Ameliorated Mechanical and Dielectric Properties of Heat-Resistant Radome Cyanate Composites.

In order to improve the mechanical and dielectric properties of radome cyanate, a synergistic reinforcement method is employed to develop a resin-based ternary-composite with high heat-resistance and preferable radar-band transmission, which is expected to be applied to fabricate radomes capable of resisting high temperature and strong electric field. According to copolymerization characteristics and self-curing mechanism, epoxy resin (EP) and bismaleimide (BMI) are employed as reinforcements mixed into a cyanate ester (CE) matrix to prepare CE/BMI/EP composites of a heat-resistant radome material by high-temperature viscous-flow blending methods under the catalysis of aluminum acetylpyruvate. The crystallization temperature, transition heat, and reaction rate of cured polymers were tested to analyze heat-resistance characteristics and evaluate material synthesis processes. Scanning electron microscopy was used to characterize the micro-morphology of tensile fracture, which was combined with the tensile strength test and dynamic thermomechanical analysis to investigate the composite modifications on tenacity and rigidity. Weibull statistics were performed to analyze the experimental results of the dielectric breakdown field, and the dielectric-polarization and wave-transmission performances were investigated according to alternative current dielectric spectra. Compared with the pure CE and the CE composites individually reinforced by EP or BMI, the CE/BMI/EP composite acquires the most significant amelioration in both the mechanical and electrical insulation performances as indicated by the breaking elongation and dielectric breakdown strength being simultaneously improved by 40%, which are consistently manifested by the obviously increased transverse lines uniformly distributed on the fracture cross-section. Furthermore, the glass-transition temperature of CE/BMI/EP composite reaches the highest values of nearly 300 °C, with the relative dielectric constant and dielectric loss being mostly reduced to less than 3.2 and 0.01, respectively. The experimental results demonstrate that the CE/BMI/EP composite is a highly-qualified wave-transmission material with preferences in mechanical, thermostability, and electrical insulation performances, suggesting its prospective applications in low-frequency transmittance radomes.

Enhanced Photoacoustic and Photothermal Effect of Functionalized Polypyrrole Nanoparticles for Near-Infrared Theranostic Treatment of Tumor.

Functionalized nanomaterials with near-infrared (NIR) responsive capacity are quite promising for theranostic treatment of tumors, but formation of NIR responsive nanomaterials with enhanced theranostic ability and excellent biocompatibility is still very challenging. Herein, PEGylated indocyanine green (ICG)-loaded polypyrrole nanoparticles (PPI NPs) were designed and successfully formed through selecting polydopamine as the linkage between each component, demonstrating enhanced NIR responsive theranostic ability against tumor. By combining in vitro cell study with in vivo assay, the formed PPI NPs were proven to be fantastically biocompatible while effectively internalization in HeLa cells and retention in HeLa tumor were demonstrated by in vitro flow cytometry/confocal measurement and in vivo photoacoustic imaging assay. With the guidance of photoacoustic imaging, successful photothermal ablation of tumor was achieved by treatment with PPI NPs plus laser, which was much more effective than the group treated with NPs free of ICG. The combined enhanced photoacoustic and photothermal effect is mainly ascribed to the functionalized polypyrrole nanoparticles, which could accumulate in the tumor site more effectively with a relatively longer retention time taking advantage of the nanomaterial-induced endothelial leakiness phenomenon. All these results demonstrating that this designed PPI NPs possessing enhanced NIR responsive property hold great promise for tumor NIR theranostic applications.

Acid-Activatable Theranostic Unimolecular Micelles Composed of Amphiphilic Star-like Polymeric Prodrug with High Drug Loading for Enhanced Cancer Therapy.

Stimuli-responsive nanomedicine with theranostic functionalities with reduced side-effects has attracted growing attention, although there are some major obstacles to overcome before clinical applications. Herein, we present an acid-activatable theranostic unimolecular micelles based on amphiphilic star-like polymeric prodrug to systematically address typical existing issues. This smart polymeric prodrug has a preferable size of about 35 nm and strong micellar stability in aqueous solution, which is beneficial to long-term blood circulation and efficient extravasation from tumoral vessels. Remarkably, the polymeric prodrug has a high drug loading rate up to 53.1 wt%, which induces considerably higher cytotoxicity against tumor cells (HeLa cells and MCF-7 cells) than normal cells (HUVEC cells) suggesting a spontaneous tumor-specific targeting capability. Moreover, the polymeric prodrug can serve as a fluorescent nanoprobe activated by the acidic microenvironment in tumor cells, which can be used as a promising platform for tumor diagnosis. The superior antitumor effect in this in vitro study demonstrates the potential of this prodrug as a promising platform for drug delivery and cancer therapy.

pH-controllable synthesis of unique nanostructured tungsten oxide aerogel and its sensitive glucose biosensor.

This work presents a controllable synthesis of nanowire-networked tungsten oxide aerogels, which was performed by varying the pH in a polyethyleneimine (PEI)-assisted hydrothermal process. An enzyme-tungsten oxide aerogel co-modified electrode shows high activity and selectivity toward glucose oxidation, thus holding great promise for applications in bioelectronics.

Polydopamine-functionalization of graphene oxide to enable dual signal amplification for sensitive surface plasmon resonance imaging detection of biomarker.

Surface plasmon resonance imaging (SPRi) is one of the powerful tools for immunoassays with advantages of label-free, real-time, and high-throughput; however, it often suffers from limited sensitivity. Herein we report a dual signal amplification strategy utilizing polydopamine (PDA) functionalization of reduced graphene oxide (PDA-rGO) nanosheets for sensitive SPRi immunoassay in serum. The PDA-rGO nanosheet is synthesized by oxidative polymerization of dopamine in a gentle alkaline solution in the presence of graphene oxide (GO) sheets and then is antibody-conjugated via a spontaneous reaction between the protein and the PDA component. In the dual amplification mode, the first signal comes from capture of the antibody-conjugated PDA-rGO to form sandwiched immunocomplexes on the SPRi chip, followed by a PDA-induced spontaneous gold reductive deposition on PDA-rGO to further enhance the SPRi signal. The detection limit as low as 500 pg mL(-1) is achieved on a nonfouling SPRi chip with high specificity and a wide dynamic range for a model biomarker, carcinoembryonic antigen (CEA) in 10% human serum.

PDMS-film coated on PCB for AC impedance sensing of biological cells.

Microfluidic impedance sensor has been introduced as a cost effective platform in biological cell sensing and counting since several decades ago. Conventional microfluidic impedance sensor usually requires the patterned gold electrodes directly in contact with the carrying buffer to measure the electrical current change due to the blockage of cells. However, patterning metal electrode probes on the silicon or glass substrate is a non-trivial task, which increases the fabrication cost of the impedance sensor. In this paper, we demonstrate an alternating current (AC) impedance based microfluidic cytometer built on a printed circuit board (PCB) coated with polydimethylsiloxane (PDMS) thin film. In addition, circulating tumor cells (Hela cells) are used to successfully demonstrate the feasibility of the microfluidic AC impedance sensor in tumor cell detection. The electrodes pre-deposited PCB costs less than US$2.00 and is widely available in the market. This device has a good potential for point-of-care diagnosis in resource-poor settings.

Weavable yarn-shaped supercapacitor in sweat-activated self-charging power textile for wireless sweat biosensing.

The yarn-based sweat-activated battery (SAB) is a promising energy source for textile electronics due to its excellent skin compatibility, great weavability, and stable electric output. However, its power density is too low to support real-time monitoring and wireless data transmission. Here, we developed a scalable, high-performance sweat-based yarn biosupercapacitor (SYBSC) with two symmetrically aligned electrodes made by wrapping hydrophilic cotton fibers on polypyrrole/poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate)-modified stainless steel yarns. Once activated with artificial sweat, the SYBSC could offer a high areal capacitance of 343.1 mF cm-2 at 0.5 mA cm-2. After 10,000 times of bending under continuous charge-discharge cycles and 25 cycles of machine washing, the device could retain the capacitance at rates of 68% and 73%, respectively. The SYBSCs were integrated with yarn-shaped SABs to produce hybrid self-charging power units. The hybrid units, pH sensing fibers, and a mini-analyzer were woven into a sweat-activated all-in-one sensing textile, in which the hybrid, self-charging units could power the analyzer for real-time data collection and wireless transmission. The all-in-one electronic textile could be successfully employed to real-time monitor the pH values of the volunteers' sweat during exercise. This work can promote the development of self-charging electronic textiles for monitoring human healthcare and exercise intensity.

Zinc ions and ciprofloxacin-encapsulated chitosan/poly(ɛ-caprolactone) composite nanofibers promote wound healing via enhanced antibacterial and immunomodulatory.

Antibacterial and anti-inflammatory nanofibrous membranes have attracted extensive attention, especially for the cutaneous wound treatment. In this study, zinc ions and ciprofloxacin-encapsulated chitosan/poly(ɛ-caprolactone) (CS/PCL) electrospun core-shell nanofibers were prepared by employing zinc ions-coordinated chitosan as the shell, and ciprofloxacin-functionalized PCL as the core. The morphology and core-shell structure of the as-prepared composite nanofibers were examined by SEM and TEM, respectively. The physical structure and mechanical property of the electrospun membrane were explored by FTIR, swelling, porosity and tensile test. Tensile strength of the zinc ions-coordinated CS/PCL composite nanofibers was enhanced to ca. 16 MPa. Meanwhile, the composite nanofibers can rapidly release of ciprofloxacin during 11 days and effectively suppress above 98 % of S. aureus proliferation. Moreover, the composite nanofibers exhibited excellent guide cell alignment and cyto-activity, as well as significantly down-regulated the inflammation factors, IL-6 and TNF-α in vitro. Animal experiments in vivo showed that the zinc ions-coordinated CS/PCL membrane by means of the synergistic effect of ciprofloxacin and active zinc ions, could significantly alleviate macrophage infiltration, promote collagen deposition and accelerate the healing process of wounds.

A polycationic antimicrobial and biocompatible hydrogel with microbe membrane suctioning ability.

Despite advanced sterilization and aseptic techniques, infections associated with medical implants have not been eradicated. Most present coatings cannot simultaneously fulfil the requirements of antibacterial and antifungal activity as well as biocompatibility and reusability. Here, we report an antimicrobial hydrogel based on dimethyldecylammonium chitosan (with high quaternization)-graft-poly(ethylene glycol) methacrylate (DMDC-Q-g-EM) and poly(ethylene glycol) diacrylate, which has excellent antimicrobial efficacy against Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Fusarium solani. The proposed mechanism of the antimicrobial activity of the polycationic hydrogel is by attraction of sections of anionic microbial membrane into the internal nanopores of the hydrogel, like an 'anion sponge', leading to microbial membrane disruption and then microbe death. We have also demonstrated a thin uniform adherent coating of the hydrogel by simple ultraviolet immobilization. An animal study shows that DMDC-Q-g-EM hydrogel coating is biocompatible with rabbit conjunctiva and has no toxicity to the epithelial cells or the underlying stroma.

Electrospun ZnO-loaded chitosan/PCL bilayer membranes with spatially designed structure for accelerated wound healing.

A multifunctional bilayer membrane with electrospinning chitosan (CS) and active ZnO nanoparticles was designed. The outer-layer was constructed with ZnO-encapsulated poly(ε-caprolactone) (PCL) ultrafine fibers in a randomly-orientated structure, which could impart the bilayer membrane with great antibacterial activity. The inner-layer was composed with CS fibers with aligned core-shell structure, which could provide anti-inflammatory and effective cell contact guide function. The structure, morphology and crystallization behavior of the bilayer membrane was investigated by FTIR, TEM, SEM and XRD. Importantly, the bi-layered CS/PCL electrospun membrane loading 1.2 wt% ZnO nanoparticles exhibited an enhanced tensile strength and an obvious inhibitory zone against E. coli and S. aureus, and also presented a non-cytotoxic behavior to fibroblasts. Moreover, the as-prepared bi-layered membrane enabled the maintenance of high bioavailability of ZnO nanoparticles and synchronization with the aligned structural feature of CS fibers, which alleviated inflammation, stimulated cellular migration and re-epithelialization in vivo.

Highly stable branched cationic polymer-functionalized black phosphorus electrochemical sensor for fast and direct ultratrace detection of copper ion.

Copper ions (Cu2+) is an indispensable trace element in the process of metabolism and intake of excessive Cu2+ may lead to fatal diseases such as Alzheimer's disease. It is highly demanding to develop a sensitive, selective and convenient method for Cu2+ detection. In this work, thin-layer structured polyethyleneimine (PEI) decorated black phosphorus (BP) nanocomposite is one-step synthesized for an electrochemical sensor toward direct detection of Cu2+. This sensor achieves a wide detection range of 0.25-177 µM, a low detection limit of 0.02 µM much below the Environmental Protection Agency (EPA) maximum contaminant levels for drinking water (20 µM for Cu2+), and much faster response (1.5 s response time) and simpler operation than the conventional tedious anodic stripping voltammetry, ranking one of the best among all reported Cu2+ sensor. The great sensing enhancement is mainly due to a synergistic effect of BP and PEI of the composite, of which the former offers the reactivity while the latter splits the thick BP to thin-layer structured PEI-BP composite for larger reaction area. Meanwhile, a flexible sensor has been successfully fabricated and applied in detecting of Cu2+ in real samples of river, confirming the application feasibility of PEI-BP sensor in water environment control.

Simultaneous deposition of tannic acid and poly(ethylene glycol) to construct the antifouling polymeric coating on Titanium surface.

Titanium (Ti) and its alloys are primarily explored to produce biomedical implants owing to their improved mechanical stability, corrosion resistance, low density, and good biocompatibility. Despite, Ti substrate surfaces are easily contaminated by plasma proteins and bacteria. Herein, a simple one-step process for the simultaneous deposition of a polyphenol tannic acid (TA) and four-armed poly(ethylene glycol) (PEG10k-4-OH) on the Ti substrate (Ti-TA/PEG) surface was described. Additionally, a two-step process has been employed to fabricate the Ti-TA-PEG surface via successive deposition of TA and PEG10k-4-OH for comparison. The resultant Ti-TA/PEG surface prepared by simultaneous deposition of TA and PEG10k-4-OH exhibits higher coating thickness and better surface coverage than the Ti-TA-PEG surface. The Ti-TA/PEG and Ti-TA-PEG surfaces could actively inhibit the non-specific adsorption of proteins, suppress the bacterial and platelet adhesion, and prevents biofilm formation. Moreover, the Ti-TA/PEG surface displays a better antifouling performance than the Ti-TA-PEG surface. Thus, the present study demonstrates a simple and convenient approach for constructing polymeric coating with good anti-adhesive properties on the Ti substrate surface.

Mussel Adhesive Mimetic Silk Sericin Prepared by Enzymatic Oxidation for the Construction of Antibacterial Coatings.

With the rapid development and advancement in orthodontic and orthopedic technologies, the demand for biomedical-grade titanium (Ti) alloys is growing. The Ti-based implants are susceptible to bacterial infections, leading to poor healing and osteointegration, resulting in implant failure or repeated surgical intervention. Silk sericin (SS) is hydrophilic, biocompatible, and biodegradable and could induce a low immunological response in vivo. As a result, it would be intriguing to investigate the use of hydrophilic SS in surface modification. In this work, the tyrosine moiety in SS was oxidized by tyrosinase (or polyphenol oxidase) to the 3,4-dihydroxyphenylalanine (DOPA) form, generating the catechol moiety-containing SS (SSC). Inspired by the adhesion of mussel foot proteins, the SSC coatings could be directly deposited onto multiple surfaces in SS and tyrosinase mixed stock solutions to create active surfaces with catechol groups. Further, the SSC-coated Ti surfaces were hybridized with silver nanoparticles (Ag NPs) via in situ silver ion (Ag+) reduction. The antibacterial properties of the Ag NPs/SS-coated Ti surfaces are demonstrated, and they can prevent bacterial cell adhesion as well as early-stage biofilm formation. In addition, the developed Ag NPs/SSC-coated Ti surfaces exhibited a negligible level of cytotoxicity in L929 mouse fibroblast cells.

Direct electron transfer of glucose oxidase and biosensing of glucose on hollow sphere-nanostructured conducting polymer/metal oxide composite.

A hollow sphere-nanostructured conductive polymer/metal oxide composite was synthesized and used to investigate the electrochemical behavior of glucose oxidase, demonstrating a significantly enhanced direct electron transfer ability of glucose oxidase. In particular, the long-standing puzzle of whether enzymatic glucose sensing involves an enzyme direct electron transfer process was studied. The results indicate the mechanism is indeed a glucose oxidase direct electron transfer process with competitive glucose oxidation and oxygen reduction to detect glucose. A glucose biosensor with the glucose oxidase-immobilized nanomaterial was further constructed, demonstrating superior sensitivity and reliability, and providing great potential in clinical applications.

Bienzymatic synergism of vanadium oxide nanodots to efficiently eradicate drug-resistant bacteria during wound healing in vivo.

Antibiotic resistance is a common phenomenon observed during treatment with antibacterials. Use of nanozymes, especially those with synergistic enzyme-like activities, as antibacterials could overcome this problem, but their synthesis is limited by their high cost and/or complex production process. Herein, vanadium oxide nanodots (VOxNDs) were prepared via a one-step bottom-up ethanol-thermal method using vanadium trichloride as the precursor. VOxNDs alone possess bienzyme mimics of peroxidase and oxidase. Accordingly, highly efficient antibacterials against drug-resistant bacteria can be obtained through synergistic catalysis; the oxidase-like activity decomposes O2 to generate superoxide anion radical (O2-) and hydroxyl radicals (OH), and the intrinsic peroxidase-like activity can further induce the production of OH from external H2O2. Consequently, H2O2 concentration could decrease up to four magnitude orders with VOxNDs to achieve an antibacterial efficacy similar to that of H2O2 alone. Wound healing in vivo further confirms the high antibacterial efficiency, good biocompatibility, and application potential of the synergistic antibacterial system due to the "nano" structure of VOxNDs. The method of synthesis of nanodot antibacterials described in this paper is inexpensive, and the results of this study reveal the multi-enzymatic synergism of nanozymes.

Amino-containing tannic acid derivative-mediated universal coatings for multifunctional surface modification.

The development of a universal coating strategy for the construction of functional surfaces and modulation of surface properties is of great research interest. Tannic acid (TA) could serve as a sole precursor for the deposition of colorless coatings on substrate surfaces. However, the deposition of TA requires a high salt concentration (0.6 M), which may limit its practical application. Herein, primary amine moieties were introduced on the gallic acid groups in TA. The resultant amine-containing TA derivative (TAA) can self-polymerize under mild conditions (10 mM, Tris buffer), and form uniform and colorless coatings in a material-independent manner. In comparison with the TA coating under the same preparation conditions, the TAA coating exhibits an increased thickness as measured by ellipsometry. The TAA coating is adapted for secondary surface functionalization. The hydrophilic mPEG brushes can be grafted on the TAA coating to inhibit non-specific protein adsorption. A biotin probe can be immobilized on the TAA coating to promote specific binding with avidin. In addition, the TAA coating can be utilized for in situ reduction of silver ions to AgNPs. The resulting AgNP-loaded TAA coating can inhibit bacterial adhesion and prevent biofilm formation.

On-demand microfluidic droplet trapping and fusion for on-chip static droplet assays.

On-demand droplet trapping and droplet fusion through novel approaches were successfully demonstrated to form a static droplet assay on-chip for timelapse studies of droplet based microreactions.

Flow-through functionalized PDMS microfluidic channels with dextran derivative for ELISAs.

In this work, a dextran modified PDMS microfluidic ELISA device was fabricated. The dextran functionalization was conducted with a simple, economic and fast flow-through process in a fabricated PDMS microfluidic device, and demonstrated significant enhancement of hydrophilicity and efficient covalent immobilization of proteins on the PDMS microchannel surface. The device was used to simultaneously detect multiple important biomarker IL-5, HBsAg, and IgG, showing a limit of detection of 100 pg mL(-1) and a dynamic range of 5 orders of magnitude, which significantly improved the performance of the reported hydrophobic and plasma-treated hydrophilic PDMS flow-through immunoassay devices. The fabricated PDMS device demonstrated its capability for colorimetric detection of proteins through direct observation by human eyes. Thus, this work not only demonstrates great potential to fabricate an economical and sensitive lab-on-chip system for high throughput screening of various infectious diseases, but also provides an opportunity to develop a portable microfluidic ELISA device via human eye examination for heath point-of-care services.

AFM study of adsorption of protein A on a poly(dimethylsiloxane) surface.

In this paper, the morphology and kinetics of adsorption of protein A on a PDMS surface is studied by AFM. The results of effects of pH, protein concentration and contact time of the adsorption reveal that the morphology of adsorbed protein A is significantly affected by pH and adsorbed surface concentration, in which the pH away from the isoelectric point (IEP) of protein A could produce electrical repulsion to change the protein conformation, while the high adsorbed surface protein volume results in molecular networks. Protein A can form an adsorbed protein film on PDMS with a maximum volume of 2.45 x 10(-3) microm(3). This work enhances our fundamental understanding of protein A adsorption on PDMS, a frequently used substrate component in miniaturized immunoassay devices.

Co-delivery of chlorin e6 and doxorubicin using PEGylated hollow nanocapsules for 'all-in-one' tumor theranostics.

Aim: Hollow mesoporous copper sulfide nanocapsules conjugated with poly(ethylene glycol) (PEG), doxorubicin and chlorin e6 (HPDC) were synthesized for fluorescence imaging and multimodal tumor therapy. Materials & methods: HPDC were synthesized by encapsulating chlorin e6 and doxorubicin into PEGylated nanocapsules via a simple precipitation method. The photothermal/photodynamic effects, drug release, cellular uptake, imaging capacities and antitumor effects of the HPDCs were evaluated. Results: This smart nanoplatform is stimulus-responsive toward an acidic microenvironment and near infrared laser irradiation. Moreover, fluorescence imaging-guided and combined photothermal/photodynamic/chemotherapies of tumors were promoted under laser activation and led to efficient tumor ablation, as evidenced by exploring animal models in vivo. Conclusion: HPDCs are expected to serve as potent and reliable nanoagents for achieving superior therapeutic outcomes in cancer management.