Dual aptamer-functionalized silica nanoparticles for the highly sensitive detection of breast cancer

Combining Bioorthogonal Chemistry with Fluorescent Silica Nanoparticles for the Ultrasensitive Detection of the HIV-1 p24 Antigen

Early detection and viral concentration monitoring of human immunodeficiency virus in resource-poor settings are important to control disease spread and reduce mortality. Nucleic acid amplification tests are expensive for low-resource settings. Lateral flow antibody tests are not sensitive if testing is performed within 7-10 days, and these tests are not quantitative. We describe a signal enhancement technique based on fluorescent silica nanoparticles and bioorthogonal chemistries for the femtomolar detection of the HIV-1 p24 antigen. We developed a magnetic bead-based assay, wherein we used fluorescent-dye-encapsulated silica nanoparticles as reporters. The number of reporters was increased by using bioorthogonal chemistry to provide signal enhancement. The limit and range of detection of the sandwich immunoassay using alternating multiple layers for p24 in human serum were found to be 46 fg/mL (1.84 fM) and 46 fg/mL to 10 ng/mL, respectively. This simple assay was 217-fold higher in sensitivity compared to that of commercial enzyme-linked immunoassays (limit of detection of 10 pg/mL).

Stimuli-responsive biodegradable silica nanoparticles: From native structure designs to biological applications

Due to their inherent advantages, silica nanoparticles (SiNPs) have greatly potential applications as bioactive materials in biosensors/biomedicine. However, the long-term and nonspecific accumulation in healthy tissues may give rise to toxicity, thereby impeding their widespread clinical application. Hence, it is imperative and noteworthy to develop biodegradable and clearable SiNPs for biomedical purposes. Recently, the design of multi-stimuli responsive SiNPs to improve degradation efficiency under specific pathological conditions has increased their clinical trial potential as theranostic nanoplatform. This review comprehensively summaries the rational design and recent progress of biodegradable SiNPs under various internal and external stimuli for rapid in vivo degradation and clearance. In addition, the factors that affect the biodegradation of SiNPs are also discussed. We believe that this systematic review will offer profound stimulus and timely guide for further research in the field of SiNP-based nanosensors/nanomedicine.

Advances in Aptamers-Based Applications in Breast Cancer: Drug Delivery, Therapeutics, and Diagnostics

Aptamers are synthetic single-stranded oligonucleotides (such as RNA and DNA) evolved in vitro using Systematic Evolution of Ligands through Exponential enrichment (SELEX) techniques. Aptamers are evolved to have high affinity and specificity to targets; hence, they have a great potential for use in therapeutics as delivery agents and/or in treatment strategies. Aptamers can be chemically synthesized and modified in a cost-effective manner and are easy to hybridize to a variety of nano-particles and other agents which has paved a way for targeted therapy and diagnostics applications such as in breast tumors. In this review, we systematically explain different aptamer adoption approaches to therapeutic or diagnostic uses when addressing breast tumors. We summarize the current therapeutic techniques to address breast tumors including aptamer-base approaches. We discuss the next aptamer-based therapeutic and diagnostic approaches targeting breast tumors. Finally, we provide a perspective on the future of aptamer-based sensors for breast therapeutics and diagnostics. In this section, the therapeutic applications of aptamers will be discussed for the targeting therapy of breast cancer.

Recent advances in nanomaterials-based optical sensors for detection of various biomarkers (inorganic species, organic and biomolecules)

This review briefly emphasizes the different detection approaches (electrochemical sensors, chemiluminescence, surface-enhanced Raman scattering), functional nanostructure materials (quantum dots, metal nanoparticles, metal nanoclusters, magnetic nanomaterials, metal oxide nanoparticles, polymer-based nanomaterials, and carbonaceous nanomaterials) and detection mechanisms. Further, this review emphasis on the integration of functional nanomaterials with optical spectroscopic techniques for the identification of various biomarkers (nucleic acids, glucose, uric acid, oxytocin, dopamine, ascorbic acid, bilirubin, spermine, serotonin, thiocyanate, Pb²⁺ , Cu²⁺ , Hg²⁺ , F^- , peptides, and cancer biomarkers (mucin 1, prostate specific antigen, carcinoembryonic antigen, CA15-3, human epidermal growth factor receptor 2, C-reactive protein, and interleukin-6). Analytical characteristics of nanomaterials-based optical sensors are summarized in Tables, providing the insights of nanomaterials-based optical sensors for biomarkers detection. Finally, the opportunities and challenges of nanomaterials-based optical analytical approaches for the detection of various biomarkers (inorganic, organic, biomolecules, peptides and proteins) are discussed.

An update on dual targeting strategy for cancer treatment

The key issue in the treatment of solid tumors is the lack of efficient strategies for the targeted delivery and accumulation of therapeutic cargoes in the tumor microenvironment (TME). Targeting approaches are designed for more efficient delivery of therapeutic agents to cancer cells while minimizing drug toxicity to normal cells and off-targeting effects, while maximizing the eradication of cancer cells. The highly complicated interrelationship between the physicochemical properties of nanoparticles, and the physiological and pathological barriers that are required to cross, dictates the need for the success of targeting strategies. Dual targeting is an approach that uses both purely biological strategies and physicochemical responsive smart delivery strategies to increase the accumulation of nanoparticles within the TME and improve targeting efficiency towards cancer cells. In both approaches, either one single ligand is used for targeting a single receptor on different cells, or two different ligands for targeting two different receptors on the same or different cells. Smart delivery strategies are able to respond to triggers that are typical of specific disease sites, such as pH, certain specific enzymes, or redox conditions. These strategies are expected to lead to more precise targeting and better accumulation of nano-therapeutics. This review describes the classification and principles of dual targeting approaches and critically reviews the efficiency of dual targeting strategies, and the rationale behind the choice of ligands. We focus on new approaches for smart drug delivery in which synthetic and/or biological moieties are attached to nanoparticles by TME-specific responsive linkers and advanced camouflaged nanoparticles.

Force-Coded Strategy for the Simultaneous Detection of Multiple Tumor-Related Proteins

Multiplexed simultaneous detection of various cancer markers is required for accurate diagnosis and treatment of early cancer. In this work, we present a force-coded strategy for the simultaneous detection of tumor-related proteins with tunable dynamic range via magnetic sensing. The multiplexing capability of this method is achieved by designing DNA devices that can recognize different biomarkers and code them with different binding forces measured by the force-induced remnant magnetization spectroscopy, which is not influenced by the color of the light and the solution. Moreover, the force-coded assay with high sensitivity and adjustable detection range is robust, which could be used for practical biological applications such as magnetic sensing, handheld miniaturized systems, and potential in vivo diagnosis.

Construction and bioapplications of aptamer-based dual recognition strategy

Aptamer-based dual recognition strategy, using dual aptamers or the cooperation of aptamers with other recognition elements, can better utilize the advantages of each recognition molecule and increase the design flexibility to effectively overcome the limitations of a single molecule recognition strategy, thereby improving the sensitivity and selectivity and facilitating the regulation of biological process. Hence, this review systematically tracks the construction and application of dual aptamers recognition strategy in the versatile detection of protein biomarkers, pathogenic microorganisms, cancer cells, and the treatment of some diseases and, more importantly, in functional regulation and imaging of cell-surface protein receptors. Then, the cooperation of aptamers with other recognition elements are briefly introduced. Potential challenges facing this field have been highlighted, aiming to expand bioanalytical applications of aptamer-based dual or multiple recognition strategies and meet the growing demand for precision medicine.

Biosensors and nanotechnology for cancer diagnosis (lung and bronchus, breast, prostate, and colon): a systematic review

The second cause of death in the world has been reported to be cancer, and it has been on the rise in recent years. As a result of the difficulties of cancer detection and its treatment, the survival rate of patients is unclear. The early detection of cancer is an important issue for its therapy. Cancer detection based on biomarkers may effectively enhance the early detection and subsequent treatment. Nanomaterial-based nanobiosensors for cancer biomarkers are excellent tools for the molecular detection and diagnosis of disease. This review reports the latest advancement and attainment in applying nanoparticles to the detection of cancer biomarkers. In this paper, the recent advances in the application of common nanomaterials like graphene, carbon nanotubes, Au, Ag, Pt, and Fe₃O₄together with newly emerged nanoparticles such as quantum dots, upconversion nanoparticles, inorganics (ZnO, MoS₂), and metal-organic frameworks for the diagnosis of biomarkers related to lung, prostate, breast, and colon cancer are highlighted. Finally, the challenges, outlook, and closing remarks are given.

Aptamer grafted nanoparticle as targeted therapeutic tool for the treatment of breast cancer

Breast carcinomas repeat their number and grow exponentially making it extremely frequent malignancy among women. Approximately, 70-80% of early diagnosed or non-metastatic conditions are treatable while the metastatic cases are considered ineffective to treat with current ample amount of therapy. Target based anti-cancer treatment has been in the limelight for decades and is perceived significant consideration of scientists. Aptamers are the 'coming of age' therapeutic approach, selected using an appropriate tool from the library of sequences. Aptamers are non-immunogenic, stable, and high-affinity ligand which are poised to reach the clinical benchmark. With the heed in nanoparticle application, the delivery of aptamer to the specific site could be enhanced which also protects them from nuclease degradation. Moreover, nanoparticles due to robust structure, high drug entrapment, and modifiable release of cargo could serve as a successful candidate in the treatment of breast carcinoma. This review would showcase the method and modified method of selection of aptamers, aptamers that were able to make its way towards clinical trial and their targetability and selectivity towards breast cancers. The appropriate usage of aptamer-based biosensor in breast cancer diagnosis have also been discussed.

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.

Aptamer-based sensing of breast cancer biomarkers: a comprehensive review of analytical figures of merit

INTRODUCTION

Accurate determination of the aberrantly expressed biomarkers such as human epidermal growth factor receptor 2 (HER2), carcinoembryonic antigen (CEA), platelet-derived growth factor (PDGF), mucin 1 (MUC1), and vascular endothelial growth factor VEGF₁₆₅ have played an essential role in the clinical management of the breast cancer. Assessment of these cancer-specific biomarkers has conventionally relied on time-taking methods like the enzyme-linked immunosorbent assay and immunohistochemistry. However, recent development in the aptamer-based diagnostics has allowed developing tools that may substitute the conventional means of biomarker assessment in breast cancer. Adopting the aptamer-based diagnostic tools (aptasensors) to clinical practices will depend on their analytical performance on clinical samples.

AREAS COVERED

In this review, we provide an overview of the analytical merits of HER2, CEA, PDGF, MUC1, and VEGF₁₆₅ aptasensors. Scopus and Pubmed databases were searched for studies reporting aptasensor development for the listed breast cancer biomarkers in the past one decade. Linearity, detection limit, and response time are emphasized.

EXPERT OPINION

In our opinion, aptasensors have proven to be on a par with the antibody-based methods for detection of various breast cancer biomarkers. Though robust validation of the aptasensors on significant sample size is required, their ability to detect pathophysiological range of biomarkers suggest the possibility of future clinical adoption.

Aptamer-based nanostructured interfaces for the detection and release of circulating tumor cells

Analysis of circulating tumor cells (CTCs) can provide significant clinical information for tumors, which has proven to be helpful for cancer diagnosis, prognosis monitoring, treatment efficacy, and personalized therapy. However, CTCs are an extremely rare cell population, which challenges the isolation of CTCs from patient blood. Over the last few decades, many strategies for CTC detection have been developed based on the physical and biological properties of CTCs. Among them, nanostructured interfaces have been widely applied as CTC detection platforms to overcome the current limitations associated with CTC capture. Furthermore, aptamers have attracted significant attention in the detection of CTCs due to their advantages, including good affinity, low cost, easy modification, excellent stability, and low immunogenicity. In addition, effective and nondestructive release of CTCs can be achieved by aptamer-mediated methods that are used under mild conditions. Herein, we review some progress in the detection and release of CTCs through aptamer-functionalized nanostructured interfaces.

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.

Silica Nanoparticles

Silica consists of one silicon atom and two oxygen atoms (SiO₂) and is commonly used in various aspects of daily life. For example, it has been used as glass, insulator, and so on. Nowadays, silica is used as core reagents for fabricating and encapsulating nanoparticles (NPs). In this chapter, the usage of silica in nanotechnology is described. Synthesis and surface modification of silica nanoparticles (SiNPs), including via the Stöber method, reverse microemulsion method, and modified sol-gel method, are illustrated. Then, various NPs with silica encapsulation are explained. At last, the biological applications of those mentioned NPs are described.

Aptamer-Modified Nanoparticles in Medical Applications

Since aptamers have been selected against a broad range of target structures of medical interest and nanoparticles are available with diverse properties, aptamer-modified nanoparticles can be used in various diagnostic and therapeutic applications. While the aptamer is responsible for specificity and affinity of the conjugate, the nanoparticles' function varies from signal generation in diagnostic approaches to drug loading in drug delivery systems. Within this chapter different medical applications of aptamer-modified nanoparticles will be summarized and underlying principles will be described.

Recent advances in optical aptasensor technology for amplification strategies in cancer diagnostics

Aptamers are chemically synthetic single-stranded DNA or RNA molecules selected by molecular evolution. They have been widely used as attractive tools in biosensing and bioimaging because they can bind to a large variety of targets with high sensitivity and high affinity and specificity. As recognition elements, aptamers contribute in particular to cancer diagnostics by recognizing different cancer biomarkers, while they can also facilitate ultrasensitive detection by further employing signal amplification elements. Optical techniques have been widely used for direct and real-time monitoring of cancer-related biomolecules and bioprocesses due to the high sensitivity, quick response, and simple operation, which has greatly benefited cancer diagnostics. In this review, we highlight recent advances in optical platform-based sensing strategies for cancer diagnostics aided by aptamers. Limitations and current challenges are also discussed.

Resonant-Cantilever-Detected Kinetic/Thermodynamic Parameters for Aptamer-Ligand Binding on a Liquid-Solid Interface

Nucleic acid aptamers have been widely used as recognition elements on various biosensing interfaces, but quantitative kinetic/thermodynamic analysis for revealing the aptamer-ligand binding mechanism, which occurs on a liquid-solid interface, has not been realized due to a lack of usable biophysical tools. Herein we apply a resonant microcantilever sensor to continuously record the frequency shift according to the binding-induced mass change on the liquid-solid interface. The frequency-shift curve is used for tracing the reaction process and is fitted with classic equations to calculate a set of kinetic/thermodynamic parameters, such as rate constants (k_a = 902.95 M^-1 s^-1, k_d = 0.000141 s^-1), equilibrium constants (K_D = 1.55 μM), the Gibbs free energy (ΔG° = -32.57 kJ/mol), and the activation energy (E_a = 38.03 kJ/mol) for the immobilized aptamer and free ATP. This quantitative analysis method is label-free, calibration-free, and highly sensitive. The kinetic/thermodynamic parameter detection method provides new resolution to the in-depth understanding of the ligand-aptamer interaction on the liquid-solid interface for biosensing or lab-on-a-chip applications.

Aptamer Hybrid Nanocomplexes as Targeting Components for Antibiotic/Gene Delivery Systems and Diagnostics: A Review

With the passage of time and more advanced societies, there is a greater emergence and incidence of disease and necessity for improved treatments. In this respect, nowadays, aptamers, with their better efficiency at diagnosing and treating diseases than antibodies, are at the center of attention. Here, in this review, we first investigate aptamer function in various fields (such as the detection and remedy of pathogens, modification of nanoparticles, antibiotic delivery and gene delivery). Then, we present aptamer-conjugated nanocomplexes as the main and efficient factor in gene delivery. Finally, we focus on the targeted co-delivery of genes and drugs by nanocomplexes, as a new exciting approach for cancer treatment in the decades ahead to meet our growing societal needs.

Nucleic-Acid Structures as Intracellular Probes for Live Cells

The chemical composition of cells at the molecular level determines their growth, differentiation, structure, and function. Probing this composition is powerful because it provides invaluable insight into chemical processes inside cells and in certain cases allows disease diagnosis based on molecular profiles. However, many techniques analyze fixed cells or lysates of bulk populations, in which information about dynamics and cellular heterogeneity is lost. Recently, nucleic-acid-based probes have emerged as a promising platform for the detection of a wide variety of intracellular analytes in live cells with single-cell resolution. Recent advances in this field are described and common strategies for probe design, types of targets that can be identified, current limitations, and future directions are discussed.

A silver nanoparticle-assisted signal amplification electrochemiluminescence biosensor for highly sensitive detection of mucin 1

A novel electrochemiluminescence (ECL) biosensor was developed in this study, which was based on the Ag-NP modified tetrahedral DNA nanostructure.

Combined Raman and AFM detection of changes in HeLa cervical cancer cells induced by CeO2 nanoparticles – molecular and morphological perspectives

Raman and AFM analyses represent a tool for the evaluation of cytotoxic and anti-proliferative effects in cells induced by CeO₂ nanoparticles.

A Multicolor Immunosensor for Sensitive Visual Detection of Breast Cancer Biomarker Based on Sensitive NADH-Ascorbic-Acid-Mediated Growth of Gold Nanobipyramids

Many studies have demonstrated that the extracellular domain of human epidermal growth factor receptor 2 (HER2 ECD) level in serum can act as a breast cancer biomarker and serve as a monitoring neoadjuvant therapy of breast cancer. In this study, we developed a sensitive ascorbic acid (AA)-mediated AuNBPs (gold nanobipyramids) growth method with NADH (reduced nicotinamide adenine dinucleotide I) assistance, and we further fabricated a high-resolution multicolor immunosensor for sensitive visual detection of HER2 ECD in serum by using AuNBPs as signal and antibody as recognition probe. The NADH-assisted AA-mediated method effectively suppressed color formation in the blank and greatly improved the sensitivity of mediating AuNBPs growth, allowing us to use a low concentration of AA to mediate AuNBPs growth to generate more colorful and clearer color changes. The proposed multicolor immunosensor has higher resolution and more color changes corresponding to HER2 ECD concentrations. It can be used to detect as low as 0.5 ng/mL of HER2 ECD by bare eye observation and 0.05 ng/mL of HER2 ECD by UV-visible spectrophotometry. Using the immunosensor, we have successfully detected HER2 ECD in human serum with a recovery of 94%-96% and an RSD (n = 5) < 5%. The results obtained with our immunosensor were consistent with those obtained with ELISA, verifying the immunosensor has good accuracy. The immunosensor exhibited a vivid multicolor change, has low visual detection limit, excellent specificity and reproducibility, and robust resistance to matrix. All the above features makes our immunosensor a promising assay for the early diagnosis of HER2-dependent breast cancers in clinical diagnosis.

Polyfunctionalised Nanoparticles Bearing Robust Gadolinium Surface Units for High Relaxivity Performance in MRI

The first example of an octadentate gadolinium unit based on DO3A (hydration number q=1) with a dithiocarbamate tether has been designed and attached to the surface of gold nanoparticles (around 4.4 nm in diameter). In addition to the superior robustness of this attachment, the restricted rotation of the Gd complex on the nanoparticle surface leads to a dramatic increase in relaxivity (r₁ ) from 4.0 mm^-1  s^-1 in unbound form to 34.3 mm^-1  s^-1 (at 10 MHz, 37 °C) and 22±2 mm^-1  s^-1 (at 63.87 MHz, 25 °C) when immobilised on the surface. The one-pot synthetic route provides a straightforward and versatile way of preparing a range of multifunctional gold nanoparticles. The incorporation of additional surface units for biocompatibility (PEG and thioglucose units) and targeting (folic acid) leads to little detrimental effect on the high relaxivity observed for these non-toxic multifunctional materials. In addition to the passive targeting attributed to gold nanoparticles, the inclusion of a unit capable of targeting the folate receptors overexpressed by cancer cells, such as HeLa cells, illustrates the potential of these assemblies.

In vitro selection of aptamer S1 against MCF-7 human breast cancer cells

Breast cancer is the most common female cancer. However, the known effective specific biomarkers for breast cancer are still scarce. Abnormal membrane proteins serve as ideal biomarkers for disease diagnoses, therapeutics and prognosis. Thus aptamers (single-stranded oligonucleotide molecules) with molecular recognition properties can be used as efficient tools to sort cells based on differences in cell surface architecture between normal and tumor cells. In this study, we aimed to screen specific aptamer against MCF-7 human breast cancer cells. Cell-SELEX process was performed to isolate aptamers from a combinatorial single-stranded nucleic acid library that selectively targeting surface proteins of MCF-7 cells in contrast with MCF-10A human mammary epithelial cells. The process was repeated until the pool was enriched for sequences that specifically recognizing MCF-7 cells in monitoring by flow cytometry. Subsequently, the enriched pool was cloned into bacteria, and positive clones were sequenced to obtain individual sequences. Representative sequences were chemically synthesized and evaluated their binding affinities to MCF-7 cells. As a result, an aptamer S1 was finally identified to have high binding affinity with equilibrium dissociation constant (K_d) value of 29.9 ± 6.0 nM. FAM-labeled aptamer S1 induced fluorescence shift in MCF-7 cells but not in MCF-10A human mammary epithelial cells, or MDA-MB-453 and MDA-MB-231 human breast cancer cells. Furthermore, result of cell imaging observed from laser confocal fluorescence microscope showed that MCF-7 cells exhibited stronger fluorescence signal resulted from Cy5-labeled aptamer S1 than MCF-10A cells. The above findings suggested that S1 may be a specificity and selectivity aptamer for MCF-7 cells and useful for the breast cancer detection and diagnosis.

Peptide Functionalization of Gold Nanoparticles for the Detection of Carcinoembryonic Antigen in Blood Plasma via SPR-Based Biosensor

Nanoparticles functionalized with specific biological recognition molecules play a major role for sensor response enhancement in surface plasmon resonance (SPR) based biosensors. The functionalization procedure of such nanoparticles is crucial, since it influences their interactions with the environment and determines their applicability to biomolecular detection in complex matrices. In this work we show how the ζ-potential (Zpot) of bio-functionalized gold spherical NPs (Bio-NPs) is related to the SPR sensor response enhancement of an immune-sandwich-assay for the detection of the carcinoembryonic antigen (CEA), a cancer marker for colorectal carcinomas. In particular, we prepare bio-functional nanoparticles by varying the amount of peptide (either streptavidin or antibody against CEA) bound on their surface. Specific and non-specific sensor responses, reproducibility, and colloidal stability of those bio-functional nanoparticles are measured via SPR and compared to ζ-potential values. Those parameters are first measured in buffer solution, then measured again when the surface of the biosensor is exposed to blood plasma, and finally when the nanoparticles are immersed in blood plasma and flowed overnight on the biosensor. We found that ζ-potential values can guide the design of bio-functional NPs with improved binding efficiency and reduced non-specific sensor response, suitable reproducibility and colloidal stability, even in complex matrixes like blood plasma.

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.

Aptamer-displaying peptide amphiphile micelles as a cell-targeted delivery vehicle of peptide cargoes

Peptide amphiphile micelles (PAMs) are attractive vehicles for the delivery of a variety of therapeutic and prophylactic peptides. However, a key limitation of PAMs is their lack of preferential targeting ability. In this paper, we describe our design of a PAM system that incorporates a DNA oligonucleotide amphiphile (antitail amphiphile-AA) to form A/PAMs. A cell-targeting DNA aptamer with a 3' extension sequence (tail) complementary to the AA is annealed to the surface to form aptamer-displaying PAMs (Aptamer~A/PAMs). Aptamer~A/PAMs are small, anionic, stable nanoparticles capable of delivering a large mass percentage peptide amphiphile (PA) compared to targeting DNA components. Aptamer~A/PAMs are stable for over 4 h in the presence of biological fluids. Additionally, the aptamer retains its cell-targeting properties when annealed to the A/PAM, thus leading to enhanced delivery to a specifically-targeted B-cell leukemia cell line. This exciting modular technology can be readily used with a library of different targeting aptamers and PAs, capable of improving the bioavailability and potency of the peptide cargo.

Photonic crystal enhanced fluorescence immunoassay on diatom biosilica

Fluorescence biosensing is one of the most established biosensing methods, particularly fluorescence spectroscopy and microscopy. These are two highly sensitive techniques but require high-grade electronics and optics to achieve the desired sensitivity. Efforts have been made to implement these methods using consumer grade electronics and simple optical setups for applications such as point-of-care diagnostics, but the sensitivity inherently suffers. Sensing substrates, capable of enhancing fluorescence are thus needed to achieve high sensitivity for such applications. In this paper, we demonstrate a photonic crystal-enhanced fluorescence immunoassay biosensor using diatom biosilica, which consists of silica frustules with sub-100 nm periodic pores. Utilizing the enhanced local optical field, the Purcell effect and increased surface area from the diatom photonic crystals, we create ultrasensitive immunoassay biosensors that can significantly enhance fluorescence spectroscopy as well as fluorescence imaging. Using standard antibody-antigen-labeled antibody immunoassay protocol, we experimentally achieved 100× and 10× better detection limit with fluorescence spectroscopy and fluorescence imaging respectively. The limit of detection of the mouse IgG goes down to 10^-16 M (14 fg/mL) and 10^-15 M (140 fg/mL) for the two respective detection modalities, virtually sensing a single mouse IgG molecule on each diatom frustule. The effectively enhanced fluorescence imaging in conjunction with the simple hot-spot counting analysis method used in this paper proves the great potential of diatom fluorescence immunoassay for point-of-care biosensing.

Probing ATP/ATP-Aptamer or ATP-Aptamer Mutant Complexes by Microscale Thermophoresis and Molecular Dynamics Simulations: Discovery of an ATP-Aptamer Sequence of Superior Binding Properties

Microscale thermophoresis (MST) is used to follow the dissociation constants corresponding to ATTO 488-labeled adenosine triphosphate (ATP) and the ATP-aptamer or ATP-aptamer mutants that include two binding sites for the ATP ligand. A set of eight ATP-aptamer mutants, where the thymidine bases, within the reported ATP binding aptamer sites, are substituted with cytosine bases, are examined. The MST-derived dissociation constant of ATP to the reported aptamer is K_d = 31 ± 3 μM, whereas most of the aptamer mutants show lower affinity (higher K_d values) toward the ATP ligand. One aptamer mutant reveals, however, a higher affinity toward the ATP ligand, as compared to the reported ATP-aptamer. Molecular dynamics and docking simulations identify the structural features that control the affinities of binding of the ATP ligand to the two binding sites associated with the ATP-aptamer or the ATP-aptamer mutants. The simulated structures suggest that H-bonds between the ATP ligand and G₉ and G₁₁ bases, within one binding domain, and the π-π interactions between G₆ and the ATP purine moiety and the pyrimidine ring, in the second binding domain, control the affinity of binding interactions between the ATP ligand and the ATP-aptamer or ATP-aptamer mutant. Very good correlation between the computed  K_d values and the MST-derived K_d values is found. The ATP-aptamer mutant (consisting of A₁→ G, T₄ → C, T₁₂ → C, A₂₄ → G, and T₂₇ → C mutations) reveals superior binding affinities toward the ATP ligands ( K_d = 15 ± 1 μM) as compared to the binding affinity of ATP to the reported aptamer. These features of the mutant are supported by molecular dynamics simulations.

In situ generation of electrochemiluminescent DNA nanoflowers as a signal tag for mucin 1 detection based on a strategy of target and mimic target synchronous cycling amplification

A sensitive electrochemiluminescent (ECL) aptasensor consisting of a novel ECL signal tag of DNA nanoflowers (DNA NFs) and a highly efficient target conversion strategy for the MUC1 assay was developed, which not only increased the stability for luminophore loading, but also greatly improved the detection sensitivity.

Applications of Cancer Cell-Specific Aptamers in Targeted Delivery of Anticancer Therapeutic Agents

Aptamers are single-stranded oligonucleotides that specifically bind and interact with their corresponding targets, including proteins and cells, through unique three-dimensional structures. Numerous aptamers have been developed to target cancer biomarkers with high specificity and affinity, and some are employed as versatile guiding ligands for cancer-specific drug delivery and anti-cancer therapeutics. In this review, we list the aptamers that target tumor surface biomarkers and summarize the representative applications of aptamers as agonists and antagonists that activate anti-cancer and inactivate pro-cancer biomarkers, respectively. In addition, we describe applications of aptamer-drug or aptamer-oligonucleotide conjugates that can deliver therapeutic agents, including small interfering RNAs, micro RNAs, short hairpin RNAs, and chemotherapeutic molecules, to cancer cells. Moreover, we provide examples of aptamer- conjugated nano-vehicles, in which cancer-targeting oligonucleotide aptamers are conjugated with nano-vehicles such as liposomes, micelles, polymeric nanoparticles, and quantum dots. Conjugation of aptamers with anti-cancer drugs and nano-vehicles will facilitate innovative applications of aptamer-based cancer therapeutics.

Nanomedicine applications in women's health: state of the art

State-of-the-art applications of nanomedicine have the potential to revolutionize the diagnosis, prevention, and treatment of a range of conditions and diseases affecting women’s health. In this review, we provide a synopsis of potential applications of nanomedicine in some of the most dominant fields of women’s health: mental health, sexual health, reproductive medicine, oncology, menopause-related conditions and dementia. We explore published studies arising from in vitro and in vivo experiments, and clinical trials where available, to reveal novel and highly promising therapeutic applications of nanomedicine in these fields. For the first time, we summarize the growing body of evidence relating to the use of nanomaterials as experimental tools for the detection, prevention, and treatment of significant diseases and conditions across the life course of a cisgender woman, from puberty to menopause; revealing the far-reaching and desirable theoretical impact of nanomedicine across different medical disciplines. We also present an overview of potential concerns regarding the therapeutic applications of nanomedicine and the factors currently restricting the growth of applied nanomedicine.

Oligonucleotide aptamers against tyrosine kinase receptors: Prospect for anticancer applications

Transmembrane receptor tyrosine kinases (RTKs) play crucial roles in cancer cell proliferation, survival, migration and differentiation. Area of intense research is searching for effective anticancer therapies targeting these receptors and, to date, several monoclonal antibodies and small-molecule tyrosine kinase inhibitors have entered the clinic. However, some of these drugs show limited efficacy and give rise to acquired resistance. Emerging highly selective compounds for anticancer therapy are oligonucleotide aptamers that interact with their targets by recognizing a specific three-dimensional structure. Because of their nucleic acid nature, the rational design of advanced strategies to manipulate aptamers for both diagnostic and therapeutic applications is greatly simplified over antibodies. In this manuscript, we will provide a comprehensive overview of oligonucleotide aptamers as next generation strategies to efficiently target RTKs in human cancers.

Specific detection of cancer cells through aggregation-induced emission of a light-up bioprobe

A cancer cell specific aptamer was labeled with an aggregation-induced emission (AIE) probe for the first time. Using it as a light-up bioprobe, a specific cancer cell detection method is developed.

Recent applications of the combination of mesoporous silica nanoparticles with nucleic acids: development of bioresponsive devices, carriers and sensors

The discovery and control of the biological roles mediated by nucleic acids have turned them into a powerful tool for the development of advanced biotechnological materials. Such is the importance of these gene-keeping biomacromolecules that even nanomaterials have succumbed to the claimed benefits of DNA and RNA. Currently, there could be found in the literature a practically intractable number of examples reporting the use of combination of nanoparticles with nucleic acids, so boundaries are demanded. Following this premise, this review will only cover the most recent and powerful strategies developed to exploit the possibilities of nucleic acids as biotechnological materials when in combination with mesoporous silica nanoparticles. The extensive research done on nucleic acids has significantly incremented the technological possibilities for those biomacromolecules, which could be employed in many different applications, where substrate or sequence recognition or modulation of biological pathways due to its coding role in living cells are the most promising. In the present review, the chosen counterpart, mesoporous silica nanoparticles, also with unique properties, became a reference material for drug delivery and biomedical applications due to their high biocompatibility and porous structure suitable for hosting and delivering small molecules. Although most of the reviews dealt with significant advances in the use of nucleic acid and mesoporous silica nanoparticles in biotechnological applications, a rational classification of these new generation hybrid materials is still uncovered. In this review, there will be covered promising strategies for the development of living cell and biological sensors, DNA-based molecular gates with targeting, transfection or silencing properties, which could provide a significant advance in current nanomedicine.

Improved Detection of HER2 by a Quasi-Targeted Proteomics Approach Using Aptamer–Peptide Probe and Liquid Chromatography–Tandem Mass Spectrometry

BACKGROUND

Human epidermal growth factor receptor 2 (HER2)-positive breast cancer is a particularly aggressive type of the disease. To date, much evidence has indicated that accurate HER2 status detection is crucial for prognosis and treatment strategy selection. Thus, bioanalytical techniques for early and accurate detection of HER2 have the potential to improve patient care. Currently, the widely used immunohistochemical staining normally has problems with reproducibility and lack of standardization, resulting in poor concordance between laboratories. Aptamers are a good alternative, but the extent of their use in quantitative analysis of HER2 is limited because of the lack of effective detection methods.

METHODS

We developed a quasi-targeted proteomics assay and converted the HER2 signal into the mass response of reporter peptide by a combination of aptamer–peptide probe and LC-MS/MS.

RESULTS

The selected aptamer–peptide probe consisted of aptamer HB5 and the substrate peptide GDKAVLGVDPFR that contained the reporter peptide AVLGVDPFR. After characterization of this newly synthesized probe (e.g., conjugation efficiency, stability, binding affinity, specificity, and digestion efficiency), probe binding and trypsin shaving conditions were optimized. The resulting limit of quantification for HER2 was 25 pmol/L. Then, the quasi-targeted proteomics assay was applied to determine the HER2 concentrations in the HER2-positive breast cancer cells BT474 and SK-BR-3, the HER2-negative breast cancer cells MDA-MB-231 and MCF-7, and 36 pairs of human breast primary tumors and adjacent normal tissue samples. The results were highly concordant with those obtained by immunohistochemistry with reflex testing by fluorescent in situ hybridization.

CONCLUSIONS

Quasi-targeted proteomics can be a quantitative alternative for HER2 detection.

Aptamer Combined with Fluorescent Silica Nanoparticles for Detection of Hepatoma Cells

PURPOSE

The purpose of this study is to develop a simple, effective method to label hepatoma cells with aptamers and then detect them using fluorescent silica nanoparticles (FSNPs).

METHOD

Streptavidin was conjugated to carboxyl-modified fluorescein isothiocyanate (FITC)-doped silica nanoparticles which were prepared by the reverse microemulsion method. The resulting streptavidin-conjugated fluorescent silica nanoparticles (SA-FSNPs) were mixed with hepatoma cells that had been labeled with biotin-conjugated aptamer TLS11a (Bio-TLS11a). The specificity and sensitivity of the nanoprobes were assessed using flow cytometry and fluorescence microscopy. Their toxicity was assessed in normal human liver cell cultures using the MTT assay, as well as in nude mice using immunohistochemistry.

RESULTS

SA-FSNPs showed uniform size and shape, and fluorescence properties of them was similar to the free FITC dye. SA-FSNPs were able to detect aptamer-labeled hepatoma cells with excellent specificity and good sensitivity, and they emitted strong, photobleach-resistant fluorescent signal. SA-FSNPs showed no significant toxic effects in vitro or in vivo.

CONCLUSION

The combination of biotin-conjugated aptamers and SA-FSNPs shows promise for sensitive detection of hepatoma cells, and potentially of other tumor cell types as well.

Aptamer selection and applications for breast cancer diagnostics and therapy

Aptamers are short non-coding, single-stranded oligonucleotides (RNA or DNA) developed through Systematic Evolution of Ligands by Exponential enrichment (SELEX) in vitro. Similar to antibodies, aptamers can bind to specific targets with high affinity, and are considered promising therapeutic agents as they have several advantages over antibodies, including high specificity, stability, and non-immunogenicity. Furthermore, aptamers can be produced at a low cost and easily modified, and are, therefore, called "chemical antibodies". In the past years, a variety of aptamers specifically bound to both breast cancer biomarkers and cells had been selected. Besides, taking advantage of nanomaterials, there were a number of aptamer-nanomaterial conjugates been developed and widely investigated for diagnostics and targeted therapy of breast cancer. In this short review, we first present a systematical review of various aptamer selection methods. Then, various aptamer-based diagnostic and therapeutic strategies of breast cancer were provided. Finally, the current problems, challenges, and future perspectives in the field were thoroughly discussed.