Dual‐fluorophore Raspberry‐like Nanohybrids for Ratiometric pH Sensing

We report on the development of raspberry‐like silica structures formed by the adsorption of 8‐hydroxypyrene‐1,3,6‐trisulfonate (HPTS)@silica nanoparticles (NPs) on rhodamine B isothiocyanate (RBTIC)@silica NPs for ratiometric fluorescence‐based pH sensing. To overcome the well‐known problem of dye leaching which occurs during encapsulation of anionic HPTS dye in silica NPs, we utilized a polyelectrolyte‐assisted incorporation of the anionic HPTS. The morphological and optical characterization of the as‐synthesized dye‐doped NPs and the resulting nanohybrids were carried out. The pH‐sensitive dye, HPTS, incorporated in the HPTS‐doped silica NPs provided a pH‐dependent fluorescence response while the RBITC‐doped silica provided the reference signal for ratiometric sensing. We evaluated the effectiveness of the nanohybrids for pH sensing; the ratio of the fluorescence emission intensity at 510 nm and 583 nm at excitation wavelengths of 454 nm and 555 nm, respectively. The results showed a dynamic response in the acidic pH range. With this approach, nanohybrids containing different dyes or receptors could be developed for multifunctioning and multiplexing applications.     

Current Advances in Quantum‐Dots‐Based Photoelectrochemical Immunoassays

As a newly developed technique, photoelectrochemical (PEC) immunoassays have attracted great attention in recent years because of their low cost and desirable sensitivity. Because the detection signal originates from the photoelectric conversion of photoelectric materials, the appearance and application of quantum dots (QDs), which possess unique photophysical properties and regulated optoelectronic characteristics, has taken the development of PEC immunoassays to new heights. This review concisely introduces the general mechanism of QDs‐based photoelectric conversion for immunoassays and summarizes the current advances in QD applications in immunoassays. Given that signal strategies and photoactive materials are the key elements in PEC biosensor systems, we comprehensively highlight the state‐of‐the‐art signaling strategies and various applications of QDs in PEC immunoassays to introduce advances in QDs‐based PEC immunoassays. Finally, challenges and future developmental trends are briefly discussed     

Towards ultra-responsive biodegradable polysaccharide humidity sensors

Sodium alginate is a biodegradable natural polymer that is derived from algae and is water soluble. Upon immersion in a CaCl₂ solution, a sodium alginate water solution is cross-linked to form water-insoluble calcium alginate. When the sodium alginate water solution is immersed in the CaCl₂ bath via a syringe pump, calcium alginate fibers are produced. By changing the CaCl₂ concentration, calcium alginate fibers with different degrees of cross-linking can be produced. Such fibers were found to differ in mechanical and morphological properties, and more interestingly, were found to possess humidity sensing and conductive properties. Interestingly, the higher the CaCl₂ concentration, the lower the degree of cross-linking, which produced softer fibers with better humidity sensing and conductive properties. The fibers were able to trap water in their structures, and a higher water content increased the conductivity due to the presence of an electrolyte salt in the fiber and due to the polyelectrolyte nature of the fiber itself. The cross-linking and percent shrinking degree, morphology and mechanical properties of the fibers were found to create significant changes in the conductivity and humidity sensing properties of the fibers. High humidity environments led to an increase in the conductivity of the fibers, whereas dry environments led to a decrease in the conductivity. The fibers, especially those with the highest CaCl₂ concentration, were determined to be ultra-responsive to humidity changes and exhibited very good repetition in humidity cycles. These tailored fibers are proposed as novel biodegradable conductive materials for various humidity sensing, robotic and bio-robotic applications.     

The Orange Side of Disperse Red 1: Humidity‐Driven Color Switching in Supramolecular Azo‐Polymer Materials Based on Reversible Dye Aggregation

Humidity detection, and the quest for low‐cost facile humidity‐sensitive indicator materials is of great interest for many fields, including semi‐conductor processing, food transport and storage, and pharmaceuticals. Ideal humidity‐detection materials for a these applications might be based on simple clear optical readout with no power supply, i.e.: a clear color change observed by the naked eye of any untrained observer, since it doesn't require any extra instrumentation or interpretation. Here, the introduction of a synthesis‐free one‐step procedure, based on physical mixing of easily available commercial materials, for producing a humidity memory material which can be easily painted onto a wide variety of surfaces and undergoes a remarkable color change (approximately 100 nm blue‐shift of λ_MAX) upon exposure to various thresholds of levels of ambient humidity is reported. This strong color change, easily visible to as a red‐to‐orange color switch, is locked in until inspection, but can then be restored reversibly if desired, after moderate heating. By taking advantage of spontaneously‐forming reversible ‘soft’ supramolecular bonds between a red‐colored azo dye and a host polymer matrix, a reversible dye ‘migration’ aggregation appearing orange, and dis‐aggregation back to red can be achieved, to function as the sensor.

     

酶生物燃料电池自供能传感器的研究现状及应用

在现代分析领域中,对于生物传感器的要求不断倾向于微型化和便捷化。基于酶型生物燃料电池的自供能传感器在检测目标物的同时可以提供能量,避免了外电源的使用,为生物传感器的微型化和便捷化发展提供了有效途径,日益成为人们关注的焦点。本文按照设计原理进行分类,对近五年内发展的基于酶型生物燃料电池的自供能传感器进行了综述,并展望了其今后的研究趋势和应用前景。     

Electrochemical Determination of Label Free BRCA Hybridization by Single Use Antioxidant Modified Electrode

A novel DNA probe based on caffeic acid modified disposable pencil graphite electrodes were developed for the first time for the electrochemical determination of breast cancer gene sequence (BRCA) hybridization. Amino‐linked BRCA probe highly immobilized onto the caffeic acid modified electrode by means of the interaction between the amino group of BRCA probe and the carboxyl group of caffeic acid compared to the bare electrode. 44 % signal enhancement in guanine oxidation signal was measured by caffeic acid modified electrode. Besides, these probes exhibited high selectivity towards its complementary DNA sequences (target). Hybridization between probe and target (BRCA1) was studied to evaluate the selectivity of the probes for complementary, non‐complementary and mismatch sequences. The selectivity was also tested in the presence of mixture containing the target and one base mismatch BRCA sequences in the same ratio (1 : 1). It can be said this probe can select its complementary from the mixture.     

Incorporation of Tetrazolium Blue (TB)/Gold Nanoparticles (GNPs) into Carbon Paste Electrode: Application as an Electrochemical Sensor for the Sensitive and Selective Determination of Sotalol in Micellar Medium

The electrochemical oxidation of Sotalol (SOT) based on Tetrazolium Blue (TB)/gold nanoparticles (GNPs)‐modified carbon paste electrodes (CPE) have been studied in the presence of sodium lauryl sulphate (SLS). Cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques have all been utilized within this study. GNPs and TB have a synergetic effect‐giving rise to highly improved electrochemical responses and provide an advantageous platform for the basis of an electrochemical sensor with excellent performance. The experimental parameters, electrodeposition time, pH and scan rate have all been examined and optimized. The sensing of SOT via DPV is found to exhibit a wide linear dynamic range of 1.0×10⁻⁷–7.5×10⁻⁴ M in pH 2. LOD and LOQ were calculated and found to correspond to 2.5×10⁻⁸ M and 8.3×10⁻⁸ M, respectively. The suggested sensor has been used successfully for SOT determination in pharmaceutical samples and human urine as real samples. Satisfactory recoveries of analyte from these samples are demonstrated indicating that the suggested sensor is highly suitable for clinical analysis, quality control and a routine determination of SOT in pharmaceutical formulations.     

Electrochemical Motion Tracking of Microorganisms Using a Large-Scale-Integration-Based Amperometric Device

Motion tracking of microorganisms is useful to investigate the effects of chemical or physical stimulation on their biological functions. Herein, we describe a novel electrochemical imaging method for motion tracking of microorganisms using a large-scale integration (LSI)-based amperometric device. The device consists of 400 electrochemical sensors with a pitch of 250 μm. A convection flow caused by the motion of microorganisms supplies redox species to the sensors and increases their electrochemical responses. Thus, the flow is converted to electrochemical signals, enabling the electrochemical motion tracking of the microorganisms. As a proof of concept, capillary vibration was monitored. Finally, the method was applied to monitoring the motion of Daphnia magna. The motions of these microorganisms were clearly tracked based on the electrochemical oxidation of [Fe(CN)₆]⁴⁻ and reduction of O₂.     

A Simple Post-Polymerization Modification Method for Controlling Side-Chain Information in Digital Polymers

A three-step post-polymerization modification method was developed for the design of digitally encoded poly(phosphodiester)s with controllable side groups. Sequence-defined precursors were synthesized, either manually on polystyrene resins or automatically on controlled pore glass supports, using two phosphoramidite monomers containing either terminal alkynes or triisopropylsilyl (TIPS) protected alkyne side groups. Afterwards, these polymers were modified by stepwise copper-catalyzed azide–alkyne cycloaddition (CuAAC). The terminal alkynes were first reacted with a model azide compound, and after removal of the TIPS groups, the remaining alkynes were reacted with another organic azide. This simple method allows for quantitative side-chain modification, thus opening up interesting avenues for the preparation of a wide variety of digital polymers.     

Multiple Hydrogen Bonding Enables the Self-Healing of Sensors for Human–Machine Interactions

Despite its widespread use in signal collection, flexible sensors have been rarely used in human–machine interactions owing to its indistinguishable signal, poor reliability, and poor stability when inflicted with unavoidable scratches and/or mechanical cuts. A highly sensitive and self-healing sensor enabled by multiple hydrogen bonding network and nanostructured conductive network is demonstrated. The nanostructured supramolecular sensor displays extremely fast (ca. 15 s) and repeatable self-healing ability with high healing efficiency (93 % after the third healing process). It can precisely detect tiny human motions, demonstrating highly distinguishable and reliable signals even after cutting–healing and bending over 20 000 cycles. Furthermore, a human–machine interaction system is integrated to develop a facial expression control system and an electronic larynx, aiming to control the robot to assist the patient's daily life and help the mute to realize real-time speaking.