Voltammetric aptamer based detection of HepG2 tumor cells by using an indium tin oxide electrode array and multifunctional nanoprobes

Emerging Biohybrids of Aptamer-Based Nano-Biosensing Technologies for Effective Early Cancer Detection

Cancer is a leading global cause of mortality, which underscores the imperative of early detection for improved patient outcomes. Biorecognition molecules, especially aptamers, have emerged as highly effective tools for early and accurate cancer cell identification. Aptamers, with superior versatility in synthesis and modification, offer enhanced binding specificity and stability compared with conventional antibodies. Hence, this article reviews diagnostic strategies employing aptamer-based biohybrid nano-biosensing technologies, focusing on their utility in detecting cancer biomarkers and abnormal cells. Recent developments include the synthesis of nano-aptamers using diverse nanomaterials, such as metallic nanoparticles, metal oxide nanoparticles, carbon-derived substances, and biohybrid nanostructures. The integration of these nanomaterials with aptamers significantly enhances sensitivity and specificity, promising innovative and efficient approaches for cancer diagnosis. This convergence of nanotechnology with aptamer research holds the potential to revolutionize cancer treatment through rapid, accurate, and non-invasive diagnostic methods.

Label-free electrochemical aptasensor for the detection of HepG2 hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common liver malignancy and is characterized by increasing incidence and high mortality rates. Current methods for the screening and diagnosis of HCC exhibit inherent limitations, highlighting the ever-growing need for the development of new methods for the early diagnosis of HCC. The aim of this work was to develop a novel electrochemical aptasensor for the detection of HepG2 cells, a type of circulating tumor cells that can be used as biomarkers for the early detection of HCC. A carbon screen-printed electrode was functionalized with a composite suspension containing graphene oxide, chitosan, and polyaniline nanoparticles to increase the electrode surface and provide anchoring sites for the HepG2 cell-specific aptamer. The aptamer was immobilized on the surface of the functionalized electrode using multipulse amperometry, an innovative technique that significantly reduces the time required for aptamer immobilization. The innovative platform was successfully employed for the first time for the amplification-free detection of HepG2 cells in a linear range from 10 to 200,000 cells/mL, with a limit of detection of 10 cells/mL. The platform demonstrated high selectivity and stability and was successfully used for the detection of HepG2 cells in spiked human serum samples with excellent recoveries.

Highly Sensitive Zinc Oxide Fiber-Optic Biosensor for the Detection of CD44 Protein

Currently, significant progress is being made in the prevention, treatment and prognosis of many types of cancer, using biological markers to assess current physiological processes in the body, including risk assessment, differential diagnosis, screening, treatment determination and monitoring of disease progression. The interaction of protein coding gene CD44 with the corresponding ligands promotes the processes of invasion and migration in metastases. The study of new and rapid methods for the quantitative determination of the CD44 protein is essential for timely diagnosis and therapy. Current methods for detecting this protein use labeled assay reagents and are time consuming. In this paper, a fiber-optic biosensor with a spherical tip coated with a thin layer of zinc oxide (ZnO) with a thickness of 100 nm, deposited using a low-cost sol-gel method, is developed to measure the CD44 protein in the range from 100 aM to 100 nM. This sensor is easy to manufacture, has a good response to the protein change with detection limit of 0.8 fM, and has high sensitivity to the changes in the refractive index (RI) of the environment. In addition, this work demonstrates the possibility of achieving sensor regeneration without damage to the functionalized surface. The sensitivity of the obtained sensor was tested in relation to the concentration of the control protein, as well as without antibodies-CD44.

Carbon Nano-Onion-Decorated ZnO Composite-Based Enzyme-Less Electrochemical Biosensing Approach for Glucose

This study investigates the enzyme-less biosensing property of the zinc oxide/carbon nano-onion (ZnO/CNO) nanocomposite coated on a glassy carbon electrode. The ZnO/CNO nanocomposite was synthesized using the ex situ mixing method, and the structural characterization was done using XRD, SEM, and TEM, whereas functional groups and optical characterization were done through FTIR and UV-visible spectroscopy. The electrochemical sensing response of the ZnO/CNO nanocomposite for the linear range of glucose concentration (0.1-15 mM) was examined using cyclic voltammetry (CV) with a potential window of -1.6 to +1.6 V using 0.1 M NaOH as an electrolyte. The ZnO/CNO nanocomposites showed enhanced sensing ability toward glucose with a sensitive value of 606.64 μA/mM cm². Amperometric i-t measurement supports the finding of CV measurement and showed good sensing ability of the electrode ZnO/CNO nanocomposite material for up to 40 days. The enhanced electrocatalytic activity of the ZnO/CNO nanocomposite is explained due to the synergetic effect of both ZnO and CNO. Our findings suggest a high potential for ZnO/CNO nanocomposite-based glucose biosensors, which could be further utilized to develop noninvasive skin-attached sensors for biomedical applications.

Aptamers and New Bioreceptors for the Electrochemical Detection of Biomarkers Expressed in Hepatocellular Carcinoma

Hepatocellular carcinoma is a malignancy associated with high mortality and increasing incidence. Early detection of this disease could help increase survival and overall patient benefit. Non-invasive strategies for the diagnosis of this medical condition are of utmost importance. In this scope, the detection of hepatocellular carcinoma biomarkers could provide a useful diagnostic tool. Aptamers represent as short, single-stranded DNAs or RNAs that can specifically bind selected analytes, and also as pseudo-biorecognition elements that can be employed for electrode functionalization. Also, other types of DNA sequences can be used for the construction of DNA-based biosensors applied for the quantification of hepatocellular carcinoma biomarkers. Herein, we will be analyzing recent examples of aptasensors and DNA biosensors for the detection of hepatocellular carcinoma biomarkers like micro-RNAs, long non-coding RNAs, exosomes, circulating tumor cells and proteins. The literature data is discussed comparatively in a critical manner highlighting the advantages of using electrochemical biosensors in diagnosis, as well as the use of nanomaterials and biocomponents in the functionalization of electrodes for improved sensitivity and selectivity.

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 Sensors for Detection of Markers on Tumor Cells

In recent years, the increasing incidence and mortality of cancer have inspired the development of accurate and rapid early diagnosis methods in order to successfully cure cancer; however, conventional methods used for detecting tumor cells, including histopathological and immunological methods, often involve complex operation processes, high analytical costs, and high false positive rates, in addition to requiring experienced personnel. With the rapid emergence of sensing techniques, electrochemical cytosensors have attracted wide attention in the field of tumor cell detection because of their advantages, such as their high sensitivity, simple equipment, and low cost. These cytosensors are not only able to differentiate tumor cells from normal cells, but can also allow targeted protein detection of tumor cells. In this review, the research achievements of various electrochemical cytosensors for tumor cell detection reported in the past five years are reviewed, including the structures, detection ranges, and detection limits of the cytosensors. Certain trends and prospects related to the electrochemical cytosensors are also discussed.

Electrochemical aptasensors for the detection of hepatocellular carcinoma-related biomarkers

Recent progress in electrochemical aptasensors for the detection of HCC-related biomarkers, including cancer cells, proteins, cell-derived exosomes, and nucleic acids, is reviewed.

Magnetic bead-based electrochemical and colorimetric assays of circulating tumor cells with boronic acid derivatives as the recognition elements and signal probes

Simple, sensitive and rapid detection of circulating tumor cells (CTCs) is of great importance for early diagnosis and therapy of cancers. Overexpression of sugar units on cell surface is related to the phenotypes of many cancers. Based on the boronate ester interaction, we reported the electrochemical and colorimetric detection of CTCs with high simplicity and sensitivity. Specifically, ferroceneboronic acid (FcBA) can be measured by differential pulse voltammetry and 4-mercaptophenylboronic acid (MPBA) can induce the aggregation and color change of gold nanoparticles (AuNPs). CTCs captured by the aptamer-modified magnetic beads (Apt-MBs) can sequestrate FcBA or MPBA molecules by the formation of boronate ester bonds, thus leading to the decrease in the electrochemical signal of FcBA or preventing the MPBA-triggered aggregation of AuNPs. Due to the overexpression of sugar groups on the surface of CTCs, the amplification-free methods exhibited high sensitivity and obviated the use of additional antibody or aptamer for the recognition of captured cells. With MCF-7 cancer cell as the model, 50 cells can be readily determined by the electrochemical and colorimetric methods. The proposed strategy is valuable for probing of cell glycosylation and designing of novel sensing devices for detection of sugar-containing biological macromolecules and cells.

Recognition and sensitive detection of CTCs using a controllable label-free electrochemical cytosensor

An excellent atomic layer deposition (ALD) method was adopted for the controllable systhesis of a xFe₂O₃-nPt (or nPt-xFe₂O₃)-coated graphene nanostructure (xFe₂O₃-nPt@graphene). The produced nanomaterials have been characterized by transmission electron microscopy (TEM), cyclic voltammetry (CV), and X-ray photoelectron spectroscopy (XPS). It is shown that xFe₂O₃ and nPt were effectively tailored and deposited on the graphene. A simple, rapid, and sensitive electrochemical cytosensor based on the controllable nanomaterials was successfully developed for MCF-7 cells detection by combining the high affinity and specificity of an aptamer. The prepared cytosensor displays a linear response to MCF-7 in the concentration range 18 to 1.5 × 10⁶ cell mL^-1 with the detection limit of 6 cell mL^-1 (at an S/N of 3). This cytosensor was applied to detect circulating tumor cells (CTCs) in patient blood and the results were satisfied. The experimental results indicate that the proposed controllable electrochemical cytosensor is highly-sensitive, and convenient for clinical detection of breast CTCs. Graphical abstract.

PdIrBP mesoporous nanospheres combined with superconductive carbon black for the electrochemical determination and collection of circulating tumor cells

An integrated electrochemical immunoassay is described for the determination of circulating tumor cells (CTCs). For the first time, Ketjen black (KB), which is a superconductive carbon material, was incorporated with Au nanoparticles (AuNPs) and used to modify the surface of gold electrodes. A cocktail of anti-epithelial cell adhesion molecules (EpCAM) and anti-vimentin antibodies was chosen to capture the CTCs. Palladium-iridium-boron-phosphorus alloy-modified mesoporous nanospheres (PdIrBPMNS) served as a catalytic tag to amplify the current signal. Glycine-HCl (Gly-HCl) was used as an antibody eluent to release and collect the captured CTCs from the electrodes for further clinical research without compromising cell viability. The response of the method increased linearly from 10 to 1 × 10⁶ cells mL^-1 CTCs, while the detection limit was calculated to be as low as 2 cells mL^-1. This method was successfully used to determine CTCs in spiked blood samples and demonstrated good recovery. Graphical abstractKetjen black/AuNPs was incorporated in the electrochemical platform to enhance the electron transfer ability of the electrode surface. PdIrBP mesoporous nanospheres were used to amplify DPV signal in this assay. The introduction of Gly-HCl realized nondestructive recovery of circulating tumor cells.

Aptamer-based electrochemical cytosensors for tumor cell detection in cancer diagnosis: A review

Circulating tumor cells, a type of viable cancer cell circulating from primary or metastatic tumors in the blood stream, can lead to the parallel development of primary tumors and metastatic lesions. Highly selective and sensitive detection of tumor cells has become a hot research topic and can provide a basis for early diagnosis of cancers and anticancer drug evaluation to develop the best treatment plan. Aptamers are single-stranded oligonucleotides that can bind to target tumor cells in unique three-dimensional structures with high specificity and affinity. Aptamer-based methods or signal amplification methods using aptamers show great potential in improving the selectivity and sensitivity of electrochemical (EC) cytosensors for tumor cell detection. This review covers the remarkable developments in aptamer-based EC cytosensors for the identification of cell type, cell counting and detection of crucial proteins on the cell surface. Various EC techniques have been developed for cancer cell detection, including common voltammetry or impedance, electrochemiluminescence and photoelectrochemistry in a direct approach (aptamer-target cell), sandwich approach (capture probe-target cell-signaling probe) or other approach. The current challenges and promising opportunities in the establishment of EC aptamer cytosensors for tumor cell detection are also discussed.

DNA nanotetrahedron linked dual-aptamer based voltammetric aptasensor for cardiac troponin I using a magnetic metal-organic framework as a label

An ultrasensitive voltammetric aptasensor was constructed to analyze cardiac troponin I (cTnI). It is based on DNA nanotetrahedron (NTH) linked dual-aptamer (dAPT) and magnetic metal organic frameworks (mMOFs) of type Fe₃O₄@UiO-66. Firstly, the DNA NTH linked dAPT (Tro4 and Tro6) were immobilized on a gold electrode for improving the capture efficiency of cTnI. The novel mMOFs Fe₃O₄@UiO-66 was then decorated by Au@Pt nanoparticles (Au@PtNPs), horseradish peroxidase (HRP), G-quadruplex/hemin (GQH) DNAzyme, and two types of aptamers to form signaling nanoprobes. In the presence of cTnI, an aptamer-protein-nanoprobe sandwich-type structure is formed. Afterward, the nanoprobes including enzyme, GQH DNAzyme and Fe₃O₄@UiO-66/Au@PtNP were utilized to catalyze the oxidation of hydroquinone by hydrogen peroxide for the electrochemical signals amplification, typically at a working potential of -0.1 V (vs. Ag/AgCl). The voltammetric signal increases linearly in the 0.01 to 100 ng·mL^-1 cTnI concentration range, and the detection limit is 5.7 pg·mL^-1. Graphical abstract An ultrasensitive voltammetric aptasensor was constructed to analyze cardiac troponin I (cTnI) based on DNA nanotetrahedron linked dual-aptamer and magnetic metal organic frameworks of type Fe₃O₄@UiO-66. The results indicated the aptasensor has a wide linear response range (0.01 to 100 ng/mL) and low detection limit (5.74 pg/mL) for cTnI. GE: gold electrode; MCH: 6-Mmercapto-1-hexanol; HRP: horseradish peroxidase; HQ: hydroquinone; BQ: benzoquinone.

An ultrasensitive electrochemical cytosensor for highly specific detection of HL-60 cancer cells based on metal ion functionalized titanium phosphate nanospheres

Facile and sensitive detection methods of cancer cells in the early stage are beneficial for monitoring cancers and treating patients in time to reduce the death rate. In this work, an ultrasensitive cytosensor was constructed using aptamers as cell capturers and metal ion-exchanged titanium phosphate nanospheres as electrochemical probes. KH1C12 can specifically recognize HL-60 cells and distinguish them from other cell lines, K562 and CCRF-CEM, to obtain high selectivity. Cadmium ion functionalized titanium phosphate nanospheres show large quantities of electroactive cadmium ion output and a highly sensitive electrochemical signal. This proposed cytosensor showed a wide dynamic linear range from 102 cells per mL to 107 cells per mL with a low detection limit of 35 cells per mL, providing a new, simple and ultrasensitive platform for cancer diagnosis in biomedical and clinical research.

Label-free cytosensing of cancer cells based on the interaction between protein and an electron-transfer carbohydrate-mimetic peptide

We used an electron-transfer carbohydrate-mimetic peptide (YYYYC) to construct an electrochemical cytosensing system. Magnetic beads were modified with either asialofetuin (ASF) or soybean agglutinin (SBA) to evaluate the effect on cell sensing. Because SBA binds to the galactose residue that exists at the terminals of the carbohydrate chains in ASF, the target protein was accumulated on the protein magnetic beads. SBA is an example of N-acetylgalactosamine- and galactose-binding proteins that readily combine with YYYYC. When the peptides and protein-immobilized beads competed for a target protein, the peak current of the peptides changed according to the concentration of the protein at the 10^-12 M level. Next, human myeloid leukemia cells (K562 cell) were measured using the peptide and the carbohydrate chains on the cell surface that recognize SBA. The electrode response was linear to the number of K562 cells and ranged from 1.0 × 10² to 5.0 × 10³ cells mL^-1. In addition, detection of a human liver cancer cell (HepG2 cell) was carried out using interactions with the peptide, the ASF receptors in HepG2 cells, and the carbohydrate chains of ASF. The peak currents were proportional and ranged between 5.0 × 10¹ and 1.5 × 10³ cells mL^-1. When the values estimated from an electrochemical process were compared with those obtained by ELISA, the results were within the acceptable range of measurement error.

A DNA nanostructured aptasensor for the sensitive electrochemical detection of HepG2 cells based on multibranched hybridization chain reaction amplification strategy

Sensitive detection of cancer cells is beneficial to the early diagnosis of cancer and individual treatment. In the present study, a DNA nanostructured aptasensor was used for the sensitive electrochemical detection of human liver hepatocellular carcinoma cells (HepG2) based on multibranched hybridization chain reaction amplification strategy. We established a well-designed platform by immobilizing DNA tetrahedron, a three-dimensional DNA nanostructure, on the gold electrode to capture HepG2 cells more specifically and efficiently. Meanwhile, functional hybrid nanoprobes consisted of MIL-101@AuNPs (Au nanoparticles), numerous hemin/G-quadruplex DNAzyme from multibranched hybridization chain reaction, and natural horseradish peroxidase (HRP) was designed. The hybrid nanoprobes possessed the functions of specific discernment and enzymatic signal amplification simultaneously. With the help of nanoprobes, HepG2 cells were recognized and captured to form a DNA tetrahedron-cell-nanoprobe sandwich-like structure on the electrode surface. The lower detection limit of this established cytosensor is 5 cells per ml. Moreover, it delivered a broad detection range from 10² to 10⁷ cells per ml. The results revealed that the as-proposed cytosensor may be utilized as a powerful tool for early diagnosis of cancer in the future.

Aptamer: A potential oligonucleotide nanomedicine in the diagnosis and treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common cancers with a high mortality rate. Late diagnosis and poor prognosis are still a major drawback since curative therapies such as liver resection and liver transplantation are effective only for an early stage HCC. Development of novel molecular targeting therapies against HCC may provide new options that will improve the efficiency of the diagnosis and the success of the therapy, thus ameliorating the life expectancy of the patients. The aptamer is an oligonucleotide nanomedicine that has high binding affinity and specificity to small and large target molecules in the intracellular and extracellular environment with agonist or antagonist function. Currently, several aptamers for diagnostic and therapeutic purposes are under development to recognize different molecules of HCC. In in vitro models, the aptamer has been shown to be able to reduce the growth of HCC cells and increase the sensitivity to conventional chemotherapies. In in vivo mouse models, aptamer could induce cell apoptosis with antitumor activity. Overall data had shown that aptamer has limited toxicity and might be safe in clinical application. This review summarizes recent information of aptamer as a potential oligonucleotide nanomedicine tool, in diagnostics, targeted therapy, and as drug delivery nano-vehicles.