Magnetic-assisted self-assembled aptamer/protein hybrid probes for efficient capture and rapid detection of cancer cells in whole blood

Aptamers Versus Vascular Endothelial Growth Factor (VEGF): A New Battle against Ovarian Cancer

Cancer is one of the diseases that causes a high mortality as it involves unregulated and abnormal cell growth proliferation that can manifest in any body region. One of the typical ovarian cancer symptoms is damage to the female reproductive system. The death rate can be reduced through early detection of the ovarian cancer. Promising probes that can detect ovarian cancer are suitable aptamers. Aptamers, i.e., so-called chemical antibodies, have a strong affinity for the target biomarker and can typically be identified starting from a random library of oligonucleotides. Compared with other probes, ovarian cancer targeting using aptamers has demonstrated superior detection effectiveness. Various aptamers have been selected to detect the ovarian tumor biomarker, vascular endothelial growth factor (VEGF). The present review highlights the development of particular aptamers that target VEGF and detect ovarian cancer at its earliest stages. The therapeutic efficacy of aptamers in ovarian cancer treatment is also discussed.

Hierarchal polyaniline-folic acid nanostructures act as a platform for electrochemical detection of tumor cells

The fabrication of electrochemical sensing platforms for cancer monitoring by quantifying circulating tumor cells (CTCs) in blood holds promise for providing a low-cost, rapid, feasible, and safe approach for cancer diagnosis. Here, we isolate cancer cells using CoFe₂O₄ nanoparticles functionalized with folic acid and chitosan as an inexpensive magnetic nanoprobe. This electrochemical cytosensing platform was realized using polyaniline-folic acid nanohybrids with a three-dimensional hierarchical structure that presents abundant affinity sites toward overexpressed folate bioreceptors on cancer cells, in addition to retaining satisfied conductivity. Furthermore, 3D modeling and simulation of the polyaniline-folic acid structures were conducted to investigate the stable complex between aniline and folate, and the interaction between the polyaniline-folate complex and folate receptor alpha1, a bioreceptor on MCF-7 was revealed for the first time. The limit of detection was calculated to be 4 cells mL^-1 with a linear range from 50 to 10⁶ cells mL^-1.

Specific recognition and photothermal release of circulating tumor cells using near-infrared light-responsive 2D MXene nanosheets@hydrogel membranes

2D materials with attractive optical properties are promising for individualized cancer immunotherapy. Isolation, capture, and release of circulating tumor cells (CTCs) are of great significance for promoting the process of early diagnosis of cancers. MXene nanosheets incorporated gelatin hydrogel offers the possibility of achieving near-infrared (NIR) light response to initiate the photothermal effect. Herein, the design and preparation of Ti₃C₂T_x MXene nanosheets-embedded thermoresponsive gelatin hydrogel membrane with NIR light-responsive for the specific capture and release of CTCs were reported. The membrane was fabricated by casting Ti₃C₂T_x-embedded gelatin onto a substrate and then modified with epithelial-cell adhesion-molecule antibody (anti-EpCAM) for the specific recognition and separation of CTCs from whole blood. The captured cells can be released without damage with dual-mode containing temperature-responsive release (gelatin deconstructed at 37 °C) and photothermal site-release (Ti₃C₂T_x induced by NIR light). Furthermore, we were able to achieve an average efficient release rate of 89 % of captured cells with stable cell viability of 87 % via the NIR light irradiation. This work may provide the promising potential for retrieval of single cells in clinical diagnosis.

The Potential of Aptamer-Mediated Liquid Biopsy for Early Detection of Cancer

The early detection of cancer favors a greater chance of curative treatment and long-term survival. Exciting new technologies have been developed that can help to catch the disease early. Liquid biopsy is a promising non-invasive tool to detect cancer, even at an early stage, as well as to continuously monitor disease progression and treatment efficacy. Various methods have been implemented to isolate and purify bio-analytes in liquid biopsy specimens. Aptamers are short oligonucleotides consisting of either DNA or RNA that are capable of binding to target molecules with high specificity. Due to their unique properties, they are considered promising recognition ligands for the early detection of cancer by liquid biopsy. A variety of circulating targets have been isolated with high affinity and specificity by facile modification and affinity regulation of the aptamers. In this review, we discuss recent progress in aptamer-mediated liquid biopsy for cancer detection, its associated challenges, and its future potential for clinical applications.

Lignin, lipid, protein, hyaluronic acid, starch, cellulose, gum, pectin, alginate and chitosan-based nanomaterials for cancer nanotherapy: Challenges and opportunities

Although nanotechnology-driven drug delivery systems are relatively new, they are rapidly evolving since the nanomaterials are deployed as effective means of diagnosis and delivery of assorted therapeutic agents to targeted intracellular sites in a controlled release manner. Nanomedicine and nanoparticulate drug delivery systems are rapidly developing as they play crucial roles in the development of therapeutic strategies for various types of cancer and malignancy. Nevertheless, high costs, associated toxicity and production of complexities are some of the critical barriers for their applications. Green nanomedicines have continually been improved as one of the viable approaches towards tumor drug delivery, thus making a notable impact on which considerably affect cancer treatment. In this regard, the utilization of natural and renewable feedstocks as a starting point for the fabrication of nanosystems can considerably contribute to the development of green nanomedicines. Nanostructures and biopolymers derived from natural and biorenewable resources such as proteins, lipids, lignin, hyaluronic acid, starch, cellulose, gum, pectin, alginate, and chitosan play vital roles in the development of cancer nanotherapy, imaging and management. This review uncovers recent investigations on diverse nanoarchitectures fabricated from natural and renewable feedstocks for the controlled/sustained and targeted drug/gene delivery systems against cancers including an outlook on some of the scientific challenges and opportunities in this field. Various important natural biopolymers and nanomaterials for cancer nanotherapy are covered and the scientific challenges and opportunities in this field are reviewed.

Semiconducting CuxNi3-x(hexahydroxytriphenylene)2 framework for electrochemical aptasensing of C6 glioma cells and epidermal growth factor receptor

A 2D CuNi metal-organic framework (MOF) named CuxNi3-x(HHTP)2 was synthesized with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) as the linker and was used as a sensitive scaffold to adsorb aptamer strands for the electrochemical detection of living C6 glioma cells and one of their biomarkers, epidermal growth factor receptor (EGFR). Different from conventional MOFs, the CuxNi3-x(HHTP)2 MOF comprises long-range delocalized electrons, a graphene-analog nanostructure, multiple metal states (Cu0/Cu+/Cu2+ and Ni2+/Ni3+), and abundant oxygen vacancies. With these features, the CuxNi3-x(HHTP)2 MOF anchored a large amount of C6 cell-targeted aptamer strands via coordination among metal centers, oligonucleotides, π-π stacking, and van der Waals force. The CuxNi3-x(HHTP)2-based cytosensor showed a low limit of detection (LOD) of 21 cells mL-1 toward C6 glioma cells within a wide range from 50 cells mL-1 to 1 × 105 cells mL-1. Moreover, the proposed aptasensor displayed high selectivity, good stability, acceptable reproducibility, and a low LOD of 0.72 fg mL-1 for detecting EGFR with the concentration ranging from 1 fg mL-1 to 1 ng mL-1. The aptasensor based on the CuxNi3-x(HHTP)2 MOF exhibited superior sensing performance over those based on its monometallic analogues such as Cu3(HHTP)2 MOF and Ni3(HHTP)2 MOF. Hence, this sensing strategy based on a bimetallic semiconducting MOF shows great potential for cancer diagnosis.

Aptamer-Based Detection of Circulating Targets for Precision Medicine

The past decade has witnessed ongoing progress in precision medicine to improve human health. As an emerging diagnostic technique, liquid biopsy can provide real-time, comprehensive, dynamic physiological and pathological information in a noninvasive manner, opening a new window for precision medicine. Liquid biopsy depends on the sensitive and reliable detection of circulating targets (e.g., cells, extracellular vesicles, proteins, microRNAs) from body fluids, the performance of which is largely governed by recognition ligands. Aptamers are single-stranded functional oligonucleotides, capable of folding into unique tertiary structures to bind to their targets with superior specificity and affinity. Their mature evolution procedure, facile modification, and affinity regulation, as well as versatile structural design and engineering, make aptamers ideal recognition ligands for liquid biopsy. In this review, we present a broad overview of aptamer-based liquid biopsy techniques for precision medicine. We begin with recent advances in aptamer selection, followed by a summary of state-of-the-art strategies for multivalent aptamer assembly and aptamer interface modification. We will further describe aptamer-based micro-/nanoisolation platforms, aptamer-enabled release methods, and aptamer-assisted signal amplification and detection strategies. Finally, we present our perspectives regarding the opportunities and challenges of aptamer-based liquid biopsy for precision medicine.

An aptasensor for the detection of ampicillin in milk using a personal glucose meter

Antibiotic residues in foods have aroused wide public concern because of their potential side-effects. It is imperative to develop a simple, accurate and reliable method for the detection of antibiotic residues in foods. In this paper, we report a novel, facile and sensitive method for the detection of ampicillin in milk using a commercial personal glucose meter (PGM). Magnetic beads (MBs) were employed as the platform, an ampicillin aptamer was used as the recognition element and streptavidin was utilized as the bridge to link invertase and the aptamer. After the hydrolysis of sucrose to glucose, the concentration of glucose was quantitatively measured using the PGM. The difference of PGM signals with and without addition of ampicillin exhibits a good linear correlation with the logarithm of ampicillin concentrations in the range of 2.5 × 10-10 mol L-1 to 1.0 × 10-7 mol L-1 with a detection limit of 2.5 × 10-10 mol L-1 (S/N = 3). Finally, the proposed method was successfully applied for the detection of ampicillin residue in milk.

An electrochemical aptasensor for ATP based on a configuration-switchable tetrahedral DNA nanostructure

A novel electrochemical aptasensor for ATP was developed based on an aptamer-embedded configuration-switchable tetrahedral DNA nanostructure (TDN) and the formation of a G-quadruplex. This unique TDN was formed through the self-assembly of four specially designed single-stranded DNA (ssDNA) sequences (S1, S2, S3 and S4). The TDN was immobilized on the surface of a Au electrode through the thiol groups at the 5'-end of S1, S2 and S3. Five edges of the TDN were designed to form a double helix to preserve the structural robustness of the tetrahedron, while the ATP aptamer embedded sequence (S3) was designed to be located at the rest edge. The two terminals of S4 at the same edge were composed of two split G-quadruplex-forming sequences, which were non-complementary to the aptamer. This edge offered the configuration-switchable characteristic of the TDN. In the absence of ATP, the TDN remained in a relaxed state, and the G-quadruplex cannot form due to the large distance between the split G-quadruplex-forming sequences. However, in the presence of ATP, the aptamer combined with ATP and shortened the distance between the split sequences, resulting in the taut state of the TDN and the formation of a G-quadruplex at the edge. After the addition of hemin, the differential pulse voltammograms (DPVs) were used to quantify ATP. The sensor revealed a dynamic response range from 0.1 nM to 1 μM, with a detection limit of 50 pM. In addition, the specificity and practicability in real samples were also verified, indicating its potential applications.

Application of DNA nanodevices for biosensing

Deoxyribonucleic acid (DNA), the carrier of genetic information in living life, is an essential biomacromolecule in almost all living systems. DNA has advantages including, programmability, predictability, high rigidity, and stability. Through self-assembly or combination with other nanomaterials (such as gold nanoparticles, graphene oxides, quantum dots, and polymers), DNA can be applied to construct specific, stable, biocompatible, and functional nanodevices. DNA nanodevices have made greater contributions in a plethora of fields. In this review, we discuss the recent progress of DNA nanodevices in molecular detection and analysis. Meanwhile, we prospect the development of various DNA devices in biological analysis, clinical diagnosis and biomedical research.

A Novel Cell-Assisted Enhanced Chemiluminescence Strategy for Rapid and Label-Free Detection of Tumor Cells in Whole Blood

In this study, an interesting phenomenon was found where cells (including tumor and normal cells) managed to significantly enhance chemiluminescence (CL) signals. The possible reaction mechanism may be that cells can be severely damaged by CL substrates, and the released contents, possibly proteins (such as cytochrome c), can remarkably magnify CL owing to the increased production of singlet oxygen. More importantly, based on the above phenomena, a novel cell-assisted enhanced CL strategy was proposed for the rapid and label-free detection of tumor cells. The complexes of aptamer sgc8c and streptavidin-modified magnetic beads were employed to recognize and isolate target tumor cells from whole blood. The enhanced CL intensity, which was triggered directly by the captured cells, was measured. The proposed strategy exhibited a good detection performance with a linear range from 200 to 10,000 cells/mL. The analysis can be finished in ∼30 min, and the limit of detection was down to 100 cells/mL. The recoveries and relative standard deviations were 97.81-102.71% and 3.46-12.71%, respectively. Moreover, the established method can successfully distinguish the leukemia patients from healthy people. Therefore, it provides a novel, rapid, and simple method for the determination of tumor cells, which can be used in further practice.