Magnetic chitosan/graphene oxide composite loaded with novel photosensitizer for enhanced photodynamic therapy

Photodynamic therapy (PDT) is an increasingly recognized alternative to treat various cancers in clinical practice. Most second-generation photosensitizers (PS) are hydrophobic and have poor targeting selectivity, which limit their efficacy for PDT. In this paper, graphene oxide (GO) coupled with magnetic Fe₃O₄ nanoparticles and chitosan (CS) (MCGO) was prepared by a one-pot solvothermal method and used as a nanocarrier for loading the new photosensitizer HNPa (λ_max = 698 nm), which was first synthesized by our group, and was considered as a good water-soluble drug and an excellent tissue-penetrating agent due to its strong absorption at 698 nm (near-infrared region). The synthesized composite (MCGO–HNPa) showed high stability, good water solubility and biocompatibility, expected magnetic targetability, and good photostability for PDT even in low concentrations. Our research reveals that MCGO nanomaterials can promote the production and release of singlet oxygen (Φ_Δ = 62.9%) when compared with free HNPa. In addition, the in vitro cell uptake experiments suggested that the MCGO nanomaterials can accelerate the penetration of HNPa drugs into the tumor cell nucleus and that the drug release behavior is pH-sensitive. The MTT assay results against human hepatoma cell lines HepG-2 clearly show that the MCGO–HNPa composite can effectively result in cell damage and apoptotic cell death under light, and that the nanocomposite can improve the PDT antitumor effect of PS agents with negligible dark toxicity. Meanwhile, the research on the photoreaction mechanism reveals that Type I and Type II photodynamic reactions can occur simultaneously in this PDT process, and their relative contributions depend on the type and dose of the photosensitizer. Type II has a greater effect on PDT than Type I, especially for a higher HNPa photosensitizer dose. All the results reveal the promising application of the presented novel strategy.

Prepared magnetic chitosan/graphene oxide composite loaded with a novel photosensitizer (MCGO–HNPa) showed excellent PDT activity against HepG-2 cells.     

羧甲基壳聚糖/羟乙基纤维素共混凝胶的制备及性能

将羟乙基纤维素和羧甲基壳聚糖通过戊二醛交联制备羧甲基壳聚糖,羟乙基纤维素凝胶,考察不同质量比的共混凝胶在不同pH缓冲液中的溶胀和释药性能.在溶胀性能研究中,pH值为1.0时凝胶的溶胀度小于pH值为3,5,7时.在羧甲基壳聚糖:羟乙基纤维素为5:5时,其最大溶胀度可以达到4.2左右,相比其他质量比共混体系,其溶胀效果明显增强.各种释放条件下,单纯羧甲基壳聚糖的交联体系,牛血清蛋白释放速度最大,随着羟乙基纤维素比例的增加,牛血清蛋白的药物释放速度变快,释放量在逐渐变大,pH=1.0时,羧甲基壳聚糖:羟乙基纤维素为7:3,药物释放百分比为60%;而羧甲基壳聚糖:羟乙基纤维素为5:5时,药物释放百分比约为80%左右.说明羧甲基壳聚糖,羟乙基纤维素共混凝胶适合于胃部滞留给药.     

Enhanced bioactivity and osteoinductivity of carboxymethyl chitosan/nanohydroxyapatite/graphene oxide nanocomposites

Tissue engineering approaches combine a bioscaffold with stem cells to provide biological substitutes that can repair bone defects and eventually improve tissue functions. The prospective bioscaffold should have good osteoinductivity. Surface chemical and roughness modifications are regarded as valuable strategies for developing bioscaffolds because of their positive effects on enhancing osteogenic differentiation. However, the synergistic combination of the two strategies is currently poorly studied. In this work, a nanoengineered scaffold with surface chemistry (oxygen-containing groups) and roughness (R_q = 74.1 nm) modifications was fabricated by doping nanohydroxyapatite (nHA), chemically crosslinked graphene oxide (GO) and carboxymethyl chitosan (CMC). The biocompatibility and osteoinductivity of the nanoengineered CMC/nHA/GO scaffold was evaluated in vitro and in vivo, and the osteogenic differentiation mechanism of the nanoengineered scaffold was preliminarily investigated. Our data demonstrated that the enhanced osteoinductivity of CMC/nHA/GO may profit from the surface chemistry and roughness, which benefit the β1 integrin interactions with the extracellular matrix and activate the FAK–ERK signaling pathway to upregulate the expression of osteogenic special proteins. This study indicates that the nanocomposite scaffold with surface chemistry and roughness modifications could serve as a novel and promising bone substitute for tissue engineering.

The CMC/nHA/GO scaffold with the surface chemistry and roughness dual effects and the release of phosphate and calcium ions synergistically assist the mineralization and facilitate the bone regeneration.     

羧甲基壳聚糖温敏凝胶的制备及其毒性实验

背景:与壳聚糖相比,羧甲基壳聚糖的水溶性提高,且安全、无毒、无害,具有成膜性、保湿性、生物相容性好的特点,是一种良好的药物载体.目的:自制羧甲基壳聚糖温敏凝胶,了解其对小鼠肺成纤维细胞L929的毒性作用.方法:利用羧甲基壳聚糖与甘油磷酸盐互配,制备羧甲基壳聚糖温敏凝胶.采用四甲基偶氮唑盐法测定50,10,2,0.4,0.08倍的羧甲基壳聚糖温敏凝胶浸提液对体外培养L929细胞的细胞毒性,并设定阳性与阴性对照组.测定加样后24,48,72,96 h的A值,计算细胞相对增殖率,评定细胞毒性等级.结果与结论:各组细胞不同时间点相对增殖率均在103%～228%之间,各浓度羧甲基壳聚糖温敏凝胶材料浸提液的细胞毒性均为0级.提示羧甲基壳聚糖温敏凝胶对L929细胞无毒性作用,且有良好的生物相容性,在牙周病治疗中具有潜在的应用价值.     

A simple electrochemical immunosensor based on a chitosan/reduced graphene oxide nanocomposite for sensitive detection of biomarkers of malignant melanoma

The sensitive and specific detection of tumor biomarkers is crucial for early diagnosis and treatment of malignant melanoma. Immunoassay with a simple sensing interface and high sensitivity is highly desirable. In this work, a simple electrochemical immunosensor based on a chitosan/reduced graphene oxide (CS–rGO) nanocomposite was developed for sensitive determination of an S-100B protein, a tumor marker of malignant melanoma. CS–rGO nanocomposite were prepared by chemical reduction of graphene oxide in the presence of chitosan and modified on glassy carbon electrode (GCE) to provide a biofriendly, conductive, and easily chemically modified matrix for further immobilization of antibodies. Anti-S-100B antibodies were grafted onto the chitosan molecules to fabricate the immunorecognition interface by a simple glutaraldehyde cross-linking method. Electrochemical determination of S-100B was achieved by measuring the decreased current signal of solution phase electrochemical probes, which originated from the increased steric hindrance and insulation caused by the formation of antigen–antibody complexes at the electrode interface. Due to the good conductivity, high surface area, excellent biocompatibility, and good film-forming ability of CS–rGO, the constructed immunosensor exhibited good stability, high selectivity and sensitivity, a wide dynamic range from 10 fg mL⁻¹ to 1 ng mL⁻¹ and a low limit of detection of 1.9 pg mL⁻¹ (S/N = 3). Moreover, the sensor was also applicable for the sensitive detection of S-100B protein in real human serum samples.

Simple electrochemical immunosensor is easily fabricated based on chitosan/reduce graphene oxide nanocomposite for sensitive determination of a tumor marker of malignant melanoma.     

Flexible solid-state supercapacitor based on tin oxide/reduced graphene oxide/bacterial nanocellulose

We demonstrate a flexible and light-weight supercapacitor based on bacterial nanocellulose (BNC) incorporated with tin oxide (SnO₂) nanoparticles, graphene oxide (GO) and poly(3,4-ethylenedioxyiophene)-poly(styrenesulfonate) (PEDOT:PSS). The SnO₂ and GO flakes are introduced into the fibrous nanocellulose matrix during bacteria-mediated synthesis. The flexible PEDOT:PSS/SnO₂/rGO/BNC electrodes exhibited excellent electrochemical performance with a capacitance of 445 F g⁻¹ at 2 A g⁻¹ and outstanding cycling stability with 84.1% capacitance retention over 2500 charge/discharge cycles. The flexible solid-state supercapacitors fabricated using PEDOT:PSS/SnO₂/rGO/BNC electrodes and poly(vinyl alcohol) (PVA)-H₂SO₄ coated BNC as a separator exhibited excellent energy storage performance. The fabrication method demonstrated here is highly scalable and opens up new opportunities for the fabrication of flexible cellulose-based energy storage devices.

A novel, simple and scalable method for the incorporation of tin oxide (SnO₂) and graphene oxide (GO) into bacterial nanocellulose during its growth for the fabrication of a flexible, scalable and environmental-friendly energy storage device was reported.     

温敏凝胶制备及其在体内的生物相容性评价

学术背景:凝胶材料在体温条件下能以凝胶形式稳定存在,是其作为医学植入物的必备条件,故需要将温敏型凝胶的低临界溶解温度调节到超过人体体温的水平.目的:制备低临界溶解温度超过37 ℃的温敏凝胶材料聚-(N-异丙基丙稀酰胺/N-羟甲基丙烯酰胺) P(NIPAAm-co-NHMPA),并初步评价其作为医学植入物的安全性.设计:随机、非盲法、分组对照动物实验.单位:华中科技大学同济医学院附属协和医院骨科.材料:实验于2007-01/10在华中科技大学同济医学院附属协和医院中心实验室、武汉大学化学系医用高分子材料教育部重点实验室完成.NIPAAm和NHMPA单体购自Aldrich公司、交联剂N, N'-亚甲基双丙烯酰胺(MBAAm)购自Fluka公司、促进剂过硫酸铵(APS)和四甲基乙二胺(TEMED)购自Sigma公司.方法:①温敏凝胶的制备:以APS和TEMED为氧化还原引发体系,MBAAm为交联剂制备P(NIPAAm-co-NHMPA),反应体系中添加一定质量分数的NHMP,溶涨率法测定低临界溶解温度.②安全性评价:进行过敏实验、急性全身毒性实验、遗传毒性实验、植入实验等一系列体内生物相容性动物实验以评估植入物的安全性.主要观察指标:过敏实验记录激发部位红斑水肿;急性全身中毒实验观察记录注射后4,24,48和72 h动物的一般状态;遗传毒性实验于注射6 h后在显微镜下计数鼠骨髓多染红细胞微核;植入实验将制得的切片进行光镜下观察.结果:①合成的凝胶材料符合预期的温敏特性要求,低临界溶解温度为38 ℃.②在过敏实验皮内注射浸提液及生理盐水组皮肤无红斑水肿;急性全身毒性实验显示腹腔注射浸提液及生理盐水组无毒性表现;遗传毒性实验中实验组和阴性对照组鼠骨髓多染红细胞的微核出现率无差异;体内植入实验表明材料周围炎性反应轻微而局限.结论:温敏凝胶P(NIPAAm-co-NHMPA)的生物相容性良好,是一种有潜力的医学植入物.     

温敏凝胶制备及其在体内的生物相容性评价

学术背景：凝胶材料在体温条件下能以凝胶形式稳定存在，是其作为医学植入物的必备条件，故需要将温敏型凝胶的低临界溶解温度调节到超过人体体温的水平。目的：制备低临界溶解温度超过37℃的温敏凝胶材料聚．（N-异丙基丙稀酰胺/N-羟甲基丙烯酰胺）P（NIPAAm-co-NHMPA），并初步评价其作为医学植入物的安全性。设计：随机、非盲法、分组对照动物实验。单位：华中科技大学同济医学院附属协和医院骨科。材料：实验于2007-01/10在华中科技大学同济医学院附属协和医院中心实验室、武汉大学化学系医用高分子材料教育部重点实验室完成。NIPAAm和NHMPA单体购自Aldrich公司、交联剂N，N’-亚甲基双丙烯酰胺（MBAAm）购自Fluka公司、促进剂过硫酸铵（APS）和四甲基乙二胺（TEMED）购自Sigma公司。方法：①温敏凝胶的制备：以APS和TEMED为氧化还原引发体系，MBAAm为交联剂制备P（NIPAAm-co-NHMPA），反应体系中添加一定质量分数的NHMP，溶涨率法测定低临界溶解温度。②安全性评价：进行过敏实验、急性全身毒性实验、遗传毒性实验、植入实验等一系列体内生物相容性动物实验以评估植入物的安全性。主要观察指标：过敏实验记录激发部位红斑水肿；急性全身中毒实验观察记录注射后4，24，48和72h动物的一般状态；遗传毒性实验于注射6h后在显微镜下计数鼠骨髓多染红细胞微核；植入实验将制得的切片进行光镜下观察。结果：①合成的凝胶材料符合预期的温敏特性要求，低临界溶解温度为38℃。②在过敏实验皮内注射浸提液及生理盐水组皮肤无红斑水肿；急性全身毒性实验显示腹腔注射浸提液及生理盐水组无毒性表现；遗传毒性实验中实验组和阴性对照组鼠骨髓多染红细胞的微核出现率无差异；体内植入实验表明材料周围炎性反应轻微而局限。结     

Preparation of novel phosphorus-nitrogen-silicone grafted graphene oxide and its synergistic effect on intumescent flame-retardant polypropylene composites

Due to the poor dispersion in polymer matrix, graphene can hardly be used alone as a flame-retardant additive for polymers. In this paper, a novel halogen-free flame retardant – the ternary graft product of silsesquioxane, graphene oxide and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (PMGO) with a structure of graphene oxide layers modified with the synergistic flame retardant multiple elements of phosphorous, nitrogen and silicon was synthesized and then used in combination with traditional intumescent flame retardant (IFR) to enhance the flame retardancy of polypropylene (PP). The experimental results show that the thermal and flame retardant properties of flame-retardant (FR) PP composites are significantly improved by introducing 5 wt% PMGO as well as 20 wt% IFR. The peak heat release rate and total heat release of the FR PP composite are reduced 61.5% and 40.2%, respectively, compared to neat PP. Based on the char layer observation and thermal analysis, the enhancement in flame retardancy is mainly attributed to the outstanding intumescent char layers with high strength and thermal stability formed under the synergistic effect of PMGO and IFR. Besides, the introduced phosphorous, nitrogen and silicon hydrophilic groups do not show the negative effects on the surface hydrophobicity of flame retardant PP materials, which could broaden its scope of application.

The combination of PMGO and IFR significantly improves the flame retardancy and surface hydrophobicity of PP materials.     

Preparation and characterization of a novel positively charged composite hollow fiber nanofiltration membrane based on chitosan lactate

A positively charged composite hollow fiber nanofiltration (NF) membrane was prepared via interfacial polymerization (IP) between chitosan lactate (CL) and trimesoyl chloride (TMC) on a polyether sulfone (PES) hollow fiber ultrafiltration (UF) membrane. The chemical structure and the morphologies of the resultant NF membranes were characterized with attenuated total reflectance-infrared spectroscopy (ATR-IR) and scanning electron microscopy (SEM). The rejection of NF membrane for different inorganic salt aqueous solutions followed the order: MgCl₂ > ZnCl₂ > MgSO₄ > NaCl > Na₂SO₄. It suggested that this novel kind of composite hollow fiber NF membrane is positively charged. The molecular weight cut-off (MWCO) was obtained through the rejection of polyethylene glycol (PEG) solutions with different molecular weights (M_w). The effect of monomer concentrations, the interfacial polymerization time, and the curing temperature, were investigated, respectively. The rejection and the permeate flux of the resultant composite hollow fiber CL membrane fabricated under the optimal conditions towards a MgCl₂ solution of 1000 ppm were 95.1% and 10.3 L m⁻² h⁻¹, respectively, at 0.4 MPa and 25 °C. Moreover, the effects of operation conditions on the rejection performance of the composite hollow fiber NF membrane were investigated. It suggested that this novel kind of hollow fiber composite nanofiltration membrane based on CL have excellent stability in rejection performances to salt solutions.

A positively charged composite hollow fiber nanofiltration (NF) membrane was prepared via interfacial polymerization by using chitosan lactate and trimesoyl chloride (TMC).     

Preparation of a novel polyacrylic acid and chitosan interpenetrating network hydrogel for removal of U(vi) from aqueous solutions

A clean and simple method has been developed for preparation of interpenetrating polymer networks using polyacrylic acid (PAA) and chitosan (CS) for extraction of uranium from polluted water. The peak of Fourier transform infrared spectroscopy (FTIR) occurred at 928 cm⁻¹ indicating combination of uranium and PAA/CS. The energy dispersive X-ray (EDX) and the scanning electron microscope (SEM) studies illustrated the formation of a crosslinking structure and excellent binding ability of uranium on PAA/CS. The maximum adsorption capacity was 289.6 mg g⁻¹ calculated using the equation of the Langmuir model. The adsorption capacity reached a plateau at pH 4 and the sorption process fits the pseudo-second-order model well. The PAA/CS composite has stability of reuse, with the adsorbent capacity decreasing slowly with increasing usage frequency. The experimental results confirm that the PAA/CS hydrogel could be a novel alternative for highly efficient removal of uranium from wastewater.

A clean and simple method has been developed for preparation of interpenetrating polymer networks using polyacrylic acid (PAA) and chitosan (CS) for extraction of uranium from polluted water.     

A novel surface plasmon resonance sensor based on a functionalized graphene oxide/molecular-imprinted polymer composite for chiral recognition of l-tryptophan

Herein, a novel surface plasmon resonance (SPR) sensor based on a functionalized graphene oxide (GO)/molecular-imprinted polymer composite was developed for the chiral recognition of l-tryptophan (l-Trp). The composite''s recognition element was prepared via a facile and green synthesis approach using polydopamine as both a reducer of GO and a functional monomer as well as a cross-linker for molecular imprinting. The composite was characterized via Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, and Raman spectroscopy. After attaching the composite onto the gold surface of an SPR chip, the sensor was characterized using contact-angle measurements. The sensor exhibited excellent selectivity and chiral recognition for the template (i.e., l-Trp). Density functional theory computations showed that the difference in hydrogen bonding between the composite element and l-Trp and d-Trp played an important role in chiral recognition.

Novel SPR sensor for chiral recognition of l-tryptophan using a functionalized graphene oxide/molecularly-imprinted polymer composite as a recognition element.     

Nanocomposite of hydrophobic cellulose aerogel/graphene quantum dot/Pd: synthesis,characterization, and catalytic application

Novel hydrophobic cellulose aerogel (CA) supported graphene quantum dots (GQD)/Pd were synthesized with high lipophilicity, superior porosity as well as high catalytic activity. The nanocomposite aerogel was obtained in four steps, including transformation of cotton to CA, a silanization reaction of CA in the presence of TiO₂ nanoparticles to give polysiloxane/TiO₂ nanoparticles supported on CA (ST@CA), a modification of ST@CA with GQD to yield polysiloxane/TiO₂ nanoparticles/graphene quantum dots supported on CA (STG@CA), and finally a deposition of Pd nanoparticles on STG@CA. The synthesized aerogel demonstrated hydrophobicity with a water contact angle of 136.2°. It also exhibited excellent oil/water selective absorption capacity with an oil absorption of up to 79 g g⁻¹ with 134 g g⁻¹ selectivity. Finally, the nanocomposite was used as a heterogeneous catalyst in the oxidation reaction of alcohols, ethylbenzene, and alkenes. High yields, excellent selectivities, green and mild reaction conditions, recyclability and biocompatibility of the catalyst were important features of the reactions.

Novel hydrophobic cellulose aerogel (CA) supported graphene quantum dots (GQD)/Pd were synthesized with high lipophilicity, superior porosity as well as high catalytic activity.     

Preparation and characterization of antibacterial dopamine-functionalized reduced graphene oxide/PLLA composite nanofibers

Electrospun poly(l)-lactide (PLLA) ultrafine fibers are a biodegradable and biocompatible scaffold, widely used in tissue engineering applications. Unfortunately, these scaffolds have some limitations related to the absence of bioactivity and antibacterial capacity. In this study, dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers were fabricated via electrospinning. The morphology and the physicochemical and biological properties of the composite nanofibers were investigated. The results indicate that incorporating rGO improves the hydrophilic, mechanical, and biocompatibility properties of PLLA nanofibers. Tetracycline hydrochloride (TC)-loaded rGO/PLLA composite nanofibers showed better controlled drug release profiles compared to GO/PLLA and PLLA nanofibrous scaffolds. Drug-loaded nanofibrous scaffolds showed significantly improved antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Additionally, rGO/PLLA composite nanofibers exhibited enhanced cytocompatibility. Thus, it can be concluded that rGO/PLLA composite nanofibers allow the development of multifunctional scaffolds for use in biomedical applications.

Antibacterial dopamine-functionalized reduced graphene oxide (rGO)/PLLA composite nanofibers for biomedical applications.     

A highly responsive methanol sensor based on graphene oxide/polyindole composites

Graphene-based materials, namely commercial graphene (cm-G), commercial graphene oxide (cm-GO), reduced graphene oxide (rGO), and synthesized graphene oxide (OIHM-GO), and their composites with polyindole (PIn) were used as sensing materials for methanol vapor. The synthesized graphene oxide was prepared by the optimized improved Hummers'' method. rGO was prepared from cm-GO by two different methods: thermally mild reduction at 120 °C to yield T-rGO and chemical reduction by ascorbic acid to yield C-rGO. Graphene-based material/polyindole composites were prepared by in situ polymerization. In this report, the sensing responses were evaluated from the responsive electrical currents at room temperature. cm-GO showed the highest methanol response because it possessed the highest number of oxygen species, which act as the active sites. The relative electrical conductivity response of the in situ cm-GO/dPIn composite to methanol was the highest amongst the composites. The in situ OIHM-GO/dPIn composite possessed the high relative conductivity response of 81.89 ± 2.12 at 11.36 ppm, a sensitivity of 7.37 ppm⁻¹ with R² of 0.9967 in the methanol concentration range of 1.14–11.36 ppm, a theoretical LOD of 0.015 ppm, and repeatability of at least 4 cycles with good selectivity. This work represents the first report of the preparation and testing of graphene-based materials/polyindole composites as methanol sensors.

The methanol response depended on the hydrophilicity of the composite materials; GO/dPIn demonstrated the highest oxygen content and the highest hydrophilicity, thus inducing high methanol adsorption into the inner layer of the composite.     

Progress in the functional modification of graphene/graphene oxide: a review

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties. This review focuses on the functional modification of graphene and graphene oxide. First, the basic structure, preparation methods and properties of graphene and graphene oxide are briefly described. Subsequently, the methods for the reduction of graphene oxide are introduced. Next, the functionalization of graphene and graphene oxide is mainly divided into covalent binding modification, non-covalent binding modification and elemental doping. Then, the properties and application prospects of the modified products are summarized. Finally, the current challenges and future research directions are presented in terms of surface functional modification for graphene and graphene oxide.

Graphene and graphene oxide have attracted tremendous interest over the past decade due to their unique and excellent electronic, optical, mechanical, and chemical properties.     

Strategy to design a smart photocleavable and pH sensitive chitosan based hydrogel through a novel crosslinker: a potential vehicle for controlled drug delivery

We report herein the synthesis of a novel photocleavable crosslinker, 4-formylphenyl 4-((4-formylphenoxy)methyl)-3-nitrobenzoate (CHO–ONB–CHO) and its joining with amine-based polysaccharides, viz. chitosan, resulting in the formation of a dual stimuli-responsive (ONB–chitosan) hydrogel having UV- and pH-responsive sites. The detailed mechanism for the formation of CHO–ONB–CHO and ONB–chitosan hydrogel is proposed. The (CHO–ONB–CHO) crosslinker was characterized using ¹H-NMR, LCMS and UV-visible spectroscopy. The dual responsive hydrogel is characterized by FTIR, SEM, XRD, DSC and TGA. The crosslinked hydrogel displayed mechanical robustness with a storage modulus of about 1741 pa. The pH-responsiveness of the hydrogel was studied via equilibrium swelling studies in various pH media at 37 °C. The photocleavable behavior of the crosslinker was observed in the UV-absorption range of 310–340 nm and the hydrogel exhibited maximum swelling at pH 5.7. The higher swelling of the hydrogel in acidic conditions and its photo-responsiveness can be exploited for the controlled, temporal and spatial release of therapeutic drugs at any inflammatory areas with acidic environments. It was observed that the hydrogel exhibited higher drug release at pH 5.7 than at pH 7.4.

We report the synthesis of a novel photocleavable crosslinker and its joining with amine-based polysachharides, viz. chitosan, resulting in the formation of a dual stimuli-responsive hydrogel having UV- and pH-responsive sites.     

Facile preparation of antibacterial hydrogel with multi-functions based on carboxymethyl chitosan and oligomeric procyanidin

Hydrogel-based antibacterial materials with multi-functions are of great significance for healthcare. Herein, a facile and one-step method was developed to fabricate an injectable hydrogel (named CMCS/OPC hydrogel) based on carboxymethyl chitosan (CMCS) and oligomeric procyanidin (OPC). In this hydrogel system, OPC serves as the dynamic crosslinker to bridge CMCS macromolecules mainly through dynamical hydrogen bonds, which endows this hydrogel with excellent injectable, self-healing, and adhesive abilities. In addition, due to the inherent antibacterial properties of CMCS and OPC, this hydrogel shows excellent antibacterial activity. Therefore, the well-designed CMCS/OPC hydrogel has great prospects as an antibacterial material in the biomedical field.

An injectable, self-healing, adhesive, and antibacterial CMCS/OPC hydrogel based on carboxymethyl chitosan (CMCS) and oligomeric procyanidin (OPC) was fabricated and characterized.     

Simultaneous detection of acetaminophen and 4-aminophenol with an electrochemical sensor based on silver–palladium bimetal nanoparticles and reduced graphene oxide

In this paper, Ag–Pd bimetallic nanoparticles uniformly distributed on reduced graphene oxide (rGO) were synthesized by redox reaction between Pd²⁺, Ag⁺and GO, and were characterized by X-ray diffractometry, field emission scanning electron microscopy, electrochemical impedance spectroscopy and thermal gravimetric analyses. A novel electrochemical sensor was constructed based on these nanocomposites using glassy carbon as a substrate. Under optimal conditions, the linear ranges were 0.50–300.00 μM for PA and 1.00–300.00 μM for 4-AP, with the detection limits of 0.23 μM for PA and 0.013 μM for 4-AP, respectively. This sensor was successfully applied to the determination of PA in pharmaceutical formulations and gave satisfactory results with a lower detection limit, wider linear range and good reproducibility.

Simultaneous detection of acetaminophen and 4-aminophenol with a highly sensitive electrochemical sensor based on silver–palladium bimetal nanoparticles and reduced graphene oxide.     

An ionic diode based on a spontaneously formed polypyrrole-modified graphene oxide membrane

Asymmetric membranes derived from the stacking of graphene oxide (GO) nanosheets have attracted great attention for the fabrication of ionic diodes. Herein, we described an ionic diode based on a polypyrrole-modified GO membrane with a vertical asymmetry, which was achieved by a spontaneous oxidation polymerization of pyrrole monomers on one side of the GO membrane in vapor phase. This asymmetric modification resulted in an asymmetric geometry due to the occupation of the interlayer space of one side of the GO membrane by polypyrrole. Our ionic diode demonstrated an obvious ionic rectification behavior over a wide voltage range. A calculation based on Poisson–Nernst–Planck equations was used to theoretically investigate the role of asymmetric modification of polypyrrole.

We described an ionic diode based on polypyrrole-modified graphene oxide membrane, which was prepared by a spontaneous oxidation polymerization of pyrrole monomers.