A cytosensor based on NiO nanoparticle-enhanced surface plasmon resonance for detection of the breast cancer cell line MCF-7

Ferula latisecta gels for synthesis of zinc/silver binary nanoparticles: antibacterial effects against gram-negative and gram-positive bacteria and physicochemical characteristics

This study explores the potential antibacterial applications of zinc oxide nanoparticles (ZnO NPs) enhanced with silver (Ag) using plant gel (ZnO-AgO NPs). The problem addressed is the increasing prevalence of pathogenic bacteria and the need for new, effective antimicrobial agents. ZnO NPs possess distinctive physicochemical properties that enable them to selectively target bacterial cells. Their small size and high surface area-to-volume ratio allow efficient cellular uptake and interaction with bacterial cells. In this study, the average size of the synthesized ZnO-Ag nanoparticles was 77.1 nm, with a significant standard deviation of 33.7 nm, indicating a wide size distribution. The nanoparticles demonstrated remarkable antibacterial efficacy against gram-negative and gram-positive bacteria, with inhibition zones of 14.33 mm for E. coli and 15.66 mm for B. subtilis at a concentration of 300 µg/ml. Minimum inhibitory concentrations (MIC) were determined to be 100 µg/ml for E. coli and 75 µg/ml for S. saprophyticus. Additionally, ZnO-Ag NPs exhibited excellent biocompatibility, making them appropriate for various pharmacological uses. This study utilizes Ferula latisecta gels, offering a sustainable and eco-friendly approach to nanoparticle synthesis. Incorporating of Ag into ZnO NPs significantly enhances their antimicrobial properties, with the combined results showing great inhibition effects on pathogenic microbes. The findings suggest that ZnO-Ag NPs could be a promising candidate for addressing the challenges posed by drug-resistant bacterial infections and enhancing antimicrobial treatments.

Silver nanoparticles-based localized surface plasmon resonance biosensor for Escherichia coli detection

Escherichia coli (E. coli) bacteria with varying solution concentrations have been successfully detected using silver nanoparticles (Ag NPs)-based localized surface plasmon resonance (LSPR) biosensors. The Ag NPs were effectively synthesized by a chemical method using trisodium citrate with L-Histidine (L-His) and deposited on the surface of Au thin film-coated half-cylinder BK-7 prisms. He-Ne laser with a wavelength of 632.8 nm was used to generate LSPR phenomena in Kretschmann configuration with prism/Au thin film/His-Ag NPs/E. coli bacteria/air structure arrangements. The variation of E. coli bacteria concentration was carried out to determine the effect of E. coli bacteria concentration on the LSPR curve characteristics. The characterization results showed that the size of Ag NPs was 18.7 nm, and that of His-Ag NPs was 17.9 nm. Selected area electron diffraction results indicated the formation of diffraction rings with the presence of lattice planes (111), (200), (220), and (311), proving the face-centered cubic crystal structure of silver. The absorbance peak of Ag NPs shifted from a wavelength of 421-414 nm with an increase in band gap energy from 2.94 eV to 2.99 eV, along with a decreased average particle size. The functional groups observed in His-Ag NPs showed wavenumbers at 3320 to 3318 cm-1, 2106 to 2129 cm-1, and 1635 cm-1, showing the OH, CH, and C CO bonds, respectively. The SPR angle of the prism/Au thin film/air structure is 44.80°. Meanwhile, the LSPR angle for the prism/Au thin film/His-Ag NPs/air structure is 44.92°. There is an increase in the LSPR angle by 0.12°. Moreover, the minimum reflectance increases by 0.02. After detecting E. coli bacteria, the LSPR angle shifted by 0.26°, 0.38°, and 0.49° for concentrations of 6.0 × 108 CFU/mL, 6.0 × 107 CFU/mL and 6.0 × 106 CFU/mL respectively. However, the minimum reflectance rose from 0.09° to 0.14°, 0.20°, and 0.22°. Moreover, SPR testing with the structure of the prism/Au thin film/E. coli bacteria/air was carried out to determine the contribution of His-Ag NPs for detecting E. coli bacteria. The results showed that no angular shift occurs. These results indicate that using Ag NPs encapsulated with L-His is essential in amplifying the SPR signal and detecting E. coli bacteria. There was a notable alteration in both the LSPR angle and minimum reflectance indicating that adding His-Ag NPs facilitated the interaction between the E. coli and the sensor surface, thereby enhancing the performance of LSPR-based sensors for E. coli detection for low limit of detection value at 0.47 CFU/mL.

Facile preparation of a cost-effective platform based on ZnFe2O4 nanomaterials for electrochemical cell detection

Circulating tumor cells (CTCs) are important tumor markers that indicate early metastasis, tumor recurrence, and treatment efficacy. To identify and separate these cells from the blood, new nanomaterials need to be developed. The present study explored the potential application of ZnFe₂O₄ magnetic nanoparticles in capturing CTCs with cell surface markers. Folic acid was coupled to L-cysteine-capped ZnFe₂O₄ nanoparticles (ZC) to provide binding sites on ZnFe₂O₄ nanoparticles for the recognition of folate bioreceptors, which are highly expressed in MCF-7 breast cancer cells. The cytotoxicity of ZnFe₂O₄ nanoparticles and ZC against MCF-7 was analyzed with the MTT assay. After 24 h of incubation, there were IC50 values of 702.6 and 805.5 µg/mL for ZnFe₂O₄ and ZC, respectively. However, after 48 h of incubation, IC50 values of ZnFe₂O₄ and ZC were reduced to 267.3 and 389.7 µg/mL, respectively. The cell quantification was conducted with magnetically collected cells placed on a glassy carbon electrode, and the differential pulse voltammetry (DPV) responses were analyzed. This cost-effective ZnFe₂O₄-based biosensing platform allowed cancer cell detection with a limit of detection of 3 cells/mL, ranging from 25 to 10⁴ cells/mL. In future, these functionalized zinc ferrites may be used in electrochemical cell detection and targeted cancer therapy.

Isolation, Detection and Analysis of Circulating Tumour Cells: A Nanotechnological Bioscope

Cancer is one of the dreaded diseases to which a sizeable proportion of the population succumbs every year. Despite the tremendous growth of the health sector, spanning diagnostics to treatment, early diagnosis is still in its infancy. In this regard, circulating tumour cells (CTCs) have of late grabbed the attention of researchers in the detection of metastasis and there has been a huge surge in the surrounding research activities. Acting as a biomarker, CTCs prove beneficial in a variety of aspects. Nanomaterial-based strategies have been devised to have a tremendous impact on the early and rapid examination of tumor cells. This review provides a panoramic overview of the different nanotechnological methodologies employed along with the pharmaceutical purview of cancer. Initiating from fundamentals, the recent nanotechnological developments toward the detection, isolation, and analysis of CTCs are comprehensively delineated. The review also includes state-of-the-art implementations of nanotechnological advances in the enumeration of CTCs, along with future challenges and recommendations thereof.

Real-Time Detection of Circulating Tumor Cells in Bloodstream Using Plasmonic Fiber Sensors

Circulating tumor cells (CTCs) are single cancer cells or cancer cell clusters that are present in the circulatory system. Assessing CTC levels in patients can aid in the early detection of cancer metastasis and is essential for the purposes of accurate cancer prognosis. However, current in vitro blood tests are limited by the insufficient blood samples and low concentration levels of CTCs, which presents a major challenge for practical biosensing devices. In this work, we propose the first surface plasmon resonance (SPR) fiber probe to work intravenously, which offers a real-time detection of CTCs in bloodstreams. By exposing the protein-functionalized fiber probe to circulating blood, a continuous capture of CTCs ensures a constant increase in enrichment and hence greatly enhances enumeration accuracy. The performance of our plasmonic fiber probe was demonstrated to specifically detect Michigan Cancer Foundation-7 (MCF-7) breast cancer cells in flowing whole mouse blood. Further, a detection limit of ~1.4 cells per microliter was achieved by using an epithelial cell adhesion molecule (EpCAM) antibody-based receptor layer and a 15 minute enrichment period. This pilot study validates real-time CTC detection directly in the bloodstream by using plasmonic fiber probes, which exhibit promising clinical potential for in vivo diagnostic tests involving low concentration biomarkers in circulating blood.

Construction of Aptamer-Based Nanobiosensor for Breast Cancer Biomarkers Detection Utilizing g-C3N4/Magnetic Nano-Structure

An electrochemical aptasensor has been developed to determine breast cancer biomarkers (CA 15-3). Aptamer chains were immobilized on the surface of the electrode by g-C₃N₄/Fe₃O₄ nanoparticles, which increased the conductivity and active surface area of the electrode. X-ray diffraction analysis (XRD), Fourier-transformed infrared spectroscopy (FTIR), and transmission electron microscopy (TEM) measurements have been carried out to characterize the nanomaterials. Cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy have been used to characterize the developed electrode. The results demonstrate that the modified electrode has better selectivity for CA 15-3 compared to other biological molecules. It has a good electrochemical response to CA 15-3 with a detection limit of 0.2 UmL^-1 and a linear response between 1 and 9 UmL^-1. It has been used as a label-free sensor in potassium ferrocyanide medium and as methylene blue-labeled in phosphate buffer medium. This electrode was successfully applied to analyze the serum of diseased and healthy individuals, which corroborates its high potential for biosensing applications, especially for the diagnosis of breast cancer.

Optical cytosensors for the detection of circulating tumour cells

Blood analysis is an established approach to monitor various diseases, ranging from heart defects and diabetes to cancer. Among various tumor markers in the blood, circulating tumor cells (CTCs) have received increasing attention due to the fact that they originate directly from the tumors. Capturing and detecting CTCs represents a promising approach in cancer diagnostics and clinical management of cancers. CTCs in blood progress to self-seeding a tumour or initiating a new lesion mass. Cytosensors are biosensors intended to identify CTCs in a blood sample of cancer patients and provide information about the cancer status. Herein, we firstly discuss different detection methods of state-of-the-art optical cytosensors, including colorimetry, fluorescence, surface plasmon resonance, photoelectrochemistry and electrochemiluminescence. Then we review the significant advances made in implementing biorecognition elements and nanomaterials for the detection of cancer cells. Despite great progress in optical cytosensors, and their integration with smartphones, they have still only been explored to prototype stages. Much more effort is needed to fulfil their potential in modern cancer diagnostics and in monitoring the state of disease for cancer patients.

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.

Insights on the emerging biotechnology of histidine-rich peptides

In the late 70's, the discovery of the restriction enzymes made possible the biological production of functional proteins by recombinant DNA technologies, a fact that largely empowered both biotechnological and pharmaceutical industries. Short peptides or small protein domains, with specific molecular affinities, were developed as purification tags in downstream processes to separate the target protein from the culture media or cell debris, upon breaking the producing cells. Among these tags, and by exploiting the interactivity of the imidazole ring of histidine residues, the hexahistidine peptide (H6) became a gold standard. Although initially used almost exclusively in protein production, H6 and related His-rich peptides are progressively proving a broad applicability in novel utilities including enzymatic processes, advanced drug delivery systems and diagnosis, through a so far unsuspected adaptation of their binding capabilities. In this context, the coordination of histidine residues and metals confers intriguing functionalities to His-rich sequences useable in the forward-thinking design of protein-based nano- and micro-materials and devices, through strategies that are comprehensively presented here.

Multifunctional nanoparticles as optical biosensing probe for breast cancer detection: A review

Optical biosensors show attractive performance in medical sensing in the event of using different nanoparticles in their design. Owing to their unique optical characteristics and biological compatibility, gold nanoparticles (GNPs), silver nanoparticles (AgNPs), bimetallic nanoparticles and magnetic nanoparticles have been broadly implemented in making sensing tools. The functionalization of these nanoparticles with different components provides an excellent opportunity to assemble selective and sensitive sensing materials to detect various biological molecules related to breast cancer. This review summarizes the recent application of optical biosensing devices based on nanomaterials and discusses their pros and cons to improve breast cancer detection in real samples. In particular, the main constituent elements of these optical biosensors including recognition and transducer elements, types of applied nanostructures, analytical sensing procedures, sensor detection ranges and limit of detection (LOD), are expressed in detail.

Recent advances in functionalization of plasmonic nanostructures for optical sensing

This review summarizes the progress that has been made in the use of nanostructured SPR-based chemical sensors and biosensors. Following an introduction into the field, a first large section covers principles of nanomaterial-based SPR sensing, mainly on methods using noble metal nanoparticles (spheres, cubes, triangular plates, etc.). The next section covers methods for functionalization of plasmonic nanostructures, with subsections on functionalization using (a) amino acids and proteins; (b) oligonucleotides, (c) organic polymers, and (d) organic compounds. Several tables are presented that give an overview on the wealth of methods and materials published. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. This review is not intended to be a comprehensive compilation of the literature in the field but rather is a systematic overview of the state of the art in surface chemistry of plasmonic nanostructures. The ability of various ligands and receptors for functionalization of nanoparticles as well as their sensing capability is discussed.

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.

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.

Bioconjugated gold nanoparticles as an efficient colorimetric sensor for cancer diagnostics

The chances of curing and reducing the adverse effect of cancer partly lie in early detection. Colorimetric sensor-based technique show promising results since the target is detected with high sensitivity but without the use of advanced/costly techniques through a simple visual color change. In most cases, gold nanoparticles (Au Nps) functionalized with biomolecules complementary to target analyte are used for colorimetric detection. The interaction of functionalized Au Nps with target analytes induce aggregation or dispersion where the color of the solution changes from red to blue or blue to red respectively, which can be visualized by the naked eyes. Such a facile technique has a high commercial viability and therefore, understanding its concept is essential. Here, some of the reported studies are discussed technically for better understanding about the invitro colorimetric detection of cancer.

Construction of Tb-MOF-on-Fe-MOF conjugate as a novel platform for ultrasensitive detection of carbohydrate antigen 125 and living cancer cells

Combining different metal-organic frameworks (MOFs) into a conjugate material can integrate the properties of each MOF component and further lead to emergent properties from the synergistic heterostructured units. In this work, two kinds of bimetallic TbFe-MOFs have been designed by MOF-on-MOF strategy and utilized as a platform for anchoring carbohydrate antigen 125 (CA125) aptamer to detect CA125 and living michigan cancer foundation-7 (MCF-7) cells. Although the integrated MOF-on-MOF architectures show similar chemical and structural features to that of the top layer, the Fe-MOF-on-Tb-MOF and Tb-MOF-on-Fe-MOF have different surface nanostructures to their parent MOFs. The developed aptasensor based on Tb-MOF-on-Fe-MOF displays higher stability of the formed G-quadruplex between aptamer and CA125 than that based on Fe-MOF-on-Tb-MOF, owing to stronger immobilization behavior of the aptamer for the Tb-MOF-on-Fe-MOF composite. The developed aptasensor provides an extremely low detection limit of 58 μU·mL^-1 towards CA125 within a wide linear range from 100 μU·mL^-1 to 200 U·mL^-1, which is significantly lower than those of all reported sensors. This aptasensor also has high selectivity, good stability, acceptable reproducibility, and excellent applicability in human serum. Moreover, the Tb-MOF-on-Fe-MOF nanoarchitecture demonstrates superior biocompatibility and good endocytosis. As a result, the developed aptasensor illustrates high sensitivity for detection of MCF-7 cells with an extremely low detection limit of 19 cell·mL^-1. Therefore, the proposed aptasensor based on Tb-MOF-on-Fe-MOF exhibits great potentials for early diagnosis of tumors.

Electrochemical Aptasensor for Ultralow Fouling Cancer Cell Quantification in Complex Biological Media Based on Designed Branched Peptides

The rapid, convenient, and selective assaying of clinical targets directly in complex biological media brings with it the potential to revolutionize diagnostics. One major hurdle to impact is retention of selectivity and a tight control of nonspecific surface interactions or biofouling. We report herein, the construction of an antifouling interface through the covalent attachment of designed branched zwitterionic peptides onto electrodeposited polyaniline film. The antifouling capability of the designed branched peptide significantly outperforms that of the commonly used PEG and linear peptides. The interfaces modified with branched peptides are exceptionally effective in reducing a nonspecific protein and cell adsorption, as verified by electrochemical and fluorescent characterization. The derived sensors with mucin1 protein (MUC1) aptamer as the recognition element detect MUC1-positive MCF-7 breast cancer cells in human serum with high sensitivity and selectivity. The linear response range of the cytosensor for the MCF-7 cell is from 50 to 10⁶ cells/mL, with a limit of detection as low as 20 cells/mL. More importantly, the assaying performances remain unchanged in human serum owing to the presence of branched antifouling peptide, indicating feasibility of the cytosensor for practical cancer cell quantification in complex samples.

Aptasensors as a new sensing technology developed for the detection of MUC1 mucin: A review

Mucin 1 protein (MUC1) is a membrane-associated glycoprotein overexpressed in the majority of human malignancies and considered as a predominant protein biomarker in cancers. Owing to the crucial role of MUC1 in cancer dissemination and metastasis, detection and quantification of this biomarker is of great importance in clinical diagnostics. Today, there exist a wide variety of strategies for the determination of various types of disease biomarkers, especially MUC1. In this regard, aptamers, as artificial single-stranded DNA or RNA oligonucleotides with catalytic and receptor properties, have drawn lots of attention for the development of biosensing platforms. So far, various sensitivity-enhancement techniques in combination with a broad range of smart nanomaterials have integrated into the design of novel aptamer-based biosensors (aptasensors) to improve detection limit and sensitivity of analyte determination. This review article provides a brief classification and description of the research progresses of aptamer-based biosensors and nanobiosensors for the detection and quantitative determination of MUC1 based on optical and electrochemical platforms.

Ratiometric Electrogenerated Chemiluminescence Cytosensor Based on Conducting Polymer Hydrogel Loaded with Internal Standard Molecules

A sensitive and reliable bimodal electrochemiluminescent (ECL) system based on CdTe quantum dots (QDs) and luminol as double luminophores is constructed. CdTe QDs tagged with the aptamer (CdTe-Apt 2) of cancer cells are used as the detection signals, while luminol molecules are used as internal standards. The electrodeposited polyaniline-based conducting polymer hydrogel (CPH) on the electrode surfaces improves the biocompatibility and conductivity of the sensing interfaces effectively. Furthermore, electron transfer is probably much easier when luminol and coreactant potassium persulfate (K₂S₂O₈) are immobilized in the CPH in comparison to that in solution. Cancer cells are captured to the electrode surface by another aptamer linked to the Au nanoparticles immobilized in the CPH through Au-S bonds. In the developed bimodal ECL system, an internal standard method is used to quantify cancer cells by comparing the differences in sensitivity of the double-peak ECL signals with that of target analytes. The internal standard method of ECL strategy can provide very accurate detection results in a complex environment because interferences in the system can be eliminated through the self-calibration of two emission spectra. A linear relation is found on the basis of a plot of the ΔECL_CdTe/ΔECL_luminol against the concentration of cancer cells within 100-6500 cells mL^-1 under optimized conditions. The developed ratiometric ECL cytosensor with internal standard can significantly improve the accuracy and reliability of cell assays in complex biological media, demonstrating promising applications in healthcare monitoring and clinical diagnostics.

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.

Dual-aptamer based electrochemical sandwich biosensor for MCF-7 human breast cancer cells using silver nanoparticle labels and a poly(glutamic acid)/MWNT nanocomposite

This paper reports on a sensitive and selective method for the detection of Michigan Cancer Foundation-7 (MCF-7) human breast cancer cells and MUC1 biomarker by using an aptamer-based sandwich assay. A biocompatible nanocomposite consisting of multiwall carbon nanotubes (MWCNT) and poly(glutamic acid) is placed on a glassy carbon electrode (GCE). The sandwich assay relies on the use of a mucin 1 (MUC1)-binding aptamer that is first immobilized on the surface of modified GCE. Another aptamer (labeled with silver nanoparticles) is applied for secondary recognition of MCF-7 cells in order to increase selectivity and produce an amplified signal. Differential pulse anodic stripping voltammetry was used to follow the electrochemical signal of the AgNPs. Under the optimal condition, the sensor responds to MCF-7 cells in the concentration range from 1.0 × 10² to 1.0 × 10⁷ cells·mL^-1 with a detection limit of 25 cells. We also demonstrate that the MUC1 tumor marker can be detected by the present biosensor. The assay is highly selective and sensitive, acceptably stable and reproducible. This warrants the applicability of the method to early diagnosis of breast cancer. Graphical abstract Schematic of the fabrication of an aptamer-based sandwich biosensor for Michigan Cancer Foundation-7 cells (MCF-7). A MWCNT-poly(glutamic acid) nanocomposite was used as a biocompatible matrix for MUC1-aptamer immobilization. Stripping voltammetry analysis of AgNPs was performed using aptamer conjugated AgNPs as signalling probe.

Electrochemical sensor for detection of cancer cell based on folic acid and octadecylamine-functionalized graphene aerogel microspheres

Early diagnosis of cancers is critical for prevention of metastasis and early treatment. The study reports an electrochemical sensor for detection of cancer cell based on folic acid (FA) and octadecylamine (OA)-functionalized graphene aerogel microspheres (FA-GAM-OA). Citric acid was mixed with FA and OA and heated at 180 °C for 4 h to form FA and OA-functionalized graphene oxide. The graphene oxide was employed as solid particle surfactant for stabilizing toluene-in-water emulsion. The graphene oxide sheets in the emulsion were self-assembled into graphene oxide gel microspheres on the water/toluene interfaces. Followed by free drying and reduction in H₂ at 400 °C for 5 h. The resulted FA-GAM-OA shows a sphere-like structure with an average diameter of 1.2 µm, the rich of open-pores and folic acid groups. Small particle size and good hydrophilicity make FA-GAM-OA can be dispersed in water for sensor preparation. The small size of graphene sheets and their self-assembly avoid a serious agglomeration of graphene sheets. The FA-GAM-OA offers a large surface area (1723.6 m² g^-1) and high electronic conductivity (2978.2 S m^-1). The covalent linkage and ordered alignment of folic acid groups at FA-GAM-OA surface achieve to specific cancer cell capture with high capture efficiency. The electrochemical sensor based on FA-GAM-OA exhibits extremely good analytical performances in detection of liver cancer cells with a linear range of 5-10⁵ cell mL^-1 giving a low detection limit of 5 cells mL^-1 (S/N = 3). The method was successfully applied to electrochemical detection of liver cancer cells in whole blood.

Halloysite Nanotube-Modified Plasmonic Interface for Highly Sensitive Refractive Index Sensing

We propose and demonstrate a novel strategy to modify the plasmonic interface by using a thin layer of halloysite nanotubes (HNTs). The modified surface plasmon resonance (SPR) sensor achieves a greatly improved sensitivity because the large surface area and high refractive index of the HNTs layer significantly increase the probing electric field intensity and hence the measurement sensitivity. More significantly, the thickness of the HNTs layer can be tailored by spraying different concentrations of HNTs ethanol suspension. The proposed sensors show significant superiority in terms of the highest sensitivity (10431 nm/RIU) and the enhancement fold (5.6-folds) over those reported previously. Additionally, the proposed approach is a chemical-free and environment-friendly modification method for the sensor interface, without additional chemical or biological amplification steps (no toxic solvents are used). These unique features make the proposed HNTs-SPR biosensor a simple, biocompatible, and low-cost platform for the trace-level detection of biochemical species in a rapid, sensitive, and nondestructive manner.

Research progresses on the functional polypeptides in the detection and imaging of breast cancer

Polypeptides as functional groups continue to garner significant interest in the detection and imaging of breast cancer, working as recognition elements, signal sources, building blocks and therapeutic reagents, etc.

Surface plasmon resonance biosensor for sensitive detection of microRNA and cancer cell using multiple signal amplification strategy

A sensitive and versatile surface plasmon resonance (SPR) biosensor was proposed for the detection of microRNA (miRNA) and cancer cell based on multiple signal amplification strategy. Thiol-modified hairpin probe, including a sequence complementary to the target miRNA, was first immobilized on the Au film. In the presence of target miRNA, the stem-loop structure of hairpin probe was unfolded, and then DNA-linked Au nanoparticles (AuNPs) were hybridized with the terminus of the unfolded hairpin probe. Subsequently, DNA-linked AuNPs initiated the formation of DNA supersandwich structure through the addition of two report DNA sequences. Owing to the electronic coupling between localized plasmon of the AuNPs and the surface plasmon wave, as well as the enhancement of the refractive index of the medium over the Au film induced by DNA supersandwich structure, the SPR response was significantly enhanced. Next, numerous positively charged silver nanoparticles (AgNPs) were absorbed onto the long-range DNA surpersandwich equably, resulting in a further increase of SPR response. Due to the enzyme-free multiple signal amplification strategy, as low as ca. 0.6 fM miRNA-21 could be detected. In addition, this biosensor showed high selectivity toward single-base mismatch. More importantly, this SPR biosensor was also used for cancer cell detection coupled with the cell-specific aptamer modified magnetic nanoparticles. Given that the biosensor avoided enzyme introduction, the limitation of the enzyme was overcome. The versatile biosensor has great potential for the broad applications in the field of clinical analysis.

Nanobiosensors in diagnostics

Medical diagnosis has been greatly improved thanks to the development of new techniques capable of performing very sensitive detection and quantifying certain parameters. These parameters can be correlated with the presence of specific molecules and their quantity. Unfortunately, these techniques are demanding, expensive, and often complicated. On the other side, progress in other fields of science and technology has contributed to the rapid growth of nanotechnology. Although being an emerging discipline, nanotechnology has raised huge interest and expectations. Most of the enthusiasm comes from new possibilities and properties of nanomaterials. Biosensors (simple, robust, sensitive, cost-effective) combined with nanomaterials, also called nanobiosensors, are serving as bridge between advanced detection/diagnostics and daily/routine tests. Here we review some of the latest applications of nanobiosensors in diagnostics field.