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In the field of three‐dimensional (3D) cell culture and tissue engineering, great advance focusing on functionalized materials and desirable culture systems has been made to mimic the natural environment of cells in vivo. Mechanical loading is one of the critical factors that affect cell/tissue behaviors and metabolic activities, but the reported models or detection methods offer little direct and real‐time information about mechanically induced cell responses. Herein, for the first time, a stretchable and multifunctional platform integrating 3D cell culture, mechanical loading, and electrochemical sensing is developed by immobilization of biomimetic peptide linked gold nanotubes on porous and elastic polydimethylsiloxane. The 3D scaffold demonstrates very good compatibility, excellent stretchability, and stable electrochemical sensing performance. This allows mimicking the articular cartilage and investigating its mechanotransduction by 3D culture, mechanical stretching of chondrocytes, and synchronously real‐time monitoring of stretch‐induced signaling molecules. The results disclose a previously unclear mechanotransduction pathway in chondrocytes that mechanical loading can rapidly activate nitric oxide signaling within seconds. This indicates the promising potential of the stretchable 3D sensing in exploring the mechanotransduction in 3D cellular systems and engineered tissues. [ABSTRACT FROM AUTHOR]

The role of endogenous serotonin (5‐HT) in gastrointestinal motility is still highly controversial. Although electrochemical techniques allow for direct and real‐time recording of biomolecules, the dynamic monitoring of 5‐HT release from elastic and tubular intestine during motor reflexes remains a great challenge because of the specific peristalsis patterns and inevitable passivation of the sensing interface. A stretchable sensor with antifouling and decontamination properties was assembled from gold nanotubes, titanium dioxide nanoparticles, and carbon nanotubes. The sandwich‐like structure endowed the sensor with satisfying mechanical stability and electrochemical performance, high resistance against physical adsorption, and superior efficiency in the photodegradation of biofouling molecules. Insertion of the sensor into the lumen of rat ileum (the last section of the small intestine) successfully mimics intestinal peristalsis, and simultaneous real‐time monitoring of distension‐evoked 5‐HT release was possible for the first time. Our results unambiguously reveal that mechanical distension of the intestine induces endogenous 5‐HT overflow, and 5‐HT level is closely associated with the physiological or pathological states of the intestine. [ABSTRACT FROM AUTHOR]

[Display omitted] • We developed a 3D lactate electrochemical sensor by layer-by-layer assembly of carbon nanotubes, Prussian blue nanoparticles and lactate oxidase on a 3D scaffold electrode. • Further, the 3D sensor was integrated with collagen hydrogel with C6 glioma cells seeded therein and allowed the successful real-time monitoring of lactate released from C6 glioma cells, providing an effective detection platform for exploring the biochemical response in 3D cell culture systems. Three-dimensional (3D) cell culture has attracted increasing interest in many fields with the significant advantages in reproducing in vivo cell environment. For the characterization of biochemical information, electrochemical sensing has stood out from other techniques in real-time monitoring of living cells, and made an attempt to integrate with hydrogel for investigating the biological processes in 3D cell culture. However, it is still a challenge for real-time monitoring of cellular metabolites therein for the lack of electrochemical activity, and lactate (the product of aerobic glycolysis) is a typical example of such a predicament. Herein, we developed a 3D enzymatic electrochemical sensor that could be integrated with collagen hydrogel to monitor the lactate levels of cells cultured therein. Specifically, lactate oxidase immobilized on the outer surface of 3D sensor could oxidize lactate with H 2 O 2 as a product, and Prussian blue nanoparticles electrodeposited on carbon nanotubes adsorbed electrode conferred the excellent and stable electrocatalytic performance to H 2 O 2 for lactate detection. Further, the 3D sensor was integrated with collagen hydrogel with C6 glioma cells seeded therein and allowed the successful real-time monitoring of lactate released from C6 glioma cells, providing an effective detection platform for exploring the biochemical response in 3D cell culture systems. [ABSTRACT FROM AUTHOR]