Self-Referenced Smartphone Imaging for Visual Screening of H₂S Using Cu_<i>x</i>O‑Polypyrrole Conductive Aerogel Doped with Graphene Oxide Framework

Cu_<i>x</i>O-polypyrrole conductive aerogel loaded on graphene oxide framework (Cu_<i>x</i>O-PPy@GO) with a three-dimensional (3D) porous architecture was utilized for high-efficient visual screening of H₂S on a flexible paper substrate. The detectable signal was acquired on a portable smartphone by using a self-referenced imaging platform equipped with the light emitting diode (LED) accompanying an image processing. As a proof-of-concept, Cu_<i>x</i>O-PPy@GO aerogel-based sensing strategy was also developed for Na₂S detection and egg spoilage monitoring. Such a flexible paper-supported sensor is expected for potential application in portable and wearable food-safety fields

Self-Referenced Smartphone Imaging for Visual Screening of H₂S Using Cu_<i>x</i>O‑Polypyrrole Conductive Aerogel Doped with Graphene Oxide Framework

Cu_<i>x</i>O-polypyrrole conductive aerogel loaded on graphene oxide framework (Cu_<i>x</i>O-PPy@GO) with a three-dimensional (3D) porous architecture was utilized for high-efficient visual screening of H₂S on a flexible paper substrate. The detectable signal was acquired on a portable smartphone by using a self-referenced imaging platform equipped with the light emitting diode (LED) accompanying an image processing. As a proof-of-concept, Cu_<i>x</i>O-PPy@GO aerogel-based sensing strategy was also developed for Na₂S detection and egg spoilage monitoring. Such a flexible paper-supported sensor is expected for potential application in portable and wearable food-safety fields

ZIF-8-Assisted NaYF4:Yb,Tm@ZnO Converter with Exonuclease III-Powered DNA Walker for Near-Infrared Light Responsive Biosensor

This work reports a ZIF-8 (ZIF: Zeolitic Imidazolate Framework)-assisted NaYF4:Yb,Tm@ZnO upconverter for the photoelectrochemical (PEC) biosensing of carcinoembryonic antigen (CEA) under near-infrared (NIR) irradiation on a homemade 3D-printed device with DNA walker-based amplification strategy. The composite photosensitive material NaYF4:Yb,Tm@ZnO, as converter to transfer NIR import to photocurrent output, was driven from annealed NaYF4:Yb,Tm@ZIF-8. Yb3+ and Tm3+-codoped NaYF4 (NaYF4:Yb,Tm) converted NIR excitation into UV emission, matching with the absorption of ZnO for in situ excitation to generate the photocurrent. Upon target CEA introduction, the swing arm of DNA walker including the sequence of CEA aptamer carried out the sandwiched bioassembly with CEA capture aptamer on the G-rich anchorage DNA tracks-functionalized magnetic beads. Thereafter, DNA walker was triggered, and the swing arm DNA was captured by the G-rich anchorage DNA according to partly complementary pairing and Exonuclease III (Exo III) consumed anchorage DNA by a burnt-bridge mechanism to go into the next cycle. The released guanine (G) bases from DNA walker enhanced the photocurrent response on a miniature homemade 3D-printed device consisting of the detection cell, dark box, and light platform. Under optimal conditions, NaYF4:Yb,Tm@ZnO-based NIR light-driven PEC biosensor presented high sensitivity and selectivity for CEA sensing with a detection limit of 0.032 ng mL–1. Importantly, our strategy provides a new horizon for the development of NIR-based PEC biosensors in the aspect of developing MOF-derived photoelectric materials, flexible design of a 3D-printed device, and effective signal amplification mode

Ultrasensitive Aptamer-Based Multiplexed Electrochemical Detection by Coupling Distinguishable Signal Tags with Catalytic Recycling of DNase I

This work reports an aptamer-based, disposable, and multiplexed sensing platform for simultaneous electrochemical determination of small molecules, employing adenosine triphosphate (ATP) and cocaine as the model target analytes. The multiplexed sensing strategy is based on target-induced release of distinguishable redox tag-conjugated aptamers from a magnetic graphene platform. The electronic signal of the aptasensors could be further amplified by coupling DNase I with catalytic recycling of self-produced reactants. The assay was based on the change in the current at the various peak potentials in the presence of the corresponding signal tags. Experimental results revealed that the multiplexed electrochemical aptasensor enabled the simultaneous monitoring of ATP and cocaine in a single run with wide working ranges and low detection limits (LODs: 0.1 pM for ATP and 1.5 pM for cocaine). This concept offers promise for rapid, simple, and cost-effective analysis of biological samples

Saw-Toothed Microstructure-Based Flexible Pressure Sensor as the Signal Readout for Point-of-Care Immunoassay

A saw-toothed microstructure-based flexible pressure sensor was designed as the signal readout for point-of-care (POC) immunoassay of carcinoembryonic antigen (CEA). In this portable POC bioassay, the sandwich-type immunoreaction was first carried out to capture the target on a microplate, which simultaneously introduced the platinum nanoparticles (PtNPs). Upon adding hydrogen peroxide (H2O2), the pressure as the bridge between the molecular recognition event and detectable signal was increasing rapidly, resulting from the decomposition of H2O2 accelerated by PtNPs. Meanwhile, a flexible pressure sensor was fabricated with high sensitivity; the ability of the pressure response was dramatically improved by adopting the saw-toothed microstructure. By coupling with the pressure sensor, the pressure change could be monitored in real time to achieve the portable detection of CEA. Under the optimum conditions, the proposed pressure-based bioassay presented good sensing performance within 0.1–40 ng/mL at a detection limit of 87 pg/mL. The reproducibility, precision, and accuracy provided by the method were also studied and satisfied

Liposome-Mediated <i>In Situ</i> Formation of Type‑I Heterojunction for Amplified Photoelectrochemical Immunoassay

Exploiting innovative sensing mechanisms and their rational implementation for selective and sensitive detection has recently become one of the mainstream research directions of photoelectrochemical (PEC) bioanalysis. In contrast to existing conventional strategies, this study presents a new liposome-mediated method via in situ combining ZnInS nanosheets (ZIS NSs) with SnS2 to form a ZIS NSs/SnS2 type-I heterojunction on fluorine-doped tin oxide (FTO) electrodes for highly sensitive PEC immunoassays. Specifically, alkaline phosphatase (ALP)-encapsulated liposomes were confined within 96-well plates by sandwich immunorecognition and subsequently subjected to lysis treatment. Enzymatically produced H2S by the released ALP was then directed to react with Sn­(IV) to engender the ZIS NSs/SnS2 type-I heterojunction on the FTO/ZIS NSs-Sn­(IV) electrode, resulting in a change in the photogenerated electron–hole transfer path of the photoelectrode and reduction in current signaling. Exemplified by heart-type fatty acid binding protein (h-FABP) as a target, the constructed PEC sensor showed good stability and selectivity in a biosensing system. Under optimal conditions, the as-prepared sensing platform displayed high sensitivity for h-FABP with a dynamic linear response range of 0.1–1000 pg/mL and a lower detection limit of 55 fg/mL. This research presents the liposome-mediated PEC immunoassay based on in situ type-I heterojunction establishment, providing a new protocol for analyzing various targets of interest