Aptamer-mediated efficient capture and release of T lymphocytes on nanostructured surfaces

Shape Memory Polymer Microtransfer Printing Stamp with Macro-Micro Adjustable Adhesion Superhydrophobic Surface Obtained by Laser Texturing

The application of microtransfer technology to the manipulation process of microdevices is an area of current research. In the context of temperature-controlled microtransfer technology, the shape memory polymer (SMP) stamp plays a crucial role in microdevice manipulation, particularly surface adhesion. Aiming at the current problems such as the complexity and high cost of the SMP surface microstructure preparation process and the difficulty of surface adhesion adjustment leading to the inflexibility of microdevices pick and release, this study investigated the nanosecond ultraviolet (UV) laser ablation of superhydrophobic structures on the surface of SMP stamps and the adjustment of the surface macro-micro adhesion. The surface of the SMP stamp was ablated by laser direct writing to form a microgrid structure, which was then chemically modified to realize the superhydrophobic property of the originally hydrophilic stamp. It was found that when the surface microstructure of the SMP stamp was subjected to vertical thermal pressure, the surface microstructure of the stamp was deformed. The hydrophobicity of the whole stamp surface was weakened, and the surface adhesion was changed. Due to the shape memory property of the SMP stamp, the original microstructure state can be restored by simple heating, and the surface is still superhydrophobic after many cycles of vertical thermal pressure recovery. In this study, the superhydrophobic preparation process of the stamp surface is greatly simplified. The fine-tuning of the adhesion and wettability of the stamp surface is accomplished by changing the temperature. The macro-tuning of the stamp surface is accomplished by the regionalized design. Finally, in-plane programmable microtransfer printing was realized according to the established graphic layout of the microdevice. The macro-micro tunable adhesion superhydrophobic SMP microtransfer stamp surface has many applications in microdevice manipulation, microelectronic device assembly, and microelectromechanical system construction (MEMS).

Precise Capture and Dynamic Release of Circulating Liver Cancer Cells with Dual-Histidine-Based Cell Imprinted Hydrogels

Circulating tumor cells (CTCs) detection presents significant advantages in diagnosing liver cancer due to its noninvasiveness, real-time monitoring, and dynamic tracking. However, the clinical application of CTCs-based diagnosis is largely limited by the challenges of capturing low-abundance CTCs within a complex blood environment while ensuring them alive. Here, an ultrastrong ligand, l-histidine-l-histidine (HH), specifically targeting sialylated glycans on the surface of CTCs, is designed. Furthermore, HH is integrated into a cell-imprinted polymer, constructing a hydrogel with precise CTCs imprinting, high elasticity, satisfactory blood compatibility, and robust anti-interference capacities. These features endow the hydrogel with excellent capture efficiency (>95%) for CTCs in peripheral blood, as well as the ability to release CTCs controllably and alive. Clinical tests substantiate the accurate differentiation between liver cancer, cirrhosis, and healthy groups using this method. The remarkable diagnostic accuracy (94%), lossless release of CTCs, material reversibility, and cost-effectiveness ($6.68 per sample) make the HH-based hydrogel a potentially revolutionary technology for liver cancer diagnosis and single-cell analysis.

Photo-Controlled Gating of Selective Bacterial Membrane Interaction and Enhanced Antibacterial Activity for Wound Healing

Reversible biointerfaces are essential for on-demand molecular recognition to regulate stimuli-responsive bioactivity such as specific interactions with cell membranes. The reversibility on a single platform allows the smart material to kill pathogens or attach/detach cells. Herein, we introduce a 2D-MoS2 functionalized with cationic azobenzene that interacts selectively with either Gram-positive or Gram-negative bacteria in a light-gated fashion. The trans conformation (trans-Azo-MoS2 ) selectively kills Gram-negative bacteria, whereas the cis form (cis-Azo-MoS2 ), under UV light, exhibits antibacterial activity against Gram-positive strains. The mechanistic investigation indicates that the cis-Azo-MoS2 exhibits higher affinity towards the membrane of Gram-positive bacteria compared to trans-Azo-MoS2 . In case of Gram-negative bacteria, trans-Azo-MoS2 internalizes more efficiently than cis-Azo-MoS2 and generates intracellular ROS to kill the bacteria. While the trans-Azo-MoS2 exhibits strong electrostatic interactions and internalizes faster into Gram-negative bacterial cells, cis-Azo-MoS2 primarily interacts with Gram-positive bacteria through hydrophobic and H-bonding interactions. The difference in molecular mechanism leads to photo-controlled Gram-selectivity and enhanced antibacterial activity. We found strain-specific and high bactericidal activity (minimal bactericidal concentration, 0.65 μg/ml) with low cytotoxicity, which we extended to wound healing applications. This methodology provides a single platform for efficiently switching between conformers to reversibly control the strain-selective bactericidal activity regulated by light.

Real-Time Evaluation of Adhesion Processes and Glucose Response of Cancer Cells onto Phenylboronic Acid-Functionalized Films Monitored by Quartz Crystal Microbalance with Dissipation

Understanding the interactions between cancer cells and smart substrates is of great benefit to physiology and pathology. Herein, we successfully fabricated two phenylboronic acid (PBA)-functionalized films with different surface topographies using a PBA homopolymer (PBAH) and self-assembled nanoparticles (PBAS) via a layer-by-layer assembly technique. We used a quartz crystal microbalance with dissipation (QCM-D) to monitor the entire cell adhesion process and figured out the adhesion kinetics of HepG2 cells on the two PBA-functionalized films. As seen from the QCM-D data, the HepG2 cells displayed distinctly different adhesion behaviors on the two PBA-functionalized films (PBAS and PBAH films). The results showed that the PBAS film promoted cell adhesion and cell spreading owing to its specific physicochemical properties. Likewise, the slope changes in the D-f plots clearly revealed the evolution of the cell adhesion process, which could be classified into three stages during cell adhesion on the PBA-functionalized films. In addition, compared with the PBAH film, the PBAS film could also control cell detachment behavior in the presence of glucose based on the molecular recognition between the PBA group and the cell membrane. Such a glucose-responsive PBAS film is promising for biological applications, including cell-based diagnostics and tissue engineering. In addition, the QCM-D proved to be a useful tool for in situ and real-time monitoring and analysis of interactions between cells and surfaces of supporting substrates.

Baits-trap chip for accurate and ultrasensitive capture of living circulating tumor cells

Accurate analysis of living circulating tumor cells (CTCs) plays a crucial role in cancer diagnosis and prognosis evaluation. However, it is still challenging to develop a facile method for accurate, sensitive, and broad-spectrum isolation of living CTCs. Herein, inspired by the filopodia-extending behavior and clustered surface-biomarker of living CTCs, we present a unique baits-trap chip to achieve accurate and ultrasensitive capture of living CTCs from peripheral blood. The baits-trap chip is designed with the integration of nanocage (NCage) structure and branched aptamers. The NCage structure could "trap" the extended filopodia of living CTCs and resist the adhesion of filopodia-inhibited apoptotic cells, thus realizing the accurate capture (∼95% accuracy) of living CTCs independent of complex instruments. Using an in-situ rolling circle amplification (RCA) method, branched aptamers were easily modified onto the NCage structure, and served as "baits" to enhance the multi-interactions between CTC biomarker and chips, leading to ultrasensitive (99%) and reversible cell capture performance. The baits-trap chip successfully detects living CTCs in broad-spectrum cancer patients and achieves high diagnostic sensitivity (100%) and specificity (86%) of early prostate cancer. Therefore, our baits-trap chip provides a facile, accurate, and ultrasensitive strategy for living CTC isolation in clinical. STATEMENT OF SIGNIFICANCE: A unique baits-trap chip integrated with precise nanocage structure and branched aptamers was developed for the accurate and ultrasensitive capture of living CTCs. Compared with the current CTC isolation methods that are unable to distinguish CTC viability, the nanocage structure could not only "trap" the extended-filopodia of living CTCs, but also resist the adhesion of filopodia-inhibited apoptotic cells, thus realizing the accurate capture of living CTCs. Additionally, benefiting from the "baits-trap" synergistic effects generated by aptamer modification and nanocage structure, our chip achieved ultrasensitive, reversible capture of living CTCs. Moreover, this work provided a facile strategy for living CTC isolation from the blood of patients with early-stage and advanced cancer, exhibiting high consistency with the pathological diagnosis.

Double-Tetrahedral DNA Probe Functionalized Ag Nanorod Biointerface for Effective Capture, Highly Sensitive Detection, and Nondestructive Release of Circulating Tumor Cells

Circulating tumor cells (CTCs) are indicative of tumorigenesis, metastasis, and recurrence; however, it is still a great challenge to efficiently analyze the extremely rare CTCs in peripheral blood. Herein, a novel nanobiointerface integrating high affinities of arrayed silver nanorods (Ag NRs) and double-tetrahedral DNA (DTDN) probes by a clever strategy is proposed for the efficient capture, highly sensitive detection, and nondestructive release of CTCs. Under the optimal conditions, the DTDN-probe-functionalized Ag NRs nanobiointerface can capture 90.2% of SGC-7901 cells in PBS, and the capture efficiency is 2.8 times and 50 times those of a DTDN-probe-functionalized Ag film and unfunctionalized Ag NRs, respectively, benefiting from the nanorough interface of the Ag NRs array and multivalent recognition of the DTDN probe. In addition, 93.4% of cells was released via Zn2+-assisted DNAzyme cleavage, and the viability of the postreleased CTCs is about 98.0%. The potential practicality of the nanobiointerface for testing CTCs in blood was further characterized by spiking SGC-7901 cells in leukocytes collected from human blood, and the results show that 83.8% capture efficiency, 91.2% release efficiency, and single-cell detection limit were achieved, which indicates that the nanobiointerface has great potential in clinical applications for reliable CTC analyses.

High-Efficiency Capture of Cells by Softening Cell Membrane

The capture of circulating tumor cells (CTCs) by nanostructured substrate surface is a useful method for early diagnosis of cancer. At present, most methods used to improve the cell capture efficiency are based on changing substrate surface properties. However, there are still some gaps between these methods and practical applications. Here, a method is presented for improving cell capture efficiency from a different perspective, that is, changing the properties of the cells. Concretely, the mechanical properties of the cell membrane are changed by adding Cytochalasin D to soften the cell membrane. Furthermore, a corresponding theoretical model is proposed to explain the experimental results. It is found that cell softening can reduce the resistance of cell adhesion, which makes the adhesion ability stronger. The high-efficiency capture of cells by softening the cell membrane provides a potential method to improve the detection performance of CTCs.

Miniaturized droplet microarray platform enables maintenance of human induced pluripotent stem cell pluripotency

The capacity of human induced pluripotent stem cells (hiPSCs) for indefinite self-renewal warrants their application in disease modeling, drug discovery, toxicity assays and efficacy screening. However, their poor proliferation ability, inability to adhere to surfaces without Matrigel coating and tendency to spontaneously differentiate in vitro hinder the application of hiPSCs in these fields. Here we study the ability to culture hiPSCs inside 200 ​nL droplets on the droplet microarray (DMA) platform. We demonstrate that (1) hiPSCs can attach to the Matrigel (MG)-free surface of DMA and show good viability after 24 h culture; (2) hiPSC do not spontaneously differentiate when cultured on the MG-free surface of DMAs; (3) culturing of hiPSCs in 200 ​nL as compared to 2 ​mL culture leads to higher expression of the Nanog pluripotency marker. Overall, the results demonstrate the possibility to culture undifferentiated hiPSCs in 200 ​nL droplets on DMA, thereby opening the possibility for high-throughput screenings of hiPSCs with various factors without compromising the results through the involvement of animal-derived materials, such as Matrigel.

Structuring of Si into Multiple Scales by Metal-Assisted Chemical Etching

Structuring Si, ranging from nanoscale to macroscale feature dimensions, is essential for many applications. Metal-assisted chemical etching (MaCE) has been developed as a simple, low-cost, and scalable method to produce structures across widely different dimensions. The process involves various parameters, such as catalyst, substrate doping type and level, crystallography, etchant formulation, and etch additives. Careful optimization of these parameters is the key to the successful fabrication of Si structures. In this review, recent additions to the MaCE process are presented after a brief introduction to the fundamental principles involved in MaCE. In particular, the bulk-scale structuring of Si by MaCE is summarized and critically discussed with application examples. Various approaches for effective mass transport schemes are introduced and discussed. Further, the fine control of etch directionality and uniformity, and the suppression of unwanted side etching are also discussed. Known application examples of Si macrostructures fabricated by MaCE, though limited thus far, are presented. There are significant opportunities for the application of macroscale Si structures in different fields, such as microfluidics, micro-total analysis systems, and microelectromechanical systems, etc. Thus more research is necessary on macroscale MaCE of Si and their applications.

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.

Soft Polymeric Matrix as a Macroscopic Cage for Magnetically Modulating Reversible Nanoscale Ligand Presentation

A physical, noninvasive, and reversible means of controlling the nanoscale presentation of bioactive ligands is highly desirable for regulating and investigating the time-dependent responses of cells, including stem cells. Herein we report a magnetically actuated dynamic cell culture platform consisting of a soft hydrogel substrate conjugated with RGD-bearing magnetic nanoparticle (RGD-MNP). The downward/upward magnetic attraction conceals/promotes the presentation of the RGD-MNP in/on the soft hydrogel matrix, thereby inhibiting/enhancing the cell adhesion and mechanosensing-dependent differentiation. Meanwhile, the lateral magnetic attraction promotes the unidirectional migration of cells in the opposite direction on the hydrogel. Furthermore, cyclic switching between the "Exposed" and "Hidden" conditions induces the repeated cycles of differentiation/dedifferentiation of hMSCs which significantly enhances the differentiation potential of hMSCs. Our design approach capitalizes on the bulk biomaterial matrix as the macroscopic caging structure to enable dynamic regulation of cell-matrix interactions reversibly, which is hard to achieve by using conventional cell culture systems.

Capture and selective release of multiple types of circulating tumor cells using smart DNAzyme probes

The effective capture, release and reanalysis of circulating tumor cells (CTCs) are of great significance to acquire tumor information and promote the progress of tumor therapy. Particularly, the selective release of multiple types of CTCs is critical to further study; however, it is still a great challenge. To meet this challenge, we designed a smart DNAzyme probe-based platform. By combining multiple targeting aptamers and multiple metal ion responsive DNAzymes, efficient capture and selective release of multiple types CTCs were realized. Sgc8c aptamer integrated Cu2+-dependent DNAzyme and TD05 aptamer integrated Mg2+-dependent DNAzyme can capture CCRF-CEM cells and Ramos cells respectively on the substrate. With the addition of Cu2+ or Mg2+, CCRF-CEM cells or Ramos cells will be released from the substrate with specific selectivity. Furthermore, our platform has been successfully demonstrated in the whole blood sample. Therefore, our capture/release platform will benefit research on the molecular analysis of CTCs after release and has great potential for cancer diagnosis and individualized treatment.

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

The isolation of viable circulating tumor cells (CTCs) from blood is of paramount significance for early stage detection and individualized therapy of cancer. Currently, CTCs isolated by conventional magnetic separation methods are tightly coated with magnetic materials even after attempted coating removal treatments, which is not conducive for subsequent analysis of CTCs. Herein, we developed DNA aptamer-functionalized magnetic short nanofibers (aptamer-MSNFs) for efficient capture and release of CTCs. In our work, polyethylenimine (PEI)-stabilized Fe₃O₄ nanoparticles with a mean diameter of 22.6 nm were first synthesized and encapsulated within PEI/poly(vinyl alcohol) nanofibers via a blended electrospinning process. After a homogenization treatment to acquire the MSNFs, surface conjugation of the DNA aptamer was performed through thiol-maleimide coupling. The formed aptamer-MSNFs, with a mean diameter of 350 nm and an average length of 9.6 μm, display a saturated magnetization of 12.3 emu g^-1, are capable of specifically capturing cancer cells with an efficiency of 87%, and enable the nondestructive release of cancer cells with a release efficiency of 91% after nuclease treatment. In particular, the prepared aptamer-MSNFs displayed a significantly higher release efficiency than commercial magnetic beads. The designed aptamer-MSNFs may hold great promise for CTC capture and release as well as for other cell sorting applications.

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.

DNA Framework-Programmed Cell Capture via Topology-Engineered Receptor-Ligand Interactions

Receptor-ligand interactions (RLIs) that play pivotal roles in living organisms are often depicted with the classic keys-and-locks model. Nevertheless, RLIs on the cell surface are generally highly complex and nonlinear, partially due to the noncontinuous and dynamic distribution of receptors on extracellular membranes. Here, we develop a tetrahedral DNA framework (TDF)-programmed approach to topologically engineer RLIs on the cell membrane, which enables active recruitment-binding of clustered receptors for high-affinity capture of circulating tumor cells (CTCs). The four vertices of a TDF afford orthogonal anchoring of ligands with spatial organization, based on which we synthesized n-simplexes harboring 1-3 aptamers targeting epithelial cell adhesion molecule (EpCAM) that are overexpressed on the membrane of tumor cells. The 2-simplex with three aptamers not only shows increased binding affinity (∼19-fold) but prevents endocytosis by cells. By using 2-simplex as the capture probe, we demonstrate the high-efficiency CTC capture, which is challenged in real clinical breast cancer patient samples. This TDF-programmed platform thus provides a powerful means for studying RLIs in physiological settings and for cancer diagnosis.

An Acoustic Droplet-Induced Enzyme Responsive Platform for the Capture and On-Demand Release of Single Circulating Tumor Cells

The recovery of rare single circulating tumor cells (CTCs) from patients has great potential to facilitate the study of cell heterogeneity and cancer metastasis, which may promote the development of individualized cancer immunotherapy. Herein, a versatile single-cell recovery approach that utilizes an acoustic droplet-induced enzyme responsive platform for the capture and on-demand release of single CTCs is proposed. The platform combines a multifunctional enzyme-responsive gelatin nanoparticle (GNP)-decorated substrate (GNP-chip) for specific capture with an acoustic droplet positioning technique to realize on-demand release of single CTCs. The acoustic droplet dispenser is employed to generate oxidized alginate microdroplets containing the MMP-9 enzyme (OA-MMP-9) with controllable size and precise positioning upon the cell-attached GNP-chip, allowing controlled cell-surface biodegradation under enzymatic reactions followed by calcium chloride (CaCl₂) solution treatment to form single-cell encapsulated calcium alginate hydrogels. Benefitting from the existence of hydrogels, the released cells could be efficiently recovered by microcapillary. Results demonstrate that the encapsulated cells maintain good cell morphology in the hydrogels, which allow further single-cell nucleic acid analysis. As a proof-of-concept platform, this approach enables reliable and efficient retrieval of single CTCs and holds the potential for versatility in single-cell analysis systems.

Integration of Hierarchical Micro-/Nanostructures in a Microfluidic Chip for Efficient and Selective Isolation of Rare Tumor Cells

Circulating tumor cells (CTCs) are important clinical markers for both cancer early diagnosis and prognosis. Various techniques have been developed in the past decade to isolate and quantify these cells from the blood while microfluidic technology attracts significant attention due to better controlled microenvironment. When combined with advanced nanotechnologies, CTC isolation performance in microfluidic devices can be further improved. In this article, by extending the wavy-herringbone concept developed earlier in our team, we prepared a hierarchical microfluidic chip by introducing a uniform coating of nanoparticles with anti-epithelial cell adhesion molecule (EpCAM) on wavy microgrooves. This hierarchical structured platform not only maintains the capture purity of the wavy-herringbone structure but improves the capture efficiency thanks to the larger surface area to volume ratio brought by nanoparticles. Our results demonstrated a capture efficiency of almost 100% at a low shear rate of 60/s. Even at a higher shear rate of 400/s, the hierarchical micro/nanostructures demonstrated an enhancement of up to ~3-fold for capture efficiency (i.e., 70%) and ~1.5-fold for capture purity (i.e., 68%), compared to wavy-herringbone structures without nanoparticle coating. With these promising results, this hierarchical structured platform represents a technological advancement for CTC isolation and cancer care.

TiO2 nanopillar arrays coated with gelatin film for efficient capture and undamaged release of circulating tumor cells

Circulating tumor cells (CTCs) are important for the detection and treatment of cancer. Nevertheless, a low density of circulating tumor cells makes the capture and release of CTCs an obstacle. In this work, TiO₂ nanopillar arrays coated with gelatin film were synthesized for efficient capture and undamaged release of circulating tumor cells. The scanning electron microscope and atomic force microscope images demonstrate that the substrate has a certain roughness. The interaction between the cell membrane and the nanostructure substrate contributes to the efficient capture of CTC (capture efficiency up to 94.98%). The gelatin layer has excellent biocompatibility and can be rapidly digested by matrix metalloproteinase (MMP9), which realizes the non-destructive release of CTCs (0.1 mg ml^-1, 5 min, nearly 100% release efficiency, activity 100%). Therefore, by our strategy, the CTCs can be efficiently captured and released undamaged, which is important for subsequent analysis.

Superhydrophobic hierarchical fiber/bead composite membranes for efficient treatment of burns

One of the current challenges in burn wound care is the development of multifunctional dressings that can protect the wound from bacteria or organisms and promote skin regeneration and tissue reconstitution. To this end, we report the design and fabrication of a composite electrospun membrane, comprised of electrospun polylactide: poly(vinyl pyrrolidone)/polylactide: poly(ethylene glycol) (PLA:PVP/PLA:PEG) core/shell fibers loaded with bioactive agents, as a functionally integrated wound dressing for efficient burns treatment. Different mass ratios of PLA:PVP in the shell were screened to optimize mechanical, physicochemical, and biological properties, in addition to controlled release profiles of loaded antimicrobial peptides (AMPs) from the fibers for desirable antibacterial activity. Fibroblasts were shown to readily adhere and proliferate when cultured on the membrane, indicating good in vitro cytocompatibility. The introduction of PLA beads by electrospraying on one side of the membrane resulted in biomimetic micro-nanostructures similar to those of lotus leaves. This designer structure rendered the composite membranes with superhydrophobic property to inhibit the adhesion/spreading of exogenous bacteria and other microbes. The administration of the resulting composite fibrous membrane on burnt skin in an infected rat model led to faster healing than a conventional product (sterile silicone membrane) and control detailed herein. These composite fibrous membranes loaded with bioactive drugs provide an integrated strategy for promoting burn wound healing and skin regeneration. STATEMENT OF SIGNIFICANCE: To address an urgent need in complex clinical requirements on developing a new generation of wound dressings with integrated functionalities. This article reports research work on a hierarchical fiber/bead composite membranes design, which combines a lotus-leaf-like superhydrophobic surface with drugs preloaded in the core and shell of fibers for effective burn treatment. This demonstrates a balance between simplified preparation processes and increased multifunctionality of the wound dressings. The creation of hierarchically structured surfaces can be readily achieved by electrospinning, and the composite dressings possessed a considerable mechanical strength, effective wound exudate absorption and permeability, good biocompatibility, broad antibacterial ability and promoting wound healing etc. Thus, our work unveils a promising strategy for the development of functionally integrated wound dressings for burn wound care.

Traceless aptamer-mediated isolation of CD8+ T cells for chimeric antigen receptor T-cell therapy

Chimeric antigen receptor T-cell therapies using defined product compositions require high-purity T-cell isolation systems that, unlike immunomagnetic positive enrichment, are inexpensive and leave no trace on the final cell product. Here, we show that DNA aptamers (generated with a modified cell-SELEX procedure to display low-nanomolar affinity for the T-cell marker CD8) enable the traceless isolation of pure CD8⁺ T cells at low cost and high yield. Captured CD8⁺ T cells are released label-free by complementary oligonucleotides that undergo toehold-mediated strand displacement with the aptamer. We also show that chimeric antigen receptor T cells manufactured from these cells are comparable to antibody-isolated chimeric antigen receptor T cells in proliferation, phenotype, effector function and antitumour activity in a mouse model of B-cell lymphoma. By employing multiple aptamers and the corresponding complementary oligonucleotides, aptamer-mediated cell selection could enable the fully synthetic, sequential and traceless isolation of desired lymphocyte subsets from a single system.

DNA-mediated reversible capture and release of circulating tumor cells with a multivalent dual-specific aptamer coating network

DNA-triggered reversible isolation and recovery of circulating tumor cells (CTCs) is presented based on a multivalent dual-specific aptamer-tethered rolling circle amplification (MA-RCA) network. The multivalent binding sites endow the MA-RCA network with a strong binding ability towards CTCs, and the repeated cell capture/release processes are also actualized in a noninvasive manner.

Size-matching hierarchical micropillar arrays for detecting circulating tumor cells in breast cancer patients' whole blood

Circulating tumor cells (CTCs) are important markers for cancer diagnosis and treatment, but it is still a challenge to recognize and isolate CTCs because they are very rare in the blood. To selectively recognize CTCs and improve the capture efficiency, micro/nanostructured substrates have been fabricated for this application; however the size of CTCs is often ignored in designing and engineering micro/nanostructured substrates. Herein, a spiky polymer micropillar array is fabricated for capturing CTCs with high efficiency. The surface of the micropillar is cactus-like, and is composed of nanospikes. This hierarchical polymer array is designed according to the size of CTCs, which allows for more interactions of the CTCs with the array by setting the size of gaps among the micropillars to match with the CTCs. This polymer array is created by molding on an ordered silicon array, and then it is coated with an antiepithelial cell adhesion molecule antibody (anti-EpCAM). After co-culture with MCF-7 cells for 45 min, the capture efficiency of this array for CTCs is up to 91% ± 2%. Moreover, the anti-EpCAM modified polymer micropillar arrays present an excellent capacity to isolate CTCs from the whole blood samples of breast cancer patients. This study may provide a new concept for capturing target cells by designing and engineering micro/nanostructured substrates according to the size of target cells.

Anisotropic Ligand Nanogeometry Modulates the Adhesion and Polarization State of Macrophages

Material implants trigger host reactions generated by cells, such as macrophages, which display dynamic adhesion and polarization including M1 inflammatory state and M2 anti-inflammatory state. Creating materials that enable diverse nanoscale display of integrin-binding groups, such as RGD ligand, can unravel nanoscale recruitment and ligation of integrin, which modulate cellular adhesion and activation. Here, we synthesized gold nanorods (GNRs) with various nanoscale anisotropies (i.e., aspect ratios, ARs), but in similar surface areas, and controlled their substrate conjugation to display an anisotropic ligand nanogeometry without modulating ligand density. Using nanoscale immunolabeling, we demonstrated that highly anisotropic ligand-coated GNRs ("AR4" and "AR7") facilitated the recruitment of integrin β1 on macrophages to their nanoscale surfaces. Consequently, highly anisotropic GNRs (e.g., "AR4" and "AR7") elevated the adhesion and M2 state of macrophages, with the inhibition of their M1 state in the culture and mice, entailing rho-associated protein kinase. This nanoscale anisotropic nanogeometry provides a novel and critical parameter to be considered in the generation of biomaterials to potentially modulate host reactions to the implants for immunomodulatory tissue regeneration.

An In Situ Reversible Heterodimeric Nanoswitch Controlled by Metal-Ion-Ligand Coordination Regulates the Mechanosensing and Differentiation of Stem Cells

In situ and cytocompatible nanoswitching by external stimuli is highly appealing for reversibly regulating cellular adhesion and functions in vivo. Here, a heterodimeric nanoswitch is designed to facilitate in situ switchable and combinatorial presentation of integrin-binding cell-adhesive moieties, such as Mg²⁺ and Arg-Gly-Asp (RGD) ligand in nanostructures. In situ reversible nanoswitching is controlled by convertible coordination between bioactive Mg²⁺ and bisphosphonate (BP) ligand. A BP-coated gold-nanoparticle monomer (BP-AuNP) on a substrate is prepared to allow in situ assembly of cell-adhesive Mg²⁺ -active Mg-BP nanoparticles (NPs) on a BP-AuNP surface via Mg²⁺ -BP coordination, yielding heterodimeric nanostructures (switching "ON"). Ethylenediaminetetraacetic acid (EDTA)-based Mg²⁺ chelation allows in situ disassembly of Mg²⁺ -BP NP, reverting to Mg²⁺ -free monomer (switching "OFF"). This in situ reversible nanoswitching on and off of cell-adhesive Mg²⁺ presentation allows reversible cell adhesion and release in vivo, respectively, and spatiotemporally controls cyclic cell adhesion. In situ heterodimeric assembly of dual RGD ligand- and Mg²⁺ -active RGD-BP-Mg²⁺ NP (switching "Dual ON") further tunes and promotes focal adhesion, spreading, and differentiation of stem cells. The modular nature of this in situ nanoswitch can accommodate various bioactive nanostructures via metal-ion-ligand coordination to regulate diverse cellular functions in vivo in reversible and compatible manner.

Functional-DNA-Driven Dynamic Nanoconstructs for Biomolecule Capture and Drug Delivery

The discovery of sequence-specific hybridization has allowed the development of DNA nanotechnology, which is divided into two categories: 1) structural DNA nanotechnology, which utilizes DNA as a biopolymer; and 2) dynamic DNA nanotechnology, which focuses on the catalytic reactions or displacement of DNA structures. Recently, numerous attempts have been made to combine DNA nanotechnologies with functional DNAs such as aptamers, DNAzymes, amplified DNA, polymer-conjugated DNA, and DNA loaded on functional nanoparticles for various applications; thus, the new interdisciplinary research field of "functional DNA nanotechnology" is initiated. In particular, a fine-tuned nanostructure composed of functional DNAs has shown immense potential as a programmable nanomachine by controlling DNA dynamics triggered by specific environments. Moreover, the programmability and predictability of functional DNA have enabled the use of DNA nanostructures as nanomedicines for various biomedical applications, such as cargo delivery and molecular drugs via stimuli-mediated dynamic structural changes of functional DNAs. Here, the concepts and recent case studies of functional DNA nanotechnology and nanostructures in nanomedicine are reviewed, and future prospects of functional DNA for nanomedicine are indicated.

Programmable hydrogels

Programmable hydrogels are defined as hydrogels that are able to change their properties and functions periodically, reversibly and/or sequentially on demand. They are different from those responsive hydrogels whose changes are passive or cannot be stopped or reversed once started and vice versa. The purpose of this review is to summarize major progress in developing programmable hydrogels from the viewpoints of principles, functions and biomedical applications. The principles are first introduced in three categories including biological, chemical and physical stimulation. With the stimulation, programmable hydrogels can undergo functional changes in dimension, mechanical support, cell attachment and molecular sequestration, which are introduced in the middle of this review. The last section is focused on the introduction and discussion of four biomedical applications including mechanistic studies in mechanobiology, tissue engineering, cell separation and protein delivery.

Dual-Responsive Self-Assembled Monolayer for Specific Capture and On-Demand Release of Live Cells

We report a dual-responsive self-assembled monolayer (SAM) on a well-defined rough gold substrate for dynamic capture and release of live cells. By incorporating 5'-triphosphate (ATP) aptamer into a SAM, we can accurately isolate specific cell types and subsequently release captured cells at either population or desired-group (or even single-cell) levels. On one hand, the whole SAMs can be disassembled through addition of ATP solution, leading to the entire release of the captured cells from the supported substrate. On the other hand, desired cells can be selectively released using near-infrared light irradiation, with relatively high spatial and temporal precision. The proposed dual-responsive cell capture-and-release system is biologically friendly and is reusable with another round of modification, showing great usefulness in cancer diagnosis and molecular analysis.

Magnetic Manipulation of Reversible Nanocaging Controls In Vivo Adhesion and Polarization of Macrophages

Macrophages are key immune cells that perform various physiological functions, such as the maintenance of homeostasis, host defense, disease progression, and tissue regeneration. Macrophages adopt distinctly polarized phenotypes, such as pro-inflammatory M1 phenotype or anti-inflammatory (pro-healing) M2 phenotype, to execute disparate functions. The remotely controlled reversible uncaging of bioactive ligands, such as Arg-Gly-Asp (RGD) peptide, is an appealing approach for temporally regulating the adhesion and resultant polarization of macrophages on implants in vivo. Here, we utilize physical and reversible uncaging of RGD by a magnetic field that allows facile tissue penetration. We first conjugated a RGD-bearing gold nanoparticle (GNP) to the substrate and then a magnetic nanocage (MNC) to the GNP via a flexible linker to form the heterodimeric nanostructure. We magnetically manipulated nanoscale displacement of MNC and thus its proximity to the GNP to reversibly uncage and cage RGD. The uncaging of RGD temporally promoted the adhesion and subsequent M2 polarization of macrophages while inhibiting their M1 polarization both in vitro and in vivo. The RGD uncaging-mediated adhesion and M2 polarization of macrophages involved rho-associated protein kinase signaling. This study demonstrates physical and reversible uncaging of RGD to regulate the adhesion and polarization of host macrophages in vivo. This approach of magnetically regulating the heterodimer conformation for physical and reversible uncaging of RGD offers the promising potential to manipulate inflammatory or tissue-regenerative immune responses to the implants in vivo.

Frosted Slides Decorated with Silica Nanowires for Detecting Circulating Tumor Cells from Prostate Cancer Patients

Developing low-cost and highly efficient nanobiochips are important for liquid biopsies, real-time monitoring, and precision medicine. By in situ growth of silica nanowires on a commercial frosted slide, we develop a biochip for effective circulating tumor cells (CTCs) detection after modifying epithelial cell adhesion molecule antibody (anti-EpCAM). The biochip shows the specificity and high capture efficiency of 85.4 ± 8.3% for prostate cancer cell line (PC-3). The microsized frosted slides and silica nanowires allow enhanced efficiency in capture EpCAM positive cells by synergistic topographic interactions. And the capture efficiency of biochip increased with the increase of silica nanowires length on frosted slide. The biochip shows that micro/nanocomposite structures improve the capture efficiency of PC-3 more than 70% toward plain slide. Furthermore, the nanobiochip has been successfully applied to identify CTCs from whole blood specimens of prostate cancer patients. Thus, this frosted slide-based biochip may provide a cheap and effective way of clinical monitoring of CTCs.

Manipulating cell fate: dynamic control of cell behaviors on functional platforms

We review the recent advances and new horizons in the dynamic control of cell behaviors on functional platforms and their applications.

Microfluidic channel-coupled 3D quartz nanohole arrays for high capture and release efficiency of BT20 cancer cells

Nanostructured materials, such as silicon nanowires, quartz nanostructures, and polymer-modified nanostructures, are a promising new class of materials for the capture and enumeration of very rare tumor cells, including circulating tumor cells (CTCs), to examine their biological characteristics in whole blood of cancer patients. These cells can then be used for transplantation, anti-tumor cell therapy, and cell-secreted protein studies. It is believed that 3-dimensional (3D) nanostructured substrates efficiently enhance cell capture yields due to the increased local contacts between the 3D nanostructures and extracellular extensions of the tumor cells. Recent studies have been performed with enhanced cell capture yields thanks to various nanostructured platforms; however, there remains an urgent need both to capture and release viable rare tumor cells for further molecular (i.e., protein) analysis and to develop patient-specific drugs. Here, we first demonstrate that our 3D quartz nanohole array (QNHA) tumor cell capture and release system allows us not only to selectively capture rare tumor cells, but also to release the cells with high capture and release rates. This system was developed using streptavidin (STR)-functionalized QNHA (STR-QNHA) with a microfluidic channel. Our system has ideal cell-separation yields of as high as 85-91% and high release rates of >90% for the BT20 cell line. We suggest that the use of a microfluidic channel technique coupled with a STR-QNHA cell capture and release chip (STR-QNHA cell chip) would be a powerful and simple process to evaluate the capture, enumeration, and release of CTCs from patient whole blood for studying further cell therapy and tumor-cell-secreted molecules.

Capturing Circulating Tumor Cells through a Combination of Hierarchical Nanotopography and Surface Chemistry

Circulating tumor cells (CTCs) have become known as minimally invasive multifunctional biomarkers for earlier diagnosis, prognosis, recurrence risk assessment, and therapeutic monitoring in recent years. However, effectively capturing these CTCs is still difficult because of the extremely low abundance of CTCs and the diverse phenotypes of cancer cells. In this study, we present a novel necklace-like polydopamine nanosphere (PDA NS)/alginate composite nanofiber with a hierarchical nanotopographical structure and a surface chemical signal for capturing the CTCs. The height of the nanotopography, which is formed by connecting PDA NSs with nanofibers via electrospinning, can be easily adjusted by changing the size of the PDA NSs. Four types of cancer cells are employed to investigate the capture efficiency of the fiber. More importantly, in a blood environment containing rare cancer cells, the fiber still has a great ability to capture these cells. Therefore, this nanofiber is identified as a potential device for the diagnosis of cancer.

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.

Mapping cell behavior across a wide range of vertical silicon nanocolumn densities

Over the past decade, vertical nanostructures have provided novel approaches for biomedical applications such as intracellular delivery/detection, specific cell capture, membrane potential measurement, and cellular activity regulation. Although the feasibility of the vertical nanostructures as a new biological tool has been thoroughly demonstrated, a better understanding of cell behavior on vertical nanostructures, in particular the effects of geometry, is essential for advanced applications. To investigate the cell behavior according to the variation of the spacing between vertical nanostructures, we have interfaced fibroblasts (NIH3T3) with density-controlled vertical silicon nanocolumn arrays (vSNAs). Over a wide range of vSNA densities, we observe three distinct cell settling regimes and investigate both overall cell behavior (adhesions, morphology, and mobility) and detailed biomacromolecule variance (F-actin and focal adhesion) across these regimes. We expect that these systematic observations could serve as a guide for improved nanostructure array design for the desired cell manipulation.

Nanoscale silicon for subcellular biointerfaces

Semiconductor nanomaterials are emerging as a class of materials that can push the fundamental limits of current biomedical devices and possibly revolutionize healthcare. In particular, silicon nanostructures have been proven to be attractive systems for integrating nanoscale machines in biology because of their tunable electronic and optical properties, low cytotoxicity, and the vast microfabrication toolbox available for silicon. Studies have demonstrated that the implementation of next-generation silicon-based biomedical devices can benefit from the rational design of their nanoscale components. In this review, we will discuss some recent progress in this area, with a particular focus on the chemical synthesis of new silicon nanostructures and their emerging applications ranging from fundamental biophysical studies to clinical relevance.

Efficient Capture of Cancer Cells by Their Replicated Surfaces Reveals Multiscale Topographic Interactions Coupled with Molecular Recognition

Cell-surface topographic interactions can direct the design of biointerfaces, which have been widely used in isolation of circulating tumor cells or fundamental cell biological research. By using three kinds of cancer cell-replicated surfaces with differentiated structures, we uncover that multiscale-cooperative topographic interactions (at both nanoscale and microscale) coupled with molecular recognition enable efficient and specific isolation of cancer cells. The cell replicas precisely inherit the structural features from the original cancer cells, providing not only preferable structures for matching with cancer cells but also a unique platform to interrogate whether certain cancer cells can optimally match with their own replicated surfaces. The results reveal that cancer cells do not show preferential recognitions to their respective replicas, while the capture agent-modified surfaces with hierarchical structures exhibit improved cancer cell capture efficiencies. Two levels of topographic interactions between cancer cells and cell replica surfaces exist. Nanoscale filopodia on cancer cells can topographically interact with different nanostructures on replica surfaces. In addition, microscale concave/convex on surfaces provide suitable sites for trapping cancer cells. This study may promote smart design of multiscale biofunctional materials that can specifically recognize cancer cells.

Enrichment and single-cell analysis of circulating tumor cells

Up to 90% of cancer-related deaths are caused by metastatic cancer. Circulating tumor cells (CTCs), a type of cancer cell that spreads through the blood after detaching from a solid tumor, are essential for the establishment of distant metastasis for a given cancer. As a new type of liquid biopsy, analysis of CTCs offers the possibility to avoid invasive tissue biopsy procedures with practical implications for diagnostics. The fundamental challenges of analyzing and profiling CTCs are the extremely low abundances of CTCs in the blood and the intrinsic heterogeneity of CTCs. Various technologies have been proposed for the enrichment and single-cell analysis of CTCs. This review aims to provide in-depth insights into CTC analysis, including various techniques for isolation of CTCs with capture methods based on physical and biochemical principles, and single-cell analysis of CTCs at the genomic, proteomic and phenotypic level, as well as current developmental trends and promising research directions.