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Chronic inflammatory diseases, such as intervertebral disc degeneration (IVDD), which affect the lives of hundreds of millions of people, still lack effective and precise treatments. In this study, a novel hydrogel system with many extraordinary properties is developed for gene–cell combination therapy of IVDD. Phenylboronic acid‐modified G5 PAMAM (G5‐PBA) is first synthesized, and therapeutic siRNA silencing the expression of P65 mixed with G5‐PBA (siRNA@G5‐PBA) is then embedded into the hydrogel (siRNA@G5‐PBA@Gel) based on multi‐dynamic bonds including acyl hydrazone bonds, imine linkage, π–π stacking, and hydrogen bonding interactions. Local and acidic inflammatory microenvironment‐responsive gene‐drug release can achieve spatiotemporal regulation of gene expression. In addition, gene‐drug release from the hydrogel can be sustained for more than 28 days in vitro and in vivo, greatly inhibiting the secretion of inflammatory factors and the subsequent degeneration of nucleus pulposus (NP) cells induced by lipopolysaccharide (LPS). Through prolonged inhibition of the P65/NLRP3 signaling pathway, the siRNA@G5‐PBA@Gel is verified to relieve inflammatory storms, which can significantly enhance the regeneration of IVD when combined with cell therapy. Overall, this study proposes an innovative system for gene–cell combination therapy and a precise and minimally invasive treatment method for IVD regeneration. This work innovatively develops an injectable, self‐healing, adhesive, hemostatic, antibacterial, and biocompatible multifunctional hydrogel system for local and acidic inflammatory microenvironment‐responsive gene‐drug release and cell delivery, which is a precise and minimally invasive treatment method of IVDD and can achieve IVD regeneration through gene–cell combination therapy.

Polymeric hydrogels are widely explored materials for biomedical applications. However, they have inherent limitations like poor resistance to stimuli and low mechanical strength. This drawback of hydrogels gave rise to ‘‘smart self-healing hydrogels’’ which autonomously repair themselves when ruptured or traumatized. It is superior in terms of durability and stability due to its capacity to reform its shape, injectability, and stretchability thereby regaining back the original mechanical property. This review focuses on various self-healing mechanisms (covalent and non-covalent interactions) of these hydrogels, methods used to evaluate their self-healing properties, and their applications in wound healing, drug delivery, cell encapsulation, and tissue engineering systems. Furthermore, composite materials are used to enhance the hydrogel’s mechanical properties. Hence, findings of research with various composite materials are briefly discussed in order to emphasize the healing capacity of such hydrogels. Additionally, various methods to evaluate the self-healing properties of hydrogels and their recent advancements towards 3D bioprinting are also reviewed. The review is concluded by proposing several pertinent challenges encountered at present as well as some prominent future perspectives.

The aim of this paper is to research, theoretically and empirically, the impact of institutional reforms on economic growth in transition countries (new European Union members) and Croatia, in the period from 1996 to 2012. In order to prove the hypothesis, we will use panel analysis of transition economies and Croatia, namely the Arellano-Bond dynamic panel analysis. The analysis includes two dependent variables (gross domestic product per capita [G.D.P./p.c.]and the share of export in G.D.P.) and five independent variables (total Heritage Index of Economic Freedom, Worldwide Governance Indicators (W.G.I.) government effectiveness indicator, W.G.I. rule of law indicator, corruption perception index and the index of institutional reforms in transition countries). The results show that there is a significant positive impact of institutional reforms on the economic growth of transition countries and Croatia, which creates preconditions that are essential for the future growth rate of the Croatian economy.

Liquid crystal polymers (LCPs) have gained tremendous attention in recent years due to their great potentials from fabrication of responsive actuators and sensors to construction of intelligent soft robotic and light modulators. However, conventional LCPs with permanent cross‐links present tedious and unmodifiable stimuli‐responsiveness. Recently, dynamic bonds capable to reversibly break and reform have been integrated into LCP, imparting intrinsic dynamic characteristics. The dynamic LCP possesses unprecedented diverse functionalities including reprogrammability, recyclability, and self‐healing ability, becoming much more adaptive to surrounding environmental changes compared with the conventional counterpart. In this review, recent progress of dynamic bond‐based LCPs is summarized. The mechanism, preparation, and functionalities of dynamic LCPs based on dynamic noncovalent bond (DNCB) and dynamic covalent bond (DCB) are poised to be discussed, followed by introducing emergent LCPs combining both of DNCB and DCB. Consequently, the unique functionalities of dynamic bond‐based LCPs will be given. Finally, outlooks of development of the dynamic bond‐based LCPs are presented. Distinct from the covalent bonds, dynamic bonds including dynamic noncovalent bonds and dynamic covalent bonds offer exceptional advantages in adaptability, reprogrammability, and recyclability. This review provides comprehensive summarization of recent progress of dynamic bond‐assisted liquid crystal polymers. The fundamentals and functionalities and potential applications of such emerging materials will be provided.

Dynamic chemistry refers to a type of fundamental science that involves precise construction or regulation of reactional, motional, or constitutional dynamics of chemical systems. Under the meticulous design of chemists, the nanoscopic dynamics, either molecular or supramolecular, are managed to scale up to macroscopic dynamic properties. For example, the stimuli‐induced conformational or configurational changes of polymer skeletons result in unexpected functions of polymers, such as self‐healing and shape‐shifting behaviors. This review focuses on how the microscopic dynamics of these molecular components initiate the reversible macroscopic deformation of the corresponding polymer materials upon external stimuli. The self‐healing and shape‐shifting materials are discussed in terms of the subtle molecular design, dynamic reversible mechanisms, and critical roles of the dynamic components in building these materials. Furthermore, this review puts forward the challenges and opportunities for the field of dynamic polymers in both aspects of fundamental chemistry and material fabrication. We hope this review can provide new inspiration for the development of this particular research field.

In situ hydrogels have attracted increasing interest in recent years due to the need to develop effective and practical implantable platforms. Traditional hydrogels require surgical interventions to be implanted and are far from providing personalized medicine applications. However, in situ hydrogels offer a wide variety of advantages, such as a non-invasive nature due to their localized action or the ability to perfectly adapt to the place to be replaced regardless the size, shape or irregularities. In recent years, research has particularly focused on in situ hydrogels based on natural polysaccharides due to their promising properties such as biocompatibility, biodegradability and their ability to self-repair. This last property inspired in nature gives them the possibility of maintaining their integrity even after damage, owing to specific physical interactions or dynamic covalent bonds that provide reversible linkages. In this review, the different self-healing mechanisms, as well as the latest research on in situ self-healing hydrogels, is presented, together with the potential applications of these materials in tissue regeneration.

Smart molecules have attracted increasing attention due to their transformative role in creating the next generation of smart structures and devices. Smart bistable coordination complexes are a class of functional complexes which have two stable states that can be reversibly switched in response to external stimuli. Such bistable molecules play a vital role in various applications, such as sensors, data storage, spintronics, smart windows, optical switches, information encryption and decryption, displays, actuators, etc. Herein, the recent research studies into the development of these smart bistable metal coordination complexes are reviewed. According to the different external stimuli, these smart bistable coordination systems have been classified and summarized, including light‐responsive systems, thermally‐responsive systems, electrically‐responsive systems, mechanically‐responsive systems, and some other cases. These systems are further subdivided according to the changes in signals (e.g., color, fluorescence, spin state, crystalline phase) under external stimuli. The design principles of each type of smart bistable metal complexes as well as their broad and innovative applications are comprehensively described. Finally, the challenges and opportunities in this field are briefly analyzed and discussed. Smart bistable complexes play a vital role in various applications such as sensors, data storage, spintronics, smart windows, optical switches, information encryption and decryption, displays, actuators, and so on. In this review, we summarize smart bistable complexes in terms of external stimulus approach and discuss their design guidelines, properties, and applications.

Facing the ubiquitous corrosion threat, the great significance of developing high-performance protective materials with the dual function of self-healing defects and self-warning damage is extremely challenging. Herein, inspired by the biological skin and pearls, we proposed that the biological polyurethanes (PU) embedded with multiple dynamic bonds (reversible hydrogen bonds and aromatic disulfide bonds) were combined with polydopamine (PDA)/1,10-phenanthroline (Phen)/graphene oxide (GO) (PPG) nanosheets (PDA encapsulated GO with Phen) to obtain a versatile nacre structure polymer with the interface hydrogen bond between PPG and PU matrix. The biomimetic polymer not only guarantees ultrahigh toughness (116.1 MJ·m −3 ) and abnormal elongation (2320%) but shows satisfactory repair performance (81% under 25 °C for 3 h), and the coating can accelerate damage recovery (87%) under near-infrared light (NIR) irradiation for 1 h due to the photothermal properties of PPG. The warning of damages in the coating can be enabled through the Phen chelation Fe 2+ ions that bring in the corrosion reaction to produce a conspicuous red color, thereby achieving the active warning function of the bionic coating on defects for the first time. In addition, the electrochemical tests exhibit that the repair performance and protection effect of the biomimetic coating in 3.5 wt.% NaCl solution are also trustworthy, and this highly reliable bio-based bionic coating brings a revolutionary program to inaugurate multifunctional and high-performance intelligent materials under harsh environments.

Fatigue threshold (G₀) is the energy release rate below which no fatigue crack advances. Understanding the relationship between the static/dynamic structures and G₀ of viscoelastic hydrogels is crucial for designing materials exposed to cyclic loading. In this study, we elaborate the role of dynamic bonds in the G₀ of tough hydrogels. Using polyampholyte hydrogels possessing abundant ionic dynamic bonds, we can adopt a time–salt superposition principle to access a wide range of time scales that are difficult to access in fatigue tests. G₀ was found rate-independent in the elastic regime at a low cyclic strain rate, whereas weak power-law relations between G₀ and strain rate were first observed in viscoelastic regimes. The former agrees with the molecular explanation of the Lake–Thomas model, and the latter is related to the self-healing property of dynamic bonds in the viscoelastic regime that protects the permanent bonds from breaking. This work modifies the previous consideration that the dynamic bonds only contribute to the fracture toughness and crack resistance but not to the G₀.

Microcellular thermoplastic polyurethane (TPU) foams with dynamic covalent bonds demonstrating exceptional self-healing capabilities, coupled with precisely controlled micron-scale cellular architectures, present a promising solution for developing advanced materials that simultaneously achieve damage recovery and low density. In this study, a series of self-healable materials (named as PU-S) with high light transmittance possessing two dynamic covalent bonds (oxime bond and disulfide bond) in different ratios were fabricated by the one-pot method, and then the prepared PU-S were foamed utilizing the green and efficient supercritical carbon dioxide (scCO2) foaming technology. The PU-S foams possess multiple dynamic covalent bonds as well as porous structures, and the effect of the dynamic covalent bonds endows the materials with excellent self-healing properties and recyclability. Owing to the tailored design of dynamic covalent bonding synergies and micron-sized porous structures, PU-S5 exhibits hydrophobicity (97.5° water contact angle), low temperature flexibility (Tg = −30.1 °C), high light transmission (70.6%), and light weight (density of 0.12 g/cm3) together with high expansion ratio (~10 folds) after scCO2 foaming. Furthermore, PU-S5 achieves damage recovery under mild thermal conditions (60 °C). Accordingly, self-healing PU-S based on multiple dynamic covalent bonds will realize a wide range of potential applications in biomedical, new energy automotive, and wearable devices.