Trends in Multiplex Immunoassays for In Vitro Diagnostics and Point-of-Care Testing.

The tremendous advances in multiplex immunoassays (MIAs) are leading to novel in vitro diagnostics (IVD) and point-of-care testing (POCT) [...].

In Vitro Diagnostic Assays for COVID-19: Recent Advances and Emerging Trends.

There have been tremendous advances in in vitro diagnostic (IVD) assays for coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The main IVD assays used for COVID-19 employ real-time reverse transcriptase polymerase chain reaction (RT-PCR) that takes a few hours. But the assay duration has been shortened to 45 min by Cepheid. Of interest is the point-of-care (POC) molecular assay by Abbott that decreased the assay duration to just 5 min. Most molecular tests have been approved by the United States Food and Drug Administration (FDA) under emergency use authorization (EUA) and are Conformité Européenne (CE) marked. A wide range of serology immunoassays (IAs) have also been developed that complement the molecular assays for the diagnosis of COVID-19. The most prominent IAs are automated chemiluminescent IA (CLIA), manual ELISA, and rapid lateral flow IA (LFIA), which detect the immunoglobulin M (IgM) and immunoglobulin G (IgG) produced in persons in response to SARS-CoV-2 infection. The ongoing research efforts and advances in complementary technologies will pave the way to new POC IVD assays in the coming months. However, the performance of IVD assays needs to be critically evaluated before they are employed for the clinical diagnosis of COVID-19.

Carbon nanotube bottles for incorporation, release and enhanced cytotoxic effect of cisplatin.

Carbon nanotubes (CNTs) have emerged as promising drug delivery systems particularly for cancer therapy, due to their abilities to overcome some of the challenges faced by cancer treatment, namely non-specificity, poor permeability into tumour tissues, and poor stability of anticancer drugs. Encapsulation of anticancer agents inside CNTs provides protection from external deactivating agents. However, the open ends of the CNTs leave the encapsulated drugs exposed to the environment and eventually their uncontrolled release before reaching the desired target. In this study, we report the successful encapsulation of cisplatin, a FDA-approved chemotherapeutic drug, into multi-walled carbon nanotubes and the capping at the ends with functionalised gold nanoparticles to achieve a "carbon nanotube bottle" structure. In this proof-of-concept study, these caps did not prevent the encapsulation of drug in the inner space of CNTs; on the contrary, we achieved higher drug loading inside the nanotubes in comparison with data reported in literature. In addition, we demonstrated that encapsulated cisplatin could be delivered in living cells under physiological conditions to exert its pharmacological action.

Point-of-Care Diagnostics: Recent Advances and Trends.

Recent years have witnessed tremendous advances in point-of-care diagnostics (POCD), which are a result of continuous developments in biosensors, microfluidic, bioanalytical platforms, assay formats, lab-on-a-chip technologies, and complementary technologies. This special issue targets the critical advances in POCD and provides guided insights and directions for future research.

A Smartphone-Based Colorimetric Reader for Human C-Reactive Protein Immunoassay.

A smartphone-based colorimetric reader (SBCR), comprising a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4, or iPhone 5s) and a custom-made dark hood and base holder assembly, is used for human C-reactive protein (CRP) immunoassay. A 96-well microtiter plate (MTP) is positioned on the gadget's screensaver to provide white light-based bottom illumination only in the specific regions corresponding to the well's bottom. The images captured by the smartphone's back camera are analyzed by a novel image processing algorithm. Based on one-step kinetics-based human C-reactive protein immunoassay (IA), SBCR is evaluated and compared with a commercial MTP reader (MTPR). For analysis of CRP spiked in diluted human whole blood and plasma as well as CRP in clinical plasma samples, SBCR exhibits the same precision, dynamic range, detection limit, and sensitivity as MTPR for the developed IA (DIA). Considering its compactness, low cost, advanced features and a remarkable computing power, SBCR is an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC testing (POCT).

Emerging Human Fetuin A Assays for Biomedical Diagnostics.

Human fetuin A (HFA) plays a prominent pathophysiological role in numerous diseases and pathophysiological conditions with considerable biomedical significance; one example is the formation of calciprotein particles in osteoporosis and impaired calcium metabolisms. With impressive advances in in vitro diagnostic assays during the last decade, ELISAs have become a workhorse in routine clinical diagnostics. Recent diagnostic formats involve high-sensitivity immunoassay procedures, surface plasmon resonance, rapid immunoassay chemistries, signal enhancement, and smartphone detection. The current trend is toward fully integrated lab-on-chip platforms with smartphone readouts, enabling health-care practitioners and even patients to monitor pathological changes in biomarker levels. This review provides a critical analysis of advances made in HFA assays along with the challenges and future prospects.

Immunosensing procedures for carcinoembryonic antigen using graphene and nanocomposites.

Two-dimensional (2D) graphene, sp2-hybridized carbon, and its two major derivatives, graphene oxide (GO) and reduced graphene oxide (rGO) have played an important role in immunoassays (IAs) and immunosensing (IMS) platforms for the detection of carcinoembryonic antigen (CEA), an implicated tumor biomarker found in several types of cancer. The graphene family with high surface area is functionalized to form stable nanocomposites with gold nanoparticles (AuNPs) and electron mediators. The capture anti-CEA antibody (Ab) with high density can be anchored on AuNPs of such composites to provide remarkable detection sensitivity, significantly below the level found in normal subjects and cancer patients. Electrochemical and fluorescence/chemiluminescence-quenching properties of graphene-based nanocomposites are exploited in various detection schemes. Future endeavors are envisioned for the development of an array platform with high-throughput for CEA together with other tumor biomarkers and C-reactive protein, a universal biomarker for infection and inflammation. The ongoing efforts dedicated to the replacement of a lab-based detector by a cellphone with smart applications will further enable cost-effective and frequent monitoring of CEA in order to establish its clinical relevance and provide tools for real-time monitoring of patients during chemotherapy.

A rapid and highly sensitive immunoassay format for human lipocalin-2 using multiwalled carbon nanotubes.

A sensitive and rapid sandwich immunoassay (IA) was developed for human lipocalin-2 (LCN2) by functionalizing a KOH-treated polystyrene microtiter plate with multiwalled carbon nanotubes (MWCNTs) dispersed in 3-aminoproyltriethoxysilane (APTES). The significantly increased surface area due to the presence of MWCNTs led to a high immobilization density of 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) activated anti-LCN2 capture antibodies (Ab). The anti-LCN2 Ab-bound MTPs were stable for 6 weeks when stored in 0.1M PBS, pH 7.4 at 4°C. The IA detects LCN2 from 0.6 to 5120pgmL-1 with a limit of detection (LOD) and limit of quantification (LOQ) of 0.9pgmL-1 and 6pgmL-1, respectively. The assay offered a ~50-fold lower LOD and ~3-fold faster IA, compared to a commercial sandwich enzyme-linked immunosorbent assay kit.

Surface plasmon resonance-based immunoassay for procalcitonin.

A surface plasmon resonance (SPR) biosensor has been developed for rapid immunoassay of procalcitonin (PCT) with high detection sensitivity and reproducibility. The 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)-activated protein A (PrA), diluted in 1% (v/v) 3-aminopropyltriethoxysilane (APTES) was dispensed on a KOH-treated Au-coated SPR chip, resulting in the covalent binding of PrA in 30 min. This "single-step" PrA immobilization strategy led to the oriented binding of the anti-PCT antibody (Ab) on a PrA-functionalized gold (Au) chip. The leach-proof immobilization procedure is five-fold faster than conventional counterparts, enabling high detection specificity and reproducibility. The IA detects 4-324 ng mL(-1) of PCT with a limit of detection (LOD) and a limit of quantification (LOQ) of 4.2 ng mL(-1) and 9.2 ng mL(-1), respectively. It was capable of detecting PCT in real sample matrices and patient samples with high precision. The Ab-bound SPR chips were stable for more than five weeks.

Microfluidic solutions enabling continuous processing and monitoring of biological samples: A review.

The last decade has witnessed tremendous advances in employing microfluidic solutions enabling Continuous Processing and Monitoring of Biological Samples (CPMBS), which is an essential requirement for the control of bio-processes. The microfluidic systems are superior to the traditional inline sensors due to their ability to implement complex analytical procedures, such as multi-step sample preparation, and enabling the online measurement of parameters. This manuscript provides a backgound review of microfluidic approaches employing laminar flow, hydrodynamic separation, acoustophoresis, electrophoresis, dielectrophoresis, magnetophoresis and segmented flow for the continuous processing and monitoring of biological samples. The principles, advantages and limitations of each microfluidic approach are described along with its potential applications. The challenges in the field and the future directions are also provided.

Bioanalytical advances in assays for C-reactive protein.

This review presents advances in assays for human C-reactive protein (CRP), the most important biomarker of infection and inflammation for a plethora of diseases and pathophysiological conditions. Routine assays in clinical settings are based on analyzers, enzyme-linked immunosorbent assays and lateral flow assays. However, assays encompassing novel sensing schemes, improved chemistry, signal enhancement, lab-on-a-chip, microfluidics and smartphone detection, have emerged in recent years. The incorporation of immune-transducing chips or sensing interfaces with nanomaterials enables multiplexing analysis of CRP with co-existing biomarkers. However, there are still considerable challenges in the development of rapid diagnostics for both pentameric and monomeric CRP forms.

Emerging Technologies for Next-Generation Point-of-Care Testing.

Considerable advances in point-of-care testing (POCT) devices stem from innovations in cellphone (CP)-based technologies, paper-based assays (PBAs), lab-on-a-chip (LOC) platforms, novel assay formats, and strategies for long-term reagent storage. Various commercial CP platforms have emerged to provide cost-effective mobile health care and personalized medicine. Such assay formats, as well as low-cost PBAs and LOC-based assays, are paving the way to robust, automated, simplified, and cost-effective POCT. Strategies have also been devised to stabilize reagent storage and usage at ambient temperature. Nevertheless, successful commercialization and widespread implementation of such clinically viable technologies remain subject to several challenges and pending issues.

A rapid sandwich immunoassay for human fetuin A using agarose-3-aminopropyltriethoxysilane modified microtiter plate.

A rapid sandwich immunoassay (IA) with enhanced signal response for human fetuin A (HFA) was developed by modifying the surface of a KOH-treated polystyrene microtiter plate (MTP) with agarose and 3-aminopropyltriethoxysilane (APTES). The agarose-APTES complex binds covalently to the hydroxyl moiety of the MTP plate to serve as a binding platform for bioconjugation of EDC-activated anti-HFA antibody (Ab) via carbodiimide coupling. The one-step kinetics-based sandwich enzyme-linked immunosorbent assay (ELISA) enabled the detection of HFA in 30 min with a limit of detection (LOD) and a linear range of 0.02 ng mL(-1) and 1-243 ng mL(-1), respectively. It detected HFA spiked in diluted human whole blood and serum, and HFA in ethylenediaminetetraacetic acid (EDTA)-plasma of patients with high precision similar to that of conventional ELISA. The anti-HFA Ab-bound agarose-functionalized MTPs retained their functional activity after 6 weeks of storage in 0.1 M PBS, pH 7.4 at 4 °C.

Graphene-based rapid and highly-sensitive immunoassay for C-reactive protein using a smartphone-based colorimetric reader.

A novel immunoassay (IA) has been developed for human C-reactive protein (CRP), an important biomarker and tissue preserving factor for infection and inflammation. Graphene nanoplatelets (GNP) and 3-aminopropyltriethoxysilane (APTES) were admixed and covalently attached to a polystyrene based-microtiter plate (MTP), pretreated with KOH. The resulting surface served as a stable layer for the covalent attachment of the anti-human CRP antibody. The IA procedure was based on the one-step kinetics-based sandwich IA employing a minimum number of process steps, whereas the enzymatic reaction solution was monitored by a smartphone-based colorimetric reader. With a limit of detection and a limit of quantification of 0.07ngmL(-1) and 0.9ngmL(-1), it precisely detected CRP spiked in diluted human whole blood and plasma as well as the CRP levels in clinical plasma samples. The results obtained for "real-world" patient samples agreed well with those of the conventional immunosorbent assay and the clinically-accredited analyzer-based IA. The antibody-bound GNP-functionalized MTPs retained its original activity after 6 weeks of storage in 0.1M PBS, pH 7.4 at 4°C.

A smartphone-based colorimetric reader for bioanalytical applications using the screen-based bottom illumination provided by gadgets.

A smartphone-based colorimetric reader (SBCR) was developed using a Samsung Galaxy SIII mini, a gadget (iPAD mini, iPAD4 or iPhone 5s), integrated with a custom-made dark hood and base holder assembly. The smartphone equipped with a back camera (5 megapixels resolution) was used for colorimetric imaging via the hood and base-holder assembly. A 96- or 24-well microtiter plate (MTP) was positioned on the gadget's screensaver that provides white light-based bottom illumination only in the specific regions corresponding to the bottom of MTP's wells. The pixel intensity of the captured images was determined by an image processing algorithm. The developed SBCR was evaluated and compared with a commercial MTP reader (MTPR) for three model assays: our recently developed human C-reactive protein sandwich enzyme-linked immunosorbent assay (ELISA), horseradish peroxidase direct ELISA, and bicinchoninic acid protein estimation assay. SBCR had the same precision, dynamic range, detection limit and sensitivity as MTPR for all three assays. With advanced microfabrication and data processing, SBCR will become more compact, lighter, inexpensive and enriched with more features. Therefore, SBCR with a remarkable computing power could be an ideal point-of-care (POC) colorimetric detection device for the next-generation of cost-effective POC diagnostics, immunoassays and diversified bioanalytical applications.

Rapid sandwich ELISA-based in vitro diagnostic procedure for the highly-sensitive detection of human fetuin A.

A rapid sandwich enzyme-linked immunosorbent assay (ELISA)-based in vitro diagnostic (IVD) procedure has been developed for human fetuin A (HFA), an important disease biomarker for inflammatory diseases as well as malignancies. In this simplified and cost-effective procedure, the EDC-activated anti-HFA antibody (Ab) was admixed with 1% (v/v) 3-aminopropyltriethoxysilane (APTES) in 1:1 (v/v) and dispensed in a KOH-pretreated microtiter plate (MTP). APTES formed a stable complex with the capture antibody that was in turn covalently bonded on the KOH-treated surface in 30 min. The resulting immunoassay (IA) format detects HFA with a dynamic range of 0.1-243 ng mL(-1), and a limit of detection (LOD) and analytical sensitivity of 0.3 ng mL(-1) and 1.0 ng mL(-1), respectively. For the determination of HFA spiked in diluted human whole blood and serum, and HFA in ethylenediaminetetraacetic acid (EDTA)-plasma of patients, the obtained analytical precision is similar to that of the conventional sandwich ELISA. The anti-HFA Ab-bound MTPs, stored at 4 °C in 0.1M PBS, pH 7.4, retained its biological activity for 8 weeks, thereby demonstrating excellent storage stability. This generic sandwich ELISA procedure can be extended for rapid, simplified and cost-effective detection of other disease biomarkers.

One-step kinetics-based immunoassay for the highly sensitive detection of C-reactive protein in less than 30 min.

This article reveals a rapid sandwich enzyme-linked immunosorbent assay (ELISA) for the highly sensitive detection of human C-reactive protein (CRP) in less than 30 min. It employs a one-step kinetics-based highly simplified and cost-effective sandwich ELISA procedure with minimal process steps. The procedure involves the formation of a sandwich immune complex on capture anti-human CRP antibody-bound Dynabeads in 15 min, followed by two magnet-assisted washings and one enzymatic reaction. The developed sandwich ELISA detects CRP in the dynamic range of 0.3 to 81 ng ml(-1) with a limit of detection of 0.4 ng ml(-1) and an analytical sensitivity of 0.7 ng ml(-1). It detects CRP spiked in diluted human whole blood and serum with high analytical precision, as confirmed by conventional sandwich ELISA. Moreover, the results of the developed ELISA for the determination of CRP in the ethylenediaminetetraacetic acid plasma samples of patients are in good agreement with those obtained by the conventional ELISA. The developed immunoassay has immense potential for the development of rapid and cost-effective in vitro diagnostic kits.

One-step antibody immobilization-based rapid and highly-sensitive sandwich ELISA procedure for potential in vitro diagnostics.

An improved enzyme-linked immunosorbent (ELISA) assay using one-step antibody immobilization has been developed for the detection of human fetuin A (HFA), a specific biomarker for atherosclerosis and hepatocellular carcinoma. The anti-HFA formed a stable complex with 3-aminopropyltriethoxysilane (APTES) by ionic and hydrophobic interactions. The complex adsorbed on microtiter plates exhibited a detection range of 4.9 pg mL(-1) to 20 ng mL(-1) HFA, with a limit of detection of 7 pg mL(-1). Furthermore, an analytical sensitivity of 10 pg mL(-1) was achieved, representing a 51-fold increase in sensitivity over the commercial sandwich ELISA kit. The results obtained for HFA spiked in diluted human whole blood and plasma showed the same precision as the commercial kit. When stored at 4°C in 0.1 M phosphate-buffered saline (PBS, pH 7.4), the anti-HFA bound microtiter plates displayed no significant decrease in their functional activity after two months. The new ELISA procedure was extended for the detection of C-reactive protein, human albumin and human lipocalin-2 with excellent analytical performance.

Cellphone-based devices for bioanalytical sciences.

During the last decade, there has been a rapidly growing trend toward the use of cellphone-based devices (CBDs) in bioanalytical sciences. For example, they have been used for digital microscopy, cytometry, read-out of immunoassays and lateral flow tests, electrochemical and surface plasmon resonance based bio-sensing, colorimetric detection and healthcare monitoring, among others. Cellphone can be considered as one of the most prospective devices for the development of next-generation point-of-care (POC) diagnostics platforms, enabling mobile healthcare delivery and personalized medicine. With more than 6.5 billion cellphone subscribers worldwide and approximately 1.6 billion new devices being sold each year, cellphone technology is also creating new business and research opportunities. Many cellphone-based devices, such as those targeted for diabetic management, weight management, monitoring of blood pressure and pulse rate, have already become commercially-available in recent years. In addition to such monitoring platforms, several other CBDs are also being introduced, targeting e.g., microscopic imaging and sensing applications for medical diagnostics using novel computational algorithms and components already embedded on cellphones. This report aims to review these recent developments in CBDs for bioanalytical sciences along with some of the challenges involved and the future opportunities.