Highly Tough, Stretchable, Self-Adhesive and Strain-Sensitive DNA-Inspired Hydrogels for Monitoring Human Motion.

Hydrogels used as strain sensors often rely on splicing tapes to attach them to surfaces, which causes much inconvenience. Therefore, to develop strain sensor hydrogels that possess both good mechanical properties and self-adhesion is still a great challenge. Inspired by the multiple hydrogen bonding interactions of nucleobases in DNA, we designed and synthesized a series of hydrogels PAAm-GO-Aba/Tba/Aba+Tba comprising polyacrylamide (PAAm), graphene oxide (GO), acrylated adenine and thymine (Aba and Tba). The introduction of nucleobases helps hydrogels to adhere to various substrates through multiple hydrogen-bonding interactions. It has also been found that the adhesive strength of hydrogels with nucleobases for hogskin increased to 2.5 times that of those without nucleobases. Meanwhile, these hydrogels exhibited good dynamic mechanical and self-recovery properties. They can be directly attached to human skin as strain sensors to monitor the motions of finger, wrist, and elbow. Electrical tests indicate that they give precise real-time monitoring data and exhibit good strain sensitivity and electrical stability. This work provides a promising basis from which to explore the fabrication of tough, self-adhesive, and strain-sensitive hydrogels as strain sensors for applications in wearable devices and healthcare monitoring.

DNA-Inspired Adhesive Hydrogels Based on the Biodegradable Polyphosphoesters Tackified by a Nucleobase.

Since adhesive hydrogels showed wide applications ranging from wearable soft materials to medical sealants, more and more attention has been paid toward the exploration of novel adhesive hydrogels. However, the difficulty in removing the residue caused by the excessive adhesive strength and sluggish degradation or nondegradation behaviors of the adhesive has always been challenging. Inspired by the multiple complementary hydrogen bond interactions in DNA, the bioinspired nucleobase (A, T, and U) monomers were first synthesized and used to tackify polyphosphoester hydrogels. The multiple hydrogen bonds and hydrophobic interactions between purine rings and pyrimidine functionalities endowed the hydrogels with excellent controllable adhesive properties. Besides this, it has been found that these nucleobase-tackified hydrogels could be easily peeled off without leaving any residue and could be totally degraded under alkaline conditions due to hydrolysis of phosphoester chains. At the same time, they also exhibited controllable biodegradation to different extents under the different pH conditions. The excellent adhesive performance, controllable biodegradation, and excellent biocompatibility showed by this nucleobase-tackified polyphosphoester adhesive hydrogel demonstrated its great potential in wound dressing, as a tissue sealant, and so on.

Tailor-Made pH-Responsive Poly(choline phosphate) Prodrug as a Drug Delivery System for Rapid Cellular Internalization.

Rapid cellular uptake and efficient drug release in tumor cells are two of the major challenges for cancer therapy. Herein, we designed and synthesized a novel pH-responsive polymer-drug conjugate system poly(2-(methacryloyloxy)ethyl choline phosphate)-b-poly(2-methoxy-2-oxoethyl methacrylate-hydrazide-doxorubicin) (PCP-Dox) to overcome these two challenges simultaneously. It has been proved that PCP-Dox can be easily and rapidly internalized by various cancer cells due to the strong interaction between multivalent choline phosphate (CP) groups and cell membranes. Furthermore, Dox, linked to the polymer carrier via acid-labile hydrazone bond, can be released from carriers due to the increased acidity in lysosome/endosome (pH 5.0-5.5) after the polymer prodrug was internalized into the cancer cells. The cell viability assay demonstrated that this novel polymer prodrug has shown enhanced cytotoxicity in various cancer cells, indicating its great potential as a new drug delivery system for cancer therapy.

Evaluating the hypolipidemic effect of garlic essential oil encapsulated in a novel double-layer delivery system.

The limited application of garlic essential oil (GEO) is attributed to its pungent taste, poor water solubility and low bioavailability. Liposomes are nontoxic, biodegradable and biocompatible, and ß-cyclodextrin can inhibit undesirable odors and improve the stability and bioavailability. Thus a promising dual-layer GEO ß-cyclodextrin inclusion compound liposome (GEO-DCL) delivery system with both advantages was designed and prepared in this study. Experimental results indicated that the encapsulation efficiency of GEO-DCLs was 5% higher than that of GEO liposomes (GEO-CLs), reaching more than 88%. In vitro release experiment showed that the release rate of GEO in GEO-DCLs was 40% lower than that of GEO-CLs after incubation in gastric juice for 6-h, indicating that the stability of GEO-DCLs was better than GEO-CLs. Evaluation of the effects of GEO-DCLs on lowering blood lipid levels in hypercholesterolemia mice. GEO-DCLs could reduce the weight and fat deposition in hypercholesterolemia mice. Inhibiting the increase of TC, LDL-C, and decrease of HDL-C in mice. The degree of liver injury was decreased, the number of round lipid droplets in liver cytoplasm was reduced, and the growth of fat cells was inhibited. The lipid-lowering effects of GEO-DCLs were dose-dependent. GEO-DCL can improve the bioavailability of GEO and improve dyslipidemia. Based on GEO's efficacy in lowering blood lipids, this study developed a kind of GEO-DCL compound pomegranate juice beverage with good taste, miscibility and double effect of reducing blood lipids. This study lays a foundation for the application of GEO in the field of functional food.

Nanolignin-containing cellulose nanofibrils (LCNF)-enabled multifunctional ratiometric fluorescent bio-nanocomposite films for food freshness monitoring.

Herein, the nanolignin-containing cellulose nanofibrils (LCNF)-enabled ratiometric fluorescent bio-nanocomposite film is developed. Interestingly, the inclusion of LCNF in the cellulose-based film enhances the detecting performance of food freshness, such as high sensitivity to biogenic amines (BAs) (limit of detection (LOD) of up to 1.83 ppm) and ultrahigh discernible fluorescence color difference (ΔE = 113.11). The underlying mechanisms are the fluorescence resonance energy transfer (FRET), π - π interaction, and cation - π interaction between LCNF and fluorescein isothiocyanate (FITC), as well as the increased hydrophobicity due to lignin, which increases the interactions of amines with FITC. Its color stability (up to 28 days) and mechanical property (49.4 Mpa) are simultaneously improved. Furthermore, a smartphone based detecting platform is developed to achieve access to food safety. This work presents a novel technology, which can have a great potential in the field of food packaging and safety.

[TG-fTIR study of the thermal-conversion properties of holo-cellulose derived from woody biomass].

Thermal-conversion properties of cellulose, hemi-cellulose and holo-cellulose derived from woody biomass were studied using TG-FTIR, and also compared to those of avicel cellulose and xylan. 3-D diffusion model was applied to calculate the kinetic parameters of thermal-conversion reaction of biomass materials, such as the activation energy, pre-exponential factors, etc, which showed good regression results. With the analysis of three-dimensional IR spectra of gas products, featured peaks of HzO, CO, CO2, CH4, and oxygenates were obviously observed where showing up with the maximum weight-loss rate in DTG curves. The possible forming routes of major gaseous products were analyzed and discussed. The order of releasing amounts for gaseous productions was approximately as CO2 > H2O > CO CH4. Based on the comprehensive understanding and comparative analysis of the whole results, it is concluded that the thermal conversion process of holo-cellulose was the result of interaction between cellulose and hemi-cellulose under the dominant role of cellulose.

Cellulose microspheres enhanced polyvinyl alcohol separator for high-performance lithium-ion batteries.

Separators typically play an important role in enhancing the electrochemical performance of lithium-ion batteries (LIBs), while the preparation of separators suffers good electrochemical performance and high stability. In this study, regenerated porous cellulose microspheres (RCM) were innovatively fabricated and the biodegradable RCM/Polyvinyl alcohol (PVA) separators were successfully prepared through simple mixing and solvent substitution. Interestingly, the RCM with rich carboxylic groups, not only function as nanofillers that increases the strength properties of the three-dimensional porous network, but also enhances Li+ transfer (due to the COO- and Li+ interactions), resulting in outstanding Li+ transference number (0.54) of the RCM/PVA separator. In addition, the RCM/PVA separator shows excellent thermal stability and high liquid absorption rate (481.25 %). The LiFePO4/3 % RCM-HCl/PVA/Li cell displayed a high discharge capacity of 152.6 mAh·g-1 after 200 cycles at 1C. This work provides a new light on the fabrication of biodegradable separators for LIBs via a novel and cost-effective strategy.

Piezoelectric PDMS/AlN Film for Osteogenesis in Vitro.

Bone defect and nonunion are complex diseases which are difficult to treat due to insufficient bone regeneration. Electrical stimulation has attracted attention as a promising strategy to induce and enhance bone regeneration. Self-powered and biocompatible materials have been widely explored and used in biomedical devices, owing to their ability to produce electrical stimulation without an external power source. We aimed to prepare a piezoelectric polydimethylsiloxane (PDMS)/aluminum nitride (AlN) film with excellent biocompatibility and osteoconductive ability for the growth of murine calvarial preosteoblast MC3T3-E1 cells. By applying vibration to stimulate body movement, the PDMS/AlN film demonstrated a current density of 2-6 µA cm-2, and the generated continuous alternating current (AC) effectively promoted MC3T3-E1 cell growth, viability, and osteoblastic related gene expression (genes runt-related transcription factor 2 [RUNX2], osteocalcin [OCN], alkaline phosphatase [ALP]) and exhibited higher mineralization. Compared to blank plates and nonvibrated PDMS/AlN films, the vibrated PDMS/AlN film showed rapid and superior osteogenic differentiation. The design of the biocompatible and flexible piezoelectric PDMS/AlN film overcame the poor processability, brittleness, and instability of electrical stimulation of traditional electroactive materials, demonstrating great potential in the application of electrical stimulation for bone tissue engineering.

Choline phosphate lipid as an intra-crosslinker in liposomes for drug and antibody delivery under guard.

Liposomes are used to deliver therapeutics in vivo because of their good biocompatibility, efficient delivery, and ability to protect the therapeutics from degradation. However, the instability of liposomes will cause the therapeutics to lose protection and become ineffective. To deliver therapeutics to the target under guard, we synthesized and used a bio-membrane mimetic choline phosphate lipid (CP-lip) to intra-crosslink liposomes to highly improve their stability. We found that when the ratio of PC-lip to CP-lip is 1 : 2, the intra-crosslinked liposome (PC-CP-lipo) showed higher stability, better biocompatibility and improved anti-protein adsorption than other common liposomes. We used doxorubicin (Dox) loaded PC-CP-lipo to treat melanoma and the tumor inhibition ratio could reach 86.3%. After the combined Dox@PC-CP-lipo treatment with PD-L1 antibody to block the immune checkpoints, the tumor suppression rate could reach 94.4%, and 60% of the mice did not suffer from tumor rechallenge. The method of using a CP-lip to intra-crosslink liposomes is applicable to all liposomes, solving the key problem of liposome disintegration, thus enhancing the protection of drugs and antibodies by liposomes in vivo.

A highly stable electrode with low electrode-skin impedance for wearable brain-computer interface.

To date, brain-computer interfaces (BCIs) have proved to play a key role in many medical applications, for example, the rehabilitation of stroke patients. For post-stroke rehabilitation, the BCIs require the EEG electrodes to precisely translate the brain signals of patients into intended movements of the paralyzed limb for months. However, the gold standard silver/silver-chloride electrodes cannot satisfy the requirements for long-term stability and preparation-free recording capability in wearable EEG devices, thus limiting the versatility of EEG in wearable BCI applications over time outside the rehabilitation center. Here, we design a long-term stable and low electrode-skin interfacial impedance conductive polymer-hydrogel EEG electrode that maintains a lower impedance value than gel-based electrodes for 29 days. With this technology, EEG-based long-term and wearable BCIs could be realized in the near future. To demonstrate this, our designed electrode is applied for a wireless single-channel EEG device that detects changes in alpha rhythms in eye-open/eye-close conditions. In addition, we validate that the designed electrodes could capture oscillatory rhythms in motor imagery protocols as well as low-frequency time-locked event-related potentials from healthy subjects, with similar or better performance than gel-based electrodes. Finally, we demonstrate the use of the designed electrode in online BCI-based functional electrical stimulation, which could be used for post-stroke rehabilitation.

Aza-crown ether locked on polyethyleneimine: solving the contradiction between transfection efficiency and safety during in vivo gene delivery.

We proposed a method using an aza-crown ether derivative to lock a hyperbranched polyethyleneimine, which endows the PEI25k with tumor targeting ability, anti-serum ability and extended circulation in the blood meanwhile retaining the high gene complexation and high transfection efficiency. The method we proposed here simultaneously endows cationic materials with high transfection efficiency and high safety, which greatly pushed the cationic materials to be applied in in vivo gene delivery.

Enantioselective Synthesis and Antifungal Activity of C18 Polyacetylenes.

Fungal pathogens cause serious crop diseases and decrease crop yields and quality. Polyacetylene alcohols are plant secondary metabolites and bioactive against various pathogenic fungi. They are, however, difficult to synthesize. In the present study, an efficient and highly enantioselective method (>98% ee) was established and employed to achieve the synthesis of the natural C18 polyacetylenes (S,E)-octadeca-1,9-dien-4,6-diyn-3-ol 1, (3R,10R,E)-octadeca-1,8-dien-4,6-diyne-3,10-diol 2, and their analogs. The title compounds were structurally characterized and biologically evaluated for fungicidal activities. The compounds exhibited high potencies against eight pathogenic fungal species tested, such as Colletotrichum gloeosporioiles, Bipolaris sorokiniana, Fusarium graminearum, and Fusarium pseudograminearum, with half-maximum effective concentrations ranging from 8 to 425 µg/mL, being similar to those of the fungicide thiophanate-methyl (3-408 µg/mL). These compounds are potential natural fungicides and fungicide lead candidates for further structural and property improvements.

Formate-assisted analytical pyrolysis of kraft lignin to phenols.

The effect of sodium formate (SF), calcium formate (CF) and nickel formate (NF) as additives on analytical pyrolysis performance of kraft lignin was conducted. The results showed that these formates promoted the releasing of volatiles, leading to the rapid degradation of kraft lignin. High relative content of monophenols (53.77%), especially of guaiacol (23.65%), were achieved from the pyrolysis of pure lignin. The relative content of guaiacol was dramatically decreased after the adding of formates in kraft lignin. The relative content of polyphenols such as 3-methylcatechol and 4-methylcatechol reached to 16.97%, 16.23% and 21.95% with the formates of SF, CF and NF, respectively. The NF showed the highest selectivity of polyphenols and hydrocarbons. The increase of polyphenols and hydrocarbons from NF was the synergetic effect of the hydrogen radical reaction from the formic functional groups under the catalysis of Ni and/or NiO produced from the NF pyrolysis process.

Carbohydrates-rich corncobs supported metal-organic frameworks as versatile biosorbents for dye removal and microbial inactivation.

In this work, biodegradable cellulose-based biosorbents (MOFs/OCBs) with dual function of dye removal and microbial inactivation were fabricated by in situ anchoring metal-organic frameworks (MOFs) on the TEMPO oxidized corncobs (OCBs). Results showed that delignification and oxidation can develop the OCBs with more cellulose content, carboxyl groups and specific surface area, thus facilitating the deposition of MOFs. The porous and carbohydrate-rich OCBs can serve as supports and stabilizers for MOFs, allowing for enhanced stability and recyclability of MOFs powders. The MOFs, namely HKUST-1 and ZIF-8, can endow the OCBs multiple functions of good adsorption capacity to methyl orange (from 8% of OCBs to 55% of HKUST-1/OCBs and 84% of ZIF-8/OCBs) and excellent antibacterial activity (from 0 of OCBs to 90.2% of HKUST-1/OCBs and 44.8% of ZIF-8/OCBs). Such a concept may offer a new pathway for preparing economical and efficient biosorbents for environmental remedy purposes.

Bioreducible Polymer Nanocarrier Based on Multivalent Choline Phosphate for Enhanced Cellular Uptake and Intracellular Delivery of Doxorubicin.

Limited cellular uptake and inefficient intracellular drug release severely hamper the landscape of polymer drug nanocarriers in cancer chemotherapy. Herein, to address these urgent challenges in tumor treatment simultaneously, we integrated the multivalent choline phosphate (CP) and bioreducible linker into a single polymer chain, designed and synthesized a neoteric bioreducible polymer nanocarrier. The excellent hydrophility of these zwitterionic CP groups endowed high drug loading content and drug loading efficiency of doxorubicin to this drug delivery system (∼22.1 wt %, ∼95.9%). Meanwhile, we found that the multivalent choline phosphate can effectively enhance the internalization efficiency of this drug-loaded nanocarrier over few seconds, and the degree of improvement depended on the CP density in a single polymer chain. In addition, after these nanocarriers entered into the tumor cells, the accelerated cleavage of bioreducible linker made it possible for more cargo escape from the delivery system to cytoplasm to exert their cytostatic effects more efficiently. The enhanced therapeutic efficacy in various cell lines indicated the great potential of this system in anticancer drug delivery applications.

Adding nickel formate in alkali lignin to increase contents of alkylphenols and aromatics during fast pyrolysis.

The composition of pyrolysis vapors obtained from alkali lignin pyrolysis with the additive of nickel formate was examined using the pyrolysis gas chromatography-mass spectrometry (Py-GC/MS). Characterization of bio-chars was performed using X-ray diffraction (XRD). Results showed that the nickel formate significantly increased liquid yield, simplified the types of alkali lignin pyrolysis products and increased individual component contents. The additive of nickel formate increased contents of alkylphenols and aromatics from alkali lignin pyrolysis. With an increase in temperature, a greater amount of the relative contents can be achieved. The nickel formate was thermally decomposed to form hydrogen, resulting in hydrodeoxygenation of alkali lignin during pyrolysis. It was also found that Ni is in favor of producing alkylphenols. The analysis based on the experimental result provided evidences used to propose reaction mechanism for pyrolysis of nickel formate-assisted alkali lignin.

Quality improvement of pyrolysis oil from waste rubber by adding sawdust.

This work was aimed at improving the pyrolysis oil quality of waste rubber by adding larch sawdust. Using a 1 kg/h stainless pyrolysis reactor, the contents of sawdust in rubber were gradually increased from 0%, 50%, 100% and 200% (wt%) during the pyrolysis process. Using a thermo-gravimetric (TG) analyzer coupled with Fourier transform infrared (FTIR) analysis of evolving products (TG-FTIR), the weight loss characteristics of the heat under different mixtures of sawdust/rubber were observed. Using the pyrolysis-gas chromatography (GC)-mass spectrometry (Py-GC/MS), the vapors from the pyrolysis processes were collected and the compositions of the vapors were examined. During the pyrolysis process, the recovery of the pyrolysis gas and its composition were measured in-situ at a reaction temperature of 450 °C and a retaining time of 1.2s. The results indicated that the efficiency of pyrolysis was increased and the residual carbon was reduced as the percentage of sawdust increased. The adding of sawdust significantly improved the pyrolysis oil quality by reducing the polycyclic aromatic hydrocarbons (PAHs) and nitrogen and sulfur compounds contents, resulting in an improvement in the combustion efficiency of the pyrolysis oil.

[Preparation of silk fibroin-chitosan scaffolds and their properties].

OBJECTIVE: To prepare the silk fibroin (SF)-chitosan (CS) scaffolds by adjusting the mass ratio between CS and SF, and test and compare the properties of the scaffolds at different mass ratios. METHODS: According to the mass ratios of 6:4 (group A), 6:8 (group B), and 6:16 (group C) between SF and CS, CS-SF scaffolds were prepared by freeze-drying method, respectively. The material properties, porosity, the dissolubility in hot water, the modulus elasticity, and the water absorption expansion rate were measured; the aperture size and shape of scaffolds were observed by scanning electron microscope (SEM). Density gradient centrifugation method was used to isolate the bone marrow mesenchymal stell cells (BMSCs) of 4-week-old male Sprague Dawley rats. The BMSCs at passage 3 were seeded onto 3 scaffolds respectively, and then the proliferation of cells on the scaffolds was detected by MTS method. RESULTS: The results of fourier transform infrared spectroscopy proved that with the increased content of CS, the absorption peak of random coil/alpha helix structure (1 654 cm(-1) and 1540 cm(-1)) constantly decreased, but the absorption peak of corresponding to beta-fold structure (1628 cm(-1) and 1516 cm(-1)) increased. The porosity was 87.36% +/- 2.15% in group A, 77.82% +/- 1.37% in group B, and 72.22% +/- 1.37% in group C; the porosity of group A was significantly higher than that of groups B and C (P < 0.05), and the porosity of group B was significantly higher than that of group C (P < 0.05). The dissolubility in hot water was 0 in groups A and B, and was 3.12% +/- 1.26% in group C. The scaffolds had good viscoelasticity in 3 groups; the modulus elasticity of 3 groups were consistent with the range of normal articular cartilage (4-15 kPa); no significant difference was found among 3 groups (F=5.523, P=0.054). The water absorption expansion rate was 1 528.52% +/- 194.63% in group A, 1 078.22% +/- 100.52% in group B, and 1320.05% +/- 179.97% in group C; the rate of group A was significantly higher than that of group B (P=0.05), but there was no significant difference between groups A and C and between groups B and C (P > 0.05). SEM results showed the aperture size of group A was between 50-250 microm, with good connectivity of pores; however, groups B and C had structure disturbance, with non-uniform aperture size and poor connectivity of pores. The growth curve results showed the number of living cells of group A was significantly higher than that of groups B and C at 1, 3, 5, and 7 days (P < 0.05); and there were significant differences between groups B and C at 3, 5, and 7 days (P < 0.05). CONCLUSION: The CS-SF scaffold at a mass ratio of 6:4 is applicable for cartilage tissue engineering.

[Preliminary study on chitosan/HAP bilayered scaffold].

OBJECTIVE: To study repair of osteochondral defects by using composite of autologous BMSCs and chitosan/HAP (CS/HAP) bilayered scaffold in rabbits and its feasibility as osteochondral tissue engineering scaffolds. METHODS: CS/HAP bilayered scaffolds were produced with CS and HAP using a lyophilization and sintering method. The pore size of the scaffold was observed by scanning electron microscopy (SEM). Anhydrous ethanol substitution method determined its porosity. BMSCs were isolated from bone marrow and cultured by general bone marrow methods. Both CD44 and CD45 on the BMSCs surface were detected with immunocytochemistry to identify BMSCs. Cell-scaffold complex was made with BMSCs as seed cells and CS/HAP bilayered scaffold as carrier by fibrin glue planting technique. The distribution of BMSCs in CS/HAP scaffold was tested by SEM. The osteochondral defect (4 mm in diameter and 3 mm in height) model was made in the right knee joint of 36 Japanese white rabbits, which were randomly divided into 3 groups. Defects were repaired with CS/HAP and BMSCs composite ( group A, n = 12) and with CS/HAP implants (group B, n = 12); defects were not treated as a control (group C, n = 12). Histological evaluation and gross observation were carried out at 6 weeks (n = 6 in each group) and 12 weeks (n = 6 in each group) postoperatively. Semi-quantitative histomorphological analysis was done to evaluate the repair cartilage tissue according to the modified Wakitani grading scale. RESULTS: CS/HAP bilayered scaffold possessed a porosity of 76.00% +/- 5.01% and pore size of 200-400 MICROm (mean 300 microm) in CS layer, and 72.00% +/- 4.23% and 200-500 microm (mean 350 microm) in HAP layer, respectively. BMSCs formed colonies within 10-14 days. Immunocytochemistry results showed BMSCs had positive CD44 expression and negative CD45 expression. At 6 and 12 weeks after operation, gross and histological observation showed that the cartilage defects were fully filled with regenerated tissue, but bone defects were partially repaired in group A; the cartilage and bone defects were partially filled with regenerated tissue in group B and group C. The modified Wakitani grading scale were 5.17 +/- 1.17 and 3.20 +/- 0.75 in group A, 9.00 +/- 0.63 and 6.00 +/- 0.89 in group B, and 10.00 +/- 0.89 and 9.60 +/- 0.82 in group C at 6 weeks and 12 weeks postoperatively, respectively; showing significant differences between group A and groups B, C (P < 0.05). CONCLUSION: The novel CS/HAP bilayered scaffold possesses porous structure and will possibly become a new biomaterial of osteochondral tissue engineering.