Free-standing electrochemical biosensor for carcinoembryonic antigen detection based on highly stable and flexible conducting polypyrrole nanocomposite.

A flexible free-standing electrochemical biosensor to detect carcinoembryonic antigen (CEA) is described based on a conducting polypyrrole (PPy) nanocomposite film electrode. The conducting PPy composite was constructed by the sandwiched structure formed by PPy doped with pentaerythritol ethoxylate (PEE) and 2-naphthalene sulfonate (2-NS-PPy) separately via electropolymerization. Gold nanoparticles (AuNPs) were fixed on the PPy composite film by electrodeposition and then connected to CEA aptamer through self-assembly to construct a free-standing electrochemical biosensor breaking away from additional soft substrates and current collector. This PPy composite film-based electrochemical biosensor exhibits satisfying sensing performance for CEA detection, with a linear range from 10-10 g/mL to 10-6 g/mL and a detection limit of 0.033 ng/mL, good specificity and long-term sensing stability (96.8% of the original signal after 15 days). The biosensor also presents acceptable reproducibility with 1.7% relative standard deviation. Moreover, this electrochemical biosensor owns the deformation stability that could bear various deformations (twisting, folding, and knotting) without affecting device's sensing performance. It can even maintain 99.4% of the original signal under 25% strain deformation. Due to the superior sensing performance, high stability (mechanical deformation and long-term storage), and flexibility, this free-standing electrochemical biosensor proves huge potential in application of flexible and wearable electronics.

A nanocomposite consisting of MnO2 nanoflowers and the conducting polymer PEDOT for highly sensitive amperometric detection of paracetamol.

An electrochemical sensor for paracetamol is described that consists of a glassy carbon electrode (GCE) that was modified with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with MnO2 nanoflowers. The hydrothermally synthesized MnO2 nanoflowers possess a large surface area and can be doped into PEDOT through electrochemical deposition to form a conducting polymer nanocomposite. The nanoflowers are shown to be uniformly distributed within the nanocomposite as revealed by elemental mapping analysis. The nanocomposite displays excellent catalytic activity toward the electrochemical oxidation of paracetamol. The modified GCE, best operated at a working potential of around 0.37 V (vs. SCE) has a linear response in 0.06 to 435 µM paracetamol concentration range and a very low limit of detection (31 nM at a signal-to-noise ratio of 3). The sensor exhibits excellent reproducibility and stability, and satisfying accuracy for paracetamol detection in pharmaceutical samples. Graphical abstract A highly sensitive electrochemical sensor capable of detecting paracetamol with a limit of detection down to 31 nM was developed based on MnO2 nanoflowers doped conducting polymer PEDOT.

Trimethylated chitosan-coated flexible liposomes with resveratrol for topical drug delivery to reduce blue-light-induced retinal damage.

LED-related blue-light-induced damage can cause eye diseases. However, drug delivery in patients with ocular diseases is faced with various challenges. In this study, we developed flexible liposomes based on trimethylated chitosan (TMC-Lipo) to deliver resveratrol for the treatment of retinal diseases. Flexible liposomes can easily cross various biological barriers. Chitosan and its derivatives have adhesive properties and are widely used in mucoadhesive drug delivery systems. Therefore, we wrapped flexible liposomes with trimethylated chitosan via electrostatic adsorption. The charge of the flexible liposomes became positive after encapsulation in TMC, and they remained stable in artificial tears. We assessed the safety of TMC-Lipo in cellular and zebrafish experiments and found that it can be safely used. In addition, treatment with TMC-Lipo significantly reduced H2O2-induced damage to ARPE-19 cells, restored mitochondrial membrane potential, and protected the cells. TMC-Lipo more easily reached the posterior ocular segment of the mice than liposome nanoparticles and attenuated blue-light-induced retinal cytopathy. Our study demonstrates that effective eye drop formulations can be developed based on trimethylated chitosan, which provides a promising approach for the treatment of ocular diseases.

Self-Healing Ti3C2 MXene/PDMS Supramolecular Elastomers Based on Small Biomolecules Modification for Wearable Sensors.

Flexible conductive composites can be used as wearable strain sensors, which are widely used in the fields of new-generation robotics, electronic skin, and human detection. However, how to make conductive composites that simultaneously possess flexibility, stretchability, self-healing, and sensing capability is challenging research. In this work, we innovatively designed and prepared a silicone polymer conductive composite. MXenes and amino poly(dimethylsiloxane) were modified by small biomolecules via an esterification reaction and a Schiff base reaction, respectively. The modified MXenes are uniformly dispersed, which endows the composite with good electrical conductivity. The reversibility of multiple hydrogen bonds and imine bonds in the composite system makes it have ideal tensile properties and high-efficiency self-healing ability without external stimulation. The conductive composite containing 10 wt % A-MXenes showed an elongation of 81%, and its mechanical strength could reach 1.81 MPa. After repair, the tensile properties and the electrical conductivity could be restored to 98.4 and 97.6%, respectively. In addition, the conductive composite is further evaluated for the value of wearable strain sensors. Even after cut-healed processes, the conductive composite can still accurately detect tiny human movements (including speaking, swallowing, and pressing). This kind of self-healing MXene/PDMS elastomers based on the modification of small biomolecules has great potential as wearable strain sensors. This simple preparation method provides guidance for future multifunctional flexible electronic materials.