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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-Fe3+/polyacrylamide (CMC-Fe3+/PAAm) double network hydrogel was developed by facile two-step method. In this hydrogel, the Fe3+ 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/m3). Furthermore, these mechanical behaviors can be modulated by adjusting the solid content, CMC/PAAm ratio, Fe3+ concentration and soaking time in Fe3+ 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-Fe3+/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-Fe3+/PAAm hydrogel can fabricate a flexible strain sensor for precisely monitoring various human motions. This study suggests that the CMC-Fe3+/PAAm hydrogel exhibits potential application in the flexible and stretchable strain sensors.

Intra-peritoneal adhesion are common and serious complications after surgery. Deposition of proteins and inflammatory response on injured cecum are main factors resulting in the formation of adhesi...

Natural rubber (NR) grafted with 2-ethylhexyl acrylate (2-EHA) and methacrylic acid (MAA, collectively NR-g-PEHA/MAA) was synthesized by emulsion polymerization. Tetraethylenepentamine and cumene hydroperoxide were used as redox initiators. The successful grafting of 2-EHA and MAA onto NR was confirmed by Fourier transform infrared spectroscopy. The morphology of the NR latex particles was observed by transmission electron microscopy. The effects of reaction temperature, initiator dosage, feeding mode, and hard monomer content on the mechanical properties of the modified NR film were investigated. Grafted polymer chains were unevenly wrapped on the outside of NR particles, and smaller particles were more easily grafted. Crosslinking was characterized using a toluene swelling method. Thermal stability and glass transition temperature were examined by differential scanning calorimetry and thermogravimetric analysis. The results showed that the thermal stability of NR-g-PEHA/MAA had been improved, and the glass transition temperature (Tg) was unchanged.

Circulation stability in vivo and stimuli-responsiveness under a tumor microenvironment of the polymeric prodrug micellar drug delivery systems are very critical to improve the tumor therapeutic efficiency. In this study, a series of polyamidoamine (PAMAM)-graft-poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA)-block-poly(betaine sulfonate) (PSBMA) (PDS) unimolecular micelles were prepared via atom transfer radical polymerization. PAMAM served as a hydrophobic core to load the drug, the PDMAEMA segment was a middle layer to provide both thermo- and pH-sensitivity, whereas the PSMBA shell layer was used to improve the stability of the unimolecular micelles. The PDS exhibited a spherical structure with the size of 10-20 nm at pH 7.4. PDS micelles had excellent stability to resist the large volume liquid dilution. Moreover, it exhibited excellent stability in a complex biological microenvironment because of a superhigh antiprotein adhesion capacity of the PSBMA shell layer compared with PAMAM micelles. Drug release studies confirmed that the DOX can remain in the PDS micelles at pH 7.4 and 37 °C, whereas it can rapidly be released when the pH decreases to 5.0 and/or the temperature increases to 40 °C. In vitro studies suggested that the PDS drug delivery system can effectivity induce apoptosis and inhibit the proliferation of cancer cells. In vivo studies suggested that the PDS micelles prolonged the circulation time, decreased the side effects, and increased the antitumor efficacy. Therefore, the prepared PDS micelles are a potential anticancer drug delivery carrier for cancer therapy.

The efficient removal of toxic metal ions from waste water is of critical importance in environmental protection. In this study, we report the incorporation of graphene oxide (GO) into bacterial cellulose (BC) and the effect on the removal of metal ions from waste water. The as-prepared BC/GO adsorbents have a three-dimensional (3D) network structure with interconnected pores and high porosity. The adsorption capacities and efficiencies of the BC/GO adsorbents with varying GO contents were compared by using Cu2+, Cd2+, and Pb2+ as model heavy metal ions. The incorporated GO into the BC/GO adsorbents plays a critical role in removing metal ions through strong electrostatic interactions between the positive metal ions and the negative functional groups on GO. In addition, the effects of pH, contact time, adsorbent dose, and ion concentration on the adsorption behavior of the BC/GO adsorbents were investigated. The data from adsorption kinetics indicate that the adsorption of Cu2+, Cd2+, and Pb2+ on BC/GO obeys a pseudo-second-order model, while the adsorption isotherms vary with the type of metal ions. The desorption and readsorption experiments of the BC/GO adsorbents demonstrate good recyclability. It has been demonstrated that incorporating GO into BC is an effective way to improve the adsorption behavior of BC.

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.

Flexible and stretchable electronics have received tremendous attention for next-generation human-friendly electronic applications. However, fabrication of transparent, fully recyclable and stretchable electronic sensors with low-temperature stability using biocompatible natural polymer-based hydrogels still remains a great challenge. In this study, a green and fully recyclable stretchable electronic sensor with high transparency and ultra-low operating temperature is constructed using ionic conductive gelatin organohydrogels. These gelatin organohydrogels are prepared by a simple strategy of immersing gelatin pre-hydrogels in citrate (Na3Cit) water/glycerol solutions. The existence of Na3Cit in the organohydrogel not only induces the formation of multiple non-covalent cross-linking points, endowing the organohydrogel with high mechanical performances, but also makes the organohydrogel have excellent ionic conductivity. The organohydrogel is also highly transparent and exhibits outstanding antifreezing properties. The mechanical robustness, conductivity and transparency of the organohydrogel can be well maintained even at −60 °C. As a result, a stretchable and transparent electronic sensor based on this organohydrogel is fabricated, which is strain-sensitive with a large linear sensing window and excellent stability. More importantly, the organohydrogel-based electronic sensor can be fully recycled due to the reversible non-covalently crosslinked structure, and the recycled organohydrogel regains its mechanical and sensing properties. The obtained sensors could precisely detect various human activities even below −30 °C, indicating the potential applications of the organohydrogel-based electronic sensor in flexible and stretchable electronics in a broad range of temperature.

The development of three-dimensional conductive scaffolds is vital to support the adhesion, proliferation and myocardial differentiation of stem cells in cardiac tissue engineering. Herein, we describe a facile approach for preparing a poly(3,4-ethylenedioxythiophene)/alginate (PEDOT/Alg) porous scaffold with a wide range of desirable properties. In the PEDOT/Alg scaffold, chemically crosslinked alginate networks are formed using adipic acid hydrazide as the crosslinker, and PEDOT is synthesized in situ in the alginate matrix simultaneously. PEDOT exists in the alginate matrix as particles and its morphology can be modulated by adjusting the ratio of PEDOT/alginate. The results also show that the swelling properties, degradation behaviors, mechanical strength and conductivity of the PEDOT/Alg scaffold can be controlled via adjusting the PEDOT/alginate ratio. The introduction of PEDOT can overcome the brittle nature of the pure alginate scaffold. Moreover, the PEDOT/Alg scaffold exhibits excellent conductivity (as high as 6 × 10−2 S cm−1). The introduction of PEDOT improves the protein absorption capacity of the alginate scaffold. To explore its potential application in cardiac tissue engineering, brown adipose-derived stem cells (BADSCs) are seeded in the prepared PEDOT/Alg porous scaffold. The results suggest that the PEDOT/Alg porous scaffold can support the attachment and proliferation of BADSCs. Moreover, it is beneficial for the cardiomyogenic differentiation of BADSCs, especially under electrical stimulation. Overall, we conclude that the PEDOT/Alg porous scaffold may represent an ideal platform to modulate the biological behaviors of BADSCs.

Uniformly dispersing silver nanowires (AgNWs) in polymer matrices is of paramount importance for developing high-performance electromagnetic interference (EMI) shielding materials. Herein, new flexible and robust high-efficiency bacterial cellulose (BC)-based EMI shielding papers were developed via a modified step-by-step in situ biosynthesis method, in which, AgNWs were well distributed in the BC network. The BC nanofibers and AgNWs could form an effective entangled network with hydrogen bonding, efficiently strengthening the produced BC/AgNW papers. An electrical conductivity of 608365 S m1 was achieved for a BC/AgNW paper with a AgNW content of 36.5 wt%, which is superior to almost all AgNW-containing papers reported so far. Moreover, the BC/AgNW paper could sustain mechanical deformation and vigorous washing, without losing electrical conductivity. Additionally, this paper presents an ultrahigh specific EMI shielding effectiveness of 6400 dB mm1, which is higher than almost all previously reported AgNW-based polymer composites. The proposed approach in this study provides a facile and scalable fabrication route for producing flexible and highly conductive BC/AgNW papers, which are of great potential as electrically conductive components and EMI shielding elements in advanced applications., This work was supported by the National Natural Science Foundation of China (Grant Nos. 51973058 and 31870963), Jiangxi Provincial Natural Science Foundation (Grant No. 20202ACBL214007), Key Research and Development Program of Jiangxi Province (Grant No. 20192ACB80008) and the Key Project of Natural Science Foundation of Jiangxi Province (20202ACBL204013)., info:eu-repo/semantics/publishedVersion

In this work, doxorubicin (DOX) was intercalated into layered nanohydroxyapatite (LHAp). The drug loaded LHAp (DOX@LHAp) was then mixed with poly(lactic-co-glycolic acid) (PLGA) and electrospun to yield DOX@LHAp/PLGA composite scaffolds. As control, needle-like nanohydroxyapatite (nHAp) was also used to make an DOX@nHAp/PLGA composite scaffold and bare DOX was used to fabricate DOX/PLGA scaffold. The morphology, release behavior of DOX, and capability to inhibit cancer cells were assessed. The addition of DOX-loaded nHAp to PLGA causes a slight decrease in the average fiber diameter of DOX@LHAp/PLGA as compared to PLGA. The in vitro drug release tests reveal a much faster release of DOX from DOX/PLGA than DOX@LHAp/PLGA. Moreover, DOX@LHAp/PLGA displays a more sustainable release over DOX@nHAp/PLGA due to the storage of DOX in the gallery of LHAp, which is further proved by their cancer cell inhibition results. We believe that the DOX@LHAp/PLGA scaffold has potential as an implantable drug delivery system.

In this study, a novel mesoporous bioactive glass nanotube (MBGN) scaffold has been fabricated via template-assisted sol-gel method using bacterial cellulose (BC) as template and nonionic block copolymer (P123) as pore-directing agent. The scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption analysis. Furthermore, simvastatin was used to evaluate the loading efficiency and release kinetics of the scaffold. The obtained scaffold displays nanofiber-like morphology, ordered mesopores on the tube walls, and interconnected three-dimensional (3D) network structure that completely replicates the BC template. In addition, it shows dual pore sizes (16.2 and 3.3 nm), large specific surface area (537.2 m2 g−1) and pore volume (1.429 cm3 g−1). More importantly, the scaffold possesses excellent apatite-forming ability and sustainable drug release as compared to the counterpart scaffold without mesopores. This unique scaffold can be considered a promising candidate for drug delivery and bone tissue regeneration.

Graphene-based nanomaterials have been used as biomaterials to enhance cell adhesion, growth, and differentiation. However, the effect of graphene materials on cancer cell behavior has not been thoroughly investigated. Herein, we have incorporated graphene oxide (GO) into cellulose acetate (CA) to develop nanofibrous scaffolds for in vitro cancer cell culture, which is a crucial step for drug screening and cancer research. The Go/CA scaffolds were seeded with breast cancer cells and cell viability, proliferation, adhesion, infiltration, and morphology were assessed. Mechanical characterization demonstrated that the mechanical properties of GO/CA scaffolds were significantly better than bare CA scaffold and improved with increasing GO content. More importantly, the in vitro cell studies showed that the cancer cells on GO/CA scaffolds had significantly higher viability and better cell adhesion and growth than bare CA. Our results confirm an important role of GO in improving mechanical properties and cancer cell performance on GO/CA scaffolds. These results suggest the potential of the GO/CA scaffolds as a promising candidate for in vitro cancer models.

Hydrogels based on supramolecular noncovalent interactions have attracted great research interest but are still limited by relatively low mechanical strength and performance deterioration at subzero temperatures because of the formation of ice crystallization. In this study, an antifreezing and mechanically strong gelatin supramolecular organohydrogel is prepared via a simple strategy of immersing a gelatin pre-hydrogel in the citrate (Cit) water/glycerol mixture solution. In the organohydrogel, a part of water molecules are replaced by glycerol, which inhibits the formation of ice crystallization even at extremely low temperature. In addition, the formation of noncovalent interactions such as the hydrophobic aggregation induced by the salting-out effect, ionic interactions between the -NH3+ of gelatin and Cit3- anions, and hydrogen bonding between gelatin chains and glycerol endows the organohydrogels with high mechanical strength and toughness. The supramolecular organohydrogel can maintain its mechanical flexibility even at -80 °C or be stored for a long time. Moreover, the nature of noncovalent interactions endows the organohydrogel with intriguing thermoplasticity, good healable ability, and excellent adhesive behavior at various substrate surfaces.

The spread of cancer cells to skeletal tissues which mainly consist of hydroxyapatite (HAp) may indicate some correlation between cancer cells and HAp. It is well accepted that an effective experimental model (in vitro cancer model) which mimics the microenvironment in vivo is of great importance for cancer research. Herein, for the first time, HAp nanoparticles are incorporated into poly(lactic-co-glycolic acid) (PLGA) nanofibers to construct biomimetic 3D nanofibrous scaffolds as an in vitro cancer model. The morphologies, structure, mechanical and thermal properties of the PLGA/HAp scaffolds were characterized. The as-prepared PLGA/HAp scaffolds exhibit decreased fiber diameter, enhanced mechanical properties (31% and 8% improvement in tensile strength and modulus, respectively), and rougher surface over PLGA scaffold. The in vitro biocompatibility of PLGA/HAp scaffolds was evaluated with breast cancer cell line (MCF-7) using PLGA scaffold as control and cell cycle progression was detected by flow cytometry. MTT assay and live staining results demonstrate that PLGA/HAp scaffolds can better support cell viability and proliferation over PLGA scaffold. Analysis of cell cycle reveals that DNA synthesis, cell division, and proliferation of cancer cell are related to the presence of HAp in PLGA nanofibers. Our studies demonstrate the suitability of HAp-incorporated PLGA fibrous scaffolds as a promising platform for 3D cancer cell culture.

Herein, we develop a fluorescence sensing platform based on boron and nitrogen co-doped graphene quantum dots (B,N-GQDs), which are synthesized by a one-step bottom-up hydrothermal method. The prepared B,N-GQDs exhibit high-fluorescence quantum yield (75%) and long fluorescence lifetime (12.86 ns). In the B,N-GQDs–Hg2+ system, the fluorescence of B,N-GQDs is quenched with increasing Hg2+ concentration due to the affinity interaction between the surface functional groups of B,N-GQDs and Hg2+. Subsequently, the quenched fluorescence of the B,N-GQDs–Hg2+ system is gradually recovered with the addition of F− ions due to their strong affinity with Hg2+. The linear ranges for the detection of Hg2+ and F− ions are 0.2–2.6 μM and 0.25–7.0 mM, respectively, and the detection limits are 0.16 μM and 0.18 mM for Hg2+ and F− ions, respectively, which are below the regulatory level of 0.25 μM and 0.526 mM in the Integrated Wastewater Discharge Standard. Therefore, B,N-GQDs provide a facile and effective approach for the detection of both Hg2+ and F− ions with real-time monitoring and high-speed measuring.

Incorporating bioactive nanofillers and creating porous surfaces are two common strategies used to improve the tissue integration of polyetheretherketone (PEEK) material. However, few studies have reported the combined use of both strategies to modify PEEK. Herein, for the first time, dual nanoparticles of graphene oxide (GO) and hydroxyapatite (HAp) were incorporated into PEEK matrix to obtain ternary composites that were laser machined to create macropores with diameters ranging from 200 μm to 600 μm on the surfaces. The surface morphology and chemistry, mechanical properties, and cellular responses of the composites were investigated. The results show that micropatterned pores with a depth of 50 μm were created on the surfaces of the composites, which do not significantly affect the mechanical properties of the resultant composites. More importantly, the incorporation of GO and HAp significantly improves the cell adhesion and proliferation on the surface of PEEK. Compared to the smooth surface composite, the composites with macroporous surface exhibit markedly enhanced cell viability. The combined use of nanofillers and surface macropores may be a promising way of improving tissue integration of PEEK for bone implants.

To accelerate the vascularization of engineered tissue, an endothelial-specific fusion protein (VEGF-Fc), which consists of a human vascular endothelial growth factor (VEGF) and an immunoglobulin G Fc region, was fabricated and used to construct a bioactive interface in a porous scaffold. In this study, VEGF-Fc was immobilized on polycarprolactone (PCL) porous scaffolds by steeping, which is mediated by the hydrophobic binding of the Fc domain. The VEGF-Fc proteins were distributed stably and uniformly throughout the PCL porous scaffolds without affecting their surface morphology and mechanical properties. The immobilized VEGF-Fc activated the phosphorylation of VEGF2 receptor continuously, and further promoted the expressions of PI3K and MAPK, which effectively enhanced the adhesion and proliferation of human vascular endothelial cells (HUVECs). Furthermore, the immobilized VEGF-Fc promoted the migration of HUVECs into the scaffolds, and also enhanced the cellularization and ECM deposition in the subcutaneous implanted scaffolds in rats, which synergistically supported the vascularization of the scaffold in vivo. In view of the advantages of easy use, stability and efficiency, the VEGF-Fc fusion protein appeared to be a promising candidate for surface modification of porous scaffolds for tissue engineering.

Supplementary data to this article can be found online at https:// doi.org/10.1016/j.msec.2019.110416., Developing fibrous scaffolds with hierarchical structures that closely mimic natural extracellular matrix (ECM) is highly desirable. However, fabricating scaffolds with true nanofibers (90%. Additionally, the combination of CA submicrofibers with BC nanofibers leads to significantly improved mechanical properties over nanofibrous BC and submicrofibrous CA scaffolds and enlarged pores over nanofibrous BC scaffold. In addition, the biological behaviors of prepared BC/CA on MC3T3-E1 cells were investigated. Results suggested that BC/CA scaffold is beneficial for cell migration and proliferation. Moreover, the BC/CA scaffold shows higher alkaline phosphatase (ALP) activity, and calcium depositions. In addition, the hierarchical structures can effectively improve the expression of osteogenic gene (ALP mRNA and Runx2 mRNA) and protein (ALP). We believe that the methodology might provide biomimetic morphological microenvironments for enhanced tissue regeneration., This work is supported by the National Natural Science Foundation of China (Grant nos. 51973058, 31870963, 51572187, and 51563008), the Excellent Young Scientists Fund by National Natural Science Foundation of China (No. 31722022), the Youth Science Foundation of Jiangxi Province (No. 20171ACB21036 and 20181BAB216010)., info:eu-repo/semantics/publishedVersion

Blood contacting materials with anti-thrombotic surfaces are highly demanded in clinics. Despite considerable research on surface modifications, limited progress has been made on effective prevention of thrombosis for artificial implants such as mechanical valve prosthesis. Herein, wettability gradient surface, which can ideally exhibit good hemocompatibility and low flow resistance, was developed for potential reduction of thrombosis. The wettability gradient surface on a model substrate of nickel-titanium (NiTi) alloy was prepared via a simple and economic method that combined laser microfabrication and surface stearic acid self-assembly approach. Scanning electron microscopy (SEM) observation confirmed that the wettability gradient surface was composed of a smooth NiTi region and three porous regions with different pore sizes and distances. Contact angle measurement revealed that, together with a low surface energy layer, the structural topography gradient could create a wettability gradient surface on NiTi alloy which could drive droplet motion. When compared with bare NiTi, such wettability gradient surface exhibited better anti-adhesion property, which was beneficial to the hemocompatibility and thus showing a lower hemolysis rate. Additionally, the wettability gradient surface also showed much lower flow resistance than bare NiTi. These results demonstrate that the developed wettability gradient surface may be used to reduce thrombosis.

The fast capacity fading at high current density turns out to be one of the key challenges limiting the broad applications of transition metal oxide-based electrodes. Herein, Fe2O3 nanoparticles with well-defined mesopores wrapped by reduced graphene oxide (RGO) have been synthesized via a facile hydrothermal strategy. The as-prepared nanocomposites were systematically characterized. XPS and Raman analyses confirm the co-existence of Fe2O3 and RGO in the nanocomposite system. SEM and TEM reveal that the mesoporous Fe2O3 nanoparticles have a size of 20–60 nm and are uniformly dispersed and tightly wrapped by RGO. When used as the anode in lithium ion batteries, the mesoporous-Fe2O3/RGO electrode exhibits excellent cycling stability (1098 mA h g−1 after 500 cycles at 1 A g−1) and superior rate capability (574 mA h g−1 at 5 A g−1). The excellent electrochemical performance can be mainly ascribed to the unique mesoscopic architecture that serves as a cushion to alleviate volume change of Fe2O3 during discharge/charge cycles, provides a sustainably large contact area with the electrolyte, and improves electrical conductivity. This unique nanocomposite electrode holds great potential as an anode material for advanced lithium ion batteries.

Development of high performance absorbents is of particular importance in environmental protection. Herein, we report a mechanically robust, ultralight, and recyclable absorbent with highly dispersed two-dimensional (2D) few-layer reduced graphene oxide (FrGO) in a three-dimensional (3D) carbonized bacterial cellulose (CBC) monolith via a novel step-by-step in situ biosynthesis (SBSB) method followed by carbonization. The step-by-step self-assembly produces a mechanically entangled nanostructure between FrGO and CBC nanofibers. The self-assembled CBC/FrGO nanocomposite absorbent possesses multi-scaled pores and large specific area. When used as absorbents, the monolithic CBC/FrGO aerogel exhibits excellent recyclability and high absorption capacities toward numerous oils and organic solvents. These properties, together with the green, cost-effective and scalable production process, make it very promising as a superior all-carbon absorbent for environmental protection.

Postoperative adhesions are very common complications after general abdominal surgery. Although adhesiolysis has been proven effective in eliminating the preexisting adhesions, the new trauma caused by surgical lysis can induce recurrent adhesion. The prevention of recurrent adhesion after adhesiolysis is more difficult because the injury is more severe and adhesion mechanism is more complicated compared with the primary adhesion. In this study, a thermoresponsive hydrogel contained galactose modified xyloglucan (mXG) and hydroxybutyl chitosan (HBC) was developed as a barrier device for recurrent adhesion prevention after adhesiolysis due to its injectability and spontaneous gelling behaviors at the body temperature without any chemical reactions or extra driving factors. First, mXG and HBC were synthesized via enzymatic modification and etherification reaction, respectively. Rheological measurements indicated that the mXG/HBC composite system showed excellent thermosensitivity properties, and their gelation temperature and time can be modulated via adjusting the mXG/HBC ratio. Moreover, the mXG/HBC hydrogel exhibited excellent cytocompatibility and hemocompatibility in vitro. Furthermore, the mXG/HBC hydrogel could promote wound healing in the rat skin wound model. Finally, the efficacy of the mXG/HBC composite hydrogel in the prevention of recurrent adhesion was evaluated in a more rigorous rat repeated-injury adhesion model. The results demonstrated that the composite hydrogel could not only effectively prevent recurrent adhesion after adhesiolysis, but also promote wound healing and reduce scare formation. These results suggested that the mXG/HBC composite hydrogel may be a promising candidate as an injectable anti-adhesion system for clinical applications. Statement of Significance Although adhesiolysis has been proven effective in eliminating the preexisting adhesions, the new trauma caused by surgical lysis can induce recurrent adhesion. So far, most of the existing barrier systems and pharmacological approaches were developed for primary adhesion prevention while few attention has paid on prevention of recurrent adhesion after adhesiolysis. In the present study, we developed a thermoresponsive polysaccharide-based composite hydrogel by simple mixing galactose modified xyloglucan (mXG) and hydroxybutyl chitosan (HBC). The resulting mXG/HBC composite hydrogel not only was easy to handle and highly effective in preventing the recurrent adhesion after adhesiolysis, but also could promote wound healing and reduce scare formation. Our study provide an effective anti-adhesion system for preventing recurrent adhesion after adhesiolysis.

In this study, nano-hydroxyapatite crystals (nHAs) were prepared in the presence of zwitterionic poly(3-carboxy-N,N-dimethyl-N-(3′-acrylamidopropyl) propanaminium inner salt) (PCBAA) at different concentrations and pH microenvironments, denoted as Z-nHAs. The phase, morphology, size of apatite, and interactions between nHAs and PCBAA were systemically characterized via XRD, TEM, FTIR, and TGA. The results showed that Z-nHAs could be formed at all pH ranges in the presence of PCBAA in our experiment. It was different from the case of pure nHAs that could not be formed under an acidic microenvironment without PCBAA. In addition, a higher pH value was beneficial for the formation of nHAs with a smaller size. Z-nHAs exhibited a fiber-like structure at the initial 2 h and became rod-like in shape after 5 h, whereas pure nHAs prepared in water had an irregular flake-like structure. Moreover, 14–20% PCBAA could be incorporated into Z-nHAs via interactions between the quaternary ammonium group (–R3N+) and carboxyl group (–COO−) in the PCBAA chain and Ca2+/PO43− of nHA. A possible mechanism for the formation of Z-nHAs in the presence of PCBAA was proposed based on the experimental results.

In this paper, a novel three-dimensional (3D) scaffold consisting of hollow mesoporous bioactive glass (MBG) nanofibers was synthesized via template-assisted sol–gel method. The hollow mesoporous fibers show an ultra-small diameter of around 40 nm, which is the smallest among all currently reported MBG fibers, and the resultant scaffold possesses a large specific surface area of 579.0 m2 g−1, which is the largest of all MBG products reported so far. It is believed that such ultrafine diameter and the presence of mesopores will endow the scaffold with excellent bioactivity, which makes it a promising candidate in controlled drug release and bone tissue engineering.

Zwitterionic polymers coating shows significant advantages in preventing thrombosis for the treatment of cardiovascular diseases. However, their limited bio-functionality and low durability struggle to meet requirements from clinical applications. In this study, a dihydrolipoic acid-modified sulfobetaine-derived starch (SB-ST-D) hydrogel coating is developed for polyethylene terephthalate (PET) based blood-contacting devices. First, polydopamine (PDA) is deposited on the PET surface (PDA/PET). Then, SB-ST-D is covalently immobilized on the surface of the PDA/PET (SSD/PET) via Michael addition reaction and the hydrogel is formed by the disulfide bridge formation. The obtained SB-ST-D hydrogel coatings not only exhibit excellent biocompatibility, but also effectively resist non-specific protein adsorption, inhibit cell and platelet adhesion, prevent thrombosis, and alleviate inflammation response in vivo. Moreover, the SB-ST-D hydrogel coating can maintain good anti-fouling properties after 45 d of immersion in PBS, 7 d of PBS buffer shearing, and even under mechanical damage. To improve the specific adhesion capacity of human umbilical vein endothelial cells (HUVECs), the REDV is introduced on the SB-ST-D coating surface via thiol–ene click reaction. Results suggest that the obtained coating can promote the adhesion, proliferation, and migration of HUVECs, and decrease the adhesion of human aortic smooth muscle cells simultaneously. Therefore, the prepared SB-ST-D hydrogel coatings with combined durable, antithrombotic, and bio-functional properties will be a milestone in the development of long-term blood-contacting devices.

Effective surface modification to endow pyrolytic carbon (PYC) with long-term anti-thrombotic performance is highly demanded. In this work, a gradient hydrophobic surface on PYC was prepared by creating parallel ridges via the combination of laser etching technology and surface fluorosilanization. Scanning electron microscopy (SEM) observation confirms that the gradient hydrophobic surface is composed of a bare PYC region and four regions of parallel ridges with varying distances. The gradient hydrophobic surface is stable in air, phosphate buffer solution (PBS), and flowing PBS. Additionally, the gradient hydrophobic surface on PYC shows spontaneous droplet motion and much lower flow resistance than bare PYC. Compared to bare PYC, the gradient hydrophobic surface on PYC exhibits better blood compatibility and anti-adhesion performance. The results presented in this paper confirm that creating a gradient hydrophobic surface is an effective way of achieving long-lasting anti-thrombosis property.

Conductive hydrogels have consistently attracted researchers' interests in the past few years. However, challenges still remain in the preparation of hydrogels with self-healing ability and underwater sensing capacity. In this work, we fabricate a novel fully-physically crosslinked nanocomposite hydrogel by incorporating gelatin dispersed carbon nanotubes (CNTs) into poly (sulfobetaine methacrylate) (PSBMA) network. The fully physically crosslinked PSBMA backbone and the nano reinforcement of CNTs endow hydrogel with fast self-healing ability (about 30 s) and good mechanical properties. Additionally, PSBMA/CNTs hydrogels exhibit high strain sensitivity (gauge factor up to 10.35) and pressure sensitivity (up to 0.256 kPa−1) and they can be fabricated as strain and pressure sensors to precisely monitor human movements. Moreover, the PSBMA/CNTs hydrogel sensor can detect human motions underwater owing to the anti-swelling feature. This work provides a feasible method to construct self-healing hydrogel sensors with strain and pressure sensing capacity and paves a way for underwater human motion sensors.

Multifunctional capsules have great applications in biomedical fields. In this study, novel polysaccharide-based nanocapsules were prepared via a layer-by-layer technique using silica as the templates. The shell was constructed based on the electrostatic interactions between pectin and chitosan. The pectin-chitosan nanocapsules ((Pec/Cs)3Pec) could keep good colloidal stability within 96h in PBS solution and 48h in BSA solution. Meanwhile, the nanocapsules exhibited a high drug loading and pH-sensitive release property for doxorubicin hydrochloride. Moreover, (Pec/Cs)3Pec nanocapsules had no cytotoxicity to both human hepatocellular carcinoma cells (HepG2 cells) and mouse fibroblast cells (L929 cells). More importantly, (Pec/Cs)3Pec nanocapsules could be more easily uptaken by HepG2 cells when compared with L929 cells. In vitro anticancer activity tests indicated the carriers could effectively kill HepG2 cells. Overall, (Pec/Cs)3Pec nanocapsules have great potential as a novel anticancer drug carrier as a result of their pH-sensitivity, good colloidal stability and anticancer activity.

The unique properties of bioactive glasses (BGs) make them promising for bone regeneration. Unfortunately, their brittleness greatly limits their clinical application. Combining BGs with polymers is an ideal solution such that their advantages (toughness of the polymers and bioactivity of BGs) can be combined. In this work, a novel nanocomposite biomaterial consisting of BG nanofibers with a diameter of only 31 nm and gelatin coating has been developed for bone regeneration. The BG nanofibrous scaffold was synthesized via a template-assisted sol-gel method by using natural three-dimensional (3D) bacterial cellulose as the template. The BG nanofibers were subsequently coated with gelatin followed by crosslinking with proanthocyanidin (PA) to yield the BG/gelatin nanocomposite scaffolds. Characterizations with scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), mercury intrusion porosimetry, nitrogen adsorption–desorption, and mechanical testing reveal that the as-obtained BG/gelatin scaffolds maintain the 3D interconnected porous nanofibrous structure of pristine BC, show tri-modal pore structure (20–60 μm, 1–2 μm, 3–32 nm), and exhibit improved mechanical strength over bare BG scaffold. Cell studies using primary osteoblasts demonstrate more favorable cell growth, higher alkaline phosphatase (ALP) activity, and more calcium deposition on the BG/gelatin scaffold than other nanocomposite scaffolds as well as bare BG scaffold, strongly indicating a coating thickness-dependent synergistic effect between BGs and gelatin. This novel type of BG/gelatin scaffold has great potential in applications of bone regeneration.

Three-dimensional (3D) nanofibrous scaffolds morphologically mimicking natural extracellular matrix show great potential in the application of tissue repair. Herein, we report a novel 3D nanofibrous silica (SiO 2 ) scaffold fabricated via a sacrificial template method. The sacrificed template used was 3D bacterial cellulose and the resultant silica nanofiber has a ultrasmall diameter of 21 nm. SEM, TEM, and AFM evidence the 3D porous nanofibrous structure and pore structure measurement confirms the existence of macro- and meso-pores in the as-prepared silica scaffold. Cell studies using osteoblast cells demonstrate excellent biocompatibility and high ALP activity. These results suggest that the 3D silica nanofibrous scaffold is a promising candidate for hard tissue engineering.

The lack of sufficient mechanical properties restricts the application of polysaccharide-based hydrogels in the field of biomedicine, especially load-bearing tissue repair. Nowadays, double network (DN) hydrogels have aroused great interest through special cooperation between two contrasting networks. Inspired by this idea, here, we devised a new strategy to prepare a pectin–Fe3+/polyacrylamide hybrid DN hydrogel using a simple two-step method. The introduction of Fe3+ ions into a pectin network to produce strong reversible ionic complexation, results in excellent toughness. Under optimal conditions, our hybrid DN hydrogels possessed tensile strength as high as 0.9 MPa, corresponding to a high strain of 1300%. Besides, our hybrid DN hydrogels also exhibited superb stiffness (elastic modulus ∼ 1.46 MPa), toughness (fracture energy ∼ 3785 J m−2), and water absorption capacity (85%). Loading–unloading tests showed that the internal fracture process of the hydrogels was continuous. Owing to the reversible structure of Fe3+–pectin complexation, the hybrid DN hydrogels also showed good fatigue resistance, notch-insensitivity and recoverability. This type of polysaccharide-based hydrogel has potential to broaden the application in the load-bearing tissue repair field.

Hydrogels derived from natural polymers have been extensively investigated in the biomedical field, while inherent brittleness and poor stability limit their applications. In this study, a tough pectin-Fe3+/poly (acrylamide-co-stearyl methacrylate) (P(AAm-co-SMA)) double physical crosslinking (DPC) network hydrogel is prepared using a three-step method. The first HPAAm network is formed via hydrophobic associations among the PSMA segment in P(AAm-co-SMA), and trivalent ions (Fe3+) crosslinked pectin network as the second network. Due to the reversibility of dual physical cross-linking structures, the pectin-Fe3+/HPAAm hydrogel exhibit excellent toughness (1.04–11.20 MJ m−3). In addition, the pectin-Fe3+/HPAAm DPC hydrogels have tunable mechanical properties (tensile strength: 0.97–1.61 MPa, elongation: 133–1346%, elastic modulus: 0.30–2.20 MPa) via adjusting the ratio of pectin network and HPAAm network. To explore their potential application in tissue engineering, ATDC5 chondrocytes were seeded on the prepared DPC hydrogels. Results suggest that the pectin-Fe3+/HPAAm DPC hydrogels can support the adhesion and proliferation of ATDC5, moreover, the ATDC5 cells can penetrate into the hydrogel. It is concluded that the prepared hydrogels exhibit potential application in the load-bearing tissue repair field.

Flexible electronic sensors based on conductive hydrogels have received extensive attention in the field of smart wearable electronics. However, the existing hydrogels usually cannot meet the necessary requirements due to their relatively narrow strain range, and low stability, especially at subzero temperatures. In this study, a xanthan gum-Fe3+/polyacrylamide-glycerol (XG-Fe3+/PAAm-Gl) organohydrogel was prepared via the polymerization in situ and solvent-exchange method. XG was initially used to prepare organohydrogels-based sensors with multiple interactions, including covalent cross-linking interaction, ionic coordination interaction and hydrogen bonds. The prepared organohydrogel possesses excellent mechanical properties, such as, ultrastretchability (~1769%) and high strength (~1.5 MPa). In addition, a water-glycerol binary solvent endows the organohydrogel with excellent long-term anti-drying and anti-freezing capabilities, and it can maintain excellent stretchability (>500%), good conductivity and transparency even at −40 °C. A simple biosensor was fabricated using the XG-Fe3+/PAAm-Gl organohydrogel and was used to monitor the detection of human physiological motions, showing remarkable sensitivity and a wide strain range (5% to 500% strain) under a broad range of temperatures (−40 °C to 25 °C). The XG-Fe3+/PAAm-Gl organohydrogel is expected to meet the requirements of flexible sensors for adaption to many complicated environments.

In this work, a novel starch-based zwitterionic copolymer, starch-graft-poly(sulfobetaine methacrylate) (ST-g-PSBMA), was synthesized via Atom Transfer Radical Polymerization. Starch, which formed the main chain, can be degraded completely in vivo, and the pendent segments of PSBMA endowed the copolymer with excellent protein resistance properties. This ST-g-PSBMA copolymer could self-assemble into a physical hydrogel in normal saline, and studies of the formation mechanism indicated that the generation of the physical hydrogel was driven by electrostatic interactions between PSBMA segments. The obtained hydrogels were subjected to detailed analysis by scanning electron microscopy, swelling ratio, protein resistance, and rheology tests. Toxicity and hemolysis analysis demonstrated that the ST-g-PSBMA hydrogels possess excellent biocompatibility and hemocompatibility. Moreover, the cytokine secretion assays (IL-6, TNF-α, and NO) confirmed that ST-g-PSBMA hydrogels had low potential to trigger the activation of macrophages and were suitable for in vivo biomedical applications. On the basis of these in vitro results, the ST-g-PSBMA hydrogels were implanted in SD rats. The tissue responses to hydrogel implantation and the hydrogel degradation in vivo were determined by histological analysis (Hematoxylin and eosin, Van Gieson, and Masson's Trichrome stains). The results presented in this study demonstrate that the physical cross-linking, starch-based zwitterionic hydrogels possess excellent protein resistance, low macrophage-activation properties, and good biocompatibility, and they are a promising candidate for an in vivo biomedical application platform.

In general, the design of a scaffold should imitate certain advantageous properties of native extracellular matrix (ECM) to operate as a temporary ECM for cells. From this perspective, a biomimetic scaffold was prepared using poly(vinyl alcohol) and carrageenan in which axially oriented pore structure can be formed through a facile unidirectional freeze-thaw method. We examined the feasibility of this oriented scaffold, which has better physicochemical properties than a non-oriented scaffold fabricated by the conventional method. The microenvironment of this oriented scaffold could imitate biochemical and physical cues of natural cartilage ECM for guiding spatial organization and proliferation of cells in vitro, indicating its potential in cartilage repair strategy. Furthermore, the biocompatibility of the scaffold in vivo was demonstrated in a subcutaneous rat model, which revealed uniform infiltration and survival of newly formed tissue into the oriented scaffold after 4 weeks with only a minimal inflammatory response being observed over the course of the experiments. These results together indicated that the present biomimetic scaffold with oriented microarchitecture could be a promising candidate for cartilage tissue engineering.

Over the last few decades, nanoparticles have been emerging as useful means to improve the therapeutic efficacy of drug delivery and medical diagnoses. However, the heterogeneity and complexity of blood as a medium is a fundamental problem; large amounts of protein can be adsorbed onto the surface of nanoparticles and cause their rapid clearance before reaching their target sites, resulting in the failure of drug delivery. To overcome this challenge, we present a rationally designed starch derivative (SB-ST-OC) with both a superhydrophilic moiety of zwitterionic sulfobetaine (SB) and a hydrophobic segment of octane (OC) as functional groups, which can self-assemble into "stealth" micelles (SSO micelles). The superhydrophilic SB kept the micelles stable against aggregation in complex media and imbued them with "stealth" properties, eventually extending their circulation time in blood. In stability and hemolysis tests the SSO micelles showed excellent protein resistance properties and hemocompatibility. Moreover, a phagocytosis test and cytokine secretion assay confirmed that the SSO micelles had less potential to trigger the activation of macrophages and were more suitable as a drug delivery candidate in vivo. On the basis of these results, doxorubicin (DOX), a hydrophobic drug, was used to investigate the potential application of this novel starch derivative in vivo. The results of the pharmacokinetic study showed that the values of the plasma area under the concentration curve (AUC) and elimination half-life (T1/2) of the SSO micelles were higher than those of micelles without SB modifications. In conclusion, the combination of excellent protein resistance, lower macrophage activation, and longer circulation time in vivo makes this synthesized novel starch derivative a promising candidate as a hydrophobic drug carrier for long-term circulation in vivo.

Three-dimensional (3D) cell encapsulation in hydrogel provides superb methods to investigate the biochemical cues in directing cellular fate and behaviors outside the organism, the primary step of which is to establish suitable "blank platform" to mimic and simplify native ECM microenvironment. In this study, zwitterionic starch-based "clickable" hydrogels were fabricated via a "copper- and light- free" Michael-type "thiol-ene" addition reaction between acylated-modified sulfobetaine-derived starch (SB-ST-A) and dithiol-functionalized poly(ethylene glycol) (PEG-SH). By incorporating antifouling SB-ST and PEG, the hydrogel system would be excellently protected from nontarget protein adsorption to act as a "blank platform". The hydrogels could rapidly gel under physiological conditions in less than 7 min. Dynamic rheology experiments suggested the stiffness of the hydrogel was close to the native tissues, and the mechanical properties as well as the gelation times and swelling behaviors could be easily tuned by varying the precursor proportions. The protein and cell adhesion assays demonstrated that the hydrogel surface could effectively resist nonspecific protein and cell adhesion. The degradation study in vitro confirmed that the hydrogel was biodegradable. A549 cells encapsulated in the hydrogel maintained high viability (up to 93%) and started to proliferate in number and extend in morphology after 2 days' culture. These results indicated the hydrogel presented here could be a potential candidate as "blank platform" for 3D cell encapsulation and biochemical cues induced cellular behavior investigation in vitro.

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...

With the aim to explore a membrane system with appropriate degradation rate and excellent cell-occlusiveness for guided tissue regeneration (GTR), a series of poly(D, L-lactic acid) (PDLLA)/poly(D, L-lactic-co-glycolic acid) (PLGA) (100/0, 70/30, 50/50, 30/70, 0/100, w/w) composite membranes were fabricated via electrospinning. The fabricated membranes were evaluated by morphological characterization, water contact angle measurement and tensile test. In vitro degradation was characterized in terms of the weight loss and the morphological change. Moreover, in vitro cytologic research revealed that PDLLA/PLGA composite membranes could efficiently inhibit the infiltration of 293 T cells. Finally, subcutaneous implant test on SD rat in vivo showed that PDLLA/PLGA (70/30, 50/50) composite membranes could function well as a physical barrier to prevent cellular infiltration within 13 weeks. These results suggested that electrospun PDLLA/PLGA (50/50) composite membranes could serve as a promising barrier membrane for guided tissue regeneration due to suitable biodegradability, preferable mechanical properties and excellent cellular shielding effects.

To improve the circulation stability of polyamidoamine (PAMAM) based drug delivery systems in complex biological microenvironments, a series of generation-3.0 PAMAM-graft-poly[3-dimethyl(methacryloyloxyethyl)ammonium propanesulfonate] (PAMAM3.0-g-PDMAPS) copolymers are synthesized via atom transfer radical polymerization. The zwitterionic PDMAPS segments serve as a shell to stabilize the unimolecular micelles, whereas the PAMAM3.0 dendrimers constitute a hydrophobic core. The sizes of the PAMAM3.0-g-PDMAPS unimolecular micelles range from 6.5 to 8.5 nm. Furthermore, PAMAM3.0-g-PDMAPS can keep the micelle-like structure when it is diluted by large volumes of fluids. More importantly, the PDMAPS shell layer can suppress non-specific protein adsorption on the surface of the micelles. The excellent stability to dilution and anti-biofouling are beneficial for prolonged circulation time in a complex biological microenvironment. In addition, anticancer doxorubicin (DOX) can be encapsulated both in the PAMAM3.0 core via hydrophobic interactions and the PDMAPS shell layer via hydrogen bonds. Drug release studies confirm the pH-responsive nature of PMAMA3.0-g-PDMAPS micelles by achieving 65.23% DOX release at pH 5.1 as compared to 16.38% at pH 7.4. Based on these results, the cytotoxicity and anticancer effects against human hepatocellular carcinoma cells (HepG2) of the PAMAM3.0-g-PDMAPS system loaded with DOX are investigated. The results suggest that the PDMAPS shell layer can significantly decrease the cytotoxicity via decreasing/shielding of the positive charges on the PAMAM dendrimers. After internalization by HepG2 cells, DOX is released from the micelles to the nucleus and further inhibits the proliferation of HepG2. Therefore, these PAMAM3.0-g-PDMAPS unimolecular micelles are a potential platform for anticancer drug delivery.

Promising three-dimensional porous scaffolds for cardiac tissue engineering should both function as conductive substrates to adapt to the electroactive nature of the myocardium and modulate the excessive reactive oxygen species (ROS) microenvironment after myocardial infarction. In this study, glutathione (GSH) is grafted to the terminal carboxyl groups of carboxyl-capped aniline pentamer (CCAP), forming AP-GSH that is then introduced into gelatin (Gel) scaffold to create a composite scaffold combining both conductivity and antioxidant activity. Results suggest that the Gel/AP-GSH composite scaffolds exhibit high porosity, homogeneous pore structure and high swelling behaviors. The conductivity of the Gel/AP-GSH scaffold ranges from 3.4 × 10−5 S/cm to 1 × 10−4 S/cm, which is similar to the native myocardium. The introduction of AP-GSH can remove intracellular ROS and decrease the oxidative stress damage in brown adipose-derived stem cells (BADSCs), further improving the adhesion and proliferation of BADSCs under the ROS microenvironment. Moreover, BADSCs seeded in the Gel/AP-GSH composite scaffold maintain high cardiomyogenic differentiation even under the ROS microenvironment. These results demonstrate that Gel/AP-GSH composite scaffolds can be used as a promising candidate for cardiac tissue engineering.

The preparation and biological applications of graphene quantum dots (GQDs) have attracted much attention. Here, a one-step hydrothermal method for synthesizing nitrogen-doped GQDs (N-GQDs) using graphene oxide (GO), ethylenediamine and hydrogen peroxide, simultaneously achieved oxidative cleavage and chemical reduction of GO. The average size of the synthesized N-GQDs was about 1.84 ± 0.28 nm and their quantum yield of the N-GQDs reached about 0.46, which was higher than that of other GQDs synthesized by top-down methods. The cytotoxicity of these N-GQDs on Hela cells was evaluated using a cell counting Kit-8 assay. The effects of N-GQDs on different cell lines and fluorescence imaging were also observed by confocal laser scanning microscopy. The results suggested that these N-GQDs penetrated into cells by endocytosis and were promising fluorescent probes for biological imaging.

Hydrogel-based sensors have attracted enormous interest due to their broad applications in wearable devices. However, existing hydrogel-based sensors cannot integrate satisfying mechanical performances with excellent conductivity to meet the requirements for practical application. Herein, an ionically conductive hydrogel with high strength, fast self-recovery, and low residual strain is constructed through a facile soaking strategy. The proposed ionically conductive double network hydrogel is achieved by combining chemically crosslinked polyacrylamide and physically crosslinked gelatin network followed by sodium citrate solution immersing. The obtained hydrogel has a tensile strength of 1.66 MPa and an elongation of 849%. The ionically conductive hydrogels can be utilized as both strain and pressure sensors with high sensitivity. Moreover, they can be used as ionic skin to monitor various human movements precisely, demonstrating their promising potential in wearable devices and flexible electronics.

Flexible strain sensors have attracted much attention for their applications in human–machine interactions and personal health monitoring. However, fabricating strain sensors based on hydrogels with high stretchability and tensile strength simultaneously still remains a challenge due to the intrinsic brittleness of conventional hydrogel. In this study, a conductive nanocomposite hydrogel comprised of oxidized multi-walled carbon nanotubes (oxCNTs) and polyacrylamide (PAAm) is developed. In the PAAm-oxCNTs hydrogel, the oxCNTs is uniformly dispersed in the presence of gelatin via the hydrogen bonding. The chemical cross-linked PAAm is the main network structure of the hydrogel. Besides, the physical interactions between the oxCNTs, gelatin and PAAm chains contributed to the high performance of the hydrogel as well. The obtained hydrogel integrates satisfactory stretchability (sensing range >700%), high tensile strength (0.71 MPa), good recovery efficiency (90%) and superior sensing abilities. Furthermore, the PAAm-oxCNTs hydrogel exhibits excellent strain sensitivity (Gauge factor = 3.39 at 250–700% strain), fast response (300 ms) and superb durability (over 300 cycles) due to the conductive pathways formed by oxCNTs. The prepared strain sensors could detect both large and subtle human movements (e.g., elbow rotation, wrist bending knee bending, swallowing and phonation) via stable and repeatable electrical signals, indicating their potential applications in human–machine interactions and personal health monitoring.

Uniform dispersion of two-dimensional (2D) graphene materials in polymer matrices remains challenging. In this work, a novel layer-by-layer assembly strategy was developed to prepare a sophisticated nanostructure with highly dispersed 2D graphene oxide in a three-dimensional matrix consisting of one-dimensional bacterial cellulose (BC) nanofibers. This method is a breakthrough, with respect to the conventional static culture method for BC that involves multiple in situ layer-by-layer assembly steps at the interface between previously grown BC and the culture medium. In the as-prepared BC/GO nanocomposites, the GO nanosheets are mechanically bundled and chemically bonded with BC nanofibers via hydrogen bonding, forming an intriguing nanostructure. The sophisticated nanostructure of the BC/GO leads to greatly enhanced mechanical properties compared to those of bare BC. This strategy is versatile, facile, scalable, and can be promising for the development of high-performance BC-based nanocomposite hydrogels.

Multifunctional drug carriers have great applications in biomedical field. In this study, we introduced both polydopamine (PDA) and zwitterionic polymer of poly(3-(3-methacrylamidopropyl-(dimethyl)-ammonio)propane-1-sulfonate) (PSPP) onto the surface of mesoporous silica nanoparticles (MSNs) to develop a novel nanoparticle (MSNs@PDA-PSPP), which was employed as a new kind of drug carrier for the delivery of doxorubicin (DOX). The PDA coating, as a gatekeeper, could endow the drug carrier with pH-sensitive drug release performance. The outermost PSPP layer would make the drug carrier possess protein resistance performance. The chemical structure and properties were characterized by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermogravimetric analysis (TGA). MSNs@PDA-PSPP could keep good colloidal stability within 72 h in phosphate buffered saline (PBS) and protein solutions. Meanwhile, MSNs@PDA-PSPP exhibited a high drug loading for DOX. In vitro drug release experiments suggested MSNs-DOX@PDA-PSPP exhibited pH-dependent drug release behaviors. Besides, MSNs@PDA-PSPP had no cytotoxicity to human hepatocellular carcinoma cells (HepG2 cells) even at a concentration of 125 µg/mL. More importantly, cellular uptake and in vitro anticancer activity tests suggested that MSNs-DOX@PDA-PSPP could be taken up by HepG2 cells and DOX could be successfully released and delivered into the cell nuclei. Taken together, MSNs@PDA-PSPP have great potential in the biomedical field.

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.

Stem cell implantation strategy has exhibited potential to treat the myocardial infarction (MI), however, the low retention and survival limit their applications due to the reactive oxygen species (ROS) microenvironment after MI. In this study, the fullerenol nanoparticles are introduced into alginate hydrogel to create an injectable cell delivery vehicle with antioxidant activity. Results suggest that the prepared hydrogels exhibit excellent injectable and mechanical strength. In addition, the fullerenol/alginate hydrogel can effectively scavenge the superoxide anion and hydroxyl radicals. Based on these results, the biological behaviors of brown adipose-derived stem cells (BADSCs) seeded in fullerenol/alginate hydrogel were investigated in the presence of H2O2. Results suggest that the fullerenol/alginate hydrogels have no cytotoxicity effects on BADSCs. Moreover, they can suppress the oxidative stress damage of BADSCs and improve their survival capacity under ROS microenvironment via activating the ERK...

Prediction of the diffusion coefficient of solute, especially bioactive molecules, in hydrogel is significant in the biomedical field. Considering the randomness of solute movement in a hydrogel network, a physical diffusion RMP-1 model based on obstruction theory was established in this study. The physical properties of the solute and the polymer chain and their interactions were introduced into this model. Furthermore, models RMP-2 and RMP-3 were established to understand and predict the diffusion behaviors of proteins in hydrogel. In addition, zwitterionic poly(sulfobetaine methacrylate) (PSBMA) hydrogels with wide range and fine adjustable mesh sizes were prepared and used as efficient experimental platforms for model validation. The Flory characteristic ratios, Flory-Huggins parameter, mesh size, and polymer chain radii of PSBMA hydrogels were determined. The diffusion coefficients of the proteins (bovine serum albumin, immunoglobulin G, and lysozyme) in PSBMA hydrogels were studied by the fluorescence recovery after photobleaching technique. The measured diffusion coefficients were compared with the predictions of obstruction models, and it was found that our model presented an excellent predictive ability. Furthermore, the assessment of our model revealed that protein diffusion in PSBMA hydrogel would be affected by the physical properties of the protein and the PSBMA network. It was also confirmed that the diffusion behaviors of protein in zwitterionic hydrogels can be adjusted by changing the cross-linking density of the hydrogel and the ionic strength of the swelling medium. Our model is expected to possess accurate predictive ability for the diffusion coefficient of solute in hydrogel, which will be widely used in the biomedical field.

Peritoneal adhesion is very common after abdominal and pelvic surgery, which leads to a variety of severe complications. Although numerous pharmacological treatments and barrier-based devices have been investigated to minimize or prevent postoperative adhesion, the clinical efficacy is not very encouraging. In this work, a biodegradable and thermoreversible galactose modified xyloglucan (mXG) hydrogel was developed and the efficacy of mXG hydrogel in preventing postoperative peritoneal adhesion was investigated. The 4% (w/v) mXG solution was a free flowing sol at low temperature, but could rapidly convert into a physical hydrogel at body temperature without any extra additives or chemical reactions. In vitro cell tests showed that mXG hydrogel was non-toxic and could effectively resist the adhesion of fibroblasts. Moreover, in vitro and in vivo degradation experiments exhibited that mXG hydrogel was degradable and biocompatible. Finally, the rat model of sidewall defect-cecum abrasion was employed to evaluate the anti-adhesion efficacy of the mXG hydrogel. The results demonstrated that mXG hydrogel could effectively prevent postoperative peritoneal adhesion without side effects. The combination of suitable gel temperature, appropriate biodegradation period, and excellent postoperative anti-adhesion efficacy make mXG hydrogel a promising candidate for the prevention of postsurgical peritoneal adhesion. Statement of significance Despite numerous drugs or barrier-based devices have been developed to prevent postoperative adhesion, few solutions have proven to be uniformly effective in subsequent clinical trials. In the present study, we developed a biodegradable and thermoreversible galactose modified xyloglucan (mXG) hydrogel by green enzymatic reaction without using any organic reagents. The developed physical mXG hydrogel not only showed excellent injectability, appropriate gelation time and temperature, but also exhibited excellent biocompatibility and biodegradability both in vitro and in vivo. In addition, mXG hydrogel was easy to handle and could effectively prevent postoperative adhesion without side effects in a rat model of sidewall defect-bowel abrasion. Our study provide a safe and effective postoperative anti-adhesion material which may have potential applications in clinical practice.