Recently, flexible and wearable electronics have gained considerable research interest due to their potential applications in wearable devices, energy storage materials, electronic skins, sensors,
...etc.
Compared to elastomers, hydrogels demonstrate more potential for flexible electronics because of their biomimetic structures, suitable mechanical properties and excellent biocompatibility. Among all the designs, nanocomposite hydrogel-based strain and pressure sensors which can transmit external stimulus to electrical signals have been intensely investigated due to their high mechanical strength, considerable conductivity and outstanding sensitivity. Numerous reports have been dedicated to the designs, preparations and applications of nanocomposite hydrogels. This review provides an up-to-date and comprehensive summary of research progresses of nanocomposite hydrogel-based strain and pressure sensors including designing strategies, preparing methods and applications of the five nanofiller based hydrogel sensors including carbon nanotube based, graphene oxide based, MXene based, polymer nanofiller based and other nanofiller based sensors. Representative cases are carefully selected and discussed regarding the fabrication, merits and demerits, respectively. Finally, perspectives and challenges are presented for the designs of future nanocomposite hydrogel-based strain and pressure sensors.
Design methods and applications of nanocomposite hydrogel-based strain and pressure sensors have been summarized and classified in this review.
Conductive hydrogels have become one of the most promising materials for skin-like sensors because of their excellent biocompatibility and mechanical flexibility. However, the limited stretchability, ...low toughness, and fatigue resistance lead to a narrow sensing region and insufficient durability of the hydrogel-based sensors. In this work, an extremely stretchable, highly tough, and anti-fatigue conductive nanocomposite hydrogel is prepared by integrating hydrophobic carbon nanotubes (CNTs) into hydrophobically associated polyacrylamide (HAPAAm) hydrogel. In this conductive hydrogel, amphiphilic sodium dodecyl sulfate was used to ensure uniform dispersion of CNTs in the hydrogel network, and hydrophobic interactions between the hydrogel matrix and the CNT surface formed, greatly improving the mechanical properties of the hydrogel. The obtained CNTs/HAPAAm hydrogel showed excellent stretchability (ca. 3000%), toughness (3.42 MJ m–3), and great anti-fatigue property. Moreover, it exhibits both high tensile strain sensitivity in the wide strain ranges (gauge factor = 4.32, up to 1000%) and high linear sensitivity (0.127 kPa–1) in a large-pressure region within 0–50 kPa. The CNTs/HAPAAm hydrogel-based sensors can sensitively and stably detect full-range human activities (e.g., elbow rotation, finger bending, swallowing motion, and pronouncing) and handwriting, demonstrating the CNTs/HAPAAm hydrogel’s potential as the wearable strain and pressure sensors for flexible devices.
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Oxygen and reactive oxygen species (ROS), as indispensable small molecular substances in the basic metabolism of life, have become the key to the success of implantable medical materials, and their ...importance cannot be overstated. Either improving the hypoxia environment in vivo to avoid tissue damage or using the ROS to selectively kill cells are the strategies adopted in the actual biomedical applications. Therefore, it is crucial to control the transfer of oxygen and the conversion of ROS. In this review, we summarize the common oxygen sources and divide them into inorganic sources, biological sources and organic oxygen sources. For the carriers that are used for loading of the oxygen sources and controlling the behavior of oxygen generation and active oxygen conversion, we classify and explain the respective mechanisms and functions of inorganic materials, natural and synthetic polymers. Moreover, by analyzing the current biomedical applications, we describe the challenges and prospects of oxygen-generating materials in the last section.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Zwitterionic hydrogels exhibit eminent nonfouling and hemocompatibility. Several key challenges hinder their application as coating materials for blood-contacting biomedical devices, ...including weak mechanical strength and low adhesion to the substrate. Here, we report a poly(carboxybetaine) microgel reinforced poly(sulfobetaine) (pCBM/pSB) pure zwitterionic hydrogel with excellent mechanical robustness and anti-swelling properties. The pCBM/pSB hydrogel coating was bonded to the PVC substrate via the entanglement network between the pSB and PVC chain. Moreover, the pCBM/pSB hydrogel coating can maintain favorable stability even after 21 d PBS shearing, 0.5 h strong water flushing, 1000 underwater bends, and 100 sandpaper abrasions. Notably, the pCBM/pSB hydrogel coated PVC tubing can not only mitigate the foreign body response but also prevent thrombus formation ex vivo in rats and rabbits blood circulation without anticoagulants. This work provides new insights to guide the design of pure zwitterionic hydrogel coatings for biomedical devices.
While silver nanoparticles are widely used to endow materials with antibacterial activity, silver nanowires (AgNWs) have not attracted much attention. Herein, the composites of bacterial cellulose ...(BC) and AgNWs were prepared through a novel step-by-step in situ biosynthesis which retains the three-dimensional network of BC. The results of water vapor permeability, water uptake rate, and water retention rate showed that the BC/AgNW wound dressings could absorb wound skin exudates and maintain moisture environments. Furthermore, the BC/AgNW dressings were robust and stretchable. More importantly, the BC/AgNW dressings exhibited sustained release of Ag+. The results from animal tests indicated that the BC/AgNW dressing with 38.4 wt% AgNWs exhibited higher expression levels of cytokeratin-10 and integrin-β4, greater proliferation of keratinocytes and formation of epithelial tissues and greatly improved skin regeneration over the bare BC. We propose that the integrated nanofibrous structure and the excellent and sustained antibacterial activity of AgNWs are responsible for the excellent in vivo wound healing ability and biocompatibility. These results suggest that the BC/AgNW composites have promising application as wound dressings.
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•Silver nanowires (AgNWs) and bacterial cellulose (BC) were integrated to obtain an advanced wound dressing.•The BC/AgNW dressing exhibited sustained release of silver ions.•The BC/AgNW dressing is robust, stretchable, antibacterial, and biocompatible.•The BC/AgNW dressing showed improved in vivo skin regeneration over bare BC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Intraperitoneal adhesions are common and serious complications after surgery. Deposition of proteins and inflammatory response on an injured cecum are the main factors resulting in the formation of ...adhesion. In this study, purely zwitterionic hydrogels (Z-hydrogels) are developed using thiolated poly(sulfobetaine methacrylate-co-2-((2-hydroxyethyl)disulfanyl)ethyl methacrylate) poly(SBMA-co-HDSMA) as the network backbone and divinyl-functionalized sulfobetaine (BMSAB) as the zwitterionic cross-linker via the thiol–ene click reaction. To improve the anti-inflammatory activity, cefoxitin sodium is loaded into Z-hydrogels (Z/C-hydrogel) to construct the physical barrier/drug system. The gelation time, mechanical behavior, and swelling ratio of the prepared Z-hydrogel can be modulated via adjusting the SBMA/HDSMA ratio in the copolymer. Moreover, they not only exhibit excellent resistance to protein and fibroblast adhesion but also show good biocompatibility and hemocompatibility. To assess its anti-adhesion effects in vivo, the Z-hydrogel is injected on the injured cecum surface using a rat model of sidewall defect-cecum abrasion. The results show that the Z-hydrogel can completely cover the irregular cecum surface and effectively suppress the formation of postoperative adhesion via reducing protein deposition and resisting fibroblast adhesion. Moreover, the introduction of cefoxitin sodium decreases the inflammatory response after surgery, thus further improving the anti-adhesion effect. Overall, we suggest that the Z-hydrogel is a promising candidate for the prevention of a postsurgical peritoneal adhesion.
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Hydrogel-based strain sensors have been widely investigated owing to their intrinsic flexible and extensible properties. However, integrating good mechanical properties and excellent strain ...sensitivity into one hydrogel remains a challenge. In this work, a dual physical cross-linked carboxymethyl cellulose-Fe
3+
/polyacrylamide (CMC-Fe
3+
/PAAm) double network hydrogel was developed by facile two-step method. In this hydrogel, the Fe
3+
cross-linked CMC acts as the first network for dissipating energy and hydrophobic association PAAm acts as the second network to maintain the integrity of hydrogel. Owing to these physical interactions, the as-prepared hydrogel shows good mechanical properties (e.g., tensile strength, 1.82 MPa; toughness, 6.52 MJ/m
3
). Furthermore, these mechanical behaviors can be modulated by adjusting the solid content, CMC/PAAm ratio, Fe
3+
concentration and soaking time in Fe
3+
solution. Moreover, the obtained hydrogel shows excellent self-recovery and anti-fatigue property due to the reversibility of dual physical cross-linked interactions. Additionally, the CMC-Fe
3+
/PAAm hydrogel shows good conductivity (1.82 S/m), strain sensitivity (gauge factor = 4.02 at 50–600% strain), and fast response time (260 ms). Based on the high strain sensitivity, the CMC-Fe
3+
/PAAm hydrogel can fabricate a flexible strain sensor for precisely monitoring various human motions. This study suggests that the CMC-Fe
3+
/PAAm hydrogel exhibits potential application in the flexible and stretchable strain sensors.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
With advances in tissue engineering and bioelectronics, flexible electronic hydrogels that allow conformal tissue integration, online precision diagnosis, and simultaneous tissue ...regeneration are expected to be the next-generation platform for the treatment of myocardial infarction. Here, we report a functionalized polyaniline-based chronological adhesive hydrogel patch (CAHP) that achieves spatiotemporally selective and conformal embedded integration with a moist and dynamic epicardium surface. Significantly, CAHP has high adhesion toughness, rapid self-healing ability, and enhanced electrochemical performance, facilitating sensitive sensing of cardiac mechanophysiology-mediated microdeformations and simultaneous improvement of myocardial fibrosis-induced electrophysiology. As a result, the flexible CAHP platform monitors diastolic-systolic amplitude and rhythm in the infarcted myocardium online while effectively inhibiting ventricular remodeling, promoting vascular regeneration, and improving electrophysiological function through electrocoupling therapy. Therefore, this diagnostic and therapeutic integration provides a promising monitorable treatment protocol for cardiac disease.
Brown adipose derived stem cells (BADSCs) have become a promising stem cell treatment candidate for myocardial infarction because of their efficiently spontaneous differentiation capacity towards ...cardiomyocytes. The lack of existing cell passage protocols motivates us to develop a neotype 3D cell expansion technique for BADSCs. In this study, “clickable” zwitterionic starch based hydrogels are developed using methacrylate modified sulfobetaine derived starch with dithiol-functionalized poly (ethylene glycol) as crosslinker via the “thiol-ene” Michael addition reaction. Moreover, CGRGDS peptide is immobilized into the hydrogel via a similar “clickable” approach. Their Young's moduli range from 22.28 to 74.81 kPa depending on the concentration of precursor solutions. Excellent anti-fouling property is also presented owing to the introduction of zwitterionic moieties. BADSCs are homogeneously encapsulated in the hydrogels and then routinely cultured for 10 days. Results suggest a capacious cell proliferation and the extent increases with either the decrease of mechanical strength or the introduction of CGRGDS. More excitingly, the cell “stemness” is well maintained during this period and the expanded cells released from the hydrogels well keep the efficiently spontaneous cardiomyogenic differentiation capacity. Therefore, it is suggested that zwitterionic starch based hydrogel is able for the expansion and “stemness ” maintenance of BADSCs.
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•“Clickable” zwitterionic starch-based hydrogels are developed via “thiol-ene” Michael addition crosslinking.•S/P hydrogel can promote the cell proliferation of encapsulated BADSCs.•Cellular “stemness” and instinctively biological behaviors of BADSCs can be well maintained by S/P hydrogel.•An effective 3D expansion technique is successfully developed for BADSCs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Natural polysaccharides play an important role in the formation of nanohydroxyapatite (nHA) crystals in biological systems. In this study, we synthesized nHA crystals in the presence of four ...polysaccharides, i.e., pectin, carrageenan, chitosan, and amylose, referred as PeHA, CaHA, CsHA, and AmHA, respectively. X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscope, and thermogravimetric analysis were used to investigate the formation of nHA crystals. The shape of prepared nHA crystals is needle/rod-like in all cases, whereas the size increases in the order of PeHA, CaHA, CsHA, and AmHA. The presence of polysaccharides induces the heterogeneous nucleation of nHA and further modulates the crystal growth. Our data suggest that the interaction intensity between nHA and polysaccharides is in the decreasing order of PeHA, CaHA, CsHA, and AmHA, resulting in the smallest nHA crystals with pectin. It is also demonstrated that a high polysaccharide concentration and short reaction time are adverse to nHA crystals, especially for the polysaccharides with carboxyl groups. This study can provide insight into the effects of polysaccharides with different chemical functional groups (−COOH, −OSO3H, −NH2, −OH) on the formation of nHA crystals.
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