Bioinspired Hierarchically Structured Surfaces for Efficient Capture and Release of Circulating Tumor Cells

Capture and lyase-triggered release of circulating tumor cells using a disposable microfluidic chip embedded with core/shell nylon-6/Ca(II)-alginate immunofiber mats

High-efficiency capture, release, and reculture of circulating tumor cells (CTCs) can significantly advance individualized cancer treatments. To achieve efficient CTC release without compromising their viability for subsequent reculture, an effective CTC capture/release system was developed. Nylon-6 (N6) and a cross-linked alginate hydrogel with Ca(II) were used as the shell and core, respectively, to prepare N6/Ca-Alg immunofiber mats using coaxial electrospinning. A 3 wt% concentration of Ca(II) was used to increase the viscosity of the alginate solution and generate a degradable coating on the N6 fiber. After modification with streptavidin and anti-EpCAM, the N6/Ca-Alg immunofiber mat was embedded within a disposable microfluidic chip to investigate the capture capacity of CTCs. The maximum adsorption capacity of CTCs was approximately 34 cells per mm2, while the viability of the captured cells was 95.1% after being released from the fibrous mats. The outer Ca-alginate hydrogel coating effectively enhanced the viability of the released cells for reculture. In spiked blood samples, our microfluidic system was able to specifically identify DLD1 cells from 10 mL of human whole blood at a concentration of 65.6 cells per mL with 67.9% efficiency within 30 minutes. Under the flow of alginate lyase solution at 0.4 mg mL-1, the reculture efficiency of the released cells after 7 days reached 274.5%. Our proposed method provides an ideal fibrous mat to be embedded within a microfluidic chip for capturing and releasing CTCs for precision medicine applications, using recultured CTCs in individualized anti-tumor therapies.

Non-Invasive Prenatal Diagnosis of Chromosomal and Monogenic Disease by a Novel Bioinspired Micro-Nanochip for Isolating Fetal Nucleated Red Blood Cells

Purpose

Fetal nucleated red blood cells (fNRBCs) in the peripheral blood of pregnant women contain comprehensive fetal genetic information, making them an ideal target for non-invasive prenatal diagnosis (NIPD). However, challenges in identifying, enriching, and detecting fNRBCs limit their diagnostic potential.

Methods

To overcome these obstacles, we developed a novel biomimetic chip, replicating the micro-nano structure of red rose petals on polydimethylsiloxane (PDMS). The surface was modified with gelatin nanoparticles (GNPs) and affinity antibodies to enhance cell adhesion and facilitate specific cell identification. We subsequently investigated the chip's characteristics, along with its in vitro capture and release system, and conducted further experiments using peripheral blood samples from pregnant women.

Results

In the cell line capture and release assay, the chip achieved a cell capture efficiency of 90.4%. Following metalloproteinase-9 (MMP-9) enzymatic degradation, the release efficiency was 84.08%, with cell viability at 85.97%. Notably, fNRBCs can be captured from the peripheral blood of pregnant women as early as 7 weeks of gestation. We used these fNRBCs to diagnose a case of single-gene disease and instances of chromosomal aneuploidies, yielding results consistent with those obtained from amniotic fluid punctures.

Conclusion

This novel chip not only enables efficient enrichment of fNRBCs for NIPD but also extends the diagnostic window for genetic and developmental disorders to as early as 7 weeks of gestation, potentially allowing for earlier interventions. By improving the accuracy and reliability of NIPD, this technology could reduce reliance on invasive diagnostic techniques, offering a new pathway for diagnosing fetal genetic conditions in clinical practice.

Tumor Microenvironment-Inspired Glutathione-Responsive Three-Dimensional Fibrous Network for Efficient Trapping and Gentle Release of Circulating Tumor Cells

Detection of circulating tumor cells (CTCs) is important for early cancer diagnosis, prediction of postoperative recurrence, and individualized treatment. However, it is still challenging to achieve efficient capture and gentle release of CTCs from the complex peripheral blood due to their rarity and fragility. Herein, inspired by the three-dimensional (3D) network structure and high glutathione (GSH) level of the tumor microenvironment (TME), a 3D stereo (3D-G@FTP) fibrous network is developed by combining the liquid-assisted electrospinning method, gas foaming technique, and metal-polyphenol coordination interactions to achieve efficient trapping and gentle release of CTCs. Compared with the traditional 2D@FTP fibrous scaffold, the 3D-G@FTP fibrous network could achieve higher capture efficiency (90.4% vs 78.5%) toward cancer cells in a shorter time (30 min vs 90 min). This platform showed superior capture performance toward heterogeneous cancer cells (HepG2, HCT116, HeLa, and A549) in an epithelial cell adhesion molecule (EpCAM)-independent manner. In addition, the captured cells with high cell viability (>90.0%) could be gently released under biologically friendly GSH stimulus. More importantly, the 3D-G@FTP fibrous network could sensitively detect 4-19 CTCs from six kinds of cancer patients' blood samples. We expect this TME-inspired 3D stereo fibrous network integrating efficient trapping, broad-spectrum recognition, and gentle release will promote the development of biomimetic devices for rare cell analysis.

Bioinspired Materials for Wearable Devices and Point-of-Care Testing of Cancer

Wearable, point-of-care diagnostics, and biosensors are on the verge of bringing transformative changes in detection, management, and treatment of cancer. Bioinspired materials with new forms and functions have frequently been used, in both translational and commercial spaces, to fabricate such diagnostic platforms. Engineered from organic or inorganic molecules, bioinspired systems are naturally equipped with biorecognition and stimuli-sensitive properties. Mechanisms of action of bioinspired materials are deeply connected with thermodynamically or kinetically controlled self-assembly at the molecular and supramolecular levels. Thus, integration of bioinspired materials into wearable devices, either as triggers or sensors, brings about unique device properties usable for detection, capture, or rapid readout for an analyte of interest. In this review, we present the basic principles and mechanisms of action of diagnostic devices engineered from bioinspired materials, describe current advances, and discuss future trends of the field, particularly in the context of cancer.

Metal-mediated Fe3O4@polydopamine-aptamer capture nanoprobe coupling multifunctional MXene@Au@Pt nanozyme for direct and portable photothermal analysis of circulating breast cancer cells

Breast cancer (BC) is the most common cancer in the world and circulating tumor cells (CTCs) are reliable biomarkers for early breast cancer diagnosis in a non-invasive manner. However, effective isolation and sensitive detection of BC-CTCs by portable devices in human blood samples are extremely challenging. Herein, we proposed a highly sensitive and portable photothermal cytosensor for direct capture and quantification of BC-CTCs. To achieve efficient isolation of BC-CTCs, aptamer functionalized Fe₃O₄@PDA nanoprobe was facilely prepared through Ca²⁺-mediated DNA adsorption. To further detect the captured BC-CTCs with high sensitivity, multifunctional two-dimensional Ti₃C₂@Au@Pt nanozyme was synthesized, which not only possessed superior photothermal effect but also exhibited high peroxidase-like activity for catalyzing 3,3',5,5'-tetramethylbenzidine (TMB) to produce TMB oxide (oxTMB) with a strong photothermal characteristic, combining with Ti₃C₂@Au@Pt to synergistically amplify the temperature signal. Moreover, numerous Ti₃C₂@Au@Pt nanocomposites would be selectively attained on the BC-CTCs surface through multi-aptamer recognition and binding strategy, which further enhanced the specificity and facilitated signal amplification. Therefore, direct separation and highly sensitive detection of BC-CTCs was successfully achieved in human blood samples. More significantly, the controlled release of the captured BC-CTCs without affecting cell viability could be straightforwardly realized by a simple strand displacement reaction. Thus, with the distinct features of portability, high sensitivity, and easy operation, the current method holds great promise for early diagnosis of breast cancer.

Recent progress of nanostructure-based enrichment of circulating tumor cells and downstream analysis

The isolation and detection of circulating tumor cells (CTCs) play an important role in early cancer diagnosis and prognosis, providing easy access to identify metastatic cells before clinically detectable metastases. In the past 20 years, according to the heterogeneous expression of CTCs on the surface and their special physical properties (size, morphology, electricity, etc.), a series of in vitro enrichment methods of CTCs have been developed based on microfluidic chip technology, nanomaterials and various nanostructures. In recent years, the in vivo detection of CTCs has attracted considerable attention. Photoacoustic flow cytometry and fluorescence flow cytometry were used to detect CTCs in a noninvasive manner. In addition, flexible magnetic wire and indwelling intravascular non-circulating CTCs isolation system were developed for in vivo CTCs study. In the aspect of downstream analysis, gene analysis and drug sensitivity tests of enriched CTCs were developed based on various existing molecular analysis techniques. All of these studies constitute a complete study of CTCs. Although the existing reviews mainly focus on one aspect of capturing CTCs study, a review that includes the in vivo and in vitro capture and downstream analysis study of CTCs is highly needed. This review focuses on not only the classic work and latest research progress in in vitro capture but also includes the in vivo capture and downstream analysis, discussing the advantages and significance of the different research methods and providing new ideas for solving the heterogeneity and rarity of CTCs.

Noninvasive prenatal diagnosis targeting fetal nucleated red blood cells

Noninvasive prenatal diagnosis (NIPD) aims to detect fetal-related genetic disorders before birth by detecting markers in the peripheral blood of pregnant women, holding the potential in reducing the risk of fetal birth defects. Fetal-nucleated red blood cells (fNRBCs) can be used as biomarkers for NIPD, given their remarkable nature of carrying the entire genetic information of the fetus. Here, we review recent advances in NIPD technologies based on the isolation and analysis of fNRBCs. Conventional cell separation methods rely primarily on physical properties and surface antigens of fNRBCs, such as density gradient centrifugation, fluorescence-activated cell sorting, and magnetic-activated cell sorting. Due to the limitations of sensitivity and purity in Conventional methods, separation techniques based on micro-/nanomaterials have been developed as novel methods for isolating and enriching fNRBCs. We also discuss emerging methods based on microfluidic chips and nanostructured substrates for static and dynamic isolation of fNRBCs. Additionally, we introduce the identification techniques of fNRBCs and address the potential clinical diagnostic values of fNRBCs. Finally, we highlight the challenges and the future directions of fNRBCs as treatment guidelines in NIPD.

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.

Active cell capturing for organ-on-a-chip systems: a review

Organ-on-a-chip (OOC) is an emerging technology that has been proposed as a new powerful cell-based tool to imitate the pathophysiological environment of human organs. For most OOC systems, a pivotal step is to culture cells in microfluidic devices. In active cell capturing techniques, external actuators, such as electrokinetic, magnetic, acoustic, and optical forces, or a combination of these forces, can be applied to trap cells after ejecting cell suspension into the microchannel inlet. This review paper distinguishes the characteristics of biomaterials and evaluates microfluidic technology. Besides, various types of OOC and their fabrication techniques are reported and various active cell capture microstructures are analyzed. Furthermore, their constraints, challenges, and future perspectives are provided.

Biomimicked large-area anisotropic grooves fromDracaena sanderianaleaf enhances cellular alignment and subsequent differentiation

Cellular alignment is important for the proper functioning of different tissues such as muscles or blood vessel walls. Hence, in tissue engineering, sufficient effort has been made to control cellular orientation and alignment. It has been shown that micro-and nanoscale anisotropic topological features on cell culture substrates can control cellular orientation. Such substrates are fabricated using various lithography techniques such as photolithography and soft lithography. Although such techniques are suitable for creating patterns in small areas to establish a proof-of-concept, patterning large areas with intricate features is an unsolved problem. In this work, we report that a replica of the groove-like anisotropic patterns of the abaxial side of aDracaena sanderiana(bamboo) leaf can be used for large-area patterning of cells. We imprinted the leaf on polydimethylsiloxane (PDMS) and characterised its surface topography using scanning electron microscopy. We further cultured bone marrow human mesenchymal cells (BM-hMSCs), skeletal muscle cells (C2C12), and neuroblastoma cells (SHSY5Y) on the patterned PDMS on which the cells orient along the direction of the grooved pattern. Further, we observed enhanced neuronal differentiation of SHSY5Y cells on biomimicked pattern compared to flat PDMS as measured by percentage of cells with neurites, neurite length and the expression of neuronal differentiation marker beta-III tubulin (TUJ1). This process is simple, frugal, and can be adopted by laboratories with resource constraints. This one-step technique to fabricate large-area anisotropic surface patterns from bamboo leaves can be used as a platform to study cellular alignment and its effect on various cellular functions, including differentiation.

Polycarboxybetaine-Based Hydrogels for the Capture and Release of Circulating Tumor Cells

Circulating tumor cells (CTCs) are indicators for the detection, diagnosis, and monitoring of cancers and offer biological information for the development of personalized medicine. Techniques for the specific capture and non-destructive release of CTCs from millions of blood cells remain highly desirable. Here, we present a CTC capture-and-release system using a disulfide-containing poly(carboxybetaine methacrylate) (pCB) hydrogel. The non-fouling characteristic of pCB prevents unwanted, nonspecific cell binding, while the carboxyl functionality of pCB is used for the conjugation of anti-epithelial cell adhesion molecule (anti-EpCAM) antibodies for the capture of CTCs. The results demonstrated that the anti-EpCAM-conjugated pCB hydrogel captured HCT116 cells from blood, and the capture ratio reached 45%. Furthermore, the captured HCT116 cells were released within 30 min from the dissolution of the pCB hydrogel by adding cysteine, which breaks the disulfide bonds of the crosslinkers. The cells released were viable and able to grow. Our system has potential in the development of a device for CTC diagnosis.

State-of-the-arts techniques and current evolving approaches in the separation and detection of circulating tumor cell

Circulating tumor cells (CTCs) are cancer cells that shed from the primary tumor and then enter the circulatory system, a small part of which may evolve into metastatic cancer under appropriate microenvironment conditions. The detection of CTCs is a truly noninvasive, dynamic monitor for disease changes, which has considerable clinical implications in the selection of targeted drugs. However, their inherent rarity and heterogeneity pose significant challenges to their isolation and detection. Even the "gold standard", CellSearch™, suffers from high expenses, low capture efficiency, and the consumption of time. With the advancement of CTCs analysis technologies in recent years, the yield and efficiency of CTCs enrichment have gradually been improved, as well as detection sensitivity. In this review, the isolation and detection strategies of CTCs have been completely described and the potential directions for future research and development have also been highlighted through analyzing the challenges faced by current strategies.

Specific capture and intact release of breast cancer cells using a twin-layer vein-shaped microchip with a self-assembled surface

Breast cancer is the most fatal disease among female cancers yet its detection still relies on needle biopsy. The unique physical and immune characteristics of breast cancer cells different from blood cells make them suitable to be employed as excellent biomarkers in liquid biopsy, through which breast cancer cells are collected from peripheral blood for further cancer diagnosis, medical treatment monitoring, and drug screening. Although the separation and enrichment of breast cancer cells from peripheral blood have been studied for years, there are still two problems to be solved in these methods: the low efficiency of on-chip immunologic capture in the flow state and the influence of the conjugated antibodies for the following analyses during cell release. In this paper, a vein-shaped microchip with self-assembled surface was developed for the specific and robust capture (91.2%) of breast cancer cells in the flow state. A protein-recovery process was proposed, in which trypsin served as a mild release reagent, releasing 92% of cells with high viability (96%), normal adherent proliferation, and complete proteins on the cell membrane, avoiding disturbance of the conjugated chemical molecules in the following clinical study. The excellent performance demonstrated in isolating free breast cancer cells from real peripheral blood sample, originating from the orthotopic 4T1 breast cancer metastatic models, suggest the microchip could be utilized as a multiple circulating tumor cell capture and release platform that could allow providing more reliable information in liquid biopsies.

Biomimicked hierarchical 2D and 3D structures from natural templates: applications in cell biology

Intricate structures of natural surfaces and materials have amazed people over the ages. The unique properties of various surfaces also created interest and curiosity in researchers. In the recent past, with the advent of superior microscopy techniques, we have started to understand how these complex structures provide superior properties. With that knowledge, scientists have developed various biomimicked and bio-inspired surfaces for different non-biological applications. In the last two decades, we have also started to learn how structures of the tissue microenvironment influence cell function and behaviour, both in physiological and pathological conditions. Hence, it became essential to decipher the role and importance of structural hierarchy in the cellular context. With advances in microfabricated techniques, such complex structures were made by superimposing features of different dimensions. However, the fabricated topographies are far from matching the complexities presentin vivo. Hence, the need of biomimicking the natural surfaces for cellular applications was felt. In this review, we discuss a few examples of hierarchical surfaces found in plants, insects, and vertebrates. Such structures have been widely biomimicked for various applications but rarely studied for cell-substrate interaction and cellular response. Here, we discuss the research work wherein 2D hierarchical substrates were prepared using biomimicking to understand cellular functions such as adhesion, orientation, differentiation, and formation of spheroids. Further, we also present the status of ongoing research in mimicking 3D tissue architecture using de-cellularized plant-based and tissue/organ-based scaffolds. We will also discuss 3D printing for fabricating 2D and 3D hierarchical structures. The review will end by highlighting the various advantages and research challenges in this approach. The biomimickedin-vivolike substrate can be used to better understand cellular physiology, and for tissue engineering.

Hyaluronic acid-functionalized redox responsive immunomagnetic nanocarrier for circulating tumor cell capture and release

Detection of circulating tumor cells (CTCs) in peripheral blood holds significant insights for cancer diagnosis, prognosis evaluation, and precision medicine. To efficiently capture and release CTCs with high viability, we reported the development of hyaluronic acid (HA)-functionalized redox responsive immunomagnetic nanocarrier (Fe₃O₄@SiO₂-SS-HA). First, Fe₃O₄nanoparticles were prepared and modified with tetraethyl orthosilicate (TEOS), 3-mercaptopropyltrimethoxysilane (MPTMS) and 2,2'-dithiodipyridine (DDPy) to form the magnetic substrate (Fe₃O₄@SiO₂-SSPy). Modified with targeted segment HA-functionalized L-cysteine ethyl ester hydrochloride (HA-Cys) via disulfide exchange reaction, the Fe₃O₄@SiO₂-SS-HA was formed. The nanocarrier with prominent magnetic property, targeting ligand, and redox-sensitive disulfide linkages was able to specially capture MCF-7 cells with an efficiency of 92% and effectively release captured cells with an efficiency of 81.4%. Furthermore, the Fe₃O₄@SiO₂-SS-HA could successfully be used for the capture of MCF-7 cells, and the captured cells could be diferntiated from the blood cells. Almost all of released tumor cells kept good viability and a robust proliferative capacity after being re-cultured. It is likely that the as-prepared nanocarrier will serve as a new weapon against CD44 receptor-overexpressed cancer cells.

Enhancing interactions between cells and hierarchical micro/nanostructured TiO2films for efficient capture of circulating tumor cells

Micro/nano hierarchical substrates with different micropillar spacings were designed and prepared for capture of tumor cells. The cell capture efficiency of hierarchical substrates with low-density micropillar arrays was similar to that of nanostructured substrate. Increasing the density of micopillars could significantly improve the capture efficiency. The maximum capture efficiency was achieved on the hierarchical substrate with micropillar spacings of 15μm, but further reducing the micropillar spacings did not increase the cell capture efficiency. It was also found that hierarchical substrates with appropriate spacing of micropillars appeared more favorable for cell attachment and spreading, and thus enhancing the cell-material interaction. These results suggested that optimizing the micropillar arrays, such as the spacing between adjacent micropillars, could give full play to the synergistic effect of hierarchical hybrid micro/nanostructures in the interaction with cells. This study may provide promising guidance to design and optimize micro/nano hierarchical structures of biointerfaces for biomedical application.

Well-Defined Nanostructured Biointerfaces: Strengthened Cellular Interaction for Circulating Tumor Cells Isolation

The topographic features at the cell-material biointerface are critical for cellular sensing of the extracellular environment (ECM) and have gradually been recognized as key factors that regulate cell adhesion behavior. Herein, a well-defined nanostructured biointerface is fabricated via a new generation of mussel-inspired polymer coating to mimic the native ECM structures. Upon the bioinert background presence and biospecific ligands conjugation, the affinity of cancer cells to the resulting biofunctional surfaces, which integrate topographic features and biochemical cues, is greatly strengthened. Both the conjugated bioligand density, filopodia formation, and focal adhesion expression are significantly enhanced by the surficial nano-features with an optimized size-scale. Thus, this nanostructured biointerface exhibits high capture efficiency for circulating tumor cells (CTCs) with high sensitivity, high biospecificity, and high purity. Benefiting from the unique bioligands conjugation chemistry herein, the captured cancer cells can be responsively detached from the biointerfaces without damage for downstream analysis. The present biofunctional nanostructured interfaces offer a good solution to address current challenges to efficiently isolate rare CTCs from blood samples for earlier cancer diagnosis.

Improved Mesenchymal Stem Cell Proliferation, Differentiation, Epithelial Transition, and Restrained Senescence on Hierarchically Patterned Porous Honey Silk Fibroin Scaffolds

We report a significant improvement of adipose-derived mesenchymal stem cells' (ADMSCs) biocompatibility and proliferation on hierarchically patterned porous honey-incorporated silk fibroin scaffolds fabricated using a combination of soft lithography and freeze-drying techniques. Parametric variations show enhanced surface roughness, swelling, and degradation rate with good pore interconnectivity, porosity, and mechanical strength for soft-lithographically fabricated biomimetic microdome arrays on the 2% honey silk fibroin scaffold (PHSF2) as compared to its other variants, which eventually made PHSF2 more comparable to the native environment required for stem cell adhesion and proliferation. PHSF2 also exhibits sustained honey release with remarkable antibacterial efficacy against methicillin-resistant Staphylococcus aureus (MRSA). Honey incorporation (biochemical cue) influences microdome structural features, that is, biophysical cues (height, width, and periodicity), which further allows ADMSCs pseudopods (filopodia) to grasp the microdomes for efficient cell-cell communication and cell-matrix interaction and regulates ADMSCs behavior by altering their cytoskeletal rearrangement and thereby increases the cellular spreading area and cell sheet formation. The synergistic effect of biochemical (honey) and biophysical (patterns) cues on ADMSCs studied by the nitro blue tetrazolium assay and DCFDA fluorescence spectroscopy reveals limited free radical generation within cells. Molecular expression studies show a decrease in p53 and p21 expressions validating ADMSCs senescence inhibition, which is further correlated with a decrease in cellular senescence-associated β galactosidase activity. We also show that an increase in CDH1 and CK19 molecular expressions along with an increase in SOX9, RUNX2, and PPARγ molecular expressions supported by PHSF2 justify the substrate's efficacy of underpinning mesenchymal to epithelial transition and multilineage trans-differentiation. This work highlights the fabrication of a naturally healing nutraceutical (honey)-embedded patterned porous stand-alone tool with the potential to be used as smart stem cells delivering regenerative healing implant.

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.

Facile cell patterning induced by combined surface topography and chemistry on polydopamine-defined nanosubstrates

Cell patterning holds significant implications for cell-based analysis and high-throughput screening. The challenge and key factor for formation of cell patterns is to precisely modulate the interaction between cells and substrate surfaces. Many nanosubstrates have been developed to control cell adhesion and patterning, however, requirements of complicated fabrication procedures, harsh reaction conditions, and delicate manipulation are not routinely feasible. Here, we developed a hierarchical polydimethylsiloxane nanosubstrate (HPNS) coated with mussel-inspired polydopamine (PDA) micropatterns for effective cell patterning, depending on both surface topography and chemistry. HPNSs obtained by facile template-assisted replication brought enhanced topographic interaction between cells and substrates, but they were innately hydrophobic and cell-repellent. The hydrophobic nanosubstrates were converted to be hydrophilic after PDA coatings formed via spontaneous self-polymerization, which greatly facilitated cell adhesion. As such, without resorting to any external forces or physical constraints, cells selectively adhered and spread on spatially defined PDA regions with high efficiency, and well-defined cell microarrays could be formed within 20 min. Therefore, this easy-to-fabricate nanosubstrate with no complex chemical modification will afford a facile yet effective platform for rapid cell patterning.

Circulating Tumor Marker Isolation with the Chemically Stable and Instantly Degradable (CSID) Hydrogel ImmunoSpheres

Here, we present chemically stable and instantly degradable (CSID) hydrogel immunospheres for the isolation of circulating tumor cells (CTCs) and circulating tumor exosomes (CTXs). The CSID hydrogels, which are prepared by the hybridization of alginate and poly(vinyl alcohol), show an equilibrium swelling ratio (ESR) of at pH 7, with a highly stable pH-responsive property. The present hybrid hydrogel is not easily disassociated in the biological buffers, thus being suitable for use in "liquid biopsy", requiring a multistep, long-term incubation process with biological samples. Also, it is gradually degraded by the action of chelating agents; effortless retrieval of the circulating markers has been achieved. Then, we modified the CSID hydrogel spheres with the anti-EpCAM antibody ("C-CSID ImmunoSpheres") and the anti-CD63 antibody ("E-CSID ImmunoSpheres") to isolate two promising circulating markers in liquid biopsy: CTCs and CTXs. The immunospheres' capabilities for marker isolation and retrieval were confirmed by a fluorescence image, where the spheres successfully isolate and effortlessly retrieve the target circulating markers. Lastly, we applied the CSID hydrogel immunospheres to five blood samples from colorectal cancer patients and retrieved average 10.8 ± 5.9 CTCs/mL and average 96.5 × 10⁶ CTXs/mL. The present CSID hydrogel immunospheres represent a simple, versatile, and time-efficient assay platform for liquid biopsy in the practical setting, enabling us to gain a better understanding of disease-related circulating markers.

Natural Fish Trap-Like Nanocage for Label-Free Capture of Circulating Tumor Cells

Nanomaterials have achieved several breakthroughs in the capture of circulating tumor cells (CTCs) over the past decades. However, artificial fabrication of label-free nanomaterials used for high-efficiency CTC capture is still a challenge. Through billions of years of evolution and natural selection, various complicated and precise hierarchical structures are developed. Here, a novel fish trap-like "nanocage" structure derived from the natural Chrysanthemum pollen is reported and a nanocage-featured film for the label-free capture of CTCs and CTC clusters is constructed. The nanocage-featured film effectively captures 92% rare cancer cells with a broad spectrum of cancer types, due to the synergistic effect of nanocage-CTC filopodia matching, high contact area, and strong adhesion force between the cancer cells and the nanocage. Furthermore, the nanocage-featured film successfully detects CTCs and CTC clusters in 2 or 4 mL blood taken from 21 cancer patients (stages I-IV) suffering from various types of cancers. This novel, abundant, and economical fish trap-like "nanocage" may provide new perspectives for the application of natural nanomaterials in clinical CTC capture and analysis.

Nanostructured Substrates for Detection and Characterization of Circulating Rare Cells: From Materials Research to Clinical Applications

Circulating rare cells in the blood are of great significance for both materials research and clinical applications. For example, circulating tumor cells (CTCs) have been demonstrated as useful biomarkers for "liquid biopsy" of the tumor. Circulating fetal nucleated cells (CFNCs) have shown potential in noninvasive prenatal diagnostics. However, it is technically challenging to detect and isolate circulating rare cells due to their extremely low abundance compared to hematologic cells. Nanostructured substrates offer a unique solution to address these challenges by providing local topographic interactions to strengthen cell adhesion and large surface areas for grafting capture agents, resulting in improved cell capture efficiency, purity, sensitivity, and reproducibility. In addition, rare-cell retrieval strategies, including stimulus-responsiveness and additive reagent-triggered release on different nanostructured substrates, allow for on-demand retrieval of the captured CTCs/CFNCs with high cell viability and molecular integrity. Several nanostructured substrate-enabled CTC/CFNC assays are observed maturing from enumeration and subclassification to molecular analyses. These can one day become powerful tools in disease diagnosis, prognostic prediction, and dynamic monitoring of therapeutic response-paving the way for personalized medical care.

Hierarchical Rose Petal Surfaces Delay the Early-Stage Bacterial Biofilm Growth

A variety of natural surfaces exhibit antibacterial properties; as a result, significant efforts in the past decade have been dedicated toward fabrication of biomimetic surfaces that can help control biofilm growth. Examples of such surfaces include rose petals, which possess hierarchical structures like the micropapillae measuring tens of microns and nanofolds that range in the size of 700 ± 100 nm. We duplicated the natural structures on rose petal surfaces via a simple UV-curable nanocasting technique and tested the efficacy of these artificial surfaces in preventing biofilm growth using clinically relevant bacteria strains. The rose petal-structured surfaces exhibited hydrophobicity (contact angle (CA) ≈ 130.8° ± 4.3°) and high CA hysteresis (∼91.0° ± 4.9°). Water droplets on rose petal replicas evaporated following the constant contact line mode, indicating the likely coexistence of both Cassie and Wenzel states (Cassie-Baxter impregnating the wetting state). Fluorescence microscopy and image analysis revealed the significantly lower attachment of Staphylococcus epidermidis (86.1 ± 6.2% less) and Pseudomonas aeruginosa (85.9 ± 3.2% less) on the rose petal-structured surfaces, compared with flat surfaces over a period of 2 h. An extensive biofilm matrix was observed in biofilms formed by both species on flat surfaces after prolonged growth (several days), but was less apparent on rose petal-biomimetic surfaces. In addition, the biomass of S. epidermidis (63.2 ± 9.4% less) and P. aeruginosa (76.0 ± 10.0% less) biofilms were significantly reduced on the rose petal-structured surfaces, in comparison to the flat surfaces. By comparing P. aeruginosa growth on representative unitary nanopillars, we demonstrated that hierarchical structures are more effective in delaying biofilm growth. The mechanisms are two-fold: (1) the nanofolds across the hemispherical micropapillae restrict initial attachment of bacterial cells and delay the direct contact of cells via cell alignment and (2) the hemispherical micropapillae arrays isolate bacterial clusters and inhibit the formation of a fibrous network. The hierarchical features on rose petal surfaces may be useful for developing strategies to control biofilm formation in medical and industrial contexts.

Effect of Chirality on Cell Spreading and Differentiation: From Chiral Molecules to Chiral Self-Assembly

The influence of chirality on cell behavior is closely related with relevant biological events; however, many recent studies only focus on the apparent chiral influence of supramolecular nanofibers and ignore the respective effects of molecular chirality and supramolecular chirality in biological processes. Herein, the inherent molecular and supramolecular chiral effects on cell spreading and differentiation are studied. Left-handed nanofibers (referring to supramolecular chirality) assembled from l-amino acid derivatives can enhance cell spreading and proliferation compared to flat l-surfaces (referring to molecular chirality). However, compared to the d-surfaces (referring to molecular chirality), right-handed nanofibers (referring to supramolecular chirality) derived from d-amino acid suppress cell spreading and proliferation, overturning the conventional view that a fibrous morphology generally enhances cell adhesion. The results directly suggest that the amplification of chirality from chiral molecules to chiral assemblies significantly enhances the effect on regulated cell behavior by supramolecular helical handedness. Moreover, cell differentiation is found to be chirality dependent. It suggests that both the l-amino acid derivatives and the left-handed fibers facilitate osteogenic differentiation. This study provides useful insight into understanding the origin of chiral expression from the molecular to the macroscopic level in nature.

Bioinert and Lubricious Surfaces by Macromolecular Design

The modification of a variety of biomaterials and medical devices often encompasses the generation of biopassive and lubricious layers on their exposed surfaces. This is valid when the synthetic supports are required to integrate within physiological media without altering their interfacial composition and when the minimization of shear stress prevents or reduces damage to the surrounding environment. In many of these cases, hydrophilic polymer brushes assembled from surface-interacting polymer adsorbates or directly grown by surface-initiated polymerizations (SIP) are chosen. Although growing efforts by polymer chemists have been focusing on varying the composition of polymer brushes in order to attain increasingly bioinert and lubricious surfaces, the precise modulation of polymer architecture has simultaneously enabled us to substantially broaden the tuning potential for the above-mentioned properties. This feature article concentrates on reviewing this latter strategy, comparatively analyzing how polymer brush parameters such as molecular weight and grafting density, the application of block copolymers, the introduction of branching and cross-links, or the variation of polymer topology beyond the simple, linear chains determine highly technologically relevant properties, such as biopassivity and lubrication.

Translating Surface-Initiated Atom Transfer Radical Polymerization into Technology: The Mechanism of Cu0-Mediated SI-ATRP under Environmental Conditions

The exceptional features of Cu⁰-mediated surface-initiated atom transfer radical polymerization (Cu⁰ SI-ATRP), and its potential for implementation in technologically relevant surface functionalizations are demonstrated thanks to a comprehensive understanding of its mechanism. Cu⁰ SI-ATRP enables the synthesis of multifunctional polymer brushes with a remarkable degree of control, over extremely large areas and without the need for inert atmosphere or deoxygenation of monomer solutions. When a polymerization mixture is placed between a flat copper plate and an ATRP-initiator-functionalized substrate, the vertical distance between these two overlaying surfaces determines the tolerance of the grafting process toward the oxygen, while the composition of the polymerization solution emerges as the critical parameter regulating polymer-grafting kinetics. At very small distances between the copper plate and the initiating surfaces, the oxygen dissolved in the solution is rapidly consumed via oxidation of the metallic substrate. In the presence of ligand, copper species diffuse to the surface-immobilized initiators and trigger a rapid growth of polymer brushes. Concurrently, the presence and concentration of added Cu^II regulates the generation of Cu^I-based activators through comproportionation with Cu⁰. Hence, under oxygen-tolerant conditions, the extent of comproportionation, together with the solvent-dependent rate constant of activation (k_act) of ATRP are the main determinants of the growth rate of polymer brushes.

Modular Chamber Assembled with Cell-Replicated Surface for Capture of Cancer Cells

The capture of circulating tumor cells (CTCs) is mainly carried out with a small volume of blood using magnetic nanoparticles and complex microfluidics. In this study, we propose a CTC-capture apparatus based on a modular design and called this apparatus as the CTC chamber. Distinct from other CTC-capture apparatuses, the capacity of the CTC chamber could be altered by varying the number of CTC-capture modules to accommodate the different volumes of blood sample. The core component of the CTC-capture module was a polydimethylsiloxane (PDMS) film with cell-replicated topological structure and anti-EpCAM antibody coating. Both synergistic roles can enhance the capture yield of cancer cells. Furthermore, the CTC chamber was assembled with one or three CTC-capture modules for the capture of cancer cells from spiked blood samples representing late-stage (3 mL of blood, 10 cancer cells mL^-1) or middle-early stage (9 mL of blood, 1 cancer cell mL^-1) cancer. The results showed that high capture yield (EpCAM-positive, ∼80%; EpCAM-negative, ∼65%) and purity (EpCAM-positive, ∼90%; EpCAM-negative, ∼80%) could be obtained within 1 h. This economic and facile CTC chamber could therefore open up opportunities for designing the next-generation CTC detection devices suitable for the diagnosis of different stages of cancer.

Hierarchical nanomaterials via biomolecular self-assembly and bioinspiration for energy and environmental applications

Bioinspired synthesis offers potential green strategies to build highly complex nanomaterials by utilizing the unique nanostructures, functions, and properties of biomolecules, in which the biomolecular recognition and self-assembly processes play important roles in tailoring the structures and functions of bioinspired materials. Further understanding of biomolecular self-assembly for inspiring the formation and assembly of nanoparticles would promote the design and fabrication of functional nanomaterials for various applications. In this review, we focus on recent advances in bioinspired synthesis and applications of hierarchical nanomaterials based on biomolecular self-assembly. We first discuss biomolecular self-assembly towards biological nanomaterials, in which the mechanisms and ways of biomolecular self-assembly as well as various self-assembled biomolecular nanostructures are demonstrated. Secondly, the bioinspired synthesis strategies including molecule-molecule interaction, molecule-material recognition, molecule-mediated nucleation and growth, and molecule-mediated reduction/oxidation are introduced and discussed. Meanwhile, typical examples and discussions on how biomolecular self-assembly inspires the formation of hierarchical hybrid nanomaterials are presented. Finally, the applications of bioinspired nanomaterials in biofuel cells, light-harvesting systems, batteries, supercapacitors, catalysis, water/air purification, and environmental monitoring are presented and discussed. We believe that this review will be very helpful for readers to understand the self-assembly of biomolecules and the biomimetic/bioinspired strategies for synthesizing hierarchical nanomaterials on the one hand, and on the other hand to design novel materials for extended applications in nanotechnology, materials science, analytical science, and biomedical engineering.

Real-Time Profiling of Anti-(Epithelial Cell Adhesion Molecule)-Based Immune Capture from Molecules to Cells Using Multiparameter Surface Plasmon Resonance

Antibodies of epithelial cell-adhesion molecule (anti-EpCAM)-based interfaces have proven to be highly efficient at capturing circulating tumor cells (CTCs). To achieve the bonding of anti-EpCAM to the interface, biotin and streptavidin are used to modify the surface. These processes are critical to subsequent cell-capture efficiencies. However, quantitative research on the interactions between biotin, streptavidin, and biotinylated anti-EpCAM on the interface is lacking. In this work, the thermodynamics and kinetics of biomolecular interactions were determined by using surface plasmon resonance. The equilibrium binding affinities for biotinylated anti-EpCAM to streptavidin and streptavidin to biotin (illustrated by biotin-PEG400-thiol) were found to be 2.75 × 10⁶ and 8.82 × 10⁶ M^-1, respectively. Each streptavidin can bind up to 2.30 biotinylated anti-EpCAM under thermodynamic equilibrium. The findings provide useful information to optimize the modification of anti-EpCAM and improve the capture efficiency of CTCs.

Cell-imprinted biomimetic interface for intelligent recognition and efficient capture of CTCs

Synergistically contributing to plastic and natural antibodies, a cell-imprinted biomimetic interface exhibited high sensitivity and efficiency in CTC capture, providing novel insight into cell–biointerface interactions.

Flow plate separation of cells based on elastic properties: a computational study

Medical studies have consistently shown that the best defense against cancer is early detection. Due to this, many efforts have been made to develop methods of screening patient blood quickly and cheaply. These methods range from separation via differences in size, electrostatic potential, chemical potential, antibody-binding affinity, among others. We propose a method of separating cells which have similar size and outer coatings, but which differ in their elastic properties. Such a method would be useful in detecting cancerous cells, which may have similar properties to leukocytes or erythrocytes but differ in their stiffness and deformation response. Here, we use coarse-grained model of a cell with membrane, cytoskeleton, and inner fluid to determine how small changes in the cell stiffness may be used to quickly and efficiently separate out irregular cells such as circulating tumor cells from a sample of blood. We focus specifically on the effects of volumetric flux and plate geometry on the ability of a separation plate to differentiate cells of similar but disparate stiffnesses. We show that volumetric flux is crucial in determining the stiffness cutoff for separating out cells of similar sizes, while the angle of the separation plate plays a less important role. With this work, we provide a comprehensive approach to the design factors of cell separation via elastic properties and hope to offer a guideline for the development of novel cytometry devices for the detection of irregular cells such as circulating tumor cells.

Enhanced cell adhesion on a bio-inspired hierarchically structured polyester modified with gelatin-methacrylate

Herein, fabrication and modification of novel bio-inspired microwell arrays with nanoscale topographic structures are reported. The natural nano- and microstructures present on the surface of rose petals were hypothesized to enhance cell-surface contacts. Thus hierarchically structured polyethylene terephthalate glycol modified (PETG) substrates were fabricated by replication from rose petals via nanoimprint lithography, followed by covalent modification and crosslinking with RGD-presenting gelatin-methacrylate (GelMA) for promoting cell adhesion and spreading. Cell culture experiments showed that the introduction of gelatin resulted in significantly enhanced cell adhesion and more than doubled cell areas on the GelMA modified surfaces. In addition, a slight preference was observed for concave compared to convex surfaces, which is tentatively attributed to the matching curvature of the micro-cavities and the cells, facilitating the accommodation of cells. These bioinspired hierarchically structured and gelatin functionalized substrates may provide new prospects for designing cell-based interfaces for advanced biomedical studies, e.g. for cell culture and biosensing in the future.

Sustainable and long-time 'rejuvenation' of biomimetic water-repellent silica coating on polyester fabrics induced by rough mechanical abrasion

The economical use of water-repellent coatings on polymeric materials in commercial and industrial applications is limited by their mechanical wear robustness and long-term durability. In this study, we demonstrate that polyethylene terephthalate (PET) fabric modified with inorganic, methyltrimethoxysilane (MTMS)-based coatings shows excellent resistance against various types of wear damage, thereby mimicking superhydrophobic biological materials. These features were facilitated by the rational design of coating processing that also enabled tunable hierarchical surface structure. A series of custom and standard testing protocols revealed that coating-to-substrate adhesion was remarkably high, as was the resistance to various mechanical abradents. The most intriguing characteristic observed during aging and abrasion cycles was the enhancement in non-wettability or 'rejuvenation' reflected by water droplet roll-off behavior, a characteristic of self-cleaning materials. Water-repellent properties of coated polyester were also enhanced by prolonged thermal annealing and were maintained after custom laundry. The developed technology offers opportunities to design low cost, durable and functional textiles for both indoor and outdoor applications.

TiO2 Nanorod Arrays with Mesoscopic Micro-Nano Interfaces for in Situ Regulation of Cell Morphology and Nucleus Deformation

Cell morphology and nucleus deformation are important when circulating tumor cells break away from the primary tumor and migrate to a distant organ. Cells are sensitive to the microenvironment and respond to the cell-material interfaces. We fabricated TiO₂ nanorod arrays with mesoscopic micro-nano interfaces through a two-step hydrothermal reaction method to induce severe changes in cell morphology and nucleus deformation. The average size of the microscale voids was increased from 5.1 to 10.5 μm when the hydrothermal etching time was increased from 3 to 10 h, whereas the average distances between voids were decreased from 0.88 to 0.40 μm. The nucleus of the MCF-7 cells on the TiO₂ nanorod substrate that was etched for 10 h exhibited a significant deformation, because of the large size of the voids and the small distance between voids. Nucleus defromation was reversible during the cells proliferate process when the cells were cultured on the mesoscopic micro-nano interface.This reversible process was regulated by combining of the uniform pressure applied by the actin cap and the localized pressure applied by the actin underneath the nucleus. Cell morphology and nucleus shape interacted with each other to adapt to the microenvironment. This mesoscopic micro-nano interface provided a new insight into the cell-biomaterial interface to investigate cell behaviors.

Design of functional electrospun nanofibers for cancer cell capture applications

The review reports recent advances in the design of functional electrospun nanofibers for cancer cell capture applications.

Highly Efficient Capture and Electrochemical Release of Circulating Tumor Cells by Using Aptamers Modified Gold Nanowire Arrays

The effective capture and release of circulating tumor cells (CTCs) is of significant importance in cancer prognose and treatment. Here we report a highly efficient method to capture and release human leukemic lymphoblasts (CCRF-CEM) using aptamers modified gold nanowire arrays (AuNWs). The gold nanowires, showing tunable morphologies from relatively random pillar deposit to relatively uniform arrays, were fabricated by electrochemical deposition using anodic aluminum oxide (AAO) as template. Upon simply being modified with aptamers by Au-S chemistry, the AuNWs exhibit higher specificity to target cells. Also compared to flat gold substrate, the AuNWs with nanostructure can capture target cells with much higher capture yield. Moreover, the captured CCRF-CEM cells can be released from AuNWs efficiently with little damage through an electrochemical desorption process. We predict that our strategy has great potential in providing a simple and economical platform for CTCs isolation, cancer diagnosis, and therapy.