Design of DNA Aptamer-Functionalized Magnetic Short Nanofibers for Efficient Capture and Release of Circulating Tumor Cells

Gold Nanoparticle-Based Microfluidic Chips for Capture and Detection of Circulating Tumor Cells

Liquid biopsy has progressed to its current use to diagnose and monitor cancer. Despite the recent advances in investigating cancer detection and diagnosis strategies, there is still a room for improvements in capturing CTCs. We developed an efficient CTC detection system by integrating gold nanoparticles with a microfluidic platform, which can achieve CTC capture within 120 min. Here, we report our development of a simple and effective way to isolate CTCs using antibodies attached on gold nanoparticles to the surface of a lateral filter array (LFA) microdevice. Our method was optimized using three pancreatic tumor cell lines, enabling the capture with high efficiency (90% ± 3.2%). The platform was further demonstrated for isolating CTCs from patients with metastatic pancreatic cancer. Our method and platform enables the production of functionalized, patterned surfaces that interact with tumor cells, enhancing the selective capture of CTCs for biological assays.

Recent progress in aptamer-based microfluidics for the detection of circulating tumor cells and extracellular vesicles

Liquid biopsy is a technology that exhibits potential to detect cancer early, monitor therapies, and predict cancer prognosis due to its unique characteristics, including noninvasive sampling and real-time analysis. Circulating tumor cells (CTCs) and extracellular vesicles (EVs) are two important components of circulating targets, carrying substantial disease-related molecular information and playing a key role in liquid biopsy. Aptamers are single-stranded oligonucleotides with superior affinity and specificity, and they can bind to targets by folding into unique tertiary structures. Aptamer-based microfluidic platforms offer new ways to enhance the purity and capture efficiency of CTCs and EVs by combining the advantages of microfluidic chips as isolation platforms and aptamers as recognition tools. In this review, we first briefly introduce some new strategies for aptamer discovery based on traditional and aptamer-based microfluidic approaches. Then, we subsequently summarize the progress of aptamer-based microfluidics for CTC and EV detection. Finally, we offer an outlook on the future directional challenges of aptamer-based microfluidics for circulating targets in clinical applications.

Dynamic DNA Nanostructures for Cell Manipulation

Dynamic DNA nanostructures are DNA nanostructures with reconfigurable elements that can undergo structural transformations in response to specific stimuli. Thus, anchoring dynamic DNA nanostructures on cell membranes is an attractive and promising strategy for well-controlled cell manipulation. Here, we review the latest progress in dynamic DNA nanostructures for cell manipulation. Commonly used mechanisms for dynamic DNA nanostructures are first introduced. Subsequently, we summarize the anchoring strategies for dynamic DNA nanostructures on cell membranes and list possible applications (including programming cell membrane receptors, controlling ligand activity and drug delivery, capturing and releasing cells, and assembling cells into clusters). Finally, insights into the remaining challenges are presented.

Noninvasive Optical Isolation and Identification of Circulating Tumor Cells Engineered by Fluorescent Microspheres

Circulating tumor cells (CTCs) are rare, meaning that current isolation strategies can hardly satisfy efficiency and cell biocompatibility requirements, which hinders clinical applications. In addition, the selected cells require immunofluorescence identification, which is a time-consuming and expensive process. Here, we developed a method to simultaneously separate and identify CTCs by the integration of optical force and fluorescent microspheres. Our method achieved high-purity separation of CTCs without damage through light manipulation and avoided additional immunofluorescence staining procedures, thus achieving rapid identification of sorted cells. White blood cells (WBCs) and CTCs are similar in size and density, which creates difficulties in distinguishing them optically. Therefore, fluorescent PS microspheres with high refractive index (RI) are designed here to capture the CTCs (PS-CTCs) and increase the average index of refraction of PS-CTCs. In optofluidic chips, PS-CTCs were propelled to the collection channel from the sample mixture, under the radiation of light force. Cells from the collection outlet were easily identified under a fluorescence microscope due to the fluorescence signals of PS microspheres. This method provides an approach for the sorting and identification of CTCs, which holds great potential for clinical applications in early diagnosis of disease.

Preparation and investigation of a novel iodine-based visible polyvinyl alcohol embolization material

Polyvinyl alcohol (PVA) embolization particles, currently used in clinical practice, have good expansibility and are capable of permanent embolization. However, the lack of adhesion of embolization particles contributes to facilitated recanalization after embolization, while the lack of visualization facilitates misembolization. At present, embolization materials with good expansion, adhesion, and visualization potential are urgently required in clinical practice. Here, we report the development of PVA/gelatin/iohexol (I) fiber blocks as a novel embolization material for liver embolization in rats. In our work, electrospun PVA/gelatin/I nanofibrous mats were first prepared, homogenized, centrifuged in a gradient manner, and freeze-dried to obtain fiber blocks (fiber diameter ​= ​296.2 ​± ​74.23 ​nm, length 99.6 ​± ​17.0 ​μm ​× ​width 46.9 ​± ​13.3 ​μm). The fiber blocks exhibited excellent cytocompatibility and hemocompatibility. Fiber blocks with a PVA/gelatin/I mass ratio of 8:2:10 were selected due to their excellent expansibility and adhesive properties. The PVA/gelatin/I fiber blocks display excellent liver embolic effects and computed tomography (CT) imaging potential due to a combination of the following characteristics: expansibility of PVA and gelatin, adhesive property of gelatin, and CT imaging potential of I. The developed fiber block material is an embolic material that may potentially be used in interventional medicine.

A review of enrichment methods for circulating tumor cells: from single modality to hybrid modality

Circulating tumor cell (CTC) analysis as a liquid biopsy can be used for early diagnosis of cancer, evaluating cancer progression, and assessing treatment efficacy. The enrichment of CTCs from patient blood is important for CTC analysis due to the extreme rarity of CTCs. This paper updates recent advances in CTC enrichment methods. We first review single-modality methods, including biophysical and biochemical methods. Hybrid-modality methods, combining at least two single-modality methods, are gaining increasing popularity for their improved performance. Then this paper reviews hybrid-modality methods, which are categorized into integrated and sequenced hybrid-modality methods. The state of the art indicates that the CTC capture efficiencies of integrated hybrid-modality methods can reach 85% or higher by taking advantage of the superimposed and enhanced capture effects from multiple single-modality methods. Moreover, a hybrid method integrating biophysical with biochemical methods is characterized by both high processing rate and high specificity.

Engineered multifunctional metal-phenolic nanocoatings for label-free capture and "self-release" of heterogeneous circulating tumor cells

Immunomagnetic beads have been widely explored as an important analytical tool for the rapid and sensitive detection of circulating tumor cells (CTCs). However, their clinical application is seriously hindered by the tedious preparation procedures and heterogeneous nature of CTCs. To this end, a designed multifunctional platform named Fe₃O₄@TA/Cu^II superparamagnetic nanoparticles (SPMNPs) is expected to have the following features: (i) the formation of a tannic acid-copper (II) ion (TA/Cu^II) coating which could be accomplished by a one-step method is very simple; (ii) the TA/Cu^II coating shows high affinity for heterogeneous CTCs and good resistance to nonspecific adhesion of blood cells; (iii) "self-release" of the captured cells could be achieved as the TA/Cu^II coating gradually degrades in the cell culture environment without any additional interventions. Therefore, the resulting Fe₃O₄@TA/Cu^II SPMNPs could capture various CTCs (MCF-7, HepG2 and HeLa cells) with different expression levels of the epithelial cell adhesion molecule (EpCAM). And the capture efficiency and cell purity can reach 88% and 87%, respectively. In addition, 68% of the captured cells are self-released after 6 h of incubation and most of the released cells show high cell proliferation activity. In particular, Fe₃O₄@TA/Cu^II SPMNPs can successfully detect 1-13 CTCs from 1 mL of blood of 14 patients with 6 types of cancers. Hence, we expect that the as-prepared Fe₃O₄@TA/Cu^II SPMNPs with simple, efficient, and universal yet cost-efficient characteristics could act as a promising analytical tool for clinical CTC detection.

Dual-recognition colorimetric sensing of thrombin based on surface-imprinted aptamer-Fe3O4

Thrombin plays an essential role in blood coagulation and some physiological and pathological processes. The convenient, rapid, sensitive, and specific detection of thrombin is of great significance in clinical research and diagnosis. Herein, surface molecularly imprinted polymer (MIP) was modified on aptamer-functionalized Fe3O4 nanoparticles (MIP-aptamer-Fe3O4 NP) for thrombin colorimetric assay by taking advantage of the peroxidase-like activity of Fe3O4 NP. With the adsorption of thrombin into imprinted cavities, the exposed surface area of Fe3O4 NP decreased, causing a decrease in its peroxidase-like activity toward 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2. On the other hand, the reductive amino acids on the thrombin surface also impeded the oxidation of TMB. Both phenomena caused the light blue color of the sensing solution. Thus, a specifically sensitive colorimetric approach for the visual detection of thrombin was proposed with a linear range and limit of detection of 108.1 pmol L-1-2.7 × 10-5 mol L-1 and 27.8 pmol L-1, respectively. Moreover, due to the double recognition elements of MIP and aptamer, the prepared MIP-aptamer-Fe3O4 NP showed higher selectivity to thrombin than that based on only one recognition element. It is worth noting that no special property (e.g. electrochemical or fluorescence activity) of the template was required in this work. Thus, more template molecules can be easily, selectively, and sensitively detected based on the proposed MIP-aptamer-mimic enzyme colorimetric sensing strategy.

Selective Adhesion and Switchable Release of Breast Cancer Cells via Hyaluronic Acid Functionalized Dual Stimuli-Responsive Microgel Films

The detection of tumor cells from liquid biopsy samples is of critical importance for early cancer diagnosis, malignancy assessment, and treatment. In this work, coatings of hyaluronic acid (HA)-functionalized dual-stimuli responsive poly(N-isopropylacrylamide) (PNIPAM) microgels are used to study the specificity of breast cancer cell binding and to assess cell friendly release mechanisms for further diagnostic procedures. The microgels are established by straightforward precipitation polymerization with amine bearing comonomers and postfunctionalization with a UV-labile linker that covalently binds HA to the microgel network. Well-defined microgel coatings for cell binding are established via simple physisorption and annealing. The HA-presenting PNIPAM microgel films are shown to specifically adhere CD44 expressing breast cancer cell lines (MDA-MB-231 and MCF-7), where an increase in adhesion correlates with higher CD44 expression and HA functionalization. Upon cooling below the lower critical solution temperature of PNIPAM microgels, the cells could be released; however, 10-30% of the cells still remained on the surface even after prolonged cooling and mild mechanical agitation. A complete cell release is achieved after applying the light stimulus by short UV treatment cleaving HA units from the microgels. Owing to the comparatively straightforward preparation procedures, such dual-responsive microgel films could be considered for the effective capture, release, and diagnostics of tumor cells.

Elucidating Raman Image-Guided Differential Recognition of Clinically Confirmed Grades of Cervical Exfoliated Cells by Dual Biomarker-Appended SERS-Tag

Ultrasensitive detection of cancer biomarkers via single-cell analysis through Raman imaging is an impending approach that modulates the possibility of early diagnosis. Cervical cancer is one such type that can be monitored for a sufficiently long period toward invasive cancer phenotype. Herein, we report a surface-enhanced Raman scattering (SERS) nanotag (SERS-tag) for the simultaneous detection of p16/K-i67, a dual biomarker persisting in the progression of squamous cell carcinoma of human cervix. A nanoflower-shaped SERS-tag, constituted of hybrid gold nanostar with silver tips to achieve maximum fingerprint enhancement from the incorporated reporter molecule, was further functionalized with the cocktail monoclonal antibodies against p16/K-i67. The recognition by the SERS-tag was first validated in cervical squamous cell carcinoma cell line SiHa as a foot-step study and subsequently implemented to different grades of clinically confirmed exfoliated cells including normal cell (NC), high-grade intra-epithelial lesion (HC), and squamous cell carcinoma (CC) samples of the cervix. Precise Raman mapped images were constituted based on the average intensity gradient of the signature Raman peaks arising from different grades of exfoliated cells. We observed a distinct intensity hike of around 10-fold in the single dysplastic HC and CC samples in comparison to NC specimen, which clearly justify the prevalence of p16/Ki-67. The synthesized probe is able to map the abnormal cells within 20 min with high reproducibility and stability for 1 mm × 1 mm mapping area with good contrast. Amidst the challenges in Raman image-guided modality, the technique was further complemented with the gold standard immunocytochemistry (ICC) dual staining analysis. Even though both are time-consuming techniques, tedious steps can be avoided and real-time readout can be achieved using the SERS mapping unlike immunocytochemistry technique. Therefore, the newly developed Raman image-guided SERS imaging emphasizes the approach of uplifting of SERS in practical utility with further improvement for clinical applications for cervical cancer detection in future.

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.

Functional Aptamer-Embedded Nanomaterials for Diagnostics and Therapeutics

In the past decades, various nanomaterials with unique properties have been explored for bioapplications. Meanwhile, aptamers, generated from the systematic evolution of ligands by exponential enrichment technology, are becoming an indispensable element in the design of functional nanomaterials because of their small size, high stability, and convenient modification, especially endowing nanomaterials with recognition capability to specific targets. Therefore, the incorporation of aptamers into nanomaterials offers an unprecedented opportunity in the research fields of diagnostics and therapeutics. Here, we focus on recent advances in aptamer-embedded nanomaterials for bioapplications. First, we briefly introduce the properties of nanomaterials that can be functionalized with aptamers. Then, the applications of aptamer-embedded nanomaterials in cellular analysis, imaging, targeted drug delivery, gene editing, and cancer diagnosis/therapy are discussed. Finally, we provide some perspectives on the challenges and opportunities that have arisen from this promising area.

Chemo-specific designs for the enumeration of circulating tumor cells: advances in liquid biopsy

Advanced materials and chemo-specific designs at the nano/micrometer-scale have ensured revolutionary progress in next-generation clinically relevant technologies. For example, isolating a rare population of cells, like circulating tumor cells (CTCs) from the blood amongst billions of other blood cells, is one of the most complex scientific challenges in cancer diagnostics. The chemical tunability for achieving this degree of exceptional specificity for extra-cellular biomarker interactions demands the utility of advanced entities and multistep reactions both in solution and in the insoluble state. Thus, this review delineates the chemo-specific substrates, chemical methods, and structure-activity relationships (SARs) of chemical platforms used for isolation and enumeration of CTCs in advancing the relevance of liquid biopsy in cancer diagnostics and disease management. We highlight the synthesis of cell-specific, tumor biomarker-based, chemo-specific substrates utilizing functionalized linkers through chemistry-based conjugation strategies. The capacity of these nano/micro substrates to enhance the cell interaction specificity and efficiency with the targeted tumor cells is detailed. Furthermore, this review accounts for the importance of CTC capture and other downstream processes involving genotypic and phenotypic CTC analysis in real-time for the detection of the early onset of metastases progression and chemotherapy treatment response, and for monitoring progression free-survival (PFS), disease-free survival (DFS), and eventually overall survival (OS) in cancer patients.

A Comprehensive Review of the Covalent Immobilization of Biomolecules onto Electrospun Nanofibers

Biomolecule immobilization has attracted the attention of various fields such as fine chemistry and biomedicine for their use in several applications such as wastewater, immunosensors, biofuels, et cetera. The performance of immobilized biomolecules depends on the substrate and the immobilization method utilized. Electrospun nanofibers act as an excellent substrate for immobilization due to their large surface area to volume ratio and interconnectivity. While biomolecules can be immobilized using adsorption and encapsulation, covalent immobilization offers a way to permanently fix the material to the fiber surface resulting in high efficiency, good specificity, and excellent stability. This review aims to highlight the various covalent immobilization techniques being utilized and their benefits and drawbacks. These methods typically fall into two categories: (1) direct immobilization and (2) use of crosslinkers. Direct immobilization techniques are usually simple and utilize the strong electrophilic functional groups on the nanofiber. While crosslinkers are used as an intermediary between the nanofiber substrate and the biomolecule, with some crosslinkers being present in the final product and others simply facilitating the reactions. We aim to provide an explanation of each immobilization technique, biomolecules commonly paired with said technique and the benefit of immobilization over the free biomolecule.

Recent advances in development of dendritic polymer-based nanomedicines for cancer diagnosis

Dendritic polymers have highly branched three-dimensional architectures, the fourth type apart from linear, cross-linked, and branched one. They possess not only a large number of terminal functional units and interior cavities, but also a low viscosity with weak or no entanglement. These features endow them with great potential in various biomedicine applications, including drug delivery, gene therapy, tissue engineering, immunoassay and bioimaging. Most review articles related to bio-related applications of dendritic polymers focus on their drug or gene delivery, while very few of them are devoted to their function as cancer diagnosis agents, which are essential for cancer treatment. In this review, we will provide comprehensive insights into various dendritic polymer-based cancer diagnosis agents. Their classification and preparation are presented for readers to have a precise understanding of dendritic polymers. On account of physical/chemical properties of dendritic polymers and biological properties of cancer, we will suggest a few design strategies for constructing dendritic polymer-based diagnosis agents, such as active or passive targeting strategies, imaging reporters-incorporating strategies, and/or internal stimuli-responsive degradable/enhanced imaging strategies. Their recent applications in in vitro diagnosis of cancer cells or exosomes and in vivo diagnosis of primary and metastasis tumor sites with the aid of single/multiple imaging modalities will be discussed in great detail. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Diagnostic Tools > in vivo Nanodiagnostics and Imaging Diagnostic Tools > in vitro Nanoparticle-Based Sensing.

Immunomagnetic separation of circulating tumor cells with microfluidic chips and their clinical applications

Circulating tumor cells (CTCs) are tumor cells detached from the original lesion and getting into the blood and lymphatic circulation systems. They potentially establish new tumors in remote areas, namely, metastasis. Isolation of CTCs and following biological molecular analysis facilitate investigating cancer and coming out treatment. Since CTCs carry important information on the primary tumor, they are vital in exploring the mechanism of cancer, metastasis, and diagnosis. However, CTCs are very difficult to separate due to their extreme heterogeneity and rarity in blood. Recently, advanced technologies, such as nanosurfaces, quantum dots, and Raman spectroscopy, have been integrated with microfluidic chips. These achievements enable the next generation isolation technologies and subsequent biological analysis of CTCs. In this review, we summarize CTCs' separation with microfluidic chips based on the principle of immunomagnetic isolation of CTCs. Fundamental insights, clinical applications, and potential future directions are discussed.

Biocompatible chitosan-modified core-shell Fe3O4 nanocomposites for exigent removal of blood lactic acid

Excess lactic acid in blood will lead to hyperlactatemia, which is frequently detected in critically ill patients admitted to the intensive care. Reducing the blood lactic acid content using acute treatments becomes particularly important for bringing a patient out of danger. Traditional treatments often fail in case of malfunctioning of a patients’ metabolism. Herein, nanotechnology was introduced to remove blood lactic acid independent of metabolism. In this work, chitosan was employed as the shell to adsorb lactic acid, and Fe3O4 nanoparticles were employed as the core to enable proper magnetic separation property. Our data showed that core–shell nanocomposites (NCs) had an exigent and efficient adsorption behavior. Furthermore, they could be easily separated from blood plasma by magnetic separation. Thus, the good hemocompatibility and cytocompatibility indicated that of core–shell NCs hold great potential in lactic acid removal for emergent hyperlactatemia treatment.

Anti-Escherichia coli Functionalized Silver-Doped Carbon Nanofibers for Capture of E. coli in Microfluidic Systems

Silver-doped carbon nanofibers (SDCNF) are used as the base material for the selective capture of Escherichia coli in microfluidic systems. Fibers were spun in a glovebox with dry atmosphere maintained by forced dry air pumped through the closed environment. This affected the evaporation rate of the solvent during the electrospinning process and the distribution of silver particles within the fiber. Antibodies are immobilized on the surface of the silver-doped polyacrylonitrile (PAN) based carbon nanofibers via a three-step process. The negatively charged silver particles present on the surface of the nanofibers provide suitable sites for positively charged biotinylated poly-(L)-lysine-graft-poly-ethylene-glycol (PLL-g-PEG biotin) conjugate attachment. Streptavidin and a biotinylated anti-E. coli antibody were then added to create anti-E. coli surface functionalized (AESF) nanofibers. Functionalized fibers were able to immobilize up to 130 times the amount of E. coli on the fiber surface compared to neat silver doped fibers. Confocal images show E. coli remains immobilized on fiber mat surface after extensive rinsing showing the bacteria is not simply a result of non-specific binding. To demonstrate selectivity and functionalization with both gram negative and gram-positive antibodies, anti-Staphylococcus aureus surface functionalized (ASSF) nanofibers were also prepared. Experiments with AESF performed with Staphylococcus aureus (S. aureus) and ASSF with E. coli show negligible binding to the fiber surface showing the selectivity of the functionalized membranes. This surface functionalization can be done with a variety of antibodies for tunable selective pathogen capture.