Electrochemistry-based approaches to low cost, high sensitivity, automated, multiplexed protein immunoassays for cancer diagnostics

Promising predictive molecular biomarkers for cervical cancer (Review)

Cervical cancer (CC) constitutes a serious public health problem. Vaccination and screening programs have notably reduced the incidence of CC worldwide by >80%; however, the mortality rate in low‑income countries remains high. The staging of CC is a determining factor in therapeutic strategies: The clinical management of early stages of CC includes surgery and/or radiotherapy, whereas radiotherapy and/or concurrent chemotherapy are the recommended therapeutic strategies for locally advanced CC. The histopathological characteristics of tumors can effectively serve as prognostic markers of radiotherapy response; however, the efficacy rate of radiotherapy may significantly differ among cancer patients. Failure of radiotherapy is commonly associated with a higher risk of recurrence, persistence and metastasis; therefore, radioresistance remains the most important and unresolved clinical problem. This condition highlights the importance of precision medicine in searching for possible predictive biomarkers to timely identify patients at risk of treatment response failure and provide tailored therapeutic strategies according to genetic and epigenetic characteristics. The present review aimed to summarize the evidence that supports the role of several proteins, methylation markers and non‑coding RNAs as potential predictive biomarkers for CC.

Design and Fabrication of a 3D-Printed Microfluidic Immunoarray for Ultrasensitive Multiplexed Protein Detection

Microfluidic technology has revolutionized device fabrication by merging principles of fluid dynamics with technologies from chemistry, physics, biology, material science, and microelectronics. Microfluidic systems manipulate small volumes of fluids to perform automated tasks with applications ranging from chemical syntheses to biomedical diagnostics. The advent of low-cost 3D printers has revolutionized the development of microfluidic systems. For measuring molecules, 3D printing offers cost-effective, time, and ease-of-designing benefits. In this paper, we present a comprehensive tutorial for design, optimization, and validation for creating a 3D-printed microfluidic immunoarray for ultrasensitive detection of multiple protein biomarkers. The target is the development of a point of care array to determine five protein biomarkers for aggressive cancers. The design phase involves defining dimensions of microchannels, reagent chambers, detection wells, and optimizing parameters and detection methods. In this study, the physical design of the array underwent multiple iterations to optimize key features, such as developing open detection wells for uniform signal distribution and a flap for covering wells during the assay. Then, full signal optimization for sensitivity and limit of detection (LOD) was performed, and calibration plots were generated to assess linear dynamic ranges and LODs. Varying characteristics among biomarkers highlighted the need for tailored assay conditions. Spike-recovery studies confirmed the assay's accuracy. Overall, this paper showcases the methodology, rigor, and innovation involved in designing a 3D-printed microfluidic immunoarray. Optimized parameters, calibration equations, and sensitivity and accuracy data contribute valuable metrics for future applications in biomarker analyses.

Advancements in Oncoproteomics Technologies: Treading toward Translation into Clinical Practice

Proteomics continues to forge significant strides in the discovery of essential biological processes, uncovering valuable information on the identity, global protein abundance, protein modifications, proteoform levels, and signal transduction pathways. Cancer is a complicated and heterogeneous disease, and the onset and progression involve multiple dysregulated proteoforms and their downstream signaling pathways. These are modulated by various factors such as molecular, genetic, tissue, cellular, ethnic/racial, socioeconomic status, environmental, and demographic differences that vary with time. The knowledge of cancer has improved the treatment and clinical management; however, the survival rates have not increased significantly, and cancer remains a major cause of mortality. Oncoproteomics studies help to develop and validate proteomics technologies for routine application in clinical laboratories for (1) diagnostic and prognostic categorization of cancer, (2) real-time monitoring of treatment, (3) assessing drug efficacy and toxicity, (4) therapeutic modulations based on the changes with prognosis and drug resistance, and (5) personalized medication. Investigation of tumor-specific proteomic profiles in conjunction with healthy controls provides crucial information in mechanistic studies on tumorigenesis, metastasis, and drug resistance. This review provides an overview of proteomics technologies that assist the discovery of novel drug targets, biomarkers for early detection, surveillance, prognosis, drug monitoring, and tailoring therapy to the cancer patient. The information gained from such technologies has drastically improved cancer research. We further provide exemplars from recent oncoproteomics applications in the discovery of biomarkers in various cancers, drug discovery, and clinical treatment. Overall, the future of oncoproteomics holds enormous potential for translating technologies from the bench to the bedside.

Clinical Efficacy of Endoscopic Infratentorial Supracerebellar Approach for Pineal Region Tumors: A Retrospective Case-Control Study

Tumors in the pineal region are deep, with complex surrounding anatomy, adjacent to important blood vessels and nerve structures, and surgical resection is difficult and risky. In this paper, we reviewed the literature to understand the epidemiology and clinical manifestations of pineal region tumors in the country and study the clinical indications, related problems, and successful experiences of patients with pineal region tumors treated by the transtentorial-superior approach. The clinical data of 80 patients with pineal region tumors were selected as the retrospective research objects and divided into the control group and the treatment group, with 40 cases in each group, according to the random number table method. The control group was treated using the endoscopic transtentorial approach (Poppen approach), while the treatment group was treated with the endoscopic supratentorial approach (Krause approach). The inflammatory factors, inflammatory stress response, postoperative neurological dysfunction, clinical efficacy, and poor prognosis were observed and compared between the two groups. Tumor resection and recurrence were used to compare the clinical outcomes of tumors in the pineal region. The extent of surgical resection was 100% higher in both groups, and the treatment group was comparable to the control group. The prognosis of patients after the operation was poor. Nausea and vomiting, visual disturbance, upper vision paralysis, and ataxia in the treatment group were significantly lower than those in the control group, with no statistical significance (P > 0.05). At the same time, the bone window can be reduced to reduce trauma and provide a certain reference for patients to choose a safe and complete resection method.

Use of MS-GUIDE for identification of protein biomarkers for risk stratification of patients with prostate cancer

Background

Non-invasive liquid biopsies could complement current pathological nomograms for risk stratification of prostate cancer patients. Development and testing of potential liquid biopsy markers is time, resource, and cost-intensive. For most protein targets, no antibodies or ELISAs for efficient clinical cohort pre-evaluation are currently available. We reasoned that mass spectrometry-based prescreening would enable the cost-effective and rational preselection of candidates for subsequent clinical-grade ELISA development.

Methods

Using Mass Spectrometry-GUided Immunoassay DEvelopment (MS-GUIDE), we screened 48 literature-derived biomarker candidates for their potential utility in risk stratification scoring of prostate cancer patients. Parallel reaction monitoring was used to evaluate these 48 potential protein markers in a highly multiplexed fashion in a medium-sized patient cohort of 78 patients with ground-truth prostatectomy and clinical follow-up information. Clinical-grade ELISAs were then developed for two of these candidate proteins and used for significance testing in a larger, independent patient cohort of 263 patients.

Results

Machine learning-based analysis of the parallel reaction monitoring data of the liquid biopsies prequalified fibronectin and vitronectin as candidate biomarkers. We evaluated their predictive value for prostate cancer biochemical recurrence scoring in an independent validation cohort of 263 prostate cancer patients using clinical-grade ELISAs. The results of our prostate cancer risk stratification test were statistically significantly 10% better than results of the current gold standards PSA alone, PSA plus prostatectomy biopsy Gleason score, or the National Comprehensive Cancer Network score in prediction of recurrence.

Conclusion

Using MS-GUIDE we identified fibronectin and vitronectin as candidate biomarkers for prostate cancer risk stratification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12014-022-09349-x.

Towards principled design of cancer nanomedicine to accelerate clinical translation

Nanotechnology in medical applications, especially in oncology as drug delivery systems, has recently shown promising results. However, although these advances have been promising in the pre-clinical stages, the clinical translation of this technology is challenging. To create drug delivery systems with increased treatment efficacy for clinical translation, the physicochemical characteristics of nanoparticles such as size, shape, elasticity (flexibility/rigidity), surface chemistry, and surface charge can be specified to optimize efficiency for a given application. Consequently, interdisciplinary researchers have focused on producing biocompatible materials, production technologies, or new formulations for efficient loading, and high stability. The effects of design parameters can be studied in vitro, in vivo, or using computational models, with the goal of understanding how they affect nanoparticle biophysics and their interactions with cells. The present review summarizes the advances and technologies in the production and design of cancer nanomedicines to achieve clinical translation and commercialization. We also highlight existing challenges and opportunities in the field.

Nucleases as molecular targets for cancer diagnosis

Early cancer diagnosis is a crucial element to improved treatment options and survival. Great research efforts have been made in the search for better performing cancer diagnostic biomarkers. However, the quest continues as novel biomarkers with high accuracy for an early diagnosis remain an unmet clinical need. Nucleases, which are enzymes capable of cleaving nucleic acids, have been long considered as potential cancer biomarkers. The implications of nucleases are key for biological functions, their presence in different cellular counterparts and catalytic activity led the enthusiasm towards investigating the role of nucleases as promising cancer biomarkers. However, the most essential feature of these proteins, which is their enzymatic activity, has not been fully exploited. This review discusses nucleases interrogated as cancer biomarkers, providing a glimpse of their physiological roles. Moreover, it highlights the potential of harnessing the enzymatic activity of cancer-associated nucleases as a novel diagnostic biomarker using nucleic acid probes as substrates.

Emerging on-chip electrokinetic based technologies for purification of circulating cancer biomarkers towards liquid biopsy: A review

Early detection of cancer can significantly reduce mortality and save lives. However, the current cancer diagnosis is highly dependent on costly, complex, and invasive procedures. Thus, a great deal of effort has been devoted to exploring new technologies based on liquid biopsy. Since liquid biopsy relies on detection of circulating biomarkers from biofluids, it is critical to isolate highly purified cancer-related biomarkers, including circulating tumor cells (CTCs), cell-free nucleic acids (cell-free DNA and cell-free RNA), small extracellular vesicles (exosomes), and proteins. The current clinical purification techniques are facing a number of drawbacks including low purity, long processing time, high cost, and difficulties in standardization. Here, we review a promising solution, on-chip electrokinetic-based methods, that have the advantage of small sample volume requirement, minimal damage to the biomarkers, rapid, and label-free criteria. We have also discussed the existing challenges of current on-chip electrokinetic technologies and suggested potential solutions that may be worthy of future studies.

Detecting cancer metastasis and accompanying protein biomarkers at single cell levels using a 3D-printed microfluidic immunoarray

A low-cost microfluidic microarray capable of lysing cells and quantifying proteins released after lysis was designed and 3D-printed. The array lyses cells on-chip in lysis buffer augmented with a 2s pulse of a sonic cell disruptor. Detection of desmoglein 3 (DSG3), a metastatic biomarker for head and neck squamous cell carcinoma (HNSCC), along with two accompanying HNSCC biomarkers from a single cell lysate of oral cancer cell cultures was demonstrated. A lysis chamber and reagent compartments deliver sample and reagents into detection chambers decorated with capture antibodies immobilized onto inner walls coated with a highly swollen 3D chitosan hydrogel film. Sandwich immunoassays are achieved when captured analytes labeled with biotinylated secondary antibodies, which then capture streptavidin-poly [horse radish peroxidase] (Poly-HRP). Subsequent delivery of super-bright femto-luminol with H2O2 generates chemiluminescence captured with a CCD camera. DSG3 is membrane-bound protein in HNSCC cells of invaded lymph nodes, vascular endothelial growth factor-A (VEGF-A), vascular endothelial growth factor-C (VEGF-C) were positive controls overexpressed into the HNSCC culture medium. Beta-tubulin (β-Tub) was used as a loading control to estimate the number of cells in analyzed samples. Limits of detection (LOD) were 0.10 fg/mL for DSG3, and 0.20 fg/mL for VEGF-A, VEGF-C and β-Tub. Three orders of magnitude semilogarithmic dynamic ranges were achieved. VEGF-A showed high in-cell expression, but VEGF-C had low levels inside cells. The very low LODs enabled quantifying these proteins released from single cells. Strong correlation between results from on-chip cell lysis, conventional off-line lysis and ELISA confirmed accuracy.

Multiplexed Protein Biomarker Detection with Microfluidic Electrochemical Immunoarrays

Electrochemistry is a multidisciplinary field encompassing the study of analytes in solution for detection and quantification. For the medical field, this brings opportunities to the clinical practice of disease detection through measurements of disease biomarkers. Specifically, panels of biomarkers offer an important future option that can enable physicians' access to blood, saliva, or urine bioassays for screening diseases, as well as monitoring the progression and response to therapy. Here, we describe the simultaneous detection of eight protein cancer biomarkers in a 30-min assay by a microfluidic electrochemical immunoarray.

Analysis of urinary VOCs using mass spectrometric methods to diagnose cancer: A review

The development of non-invasive screening techniques for early cancer detection is one of the greatest scientific challenges of the 21st century. One promising emerging method is the analysis of volatile organic compounds (VOCs). VOCs are low molecular weight substances generated as final products of cellular metabolism and emitted through a variety of biological matrices, such as breath, blood, saliva and urine. Urine stands out for its non-invasive nature, availability in large volumes, and the high concentration of VOCs in the kidneys. This review provides an overview of the available data on urinary VOCs that have been investigated in cancer-focused clinical studies using mass spectrometric (MS) techniques. A literature search was conducted in ScienceDirect, Pubmed and Web of Science, using the keywords "Urinary VOCs", "VOCs biomarkers" and "Volatile cancer biomarkers" in combination with the term "Mass spectrometry". Only studies in English published between January 2011 and May 2020 were selected. The three most evaluated types of cancers in the reviewed studies were lung, breast and prostate, and the most frequently identified urinary VOC biomarkers were hexanal, dimethyl disulfide and phenol; with the latter seeming to be closely related to breast cancer. Additionally, the challenges of analyzing urinary VOCs using MS-based techniques and translation to clinical utility are discussed. The outcome of this review may provide valuable information to future studies regarding cancer urinary VOCs.

Printed Electrodes in Microfluidic Arrays for Cancer Biomarker Protein Detection

Medical diagnostics is trending towards a more personalized future approach in which multiple tests can be digitized into patient records. In cancer diagnostics, patients can be tested for individual protein and genomic biomarkers that detect cancers at very early stages and also be used to monitor cancer progression or remission during therapy. These data can then be incorporated into patient records that could be easily accessed on a cell phone by a health care professional or the patients themselves on demand. Data on protein biomarkers have a large potential to be measured in point-of-care devices, particularly diagnostic panels that could provide a continually updated, personalized record of a disease like cancer. Electrochemical immunoassays have been popular among protein detection methods due to their inherent high sensitivity and ease of coupling with screen-printed and inkjet-printed electrodes. Integrated chips featuring these kinds of electrodes can be built at low cost and designed for ease of automation. Enzyme-linked immunosorbent assay (ELISA) features are adopted in most of these ultrasensitive detection systems, with microfluidics allowing easy manipulation and good fluid dynamics to deliver reagents and detect the desired proteins. Several of these ultrasensitive systems have detected biomarker panels ranging from four to eight proteins, which in many cases when a specific cancer is suspected may be sufficient. However, a grand challenge lies in engineering microfluidic-printed electrode devices for the simultaneous detection of larger protein panels (e.g., 50-100) that could be used to test for many types of cancers, as well as other diseases for truly personalized care.

3D-Printed Immunosensor Arrays for Cancer Diagnostics

Detecting cancer at an early stage of disease progression promises better treatment outcomes and longer lifespans for cancer survivors. Research has been directed towards the development of accessible and highly sensitive cancer diagnostic tools, many of which rely on protein biomarkers and biomarker panels which are overexpressed in body fluids and associated with different types of cancer. Protein biomarker detection for point-of-care (POC) use requires the development of sensitive, noninvasive liquid biopsy cancer diagnostics that overcome the limitations and low sensitivities associated with current dependence upon imaging and invasive biopsies. Among many endeavors to produce user-friendly, semi-automated, and sensitive protein biomarker sensors, 3D printing is rapidly becoming an important contemporary tool for achieving these goals. Supported by the widely available selection of affordable desktop 3D printers and diverse printing options, 3D printing is becoming a standard tool for developing low-cost immunosensors that can also be used to make final commercial products. In the last few years, 3D printing platforms have been used to produce complex sensor devices with high resolution, tailored towards researchers’ and clinicians’ needs and limited only by their imagination. Unlike traditional subtractive manufacturing, 3D printing, also known as additive manufacturing, has drastically reduced the time of sensor and sensor array development while offering excellent sensitivity at a fraction of the cost of conventional technologies such as photolithography. In this review, we offer a comprehensive description of 3D printing techniques commonly used to develop immunosensors, arrays, and microfluidic arrays. In addition, recent applications utilizing 3D printing in immunosensors integrated with different signal transduction strategies are described. These applications include electrochemical, chemiluminescent (CL), and electrochemiluminescent (ECL) 3D-printed immunosensors. Finally, we discuss current challenges and limitations associated with available 3D printing technology and future directions of this field.

OMICS insights into cancer histology; Metabolomics and proteomics approach

Metabolomics as a post-genomic research area comprising different analytical methods for small molecules analysis. One of the underlying applications of metabolomics technology for better disease diagnosis and prognosis is discovering the metabolic pathway differences between healthy individuals and patients. On the other hand, the other noteworthy applications of metabolomics include its effective role in biomarker screening for cancer detection, monitoring, and prediction. In other words, emerging of the metabolomics field can be hopeful to provide a suitable alternative for the common current cancer diagnostic methods especially histopathological tests. Indeed, cancer as a major global issue places a substantial burden on the health care system. Hence, proper management can be beneficial. In this respect, formalin-fixed paraffin-embedded tissue specimens (in histopathological tests) are considered as a valuable source for metabolomics investigations. Interestingly, formalin-fixed paraffin-embedded tissue specimens can provide informative data for cancer management. In general, using these specimens, determining the cancer stage, individual response to the different therapies, personalized risk prediction are possible and high-quality clinical services are the promise of OMICS technologies for cancer disease. However, considering all of these beneficial characteristics, there are still some limitations in this area that need to be addressed in order to optimize the metabolomics utilizations and advancement.

Molecularly imprinted polyaniline for detection of horseradish peroxidase

A new facile and fast approach to the synthesis of polyaniline (PANi) molecularly imprinted polymers (MIPs) based on aniline oxidative chemical polymerization was proposed for protein recognition. For the first time, a surface imprinting strategy was implemented for the synthesis of PANi MIPs on the inner surface of soft glass polycapillaries (PC) with a large (2237) number of individual microcapillaries. Two different PANi layers-(i) PANi film and (ii) protein imprinted PANi nanowires-were synthesized sequentially. Uniform and highly stable PANi film was synthesized by oxidative polymerization at pH< 1. The synthesis of PANi MIPs on the PANi film pre-coated surface improved the reproducibility of PANi MIP formation. PANi MIP nanowires were synthesized at "mild" conditions (pH > 4.5) to preserve the protein template activity. The binding of horseradish peroxidase (HRP) molecules on the PANi MIP selective sites was confirmed by photometry (TMB chromogenic reaction), SEM images, and FTIR spectroscopy. The developed PANi MIPs enable HRP determination with a limit of detection (LOD) as low as 1.00 and 0.07 ng mL^-1 on the glass slips and PC, respectively. The PANi MIPs are characterized by high stability; they are reversible and selective to HRP. The proposed approach allows PANi MIPs to be obtained for proteins on different supports and to create new materials for separation and sensing. Graphical abstract.

Two-photon imaging of aptamer-functionalized Copolymer/TPdye fluorescent organic dots targeted to cancer cells

Fluorescent organic dots (O-dots) recently have emerged as a new class of promising contrast reagents for two-photon fluorescence (TPF) imaging. However, most of these developed two-photon absorption (TPA) O-dots have no tumor-targeting group, which hampers their wide application for targeted tumor imaging. Herein, we fabricated Sgc8c aptamer-mediated TPA O-dots as a proof-of-concept of the sensing platform for targeted imaging in live cells or deep tissues. The O-dots composed of trans-4-[p-(N, N-diethylamino)styryl]-4'-(dimethyl amino) stilbene (DEAS) emerged as TPA organic emissive cores and encapsulation by using poly (methyl methacrylate-co-methacrylic acid) (PMMA-co-MAA) as polymeric encapsulating matrix to form DEAS/PMMA-co-MAA O-dots via a co-precipitation strategy. The obtained O-dots enabled an extremely high TPA absorption cross-section, bright two-photon fluorescence (excitation at 720 nm; emission at 412 nm and 434 nm), excellent cell-permeability and high penetration depth. Sgc8c aptamer, as a protein tyrosine kinase-7 (PTK7) receptor-targetable ligand, was further anchored on the surface of O-dots to obtain DEAS/PMMA-co-MAA@Sgc8c nanoprobes by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)-mediated coupling reaction. Guided by Sgc8c aptamer, DEAS/PMMA-co-MAA@Sgc8c nanoprobes could be rapidly internalized into target acute lymphoblastic leukemia cells (CEM) cells with high specificity and great efficiency. It was also performed that two-photon images of TPA nanoprobes exhibited high two-photon brightness not only in target CEM cells, but also in mouse liver tissue slices even a depth of up to 210 μm. In our perception, it is highly promising that this nanoprobe provides a valuable tool for in vivo targeted imaging.

Recent advances in microfluidic methods in cancer liquid biopsy

Early cancer detection, its monitoring, and therapeutical prediction are highly valuable, though extremely challenging targets in oncology. Significant progress has been made recently, resulting in a group of devices and techniques that are now capable of successfully detecting, interpreting, and monitoring cancer biomarkers in body fluids. Precise information about malignancies can be obtained from liquid biopsies by isolating and analyzing circulating tumor cells (CTCs) or nucleic acids, tumor-derived vesicles or proteins, and metabolites. The current work provides a general overview of the latest on-chip technological developments for cancer liquid biopsy. Current challenges for their translation and their application in various clinical settings are discussed. Microfluidic solutions for each set of biomarkers are compared, and a global overview of the major trends and ongoing research challenges is given. A detailed analysis of the microfluidic isolation of CTCs with recent efforts that aimed at increasing purity and capture efficiency is provided as well. Although CTCs have been the focus of a vast microfluidic research effort as the key element for obtaining relevant information, important clinical insights can also be achieved from alternative biomarkers, such as classical protein biomarkers, exosomes, or circulating-free nucleic acids. Finally, while most work has been devoted to the analysis of blood-based biomarkers, we highlight the less explored potential of urine as an ideal source of molecular cancer biomarkers for point-of-care lab-on-chip devices.

A ratiometric electrochemical sensor for multiplex detection of cancer biomarkers using bismuth as an internal reference and metal sulfide nanoparticles as signal tags

Ratiometric electrochemical sensors can provide a relatively accurate analysis of target analytes due to their self-calibration function. Herein, we report a simple ratiometric strategy for achieving the electrochemical detection of Cd(ii), Hg(ii), Pb(ii) and Zn(ii), as well as multiple cancer biomarkers by using metal sulfide nanoparticles as signal tags. A conductive polymer film of poly(2-amino terephthalic acid) (ATA) was electrochemically produced on a glassy carbon electrode (GCE) and doped with carbon nanotubes (CNTs) and mercaptosuccinic acid (MSA). Using Bi(iii) as an enhancer and internal reference in anodic stripping voltammetry, the MSA-CNT-ATA/GCE exhibited sensitive and distinguishable voltammetric responses to Cd(ii), Hg(ii), Pb(ii) and Zn(ii), with detection limits of 0.13, 0.49, 0.16 and 0.089 μg L^-1, respectively. By using CdS, HgS, PbS and ZnS labeled secondary antibodies as the signal tags, alpha-fetoprotein, carbohydrate antigen 19-9, carbohydrate antigen 125, and carcinoembryonic antigen were determined simultaneously according to the amounts of metal sulfide in the sandwich-type complexes, with detection limits of 0.11 pg mL^-1, 0.68 mU mL^-1, 1.4 mU mL^-1 and 0.23 pg mL^-1, respectively. This ratiometric approach has a wide scope in the electrochemical detection of heavy metal ions as well as immunoassays with metal ions serving as signal tags.

A novel and accurate microfluidic assay of CD62L in bladder cancer serum samples

We report a low-cost, sensitive, bead-based electrochemical immunoarray for soluble L-selectin (or CD62L protein), a potential biomarker for staging bladder cancer. We used a semi-automated modular microfluidic array with online antigen capture on superparamagnetic beads, which were subsequently delivered to a detection chamber housing multiple sensors. The assay was designed to accurately detect CD62L in diluted serum with a limit of detection (LOD) of 0.25 ng mL-1 and a dynamic range of 0.25-100 ng mL-1. The microfluidic array gave significantly better accuracy and higher sensitivity than a standard ELISA kit, which was shown to be subject to significant systematic error at high and low concentration ranges. 31 serum samples from patients with varying grades of bladder cancer and cancer-free controls were analyzed by the immunoarray and ELISA, and the CD62L levels correlated. This work establishes a new accurate assay for determining CD62L levels and highlights the potential of this protein as a biomarker for detecting locoregional progression of bladder cancer.

Recent advances in magnetic fluid hyperthermia for cancer therapy

Recently, magnetic fluid hyperthermia using biocompatible magnetic nanoparticles as heat mediators for cancer therapy has been extensively investigated due to its high efficiency and limited side effects. However, the development of more efficient heat nanomediators that exhibit very high specific absorption rate (SAR) value is essential for clinical application to overcome the several restrictions previously encountered due to the large quantity of nanomaterial required for effective treatment. In this review, we focus on the current progress in the development of magnetic nanoparticles based hyperthermia therapy as well as combined therapy harnessing hyperthermia with heat-mediated drug delivery for cancer treatment. We also address the fundamental principles of magnetic hyperthermia, basics of magnetism including the effect of several parameters on heating capacity, synthetic methods and nanoparticle surface chemistry needed to design and develop an ideal magnetic nanoparticle heat mediator suitable for clinical translation in cancer therapy.

Recent Advances in Enhancement Strategies for Electrochemical ELISA-Based Immunoassays for Cancer Biomarker Detection

Electrochemical enzyme-linked immunosorbent assay (ELISA)-based immunoassays for cancer biomarker detection have recently attracted much interest owing to their higher sensitivity, amplification of signal, ease of handling, potential for automation and combination with miniaturized analytical systems, low cost and comparative simplicity for mass production. Their developments have considerably improved the sensitivity required for detection of low concentrations of cancer biomarkers present in bodily fluids in the early stages of the disease. Recently, various attempts have been made in their development and several methods and processes have been described for their development, amplification strategies and testing. The present review mainly focuses on the development of ELISA-based electrochemical immunosensors that may be utilized for cancer diagnosis, prognosis and therapy monitoring. Various fabrication methods and signal enhancement strategies utilized during the last few years for the development of ELISA-based electrochemical immunosensors are described.

Automated 3D-Printed Microfluidic Array for Rapid Nanomaterial-Enhanced Detection of Multiple Proteins

We report here the fabrication and validation of a novel 3D-printed, automated immunoarray to detect multiple proteins with ultralow detection limits. This low cost, miniature immunoarray employs electrochemiluminescent (ECL) detection measured with a CCD camera and employs touch-screen control of a micropump to facilitate automated use. The miniaturized array features prefilled reservoirs to deliver sample and reagents to a paper-thin pyrolytic graphite microwell detection chip to complete sandwich immunoassays. The detection chip achieves high sensitivity by using single-wall carbon nanotube-antibody conjugates in the microwells and employing massively labeled antibody-decorated RuBPY-silica nanoparticles to generate ECL. The total cost of an array is $0.65, and an eight-protein assay can be done in duplicate for $0.14 per protein with limits of detection (LOD) as low as 78-110 fg mL-1 in diluted serum. The electronic control system costs $210 in components. Utility of the automated immunoarray was demonstrated by detecting an eight-protein prostate cancer biomarker panel in human serum samples in 25 min. The system is well suited to future clinical and point-of-care diagnostic testing and could be used in resource-limited environments.

Distributed electrochemical sensors: recent advances and barriers to market adoption

Despite predictions of their widespread application in healthcare and environmental monitoring, electrochemical sensors are yet to be distributed at scale, instead remaining largely confined to R&D labs. This contrasts sharply with the situation for physical sensors, which are now ubiquitous and seamlessly embedded in the mature ecosystem provided by electronics and connectivity protocols. Although chemical sensors could be integrated into the same ecosystem, there are fundamental issues with these sensors in the three key areas of analytical performance, usability, and affordability. Nevertheless, advances are being made in each of these fields, leading to hope that the deployment of automated and user-friendly low-cost electrochemical sensors is on the horizon. Here, we present a brief survey of key challenges and advances in the development of distributed electrochemical sensors for liquid samples, geared towards applications in healthcare and wellbeing, environmental monitoring, and homeland security. As will be seen, in many cases the analytical performance of the sensor is acceptable; it is usability that is the major barrier to commercial viability at this moment. Were this to be overcome, the issue of affordability could be addressed. Graphical Abstract ᅟ.

Towards an Electrochemical Immunosensor System with Temperature Control for Cytokine Detection

The cytokine interleukin-13 (IL-13) plays a major role in airway inflammation and is a target of new anti-asthmatic drugs. Hence, IL-13 determination could be interesting in assessing therapy success. Thus, in this work an electrochemical immunosensor for IL-13 was developed and integrated into a fluidic system with temperature control for read-out. Therefore, two sets of results are presented. First, the sensor was set up in sandwich format on single-walled carbon nanotube electrodes and was read out by applying the hydrogen peroxide–hydroquinone–horseradish peroxidase (HRP) system. Second, a fluidic system was built up with an integrated heating function realized by Peltier elements that allowed a temperature-controlled read-out of the immunosensor in order to study the influence of temperature on the amperometric read-out. The sensor was characterized at the temperature optimum of HRP at 30 °C and at 12 °C as a reference for lower performance. These results were compared to a measurement without temperature control. At the optimum operation temperature of 30 °C, the highest sensitivity (slope) was obtained compared to lower temperatures and a limit of detection of 5.4 ng/mL of IL-13 was calculated. Taken together, this approach is a first step towards an automated electrochemical immunosensor platform and shows the potential of a temperature-controlled read-out.

Disease-Related Detection with Electrochemical Biosensors: A Review

Rapid diagnosis of diseases at their initial stage is critical for effective clinical outcomes and promotes general public health. Classical in vitro diagnostics require centralized laboratories, tedious work and large, expensive devices. In recent years, numerous electrochemical biosensors have been developed and proposed for detection of various diseases based on specific biomarkers taking advantage of their features, including sensitivity, selectivity, low cost and rapid response. This article reviews research trends in disease-related detection with electrochemical biosensors. Focus has been placed on the immobilization mechanism of electrochemical biosensors, and the techniques and materials used for the fabrication of biosensors are introduced in details. Various biomolecules used for different diseases have been listed. Besides, the advances and challenges of using electrochemical biosensors for disease-related applications are discussed.

Quantum dots: from fluorescence to chemiluminescence, bioluminescence, electrochemiluminescence, and electrochemistry

During the past decade, nanotechnology has become one of the major forces driving basic and applied research. As a novel class of inorganic fluorochromes, research into quantum dots (QDs) has become one of the fastest growing fields of nanotechnology today. QDs are made of a semiconductor material with tunable physical dimensions as well as unique optoelectronic properties, and have attracted multidisciplinary research efforts to further their potential bioanalytical applications. Recently, numerous optical properties of QDs, such as narrow emission band peaks, broad absorption spectra, intense signals, and remarkable resistance to photobleaching, have made them biocompatible and sensitive for biological assays. In this review, we give an overview of these exciting materials and describe their potential, especially in biomolecules analysis, including fluorescence detection, chemiluminescence detection, bioluminescence detection, electrochemiluminescence detection, and electrochemical detection. Finally, conclusions are made, including highlighting some critical challenges remaining and a perspective of how this field can be expected to develop in the future.

Gold-loaded nanoporous iron oxide nanocubes: a novel dispersible capture agent for tumor-associated autoantibody analysis in serum

Autoantibodies are produced against tumor associated antigens (TAAs) long before the appearance of any symptoms and thus can serve as promising, non-invasive biomarkers for early diagnosis of cancer. Current conventional methods for autoantibody detection are highly invasive and mostly provide diagnosis in the later stages of cancer. Herein we report a new electrochemical method for early detection of p53 autoantibodies against colon cancer using a strategy that combines the strength of gold-loaded nanoporous iron oxide nanocube (Au@NPFe₂O₃NC)-based capture and purification while incorporating the inherent simplicity, inexpensive, and portable nature of the electrochemical and naked-eye colorimetric readouts. After the functionalisation of Au@NPFe₂O₃NC with p53 antigens, our method utilises a two-step strategy that involves (i) magnetic capture and isolation of autoantibodies using p53/Au@NPFe₂O₃NC as 'dispersible nanocapture agents' in serum samples and (ii) subsequent detection of autoantibodies through a peroxidase-catalyzed reaction on a commercially available disposable screen-printed electrode or naked-eye detection in an Eppendorf tube. This method has demonstrated a good sensitivity (LOD = 0.02 U mL^-1) and reproducibility (relative standard deviation, %RSD = <5%, for n = 3) for detecting p53 autoantibodies in serum and has also been successfully applied to analyse a small cohort of clinical samples obtained from colorectal cancer. We believe that the highly inexpensive, rapid, sensitive, and specific nature of our assay could potentially aid in the development of an early diagnostic tool for cancer and related diseases.

Fe3O4 nanoparticles on graphene oxide sheets for isolation and ultrasensitive amperometric detection of cancer biomarker proteins

Ultrasensitive mediator-free electrochemical detection for biomarker proteins was achieved at low cost using a novel composite of Fe3O4 nanoparticles loaded onto graphene oxide (GO) nano-sheets (Fe3O4@GO). This paramagnetic Fe3O4@GO composite (1µm size range) was decorated with antibodies against prostate specific antigen (PSA) and prostate specific membrane antigen (PSMA), and then used to first capture these biomarkers and then deliver them to an 8-sensor detection chamber of a microfluidic immunoarray. Screen-printed carbon sensors coated with electrochemically reduced graphene oxide (ERGO) and a second set of antibodies selectively capture the biomarker-laden Fe3O4@GO particles, which subsequently catalyze hydrogen peroxide reduction to detect PSA and PSMA. Accuracy was confirmed by good correlation between patient serum assays and enzyme-linked immuno-sorbent assays (ELISA). Excellent detection limits (LOD) of 15 fg/mL for PSA and 4.8 fg/mL for PSMA were achieved in serum. The LOD for PSA was 1000-fold better than the only previous report of PSA detection using Fe3O4. Dynamic ranges were easily tunable for concentration ranges encountered in serum samples by adjusting the Fe3O4@GO Concentration. Reagent cost was only $0.85 for a single 2-protein assay.

Electrochemical Genosensing of Circulating Biomarkers

Management and prognosis of diseases requires the measurement in non- or minimally invasively collected samples of specific circulating biomarkers, consisting of any measurable or observable factors in patients that indicate normal or disease-related biological processes or responses to therapy. Therefore, on-site, fast and accurate determination of these low abundance circulating biomarkers in scarcely treated body fluids is of great interest for health monitoring and biological applications. In this field, electrochemical DNA sensors (or genosensors) have demonstrated to be interesting alternatives to more complex conventional strategies. Currently, electrochemical genosensors are considered very promising analytical tools for this purpose due to their fast response, low cost, high sensitivity, compatibility with microfabrication technology and simple operation mode which makes them compatible with point-of-care (POC) testing. In this review, the relevance and current challenges of the determination of circulating biomarkers related to relevant diseases (cancer, bacterial and viral infections and neurodegenerative diseases) are briefly discussed. An overview of the electrochemical nucleic acid-based strategies developed in the last five years for this purpose is given to show to both familiar and non-expert readers the great potential of these methodologies for circulating biomarker determination. After highlighting the main features of the reported electrochemical genosensing strategies through the critical discussion of selected examples, a conclusions section points out the still existing challenges and future directions in this field.

Automated 3D-printed unibody immunoarray for chemiluminescence detection of cancer biomarker proteins

A low cost three-dimensional (3D) printed clear plastic microfluidic device was fabricated for fast, low cost automated protein detection. The unibody device features three reagent reservoirs, an efficient 3D network for passive mixing, and an optically transparent detection chamber housing a glass capture antibody array for measuring chemiluminescence output with a CCD camera. Sandwich type assays were built onto the glass arrays using a multi-labeled detection antibody-polyHRP (HRP = horseradish peroxidase). Total assay time was ∼30 min in a complete automated assay employing a programmable syringe pump so that the protocol required minimal operator intervention. The device was used for multiplexed detection of prostate cancer biomarker proteins prostate specific antigen (PSA) and platelet factor 4 (PF-4). Detection limits of 0.5 pg mL-1 were achieved for these proteins in diluted serum with log dynamic ranges of four orders of magnitude. Good accuracy vs. ELISA was validated by analyzing human serum samples. This prototype device holds good promise for further development as a point-of-care cancer diagnostics tool.

Evaluation of disposable microfluidic chip design for automated and fast Immunoassays

We report here, the design and development of a disposable immunoassay chip for protein biomarker detection within ∼1 h. The unique design allows for real-time dynamic calibration of immunoassay for multiple biomarker detections on the chip. The limit of detection achieved for this test chip is 10 pg/ml for IL6, and 50 pg/ml for GFAP with a detection time of 1 h. The prototype instrument used for flowing the reagents through the chip can be easily assembled from off-the-shelf components with the final chemiluminescent detection carried out in a commercial plate reader. Optimization of different aspects of chip design, fabrication, and assay development is discussed in detail.

Multiplex Immunosensor Arrays for Electrochemical Detection of Cancer Biomarker Proteins

Measuring panels of protein biomarkers offer a new personalized approach to early cancer detection, disease monitoring and patients' response to therapy. Multiplex electrochemical methods are uniquely positioned to provide faster, more sensitive, point of care (POC) devices to detect protein biomarkers for clinical diagnosis. Nanomaterials-based electrochemical methods offer sensitivity needed for early cancer detection. This review discusses recent advances in multiplex electrochemical immunosensors for cancer diagnostics and disease monitoring. Different electrochemical strategies including enzyme-based immunoarrays, nanoparticle-based immunoarrays and electrochemiluminescence methods are discussed. Many of these methods have been integrated into microfluidic systems, but measurement of more than 2-4 protein markers in a small single serum sample is still a challenge. For POC applications, a simple, low cost method is required. Major challenges in multiplexed microfluidic immunoassays are reagent additions and washing steps that require creative engineering solutions. 3-D printed microfluidics and paper-based microfluidic devices are also explored.

Antibody-like Biorecognition Sites for Proteins from Surface Imprinting on Nanoparticles

Natural antibodies are used widely for important applications such as biomedical analysis, cancer therapy, and directed drug delivery, but they are expensive and may have limited stability. This study describes synthesis of antibody-like binding sites by molecular imprinting on silica nanoparticles (SiNP) using a combination of four organosilane monomers with amino acid-like side chains providing hydrophobic, hydrophilic, and H-bonding interactions with target proteins. This approach provided artificial antibody (AA) nanoparticles with good selectivity and specificity to binding domains on target proteins in a relatively low-cost synthesis. The AAs were made by polymer grafting onto SiNPs for human serum albumin (HSA) and glucose oxidase (GOx). Binding affinity, selectivity, and specificity was compared to several other proteins using adsorption isotherms and surface plasmon resonance (SPR). The Langmuir-Freundlich adsorption model was used to obtain apparent binding constants (KLF) from binding isotherms of HSA (6.7 × 10(4)) and GOx (4.7 × 10(4)) to their respective AAs. These values were 4-300 fold larger compared to a series of nontemplate proteins. SPR binding studies of AAs with proteins attached to a gold surface confirmed good specificity and revealed faster binding for the target proteins compared to nontarget proteins. Target proteins retained their secondary structures upon binding. Binding capacity of AAHSA for HSA was 5.9 mg HSA/g compared to 1.4 mg/g for previously report imprinted silica beads imprinted with poly(aminophenyl)boronic acid. Also, 90% recovery for HSA spiked into 2% calf serum was found for AAHSA.