Continuous monitoring of wound-bed oxygenation provides important insight into healing progression and therapeutic response. Optical sensing offers a highly attractive route and remains challenging due to impaired light transport, limited signal collection, and unstable device-tissue coupling in wound environments. Here, we present a wireless hydrogel microneedle-enabled photonic sensing platform (MN-PS patch) for continuous, in situ monitoring of wound oxygen dynamics. Oxygen-responsive polymer-dot (Pdot) nanoprobes are embedded within a transparent hydrogel microneedle array, where a semiconducting polymer donor transfers energy to an oxygen-sensitive metalloporphyrin acceptor, enabling ratiometric luminescence-based oxygen readout. The microneedle architecture establishes a minimally invasive and conformal interface while creating transparent optical channels that enhance excitation delivery and emission collection. The MN-PS patch exhibits a linear ratiometric response to physiologically relevant oxygen concentrations (10-100 μM) and enables wireless optical readout using smartphone imaging. In a murine wound model, the platform continuously resolved hypoxia-reoxygenation dynamics during healing and quantitatively captured therapeutic responses to a ROS-scavenging and oxygen-generating SOD/CAT treatment. These results demonstrate that wound-bed oxygen dynamics can serve as a functional biomarker of healing progression. The MN-PS platform provides a minimally invasive strategy for real-time microenvironment monitoring and offers a general approach for photonic biosensing in dynamic soft-tissue environments.

Continuous glucose monitoring (CGM) is essential for diabetes management. Optical CGM provides a promising approach, yet current existing optical platforms face challenges including phototoxic excitation, shallow tissue penetration, and limited hardware compatibility. Here, we report a visible-light activated implantable nanophotonic biosensor that enables long-term in vivo glucose tracking through dual spectral and biochemical engineering. The sensor leverages Q-band of metalloporphyrins, shifting excitation from the phototoxic near-UV/blue B-band to the safer visible-light region, and couples with a rhodamine via Förster resonance energy transfer (FRET) to achieve efficient photon harvesting, ratiometric calibration, and CMOS-compatible optical readout. To stabilize enzymatic performance and mitigate oxidative damage, a glucose oxidase/catalase (GOx/CAT) cascade rapidly decomposes hydrogen peroxide (H2O2) byproducts, preserving sensitivity during extended implantation. This integrated design yields a biocompatible, optically compatible, and long-term stable nanophotonic sensing platform, advancing the development of smart terminal-integrated CGM systems with robust in vivo performance and strong translational potential for personalized diabetes management.

Selenium nanoparticles (SeNPs) have attracted considerable attention in the field of cancer therapy due to their remarkable biological activities and advantageous nanoscale properties. However, their inherent instability presents a considerable challenge for broader applications. To address this issue, the heteropolysaccharide extracted from golden berries (the fruits of Physalis peruviana), designated as DLG, was utilized to synthesize heteropolysaccharide-conjugated selenium nanoparticles, named DLG-SeNP3. Subsequent characterization showed that the nanoparticles DLG-SeNP3 were spherical, with an average particle size of 77 nm, a zeta potential of -14.4 mV, and excellent stability under physiological pH conditions. Further biological investigations showed that DLG-SeNP3 effectively inhibited tumor cell proliferation, exhibiting an IC50 value of 41.60 μg/mL against A549 cells, and induced apoptosis, with a proportion of 31.30 % at 100 μg/mL. Moreover, in vivo experiments demonstrated that DLG-SeNP3 not only inhibited angiogenesis, resulting in a 26.51 % decrease at 2 μg/mL, but also suppressed tumor growth and invasion, with reductions of 76.90 % and 66.67 % in the intensity and foci of red fluorescence, respectively, at 2 μg/mL. In conclusion, DLG-SeNP3, stabilized with polysaccharides derived from golden berries, shows promising potential for application in cancer treatment.

Non-invasive brain–computer interfaces (NI-BCIs) have garnered significant attention due to their safety and wide range of applications. However, developing non-invasive electroencephalogram (EEG) electrodes that are highly sensitive, comfortable to wear, and reusable has been challenging due to the limitations of conventional electrodes. Here, we introduce a simple method for fabricating semi-dry hydrogel EEG electrodes with antibacterial properties, enabling long-term, repeatable acquisition of EEG. By utilizing N-acryloyl glycinamide and hydroxypropyltrimethyl ammonium chloride chitosan, we have prepared electrodes that not only possess good mechanical properties (compression modulus 65 kPa) and anti-fatigue properties but also exhibit superior antibacterial properties. These electrodes effectively inhibit the growth of both Gram-negative (E. coli) and Gram-positive (S. epidermidis) bacteria. Furthermore, the hydrogel maintains stable water retention properties, resulting in an average contact impedance of <400 Ω measured over 12 h, and an ionic conductivity of 0.39 mS cm−1. Cytotoxicity and skin irritation tests have confirmed the high biocompatibility of the hydrogel electrodes. In an N170 event-related potential (ERP) test on human volunteers, we successfully captured the expected ERP signal waveform and a high signal-to-noise ratio (20.02 dB), comparable to that of conventional wet electrodes. Moreover, contact impedance on the scalps remained below 100 kΩ for 12 h, while wet electrodes became unable to detect signals after 7–8 h due to dehydration. In summary, our hydrogel electrodes are capable of detecting ERPs over extended periods in an easy-to-use manner with antibacterial properties. This reduces the risk of bacterial infection associated with prolonged reuse and expands the potential of NI-BCIs in daily life.

Non-invasive brain-computer interfaces (NI-BCIs) have garnered significant attention due to their safety and wide range of applications. However, developing non-invasive electroencephalogram (EEG) electrodes that are highly sensitive, comfortable to wear, and reusable has been challenging due to the limitations of conventional electrodes. Here, we introduce a simple method for fabricating semi-dry hydrogel EEG sensors with antibacterial properties, enabling long-term, repeatable acquisition of EEG. By utilizing N-acryloyl glycinamide and hydroxypropyltrimethyl ammonium chloride chitosan, we have prepared electrodes that not only possess good mechanical properties (compression modulus 65 kPa) and anti-fatigue properties but also exhibit superior antibacterial properties. These electrodes effectively inhibit the growth of both Gram-negative (E. coli) and Gram-positive (S. epidermidis) bacteria. Furthermore, the hydrogel maintains stable water retention properties, resulting in an average contact impedance of less than 400 Ω measured over 12 hours, and an ionic conductivity of 0.39 mS/cm. Cytotoxicity and skin irritation tests have confirmed the high biocompatibility of the hydrogel electrodes. In N170 event-related potential (ERP) tests conducted on human volunteers, we successfully captured the expected ERP signal waveform, comparable to that of traditional wet electrodes. Moreover, contact impedance on the scalps remained below 100 kΩ for 12 hours, while wet electrodes became unable to detect signals after 7–8 hours due to dehydration. In summary, our hydrogel electrodes are capable of detecting ERPs over extended periods in an easy-to-use manner with antibacterial properties. This reduces the risk of bacterial infections associated with prolonged reuse and expands the potential of NI-BCIs in daily life.

The emergence of the global pandemic and the discoveryof nucleicacid biomarkers in cancer diagnosis have fostered the developmentof more accurate and adaptive molecular diagnosis technologies. Currentnucleic acid testing (NAT) methods either lack sensitivity or requiretedious amplification operations, which could not meet the need forpoint-of-care (POC) NAT for on-site and community-based diagnosis.Here, we present a fluorescence one-step-bDNA-based lateral flow assay(FOB-LFA) method for amplification-free NAT to realize point-of-carepathogen detection and disease diagnosis. Take COVID-19 as an example,the developed FOB-LFA demonstrated a high sensitivity of 300 copies/mLfor the RNA of the SARS-CoV-2 pseudovirus and exhibited high specificityamong various homologous pseudoviruses. Further, the result of oropharyngealswab sample detection suggested the great potential of FOB-LFA inclinical examination. The outstanding performance of FOB-LFA, includinghigh sensitivity, high specificity, low cost, excellent portability,and minimized risk of nucleic acid leakage and contamination, canmeet the POC testing demand for the diagnosis of various infectiousand genetic diseases.

Ethnopharmacological relevance: Plant-based extracts to interfere with the onset of diabetes may be a promising approach towards type 2 diabetes mellitus (T2DM). Bitter gourd (Momordica charantia L.) is popularly consumed as an edible and medicinal resource with hypoglycemic effect in China. Wild bitter gourd (Momordica Charantia var. abbreviata Ser.) is a variant of bitter gourd, but there are relatively few studies on it.Aim of the study: The purpose of the experiment is to first screen out the most effective extraction part of Momordica charantia L. and Momordica Charantia var. abbreviata Ser. through the hypoglycemic activity experiment in vitro, and by using a high-fat and high-sugar diet with STZ-induced diabetic rat model in vivo to explore the possible mechanism of action against diabetes.Materials and methods: This study first performed alpha-glucosidase, PTP1B and lipase activities inhibition experiments on the alcohol and water extracts of Momordica charantia L. and Momordica Charantia var. abbreviata Ser. Sprague Dawley rats were either given normal feed or a high sugar and fat diet for four weeks, followed STZ (25 mg/kg, via i. p.) was given. Rats with fasting blood glucose >= 11.1 mmol/l after one week were deemed to be diabetic, treatments were administered for four weeks, and then blood samples were used to evaluate hematological and biochemical indicators, and liver was removed for post-analysis. The expression levels of p-AMPK, AMPK, p-PI3K, PI3K, p-AKT, AKT, p-GSK3 beta, GSK3 beta, p-IRS-1, IRS-1, GLUT2 were determined by Western blot. At the same time, the chemical components was identified by liquid-mass spectrometry.Results: Data showed that the ethanol extract of wild bitter gourd (WBGE) had the best ability to regulate glucose and lipid metabolism in vitro. Therefore, we further investigated the antidiabetic effects of oral consumption of WBGE on high-fat diet (HFD) and streptozotocin (STZ)-induced T2DM in SD rats. WBGE effectively reduced blood glucose and lipid levels, alleviated glucose intolerance and insulin resistant. Moreover, WBGE consumption could also inhibited oxidant responses and inflammatory damage. Mechanism studies have shown that WBGE may act by regulating AMPK/PI3K signaling pathway. On the other hand, the content of total phenol, total flavonoids, total saponins and total polysaccharide were measured by UV, 27 compounds were identified by LCMS.Conclusions: These studies explored the role and mechanism of WBGE in regulating glucose and lipid metabolism, and may support the utilization and further investigation of wild bitter gourd as a dietary intervention strategy to prevent diabetes and related metabolic abnormalities.

Aberrant cerebral glucose metabolism is related to many brain diseases, especially brain tumor. However, it remains challenging to measure the dynamic changes in cerebral glucose. Here, we developed a near-infrared (NIR) optical transducer to sensitively monitor the glucose variations in cerebrospinal fluid in vivo. The transducer consists of an oxygen-sensitive nanoparticle combined with glucose oxidase (GOx), yielding highly sensitive NIR phosphorescence in response to blood glucose change. We demonstrated long-term continuous glucose monitoring by using the NIR transducer. After subcutaneous implantation, the glucose transducer provides a strong luminescence signal that can continuously monitor blood glucose fluctuations for weeks. By using the NIR emission of the transducer, we further observed abnormal dynamic changes in cerebrospinal fluid glucose and quantitatively assessed cerebral glucose uptake rates in transgenic mice bearing brain tumors. This study provides a promising method for the diagnosis of various metabolic diseases with altered glucose metabolism.

It is well-recognized that the matrix stiffness as an important stem cell niche can mediate stem cell behavior such as attachment, proliferation and differentiation, but how matrix stiffness affects the im-munomodulatory efficacy of stem cells has been little explored, which, however, is of significant impor-tance in determining the outcomes of stem cell-based therapies and engineered tissue mimics. We herein studied the immunomodulatory efficacy of mesenchymal stem cells (MSCs) in response to matrix stiffness by the evaluation of macrophage polarization in vitro and inflammatory response in vivo by subcutaneous implantation of MSC-laden hydrogels. Remarkably, we found that soft matrix enabled MSCs to produce significantly higher levels of immunomodulatory factors compared to stiff matrix, and induced the pres-ence of more anti-inflammatory macrophages in vitro and attenuated macrophages-mediated inflamma-tory response in vivo. More importantly, we revealed stiffness-mediated immunoregulatory effect of MSCs was mainly attributed to tumor necrosis factor-alpha-stimulated protein 6 (TSG-6), which was mechanosen-sitively regulated by the MAPK and Hippo signaling pathway and downstream AP1 complex, and which in turn exerted an effect on macrophages through CD44 receptor to inhibit NF -KB pathway. To conclude, our results for the first time identify TSG-6 as the key factor in regulating immunomodulatory efficacy of MSCs in mechanical response, and can be potentially utilized to empower stem cell-based therapy and tissue engineering strategy in regenerative medicine.Statement of Significance Matrix stiffness as an important stem cell niche can mediate stem cell behavior such as attachment and differentiation, but how matrix stiffness affects the immunomodulatory efficacy of stem cells has been lit-tle explored, which, however, is of significant importance in determining the outcomes of stem cell-based therapies and engineered tissue mimics. Our results for the first time identify TSG-6 as the key factor in regulating the immunomodulatory efficacy of MSCs in mechanical response, which was regulated by the MAPK and Hippo signaling pathways and downstream AP1 complex, and which in turn exerted an ef-fect on macrophages through CD44 receptor to inhibit NF -KB pathway, and can be potentially utilized to empower stem cell-based therapy and tissue engineering strategy in regenerative medicine.(c) 2022 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Optical sensors have attracted a great deal of interest for glucose detection. However, their practical applications for continuous glucose monitoring are still constrained by operational reliability in subcutaneous tissues. Here, we show an implantable hydrogel platform embedded with luminescent polymer dots (Pdots) for sensitive and long-term glucose monitoring. We use Pdot transducer in a polyacrylamide hydrogel matrix to construct an implantable platform. The hydrogel-Pdot transducer showed bright luminescence with ratiometric response to glucose changes. The in vitro and in vivo sensitivities of the hydrogel implant were enhanced by varying the enzyme concentration and injection volume. After implantation, the hydrogel with Pdot transducer remained at the implanted site without migration for 1 month and can be removed from the subcutaneous tissue for further analysis. Our results indicate that the hydrogel-Pdot platform maintains the intrinsic sensing property with excellent stability during 1 month implantation, while fibrous capsule formation on the implant in some cases needs to be solved for long-term continuous glucose monitoring.

Current techniques for the generation of cell-laden microgels are limited by numerous challenges, including poorly uncontrolled batch-to-batch variations, processes that are both labor- and time-consuming, the high expense of devices and reagents, and low production rates; this hampers the translation of laboratory findings to clinical applications. To address these challenges, we develop a droplet-based microfluidic strategy based on metastable droplet-templating and microchannel integration for the substantial large-scale production of single cell-laden alginate microgels. Specifically, we present a continuous processing method for microgel generation by introducing amphiphilic perfluoronated alcohols to obtain metastable emulsion droplets as sacrificial templates. In addition, to adapt to the metastable emulsion system, integrated microfluidic chips containing 80 drop-maker units are designed and optimized based on the computational fluid dynamics simulation. This strategy allows single cell encapsulation in microgels at a maximum production rate of 10 ml h(-1) of cell suspension while retaining cell viability and functionality. These results represent a significant advance toward using cell-laden microgels for clinical-relevant applications, including cell therapy, tissue regeneration and 3D bioprinting.

Luminescent dye-doped polymer dots (Pdots) have been demonstrated for various biosensing applications. However, the dye doping strategy may suffer from dye aggregation and dye leaching issues which limit the long-term sensor performance. Here, we show that covalent incorporation of metalloporphyrin in polyfluorene backbone for continuous glucose monitoring. The resulting polymer was used to develop luminescent Pdots transducer that overcome the dye-aggregation problem. We characterized the spectroscopic properties of the metalloporphyrin covalently-linked Pdots, which showed reduced batch-to-batch variation, enhanced intra-particle energy transfer, and improved luminescence stability as compared to the metalloporphyrin-doped Pdots. After bioconjugation with glucose oxidase (GOx), the oxygen-sensitive phosphorescence is highly sensitive to glucose variations. The metalloporphyrin-linked Pdots transducer showed good performance in long-term continuous glucose monitoring in mouse models. This work demonstrates that covalent incorporation of porphyrin dyes in Pdots transducer is a reliable strategy to improve their stability and reproducibility for long-term continuous glucose monitoring in vivo.

Unlike conventional monolithic hydrogels with covalent cross-linkage that are typically elastic, colloidal gels assembled by reversibly assembled particles as building blocks have shown fascinating viscoelastic properties. They follow a gel-sol transition upon yielding and recover to the initial state upon the release of the shear force (so-called shear-thinning and self-healing behavior); this makes them an ideal candidate as injectable and moldable biomaterials for tissue regeneration. The immune response provoked by the implantation of the colloidal gels with special viscoelastic and structural features is critical for the successful integration of the implants with the host tissues, which, however, remains little explored. Since macrophages are known as the primary immune cells in determining the inflammatory response against the implants, we herein investigated in vitro macrophage polarization and in vivo inflammatory response induced by gelatin-based colloidal gels as compared to monolithic gels. Specifically, self-healing colloidal gels composed of pure gelatin nanoparticles, or methacrylate gelatin (GelMA) nanoparticles to allow secondary covalent cross-linkage were compared with GelMA bulk hydrogels. We demonstrated that hydrogel's elasticity plays a more dominant role rather than the structural feature in determining in vitro macrophage polarization evidenced by the stiffer gels inducing pro-inflammation M2 macrophage phenotype as compared to soft gels. However, subcutaneous implantation revealed a significantly alleviated immune response characterized by less fibrous capsule formation for the colloidal gels as compared to bulk gels of similar matrix elasticity. We speculated this can be related to the improved permeability of the colloidal gels for cell penetration, thereby leading to less fibrosis. In general, this study provided in-depth insight into the biophysical regulator of hydrogel materials on macrophage behavior and related inflammatory response, which can further direct future implant design and predict biomaterial-host interactions for immunotherapy and regenerative medicine. Impact statement Macrophages response to implanted biomaterials is a highly regulated process that influences device functionality and clinical outcome. Nowadays, the viscoelastic properties of colloidal versus monolithic hydrogels on macrophage phenotype in vitro and the host inflammatory response are not known. Our study found that colloidal hydrogels composed of nanoparticles of gelatin and methacrylate gelatin (GelMA) led to more anti-inflammatory polarization especially on soft colloidal gel (5.9 KPa) compared to bulk GelMA hydrogels. It suggested that macrophage response can be mechanically regulated by the viscoelastic signals of the hydrogels, which could be a promising strategy for the future design and application of novel biomaterials.

A hydrogel that combines both printability and adaptability, high elasticity, and stretchability can provide ideal mechanical properties, and also render complex and accurate construction for ionic skin. However, it is extremely challenging. Here, we propose a colloidal-based double-network (DN) hydrogel as printable inks for high-precision fabrication of ionic skins. Particularly, polyacrylamide (PAAm), as the covalent network that can maintain the long-term material integrity, was combined with gelatin colloidal network to improve the injectability and printability of the resulting DN hydrogels. The DN design cooperatively provides the hydrogels with higher toughness values and deformability than what single colloidal or PAAm network can achieve. Further design of ionic skin based on capacitor microarray was demonstrated to serve as a sensitive and stable capacitor that can respond to external stimuli, thereby allowing to sense the body movements such as finger bending, laugh, and wrist pulse by translating mechanical changes into electric signals. Therefore, this study provides a novel strategy for the design and preparation of high-resolution ionic skins as the wearable sensor.

Isolation and analysis of circulating rare cells is a promising approach for early detection of cancer and other diseases and for prenatal diagnosis. Isolation of rare cells is usually difficult due to their heterogeneity as well as their low abundance in peripheral blood. We previously reported a two-stage ensemble-decision aliquot ranking platform (S-eDAR) for isolating circulating tumor cells from whole blood with high throughput, high recovery rate (>90%), and good purity (>70%), allowing detection of low surface antigen-expressing cancer cells linked to metastasis. However, due to the scarcity of these cells, large sample volumes and large quantities of antibodies were required to isolate sufficient cells for downstream analysis. Here, we drastically increased the number of nucleated cells analyzed by first concentrating peripheral blood mononuclear cells (PBMCs) from whole blood by density gradient centrifugation. The S-eDAR platform was capable of isolating rare cells from concentrated PBMCs (108/mL, equivalent to processing ∼20 mL of whole blood in the 1 mL sample volume used by our instrument) at a high recovery rate (>85%). We then applied the S-eDAR platform for isolating rare fetal nucleated red blood cells (fNRBCs) from concentrated PBMCs spiked with umbilical cord blood cells and confirmed fNRBC recovery by immunostaining and fluorescence in situ hybridization, demonstrating the potential of the S-eDAR system for isolating rare fetal cells from maternal PBMCs to improve noninvasive prenatal diagnosis.

Continuous glucose monitoring (CGM) allows type I and II diabetes patients to track changes in their glucose levels, allowing detection of impending hypoglycemia or hyperglycemia. Polymer dots (Pdots) are candidates for use in implanted CGM systems due to their exceptional brightness, photostability, sensitivity, and biocompatibility. However, Pdot glucose transducers are oxygen-dependent, and changes in tissue oxygen levels affect their measurement accuracy. Here, we describe an external ratiometric calibration method that corrects for changes in tissue oxygen levels to improve measurement accuracy. This method uses the ratio of oxygen concentrations inside and outside the Pdot glucose transducer as an indicator of glucose concentration to correct for signal deviations caused by tissue oxygen fluctuations. A second oxygen-sensitive Pdot that is not conjugated with glucose oxidase is used to measure the oxygen concentration outside the Pdot glucose transducer. We describe the theoretical basis for this approach and demonstrate its effectiveness experimentally in a subcutaneous mouse implant model. This external ratiometric system achieves higher accuracy glucose measurements than previous Pdot-based CGM systems and comparable accuracy to current commercial CGM systems, demonstrating the utility of the external ratiometric calibration strategy.

Background In recent years, ginseng products are widely used in various fields. More and more people pay attention to the extraction methods and quality evaluation of ginseng. At present, China, the United States, Europe, Japan and Korea have the quality standards and content determination methods of ginseng. However, due to the different treatment methods adopted before the determination of ginseng samples, the content limits of the index components, such as ginsenoside Rb 1 , Rg 1 and Re are also different. There have been research analyzed the similarities and differences of ginseng content detection methods in pharmacopoeias of different countries, but the comparison of the effects of different methods on ginsenoside content and structural transformation has not been reported. Methods In this paper, ginsenosides in ginseng were extracted according to four national Pharmacopoeia, and analyzed quantitatively and qualitatively by UPLC-Q-Exactive-MS and HPLC-UV. Finally, a simple and feasible extraction method was optimized by response surface method. Results Twelve kinds of ginsenosides in ginseng were quantitatively analyzed by using the methods of four national pharmacopoeia. Among them, the contents of Rg 1 , Re and Rd were high, and they were the highest by using unheated J/KP (Japan/Korea Pharmacopoeia) method. Ten kinds of ginsenosides were determined by heated CP (China Pharmacopoeia), USP (the United States Pharmacopoeia) and EP (European Pharmacopoeia) method, and seven kinds of ginsenosides were determined by unheated J/KP method. In the following UPLC-Q-Exactive-MS study, 34, 36, 21 and 19 ginsenosides were identified by CP, USP, EP and J/KP method, respectively. In the optimization of ginsenoside extraction process, an efficient extraction method was selected from the solvent, extraction time, solid-liquid ratio and other factors. In conclusion, through the qualitative and quantitative comparison of CP, USP and EP samples after heating, it can be seen that ginsenoside heating will increase the content of rare saponins, and the heating time is directly proportional to the content of rare saponins. Conclusion The pretreatment method has a significant effect on the content determination of ginseng. The analysis of the preparation method and process optimization of the four Pharmacopoeia can provide important reference for the revision of ginseng standard.

Droplet microfluidics has recently emerged as a powerful platform for a variety of biomedical applications including microreactors, bioactive compound encapsulation, and single cell culture and analysis; all these applications require long-term droplet stability, which, however, makes breaking the emulsion and retrieving the loaded samples difficult. Herein, we developed a novel class of thermo-responsive fluorosurfactants to control the droplet status simply by temperature. The surfactants were synthesized by coupling perfluorinated polyethers (PFPEs) with a thermo-responsive block of poly(N-isopropylacrylamide) (pNIPAM) or poly(2-ethyl-2-oxazoline) (pEtOx) with lower critical solution temperature (LCST). These diblock surfactants can stabilize the emulsion at temperatures below LCST due to the hydrophilic head, which became hydrophobic upon increasing the ambient temperature above LCST, thereby destabilizing the droplets and realizing demulsification simply via temperature control. The diblock surfactant can be applied for templating cell encapsulation using alginate microgels, which allowed one-step and high-throughput microfluidic generation of cell-laden microgels without compromising cell viability. This non-invasive, on-demand demulsification strategy provides a high degree of freedom for microencapsulation and on-demand recovery of the samples or reaction products within the droplets, which opens a new avenue for a wide range of applications of droplet-templating microfluidics.

Cell microenvironment is a collection of dynamic biochemical and biophysical cues which functions as the key factor in determining cell behavior. Encapsulating single cell into micrometer-scale hydrogels which mimics the cell microenvironment can be used for single cell analysis, cell therapies, and tissue engineering. Here, we developed a microfluidics-based platform to engineer the niche environment at single cell level using alginate microgels crosslinked by different metal ions to regulate stem cell behavior for bone regeneration. Specifically, we revealed that Ca2+ in the engineered microenvironment promoted osteogenic differentiation of encapsulated stem cells and substantially accelerated the matrix mineralization compared to Sr2+in vitro. However, the superior osteoinductive capacity of Ca2+ compared with Sr2+ led to comparable bone healing in a rat bone defect model. This attributed to Sr2+ in microgels to inhibit the osteoclast activity and bone resorption after implantation. In summary, the present study demonstrates metal ions as a critical factor in the environmental cues to affect cell behavior and influence the efficacy of stem cell-based therapy in tissue regeneration, and provides new insights to engineer an expecting microenvironment for regenerative medicine.