Organic electrochemical transistor based immunosensor for prostate specific antigen (PSA) detection using gold nanoparticles for signal amplification

Automated and ultrasensitive point-of-care glycoprotein detection using boronate-affinity enhanced organic electrochemical transistor patch

Quantifying trace glycoproteins in biofluids requires ultrasensitive components, but feedback is not available in the current portable platforms of point-of-care (POC) diagnosis technologies. A compact and ultrasensitive bioelectrochemical patch was based on boronate-affinity amplified organic electrochemical transistors (BAAOECTs) for POC use was developed to overcome this dilemma. Benefit from the cascading signal enhancement deriving from boronate-affinity targeting multiple regions of glycoprotein and OECTs' inherent signal amplification capability, the BAAOECTs achieved a detection limit of 300 aM within 25 min, displaying about 3 orders of magnitude improvement in sensitivity compared with the commercial electrochemical luminescence (ECL) kit. By using a microfluidic chip, a microcontroller module, and a wireless sensing system, the testing workflows of the above patch was automated, allowing for running the sample-to-answer pipeline even in a resource-limited environment. The reliability of such portable biosensing platform is well recognized in clinical diagnostic applications of heart failure. Overall, the remarkable enhanced sensitivity and automated workflow of BAAOECTs biosensing platform provide a prospective and generalized design policy for expanding the POC diagnosis capabilities of glycoproteins.

Extended Review Concerning the Integration of Electrochemical Biosensors into Modern IoT and Wearable Devices

Electrochemical biosensors include a recognition component and an electronic transducer, which detect the body fluids with a high degree of accuracy. More importantly, they generate timely readings of the related physiological parameters, and they are suitable for integration into portable, wearable and implantable devices that are significant relative to point-of-care diagnostics scenarios. As an example, the personal glucose meter fundamentally improves the management of diabetes in the comfort of the patients' homes. This review paper analyzes the principles of electrochemical biosensing and the structural features of electrochemical biosensors relative to the implementation of health monitoring and disease diagnostics strategies. The analysis particularly considers the integration of the biosensors into wearable, portable, and implantable systems. The fundamental aim of this paper is to present and critically evaluate the identified significant developments in the scope of electrochemical biosensing for preventive and customized point-of-care diagnostic devices. The paper also approaches the most important engineering challenges that should be addressed in order to improve the sensing accuracy, and enable multiplexing and one-step processes, which mediate the integration of electrochemical biosensing devices into digital healthcare scenarios.

Healthcare Monitoring Sensors Based on Organic Transistors: Surface/Interface Strategy and Performance

Organic transistors possess inherent advantages such as flexibility, biocompatibility, customizable chemical structures, solution-processability, and amplifying capabilities, making them highly promising for portable healthcare sensor applications. Through convenient and diverse modifications at the material and device surfaces or interfaces, organic transistors allow for a wide range of sensor applications spanning from chemical and biological to physical sensing. In this comprehensive review, the surface and interface engineering aspect associated with four types of typical healthcare sensors is focused. The device operation principles and sensing mechanisms are systematically analyzed and highlighted, and particularly surface/interface functionalization strategies that contribute to the enhancement of sensing performance are focused. An outlook and perspective on the critical issues and challenges in the field of healthcare sensing using organic transistors are provided as well.

Applications of Pyrrole and Pyridine-based Heterocycles in Cancer Diagnosis and Treatment

BACKGROUND

The escalation of cancer worldwide is one of the major causes of economy burden and loss of human resources. According to the American Cancer Society, there will be 1,958,310 new cancer cases and 609,820 projected cancer deaths in 2023 in the United States. It is projected that by 2040, the burden of global cancer is expected to rise to 29.5 million per year, causing a death toll of 16.4 million. The hemostasis regulation by cellular protein synthesis and their targeted degradation is required for normal cell growth. The imbalance in hemostasis causes unbridled growth in cells and results in cancer. The DNA of cells needs to be targeted by chemotherapeutic agents for cancer treatment, but at the same time, their efficacy and toxicity also need to be considered for successful treatment.

OBJECTIVE

The objective of this study is to review the published work on pyrrole and pyridine, which have been prominent in the diagnosis and possess anticancer activity, to obtain some novel lead molecules of improved cancer therapeutic.

METHODS

A literature search was carried out using different search engines, like Sci-finder, Elsevier, ScienceDirect, RSC etc., for small molecules based on pyrrole and pyridine helpful in diagnosis and inducing apoptosis in cancer cells. The research findings on the application of these compounds from 2018-2023 were reviewed on a variety of cell lines, such as breast cancer, liver cancer, epithelial cancer, etc. Results: In this review, the published small molecules, pyrrole and pyridine and their derivatives, which have roles in the diagnosis and treatment of cancers, were discussed to provide some insight into the structural features responsible for diagnosis and treatment. The analogues with the chromeno-furo-pyridine skeleton showed the highest anticancer activity against breast cancer. The compound 5-amino-N-(1-(pyridin-4- yl)ethylidene)-1H-pyrazole-4-carbohydrazides was highly potent against HEPG2 cancer cell. Redaporfin is used for the treatment of cholangiocarcinoma, biliary tract cancer, cisplatin-resistant head and neck squamous cell carcinoma, and pigmentation melanoma, and it is in clinical trials for phase II. These structural features present a high potential for designing novel anticancer agents for diagnosis and drug development.

CONCLUSION

Therefore, the N- and C-substituted pyrrole and pyridine-based novel privileged small Nheterocyclic scaffolds are potential molecules used in the diagnosis and treatment of cancer. This review discusses the reports on the synthesis of such molecules during 2018-2023. The review mainly discusses various diagnostic techniques for cancer, which employ pyrrole and pyridine heterocyclic scaffolds. Furthermore, the anticancer activity of N- and C-substituted pyrrole and pyridine-based scaffolds has been described, which works against different cancer cell lines, such as MCF-7, A549, A2780, HepG2, MDA-MB-231, K562, HT- 29, Caco-2 cells, Hela, Huh-7, WSU-DLCL2, HCT-116, HBL-100, H23, HCC827, SKOV3, etc. This review will help the researchers to obtain a critical insight into the structural aspects of pyrrole and pyridine-based scaffolds useful in cancer diagnosis as well as treatment and design pathways to develop novel drugs in the future.

SpyDirect: A Novel Biofunctionalization Method for High Stability and Longevity of Electronic Biosensors

Electronic immunosensors are indispensable tools for diagnostics, particularly in scenarios demanding immediate results. Conventionally, these sensors rely on the chemical immobilization of antibodies onto electrodes. However, globular proteins tend to adsorb and unfold on these surfaces. Therefore, self-assembled monolayers (SAMs) of thiolated alkyl molecules are commonly used for indirect gold-antibody coupling. Here, a limitation associated with SAMs is revealed, wherein they curtail the longevity of protein sensors, particularly when integrated into the state-of-the-art transducer of organic bioelectronics-the organic electrochemical transistor. The SpyDirect method is introduced, generating an ultrahigh-density array of oriented nanobody receptors stably linked to the gold electrode without any SAMs. It is accomplished by directly coupling cysteine-terminated and orientation-optimized spyTag peptides, onto which nanobody-spyCatcher fusion proteins are autocatalytically attached, yielding a dense and uniform biorecognition layer. The structure-guided design optimizes the conformation and packing of flexibly tethered nanobodies. This biolayer enhances shelf-life and reduces background noise in various complex media. SpyDirect functionalization is faster and easier than SAM-based methods and does not necessitate organic solvents, rendering the sensors eco-friendly, accessible, and amenable to scalability. SpyDirect represents a broadly applicable biofunctionalization method for enhancing the cost-effectiveness, sustainability, and longevity of electronic biosensors, all without compromising sensitivity.

Genome-wide identification of transcriptional enhancers during human placental development and association with function, differentiation, and disease†

The placenta is a dynamic organ that must perform a remarkable variety of functions during its relatively short existence in order to support a developing fetus. These functions include nutrient delivery, gas exchange, waste removal, hormone production, and immune barrier protection. Proper placenta development and function are critical for healthy pregnancy outcomes, but the underlying genomic regulatory events that control this process remain largely unknown. We hypothesized that mapping sites of transcriptional enhancer activity and associated changes in gene expression across gestation in human placenta tissue would identify genomic loci and predicted transcription factor activity related to critical placenta functions. We used a suite of genomic assays [i.e., RNA-sequencing (RNA-seq), Precision run-on-sequencing (PRO-seq), and Chromatin immunoprecipitation-sequencing (ChIP-seq)] and computational pipelines to identify a set of >20 000 enhancers that are active at various time points in gestation. Changes in the activity of these enhancers correlate with changes in gene expression. In addition, some of these enhancers encode risk for adverse pregnancy outcomes. We further show that integrating enhancer activity, transcription factor motif analysis, and transcription factor expression can identify distinct sets of transcription factors predicted to be more active either in early pregnancy or at term. Knockdown of selected identified transcription factors in a trophoblast stem cell culture model altered the expression of key placental marker genes. These observations provide a framework for future mechanistic studies of individual enhancer-transcription factor-target gene interactions and have the potential to inform genetic risk prediction for adverse pregnancy outcomes.

Flexible and Stretchable Organic Electrochemical Transistors for Physiological Sensing Devices

Flexible and stretchable bioelectronics provides a biocompatible interface between electronics and biological systems and has received tremendous attention for in situ monitoring of various biological systems. Considerable progress in organic electronics has made organic semiconductors, as well as other organic electronic materials, ideal candidates for developing wearable, implantable, and biocompatible electronic circuits due to their potential mechanical compliance and biocompatibility. Organic electrochemical transistors (OECTs), as an emerging class of organic electronic building blocks, exhibit significant advantages in biological sensing due to the ionic nature at the basis of the switching behavior, low driving voltage (<1 V), and high transconductance (in millisiemens range). During the past few years, significant progress in constructing flexible/stretchable OECTs (FSOECTs) for both biochemical and bioelectrical sensors has been reported. In this regard, to summarize major research accomplishments in this emerging field, this review first discusses structure and critical features of FSOECTs, including working principles, materials, and architectural engineering. Next, a wide spectrum of relevant physiological sensing applications, where FSOECTs are the key components, are summarized. Last, major challenges and opportunities for further advancing FSOECT physiological sensors are discussed.

Organic electrochemical transistor-based immuno-sensor using platinum loaded CeO2 nanosphere-carbon nanotube and zeolitic imidazolate framework-enzyme-metal polyphenol network

This work demonstrates an organic electrochemical transistor (OECT) immuno-sensor with a detection limit down to fg mL^-1. The OECT device transforms the antibody-antigen interaction signal by using the zeolitic imidazolate framework-enzyme-metal polyphenol network nanoprobe, which can produce electro-active substance (H₂O₂) through the enzyme-catalytic reaction. The produced H₂O₂ is subsequently electrochemically oxidized at the platinum loaded CeO₂ nanosphere-carbon nanotube modified gate electrode, resulting in an amplified current response of the transistor device. This immuno-sensor realizes the selective determination of vascular endothelial growth factor 165 (VEGF₁₆₅) down to the concentration of 13.6 fg mL^-1. It also shows good applicable capacity for determining the VEGF₁₆₅ that human brain microvascular endothelial cells and U251 human glioblastomas cells secreted in the cell culture medium. The ultrahigh sensitivity of the immuno-sensor is derived from excellent performances of the nanoprobe for enzyme loading and the OECT device for H₂O₂ detection. This work may provide a general way to fabricate the OECT immuno-sensing device with high performances.

Organic thin-film transistors and related devices in life and health monitoring

The early determination of disease-related biomarkers can significantly improve the survival rate of patients. Thus, a series of explorations for new diagnosis technologies, such as optical and electrochemical methods, have been devoted to life and health monitoring. Organic thin-film transistor (OTFT), as a state-of-the-art nano-sensing technology, has attracted significant attention from construction to application owing to the merits of being label-free, low-cost, facial, and rapid detection with multi-parameter responses. Nevertheless, interference from non-specific adsorption is inevitable in complex biological samples such as body liquid and exhaled gas, so the reliability and accuracy of the biosensor need to be further improved while ensuring sensitivity, selectivity, and stability. Herein, we overviewed the composition, mechanism, and construction strategies of OTFTs for the practical determination of disease-related biomarkers in both body fluids and exhaled gas. The results show that the realization of bio-inspired applications will come true with the rapid development of high-effective OTFTs and related devices.

Electronic Supplementary Material

Supplementary material is available in the online version of this article at 10.1007/s12274-023-5606-1.

Device integration of electrochemical biosensors

Electrochemical biosensors incorporate a recognition element and an electronic transducer for the highly sensitive detection of analytes in body fluids. Importantly, they can provide rapid readouts and they can be integrated into portable, wearable and implantable devices for point-of-care diagnostics; for example, the personal glucose meter enables at-home assessment of blood glucose levels, greatly improving the management of diabetes. In this Review, we discuss the principles of electrochemical biosensing and the design of electrochemical biosensor devices for health monitoring and disease diagnostics, with a particular focus on device integration into wearable, portable and implantable systems. Finally, we outline the key engineering challenges that need to be addressed to improve sensing accuracy, enable multiplexing and one-step processes, and integrate electrochemical biosensing devices in digital health-care pathways.

Sensitive organic electrochemical transistor biosensors: Comparing single and dual gate functionalization and different COOH-functionalized bioreceptor layers

We developed new measurement configurations based on organic electrochemical transistors (OECTs). Three types of COOH-functionalized bioreceptor layers were deposited on indium tin oxide (ITO) electrodes on poly(ethylene terephthalate) (PET) substrates and their performance was tested using single gate functionalization organic electrochemical transistor (S-OECT) and dual gate functionalization organic electrochemical transistor (D-OECT) configurations. The three layers included one p-type semiconductor, one insulator, and one self-assembled layer, and the dual gates were connected in series through buffer solutions, so the solution-electrode interfaces had the opposite polarities. We investigated the sensitivities of these systems using the human IgG antigen-human IgG antibody receptor pair for main experiments, and drifts of antibody-functionalized gates without analytes as control experiments. Drifts without analyte can obscure the real sensitivity. We show that the D-OECT has the capability to cancel the drifts, and is also beneficial for showing the sensitivity more exactly. This configuration has the ability to increase the accuracy of antibody-antigen interaction detection, and further decrease or eliminate the effect of ions in the buffer solution. We also prove that the D-OECT can work well with different bioreceptor materials, which indicates that the system can be further applied to different conditions.

Ultrathin Covalent Organic Framework Nanosheets/Ti3C2Tx-Based Photoelectrochemical Biosensor for Efficient Detection of Prostate-Specific Antigen

Designable and ultrathin covalent organic framework nanosheets (CONs) with good photoelectric activity are promising candidates for the construction of photoelectrochemical (PEC) biosensors for the detection of low-abundance biological substrates. However, achieving highly sensitive PEC properties by using emerging covalent organic framework nanosheets (CONs) remains a great challenge due to the polymeric nature and poor photoelectric activity of CONs. Herein, we report for the first time the preparation of novel composites and their PEC sensing properties by electrostatic self-assembly of ultrathin CONs (called TTPA-CONs) with Ti₃C₂T_x. The prepared TTPA-CONs/Ti₃C₂T_x composites can be used as photocathodes for PEC detection of prostate-specific antigen (PSA) with high sensitivity, low detection limit, and good stability. This work not only expands the application of CONs but also opens new avenues for the development of efficient PEC sensing platforms.

A Novel, Quick, and Reliable Smartphone-Based Method for Serum PSA Quantification: Original Design of a Portable Microfluidic Immunosensor-Based System

Simple Summary

Prostate cancer (PCa) is the most frequently diagnosed malignancy and second most common cause of cancer-related death in males. An early diagnosis is crucial to improve the prognosis. Prostate-Specific Antigen (PSA) is the most widely used biomarker for PCa, but this type of biomarker analysis is performed in centralized laboratories, delaying the diagnosis and initiation of treatment. Our team has developed a miniaturized platform for portable PSA quantification to overcome this shortcoming. It includes a microfluidic chip, immune capture of PSA by magnetic microbeads, and electrochemical quantification. The utilization of a micro-potentiostat allows PSA levels to be read on a smartphone in less than 30 min. This technique was found to offer a fast, easy, specific, sensitive, and reproducible method for PSA quantification. Further research is warranted to verify these findings and explore its potential application at all health care levels.

Abstract

We describe a versatile, portable, and simple platform that includes a microfluidic electrochemical immunosensor for prostate-specific antigen (PSA) detection. It is based on the covalent immobilization of the anti-PSA monoclonal antibody on magnetic microbeads retained in the central channel of a microfluidic device. Image flow cytometry and scanning electron microscopy were used to characterize the magnetic microbeads. A direct sandwich immunoassay (with horseradish peroxidase-conjugated PSA antibody) served to quantify the cancer biomarker in serum samples. The enzymatic product was detected at −100 mV by amperometry on sputtered thin-film electrodes. Electrochemical reaction produced a current proportional to the PSA level, with a linear range from 10 pg mL⁻¹ to 1500 pg mL⁻¹. The sensitivity was demonstrated by a detection limit of 2 pg mL⁻¹ and the reproducibility by a coefficient of variation of 6.16%. The clinical performance of this platform was tested in serum samples from patients with prostate cancer (PCa), observing high specificity and full correlation with gold standard determinations. In conclusion, this analytical platform is a promising tool for measuring PSA levels in patients with PCa, offering a high sensitivity and reduced variability. The small platform size and low cost of this quantitative methodology support its suitability for the fast and sensitive analysis of PSA and other circulating biomarkers in patients. Further research is warranted to verify these findings and explore its potential application at all healthcare levels.

The synergistic effects of coupling Au nanoparticles with an alkynyl Co(II) phthalocyanine on the detection of prostate specific antigen

Prostate specific antigen (PSA) aptasensors are fabricated using a novel asymmetrically substituted Co phthalocyanine (CoPc), gold nanoparticles (AuNPs) and PSA-specific antigen. The fabricated aptasensors are: GCE-AuNPs-Aptamer, GCE@CoPc-Aptamer and GCE-AuNPs@CoPc-Aptamer (GCE = glassy carbon electrode). The fabricated sensors are characterized at each modification step to monitor the changes occurring at the sensor surface. Concentration studies were carried out using differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) to determine detection limits. All the fabricated aptasensors were found to be highly specific and selective but the GCE-AuNPs@CoPc-Aptamer nanoconjugate performed the best. The aptasensors were also tested in spiked serum samples and detection limits, as well as % recoveries were determined. The results obtained showed that the GCE-AuNPs@CoPc-Aptamer has the potential to be used for clinical studies as the results agree with those obtained for detection of PSA in buffer.

Transistor-Based Biomolecule Sensors: Recent Technological Advancements and Future Prospects

Transistor-based sensors have been widely recognized to be highly sensitive and reliable for point-of-care/bed-side diagnosis. In this line, a range of cutting-edge technologies has been generated to elevate the role of transistors for biomolecule detection. Detection of a wide range of clinical biomarkers has been reported using various configurations of transistors. The inordinate sensitivity of transistors to the field-effect imparts high sensitivity toward wide range of biomolecules. This overview has gleaned the present achievements with the technological advancements using high performance transistor-based sensors. This review encloses transistors incorporated with a variety of functional nanomaterials and organic elements for their excellence in selectivity and sensitivity. In addition, the technological advancements in fabrication of these microdevices or nanodevices and functionalization of the sensing elements have also been discussed. The technological gap in the realization of sensors in transistor platforms and the resulted scope for research has been discussed. Finally, foreseen technological advancements and future research perspectives are described.

Sensing Inflammation Biomarkers with Electrolyte-Gated Organic Electronic Transistors

An overview of cytokine biosensing is provided, with a focus on the opportunities provided by organic electronic platforms for monitoring these inflammation biomarkers which manifest at ultralow concentration levels in physiopathological conditions. Specifically, two of the field's state-of-the-art technologies-organic electrochemical transistors (OECTs) and electrolyte gated organic field effect transistors (EGOFETs)-and their use in sensing cytokines and other proteins associated with inflammation are a particular focus. The overview will include an introduction to current clinical and "gold standard" quantification techniques and their limitations in terms of cost, time, and required infrastructure. A critical review of recent progress with OECT- and EGOFET-based protein biosensors is presented, alongside a discussion onthe future of these technologies in the years and decades ahead. This is especially timely as the world grapples with limited healthcare diagnostics during the Coronavirus disease (COVID-19)pandemic where one of the worst-case scenarios for patients is the "cytokine storm." Clearly, low-cost point-of-care technologies provided by OECTs and EGOFETs can ease the global burden on healthcare systems and support professionals by providing unprecedented wealth of data that can help to monitor disease progression in real time.

Interfacing aptamers, nanoparticles and graphene in a hierarchical structure for highly selective detection of biomolecules in OECT devices

In several biomedical applications, the detection of biomarkers demands high sensitivity, selectivity and easy-to-use devices. Organic electrochemical transistors (OECTs) represent a promising class of devices combining a minimal invasiveness and good signal transduction. However, OECTs lack of intrinsic selectivity that should be implemented by specific approaches to make them well suitable for biomedical applications. Here, we report on a biosensor in which selectivity and a high sensitivity are achieved by interfacing, in an OECT architecture, a novel gate electrode based on aptamers, Au nanoparticles and graphene hierarchically organized to optimize the final response. The fabricated biosensor performs state of the art limit of detection monitoring biomolecules, such as thrombin-with a limit of detection in the picomolar range (≤ 5 pM) and a very good selectivity even in presence of supraphysiological concentrations of Bovine Serum Albumin (BSA-1mM). These accomplishments are the final result of the gate hierarchic structure that reduces sterich indrance that could contrast the recognition events and minimizes false positive, because of the low affinity of graphene towards the physiological environment. Since our approach can be easily applied to a large variety of different biomarkers, we envisage a relevant potential for a large series of different biomedical applications.

A facile strategy for quantitative sensing of glycans on cell surface using organic electrochemical transistors

This work designed a facile sensing strategy for quantitation of glycans on cell surface using organic electrochemical transistors (OECTs). The sensing strategy was performed by covalently binding target cells on mercaptopropionic acid modified gate electrode for the recognition of horseradish peroxidase (HRP) labeled lectins to specific glycans on cell surface, which led to sensitive channel current signal responding to the captured HRP and thus the expression of cell surface glycans. The quantitation of glycans on cell surface was achieved by using glycan modified microspheres to simulate the cells, on which the amounts of glycans were detected with enzyme linked immunosorbent assay. The proposed sensing strategy had been used for the detection of mannose and galactose on HeLa cells with Concanavalin A and peanut agglutinin as the specific lectins, which showed 1.37 × 10⁸ mannose and 1.13 × 10⁸ galactose on each cell, respectively. By treating HeLa cells with exoglycosidases, the mannose and galactose expression levels showed the same changes as those detected with flow cytometric analysis, indicating the practical application of the OECT-based biosensor in cell surface glycan expression analysis.

Layered Double Hydroxide-Modified Organic Electrochemical Transistor for Glucose and Lactate Biosensing

Biosensors based on Organic Electrochemical Transistors (OECTs) are developed for the selective detection of glucose and lactate. The transistor architecture provides signal amplification (gain) with respect to the simple amperometric response. The biosensors are based on a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) channel and the gate electrode is functionalised with glucose oxidase (GOx) or lactate oxidase (LOx) enzymes, which are immobilised within a Ni/Al Layered Double Hydroxide (LDH) through a one-step electrodeposition procedure. The here-designed OECT architecture allows minimising the required amount of enzyme during electrodeposition. The output signal of the biosensor is the drain current (I_d), which decreases as the analyte concentration increases. In the optimised conditions, the biosensor responds to glucose in the range of 0.1–8.0 mM with a limit of detection (LOD) of 0.02 mM. Two regimes of proportionality are observed. For concentrations lower than 1.0 mM, a linear response is obtained with a mean gain of 360, whereas for concentrations higher than 1.0 mM, I_d is proportional to the logarithm of glucose concentration, with a gain of 220. For lactate detection, the biosensor response is linear in the whole concentration range (0.05–8.0 mM). A LOD of 0.04 mM is reached, with a net gain equal to 400.

Virus Bioresistor (VBR) for Detection of Bladder Cancer Marker DJ-1 in Urine at 10 pM in One Minute

DJ-1, a 20.7 kDa protein, is overexpressed in people who have bladder cancer (BC). Its elevated concentration in urine allows it to serve as a marker for BC. However, no biosensor for the detection of DJ-1 has been demonstrated. Here, we describe a virus bioresistor (VBR) capable of detecting DJ-1 in urine at a concentration of 10 pM in 1 min. The VBR consists of a pair of millimeter-scale gold electrodes that measure the electrical impedance of an ultrathin (≈ 150-200 nm), two-layer polymeric channel. The top layer of this channel (90-105 nm in thickness) consists of an electrodeposited virus-PEDOT (PEDOT is poly(3,4-ethylenedioxythiophene)) composite containing embedded M13 virus particles that are engineered to recognize and bind to the target protein of interest, DJ-1. The bottom layer consists of spin-coated PEDOT-PSS (poly(styrenesulfonate)). Together, these two layers constitute a current divider. We demonstrate here that reducing the thickness of the bottom PEDOT-PSS layer increases its resistance and concentrates the resistance drop of the channel in the top virus-PEDOT layer, thereby increasing the sensitivity of the VBR and enabling the detection of DJ-1. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise (S/N > 100) and excellent sensor-to-sensor reproducibility characterized by coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a concentration of 30 pM, near the 10 pM limit of detection (LOD), encompassing four orders of magnitude in concentration.

Emerging Designs of Electronic Devices in Biomedicine

A long-standing goal of nanoelectronics is the development of integrated systems to be used in medicine as sensor, therapeutic, or theranostic devices. In this review, we examine the phenomena of transport and the interaction between electro-active charges and the material at the nanoscale. We then demonstrate how these mechanisms can be exploited to design and fabricate devices for applications in biomedicine and bioengineering. Specifically, we present and discuss electrochemical devices based on the interaction between ions and conductive polymers, such as organic electrochemical transistors (OFETs), electrolyte gated field-effect transistors (FETs), fin field-effect transistor (FinFETs), tunnelling field-effect transistors (TFETs), electrochemical lab-on-chips (LOCs). For these systems, we comment on their use in medicine.

A photoelectrochemical aptasensor based on p-n heterojunction CdS-Cu2O nanorod arrays with enhanced photocurrent for the detection of prostate-specific antigen

A sensitive photoelectrochemical (PEC) aptasensor was constructed for prostate-specific antigen (PSA) detection using an enhanced photocurrent response strategy. The p-n heterostructure CdS-Cu₂O nanorod arrays were prepared on Ti mesh (CdS-Cu₂O NAs/TM) by a simple hydrothermal method and successive ionic-layer adsorption reactions. Compared with the original CdS/TM, the synergistic effect of p-n type CdS-Cu₂O NAs/TM and the internal electric field realizes the effective separation of photoinduced electron-hole pairs and improves the PEC performance. In order to construct the aptasensor, an amino-modified aptamer was immobilized on CdS-Cu₂O NAs/TM to serve as a recognition unit for PSA. After the introduction of PSA, PSA was specifically captured by the aptamer on the PEC aptasensor, which can be oxidized by photogenerated holes to prevent electron-hole recombination and increase photocurrent. Under optimal conditions, the constructed PEC aptasensor has a linear range of 0.1-100 ng·mL^-1 and a detection limit as low as 0.026 ng·mL^-1. The results of aptasensor detection of human serum indicate that it has broad application prospects in biosensors and photoelectrochemical analysis.

Low-Voltage Organic Nonvolatile Memory Transistors with Water-Soluble Polymers Containing Thermally Induced Radical Dipoles

A water-soluble acidic polymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA), was applied as a gate-insulating layer for organic field-effect transistors (OFETs). Before depositing the poly(3-hexylthiophene) (P3HT) channel layers, the PAMPSA layers were subjected to thermal treatment at various temperatures from 140 to 230 °C. The OFET performance was greatly enhanced by thermal treatment between 140 and 170 °C, whereas it became very poor at higher temperatures (200-230 °C). In particular, the transfer curves showed pronounced hysteresis phenomena at 170 °C. Various measurements including thermogravimetric analysis and X-ray photoelectron spectroscopy disclosed that the PAMPSA chains underwent thermal degradation from ca. 160 °C and could generate carbon radicals leading to the formation of dipoles with the nitrogen lone pair electrons. The carbon-nitrogen dipoles delivered hysteresis phenomena to the OFETs with the PAMPSA layers treated at 170 °C, which exhibited excellent memory retention characteristics up to 10 000 cycles even at -1 V. Hence, it is expected that the thermally treated PAMPSA layers can be used as one of the viable gate-insulating memory materials for low-voltage transistor-type organic memory devices (TOMDs).

Amplification of aptamer sensor signals by four orders of magnitude via interdigitated organic electrochemical transistors

Electrochemical aptamer receptor/transducer systems are key elements of emerging E-AB sensors (aptasensor) used for the detection of various kinds of targets. However, the performance of these amperometric sensors is often limited by the low density of receptors attached to the sensor surface and high background signals. In the present work, interdigitated organic electrochemical transistors (iOECT) were used as a transducer to enhance the sensitivity and dynamic detection range of aptasensors. Therefore, the electrode of an amperometric sensor was utilized as gate electrode to operate the iOECT. This device was used to detect the low weight target molecule adenosine triphosphate (ATP), a common biomarker, which plays an important role for cardiovascular, neurodegenerative, and immune deficiency diseases. The novel aptasensor can selectively detect ATP with ultrahigh sensitivity down to the concentration of 10 pM, which is four orders of magnitude lower than the detection limit of the same aptasensor using an amperometric transducer principle (limit-of-detection of 106 nM) and most other previously reported electrochemical sensors. Furthermore, sensor regeneration was demonstrated, which facilitates reusability of OECT aptasensors. The small device size in combination with high transconductances paves the way for the development of highly sensitive integrated micro-biosensors for point-of-care applications.

An organic electrochemical transistor integrated with a molecularly selective isoporous membrane for amyloid-β detection

Alzheimer's disease (AD) is a progressive neurodegenerative disease associated with severe memory loss and impaired cognitive skills. A common pathological change found in AD-affected brains is the accumulation of a peptide named amyloid-β (Aβ) that can form plaques. Aβ aggregates are visible to structural scanning tools; however, these bulky and expensive instruments are accessible to trained personnel in clinical settings only, thus hampering timely diagnosis of the disease, particularly in low-resource settings. In this work, we design an organic electrochemical transistor (OECT) for in vitro detection of Aβ aggregates in human serum. The OECT channel is integrated with a nanostructured isoporous membrane which has a strong affinity for Aβ aggregates. The detection mechanism relies on the membrane capturing Aβ aggregates larger than the size of its pores and thus blocking the penetration of electrolyte ions into the channel underneath. Combining the high transconductance of the OECT with the precise porosity and selectivity of the membrane, the device detects the presence of Aβ aggregates in human serum samples with excellent sensitivity. This is the first-time demonstration of a biofunctionalized, nanostructured, and isoporous membrane integrated with a high-performance transistor for biosensing. This robust, low-power, non-invasive, and miniaturized sensor aids in the development of point-of-care tools for early diagnosis of AD.

A portable electrochemical immunosensor for highly sensitive point-of-care testing of genetically modified crops

The wide cultivation of genetically modified (GM) crops has raised concerns on the risks to humans and the environment. 5-enolpyruvylshikimate-3-phosphate synthase isolated from Agrobacterium species strain CP4 (CP4-EPSPS) protein is most widely present in these crops. Therefore the measurement of CP4-EPSPS sensitively in a point-of-care testing (POCT) manner for the screening of transgenic plants is demanded. To date the development of quantitative POCT system has not yet been reported. In presented study, an electrochemical immunosensor towards CP4-EPSPS has been fabricated by integrating a portable bioanalytical device with a disposable screen-printed carbon electrode (SPCE) for POCT of GM crops. The dual-functionalized AuNPs were used as nanoprobes and prepared by simultaneously tagging horseradish peroxidase (HRP) and antibody on AuNPs with an exceptionally simple protocol. The sensitivity of the developed nanoprobe-based immunosensor was 62.5-fold higher than that using HRP-labeled antibody. As a result, the proposed immunosensor using SPCE could detect CP4-EPSPS down to 0.050 ng mL^-1 with the linear range of 0.10-10 ng mL^-1 within 65 min. In addition, the developed method has been validated with genuine GM crops and the results show a good correlation coefficient of 0.9909 compared with those of a commercial ELISA kit. Therefore, this portable electrochemical immunosensor is suitable for rapid and sensitive detection and provides a convenient and reliable platform for POCT assay.

Biological Applications of Organic Electrochemical Transistors: Electrochemical Biosensors and Electrophysiology Recording

Organic electrochemical transistors (OECTs) are recently developed high-efficient transducers not only for electrochemical biosensor but also for cell electrophysiological recording due to the separation of gate electrode from the transistor device. The efficient integration of OECTs with electrochemical gate electrode makes the as-prepared sensors with improved performance, such as sensitivity, limit of detection, and selectivity. We herein reviewed the recent progress of OECTs-based biosensors and cell electrophysiology recording, mainly focusing on the principle and chemical design of gate electrode and the channel. First, the configuration, work principle, semiconductor of OECT are briefly introduced. Then different kinds of sensing modes are reviewed, especially for the biosensing and electrophysiological recording. Finally, the challenges and opportunities of this research field are discussed.

Conjugated Polymers for Assessing and Controlling Biological Functions

The field of organic bioelectronics is advancing rapidly in the development of materials and devices to precisely monitor and control biological signals. Electronics and biology can interact on multiple levels: organs, complex tissues, cells, cell membranes, proteins, and even small molecules. Compared to traditional electronic materials such as metals and inorganic semiconductors, conjugated polymers (CPs) have several key advantages for biological interactions: tunable physiochemical properties, adjustable form factors, and mixed conductivity (ionic and electronic). Herein, the use of CPs in five biologically oriented research topics, electrophysiology, tissue engineering, drug release, biosensing, and molecular bioelectronics, is discussed. In electrophysiology, implantable devices with CP coating or CP-only electrodes are showing improvements in signal performance and tissue interfaces. CP-based scaffolds supply highly favorable static or even dynamic interfaces for tissue engineering. CPs also enable delivery of drugs through a variety of mechanisms and form factors. For biosensing, CPs offer new possibilities to incorporate biological sensing elements in a conducting matrix. Molecular bioelectronics is today used to incorporate (opto)electronic functions in living tissue. Under each topic, the limits of the utility of CPs are discussed and, overall, the major challenges toward implementation of CPs and their devices to real-world applications are highlighted.

Organic Electrochemical Transistors/SERS-Active Hybrid Biosensors Featuring Gold Nanoparticles Immobilized on Thiol-Functionalized PEDOT Films

In this study we immobilized gold nanoparticles (AuNPs) onto thiol-functionalized poly(3,4-ethylenedioxythiophene) (PEDOT) films as bioelectronic interfaces (BEIs) to be integrated into organic electrochemical transistors (OECTs) for effective detection of dopamine (DA) and also as surface-enhanced Raman scattering (SERS)-active substrates for the selective detection of p-cresol (PC) in the presence of multiple interferers. This novel PEDOT-based BEI device platform combined (i) an underlying layer of polystyrenesulfonate-doped PEDOT (PEDOT:PSS), which greatly enhanced the transconductance and sensitivity of OECTs for electrochemical sensing of DA in the presence of other ascorbic acid and uric acid metabolites, as well as amperometric response toward DA with a detection limit (S/N = 3) of 37 nM in the linear range from 50 nM to 100 μM; with (ii) a top interfacial layer of AuNP-immobilized three-dimensional (3D) thiol-functionalized PEDOT, which not only improved the performance of OECTs for detecting DA, due to the signal amplification effect of the AuNPs with high catalytic activity, but also enabled downstream analysis (SERS detection) of PC on the same chip. We demonstrate that PEDOT-based 3D OECT devices decorated with a high-density of AuNPs can display new versatility for the design of next-generation biosensors for point-of-care diagnostics.

Claros System: A Rapid Microfluidics-Based Point-of-Care System for Quantitative Prostate Specific Antigen Analysis from Finger-Stick Blood

INTRODUCTION

Determination of circulating prostate specific antigen (PSA) is commonly used in the diagnosis and treatment monitoring of prostate cancer [1]. Presently, PSA testing is performed in centralized laboratories, which is associated with prolonged time between venipuncture and the PSA value being available. In this prospective study, we present a new and rapid test system for the quantitative determination of PSA levels from finger-stick blood.

METHODS

The Claros1^® analyzer is a rapid microfluidics-based point-of-care system for quantitative PSA analysis from 10-µl finger-stick blood that requires only 10 min for testing. Total PSA concentrations by the Claros system in 100 consecutive asymptomatic men (median age 57 years, range 44-81 years) were compared with two commercially available, commonly used PSA assays (Abbott and Elecsys by Roche) performed by a reference laboratory.

RESULTS

Eighty-six percent of finger-stick blood-borne probes from 100 men were evaluable for PSA testing by the Claros1^® analyzer system. In 13/14 cases the expiry date of the microfluid cassettes of the Claros system was exceeded and one blood puncture was performed inadequately. The correlations between the Claros results and OPKO-Abbott and OPKO-Roche assay results were high, with R² values of 0.982 and 0.985, respectively. The R² value for the Roche-Abbott correlation was 0.991 with a slope value of 1.160. Prostate cancer was diagnosed in seven cases, with a median PSA of 1.8 ng/ml in the Claros group compared to 1.75 ng/ml and 2.1 ng/ml in the Abbott and Roche groups, respectively.

CONCLUSION

The Claros1^® PSA assay combines the advantages of rapid, accurate detection with a low required sample volume, allowing the analysis to be performed using finger-stick blood. Provided that further analysis proves the reproducibility of the test, it may help to reduce the number of office visits, thus decreasing costs to the health care system.

Functionalized Organic Thin Film Transistors for Biosensing

The rise of organic bioelectronics efficiently bridges the gap between semiconductor devices and biological systems, leading to flexible, lightweight, and low-cost organic bioelectronic devices suitable for health or body signal monitoring. The introduction of organic semiconductors in the devices can soften the boundaries between microelectronic systems and dynamically active cells and tissues. Therefore, organic bioelectronics has attracted much attention recently due to the unique properties and promising applications. Organic thin film transistors (OTFTs), owing to their inherent capability of amplifying received signals, have emerged as one of the state-of-the-art biosensing platforms. The advantages of organic semiconductors in terms of synthetic freedom, low temperature solution processing, biocompatibility, and mechanical flexibility render OTFTs ideal transducers for wearable electronics, e-skin, and implantable devices. How to realize highly sensitive, selective, rapid, and efficient signal capture and extraction of biological recognition events is the major challenge in the design of biosensors. OTFTs are prone to converting the presence or change of target analytes into specific electrical signals even in complex biological systems. More importantly, OTFT sensors can be conveniently functionalized with chemical or biological modifications and exhibit substantially improved device sensitivity and selectivity as well as other analytical figure of merits, including calibration range, linearity, and accuracy. However, the stability and reproducibility of the organic devices need to be further improved. In this Account, we first introduce the unique features of OTFTs for bioelectronic applications. Two typical OTFT configurations, including organic electrochemical transistor (OECT) and electrolyte gated organic field effect transistor (EGOFET), are highlighted in their sensing applications mainly due to the operation of the devices in electrolytes and the combination of ionic and electronic charge transports in the devices. These devices are potentiometric transducers with low working voltages (<1 V) and high sensitivity, and are thus suitable for wearable applications with low power consumption. Second, the functionalization strategies on channel materials, electrolytes, and gate electrodes based on various modification methods and sensing mechanisms are discussed in sequence. In an OECT- or EGOFET-based biosensor, the device performance is particularly sensitive to the physical properties of the two interfaces, including channel/electrolyte and gate/electrolyte interfaces. Any change in the potential drop or capacitance of either interface can influence the channel current substantially. Therefore, the functionalization of the interfaces is critical to the sensing performance. In particular, when an electrochemically active material is modified on the interfaces, the reaction of the analyte catalyzed by the modified material can influence the interface potential and lead to a channel current response much stronger than that of a conventional electrochemical measurement. So the biosensors are much more sensitive than typical analytical methods due to the signal amplification of the transistors. Third, the processing techniques including screen printing and inkjet printing and the possibility for mass production are discussed. The applications of organic transistors in wearable electronics and healthcare monitoring systems, especially the fabric OECT-based biosensors for noninvasive detection, are presented. It is expected that the versatile organic transistors will enable various compact, flexible and disposable biosensors compatible with wearable electronics.

Functional Sensing Interfaces of PEDOT:PSS Organic Electrochemical Transistors for Chemical and Biological Sensors: A Mini Review

Organic electrochemical transistors (OECTs) are promising devices for applications in in vitro and in vivo measurements. OECTs have two important sensing interfaces for signal monitoring: One is the gate electrode surface; the other is the channel surface. This mini review introduced the new developments in chemical and biological detection of the two sensing interfaces. Specific focus was given on the modification technological approaches of the gate or channel surface. In particular, some unique strategies and surface designs aiming to facilitate signal-transduction and amplification were discussed. Several perspectives and current challenges of OECTs development were also briefly summarized.

An acid-responsive all-in-one signal amplification strategy for the ultrasensitive prostate-specific antigen detection

A one-pot strategy for the preparation of all-in-one signal tags for the colorimetric immunoassay of prostate-specific antigen.

Use of data processing for rapid detection of the prostate-specific antigen biomarker using immunomagnetic sandwich-type sensors

Diagnosis of cancer using electroanalytical methods can be achieved at low cost and in rapid assays, but this may require the combination with data treatment for determining biomarkers in real samples. In this paper, we report an immunomagnetic nanoparticle-based microfluidic sensor (INμ-SPCE) for the amperometric detection of the prostate-specific antigen (PSA) biomarker, the data of which were treated with information visualization methods. The INμ-SPCE consists of eight working electrodes, reference and counter electrodes. On the working electrodes, magnetic nanoparticles with secondary antibodies with the enzyme horseradish peroxidase were immobilized for the indirect detection of PSA in a sandwich-type procedure. Under optimal conditions, the immunosensor could operate within a wide range from 12.5 to 1111 fg·L^-1, with a low detection limit of 0.062 fg·L^-1. Multidimensional projections combined with feature selection allowed for the distinction of cell lysates with different levels of PSA, in agreement with results from the traditional enzyme-linked immunosorbent assay. The approaches for immunoassays and data processing are generic, and therefore the strategies described here may provide a simple platform for clinical diagnosis of cancers and other types of diseases.

PEDOT:PSS Morphostructure and Ion-To-Electron Transduction and Amplification Mechanisms in Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) represent a powerful and versatile type of organic-based device, widely used in biosensing and bioelectronics due to potential advantages in terms of cost, sensitivity, and system integration. The benchmark organic semiconductor they are based on is poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), the electrical properties of which are reported to be strongly dependent on film morphology and structure. In particular, the literature demonstrates that film processing induces morphostructural changes in terms of conformational rearrangements in the PEDOT:PSS in-plane phase segregation and out-of-plane vertical separation between adjacent PEDOT-rich domains. Here, taking into account these indications, we show the thickness-dependent operation of OECTs, contextualizing it in terms of the role played by PEDOT:PSS film thickness in promoting film microstructure tuning upon controlled-atmosphere long-lasting thermal annealing (LTA). To do this, we compared the LTA-OECT response to that of OECTs with comparable channel thicknesses that were exposed to a rapid thermal annealing (RTA). We show that the LTA process on thicker films provided OECTs with an enhanced amplification capability. Conversely, on lower thicknesses, the LTA process induced a higher charge carrier modulation when the device was operated in sensing mode. The provided experimental characterization also shows how to optimize the OECT response by combining the control of the microstructure via solution processing and the effect of postdeposition processing.

Advanced electronic skin devices for healthcare applications

Electronic skin, a kind of flexible electronic device and system inspired by human skin, has emerged as a promising candidate for wearable personal healthcare applications. Wearable electronic devices with skin-like properties will provide platforms for continuous and real-time monitoring of human physiological signals such as tissue pressure, body motion, temperature, metabolites, electrolyte balance, and disease-related biomarkers. Transdermal drug delivery devices can also be integrated into electronic skin to enhance its non-invasive, real-time dynamic therapy functions. This review summarizes the recent progress in electronic skin devices for applications in human health monitoring and therapy systems as well as several potential mass production technologies such as inkjet printing and 3D printing. The opportunities and challenges in broadening the applications of electronic skin devices in practical healthcare are also discussed.

Wearable Sensor System for Detection of Lactate in Sweat

Increased development of wearable sensors for physiological monitoring has spurred complementary interest in the detection of biochemical indicators of health and performance. We report a wearable sensor system for non-invasive detection of excreted human biomarkers in sweat. The system consists of a thin, flexible, kapton patch (2.5 × 7.5 cm) that can be coated with adhesive and affixed to the skin. The system can be controlled by a cell phone via a near-field communications protocol, charged wirelessly, and the data can be downloaded and displayed in a smart phone app. The system is designed such that the sensing element plugs into a low-profile socket, and can easily be removed and replaced as needed due to saturation or aging effects. As a demonstration case, we examined using an organic electrochemical transistor (OECT) within this system to monitor lactate concentration. Several different methods for optimizing the sensor performance were compared, including altering electrode materials, employing various immobilization techniques, and tailoring operating voltages. Resulting functional response of the lactate oxidase enzyme was compared as a function of the sensor variables. The OECT sensor was shown to have high sensitivity to lactate, however the sensing range is limited to lactate concentrations below approximately 1 mM.

Organic Photo-Electrochemical Transistor-Based Biosensor: A Proof-of-Concept Study toward Highly Sensitive DNA Detection

Organic bioelectronics have shown promising applications for various sensing purposes due to their significant advantages in term of high flexibility, portability, easy fabrication, and biocompatibility. Here, a new type of organic device, organic photo-electrochemical transistor (OPECT), is reported, which is the combination of an organic electrochemical transistor and a photo-electrochemical gate electrode modified with CdS quantum dots (QDs). Thanks to the inherent amplification function of the transistor, the OPECT-based biosensor exhibits much higher sensitivity than that of a traditional biosensor. The sensing mechanism of the OPECT is attributed to the charge transfer between the photosensitive semiconductor CdS QDs and the gate electrode. In an OPECT-based DNA sensor, target DNA is labeled with Au nanoparticles (NPs) and captured on the gate electrode, which can influence the charge transfer on the gate caused by the exciton-plasmon interactions between CdS QDs and Au NPs. Consequently, a highly sensitive and selective DNA sensor with a detection limit of around 1 × 10^-15 m is realized. It is expected that OPECTs can be developed as a high-performance platform for numerous biological detections in the future.

Label-Free Electrochemical Immunosensor Based on Ionic Liquid Containing Dialdehyde As a Novel Linking Agent for the Antibody Immobilization

Demand for label-free electrochemical immunosensor has resulted in extensive research in improving the conductivity of a sensing interface and antibody immobilization. In this paper, an electrochemical immunosensor for prostate specific antigen based on dialdehyde-functionalized ionic liquid used as a novel linking reagent to replace glutaraldehyde for the antibody immobilization is described. The novel linking reagent enhanced the conductivity of the sensing interface. Thus, the proposed immunosensor had a wider linear range of 0.05-30 ng mL^-1, with a lower detection limit of 0.04 ng mL^-1 compared with the immunosensor based on glutaraldehyde for the antibody immobilization.

Organic Electrochemical Transistors for the Detection of Cell Surface Glycans

Cell surface glycans play critical roles in diverse biological processes, such as cell-cell communication, immunity, infection, development, and differentiation. Their expressions are closely related to cancer growth and metastasis. This work demonstrates an organic electrochemical transistor (OECT)-based biosensor for the detection of glycan expression on living cancer cells. Herein, mannose on human breast cancer cells (MCF-7) as the target glycan model, poly dimethyl diallyl ammonium chloride-multiwall carbon nanotubes (PDDA-MWCNTs) as the loading interface, concanavalin A (Con A) with active mannose binding sites, aptamer and horseradish peroxidase co-immobilized gold nanoparticles (HRP-aptamer-Au NPs) as specific nanoprobes are used to fabricate the OECT biosensor. In this strategy, PDDA-MWCNT interfaces can enhance the loading of Con A, and the target cells can be captured through Con A via active mannose binding sites. Thus, the expression of cell surface can be reflected by the amount of cells captured on the gate. Specific nanoprobes are introduced to the captured cells to produce an OECT signal because of the reduction of hydrogen peroxide catalyzed by HRP conjugated on Au nanoparticles, while the aptamer on nanoprobes can selectively recognize the MCF-7 cells. It is reasonable that more target cells are captured on the gate electrode, more HRP-nanoprobes are loaded thus a larger signal response. The device shows an obvious response to MCF-7 cells down to 10 cells/μL and can be used to selectively monitor the change of mannose expression on cell surfaces upon a treatment with the N-glycan inhibitor. The OECT-based biosensor is promising for the analysis of glycan expressions on the surfaces of different types of cells.

In Situ Pt Staining Method for Simple, Stable, and Sensitive Pressure-Based Bioassays

Pressure-based bioassays (PASS) integrate a molecular recognition process with a catalyzed gas generation reaction, enabling sensitive and portable quantitation of biomarkers in clinical samples. Using platinum nanoparticles (PtNPs) as a catalyst has significantly improved the sensitivity of PASS compared with protein enzyme-based detection. However, PtNPs are easily deactivated during storage or after being decorated with antibodies. Moreover, nonspecific adsorption of PtNPs on substrates has been a problem, resulting in significant backgrounds. To solve these problems of PtNP-based detection, we report a robust, simple, stable, and sensitive Pt staining method for PASS. Detection antibody-decorated gold nanoparticles (AuNPs) are used to perform enzyme-linked immunosorbent assay, followed by Pt staining to stain AuNPs with Ag and Pt bimetallic shells (Au@AgPtNPs), which endow AuNPs with catalytic activity. The concentration of targets can be quantitatively determined by measuring the pressure due to O₂ gas (g) formed by the decomposition of H₂O₂ catalyzed by Au@AgPtNPs. C-reactive protein and avian influenza hemagglutinin 5 neuraminidase 1 can be quantitatively detected with detection limits of 0.015 and 0.065 ng/mL, respectively. The simple, stable, and sensitive properties of the Pt staining-based method will largely broaden the applications of PASS in clinical diagnosis and biomedicine.

Integration of organic electrochemical transistors and immuno-affinity membranes for label-free detection of interleukin-6 in the physiological concentration range through antibody–antigen recognition

A label-free immunosensor based on an organic electrochemical transistor integrated with an immuno-affinity membrane for cytokine detection at physiologically relevant concentrations is reported.