A dual recognition strategy for accurate detection of CTCs based on novel branched PtAuRh trimetallic nanospheres

Electrochemical cytosensors for non-invasive liquid biopsy: Detection procedures and technologies for circulating tumor cells

Each year, millions of new cancer cases and cancer-related deaths underscore the urgent need for effective, affordable screening methods. Circulating tumor cells (CTCs), which derived from tumors and shedding into bloodstream, are considered promising biomarkers for liquid biopsy due to their unique biological significance and the substantial volume of supporting research. Among many advanced CTCs detection methods, electrochemical sensing is rapidly developing due to their high selectivity, high sensitivity, low cost, and rapid detection capability, well meeting the growing demand for non-invasive liquid biopsy. This review focuses on the entire procedure of detecting CTCs using electrochemical cytosensors, starting from sample preparation, detailing bio-recognition elements for capturing CTCs, highlighting design strategies of cytosensor, and discussing the prospects and challenges of electrochemical cytosensor applications.

Recent advances in photothermal nanomaterials-mediated detection of circulating tumor cells

Photothermal materials have shown great potential for cancer detection and treatment due to their excellent photothermal effects. Circulating tumor cells (CTCs) are tumor cells that are shed from the primary tumor into the blood and metastasize. In contrast to other tumor markers that are free in the blood, CTCs are a collective term for all types of tumor cells present in the peripheral blood, a source of tumor metastasis, and clear evidence of tumor presence. CTCs detection enables early detection, diagnosis and treatment of tumors, and plays an important role in cancer prevention and treatment. This review summarizes the application of various photothermal materials in CTC detection, including gold, carbon, molybdenum, phosphorus, etc. and describes the significance of CTC detection for early tumor diagnosis and tumor prognosis. Focus is also put on how various photothermal materials play their roles in CTCs detection, including CT, imaging and photoacoustic and therapeutic roles. The physicochemical properties, shapes, and photothermal properties of various photothermal materials are discussed to improve the detection sensitivity and efficiency and to reduce the damage to normal cells. These photothermal materials are capable of converting radiant light energy into thermal energy for highly-sensitive CTCs detection and improving their photothermal properties by various methods, and have achieved good results in various experiments. The use of photothermal materials for CTCs detection is becoming more and more widespread and can be of significant help in early cancer screening and later treatment.

Hybrid chain reaction and selective recognition-based homogeneous dual-fluorescence analysis of circulating tumor cells in clinical ovarian cancer samples

BACKGROUND

Oncological analysis is important in tumor diagnosis. We constructed a dual-fluorescence and binary visual analysis system for circulating tumor cells (CTCs) using the folate receptor as a biomarker, combined with hybridization chain reaction and nanomaterial amplification. This strategy integrates terminal protection, selective recognition properties of N-methyl mesoporphyrin IX and CdTe quantum dots for Cu2+ and double-stranded templated copper nanoparticles, and inkjet printing technology.

RESULTS

In fluorescence mode, folate receptor and A2780 ovarian cancer cells were specifically detected with a limit of detection of 0.1 fg mL-1, and 10 cells mL-1 were observed. The detection limits of both the color and distance reading modes were comparable to those obtained in fluorescence mode. The applicability of the method for quantifying CTCs was validated using 27 (6 negative and 21 positive) clinical ovarian cancer samples; the results agreed with those of both the clinical folate receptor-polymerase chain reaction kit and radiological and pathological results.

SIGNIFICANCE

This dual-fluorescence and binary visual CTCs detection method provides multiple options for clinical tumor liquid biopsy.

Current research status of tumor cell biomarker detection

With the annual increases in the morbidity and mortality rates of tumors, the use of biomarkers for early diagnosis and real-time monitoring of tumor cells is of great importance. Biomarkers used for tumor cell detection in body fluids include circulating tumor cells, nucleic acids, protein markers, and extracellular vesicles. Among them, circulating tumor cells, circulating tumor DNA, and exosomes have high potential for the prediction, diagnosis, and prognosis of tumor diseases due to the large amount of valuable information on tumor characteristics and evolution; in addition, in situ monitoring of telomerase and miRNA in living cells has been the topic of extensive research to understand tumor development in real time. Various techniques, such as enzyme-linked immunosorbent assays, immunoblotting, and mass spectrometry, have been widely used for the detection of these markers. Among them, the detection of tumor cell markers in body fluids based on electrochemical biosensors and fluorescence signal analysis is highly preferred because of its high sensitivity, rapid detection and portable operation. Herein, we summarize recent research progress in the detection of tumor cell biomarkers in body fluids using electrochemical and fluorescence biosensors, outline the current research status of in situ fluorescence monitoring and the analysis of tumor markers in living cells, and discuss the technical challenges for their practical clinical application to provide a reference for the development of new tumor marker detection methods.

Electrochemical interface based on polydopamine and gold nanoparticles/reduced graphene oxide for impedimetric detection of lung cancer cells†

The use of non-invasive approaches for monitoring therapy processes in cancer patients at late stages is truly needed. In this work, we aim to develop an electrochemical interface based on polydopamine combined with gold nanoparticles and reduced graphene oxide for impedimetric detection of lung cancer cells. Gold nanoparticles (around 75 nm) were dispersed onto reduced graphene oxide material pre-electrodeposited onto disposable fluorine doped tin oxide electrodes. The coordination between gold and carbonaceous material has somehow improved the mechanical stability of this electrochemical interface. Polydopamine was later introduced onto modified electrodes via self-polymerization of dopamine in an alkaline solution. The result has demonstrated the good adhesion and biocompatibility of polydopamine towards A-549 lung cancer cells. The presence of the two conductive materials (gold nanoparticles and reduced graphene oxide) has led to a six-times decrease in charge transfer resistance of polydopamine film. Finally, the as-prepared electrochemical interface was employed for impedimetric detection of A-549 cells. The detection limit was estimated to be only 2 cells per mL. These findings have proved the possibilities to use advanced electrochemical interfaces for point-of-care applications.

Non-invasive approaches for monitoring therapy processes in cancer patients at late stages is truly needed.

Antifouling Gold-Inlaid BSA Coating for the Highly Efficient Capture of Circulating Tumor Cells

Large amounts of coexisting contamination in complex biofluid samples impede the quantified veracity of biomarkers, which is the key problem for disease confirmation. Herein, amyloid-like transformed bovine serum albumin inlaid with gold nanoparticles was used as a coating (BGC) on a substrate composed of silicon nanowires (SW; BGC-SW) under ambient conditions. After modification with the recognition group, BGC-SW could serve as an outstanding platform for the selective separation and sensitive detection of biomarkers in complicated biosamples. First, the BGC on SW with a large surface area exhibits excellent adhesion resistance. The attached amounts of contaminations in biofluids were decreased by over 78% compared with native bovine serum albumin (BSA) as the blocking agent. This is because the phase-transformed BSA coating provides stronger interactions with the SW than bare BSA, which results in a tighter attachment and more uniform coverage of the BGC. Furthermore, the gold matrix laid inside the antiadhesive coating ensures simple cross-linking with the recognition groups to selectively capture various biomarkers in complex biofluids and create a gentle release method. Circulating tumor cells (CTCs) were chosen as template biomarkers to verify the application of A-BGC-SW (BGC-SW modified with sgc8-aptamer) in various separation processes of untreated biofluids. The results showed that approximately six cells could be captured from a 1 mL fresh blood sample containing only 10 CTCs. The easy fabrication and excellent antiadhesion property endow A-BGC-SW with great potential in the field of biological separation.

New horizons in the identification of circulating tumor cells (CTCs): An emerging paradigm shift in cytosensors

Circulating tumor cells (CTCs) are cancer cells that are shed from a primary tumor into the bloodstream and function as seeds for cancer metastasis at distant locations. Enrichment and identification methods of CTCs in the blood of patients plays an important role in diagnostic assessments and personalized treatments of cancer. However, the current traditional identification methods not only impact the viability of cells, but also cannot determine the type of cancer cells when the disease is unknown. Hence, new methods to identify CTCs are urgently needed. In this context, many advanced and safe technologies have emerged to distinguish between cancer cells and blood cells, and to distinguish specific types of cancer cells. In this review, at first we have briefly discussed recent advances in technologies related to the enrichment of CTCs, which lay a good foundation for the identification of CTCs. Next, we have summarized state-of-the-art technologies to confirm whether a given cell is indeed a tumor cell and determine the type of tumor cell. Finally, the challenges for application and potential directions of the current identification methods in clinical analysis of CTCs have been discussed.

A dual-recognition-controlled electrochemical biosensor for accurate and sensitive detection of specific circulating tumor cells

Accurate and sensitive assay of specific circulating tumor cells (CTCs) is of importance for the diagnosis, treatment, and metastasis monitoring of cancer. Herein, we have proposed a dual-recognition-controlled electrochemical biosensor in this work for the detection of specific CTCs. To this sensor, two aptamer hairpin probes are designed to be able to separately bind to two adjacent proteins on the cell membrane to activate the associative toehold for strand displacement reaction, which will then trigger a dimer-like rolling cycle amplification reaction, and finally produce significantly amplified electrochemical signals for sensitive quantification of target CTCs. In our design, only the case that the two proteins are simultaneously expressed on the cell membrane can result in obvious signal responses, which may greatly improve the accuracy of CTCs analysis. The proposed biosensor can possess excellent selectivity to distinguish target cells from different cancer cells. Moreover, the combination of rolling cycle amplification and DNA nanostructure capture probes can effectively lower the detection limit to 3 cells mL^-1. Notably, our biosensor can be applied to the assay of the target CTCs in the complex whole blood matrixes, verifying its strong stability and anti-interference. Thus, the as-proposed dual-recognition-controlled electrochemical biosensor may exhibit great promise in clinical cancer diagnosis and personalized medicine.

An aptamer and flower-shaped AuPtRh nanoenzyme-based colorimetric biosensor for the detection of profenofos

A GO grafted SSM was prepared to load the freely mobile capture probe and novel flower-shaped AuPtRh nanospheres were synthesized to be a signal probe, which were constructed to form a colorimetric biosensor for the detection of profenofos.

Recent Development of Nanomaterials-Based Cytosensors for the Detection of Circulating Tumor Cells

The accurate analysis of circulating tumor cells (CTCs) holds great promise in early diagnosis and prognosis of cancers. However, the extremely low abundance of CTCs in peripheral blood samples limits the practical utility of the traditional methods for CTCs detection. Thus, novel and powerful strategies have been proposed for sensitive detection of CTCs. In particular, nanomaterials with exceptional physical and chemical properties have been used to fabricate cytosensors for amplifying the signal and enhancing the sensitivity. In this review, we summarize the recent development of nanomaterials-based optical and electrochemical analytical techniques for CTCs detection, including fluorescence, colorimetry, surface-enhanced Raman scattering, chemiluminescence, electrochemistry, electrochemiluminescence, photoelectrochemistry and so on.

Electrochemical sensing technology for liquid biopsy of circulating tumor cells-a review

In recent years, a lot of new detection techniques for circulating tumor cells (CTCs) have been developed. Among them, electrochemical sensing technology has gradually developed because of its advantages of good selectivity, high sensitivity, low cost and rapid detection. Especially in the latest decade, the field of electrochemical biosensing has witnessed great progress, thanks to the merging of biosensing research area with nanotechnology, immunotechnology, nucleic acid technology, and microfluidic technology. In this review, the recent progress for the detection of CTCs according to the principle of detection was summarized and how they can contribute to the enhanced performance of such biosensors was explained. The latest electrode construction strategies such as rolling circle amplification reaction, DNA walker and microfluidic technology and their advantages were also introduced emphatically. Moreover, the main reasonswhy the existing biosensors have not been widely used clinically and the next research points were clearly put forward.