A biosensor for determination of the circulating biomarker CA125/MUC16 by Surface Plasmon Resonance Imaging

Construction of scalable multi-channel DNA nanoplatform for the combined detection of ctDNA biomarkers of ovarian cancer

Single-level biomarker detection has the limitation of insufficient accuracy in cancer diagnosis. Therefore, the strategy of developing highly sensitive, multi-channel biosensors for high-throughput ctDNA determination is critical to improve the accuracy of early diagnosis of clinical tumors. Herein, in order to achieve efficient detection of up to ten targets for early diagnosis of ovarian cancer, a DNA-nanoswitch-based multi-channel (DNA-NSMC) biosensor was built based on the multi-module catalytic hairpin assembly-mediated signal amplification (CHA) and toehold-mediated DNA strand displacement (TDSD) reaction. Only two different fluorescence signals were used as outputs, combined with modular segmentation strategy of DNA-nanoswitch-based reaction platform; the multi-channel detection of up to ten targets was successfully achieved for the first time. The experimental results suggest that the proposed biosensor is a promising tool for simultaneously detecting multiple biomarkers for the early diagnosis of ovarian cancer, offering new strategies for the early screening, diagnosis, and treatment not only for ovarian cancer but also for other cancers.

One-step detection of procollagen type III N-terminal peptide as a fibrosis biomarker using fluorescent immunosensor (quenchbody)

BACKGROUND

Procollagen type III N-terminal peptide (P-III-NP) is a fibrosis biomarker associated with liver and cardiac fibrosis. Despite the value of P-III-NP as a biomarker, its analysis currently relies on enzyme-linked immunosorbent assays (ELISA) and radioimmunoassays (RIA), which require more than 3 h. To facilitate early diagnosis and treatment through rapid biomarker testing, we developed a one-step immunoassay for P-III-NP using a quenchbody, which is a fluorescence-labeled immunosensor for immediate signal generation.

RESULTS

To create quenchbodies, the total mRNA of P-III-NP antibodies was extracted from early-developed hybridoma cells, and genes of variable regions were obtained through cDNA synthesis, inverse PCR, and sequencing. A single-chain variable fragment (scFv) with an N-terminal Cys-tag was expressed in E. coli Shuffle T7, resulting in a final yield of 9.8 mg L-1. The fluorescent dye was labeled on the Cys-tag of the anti-P-III-NP scFv using maleimide-thiol click chemistry, and the spacer arm lengths between the maleimide-fluorescent dyes were compared. Consequently, a TAMRA-C6-labeled quenchbody exhibited antigen-dependent fluorescence signals and demonstrated its ability to detect P-III-NP at concentrations as low as 0.46 ng mL-1 for buffer samples, 1.0 ng mL-1 for 2 % human serum samples.

SIGNIFICANCE

This one-step P-III-NP detection method provides both qualitative and quantitative outcomes within a concise 5-min timeframe. Furthermore, its application can be expanded using a 96-well platform and human serum, making it a high-throughput and sensitive method for testing fibrotic biomarkers.

CdS/Bi2S3/NiS ternary heterostructure-based photoelectrochemical immunosensor for the sensitive detection of carbohydrate antigen 125

The sensitive, accurate and rapid detection of carbohydrate antigen 125 (CA125) is essential for the early diagnosis and clinical management of ovarian cancer, but there is still challenge. Herein, a photoelectrochemical (PEC) immunosensor based on CdS/Bi2S3/NiS ternary sulfide heterostructured photocatalyst was presented for the detection of CA125. The CdS/Bi2S3/NiS was synthesized by a one-step hydrothermal approach. The heterojunction comprising of CdS and Bi2S3 could separate photogenerated carriers, the introduced narrow bandgap NiS could act as electron-conducting bridge to facilitate the transfer of interfacial photogenerated electrons, thereby improving the photoelectric conversion efficiency. Due to their synergistic effect, the photocurrent response produced by the composite was up to 14.6 times of pure CdS. On the basis, a PEC immunosensor was constructed by introducing the CA125 antibody through thioglycolic acid linkage. It was found that the resulting immunosensor showed good performance. Under the optimized conditions, its linear detection range was as wide as 1 pg mL-1-50 ng mL-1, and the detection limit was low to 0.85 pg mL-1. Furthermore, we experimentally tested its anti-interference, stability and reproducibility, and satisfactory results were achieved. The practicable feasibility of the sensor was confirmed by testing serum sample. Thus this work provided a simple, fast and enough sensitive approach for CA125 monitoring.

Ultrasensitive Quantification of MUC16 Antigen/Amine-Terminated Aptamer Interaction by Surface Plasmon Resonance: Kinetic and Thermodynamic Studies

Purpose

MUC16 is a commonly employed biomarker to identify and predict ovarian cancer (OC). Precise measurement of MUC16 levels is essential for the accurate diagnosis, prediction, and management of OC. This research seeks to introduce a new surface plasmon resonance (SPR) biosensor design that utilizes aptamer-based technology to enable the sensitive and real-time detection of MUC16.

Methods

In this study, the sensor chip was immobilized with an anti-MUC16 aptamer (Ap) by utilizing 11-mercaptoundecanoic acid (MUA) as a linker to attach the amine-terminated Ap to the chip using EDC/NHS chemistry.

Results

The results indicated that the newly created aptasensor had a detection limit of 0.03 U/mL for MUC16 concentration, with a linear range of 0.09 to 0.27 U/mL. The findings demonstrate good precision and accuracy (<15%) for each MUC16 concentration, with recoveries ranging from 93% to 96%. Additionally, the aptasensor exhibited high selectivity, good repeatability, stability, and applicability in real human serum samples, indicating its potential as a valuable tool for the diagnosis and treatment of OC.

Conclusion

According to the outcomes, the designed aptasensor exhibited acceptable specificity to detect the CA125 antigen and could be utilized for the serum detection of target antigen by SPR method.

Selective determination of an ovarian cancer biomarker at low concentrations with surface imprinted nanotube based chemosensor

In this study, an electrochemical chemosensor that utilizes a conductive polymer-based molecularly imprinted polymer (MIP) surface for rapid and reliable determination of CA125 was devised. A novel method has been applied to fabricate CA125 imprinted polypyrrole nanotubes (MI-PPy NT) via vapor deposition polymerization (VDP) as a recognition element for highly selective and sensitive determination of CA125. The chemosensor was prepared by immobilizing MI-PPy NT onto screen-printed gold electrodes (Au-SPE) and the performance of the sensor was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in terms of selectivity, sensitivity, linear dynamic concentration range (LDR) and limit of detection (LOD). The MI-PPy NT@Au-SPE sensor exhibited high sensitivity (68.57 μA per decade) to the CA125 concentration ranging from 0.1 U mL-1 to 100 U mL-1 at an LOD of 0.4 U mL-1 with a correlation coefficient of 0.9922. The developed chemosensors with their novel design combined with a facile fabrication method, prove to be promising as future state-of-the-art biosensors.

Research progress of All-in-One PCR tube biosensors based on functional modification and intelligent fabrication

PCR amplification technology is the cornerstone of molecular biology. All-in-One PCR tube, as an emerging integrated device, is booming in biosensors application. All-in-One PCR tube biosensors are integrated PCR tubes designed for signal recognition, signal amplification or signal output. They enable "one-pot" detection within functionally modified and intelligently fabricated PCR tubes, effectively overcoming the limitations of conventional PCR applications, like complex procedural steps, risk of contamination and so on. Based on this, the review article summarizes the recent advance of All-in-One PCR tube biosensors for the first time as well as systematically categorizes five approaches of functional modification, three types of intelligent fabrication and relevant property characterization techniques. More emphasis is placed on the review of five ways of functional modification, including physical modification, chemical modification, UV photografting surface treatment, plasma surface modification, and layer-by-layer assembly coating. Moreover, All-in-One PCR tube biosensors covering different recognition elements range from small molecules to protein are detailed discussed on principle of sensing, providing a deeper understanding of the design and application of All-in-One-tube biosensor. Last, the future opportunities and challenges in this fascinating field are also deliberated.

Ultrasensitive detection of CA125 based on a triple signal amplification strategy with a huge number of loaded probes via exonuclease cyclic cleavage, rolling cyclic amplification and strand self-growth

A novel electrochemiluminescence (ECL) aptamer biosensor with high sensitivity and selectivity for the detection of tumor biomarker carbohydrate antigen 125 (CA125) was constructed, and a strategy of triple amplification of signals was proposed using an exonuclease cyclic cleavage aptamer, combined with rolling ring amplification technologies, generating multi-branched dendritic double-stranded DNA to load a large number of probes through "strand self-growth". The double-stranded DNA, which is abbreviated as CP/CA dsDNA, formed by hybridizing the single strand of capture DNA (CP DNA) with the single strand DNA of the CA125 aptamer (CA Apt) was modified on Fe₃O₄@Au. When CA125 was added, CP/CA dsDNA was unwound, and CA125 specifically combined with CA Apt to form a protein-aptamer complex, leaving only CP DNA on the surface of Fe₃O₄@Au. RecJ_f exonuclease cleaved the aptamer in the protein-aptamer complex and released CA125, which recombined with other CA125 aptamers, to form a cycle that produces more CP DNA on Fe₃O₄@Au. Three ssDNA (H1, H2, and H3) were introduced and hybridized with CP DNA to form a dsDNA with a "+" configuration structure. Then phi29 DNA polymerase, T4 DNA ligase, deoxy-ribonucleoside triphosphate (dNTP) and padlock probes were added to form a large number of complementary strands of padlock probes (CS padlock probes) by rolling cyclic amplification. CS padlock probes were linked to the "+" type dsDNA; then ssDNA H4 was added and hybridized with the CS padlock probe to form multi-branched dendritic dsDNA. A large number of tris(2,2'-bipyridyl)ruthenium(II) probes were embedded in the double strands, resulting in an extremely strong ECL signal in the presence of the co-reactant tri-n-propylamine (TPA). There is a linear relationship between the ECL signals and CA125 concentrations in the range of 1.0 × 10^-15-1.0 × 10^-8 mg mL^-1, and the detection limit was 2.38 × 10^-16 mg mL^-1. It has been used for the determination of CA125 in serum samples.

Application of Metal-Based Nanomaterials in In Vitro Diagnosis of Tumor Markers: Summary and Prospect

Cancer, which presents with high incidence and mortality rates, has become a significant health threat worldwide. However, there is currently no effective solution for rapid screening and high-quality treatment of early-stage cancer patients. Metal-based nanoparticles (MNPs), as a new type of compound with stable properties, convenient synthesis, high efficiency, and few adverse reactions, have become highly competitive tools for early cancer diagnosis. Nevertheless, challenges such as the difference between the microenvironment of detected markers and the real-life body fluids remain in achieving widespread clinical application of MNPs. This review provides a comprehensive review of the research progress made in the field of in vitro cancer diagnosis using metal-based nanoparticles. By delving into the characteristics and advantages of these materials, this paper aims to inspire and guide researchers towards fully exploiting the potential of metal-based nanoparticles in the early diagnosis and treatment of cancer.

Recent advances in surface plasmon resonance imaging and biological applications

Surface Plasmon Resonance Imaging (SPRI) is a robust technique for visualizing refractive index changes, which enables researchers to observe interactions between nanoscale objects in an imaging manner. In the past period, scholars have been attracted by the Prism-Coupled and Non-prism Coupled configurations of SPRI and have published numerous experimental results. This review describes the principle of SPRI and discusses recent developments in Prism-Coupled and Non-prism Coupled SPRI techniques in detail, respectively. And then, major advances in biological applications of SPRI are reviewed, including four sub-fields (cells, viruses, bacteria, exosomes, and biomolecules). The purpose is to briefly summarize the recent advances of SPRI and provide an outlook on the development of SPRI in various fields.

A sandwich electrochemical immunosensor based on MXene@dual MOFs for detection of tumor marker CA125

The detection signal of carbohydrate antigen 125 (CA125) can be quantitatively amplified via the dual metal-organic framework (MOF) sandwich strategy. We propose a versatile method for synthesizing uniform MXene and MIL-101(Fe)-NH₂ composites that combine the advantages of both materials to build a base layer with superb performance. MXene exhibits excellent electrical conductivity and high surface area. The mesoporous MIL-101(Fe)-NH₂ not only increases the loading capacity of the primary antibody but also possesses the catalytic activity of the metal center (Fe). UiO66 loaded with methylene blue (MB) was fabricated as an electrochemical immunosensor signal tag to enable the detection of CA125. The mixture of MXene and MIL-101(Fe)-NH₂ prepared as the substrate was fixed by chitosan rich in amino groups. As the signal amplification sector, UiO66@MB enhanced secondary antibody loading capacity and generated a redox signal enabling the detection of antigenic substances. The proposed electrochemical immunosensor demonstrated high sensitivity with a low limit of detection (LOD) of 0.006 U/mL. Therefore, the dual MOF sandwich-based immunosensor provides a novel method for the early diagnosis of CA125.

Recent Trends in Biosensing and Diagnostic Methods for Novel Cancer Biomarkers

Cancer is one of the major public health issues in the world. It has become the second leading cause of death, with approximately 75% of cancer deaths transpiring in low- or middle-income countries. It causes a heavy global economic cost estimated at more than a trillion dollars per year. The most common cancers are breast, colon, rectum, prostate, and lung cancers. Many of these cancers can be treated effectively and cured if detected at the primary stage. Nowadays, around 50% of cancers are detected at late stages, leading to serious health complications and death. Early diagnosis of cancer diseases substantially increases the efficient treatment and high chances of survival. Biosensors are one of the potential screening methodologies useful in the early screening of cancer biomarkers. This review summarizes the recent findings about novel cancer biomarkers and their advantages over traditional biomarkers, and novel biosensing and diagnostic methods for them; thus, this review may be helpful in the early recognition and monitoring of treatment response of various human cancers.

Surface Plasmon Resonance (SPR) Sensor for Cancer Biomarker Detection

A biomarker is a physiological observable marker that acts as a stand-in and, in the best-case scenario, forecasts a clinically significant outcome. Diagnostic biomarkers are more convenient and cost-effective than directly measuring the ultimate clinical outcome. Cancer is among the most prominent global health problems and a major cause of morbidity and death globally. Therefore, cancer biomarker assays that are trustworthy, consistent, precise, and verified are desperately needed. Biomarker-based tumor detection holds a lot of promise for improving disease knowledge at the molecular scale and early detection and surveillance. In contrast to conventional approaches, surface plasmon resonance (SPR) allows for the quick and less invasive screening of a variety of circulating indicators, such as circulating tumor DNA (ctDNA), microRNA (miRNA), circulating tumor cells (CTCs), lipids, and proteins. With several advantages, the SPR technique is a particularly beneficial choice for the point-of-care identification of biomarkers. As a result, it enables the timely detection of tumor markers, which could be used to track cancer development and suppress the relapse of malignant tumors. This review emphasizes advancements in SPR biosensing technologies for cancer detection.

A Multiple-Array SPRi Biosensor as a Tool for Detection of Gynecological-Oncological Diseases

Diagnostics based on the determination of biomarkers in body fluids will be more successful when several biomarkers are determined. A multiple-array SPRi biosensor for the simultaneous determination of CA125, HE4, CEA, IL-6 and aromatase has been developed. Five individual biosensors were placed on the same chip. Each of them consisted of a suitable antibody covalently immobilized onto a gold chip surface via a cysteamine linker by means of the NHS/EDC protocol. The biosensor for IL-6 works in the pg mL^-1 range, that for CA125 in the µg mL^-1 range, and the other three within the ng mL^-1 range; these are ranges suitable for the determination of biomarkers in real samples. The results obtained with the multiple-array biosensor are very similar to those obtained with a single biosensor. The applicability of the multiple biosensor was demonstrated using several examples of plasma from patients suffering from ovarian cancer and endometrial cyst. The average precision was 3.4% for the determination of CA125, 3.5% for HE4, 5.0% for CEA and IL-6, and 7.6% for aromatase. The simultaneous determination of several biomarkers may be an excellent tool for the screening of the population for earlier detection of diseases.

Application of Various Optical and Electrochemical Nanobiosensors for Detecting Cancer Antigen 125 (CA-125): A Review

Nowadays, diagnosing early-stage cancers can be vital for saving patients and dramatically decreases mortality rates. Therefore, specificity and sensitivity in the detection of cancer antigens should be elaborately ensured. Some early-stage cancers can be diagnosed via detecting the cancer antigen CA-125, such as ovarian cancer, and required treatments can be applied more efficiently. Thus, detection of CA-125 by employing various optical or electrochemical biosensors is a preliminary and crucial step to treating cancers. In this review, a diverse range of optical and electrochemical means of detecting CA-125 are reviewed. Furthermore, an applicable comparison of their performance and sensitivity is provided, several commercial detection kits are investigated, and their applications are compared and discussed to determine whether they are applicable and accurate enough.

Two Biosensors for the Determination of Interleukin-6 in Blood Plasma by Array SPRi

Interleukin-6 (IL-6) is a biomarker of inflammation, the advanced stage of COVID-19, and several cancers, including ovarian cancer. Two biosensors for the determination of IL-6 in blood plasma by array SPRi have been developed. One of these biosensors consists of the mouse monoclonal anti-IL-6 antibody as the receptor immobilized via the cysteamine linker. The second contains galiellalactone as the receptor, being an inhibitor specific for IL-6, immobilized via octadecanethiol (ODM) as the linker. Both biosensors are specific for IL-6. The biosensor with the antibody as the receptor gives a linear analytical response between 3 (LOQ) and 20 pg mL⁻¹ and has a precision between 8% and 9.8% and recovery between 97% and 107%, depending on the IL-6 concentration. The biosensor with galiellalactone as the receptor gives a linear analytical response between 1.1 (LOQ) and 20 pg mL⁻¹, and has a precision between 3.5% and 9.3% and recovery between 101% and 105%, depending on IL-6 concentration. Both biosensors were validated. Changes in IL-6 concentration in blood plasma before and after resection of ovarian tumor and endometrial cyst, as determined by the two developed biosensors, are given as an example of a real clinical application.

Detection of cancer biomarkers CA125 and CA199 via terahertz metasurface immunosensor

The cancer biomarkers including AFP, CEA, CA199 and CA125, are of great importance in the diagnosis, prognostic prediction and recurrence monitoring of malignancies. However, in clinical practical applications, most tumor cancer biomarkers are lack of sensitivity and specificity. In this study, we propose a terahertz (THz) metasurface (MS) immunosensor coupled with gold nanoparticles (AuNPs), which have good biocompatibility and high specific surface area for biomarkers. Firstly, we added AuNPs to the surface of the sensor. And then, the surface is modified with Anti-CA125 or Anti-CA199 to improve the sensitivity and specificity to the target antigen. The biosensor was fabricated using a surface micromachining process and characterized by a THz-time-domain spectroscopy (TDS) system. The sensitivity of the resonance frequency of the sensor to the refractive index was 65 GHz/RIU (refractive index unit). The detection performance of the THz immunosensor was also verified with different concentrations of CA125 and CA199. The experimental results showed that the frequency shift of the resonance peak was linearly related to the concentration of CA125 and CA199. The detection limits for both CA125 and CA199 are 0.01 U/ml, which is better than that of other common methods. Finally, serum samples were collected and detected to explore whether this method is suitable for clinical detection. The results are consistent with the results of antigen recognition. This study proves that the practicability of the THz immunosensor, which potentially provides important techniques and equipment for improving the sensitivity and specificity of cancer biomarkers.

Antifouling peptides combined with recognizing DNA probes for ultralow fouling electrochemical detection of cancer biomarkers in human bodily fluids

Herein, a universal strategy for the construction of highly sensitive and low fouling biosensors was proposed based on antifouling peptides conjugated with recognizing DNA probes. The peptide-DNA conjugate was formed through a reagent-free click reaction between a typical DNA aptamer modified with 5'-dibenzocyclooctyne (DBCO) and the designed antifouling peptide terminated with biotin and the azide group at its two ends. With the assistance of streptavidin (SA), the electrochemical biosensor was constructed via immobilization of the straight peptides and peptide-DNA conjugates in sequence onto the electrode surface modified with electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) and gold nanoparticles (AuNPs). The prepared biosensor exhibited excellent antifouling performances in various human bodily fluids such as serum, sweat and urine, with a wide linear response range for CA125 from 0.01 U mL^-1 to 1000 U mL^-1, and a low limit of detection of 0.003 U mL^-1. Combining the advantages of the antifouling peptide and recognizing DNA probe, this sensing strategy was capable of assaying CA125 in undiluted human serum, and it also offered a highly promising way for the development of different antifouling biosensors through the conjugation of antifouling peptides with various DNA probes.

Advances in surface plasmon resonance-based biosensor technologies for cancer biomarker detection

Surface plasmon resonance approach is a highly useful option to offer optical and label-free detection of target bioanalytes with numerous advantages (e.g., low-cost fabrication, appreciable sensitivity, label-free detection, and outstanding accuracy). As such, it allows early diagnosis of cancer biomarkers to monitor tumor progression and to prevent the recurrence of oncogenic tumors. This work highlights the recent progress in SPR biosensing technology for the diagnosis of various cancer types (e.g., lung, breast, prostate, and ovarian). Further, the performance of various SPR biosensors is also evaluated in terms of the basic quality assurance criteria (e.g., limit of detection (LOD), selectivity, sensor response time, and reusability). Finally, the limitations and future challenges associated with SPR biosensors are also discussed with respect to cancer biomarker detection.

Nanoscale SPR sensor for the ultrasensitive detection of the ovarian cancer marker carbohydrate antigen 125

In this study, a nanoscale surface plasmon resonance (SPR) sensor was developed to determine the ovarian cancer marker carbohydrate antigen (CA) 125 level in serum utilizing the molecular imprinting method.

A Comparison of Various Chips Used for the Manufacture of Biosensors Applied in Non-Fluidic Array SPRi, Based on the Example of Determination of Cathepsin D

Non-fluidic array SPR imaging (SPRi) with appropriate biosensors is a new tool for the determination of various biomarkers in body fluids. Numerous biomarkers can be determined without signal enhancement or preliminarily preconcentration. The introduction of a new material solution of the chip may increase the scope of the application of this technique. Solutions with adhesive separating foil and an Ag/Au chip were compared with the previously used two-paint separating polymer and pure gold chip. These solutions were tested using the example of a biosensor for cathepsin D (Cath D), which consisted of pepstatin A (a Cath D inhibitor) immobilized via a cysteamine linker using the NHS/EDC protocol. Four material versions of the Cath D biosensor proved adequate in terms of range of linearity, LOQ, precision and recovery. All four versions of the biosensor were used for the determination of Cath D in the blood serum patients with glioblastoma and control samples, producing very similar results and showing an elevated biomarker concentration in the case of cancer. Therefore, the problem of determining the correct level of Cath D in the serum of healthy individuals has been resolved, correcting literature data which ranged over three orders of magnitude.

Aptamer-Sensitized Nanoribbon Biosensor for Ovarian Cancer Marker Detection in Plasma

The detection of CA 125 protein in buffer solution with a silicon-on-insulator (SOI)-based nanoribbon (NR) biosensor was experimentally demonstrated. In the biosensor, sensor chips, bearing an array of 12 nanoribbons (NRs) with n-type conductance, were employed. In the course of the analysis with the NR biosensor, the target protein was biospecifically captured onto the surface of the NRs, which was sensitized with covalently immobilized aptamers against CA 125. Atomic force microscopy (AFM) and mass spectrometry (MS) were employed in order to confirm the formation of the probe–target complexes on the NR surface. Via AFM and MS, the formation of aptamer–antigen complexes on the surface of SOI substrates with covalently immobilized aptamers against CA 125 was revealed, thus confirming the efficient immobilization of the aptamers onto the SOI surface. The biosensor signal, resulting from the biospecific interaction between CA 125 and the NR-immobilized aptamer probes, was shown to increase with an increase in the target protein concentration. The minimum detectable CA 125 concentration was as low as 1.5 × 10−17 M. Moreover, with the biosensor proposed herein, the detection of CA 125 in the plasma of ovarian cancer patients was demonstrated.

Recent Advancements in Receptor Layer Engineering for Applications in SPR-Based Immunodiagnostics

The rapid progress in the development of surface plasmon resonance-based immunosensing platforms offers wide application possibilities in medical diagnostics as a label-free alternative to enzyme immunoassays. The early diagnosis of diseases or metabolic changes through the detection of biomarkers in body fluids requires methods characterized by a very good sensitivity and selectivity. In the case of the SPR technique, as well as other surface-sensitive detection strategies, the quality of the transducer-immunoreceptor interphase is crucial for maintaining the analytical reliability of an assay. In this work, an overview of general approaches to the design of functional SPR-immunoassays is presented. It covers both immunosensors, the design of which utilizes well-known and often commercially available substrates, as well as the latest solutions developed in-house. Various approaches employing chemical and passive binding, affinity-based antibody immobilization, and the introduction of nanomaterial-based surfaces are discussed. The essence of their influence on the improvement of the main analytical parameters of a given immunosensor is explained. Particular attention is paid to solutions compatible with the latest trends in the development of label-free immunosensors, such as platforms dedicated to real-time monitoring in a quasi-continuous mode, the use of in situ-generated receptor layers (elimination of the regeneration step), and biosensors using recombinant and labelled protein receptors.

An SPRi Biosensor for Determination of the Ovarian Cancer Marker HE4 in Human Plasma

Human epididymis protein 4 (HE4) is an ovarian cancer marker. Various cut-off values of the marker in blood are recommended, depending on the method used for its determination. An alternative biosensor for HE4 determination in blood plasma has been developed. It consists of rabbit polyclonal antibody against HE4, covalently attached to a gold chip via cysteamine linker. The biosensor is used with the non-fluidic array SPRi technique. The linear range of the analytical signal response was found to be 2-120 pM, and the biosensor can be used for the determination of the HE4 marker in the plasma of both healthy subjects and ovarian cancer patients after suitable dilution with a PBS buffer. Precision (6-10%) and recovery (101.8-103.5%) were found to be acceptable, and the LOD was equal to 2 pM. The biosensor was validated by the parallel determination of a series of plasma samples from ovarian cancer patients using the Elecsys HE4 test and the developed biosensor, with a good agreement of the results (a Pearson coefficient of 0.989). An example of the diagnostic application of the developed biosensor is given-the influence of ovarian tumor resection on the level of HE4 in blood serum.

MUC16 promotes EOC proliferation by regulating GLUT1 expression

As a common malignancy in females with a higher incidence rate, epithelial ovarian cancer (EOC) is a heterogeneous disease with complexity and diversity in histology and therapeutic response. Although great progress has been made in diagnosis and therapeutic strategies, novel therapeutic strategies are required to improve survival. Although the promoting effect of mucin 16 (MUC16) on tumour progression has been reported, the potential mechanisms remain unclear. In our study, we reported that overexpression of MUC16 was significantly related to cell proliferation and disease progression in EOC. Results from clinical specimen analysis and cell experiment support this conclusion. Patients with a high MUC16 expression usually had a worse prognosis that those with a low expression. Cell proliferation ability was significantly decreased in EOC cell lines when the knockdown of MUC16. Further study shows that the function of MUC16 in cell proliferation is based on the regulation of glucose transporter 1 (GLUT1) expression. MUC16 can control glucose uptake by regulating GLUT1 in EOC cells, thereby promoting glycogen synthesis, so that tumour cells produce more energy for proliferation. This conclusion is based on two findings. First, the significant correlation between MUC16 and GLUT1 was verified by clinical specimen and TCGA data analysis. Then, alteration of MUC16 expression levels can affect the expression of GLUT1 and glucose uptake was also verified. Finally, this conclusion is further verified in vivo by tumour‐bearing mice model. To summarize, our results suggest that MUC16 promotes EOC proliferation and disease progression by regulating GLUT1 expression.

Potential of surface plasmon resonance biosensors in cancer detection

A review is made of 71 papers on surface plasmon resonance biosensors, published between 2005 and 2020, mostly in the last decade. The reviewed papers are divided into two groups, depending on the validation of the developed biosensor. Validated biosensors are briefly characterized, while those that are not validated are listed in a table. Focus is placed on applications of SPR biosensors in testing the effectiveness of cancer markers and in the discovery of new cancer markers. Seven new markers are proposed, two of them having high sensitivity and diagnostic selectivity as determined by ROC curves. Papers concerning the determination of micro RNA and large particles such as vesicles, exosomes and cancer cells are also reviewed.

An immunosensor for the determination of carcinoembryonic antigen by Surface Plasmon Resonance imaging

Carcinoembryonic antigen (CEA) is one of the biomarkers most commonly used to determine tumor activity. In this work, a Surface Plasmon Resonance imaging (SPRi) immunosensor was developed. The immunosensor consists of a cysteamine linker attached to a gold chip and mouse monoclonal anti-CEA antibody bonded by the "EDC/NHS protocol". The formation of successive immunosensor layers was confirmed by AFM measurements. The concentration of the antibody was optimized. The linear response range of the developed immunosensor is between 0.40 and 20 ng mL^-1, and it is suitable for CEA measurement in both blood cancer patients and healthy individuals. Only 3 μL of serum or plasma sample is required, and no preconcentration is used. The method has a precision of 2-16%, a recovery of 101-104% depending on CEA concentration, a detection limit of 0.12 ng mL^-1 and a quantification limit of 0.40 ng mL^-1. The method is selective (with respect to albumin, leptin, interleukin 6, metalloproteinase-1, metallopeptidase inhibitor 1 and CA 125/MUC16) and it was validated by comparison with the standard electrochemiluminescence method on a series of colorectal cancer blood samples.

Low-Fouling Substrates for Plasmonic Sensing of Circulating Biomarkers in Biological Fluids

The monitoring of biomarkers in body fluids provides valuable prognostic information regarding disease onset and progression. Most biosensing approaches use noninvasive screening tools and are conducted in order to improve early clinical diagnosis. However, biofouling of the sensing surface may disturb the quantification of circulating biomarkers in complex biological fluids. Thus, there is a great need for antifouling interfaces to be designed in order to reduce nonspecific adsorption and prevent inactivation of biological receptors and loss of sensitivity. To address these limitations and enable their application in clinical practice, a variety of plasmonic platforms have been recently developed for biomarker analysis in easily accessible biological fluids. This review presents an overview of the latest advances in the design of antifouling strategies for the detection of clinically relevant biomarkers on the basis of the characteristics of biological samples. The impact of nanoplasmonic biosensors as point-of-care devices has been examined for a wide range of biomarkers associated with cancer, inflammatory, infectious and neurodegenerative diseases. Clinical applications in readily obtainable biofluids such as blood, saliva, urine, tears and cerebrospinal and synovial fluids, covering almost the whole range of plasmonic applications, from surface plasmon resonance (SPR) to surface-enhanced Raman scattering (SERS), are also discussed.

Comparing blood versus tissue-based biomarkers expression in breast cancer patients

Molecular markers have been used as a tool for diagnostic approaches, staging, and evaluation of therapeutic responses in patients with cancer. Cancer molecular markers can also help clinicians to make decision on therapy and prognosis evaluation at the time of diagnosis. In the early diagnosis of breast cancer (BC), estrogen and progesterone receptors (ER/PR) expression levels should be determined through immunohistochemistry (IHC). In molecular genetics, there are some important tissue-based markers that can also be found in blood, such as Mammaglobin (MAM), Cytokeratin 19 (CK19), Mucin (MUC), Proto-oncogene (c-Myc), antigen Ki-67 (Ki67), and Carcinoembryonic antigen (CEA). In this study, the positive level of the marker genes in both blood and tissue of the BC patients were compared using reverse transcription polymerase chain reaction (RT-PCR) method. In addition, the importance of blood vs. tissue-based markers in BC diagnosis also demonstrated and is discussed. CEA (O), ERβ, CK19 and, c-Myc molecular markers were significantly different between blood of normal and patients while there was no significant difference of these markers in tissue samples. Blood-based biomarkers can be used for the early diagnosis of BC. Comparing blood versus tissue-based biomarkers indicated that there are correlations between markers in blood and tissue, since blood markers can be substitute to tissue markers in BC patients in the future.

Recent Progress in Optical Sensors for Biomedical Diagnostics

In recent years, several types of optical sensors have been probed for their aptitude in healthcare biosensing, making their applications in biomedical diagnostics a rapidly evolving subject. Optical sensors show versatility amongst different receptor types and even permit the integration of different detection mechanisms. Such conjugated sensing platforms facilitate the exploitation of their neoteric synergistic characteristics for sensor fabrication. This paper covers nearly 250 research articles since 2016 representing the emerging interest in rapid, reproducible and ultrasensitive assays in clinical analysis. Therefore, we present an elaborate review of biomedical diagnostics with the help of optical sensors working on varied principles such as surface plasmon resonance, localised surface plasmon resonance, evanescent wave fluorescence, bioluminescence and several others. These sensors are capable of investigating toxins, proteins, pathogens, disease biomarkers and whole cells in varied sensing media ranging from water to buffer to more complex environments such as serum, blood or urine. Hence, the recent trends discussed in this review hold enormous potential for the widespread use of optical sensors in early-stage disease prediction and point-of-care testing devices.