Aminophenylboronic Acid-Functionalized Thorny-Trap-Shaped Monolayer Microarray for Efficient Capture and Release of Circulating Tumor Cells

A multilocus-dendritic boronic acid functionalized magnetic nanoparticle for capturing circulating tumor cells in the peripheral blood of mice with metastatic breast cancer

BACKGROUND

Dynamic fluctuation of circulating tumor cells (CTCs) can serve as an indicator of tumor progression. However, the sensitive isolation of CTCs remains extremely challenging due to their rarity and heterogeneity. Against this dilemma, dendritic boronic acid-modified magnetic nanoparticles (MNPs) were prepared in this study, and polyethyleneimine (PEI) was utilized as a scaffold to significantly increase the number of boronic acid moieties. Then the novel developed material was applied to monitor the number of CTCs in mice with metastatic breast cancer to evaluate the therapeutic effects of matrine (Mat), doxorubicin (Dox), and Mat in combination with Dox.

RESULTS

Compared to the low binding capacity of a single boronic acid ligand, dendritic boronic acid shows enhanced sensitivity in binding to sialic acid (SA), which is overexpressed in CTCs. The results showed that the capture efficiency of this modified material could achieve 94.7% and successfully captured CTCs in blood samples from mice with metastatic breast cancer. The CTC counts were consistent with the results of the pathologic examination, demonstrating the reliability and utility of the method.

SIGNIFICANCE

The dendritic boronic acid nanomaterials prepared in this study showed high specificity, sensitivity, and accuracy for cancer cell capture. The approach is expected to provide new insights into cancer diagnosis, personalized therapy, and optimization of treatment regimens.

Biosensors with Boronic Acid-Based Materials as the Recognition Elements and Signal Labels

It is of great importance to have sensitive and accurate detection of cis-diol-containing biologically related substances because of their important functions in the research fields of metabolomics, glycomics, and proteomics. Boronic acids can specifically and reversibly interact with 1,2- or 1,3-diols to form five or six cyclic esters. Based on this unique property, boronic acid-based materials have been used as synthetic receptors for the specific recognition and detection of cis-diol-containing species. This review critically summarizes the recent advances with boronic acid-based materials as recognition elements and signal labels for the detection of cis-diol-containing biological species, including ribonucleic acids, glycans, glycoproteins, bacteria, exosomes, and tumor cells. We also address the challenges and future perspectives for developing versatile boronic acid-based materials with various promising applications.

New Method for Counting and Picking Out Single Circulating Tumor Cells from Microliter-Volume Samples for Tumor Progression Surveillance and Single-Cell Heterogeneity Analysis

Circulating tumor cells (CTCs) are crucial in tumor progression and metastasis, but the knowledge of their roles grows slowly at single-cell levels. Characterizing the rarity and fragility of CTCs by nature, highly stable and efficient single-CTC sampling methods are still lacking, which impedes the development of single-CTC analysis. Herein, an improved, capillary-based single-cell sampling (SiCS) method, the so-called bubble-glue single-cell sampling (bubble-glue SiCS), is introduced. Benefiting from the characteristic that the cells tend to adhere to air bubbles in the solution, single cells can be sampled with bubbles as low as 20 pL with a self-designed microbubble-volume-controlled system. Benefiting from the excellent maneuverability, single CTCs are sampled directly from 10 μL volume of real blood samples after fluorescent labeling. Meanwhile, over 90% of the CTCs obtained survived and well proliferated after the bubble-glue SiCS process, which showed considerable superiority for downstream single-CTC profiling. Furthermore, a highly metastatic breast cancer model of the 4T1 cell line in vivo was employed for the real blood sample analysis. Increases in CTC numbers were observed during the tumor progression process, and significant heterogeneities among individual CTCs were discovered. In all, we propose a novel avenue for target SiCS and provide an alternative technique route for CTC separation and analysis.

Facile Preparation of Three-Dimensional Wafer with Interconnected Porous Structure for High-Performance Capture and Nondestructive Release of Circulating Tumor Cells

Efficient isolation and downstream bioinformation analysis of circulating tumor cells (CTCs) in whole blood contribute to the early diagnosis of cancer and investigation of cancer metastasis. However, the separation and release of CTCs remain a great challenge due to the extreme rarity of CTCs and severe interference from other cells in complex clinical samples. Herein, we developed a low-cost and easy-to-fabricate aptamer-functionalized wafer with a three-dimensional (3D) interconnected porous structure by grafting polydopamine (PDA), poly(ethylene glycol) (PEG), and aptamer in sequence (Ni@PDA-PEG-Apt) for the capture and release of CTCs. The Ni@PDA-PEG-Apt wafer integrated the features of Ni foam with a 3D interconnected porous structure offering enough tunnels for cells to flow through and enhancing aptamer-cell contact frequency, the spacer PEG with flexible and high hydrophilic property increasing anti-interference ability and providing the wafer with more binding sites for aptamer, which result in an enhanced capture specificity and efficiency for CTCs. Because of these advantages, the Ni@PDA-PEG-Apt wafer achieved a high capture efficiency of 78.25%. The captured cancer cells were mildly released by endonuclease with up to 61.85% efficiency and good proliferation. Furthermore, tumor cells were injected into mice and experienced circulation in vivo. In blood samples after circulation, 65% of target tumor cells can be efficiently captured by the wafer, followed by released and recultured cells with high viability. Further downstream metabolomics analysis showed that target cancer cells remained with high biological activity and can be well separated from MCF-10A cells based on metabolic profiles by the PCA analysis, indicating the great potential of our strategy for further research on the progression of cancer metastasis. Notably, not only is the wafer cheap with a cost of only 3.58 U.S. dollars and easily prepared by environmental-friendly reagents but also the process of capturing and releasing tumor cells can be completed within an hour, which is beneficial for large-scale clinical use in the future.

A universal monoclonal antibody-aptamer conjugation strategy for selective non-invasive bioparticle isolation from blood on a regenerative microfluidic platform

Simultaneous isolation of various circulating tumor cell (CTC) subtypes from whole blood is useful in cancer diagnosis and prognosis. Microfluidic affinity separation devices are promising for CTC separation because of their high throughput capacity and automatability. However, current affinity agents, such as antibodies (mAbs) and aptamers (Apts) alone, are still suboptimal for efficient, consistent, and versatile cell analysis. By introducing a hybrid affinity agent, i.e., an aptamer-antibody (Apt-mAb) conjugate, we developed a universal and regenerative microchip with high efficiency and non-invasiveness in the separation and profiling of various CTCs from blood. The Apt-mAb conjugate consists of a monoclonal antibody that specifically binds the target cell receptor and a surface-bound aptamer that recognizes the conserved Fc region of the mAb. The aptamer then indirectly links the surface functionalization of the microfluidic channels to the mAbs. This hybrid affinity agent and the microchip platform may be widely useful for various bio-particle separations in different biological matrices. Further, the regeneration capability of the microchip improves data consistency between multiple uses and minimizes plastic waste while promoting environmental sustainability. STATEMENT OF SIGNIFICANCE: A hybrid affinity agent, Apt-mAb, consisting of a universal aptamer (Apt) that binds the conserved Fc region of monoclonal antibodies (mAbs) was developed. The invented nano-biomaterial combines the strengths and overcomes the weakness of both Apts and mAbs, thus changing the paradigm of affinity separation of cell subtypes. When Apt-mAb was used to fabricate microfluidic chips using a "universal screwdriver" approach, the microchip could be easily tuned to bind any cell type, exhibiting great universality. Besides high sensitivity and selectivity, the superior regenerative capacity of the microchips makes them reusable, which provides improved consistency and repeatability in cell profiling and opens a new approach towards in vitro diagnostic point-of-care testing devices with environmental sustainability and cost-effectiveness.

Fabrication of a Polyvalent Aptamer Network on an Electrode Surface for Capture and Analysis of Circulating Tumor Cells

Capture and analysis of circulating tumor cells (CTCs) from complex matrixes is pivotal for the prediction of cancer metastasis and personalized treatment of cancer. Herein, we propose a strategy for CTC capture by design and fabrication of a polyvalent aptamer network on an electrode surface, which can be further used for the sensitive analysis of CTCs. In our design, the polyvalent aptamer network, which is constructed via a rolling circle amplification reaction, can significantly enhance the cell-binding abilities. Meanwhile, tetrahedral DNA structures previously assembled on the electrode surface will promote the spatial orientation and reduce the steric hindrance effect of the cell capture, thus improving the cell capture efficiency. Importantly, a detectable electrochemical signal can be obtained without additional signal probes by means of target-induced allostery of the DNA hairpin structures. Further studies reveal that the electrochemical response is proportional to the logarithm of the CTC abundance ranging from 10² to 5 × 10⁴ cell mL^-1 with a low limit of detection of 23 cell mL^-1. Moreover, the proposed capture strategy exhibits excellent stability and anti-interference in human whole blood, indicating its promising potential in clinical diagnosis.

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.

A light-induced hydrogel responsive platform to capture and selectively isolate single circulating tumor cells

Isolation of circulating tumor cells (CTCs) from patients is a challenge due to the rarity of CTCs. Recently, various platforms to capture and release CTCs for downstream analysis have been developed. However, most of the reported release methods provide external stimuli to release all captured cells, which lead to lack of specificity in the pool of collected cells, and the external stimuli may affect the activity of the released cells. Here, we presented a simple method for single-cell recovery to overcome the shortcomings, which combined the nanostructures with a photocurable hydrogel, chondroitin sulfate methacryloyl (CSMA). In brief, we synthesized gelatin nanoparticles (Gnps) and modified them on flat glass (Gnp substrate) for the specific capture of CTCs. A 405 nm laser was projected onto the selected cells, and then CSMA was cured to encapsulate the selected CTCs. Unselected cells were removed with MMP-9 enzyme solution, and selected CTCs were recovered using a microcapillary. Finally, the photocurable hydrogel-encapsulated cells were analyzed by nucleic acid detection. In addition, the results suggested that the isolation platform showed good biocompatibility and successfully achieved the isolation of selected cells. In summary, our light-induced hydrogel responsive platform holds certain potential for clinical applications.

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.

Pollen-like silica nanoparticles as a nanocarrier for tumor targeted and pH-responsive drug delivery

Aptamer modified hollow silica nanoparticles with pollen structure (plSP@aptamer) were synthesized and used as a nanocarrier for tumor targeted and pH-responsive drug delivery. The 292 ± 14 nm interior void in diameter together with 11.8 nm surface pore size of plSP@aptamer nanoparticles contributed to a high drug loading efficiency of 0.509 g g^-1. Furthermore, the drug delivery system was pH-responsive, and the releasing efficiency was up to 87.5% at pH of 5. The special spikes of this plSP@aptamer nanoparticles acted as "entry claws" to enhanced the interaction between cell and drug nanocarriers and then increased the internalization rate of drug vehicles. The cell uptake assay suggested that most of doxorubicin (DOX)@plSP@aptamer nanoparticles can escape form lysosome and located in nuclei of MCF-7 cells. The targeted performance testing showed that almost no DOX@plSP@aptamer were internalized by normal cells, indicating a high specificity of our drug vehicles. The cytotoxicity of nanoparticles was also investigated, the plSP@aptamer particles had excellent biocompatibility and the cell viability was nearly 100%. After loaded with DOX, DOX@plSP@aptamer showed great potential in targeted therapy of tumors, and only 4.2% MCF-7 cells were viable.

Recent trends in sorbents for bioaffinity chromatography

Isolation or enrichment of biological molecules from complex biological samples is mostly a prerequisite in proteomics, genomics, and glycomics. Different techniques have been used to advance the efficiency of the purification of biological molecules. Bioaffinity chromatography is one of the most powerful technique that plays an important role in the isolation of target biological molecules by the specific interactions with ligands that are immobilized on different support materials. This review examines the recent developments in bioaffinity chromatography particularly over the past 5 years in the literature. Also properties of supports, immobilization techniques, types of binding agents, and methods used in bioaffinity chromatography applications are summarized.

Renewable photoelectrochemical cytosensing platform for rapid capture and detection of circulating tumor cells

Determination of circulating tumor cells (CTCs) is crucial for cancer diagnosis and therapy at an early stage. However, extremely low concentration of CTCs in peripheral blood makes the detection of CTCs challenging. In this study, a reusable cytosensor was developed for rapid detection of CTCs based on excellent photoelectrochemical (PEC) characteristic of semiconductor nanoarrays. Using typical breast cancer cell, MCF-7 cell, as a target model, a PEC sensing platform was constructed with polymerized aminophenylboronic acid (APBA) layer coated CdS/ZnO nanorod arrays, exhibiting outstanding performance for the capture and detection of CTCs. In this design, the polymerized APBA provides abundant binding sites for capturing terminal sialic acid (SA) molecules in CTCs. As a result, the PEC cytosensor shows good sensitivity and specificity with concentrations ranging from 50 to 1.0 × 10⁶ cells/mL MCF-7 cells. Moreover, the PEC cytosensor can be rapidly and effectively recovered via a short-time bias triggered cell release and subsequent repair of APBA. This study establishes a new approach to refine a PEC cytosensor for stable monitoring and provides a robust PEC electrode with high sensitivity and low cost for clinical diagnosis related to CTCs.