such as single cells.

Bioengineering tools for probing intracellular events in T lymphocytes

T lymphocytes are the central coordinator and executor of many immune functions. The activation and function of T lymphocytes are mediated through the engagement of cell surface receptors and regulated by a myriad of intracellular signaling network. Bioengineering tools, including imaging modalities and fluorescent probes, have been developed and employed to elucidate the cellular events throughout the functional lifespan of T cells. A better understanding of these events can broaden our knowledge in the immune systems biology, as well as accelerate the development of effective diagnostics and immunotherapies. Here we review the commonly used and recently developed techniques and probes for monitoring T lymphocyte intracellular events, following the order of intracellular events in T cells from activation, signaling, metabolism to apoptosis. The techniques introduced here can be broadly applied to other immune cells and cell systems. This article is categorized under: Immune System Diseases > Molecular and Cellular Physiology Immune System Diseases > Biomedical Engineering Infectious Diseases > Biomedical Engineering.

How Nanophotonic Label-Free Biosensors Can Contribute to Rapid and Massive Diagnostics of Respiratory Virus Infections: COVID-19 Case

The global sanitary crisis caused by the emergence of the respiratory virus SARS-CoV-2 and the COVID-19 outbreak has revealed the urgent need for rapid, accurate, and affordable diagnostic tests to broadly and massively monitor the population in order to properly manage and control the spread of the pandemic. Current diagnostic techniques essentially rely on polymerase chain reaction (PCR) tests, which provide the required sensitivity and specificity. However, its relatively long time-to-result, including sample transport to a specialized laboratory, delays massive detection. Rapid lateral flow tests (both antigen and serological tests) are a remarkable alternative for rapid point-of-care diagnostics, but they exhibit critical limitations as they do not always achieve the required sensitivity for reliable diagnostics and surveillance. Next-generation diagnostic tools capable of overcoming all the above limitations are in demand, and optical biosensors are an excellent option to surpass such critical issues. Label-free nanophotonic biosensors offer high sensitivity and operational robustness with an enormous potential for integration in compact autonomous devices to be delivered out-of-the-lab at the point-of-care (POC). Taking the current COVID-19 pandemic as a critical case scenario, we provide an overview of the diagnostic techniques for respiratory viruses and analyze how nanophotonic biosensors can contribute to improving such diagnostics. We review the ongoing published work using this biosensor technology for intact virus detection, nucleic acid detection or serological tests, and the key factors for bringing nanophotonic POC biosensors to accurate and effective COVID-19 diagnosis on the short term.

Design of a Multiplexed Analyte Biosensor using Digital Barcoded Particles and Impedance Spectroscopy

Multiplexing allows quantifying multiple analytes in a single step, providing advantages over individual testing through shorter processing time, lower sample volume, and reduced cost per test. Currently, flow cytometry is the gold standard for biomedical multiplexing, but requires technical training, extensive data processing, and expensive operational and capital costs. To solve this challenge, we designed digital barcoded particles and a microfluidic architecture for multiplexed analyte quantification. In this work, we simulate and model non-fluorescence-based microfluidic impedance detection with a single excitation and detection scheme using barcoded polymer microparticles. Our barcoded particles can be designed with specific coding regions and generate numerous distinct patterns enabling digital barcoding. We found that signals based on adhered microsphere position and relative orientation were evaluated and separated based on their associated electrical signatures and had a 7 µm microsphere limit of detection. Our proposed microfluidic system can enumerate micron-sized spheres in a single assay using barcoded particles of various configurations. As representation of blood cells, the microsphere concentrations may provide useful information on disease onset and progression. Such sensors may be used for diagnostic and management of common critical care diseases like sepsis, acute kidney injury, urinary tract infections, and HIV/AIDS.

Integrated Microfluidic Device for Functional Secretory Immunophenotyping of Immune Cells

Integrated platforms for automatic assessment of cellular functional secretory immunophenotyping could have a widespread use in the diagnosis, real-time monitoring, and therapy evaluation of several pathologies. We present a microfluidic platform with integrated biosensors and culture chambers to measure cytokine secretion from a consistent and uniform number of immune cells. The biosensor relies on a fluorescence sandwich immunoassay enabled by the mechanically induced trapping of molecular interactions method. The platform contains 32 cell culture chambers, each patterned with an array of 492 microwells, to capture and analyze both adherent and nonadherent immune cells. Multiple stimuli can be delivered to a set of culture chambers. Per chamber, we were able to capture consistently 1113 ± 191 of blood-derived monocytes and neutrophils and 348 ± 37 THP-1 monocytes. Good occupancy efficiencies of ∼70% with a uniformity of ∼90% across all of the culture chambers of the device were achieved. Furthermore, we demonstrate that up to 96% of cells remain viable for the first 48 h. The employment of epoxy-modified glass substrates and active mixing enhanced the biosensing performance compared to the use of bare glass and simple diffusion. Finally, we performed functional secretory analysis of interleukin-8 and tumor necrosis factor alpha from human neutrophils and monocytes, stimulated with various doses of lipopolysaccharide and phorbol 12-myristate 13-acetate-ionomycin, respectively. We foresee the employment of our microfluidic platform in the diagnosis of different pathologies where alterations in cytokine secretion patterns can be used as biomarkers.

Oliveira O, Mejía-Salazar JR. Chiral Plasmonics and Their Potential for Point-of-Care Biosensing Applications

There has been growing interest in using strong field enhancement and light localization in plasmonic nanostructures to control the polarization properties of light. Various experimental techniques are now used to fabricate twisted metallic nanoparticles and metasurfaces, where strongly enhanced chiral near-fields are used to intensify circular dichroism (CD) signals. In this review, state-of-the-art strategies to develop such chiral plasmonic nanoparticles and metasurfaces are summarized, with emphasis on the most recent trends for the design and development of functionalizable surfaces. The major objective is to perform enantiomer selection which is relevant in pharmaceutical applications and for biosensing. Enhanced sensing capabilities are key for the design and manufacture of lab-on-a-chip devices, commonly named point-of-care biosensing devices, which are promising for next-generation healthcare systems.

Real-Time Monitoring and Detection of Single-Cell Level Cytokine Secretion Using LSPR Technology

Cytokine secretion researches have been a main focus of studies among the scientists in the recent decades for its outstanding contribution to clinical diagnostics. Localized surface plasmon resonance (LSPR) technology is one of the conventional methods utilized to analyze these issues, as it could provide fast, label-free and real-time monitoring of biomolecule binding events. However, numerous LSPR-based biosensors in the past are usually utilized to monitor the average performance of cell groups rather than single cells. Meanwhile, the complicated sensor structures will lead to the fabrication and economic budget problems. Thus, in this paper, we report a simple synergistic integration of the cell trapping of microwell chip and gold-capped nanopillar-structured cyclo-olefin-polymer (COP) film for single cell level Interleukin 6 (IL-6) detection. Here, in-situ cytokine secreted from the trapped cell can be directly observed and analyzed through the peak red-shift in the transmittance spectrum. The fabricated device also shows the potential to conduct the real-time monitoring which would greatly help us identify the viability and biological variation of the tested single cell.

Electrochemical immunosensors for the detection of cytokine tumor necrosis factor alpha: A review

In this review, we focus on recent developments in nonlabeled@label-free and labeled@sandwich assay concepts of tumor necrosis factor-alpha (TNF-α) using numerous electrochemical approaches. The fundamental role of such nanostructured materials for the improvement of the analytical response and thus the analytical figures of merit of various TNF-α sensing operations were revealed. Also, this examination focused on recent developments in immuno-electrochemical cytokine TNF-α sensors based on nanostructured materials from 2006 to 2019.

Single Cell Analysis of Neutrophils NETs by Microscopic LSPR Imaging System

A simple microengraving cell monitoring method for neutrophil extracellular traps (NETs) released from single neutrophils has been realized using a polydimethylsiloxane (PDMS) microwell array (MWA) sheet on a plasmon chip platform. An imbalance between NETs formation and the succeeding degradation (NETosis) are considered associated with autoimmune disease and its pathogenesis. Thus, an alternative platform that can conduct monitoring of this activity on single cell level at minimum cost but with great sensitivity is greatly desired. The developed MWA plasmon chips allow single cell isolation of neutrophils from 150 µL suspension (6.0 × 10⁵ cells/mL) with an efficiency of 36.3%; 105 microwells with single cell condition. To demonstrate the utility of the chip, trapped cells were incubated between 2 to 4 h after introducing with 100 nM phorbol 12-myristate 13-acetate (PMA) before measurement. Under observation using a hyperspectral imaging system that allows high-throughput screening, the neutrophils stimulated by PMA solution show a significant release of fibrils and NETs after 4 h, with observed maximum areas between 314–758 µm². An average absorption peak wavelength shows a redshift of Δλ = 1.5 nm as neutrophils release NETs.

Real-time monitoring of DNA immobilization and detection of DNA polymerase activity by a microfluidic nanoplasmonic platform

DNA polymerase catalyzes the replication of DNA, one of the key steps in cell division. The control and understanding of this reaction owns great potential for the fundamental study of DNA-enzyme interactions. In this context, we developed a label-free microfluidic biosensor platform based on the principle of localized surface plasmon resonance (LSPR) to detect the DNA-polymerase reaction in real-time. Our microfluidic LSPR chip integrates a polydimethylsiloxane (PDMS) channel bonded with a nanoplasmonic substrate, which consists of densely packed mushroom-like nanostructures with silicon dioxide stems (~40 nm) and gold caps (~22 nm), with an average spacing of 19 nm. The LSPR chip was functionalized with single-stranded DNA (ssDNA) template (T30), spaced with hexanedithiol (HDT) in a molar ratio of 1:1. The DNA primer (P8) was then attached to T30, and the second strand was subsequently elongated by DNA polymerase assembling nucleotides from the surrounding fluid. All reaction steps were detected in-situ inside the microfluidic LSPR chip, at room temperature, in real-time, and label-free. In addition, the sensor response was successfully correlated with the amount of DNA and HDT molecules immobilized on the LSPR sensor surface. Our platform represents a benchmark in developing microfluidic LSPR chips for DNA-enzyme interactions, further driving innovations in biosensing technologies.

Single-Cell Protein Secretion Detection and Profiling

Secreted proteins play important roles in mediating various biological processes such as cell-cell communication, differentiation, migration, and homeostasis at the population or tissue level. Here, we review bioanalytical technologies and devices for detecting protein secretions from single cells. We begin by discussing conventional approaches followed by detailing the latest advances in microengineered systems for detecting single-cell protein secretions with an emphasis on multiplex measurement. These platforms include droplet microfluidics, micro-/nanowell-based assays, and microchamber-based assays, among which the advantages and limitations are compared. Microscale systems also enable the tracking of protein secretion dynamics in single cells, further empowering the study of the cell-cell communication network. Looking forward, we discuss the remaining challenges and future opportunities that will transform basic research of cellular secretion functions at the systems level and the clinical applications for immune monitoring and cancer treatment.

Magnet Patterned Superparamagnetic Fe3 O4 /Au Core-Shell Nanoplasmonic Sensing Array for Label-Free High Throughput Cytokine Immunoassay

Rapid and accurate immune monitoring plays a decisive role in effectively treating immune-related diseases especially at point-of-care, where an immediate decision on treatment is needed upon precise determination of the patient immune status. Derived from the emerging clinical demands, there is an urgent need for a cytokine immunoassay that offers unprecedented sensor performance with high sensitivity, throughput, and multiplexing capability, as well as short turnaround time at low system complexity, manufacturability, and scalability. In this paper, a label-free, high throughput cytokine immunoassay based on a magnet patterned Fe₃ O₄ /Au core-shell nanoparticle (FACSNP) sensing array is developed. By exploiting the unique superparamagnetic and plasmonic properties of the core-shell nanomaterials, a facile microarray patterning technique is established that allows the fabrication of a uniform, self-assembled microarray on a large surface area with remarkable tunability and scalability. The sensing performance of the FACSNP microarray is validated by real-time detection of four cytokines in complex biological samples, showing high sensitivity (≈20 pg mL^-1 ), selectivity and throughput with excellent statistical accuracy. The developed immunoassay is successfully applied for rapid determination of the functional immunophenotype of leukemia tumor-associated macrophages, manifesting its potential clinical applications for real-time immune monitoring, early cancer detection, and therapeutic drug stratification toward personalized medicine.

An integrated adipose-tissue-on-chip nanoplasmonic biosensing platform for investigating obesity-associated inflammation

Although many advanced biosensing techniques have been proposed for cytokine profiling, there are no clinically available methods that integrate high-resolution immune cell monitoring and in situ multiplexed cytokine detection together in a biomimetic tissue microenvironment. The primary challenge arises due to the lack of suitable label-free sensing techniques and difficulty for sensor integration. In this work, we demonstrated a novel integration of a localized-surface plasmon resonance (LSPR)-based biosensor with a biomimetic microfluidic 'adipose-tissue-on-chip' platform for an in situ label-free, high-throughput and multiplexed cytokine secretion analysis of obese adipose tissue. Using our established adipose-tissue-on-chip platform, we were able to monitor the adipose tissue initiation, differentiation, and maturation and simulate the hallmark formation of crown-like structures (CLSs) during pro-inflammatory stimulation. With integrated antibody-conjugated LSPR barcode sensor arrays, our platform enables simultaneous multiplexed measurements of pro-inflammatory (IL-6 and TNF-α) and anti-inflammatory (IL-10 and IL-4) cytokines secreted by the adipocytes and macrophages. As a result, our adipose-tissue-on-chip platform is capable of identifying stage-specific cytokine secretion profiles from a complex milieu during obesity progression, highlighting its potential as a high-throughput preclinical readout for personalized obesity treatment strategies.

Smart Cell Culture Systems: Integration of Sensors and Actuators into Microphysiological Systems

Technological advances in microfabrication techniques in combination with organotypic cell and tissue models have enabled the realization of microphysiological systems capable of recapitulating aspects of human physiology in vitro with great fidelity. Concurrently, a number of analysis techniques has been developed to probe and characterize these model systems. However, many assays are still performed off-line, which severely compromises the possibility of obtaining real-time information from the samples under examination, and which also limits the use of these platforms in high-throughput analysis. In this review, we focus on sensing and actuation schemes that have already been established or offer great potential to provide in situ detection or manipulation of relevant cell or tissue samples in microphysiological platforms. We will first describe methods that can be integrated in a straightforward way and that offer potential multiplexing and/or parallelization of sensing and actuation functions. These methods include electrical impedance spectroscopy, electrochemical biosensors, and the use of surface acoustic waves for manipulation and analysis of cells, tissue, and multicellular organisms. In the second part, we will describe two sensor approaches based on surface-plasmon resonance and mechanical resonators that have recently provided new characterization features for biological samples, although technological limitations for use in high-throughput applications still exist.

3D Hybrid Small Scale Devices

Interfacing nano/microscale elements with biological components in 3D contexts opens new possibilities for mimicry, bionics, and augmentation of organismically and anatomically inspired materials. Abiotic nanoscale elements such as plasmonic nanostructures, piezoelectric ribbons, and thin film semiconductor devices interact with electromagnetic fields to facilitate advanced capabilities such as communication at a distance, digital feedback loops, logic, and memory. Biological components such as proteins, polynucleotides, cells, and organs feature complex chemical synthetic networks that can regulate growth, change shape, adapt, and regenerate. Abiotic and biotic components can be integrated in all three dimensions in a well-ordered and programmed manner with high tunability, versatility, and resolution to produce radically new materials and hybrid devices such as sensor fabrics, anatomically mimetic microfluidic modules, artificial tissues, smart prostheses, and bionic devices. In this critical Review, applications of small scale devices in 3D hybrid integration, biomicrofluidics, advanced prostheses, and bionic organs are discussed.

Label-Free Optofluidic Nanobiosensor Enables Real-Time Analysis of Single-Cell Cytokine Secretion

Single-cell analysis of cytokine secretion is essential to understand the heterogeneity of cellular functionalities and develop novel therapies for multiple diseases. Unraveling the dynamic secretion process at single-cell resolution reveals the real-time functional status of individual cells. Fluorescent and colorimetric-based methodologies require tedious molecular labeling that brings inevitable interferences with cell integrity and compromises the temporal resolution. An innovative label-free optofluidic nanoplasmonic biosensor is introduced for single-cell analysis in real time. The nanobiosensor incorporates a novel design of a multifunctional microfluidic system with small volume microchamber and regulation channels for reliable monitoring of cytokine secretion from individual cells for hours. Different interleukin-2 secretion profiles are detected and distinguished from single lymphoma cells. The sensor configuration combined with optical spectroscopic imaging further allows us to determine the spatial single-cell secretion fingerprints in real time. This new biosensor system is anticipated to be a powerful tool to characterize single-cell signaling for basic and clinical research.

Optofluidic bioanalysis: fundamentals and applications

Over the past decade, optofluidics has established itself as a new and dynamic research field for exciting developments at the interface of photonics, microfluidics, and the life sciences. The strong desire for developing miniaturized bioanalytic devices and instruments, in particular, has led to novel and powerful approaches to integrating optical elements and biological fluids on the same chip-scale system. Here, we review the state-of-the-art in optofluidic research with emphasis on applications in bioanalysis and a focus on waveguide-based approaches that represent the most advanced level of integration between optics and fluidics. We discuss recent work in photonically reconfigurable devices and various application areas. We show how optofluidic approaches have been pushing the performance limits in bioanalysis, e.g. in terms of sensitivity and portability, satisfying many of the key requirements for point-of-care devices. This illustrates how the requirements for bianalysis instruments are increasingly being met by the symbiotic integration of novel photonic capabilities in a miniaturized system.

Plasmonic nanohole array biosensor for label-free and real-time analysis of live cell secretion

Cell secretion dynamics plays a central role in physiological and disease processes. Due to its various temporal profiles, it is essential to implement a precise detection scheme for continuous monitoring of secretion in real time. The current fluorescent and colorimetric approaches hinder such applications due to their multiple time-consuming steps, molecular labeling, and especially the 'snapshot' endpoint readouts. Here, we develop a nanoplasmonic biosensor for real-time monitoring of live cell cytokine secretion in a label-free configuration. Our nanoplasmonic biosensor is composed of gold nanohole arrays supporting extraordinary optical transmission (EOT), which enables sensitive and high-throughput analysis of biomolecules. The nanobiosensor is integrated with an adjustable microfluidic cell module for the analysis of live cells under well-controlled culture conditions. We achieved an outstanding sensitivity for the detection of vascular endothelial growth factor (VEGF) directly in complex cell media. Significantly, the secretion dynamics from live cancer cells were monitored and quantified for 10 hours while preserving good cell viability. This novel approach of probing cytokine secretion activity is compatible with conventional inverted microscopes found in a common biology laboratory. With its simple optical set-up and label-free detection configuration, we anticipate our nanoplasmonic biosensor to be a powerful tool as a lab-on-chip device to analyze cellular activities for fundamental cell research and biotechnologies.

Biotunable Nanoplasmonic Filter on Few-Layer MoS2 for Rapid and Highly Sensitive Cytokine Optoelectronic Immunosensing

Monitoring of the time-varying immune status of a diseased host often requires rapid and sensitive detection of cytokines. Metallic nanoparticle-based localized surface plasmon resonance (LSPR) biosensors hold promise to meet this clinical need by permitting label-free detection of target biomolecules. These biosensors, however, continue to suffer from relatively low sensitivity as compared to conventional immunoassay methods that involve labeling processes. Their response speeds also need to be further improved to enable rapid cytokine quantification for critical care in a timely manner. In this paper, we report an immunobiosensing device integrating a biotunable nanoplasmonic optical filter and a highly sensitive few-layer molybdenum disulfide (MoS₂) photoconductive component, which can serve as a generic device platform to meet the need of rapid cytokine detection with high sensitivity. The nanoplasmonic filter consists of anticytokine antibody-conjugated gold nanoparticles on a SiO₂ thin layer that is placed 170 μm above a few-layer MoS₂ photoconductive flake device. The principle of the biosensor operation is based on tuning the delivery of incident light to the few-layer MoS₂ photoconductive flake thorough the nanoplasmonic filter by means of biomolecular surface binding-induced LSPR shifts. The tuning is dependent on cytokine concentration on the nanoplasmonic filter and optoelectronically detected by the few-layer MoS₂ device. Using the developed optoelectronic biosensor, we have demonstrated label-free detection of IL-1β, a pro-inflammatory cytokine, with a detection limit as low as 250 fg/mL (14 fM), a large dynamic range of 10⁶, and a short assay time of 10 min. The presented biosensing approach could be further developed and generalized for point-of-care diagnosis, wearable bio/chemical sensing, and environmental monitoring.

Optics-Integrated Microfluidic Platforms for Biomolecular Analyses

Compared with conventional optical methods, optics implemented on microfluidic chips provide small, and often much cheaper ways to interrogate biological systems from the level of single molecules up to small model organisms. The optical probing of single molecules has been used to investigate the mechanical properties of individual biological molecules; however, multiplexing of these measurements through microfluidics and nanofluidics confers many analytical advantages. Optics-integrated microfluidic systems can significantly simplify sample processing and allow a more user-friendly experience; alignments of on-chip optical components are predetermined during fabrication and many purely optical techniques are passively controlled. Furthermore, sample loss from complicated preparation and fluid transfer steps can be virtually eliminated, a particularly important attribute for biological molecules at very low concentrations. Excellent fluid handling and high surface area/volume ratios also contribute to faster detection times for low abundance molecules in small sample volumes. Although integration of optical systems with classical microfluidic analysis techniques has been limited, microfluidics offers a ready platform for interrogation of biophysical properties. By exploiting the ease with which fluids and particles can be precisely and dynamically controlled in microfluidic devices, optical sensors capable of unique imaging modes, single molecule manipulation, and detection of minute changes in concentration of an analyte are possible.

A Large-Area Nanoplasmonic Sensor Fabricated by Rapid Thermal Annealing Treatment for Label-Free and Multi-Point Immunoglobulin Sensing

Immunoglobulins are important biomarkers to evaluate the immune status or development of infectious diseases. To provide timely clinical treatments, it is important to continuously monitor the level of multiple immunoglobulins. Localized surface plasmon resonance (LSPR)-based nanoplasmonic sensors have been demonstrated for multiplex immunoglobulins detection. However, the sensor fabrication process is usually slow and complicated, so it is not accessible for large-area and batch fabrication. Herein, we report a large-area (2 cm × 2 cm) nanofabrication method using physical vapor deposition followed by a rapid thermal annealing treatment. To optimize the sensor performance, we systematically characterized three fabrication conditions, including (1) the deposition thickness; (2) the maximum annealing temperature, and (3) the annealing time. The corresponding absorbance spectrum profile and surface morphology of the nanostructures were observed by a UV-VIS spectrometer and atomic force microscopy. We then tested the sensitivity of the sensor using a glucose solution at different concentrations. The results showed that the sensor with 10 nm gold deposition thickness under 5-min 900 °C rapid thermal annealing can achieve the highest sensitivity (189 nm RIU⁻¹). Finally, we integrated this nanoplasmonic sensor with a microchannel and a motorized stage to perform a 10-spot immunoglobulin detection in 50 min. Based on its real-time, dynamic and multi-point analyte detection capability, the nanoplasmonic sensor has the potential to be applied in high-throughput or multiplex immunoassay analysis, which would be beneficial for disease diagnosis or biomedical research in a simple and cost-effective platform.

Sensitive Cytokine Assay Based on Optical Fiber Allowing Localized and Spatially Resolved Detection of Interleukin-6

We demonstrated a cytokine detection device based on gold nanoparticle modified silica optical fiber for the monitoring of locally variable cytokine interleukin-6 (IL-6) concentrations using a sandwich immunoassay scheme. The fiber is designed to be introduced into an intrathecal catheter with micrometer-sized holes drilled along its length to enable fluid exchange between the outside and inside of the catheter. An exposed optical fiber (diameter 125 μm) modified with a layer of gold nanoparticles was functionalized with the IL-6 capture antibody to form the sensing interface. The immunocapture device was incubated with a cytokine solution to capture the analyte. The device was then exposed to the IL-6 detection antibody which was loaded on the fluorescently labeled magnetic nanoparticles, making it possible to quantify the cytokine concentration based on the intensity of fluorescence. A reliable method for quantifying the fluorescent signal on a 3D structure was developed. This device was applied to the detection of cytokine IL-6 with the low limit of detection of 1 pg mL^-1 in a sample volume of 1 μL. The device has the linear detection range of 1-400 pg mL^-1 and spatial resolution on the order of 200-450 μm, and it is capable of detecting localized IL-6 secreted by live BV2 cells following their liposaccharide stimulation. This biological detection system is suitable for monitoring multiple health conditions.

Decoration of Reduced Graphene Oxide Nanosheets with Aryldiazonium Salts and Gold Nanoparticles toward a Label-Free Amperometric Immunosensor for Detecting Cytokine Tumor Necrosis Factor-α in Live Cells

In this study, a label-free electrochemical immunosensor was developed for detection of cytokine tumor necrosis factor-alpha (TNF-α). First, AuNPs loaded reduced graphene oxides nanocomposites (RGO-ph-AuNP) were prepared, and then, a mixed layer of 4-carbxyphenyl and 4-aminophenyl phosphorylcholine (PPC) was modified to the surface of AuNPs for the subsequent modification of anti-TNF-α capture antibody (Ab₁) to form the capture surface (Au-RGO-ph-AuNP-ph-PPC(-ph-COOH)) for the analyte TNF-α with the antifouling property. For reporting the presence of analyte, the anti-TNF-α detection antibody (Ab₂) was modified to the graphene oxides which have been modified with the 4-ferrocenylaniline through diazonium chemistry to form Ab₂-GO-ph-Fc. Then, a sandwich assay was formed on gold surfaces for the quantitative detection of TNF-α based on the electrochemical signal of ferrocene. X-ray photoelectron spectra (XPS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), UV-vis, and electrochemistry were used for characterization of the stepwise fabrications on the interface. The prepared electrochemical immunosensor was successfully used for the detection of TNF-α over the range of 0.1-150 pg mL^-1. The lowest detection limit of this immunosensor is 0.1 pg mL^-1 TNF-α in 50 mM phosphate buffer at pH 7.0. The fabricated immunosensor provided high selectivity and stability and can be used to detect TNF-α secreted by live BV-2 cells with comparable accuracy to enzyme-linked immunosorbent assay (ELISA) but with lower limit of detection.

High sensitivity plasmonic biosensor based on nanoimprinted quasi 3D nanosquares for cell detection

Quasi three-dimensional (3D) plasmonic nanostructures consisting of Au nanosquares on top of SU-8 nanopillars and Au nanoholes on the bottom were developed and fabricated using nanoimprint lithography with simultaneous thermal and UV exposure. These 3D plasmonic nanostructures were used to detect cell concentration of lung cancer A549 cells, retinal pigment epithelial (RPE) cells, and breast cancer MCF-7 cells. Nanoimprint technology has the advantage of producing high uniformity plasmonic nanostructures for such biosensors. Multiple resonance modes were observed in these quasi 3D plasmonic nanostructures. The hybrid coupling of localized surface plasmon resonances and Fabry-Perot cavity modes in the quasi 3D nanostructures resulted in high sensitivity of 496 nm/refractive index unit. The plasmonic resonance peak wavelength and sensitivity could be tuned by varying the Au thickness. Resonance peak shifts for different cells at the same concentration were distinct due to their different cell area and confluency. The cell concentration detection limit covered a large range of 5 × 10(2) to 1 × 10(7) cells ml(-1) with these new plasmonic nanostructures. They also provide a large resonance peak shift of 51 nm for as little as 0.08 cells mm(-2) of RPE cells for high sensitivity cell detection.

Multiplexed Nanoplasmonic Temporal Profiling of T-Cell Response under Immunomodulatory Agent Exposure

Immunomodulatory drugs—agents regulating the immune response—are commonly used for treating immune system disorders and minimizing graft versus host disease in persons receiving organ transplants. At the cellular level, immunosuppressant drugs are used to inhibit pro-inflammatory or tissue-damaging responses of cells. However, few studies have so far precisely characterized the cellular-level effect of immunomodulatory treatment. The primary challenge arises due to the rapid and transient nature of T-cell immune responses to such treatment. T-cell responses involve a highly interactive network of different types of cytokines, which makes precise monitoring of drug-modulated T-cell response difficult. Here, we present a nanoplasmonic biosensing approach to quantitatively characterize cytokine secretion behaviors of T cells with a fine time-resolution (every 10 min) that are altered by an immunosuppressive drug used in the treatment of T-cell-mediated diseases. With a microfluidic platform integrating antibody-conjugated gold nanorod (AuNR) arrays, the technique enables simultaneous multi-time-point measurements of pro-inflammatory (IL-2, IFN-γ, and TNF-α) and anti-inflammatory (IL-10) cytokines secreted by T cells. The integrated nanoplasmonic biosensors achieve precise measurements with low operating sample volume (1 μL), short assay time (∼30 min), heightened sensitivity (∼20–30 pg/mL), and negligible sensor crosstalk. Data obtained from the multicytokine secretion profiles with high practicality resulting from all of these sensing capabilities provide a comprehensive picture of the time-varying cellular functional state during pharmacologic immunosuppression. The capability to monitor cellular functional response demonstrated in this study has great potential to ultimately permit personalized immunomodulatory treatment.

Microfluidic perfusion systems for secretion fingerprint analysis of pancreatic islets: applications, challenges and opportunities

A secretome signature is a heterogeneous profile of secretions present in a single cell type. From the secretome signature a smaller panel of proteins, namely a secretion fingerprint, can be chosen to feasibly monitor specific cellular activity. Based on a thorough appraisal of the literature, this review explores the possibility of defining and using a secretion fingerprint to gauge the functionality of pancreatic islets of Langerhans. It covers the state of the art regarding microfluidic perfusion systems used in pancreatic islet research. Candidate analytical tools to be integrated within microfluidic perfusion systems for dynamic secretory fingerprint monitoring were identified. These analytical tools include patch clamp, amperometry/voltametry, impedance spectroscopy, field effect transistors and surface plasmon resonance. Coupled with these tools, microfluidic devices can ultimately find applications in determining islet quality for transplantation, islet regeneration and drug screening of therapeutic agents for the treatment of diabetes.