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Circulating tumor cells (CTCs) have now emerged as a type of promising circulating biomarkers in liquid biopsy and can predict the occurrence and development of cancers. In this work, an integrated and renewable interface is fabricated for the capture, release and quantitative analysis of CTCs. As designed, folate receptor-positive CTCs are captured by folic acid-modified DNA probes at the interface through the receptor-ligand interaction, and are efficiently released from the interface with the aid of bleomycin-ferrous complex-regulated cleavage. Taking MCF-7 cells as the model, the functional interface demonstrates high efficiency to selectively capture the folate receptor-positive tumor cells, and the bleomycin-ferrous complex-regulated cleavage not only easily releases the captured cells with well-maintained viability and proliferation ability, but also releases silver nanoparticles that are labeled at the cell surface for highly sensitive quantification by adopting electrochemical techniques with a detection limit of 6 cells/mL. At the meanwhile, the interface is proved to be regenerated through a simple cleavage-hybridization event and reused with high stability. Therefore, our work may provide a new idea for the collection and downstream researches of circulating tumor cells in the future.

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Selectively capturing and releasing viable circulating tumor cells (CTCs) from the peripheral blood of cancer patients is advantageous for investigating the molecular hallmarks of metastasis and developing personalized therapeutics. CTC-based liquid biopsies are flourishing in the clinical setting, offering opportunities to track the real-time responses of patients during clinical trials and lending accessibility to cancers that are traditionally difficult to diagnose. However, CTCs are rare compared to the breadth of cells that reside in the circulatory network, which has encouraged the engineering of novel microfluidic devices. Current microfluidic technologies either extensively enrich CTCs but compromise cellular viability or sort viable CTCs at low efficiencies. Herein we present a procedure to fabricate and operate a microfluidic device capable of capturing CTCs at high efficiencies while ensuring high viability. The microvortex-inducing microfluidic device functionalized with nanointerfaces positively enriches CTCs via cancer-specific immunoaffinity, while a thermally responsive surface chemistry releases the captured cells by raising the temperature to 37 °C.

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Stem cells play a crucial role in re-establishing homeostasis in the body, and the search for mechanisms by which they interact with the host to exert their therapeutic effects remains a key question currently being addressed. Considering their significant regenerative/therapeutic potential, research on mesenchymal stem cells (MSCs) has experienced an unprecedented advance in recent years, becoming the focus of extensive works worldwide to develop cell-based approaches for a variety of diseases. Initial evidence for the effectiveness of MSCs therapy comes from the restoration of dynamic microenvironmental homeostasis and endogenous stem cell function in recipient tissues by systemically delivered MSCs. The specific mechanisms by which the effects are exerted remain to be investigated in depth. Importantly, the profound cell-host interplay leaves persistent therapeutic benefits that remain detectable long after the disappearance of transplanted MSCs. In this review, we summarize recent advances on the role of MSCs in multiple disease models, provide insights into the mechanisms by which MSCs interact with endogenous stem cells to exert therapeutic effects, and refine the interconnections between MSCs and cells fused to damaged sites or differentiated into functional cells early in therapy.

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Cell sheet harvesting offers a great potential for the development of new therapies for regenerative medicine. For cells to adhere onto surfaces, proliferate, and to be released on demand, thermoresponsive polymeric coatings are generally considered to be required. Herein, an alternative approach for the cell sheet harvesting and rapid release on demand is reported, circumventing the use of thermoresponsive materials. This approach is based on the end-group biofunctionalization of non-thermoresponsive and antifouling poly(2-hydroxyethyl methacrylate) (p(HEMA)) brushes with cell-adhesive peptide motifs. While the nonfunctionalized p(HEMA) surfaces are cell-repellant, ligation of cell-signaling ligand enables extensive attachment and proliferation of NIH 3T3 fibroblasts until the formation of a confluent cell layer. Remarkably, the formed cell sheets can be released from the surfaces by gentle rinsing with cell-culture medium. The release of the cells is found to be facilitated by low surface density of cell-adhesive peptides, as confirmed by X-ray photoelectron spectroscopy. Additionally, the developed system affords possibility for repeated cell seeding, proliferation, and release on previously used substrates without any additional pretreatment steps. This new approach represents an alternative to thermally triggered cell-sheet harvesting platforms, offering possibility of capture and proliferation of various rare cell lines via appropriate selection of the cell-adhesive ligand.

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Serotonin (5-HT) is an essential inhibitory neurotransmitter in vivo that is critical for interneuronal communication of the nervous system. Herein, we constructed an electrochemical cell-sensing platform for 5-HT detection based on MXene/single-walled carbon nanotubes (SWCNTs) nanocomposite. The one-dimensional SWCNTs with good electrical conductivity are uniformly dispersed on the surface and intermediate layers of the two-dimensional MXene to form a tightly heterogeneous heterostructure. The synthesized MXene-SWCNTs could improve the stacking problem of MXene nanosheets and expose more active sites, effectively promoting the conductive properties and electrochemical activity of the composite. The fabricated MXene-SWCNTs/GCE possessed outstanding detection capability for 5-HT with a wide linear range of 4 nM-103.2 µM and a low detection limit of 1.5 nM. Moreover, the sensor was further applied for the real-time monitoring trace amount of 5-HT releasing from different cell lines, which confirmed its promising applications in 5-HT related physiological and pathological fields. MXene-SWCNTs/GCE was developed and applied for the real-time monitoring of trace amounts of 5-HT secreted from living cells.

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Encapsulation is a process in which a base material is encapsulated in a wall material that can protect it against external factors and/or improve its bioavailability. Among the different encapsulation techniques, ionic gelation stands out as being useful for thermolabile compounds. The aim of this work was to encapsulate Saccharomyces boulardii by ionic gelation using agavins (A) and whey protein (WP) as wall materials and to evaluate the morphostructural changes that occur during in vitro gastrointestinal digestion. Encapsulations at different levels of A and WP were analyzed using microscopic, spectroscopic and thermal techniques. Encapsulation efficiency and cell viability were evaluated. S. boulardii encapsulated at 5% A: 3.75% WP (AWB6) showed 88.5% cell survival after the simulated gastrointestinal digestion; the bead showed a significantly different microstructure from the controls. The mixture of A and WP increased in the survival of S. boulardii respect to those encapsulated with alginate, A or WP alone. The binary material mixture simultaneously allowed a controlled release of S. boulardii by mostly diffusive Fickian mechanisms and swelling. The cell-release time was found to control the increment of the Damköhler number when A and WP were substrates for S. boulardii, in this way allowing greater protection against gastrointestinal conditions.

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Circulating tumor cells (CTCs) have been well-established as promising biomarkers that can be leveraged to gauge the prognosis of patients with cancers and to guide patient treatment efforts. Although the scarcity of CTCs within peripheral circulation and the associated phenotypic changes that they exhibit owing to the epithelial-mesenchymal transition (EMT) process make the reliable isolation of these cells very challenging. Recently, several studies have discussed platforms capable of mediating the efficient and sensitive isolation of CTCs, but these approaches are nonetheless subject to certain limitations that preclude their clinical application. For example, these platforms are poorly-suited to minimizing damage in the context of cellular capture and release or the in vitro culture of captured cells for subsequent molecular analyses, which would better enable clinicians to select appropriate precision treatments on an individualized basis. In this study, we report the layer-by-layer assembly approach to synthesize a novel composite nanomaterial consisting of modified zirconium-based metal-organic-frameworks (MOFs) on the surface of magnetic beads with dual antibody surface modifications capable of capturing CTCs without being hampered by the state of cellular EMT process. Our analyses indicated that these dual antibody-modified nanomaterials exhibited greater capture efficiency than that observed for single antibody. Importantly, captured cells can be gradually released following capture and undergo subsequent in vitro proliferation following water molecule-induced MOF structural collapse. This release mechanism, which does not require operator intervention, may be effective as a means of minimizing damage and preserving cellular viability such that cells can be more reliably utilized for downstream molecular analyses and associated treatment planning. To further confirm the potential clinical applicability of the developed nanomaterial, it was successfully utilized for capturing CTCs from peripheral blood samples collected from cases diagnosed with gastrointestinal tumors.

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Probiotics confer numerous health benefits and functional foods prepared with these microbes own largest markets. However, their viability during transit from gastrointestinal tract is a concerning issue. Microencapsulation of probiotics is a novel technique of major interest to increase their survivability in GIT and food matrices by providing a physical barrier to protect them under harsh conditions. This article contributes the knowledge regarding microencapsulation by discussing probiotic foods, different methods and approaches of microencapsulation, coating materials, their release mechanisms at the target site, and interaction with probiotics, efficiency of encapsulated probiotics, their viability assessment methods, applications in food industry, and their future perspective. In our opinion, encapsulation has significantly got importance in the field of innovative probiotic enriched functional foods development to preserve their viability and long-term survival rate until product expiration date and their passage through gastro-intestinal tract. Previous review work has targeted some aspects of microencapsulation, this article highlights different methods of probiotics encapsulation and coating materials in relation with food matrices as well as challenges faced during applications: Gut microbiota; Lactic acid bacteria; Micro-encapsulation; Stability enhancement; Cell's release, Health benefits.

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Gold nanocluster (AuNC) decorated hydrogels have attracted considerable attention as versatile biomaterials. To date AuNCs and hydrogels have mainly been mixed as independent components. Here, we report the use of AuNCs as reactive monomers in the polymerization of hydrogels. We used a free radical polymerization to copolymerize AuNCs with acrylamide and N-acryloyl glycinamide to prepare stimuli-responsive smart hydrogels. Multiple C═C bonds were decorated on the surface of the AuNCs as active sites for polymerization. These C═C bonds not only protected the structure of the AuNCs from oxidation by free radicals during polymerization but also covalently connected the AuNCs with the polymer chains. This structure ensured good photothermal performance of the AuNCs while preserving the thermoresponsive hydrogen bonds of polymers. Moreover, the copolymerized AuNCs acted as cross-linkers, which improved the mechanical properties of the hydrogels. These smart hydrogels had good stability, efficient photothermal conversion, and a sensitive thermoresponsive. We examined their potential for capture of MDA-MB-231 cells with hyaluronic acid as target molecules. The captured cells were released under 660 nm irradiation. This process of targeted capture and light-controlled remote release could be repeatedly applied. These results suggest that systems based on AuNCs copolymerized with hydrogels have great potential for biomedical applications.

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Efficient cell capture and release methods are important for single-cell analysis of pathological samples. It requires not only strong cell binding but also mild cell release to maximize the number of collected cells while maintaining their viability. Here, we report a smart cell capture and release system based on self-assembling adhesive peptide nanofibers. We installed a versatile surface binding motif, 3, 4-dihydroxyphenylalanine to the C-terminus of a self-assembling peptide. We show that the designed peptide can self-assemble at physiological pH to establish strong cell and substrate binding. The binding strength is dramatically reduced upon the dissembling of the peptide fibers triggered by raising the pH to slightly basic. We demonstrate the efficient capture of four different cells using this system. The capture rates are comparable to fibrin glue and the released cells retain higher viability than those released by enzymatic digestion approaches. Given that this method is highly efficient, biocompatible, and easy to implement, we anticipate that this approach can be widely applied to cell capture and release for single cell analysis and cell therapy.

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Circulating tumor cells (CTCs), a type of cancer cell that spreads from primary tumors into human peripheral blood and are considered as a new biomarker of cancer liquid biopsy. It provides the direction for understanding the biology of cancer metastasis and progression. Isolation and analysis of CTCs offer the possibility for early cancer detection and dynamic prognosis monitoring. The extremely low quantity and high heterogeneity of CTCs are the major challenges for the application of CTCs in liquid biopsy. There have been significant research endeavors to develop efficient and reliable approaches to CTC isolation and analysis in the past few decades. With the advancement of microfabrication and nanomaterials, a variety of approaches have now emerged for CTC isolation and analysis on microfluidic platforms combined with nanotechnology. These new approaches show advantages in terms of cell capture efficiency, purity, detection sensitivity and specificity. This review focuses on recent progress in the field of nanotechnology-assisted microfluidics for CTC isolation and detection. Firstly, CTC isolation approaches using nanomaterial-based microfluidic devices are summarized and discussed. The different strategies for CTC release from the devices are specifically outlined. In addition, existing nanotechnology-assisted methods for CTC downstream analysis are summarized. Some perspectives are discussed on the challenges of current methods for CTC studies and promising research directions.

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Cell separation is important in cell therapy and disease diagnosis. Therefore, various cell separation methods have been studied, but cellular damage and the need for pretreatment remain substantial problems. Recently, in the diagnostic field, the detachment and recovery of antibody-captured cells was actively studied to obtain more detailed information on cancer cells. Previously, we have developed a highly efficient cell separation method using microfibers. In the present study, the efficiency of cell capture and release was examined by controlling the molecular mobility of an immobilized antibody to efficiently detect cells with low expression of a marker molecule. We found that improvement in molecular mobility of antibodies enhances cell capture efficiency but decreases the detachment effectiveness of the captured cells. Therefore, the molecular mobility of antibodies can be utilized to control cell capture and release according to the level of expression of the marker molecule.

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Cell manipulation has raised extensive concern owing to its underlying applications in numerous biological situations such as cell-matrix interaction, tissue engineering, and cell-based diagnosis. Generally, light is considered as a superior candidate for manipulating cells (e.g., cell release) due to their high spatiotemporal precision and non-invasion. However, it remains a big challenge to release cells with high efficiency due to their potential limitation of the light-triggered wettability transition on photoresponsive surfaces. In this study, we report a photoresponsive spiropyran-coated nanostructured surface that enables highly efficient release of cancer cells, amplified by the introduction of a photo-irresponsive molecule. On one hand, structural recognition stems from topological interaction between nanofractal surfaces and the protrusions of cancer cells. On the other, molecular recognition can be amplified by a photo-irresponsive and hydrophilic molecule by reducing the steric hindrance of photoresponsive components and resisting nonspecific cell adhesion. Therefore, this study may afford a novel avenue for developing advanced smart materials for high-quality biological analysis and clinical diagnosis.

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This paper reports a method for label-free single-cell biophysical analysis of multiple cells trapped in suspension by electrokinetic forces. Tri-dimensional pillar electrodes arranged along the width of a microfluidic chamber define actuators for single cell trapping and selective release by electrokinetic force. Moreover, a rotation can be induced on the cell in combination with a negative DEP force to retain the cell against the flow. The measurement of the rotation speed of the cell as a function of the electric field frequency define an electrorotation spectrum that allows to study the dielectric properties of the cell. The system presented here shows for the first time the simultaneous electrorotation analysis of multiple single cells in separate micro cages that can be selectively addressed to trap and/or release the cells. Chips with 39 micro-actuators of different interelectrode distance were fabricated to study cells with different sizes. The extracted dielectric properties of Henrietta Lacks, human embryonic kidney 293, and human immortalized T lymphocytes cells were found in agreements with previous findings. Moreover, the membrane capacitance of M17 neuroblastoma cells was investigated and found to fall in in the range of 7.49 ± 0.39 mF/m2 .

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Artificial stimuli-responsive hydrogels that can mimic natural extracellular matrix for growth and release of cancer spheroids (CSs) have attracted much attention. However, such hydrogels still face a challenge in regulating CSs growth and controlled release as well as keeping CSs integrity. Herein, a new class of ClO-/SCN- reversibly responsive nanocellulose hydrogel with fluorescence on-off reporter is developed. Upon addition of ClO-, the gel network of nanocellulose hydrogel was destructed, accompanying by the fluorescent quenching. Notably, when introducing of SCN-, a red fluorescence filamentous hydrogel was recovered by coordination cross-linking. The hydrogel reforms in a completely reversible process through the regulation of ClO-/SCN-. Benefit from the above response features of the hydrogel, the growth of cancer spheroids (CSs) in the hydrogel and on demand release of CSs from the hydrogel could be easily achieved through ClO-/SCN- regulation. Importantly, the growth and release of CSs can be monitored in real time by fluorescence imaging. Overall, such design strategy based on ClO-/SCN--responsive fluorescent hydrogels provided a new type of multi-responsive hydrogels as main scaffolds for cancer research and cancer drug screening.

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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.

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The root cap protects the root from environmental stress and senses gravity. Cells of the last layer of the root cap are shed in a developmentally programmed process. We previously showed that the transcription factor NIN-LIKE PROTEIN7 (NLP7) regulates root cap cell release likely through regulation of CELLULASE5 (CEL5). Here we provide a supplement to that work. We hypothesized that the nlp7 mutant has defects in additional root cap functions. We find that neither gravity sensing nor expression of a root cap cell identity marker is altered in nlp7 but that expression of another cellulase, CEL3, is upregulated. We conclude that NLP7 control of root cap cell release is largely independent of gravity sensing and root cap cell identity.

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Macroscopic hollow polymeric particles are attractive materials for various applications such as surgery, food industry, agriculture, etc. However, protocols reporting their synthesis have hitherto made use of organic solvents and/or sacrificial templates, compromising the encapsulation of different bioactive compounds and the process yield. Here, millimeter-size, hollow polymeric particles were synthesized, for the first time, in a solvent- and template free manner onto superhydrophobic surfaces (SHS). The particles were produced upon assembly and double superficial crosslinking of liquid droplets of DNA and methacrylamide chitosan aqueous solutions (CH:MA), leading to liquid-core particles with a hardened hydrogel shell. The particles displayed appealing physical and biological properties. The millimeter-size hydrogel shell, resulting from the double ionic/covalent crosslinking of CH:MA, endowed the hollow particles with softness to the touch and an outstanding structural stability against manipulation by hand and with forceps. Meanwhile, the liquid DNA core guaranteed a biocompatible cell encapsulation followed by a superior release and proliferation of viable cells, as compared to solid CH:MA particles prepared as a blank. Particles with these characteristics show promise for surgical protocols practiced in Tissue Engineering and Regenerative Medicine, where manipulable and biocompatible synthetic implants are often needed to supply living cells and other sensitive bioactive compounds.

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Macroscopic hollow polymeric particles are attractive materials for various applications such as surgery, food industry, agriculture, etc. However, protocols reporting their synthesis have hitherto made use of organic solvents and/or sacrificial templates, compromising the encapsulation of different bioactive compounds and the process yield. Here, millimeter-size, hollow polymeric particles were synthesized, for the first time, in a solvent- and template free manner onto superhydrophobic surfaces (SHS). The particles were produced upon assembly and double superficial crosslinking of liquid droplets of DNA and methacrylamide chitosan aqueous solutions (CH:MA), leading to liquid-core particles with a hardened hydrogel shell. The particles displayed appealing physical and biological properties. The millimeter-size hydrogel shell, resulting from the double ionic/covalent crosslinking of CH:MA, endowed the hollow particles with softness to the touch and an outstanding structural stability against manipulation by hand and with forceps. Meanwhile, the liquid DNA core guaranteed a biocompatible cell encapsulation followed by a superior release and proliferation of viable cells, as compared to solid CH:MA particles prepared as a blank. Particles with these characteristics show promise for surgical protocols practiced in Tissue Engineering and Regenerative Medicine, where manipulable and biocompatible synthetic implants are often needed to supply living cells and other sensitive bioactive compounds.

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We introduce an efficient method for the preparation of photolabile polymer linkers to be used in the fabrication of bioorthogonal and photodegradable hydrogels. The versatility of this synthesis strategy allows for incorporation of a series of chromophores responsive to addressable wavelengths of UV and broad spectrum visible light. Consequently, selective release of different cell types from composite hydrogels by user-defined timing can be achieved by irradiating the materials with different wavelengths of light.