This review covers the design rationale for application of hydrogels systems for use in bioelectronic devices with a focus on in vivo applications.Smart polymers that are capable of controlled shape transformations under external stimuli have attracted significant attention in the recent years due to the resemblance of this behavior to the biological intelligence observed in nature. Moreover, shape-morphing polymer-based materials are great candidates for biomedical applications due to their adaptive properties, controlled shape transformations, and enriched functionality. In this review, we focus on the recent progress in the field of shape-memory and shape-changing polymers, highlighting their most promising applications in the biomedical field. We include a brief theoretical background on the underlying molecular mechanisms, classification of the polymer systems based on their mechanical properties, and the most promising state-of-the-art processing techniques for the fabrication of intelligent polymer-based materials. The aim of this review is to provide a link between the diverse stimuli-responsive polymer systems and their mechanical properties, and to highlight the most appealing up-to-date biomedical applications for shape-morphing systems.Synthetic hydrogels are generally amorphous in nature without any order at the molecular level. This is in contrast to biological gels containing ordered aggregates contributing significantly to their mechanical performance. Semicrystalline hydrogels, first developed in 1994, are moderately water-swollen hydrogels containing crystalline domains. Recent work shows that physically cross-linked semicrystalline hydrogels belong to one of the groups of mechanically strong and highly stretchable hydrogels exhibiting melt-processability, self-healing and shape-memory functions. They can undergo an abrupt and reversible change from a solid-like to a liquid-like state at the melting temperature, opening up several applications such as shape-memory hydrogels, injectable gels, chemical motors, and smart inks for 3D or 4D printing. In this review article, recent advances in the field of semicrystalline physical hydrogels prepared from hydrophilic and hydrophobic vinyl monomers via a free-radical mechanism are summarized. Synthesis-molecular structure-property relations of semicrystalline hydrogels, current challenges and future directions are also discussed.Although some advanced treatments of heart failure (HF) have experienced great development in recent decades, morbidity and mortality associated with HF have not improved significantly. Hydrogels have some unique advantages for the delivery and controlled release of bioactive molecules, drugs, and cells, which can directly affect the heart locally. Many studies have shown that hydrogels represent a new approach for the treatment of HF. In this review, we present a current perspective of hydrogel-based approaches for cardiac tissue engineering and myocardial regeneration in ischemia-induced HF, with an emphasis on functional studies, translation, and clinical advancements.In recent decades, cellulose has been extensively investigated due to its favourable properties, such as hydrophilicity, low-cost, biodegradability, biocompatibility, and non-toxicity, which makes it a good feedstock for the synthesis of biocompatible hydrogels. The plentiful hydrophilic functional groups (such as hydroxyl, carboxyl, and aldehyde groups) in the backbone of cellulose and its derivatives can be used to prepare hydrogels easily with fascinating structures and properties, leading to burgeoning research interest in biomedical applications. This review focuses on state-of-the-art progress in cellulose-based hydrogels, which covers from their preparation methods (including chemical methods and physical methods) and physicochemical properties (such as stimuli-responsive properties, mechanical properties, and self-healing properties) to their biomedical applications, including drug delivery, tissue engineering, wound dressing, bioimaging, wearable sensors and so on. Moreover, the current challenges and future prospects for cellulose-based hydrogels in regard to their biomedical applications are also discussed at the end.Hydrogels have attracted increasing research interest in recent years due to their dynamic properties and potential applications in biomaterials. Concurrently, macrocycle-based host-guest interactions have played an important role in the development of supramolecular chemistry. Recently, research towards dynamic hydrogels mediated by various macrocyclic host-guest interactions has been gradually disclosed. In this review, we will outline the burgeoning progress in the development of functional hydrogels mediated by various host molecules, such as cyclodextrins, cucurbit[n]urils, calix[n]arenes, pillar[n]arenes, and other macrocycles. Smart hydrogels with outstanding properties, like biocompatibility, toughness, and self-healing, are mainly focused. DPP inhibitor We believe that this review will highlight the potential of dynamic hydrogels mediated by macrocycle-based host-guest interactions.Nanodiamonds containing the nitrogen vacancy centre (NV) have a significant role in biosensing, bioimaging, drug delivery, and as biomarkers in fluorescence imaging, due to their photo-stability and biocompatibility. The optical read out of the NV unpaired electron spin has been used in diamond magnetometry to image living cells and magnetically labelled cells. Diamond magnetometry is mostly based on the use of bulk diamond with a large concentration of NV centres in a wide field fluorescence microscope equipped with microwave excitation. It is possible to correlate the fluorescence maps with the magnetic field maps of magnetically labelled cells with diffraction limit resolution. Nanodiamonds have not as yet been implemented to image magnetic fields within complex biological systems at the nanometre scale. Here we demonstrate the suitability of nanodiamonds to correlate the fluorescence map with the magnetic imaging map of magnetically labelled cells. Nanoscale optical images with 17 nm resolution of nanodiamonds labelling fixed cells bound to iron oxide magnetic nanoparticles are demonstrated by using a single molecule localisation microscope.