Combining bioinspired nanochannels with ferrocene doped MoS2 nanoplates: Application to ratiometric electrochemical detection of let-7a.

Sensitive and accurate detection of tumor suppressor genes is vastly important to the related therapeutic research. Herein, a ratiometric electrochemical method for let-7a detection was established by integrating a ferrocene (Fc) doped MoS2 nanoplates modified electrode into the nanochannels-based biosensing platform. The ratiometric signal was developed by the redox current of methylene blue (MB) which reflects the target recognition occurred into the nanochannels and the redox current of Fc which corrects the slight signal deviation caused by some analyte-independent factors. And thus, the ratio of peak current of MB and Fc (IMB/IFc) measured at differential pulse voltammogram varied precisely with the increment of the concentration of let-7a incubated in the bioinspired nanochannels. The strategy of spherical DNAzyme induced deposition in nanochannels was utilized to further amplify the signal. Under optimal conditions, a wide linear dynamic range of 50 aM to 10 pM spanning five orders of magnitude was obtained. The developed electrochemical method, with attomole level of detection limit, was successfully applied to the determination of let-7a in human serum and tumor cells. The study not only offers a new route for reliable nucleic acid detection, but also provides an excellent opportunity to extend the application of the two-dimensional transition-metal dichalcogenides.

MoS2 nanosheets supported on anodic aluminum oxide membrane: An effective interface for label-free electrochemical detection of microRNA.

The interesting adsorption affinity of two-dimensional nanosheets to single stranded over double stranded nucleic acids have stimulated the exploration of these materials in biosensing. Herein, MoS2 nanosheets decorated anodic aluminum oxide (AAO) membrane was simply prepared by suction filtration. The MoS2/AAO hybrid membrane was initially applied to the electrochemical detection of microRNA using let-7a as the model. When let-7a was incubated with its complementary DNA, double stranded DNA-RNA formed and which displayed weak adsorption capability to the hybrid membrane. And thus the steric effect combining the electrostatic repulsion of the backbone phosphate of nucleic acids for [Fe(CN)6]3- transport across the hybrid membrane varied with the concentration of let-7a. In this way, a label-free electrochemical detection method for microRNA was established by monitoring the change of the redox current of [Fe(CN)6]3-. To further improve the detection sensitivity of the method, we proposed two separate strategies focusing on the amplification of the target-induced steric hindrance with DNA nanostructure and the magnification of the electrode sensitivity for [Fe(CN)6]3- by electrode modification. By using the two strategies, the hybrid membrane based-detection method exhibited broad linear range, low detection limit and good selectivity as well as reproducibility. Therefore, this study provided a proof-of-concept for the application of two-dimensional material to nucleic acids detection.

Nanomaterials-Based Wound Dressing for Advanced Management of Infected Wound.

The effective prevention and treatment of bacterial infections is imperative to wound repair and the improvement of patient outcomes. In recent years, nanomaterials have been extensively applied in infection control and wound healing due to their special physiochemical and biological properties. Incorporating antibacterial nanomaterials into wound dressing has been associated with improved biosafety and enhanced treatment outcomes compared to naked nanomaterials. In this review, we discuss progress in the application of nanomaterial-based wound dressings for advanced management of infected wounds. Focus is given to antibacterial therapy as well as the all-in-one detection and treatment of bacterial infections. Notably, we highlight progress in the use of nanoparticles with intrinsic antibacterial performances, such as metals and metal oxide nanoparticles that are capable of killing bacteria and reducing the drug-resistance of bacteria through multiple antimicrobial mechanisms. In addition, we discuss nanomaterials that have been proven to be ideal drug carriers for the delivery and release of antimicrobials either in passive or in stimuli-responsive manners. Focus is given to nanomaterials with the ability to kill bacteria based on the photo-triggered heat (photothermal therapy) or ROS (photodynamic therapy), due to their unparalleled advantages in infection control. Moreover, we highlight examples of intelligent nanomaterial-based wound dressings that can detect bacterial infections in-situ while providing timely antibacterial therapy for enhanced management of infected wounds. Finally, we highlight challenges associated with the current nanomaterial-based wound dressings and provide further perspectives for future improvement of wound healing.

Nanostructured ionic hydrogel with integrated conductivity, stretchability and thermal responsiveness for a high-performance strain and temperature sensor.

Ionic conductive hydrogels are promising candidates for fabricating wearable sensors for human motion detection and disease diagnosis, and electronic skin. However, most of the existing ionic conductive hydrogel-based sensors primarily respond to a single-strain stimulus. Only a few ionic conductive hydrogels can respond to multiple physiological signals. Although some studies have explored multi-stimulus sensors, such as those detecting strain and temperature, the ability to identify the type of stimulus remains a challenge, which limits their applications. Herein, a multi-responsive nanostructured ionic conductive hydrogel was successfully developed by crosslinking the thermally sensitive poly(N-isopropylacrylamide-co-ionic liquid) conductive nanogel (PNI NG) with a poly(sulfobetaine methacrylate-co-ionic liquid) (PSI) network. The resultant hydrogel (PNI NG@PSI) was endowed with good mechanical stretchability (300%), resilience and fatigue resistance, and excellent conductivity (2.4 S m-1). Furthermore, the hydrogel exhibited a sensitive and stable electrical signal response and has a potential application in human motion detection. Moreover, the introduction of a nanostructured thermally responsive PNIPAAm network also endowed it with a sensitive and unique thermal-sensing ability to timely and accurately record temperature changes in the range of 30-45 °C, holding promise for application as a wearable temperature sensor to detect fever or inflammation in the human body. In particular, as a dual strain-temperature sensor, the hydrogel demonstrated an excellent capability of distinguishing the type of stimulus from superposed strain-temperature stimuli via electrical signals. Therefore, the implementation of the proposed hydrogel in wearable multi-signal sensors provides a new strategy for different applications, such as health monitoring and human-machine interactions.

A Polyaniline Nanoparticles Crosslinked Hydrogel with Excellent Photothermal Antibacterial and Mechanical Properties for Wound Dressing.

Antibacterial hydrogel wound dressing is highly desirable in wound healing and infection control. However, the development of antibacterial hydrogels with controllable antibacterial properties and adequate mechanical properties without bacterial resistance and potential toxicity remains a challenge. Herein, a double bonds-ended polyaniline nanoparticle (Me-PANI NP) is synthesized, which can convert light energy into heat upon near-infrared (NIR) irradiation, and it is used as a novel photothermal antibacterial agent. The obtained bonds-ended Me-PANI NPs are subsequently involved in polyacrylamide (PAM) polymerization and served as chemical crosslinking points to form the Me-PANI NPs@PAM hydrogel, endowing the hydrogel with controllable photothermal antibacterial abilities upon NIR irradiation without time and space limit. Importantly, due to the energy dissipation of Me-PANI NPs under stretch, the Me-PANI NPs@PAM hydrogel achieves a maximum stretching ratio of 400% mechanical flexibility. The developed hydrogel can be potentially applied as a novel wound dressing to realize controllable treatment of bacterial infections and accelerate skin wound healing.

A label-free ratiometric immunoassay using bioinspired nanochannels and a smart modified electrode.

Labeling with redox reporter is often required in developing electrochemical bioassay for most proteins or nucleic acid biomarkers. Herein, a label-free ratiometric immunosensing platform is firstly developed by integrating the antibody-conjugated nanochannels with a smart modified electrode. The electrode modifier is the composite of C60, tetraoctylammonium bromide (TOA+) and Prussian blue (PB). Cyclic voltammograms of the ultimate C60-TOA+/PB modified electrode exhibited two pairs of peaks at 0.15 V and -0.13 V, ascribing to the redox of PB and C60, respectively. With the addition of K3[Fe(CN)6] in the electrolyte solution, the peaks of PB decreased due to the adsorption of [Fe(CN)6]3- while the peaks of C60 increased because of the formation of the ternary complex (TC) C60-TOA+-[Fe(CN)6]3-. As a result, the peak current ratio IPB/ITC decreased gradually with the increment of the concentration of [Fe(CN)6]3-. For the nanochannels-based immunosensing platform, the steric hindrance of the bioconjugated nanochannels varied with the loading amount of the target CA125, and thus [Fe(CN)6]3- passing through the channels was quantitatively affected. And the higher CA125 level was, the less [Fe(CN)6]3- concentration was. And thus, the ratio IPB/ITC monitored at the C60-TOA+/PB modified electrode increased with the increase of the concentration of CA125. The ratiometric immunoassay featured a linear calibration range from 1.0 U mL-1 to 100 U mL-1 with a low detection limit of 0.86 U mL-1. In addition, the ratiometric immunosensing platform demonstrated good specificity and stability as well as acceptable accuracy in overcoming the effect of electrode passivation which was an inherent problem of electroanalysis.