Hydrophobic interaction-mediated capture and release of cancer cells on thermoresponsive nanostructured surfaces

Multifunctional Nanofibers for Specific Purification and Release of CTCs

Recovering pure and viable circulating tumor cells (CTCs) from blood has been a challenging task for molecular characterization and functional analysis, which has attracted wide attention these days. Herein, we fabricate a thermoresponsive chitosan nanofiber substrate to effectively capture, purify, and release the target cancer cells, assisted by PNIPAAm brushes and DNA hybridization. The PNIPAAm brushes are designed to enable WBCs to detach from aptamer-PNIPAAm-chitosan-nanofiber (aptamer-P-CNFs) surfaces during the conformational transition. Meanwhile these specific captured CTCs are retained at a high purity. Moreover, effective and intact release of CTCs from the substrates without any foreign agents is realized by complementary sequences efficiently hybridizing with aptamers, and the specific cell release makes CTCs further purified. The present work provides a new strategy in the design of biointerface for recovering target CTCs from whole blood samples with high purity.

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.

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

The development of novel bioinspired surfaces with hierarchical micro- and nanoscale topographic structures for efficient capture and release of circulating tumor cells (CTCs) is reported. The capture of CTCs, facilitated by surface-immobilized epithelial cell adhesion molecule antibodies (anti-EpCAM), was shown to be significantly enhanced in novel three-dimensional hierarchically structured surfaces that were fabricated by replicating the natural micro- and nanostructures of rose petals. Under static conditions, these hierarchical capture substrates exhibited up to 6 times higher cell capture ability at concentrations of 100 cells mL^-1 in contrast to flat anti-EpCAM-functionalized polydimethylsiloxane (PDMS) surfaces. As indicated by scanning electron microscopy (SEM) and immunofluorescent images, this enhancement can be in large part attributed to the topographical interaction between nanoscale cell surface components and nanostructures on the substrate. Similarly, the increased surface area affords a higher nominal coverage of anti-EpCAM, which increases the number of available binding sites for cell capture. By treating the substrates with the biocompatible reductant glutathione (GSH), up to 85% of the captured cells were released, which displayed over 98% cell viability after culturing on tissue culture polystyrene (TCP) for 24 h. Therefore, these bioinspired hierarchically structured and functionalized substrates can be successfully applied to capture CTCs, as well as release CTCs for subsequent analysis. These findings provide new prospects for designing cell-material interfaces for advanced cell-based biomedical studies in the future.

Solution blow spinning fibres: New immunologically inert substrates for the analysis of cell adhesion and motility

The control of cell behaviour through material geometry is appealing as it avoids the requirement for complex chemical surface modifications. Significant advances in new technologies have been made to the development of polymeric biomaterials with controlled geometry and physico-chemical properties. Solution blow spinning technique has the advantage of ease of use allowing the production of nano or microfibres and the direct fibre deposition on any surface in situ. Yet, in spite of these advantages, very little is known about the influence of such fibres on biological functions such as immune response and cell migration. In this work, we engineered polymeric fibres composed of either pure poly(lactic acid) (PLA) or blends of PLA and polyethylene glycol (PEG) by solution blow spinning and determined their impact on dendritic cells, highly specialised cells essential for immunity and tolerance. We also determined the influence of fibres on cell adhesion and motility. Cells readily interacted with fibres resulting in an intimate contact characterised by accumulation of actin filaments and focal adhesion components at sites of cell-fibre interactions. Moreover, cells were guided along the fibres and actin and focal adhesion components showed a highly dynamic behaviour at cell-fibre interface. Remarkably, fibres did not elicit any substantial increase of activation markers and inflammatory cytokines in dendritic cells, which remained in their immature (inactive) state. Taken together, these findings will be useful for developing new biomaterials for applications in tissue engineering and regenerative medicine.

Bioinspired Smart Peristome Surface for Temperature-Controlled Unidirectional Water Spreading

Unidirectional liquid spreading without energy input has attracted considerable attention due to various potential applications such as biofluidics devices and self-lubrication. Introducing a surface wettable gradient or asymmetric nanostructures onto the surface has successfully harnessed the liquid to spread unidirectionally. However, these surfaces are still plagued with problems that restrict their practical applications: fixed spreading state for a fixed surface, and spreading slowly over a short distance. Herein, bioinspired from the fast continuous unidirectional water transport on the peristome of Nepenthes alata, we report a smart peristome with temperature-controlled unidirectional water spreading. The smart artificial peristome was fabricated by grafting the thermoresponsive material PNIPAAm onto the artificial PDMS peristome. Unidirectional water spreading on the smart peristome can be dynamically regulated by changing the surface temperature. Besides, the water spreading is demonstrated with a remarkable reversibility and stability. By investigating the relationship between liquid spreading distance and wettability, the underlying mechanism was revealed. This work gives a new way to achieve the control of unidirectional liquid spreading available for controllable microfluidics and medical devices.

Large-area assembly of halloysite nanotubes for enhancing the capture of tumor cells

Here, polystyrene sulfonate sodium (PSS) modified Halloysite nanotubes (HNTs) were self-assembled into a patterned coating on a glass substrate with ordered nanotube arrays in a slit-like confined space. The microstructure of the formed patterned HNTs coating was investigated. The formed strips are more regular and almost parallel to each other with an increase in HNTs concentration. The HNTs coating formed from the 2% PSS-HNTs dispersion has the maximum nanotube alignment degree. The patterned HNTs coating was employed to capture tumor cells. The tumor cells can be captured by the HNTs coating effectively compared with a smooth glass surface due to the enhanced topographic interactions between the HNTs coating and cancer cells. The HNTs coating prepared from the 2% PSS-HNTs dispersion has the highest capture yield which is due to the ordered nanotube arrangement and the appropriate surface roughness. The HNTs coating was further conjugated with anti-EpCAM, which leads to the capture yield of MCF-7 cells reaching 92% within 3 h. The HNTs coating can capture 8 MCF-7 cells from 1 mL artificial blood samples spiked with 10 MCF-7 cells, showing the promising applications of HNTs in clinical circulating tumor cell capture for early diagnosis and monitoring of cancer patients.

Label-Free Virus Capture and Release by a Microfluidic Device Integrated with Porous Silicon Nanowire Forest

Viral diseases are perpetual threats to human and animal health. Detection and characterization of viral pathogens require accurate, sensitive, and rapid diagnostic assays. For field and clinical samples, the sample preparation procedures limit the ultimate performance and utility of the overall virus diagnostic protocols. This study presents the development of a microfluidic device embedded with porous silicon nanowire (pSiNW) forest for label-free size-based point-of-care virus capture in a continuous curved flow design. The pSiNW forests with specific interwire spacing are synthesized in situ on both bottom and sidewalls of the microchannels in a batch process. With the enhancement effect of Dean flow, this study demonstrates that about 50% H5N2 avian influenza viruses are physically trapped without device clogging. A unique feature of the device is that captured viruses can be released by inducing self-degradation of the pSiNWs in physiological aqueous environment. About 60% of captured viruses can be released within 24 h for virus culture, subsequent molecular diagnosis, and other virus characterization and analyses. This device performs viable, unbiased, and label-free virus isolation and release. It has great potentials for virus discovery, virus isolation and culture, functional studies of virus pathogenicity, transmission, drug screening, and vaccine development.

Surface-Initiated Controlled Radical Polymerization: State-of-the-Art, Opportunities, and Challenges in Surface and Interface Engineering with Polymer Brushes

The generation of polymer brushes by surface-initiated controlled radical polymerization (SI-CRP) techniques has become a powerful approach to tailor the chemical and physical properties of interfaces and has given rise to great advances in surface and interface engineering. Polymer brushes are defined as thin polymer films in which the individual polymer chains are tethered by one chain end to a solid interface. Significant advances have been made over the past years in the field of polymer brushes. This includes novel developments in SI-CRP, as well as the emergence of novel applications such as catalysis, electronics, nanomaterial synthesis and biosensing. Additionally, polymer brushes prepared via SI-CRP have been utilized to modify the surface of novel substrates such as natural fibers, polymer nanofibers, mesoporous materials, graphene, viruses and protein nanoparticles. The last years have also seen exciting advances in the chemical and physical characterization of polymer brushes, as well as an ever increasing set of computational and simulation tools that allow understanding and predictions of these surface-grafted polymer architectures. The aim of this contribution is to provide a comprehensive review that critically assesses recent advances in the field and highlights the opportunities and challenges for future work.

Superwettable Microchips as a Platform toward Microgravity Biosensing

The construction of the Space Station provides a spaceflight laboratory, which enables us to accomplish tremendous short- and long-duration research such as astronomy, physics, material sciences, and life sciences in a microgravity environment. Continuous innovation and development of spaceflight laboratory prompted us to develop a facile detection approach to meet stringent requirements in a microgravity environment that traditional experimental approaches cannot reach. Here we introduce superhydrophilic microwells onto superhydrophobic substrates that are capable of capturing and transferring microdroplets, demonstrating a proof-of-concept study of a biosensing platform toward microgravity application. The capability of manipulating microdroplets originates from the capillary force of the nanoscale dendritic coating in superhydrophilic microwells. Based on theoretical modeling, capillary forces of the superhydrophilic microwells can dominate the behavior of microdroplets against the gravity. Direct naked-eye observation monitoring of daily physiological markers, such as glucose, calcium, and protein can be achieved by colorimetric tests without the requirement of heavy optical or electrical equipment, which greatly reduced the weight, and will bring a promising clue for biodetection in microgravity environments.

Smart Polymers with Special Wettability

Surface wettability plays a key role in addressing issues ranging from basic life activities to our daily life, and thus being able to control it is an attractive goal. Learning from nature, both of its structure and function, brings us much inspiration in designing smart polymers to tackle this major challenge. Life functions particularly depend on biomolecular recognition-induced interfacial properties from the aqueous phase onto either "soft" cell and tissue or "hard" inorganic bone and tooth surfaces. The driving force is noncovalent weak interactions rather than strong covalent combinations. An overview is provided of the weak interactions that perform vital actions in mediating biological processes, which serve as a basis for elaborating multi-component polymers with special wettabilities. The role of smart polymers from molecular recognitions to macroscopic properties are highlighted. The rationale is that highly selective weak interactions are capable of creating a dynamic synergetic communication in the building components of polymers. Biomolecules could selectively induce conformational transitions of polymer chains, and then drive a switching of physicochemical properties, e.g., roughness, stiffness and compositions, which are an integrated embodiment of macroscopic surface wettabilities.

Antibody-modified hydroxyapatite surfaces for the efficient capture of bladder cancer cells in a patient's urine without recourse to any sample pre-treatment

In this study, we describe a sensitive protocol for the detection of bladder cancer cells in a patient's urine without pre-treatment of the urine sample using antibody-modified hydroxyapatite (HAp) micro/nanostructured surfaces converted from natural seashells under mild biomineralization conditions.

Self-assembled coronene nanofiber arrays: toward integrated organic bioelectronics for efficient isolation, detection, and recovery of cancer cells

Integrated coronene-based nanofiber array devices for circulating tumor cell isolation, detection, and recovery through electrical stimulation.

Rhipsalis (Cactaceae)-like Hierarchical Structure Based Microfluidic Chip for Highly Efficient Isolation of Rare Cancer Cells

The circulating tumor cells (CTCs), originating from the primary tumor, play a vital role in cancer diagnosis, prognosis, disease monitoring, and precise therapy. However, the CTCs are extremely rare in the peripheral bloodstream and hard to be isolated. To overcome current limitations associated with CTC capture and analysis, the strategy incorporating nanostructures with microfluidic devices receives wide attention. Here, we demonstrated a three-dimensional microfluidic device (Rm-chip) for capturing cancer cells with high efficiency by integrating a novel hierarchical structure, the "Rhipsalis (Cactaceae)"-like micropillar array, into the Rm-chip. The PDMS micropillar array was fabricated by soft-lithography and rapid prototyping method, which was then conformally plated with a thin gold layer through electroless plating. EpCAM antibody was modified onto the surface of the micropillars through the thiol-oligonucleotide linkers in order to release captured cancer cells by DNase I treatment. The antibody-functionalized device achieved an average capture efficiency of 88% in PBS and 83.7% in whole blood samples. We believe the Rm-chip provided a convenient, economical, and versatile approach for cell analysis with wide potential applications.

Light-Triggered Specific Cancer Cell Release from Cyclodextrin/Azobenzene and Aptamer-Modified Substrate

Cell adhesion behaviors of stimuli-responsive surfaces have attracted significant attention for their potential biomedical applications. Distinct from temperature and pH stimuli, photoswitching avoids the extra input of thermal energy or chemicals. Herein, we designed a novel reusable cyclodextrin (CD)-modified surface to realize photoswitched specific cell release utilizing host-guest interactions between CD and azobenzene. The azobenzene-grafted specific cell capture agent was assembled onto the CD-modified surface to form a smart surface controlling cell adhesion by light radiation. After UV light irradiation, the azobenzene switched from trans- to cis-isomers, and the cis-azobenzene was not recognized by CD due to the unmatched host-guest pairs; thus, the captured MCF-7 cells could be released. Light-triggered specific cancer cell release with high efficiency may afford a smart surface with significant potential applications for the isolation and analysis of circulating tumor cells.

Inflammation-sensitive in situ smart scaffolding for regenerative medicine

To cope with the rapid evolution of the tissue engineering field, it is now essential to incorporate the use of on-site responsive scaffolds. Therefore, it is of utmost importance to find new 'Intelligent' biomaterials that can respond to the physicochemical changes in the microenvironment. In this present report, we have developed biocompatible stimuli responsive polyaniline-multiwalled carbon nanotube/poly(N-isopropylacrylamide), (PANI-MWCNT/PNIPAm) composite nanofiber networks and demonstrated the physiological temperature coordinated cell grafting phenomenon on its surface. The composite nanofibers were prepared by a two-step process initiated with an assisted in situ polymerization followed by electrospinning. To obtain a smooth surface in individual nanofibers with the thinnest diameter, the component ratios and electrospinning conditions were optimized. The temperature-gated rearrangements of the molecular structure are characterized by FTIR spectroscopy with simultaneous macromolecular architecture changes reflected on the surface morphology, average diameter and pore size as determined by scanning electron microscopy. The stimuli responsiveness of the nanofibers has first been optimized with computational modeling of temperature sensitive components (coil-like and globular conformations) to tune the mechanism for temperature dependent interaction during in situ scaffolding with the cell membrane. The nanofiber networks show excellent biocompatibility, tested with fibroblasts and also show excellent sensitivity to inflammation to combat loco-regional acidosis that delay the wound healing process by an in vitro model that has been developed for testing the proposed responsiveness of the composite nanofiber networks. Cellular adhesion and detachment are regulated through physiological temperature and show normal proliferation of the grafted cells on the composite nanofibers. Thus, we report for the first time, the development of physiological temperature gated inflammation-sensitive smart biomaterials for advanced tissue regeneration and regenerative medicine.

Ultra-Specific Isolation of Circulating Tumor Cells Enables Rare-Cell RNA Profiling

The clinical potential of circulating tumor cells (CTCs) in managing cancer metastasis is significant. However, low CTC isolation purities from patient blood have hindered sensitive molecular assays of these rare cells. Described herein is the ultra-pure isolation of CTCs from patient blood samples and how this platform has enabled highly specific molecular (mRNA and miRNA) profiling of patient CTCs.

Smart Thin Hydrogel Coatings Harnessing Hydrophobicity and Topography to Capture and Release Cancer Cells

Smart thin hydrogel coatings are fabricated to capture and release targeted cancer cells by simultaneously tuning surface hydrophobicity and topography. At physiological temperature, the targeted cancer cells are captured on the hydrophobic and wrinkled coating surface. At room temperature, the captured cells are released from the hydrophilic and smooth coating surface.

Poly(ethylene glycol)-Modified Tapered-Slit Membrane Filter for Efficient Release of Captured Viable Circulating Tumor Cells

The grafting of poly(ethylene glycol) (PEG) onto an SU8 microfilter has been demonstrated for efficient capture and release of circulating tumor cells (CTCs). Previous CTC filters showed low cell release efficiency due to hydrophobic surfaces, even though their capture efficiency was considerable. PEG, a hydrophilic polymeric compound mainly used to form nonfouling thin films on silicon surfaces, induces repulsive force so that the nonspecific adsorption of the surface is incomparably reduced in comparison with unmodified filter surfaces. The effectiveness of PEG-modified CTC filters was verified through lung (H358) and colorectal (SW620) cancer cells spiked, respectively, in phosphate-buffered saline (PBS) and unprocessed whole blood. The modified SU8 filters achieved approximately 37.7% and 22.8% improvement in release efficiency without significant changes in cell viability and capture efficiency. In order to verify the filter's potential for clinical applications, we extended our experiments using cancer patient blood samples. Six blood samples from colorectal and lung cancer patients were processed, and captured CTCs were efficiently released. From these experiments, the present PEG-modified filter captures and releases on average 14 ± 7.4 CTCs/mL, including EpCAM-negative CTCs, which could not be captured by previous single antibody-based methods. The antibody-free isolation with enhanced release efficiency facilitates viable cell retrieval, which is significant to CTC culture and comprehensive molecular study for verifying the mechanism of metastasis and cancer.

Efficient Purification and Release of Circulating Tumor Cells by Synergistic Effect of Biomarker and SiO2 @Gel-Microbead-Based Size Difference Amplification

Microfluidics-based circulating tumor cell (CTC) isolation is achieved by using gelatin-coated silica microbeads conjugated to CTC-specific antibodies. Bead-binding selectively enlarges target cell size, providing efficient high-purity capture. CTCs captured can be further released non-invasively. This stratagem enables high-performance CTC isolation for subsequent studies.

Advanced Materials for the Recognition and Capture of Whole Cells and Microorganisms

Selective cell recognition and capture has recently attracted significant interest due to its potential importance for clinical, diagnostic, environmental, and security applications. Current methods for cell isolation from complex samples are largely dependent on cell size and density, with limited application scope as many of the target cells do not exhibit appreciable differences in this respect. The most recent and forthcoming developments in the area of selective recognition and capture of whole cells, based on natural receptors, as well as synthetic materials utilising physical and chemical properties of the target cell or microorganism, are highlighted. Particular focus is given to the development of cell complementary surfaces using the cells themselves as templating agents, by means of molecular imprinting, and their combination with sensing platforms for rapid cell detection in complex media. The benefits and challenges of each approach are discussed and a perspective of the future of this research area is given.

Near-Infrared Light-Responsive Hydrogel for Specific Recognition and Photothermal Site-Release of Circulating Tumor Cells

Isolation of single circulating tumor cells (CTCs) from patients is a very challenging technique that may promote the process of individualized antitumor therapies. However, there exist few systems capable of highly efficient capture and release of single CTCs with high viability for downstream analysis and culture. Herein, we designed a near-infrared (NIR) light-responsive substrate for highly efficient immunocapture and biocompatible site-release of CTCs by a combination of the photothermal effect of gold nanorods (GNRs) and a thermoresponsive hydrogel. The substrate was fabricated by imprinting target cancer cells on a GNR-pre-embedded gelatin hydrogel. Micro/nanostructures generated by cell imprinting produce artificial receptors for cancer cells to improve capture efficiency. Temperature-responsive gelatin dissolves rapidly at 37 °C; this allows bulk recovery of captured CTCs at physiological temperature or site-specific release of single CTCs by NIR-mediated photothermal activation of embedded GNRs. Furthermore, the system has been applied to capture, individually release, and genetically analyze CTCs from the whole blood of cancer patients. The multifunctional NIR-responsive platform demonstrates excellent performance in capture and site-release of CTCs with high viability, which provides a robust and versatile means toward individualized antitumor therapies and also shows promising potential for dynamically manipulating cell-substrate interactions in vitro.

Efficient Transfection by Using PDMAEMA-Modified SiNWAs as a Platform for Ca(2+)-Dependent Gene Delivery

The major bottleneck for gene delivery lies in the lack of safe and efficient gene vectors and delivery systems. In order to develop a much safer and efficient transfection system, a novel strategy of combining traditional Ca(2+)-dependent transfection with cationic polymer poly(N,N-dimethylamino)ethyl methacrylate (PDMAEMA) modified silicon nanowire arrays (SiNWAs) was proposed in this work. Detailed studies were carried out on the effects of the PDMAEMA polymerization time, the Ca(2+) concentration, and the incubation time of Ca(2+)@DNA complex with PDMAEMA-modified SiNWAs (SN-PDM) on the gene transfection in the cells. The results demonstrated that the transfection efficiency of SN-PDM assisted traditional Ca(2+)-dependent transfection was significantly enhanced compared to those without any surface assistance, and SN-PDM with polymerization time 24 h exhibited the highest efficiency. Moreover, the optimal transfection efficiency was found at the system of a complex containing Ca(2+) (100 mM) and plasmid DNA (pDNA) incubated on SN-PDM for 20 min. Compared with unmodified SiNWAs, SN-PDM has little cytotoxicity and can improve cell attachment. All of these results demonstrated that SN-PDM could significantly enhance Ca(2+)-dependent transfection; this process depends on the amino groups' density of PDMAEMA on the surface, the Ca(2+) concentration, and the available Ca(2+)@DNA complex. Our study provides a potential novel and excellent means of gene delivery for therapeutic applications.

Photoswitched Cell Adhesion on Azobenzene-Containing Self-Assembled Films

Stimuli-responsive surfaces that can regulate and control cell adhesion have attracted much attention for their great potential in diverse biomedical applications. Unlike for pH- and temperature-responsive surfaces, the process of photoswitching requires no additional input of chemicals or thermal energy. In this work, two different photoresponsive azobenzene films are synthesized by chemisorption and electrostatic layer-by-layer (LbL) assembly techniques. The LbL film exhibits a relatively loose packing of azobenzene chromophores compared with the chemisorbed film. The changes in trans/cis isomer ratio of the azobenzene moiety and the corresponding wettability of the LbL films are larger than those of the chemisorbed films under UV light irradiation. The tendency for cell adhesion on the LbL films decreases markedly after UV light irradiation, whereas adhesion on the chemisorbed films decreases only slightly, because the azobenzene chromophores stay densely packed. Interestingly, the tendency for cell adhesion can be considerably increased on rough substrates, the roughness being introduced by use of photolithography and inductively coupled plasma deep etching techniques. For the chemisorbed films on rough substrates, the amount of cells that adhere also changes slightly after UV light irradiation, whereas, the amount of cells that adhere to LbL films on rough substrates decreases significantly.

Tunable Thermal-Sensitive Polymer-Graphene Oxide Composite for Efficient Capture and Release of Viable Circulating Tumor Cells

A highly sensitive microfluidic system to capture circulating tumor cells from whole blood of cancer patients is presented. The device incorporates graphene oxide into a thermoresponsive polymer film to serve as the first step of an antibody functionalization chemistry. By decreasing the temperature, captured cells may be released for subsequent analysis.

Enzymatic cleavage of uracil-containing single-stranded DNA linkers for the efficient release of affinity-selected circulating tumor cells

We report a novel strategy to enzymatically release affinity-selected cells, such as circulating tumor cells (CTCs), from surfaces with high efficiency (∼90%) while maintaining cell viability (>85%). The strategy utilizes single-stranded DNAs that link a capture antibody to the surfaces of a CTC selection device. The DNA linkers contain a uracil residue that can be cleaved.

Zn or O? An Atomic Level Comparison on Antibacterial Activities of Zinc Oxides

For the first time, the influence of different types of atoms (Zn and O) on the antibacterial activities of nanosized ZnO was quantitatively evaluated with the aid of a 3D-printing-manufactured evaluation system. Two different outermost atomic layers were manufactured separately by using an ALD (atomic layer deposition) method. Interestingly, we found that each outermost atomic layer exhibited certain differences against gram-positive or gram-negative bacterial species. Zinc atoms as outermost layer (ZnO-Zn) showed a more pronounced antibacterial effect towards gram-negative E. coli (Escherichia coli), whereas oxygen atoms (ZnO-O) showed a stronger antibacterial activity against gram-positive S. aureus (Staphylococcus aureus). A possible antibacterial mechanism has been comprehensively discussed from different perspectives, including Zn(2+) concentrations, oxygen vacancies, photocatalytic activities and the DNA structural characteristics of different bacterial species.

DNA orientation-specific adhesion and patterning of living mammalian cells on self-assembled DNA monolayers

To better understand cell behaviors on substrates, the precise control of density and orientation of cell-specific ligands remains a great challenge. In this study, we established an easy-to-use approach to manipulate the adhesion and patterning of mammalian cells on gold substrates. We prepared DNA self-assembled monolayers (DNA-SAMs) on gold substrates and found that the sequence-specific orientation of DNA-SAMs played an important role in modulating cell adhesion. We also found that the DNA-SAMs on gold substrates could be used as a potentially universal cell culture substrate, which showed properties similar to cationic polymers (e.g. poly-l lysine, PLL) substrates. Furthermore, we could manipulate cell adhesion by tuning the length of poly adenine (polyA) in the DNA sequence. We also prepared a DNA aptamer-based SAM to regulate cell adhesion by exploiting stimuli-responsive conformational change of the aptamer. By using the well-established DNA spotting technology, we patterned cells on DNA-SAMs to form a spot matrix and four English letters "CELL". Our findings suggest that DNA-SAMs on gold substrates are potentially useful for making smart surfaces for cell studies, thus introducing a new platform for cell/tissue engineering research.

A chip assisted immunomagnetic separation system for the efficient capture and in situ identification of circulating tumor cells

The detection of circulating tumor cells (CTCs), a kind of "liquid biopsy", represents a potential alternative to noninvasive detection, characterization and monitoring of carcinoma. Many previous studies have shown that the number of CTCs has a significant relationship with the stage of cancer. However, CTC enrichment and detection remain notoriously difficult because they are extremely rare in the bloodstream. Herein, aided by a microfluidic device, an immunomagnetic separation system was applied to efficiently capture and in situ identify circulating tumor cells. Magnetic nanospheres (MNs) were modified with an anti-epithelial-cell-adhesion-molecule (anti-EpCAM) antibody to fabricate immunomagnetic nanospheres (IMNs). IMNs were then loaded into the magnetic field controllable microfluidic chip to form uniform IMN patterns. The IMN patterns maintained good stability during the whole processes including enrichment, washing and identification. Apart from its simple manufacture process, the obtained microfluidic device was capable of capturing CTCs from the bloodstream with an efficiency higher than 94%. The captured cells could be directly visualized with an inverted fluorescence microscope in situ by immunocytochemistry (ICC) identification, which decreased cell loss effectively. Besides that, the CTCs could be recovered completely just by PBS washing after removal of the permanent magnets. It was observed that all the processes showed negligible influence on cell viability (viability up to 93%) and that the captured cells could be re-cultured for more than 5 passages after release without disassociating IMNs. In addition, the device was applied to clinical samples and almost all the samples from patients showed positive results, which suggests it could serve as a valuable tool for CTC enrichment and detection in the clinic.

A Smart Antibacterial Surface for the On-Demand Killing and Releasing of Bacteria

For various human healthcare and industrial applications, endowing surfaces with the capability to not only efficiently kill bacteria but also release dead bacteria in a rapid and repeatable fashion is a promising but challenging effort. In this work, the synergistic effects of combining stimuli-responsive polymers and nanomaterials with unique topographies to achieve smart antibacterial surfaces with on-demand switchable functionalities are explored. Silicon nanowire arrays are modified with a pH-responsive polymer, poly(methacrylic acid), which serves as both a dynamic reservoir for the controllable loading and release of a natural antimicrobial lysozyme and a self-cleaning platform for the release of dead bacteria and the reloading of new lysozyme for repeatable applications. The functionality of the surface can be simply switched via step-wise modification of the environmental pH and can be effectively maintained after several kill-release cycles. These results offer a new methodology for the engineering of surfaces with switchable functionalities for a variety of practical applications in the biomedical and biotechnology fields.

Cell-Capture and Release Platform Based on Peptide-Aptamer-Modified Nanowires

Nanowires have attracted much attention due to their potential bioapplications, such as delivery of drugs or sensing devices. Here we report the development of a unique cell-capture and release platform based on nanowires. The combination of nanowires, surface-binding peptides, and cell-targeting aptamers leads to specific and efficient capture of cancer cells. Moreover, the binding processes are reversible, which is not only useful for downstream analysis but also for reusability of the substrate. Our work provides a new method in the design of the cell-capture and release platform, which may open up new opportunities of developing cell-separation and diagnosis systems based on cell-capture techniques.

A smart core-sheath nanofiber that captures and releases red blood cells from the blood

A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.

Hierarchical Nanowire Arrays as Three-Dimensional Fractal Nanobiointerfaces for High Efficient Capture of Cancer Cells

A hierarchical assembled ITO nanowire array with both horizontal and vertical nanowire branches was fabricated as a new three-dimensional fractal nanobiointerface for efficient cancer cell capture. Comparing with ITO nanowire array without branches, this fractal nanobiointerface exhibited much higher efficiency (89% vs 67%) and specificity in capturing cancer cells and took shorter time (35 vs 45 min) to reach the maximal capture efficiency. As indicated by the immunofluorescent and ESEM images, this enhancement can be attributed to the improvement of topographical interaction between cells and the substrate. The introduction of horizontal and vertical nanowire branches makes the substrate topographically match better with cell filopodia and provides more binding sites for cell capture. The live/dead cell staining and proliferation experiments confirm that this fractal nanobiointerface displays excellent cyto-compatibility with an over 96% cell viability after capture. These results provide new insights and may open up opportunities in designing and engineering new cell-material interfaces for advanced biomedical applications.

Stimuli-responsive smart gating membranes

This review highlights recent developments in stimuli-responsive smart gating membranes, including design and fabrication strategies, versatile stimuli-responsive gating models and advanced applications.

Capturing red blood cells from the blood by lectin recognition on a glycopolymer-patterned surface

A glycopolymer-patterned surface selectively captures red blood cells from the blood by lectin recognition in a harmless manner.

Preservation of osteoblasts and BM-MSCs biological properties after consecutive passages with the thermal-liftoff method

Thermo-responsive surfaces based on PNIPAAm provide a novel way to harvest cells with temperature reduction.

Endogenous signalling control of cell adhesion by using aptamer functionalized biocompatible hydrogel

Design of biological signal-responsive biomaterials is essential for controlling cell-cell and cell-matrix interactions. Herein, we developed a dynamic hydrogel to control cell adhesion with biological signals in a cellular microenvironment. The basic principle was based on using nucleic acid aptamer to recognize cell signalling and control the display of bioligands on the hydrogel. Not only exogenous signalling but also endogenous signalling secreted by surrounding cells could activate the dynamic scaffold and tune the cell adhesion state. Since diverse aptamers have been developed, our design can be extended to multiple biological inputs. The biochemical signal-responsive system will greatly enhance the understanding of complex biological processes as well as the ability to manipulate cellular behaviors.

Capture and Release of Cancer Cells by Combining On-Chip Purification and Off-Chip Enzymatic Treatment

As "liquid biopsies", circulating tumor cells (CTCs) have been thought to hold significant insights for cancer diagnosis and treatment. Despite the advances of microfluidic techniques that improve the capture of CTCs to a certain extent, recovering the captured CTCs with enhanced purity at the same time remains a challenge. Here, by combining on-chip purification and off-chip enzymatic treatment, we demonstrate a two-stage strategy to enhance the purity of captured cancer cells from blood samples. The on-chip purification introduces a stirring flow to increase the capture sensitivity and decrease nonspecifically bounded cells. The off-chip enzymatic treatment enables the cancer cells to be released from the attached magnetic beads, further improving the purity and enabling next reculture. For the proof-of-concept study, spiked cancer cells are successfully obtained from unprocessed whole blood with high recovery rate (∼68%) and purity (∼61%), facilitating subsequent RNA expression analysis.

Rational Design of Materials Interface for Efficient Capture of Circulating Tumor Cells

Originating from primary tumors and penetrating into blood circulation, circulating tumor cells (CTCs) play a vital role in understanding the biology of metastasis and have great potential for early cancer diagnosis, prognosis and personalized therapy. By exploiting the specific biophysical and biochemical properties of CTCs, various material interfaces have been developed for the capture and detection of CTCs from blood. However, due to the extremely low number of CTCs in peripheral blood, there exists a need to improve the efficiency and specificity of the CTC capture and detection. In this regard, a critical review of the numerous reports of advanced platforms for highly efficient and selective capture of CTCs, which have been spurred by recent advances in nanotechnology and microfabrication, is essential. This review gives an overview of unique biophysical and biochemical properties of CTCs, followed by a summary of the key material interfaces recently developed for improved CTC capture and detection, with focus on the use of microfluidics, nanostructured substrates, and miniaturized nuclear magnetic resonance-based systems. Challenges and future perspectives in the design of material interfaces for capture and detection of CTCs in clinical applications are also discussed.

Tuning of collagen scaffold properties modulates embedded endothelial cell regulatory phenotype in repair of vascular injuries in vivo

Perivascularly implanted matrix embedded endothelial cells (MEECs) are potent regulators of inflammation and intimal hyperplasia following vascular injuries. Endothelial cells (ECs) in collagen scaffolds adopt a reparative phenotype with significant therapeutic potential. Although the biology of MEECs is increasingly understood, tuning of scaffold properties to control cell-substrate interactions is less well-studied. It is hypothesized that modulating scaffold degradation would change EC phenotype. Scaffolds with differential degradation are prepared by cross-linking and predegradation. Vascular injury increases degradation and the presence of MEECs retards injury-mediated degradation. MEECs respond to differential scaffold properties with altered viability in vivo, suppressed smooth muscle cell (SMC) proliferation in vitro, and altered interleukin-6 and matrix metalloproteinase-9 expression. When implanted perivascularly to a murine carotid wire injury, tuned scaffolds change MEEC effects on vascular repair and inflammation. Live animal imaging enables real-time tracking of cell viability, inflammation, and scaffold degradation, affording an unprecedented understanding of interactions between cells, substrate, and tissue. MEEC-treated injuries improve endothelialization and reduce SMC hyperplasia over 14 d. These data demonstrate the potent role material design plays in tuning MEEC efficacy in vivo, with implications for the design of clinical therapies.

Capturing Cancer: Emerging Microfluidic Technologies for the Capture and Characterization of Circulating Tumor Cells

Circulating tumor cells (CTCs) escape from primary or metastatic lesions and enter into circulation, carrying significant information of cancer progression and metastasis. Capture of CTCs from the bloodstream and the characterization of these cells hold great significance for the detection, characterization, and monitoring of cancer. Despite the urgent need from clinics, it remains a major challenge to capture and retain these rare cells from human blood with high specificity and yield. Recent exciting advances in micro/nanotechnology, microfluidics, and materials science have enable versatile, robust, and efficient cell isolation and processing through the development of new micro/nanoengineered devices and biomaterials. This review provides a summary of recent progress along this direction, with a focus on emerging methods for CTC capture and processing, and their application in cancer research. Furthermore, classical as well as emerging cellular characterization methods are reviewed to reveal the role of CTCs in cancer progression and metastasis, and hypotheses are proposed in regard to the potential emerging research directions most desired in CTC-related cancer research.

Accelerating the Translation of Nanomaterials in Biomedicine

Due to their size and tailorable physicochemical properties, nanomaterials are an emerging class of structures utilized in biomedical applications. There are now many prominent examples of nanomaterials being used to improve human health, in areas ranging from imaging and diagnostics to therapeutics and regenerative medicine. An overview of these examples reveals several common areas of synergy and future challenges. This Nano Focus discusses the current status and future potential of promising nanomaterials and their translation from the laboratory to the clinic, by highlighting a handful of successful examples.

Underwater Thermoresponsive Surface with Switchable Oil-Wettability between Superoleophobicity and Superoleophilicity

An underwater thermoresponsive surface that can switch between superoleophobicity and superoleophilicity is fabricated with a combination of mixed brushes, containing thermoresponsive poly(N-isopropylacrylamide) and underwater oleophilic heptadecafluorodecyltrimethoxysilane, and nanostructured silicon nanowire arrays. Temperature-induced underwater adhesion switching between low-adhesive superoleophobicity and high-adhesive superoleophobicity is achieved on a pure poly(N-isopropylacrylamide)-modified nanostructured silicon nanowire array.