Cation Exchange Reaction-Mediated Photothermal and Polarity-Switchable Photoelectrochemical Dual-Readout Biosensor

Abstract

Cation exchange (CE) is a burgeoning method for controlled crystal synthesis; however, its applications in bioanalysis are still in their infancy. Herein, we explored the transformation of ZnIn 2 S 4 in properties after the CE reaction with Cu 2+ ions; furthermore, the discrepancy was employed to design a dual-readout detection system of photothermal and polarity-switchable photoelectrochemical (PEC) immunoassays to realize reliable detection of carcinoembryonic antigen (CEA). In the presence of CEA, the CuO nanoparticles (CuO NPs) employed as dual-signal response probes would bond to the microplates and be acidolyzed by HCl to release Cu 2+ , which could replace Zn 2+ and In 3+ via the CE reaction. After the CE reaction is completed, the photocurrent would switch from a weak anodic photocurrent to a cathode one by using a 635 nm laser as a signal amplifier, while the photothermal signal would be enhanced with 808 nm laser illumination. On the basis of the polarity-switchable PEC strategy, CEA could be accurately detected from 0.1 to 50 ng mL −1 with a limit of detection (LOD) of 48 pg mL −1 (S/N = 3). Moreover, the photothermal assay for CEA detection possesses a linear range from 0.5 to 100 ng mL −1 with a LOD of 0.21 ng mL −1 . In addition, the designed sensing platform only relies on devices with portability that are permitted for point-of-care detection.

Integrated Sandwich-Paper 3D Cell Sensing Device to In Situ Wirelessly Monitor H2O2 Released from Living Cells

“…The peak with a binding energy of 645.5 eV is the 2p orbital satellite peak of Mn . The Mn 2p 3/2 and Mn 2p 1/2 with binding energies at 641.1 and 653.7 eV are from Mn 2+ , while the peaks at 642.6 and 655.8 eV are from Mn 3+ . This result indicates that Mn 2+ and Mn 3+ coexist in the nanocomposites, which is consistent with Fe.…”

“…The current–time responses of the sensing device to H 2 O 2 were recorded every 50 s by adding 200 μM H 2 O 2 at −0.85, −0.90, and −0.95 V, respectively (Figure S7). The maximum amperometric response was obtained at a potential of −0.90 V. For real-time detection of H 2 O 2 , I – t measurements were conducted by successive adding 2 μM (Figure C), 20 μM (Figure D), and 200 μM H 2 O 2 (Figure S8) over a wide range of 2–3200 μM H 2 O 2 at an applied potential of −0.90 V. The low detection limit of the sensing device is 0.4 μM, which is calculated to be 3 times the signal-to-noise ratio. , The sensitivity of this device is 113.2 μA mM –1 cm –2 (2–20 μM), 2.6 μA mM –1 cm –2 (20–200 μM), and 1.3 μA mM –1 cm –2 (200–3200 μM) based on the surface area of the electrode and the slope of the current–dose response curve. After adding 50 μM H 2 O 2 , the fabricated sensing device reaches a steady-state current within 0.2 s, exhibiting a fast response time (Figure E).…”

Tyramine-Invertase Bioconjugate-Amplified Personal Glucose Meter Signaling for Ultrasensitive Immunoassay

“…The corresponding linear equation is ΔGMS = 3.105 + 2.021 log C CEA (pg/mL) with a correlation coefficient of 0.9950. The detection limit of CEA was estimated as 41.55 fg/mL (∼0.208 fM) according to the 3σ criterion . To verify the reproducibility of the method, the relative standard deviation (RSD) was calculated as 3.17% by seven parallel measurements of 10 pg/mL CEA.…”

Oxygen Vacancies-Induced Antifouling Photoelectrochemical Aptasensor for Highly Sensitive and Selective Determination of α-Fetoprotein

“…Photoelectrochemical (PEC) sensing is expected to achieve accurate determination of AFP in urine due to the “ light excitation, electrical detection” mode, which has the advantages of low background noise, high sensitivity, and simple equipment. − However, low charge transfer efficiency and high photogenerated electron–hole recombination efficiency limit the sensitivity of TiO 2 -based biosensors. Oxygen vacancy (OV) modulation strategy is an effective method to further improve the sensitivity and fouling resistance of the sensor. , The introduction of OVs induces the formation of intermediate localized states in photoelectric material, which not only facilitates the separation of photogenerated carriers but also leads to the redshift of photoabsorption. − For example, Yu et al have reported an OVs-modulated SnO 2 nanotube (SnO 2– x ) with visible light response for AFP detection. SnO 2– x showed a redshift of the light absorption edge from 380 nm to about 500 nm.…”