Signal-On Near-Infrared Photoelectrochemical Aptasensors for Sensing VEGF165 Based on Ionic Liquid-Functionalized Nd-MOF Nanorods and In-Site Formation of Gold Nanoparticles.

The low photon energy and deep penetrating ability of near-infrared (NIR) light make it an ideal light source for a photoelectrochemical (PEC) immunosensing system. Absorption wavelengths of the metal-organic frameworks (MOFs) can be regulated by adjusting the metal ions and the conjugation degree of the ligands. Herein, an ionic liquid with a large conjugated structure was synthesized and was used as a ligand to coordinate with Nd ions to prepare Nd-MOF nanorods with a band gap of 1.26 eV. The Nd-MOF rods show a good photoabsorption property from 200 to 980 nm. A PEC platform was constructed by using Nd-MOF nanorods as the photoelectroactive element. A detachable double-stranded DNA labeled with alkaline phosphatase (ALP), which is specific to VEGF165, was immobilized onto the PEC sensing interface. After blocking unspecific active sites with bovine albumin, an NIR PEC aptasensing system was developed for VEGF165 detection. After being incubated in a mixture of VEGF165, l-ascorbic acid 2-phosphate (magnesium salt hydrate) (AAP), and chloroauric acid, the aptamers for VEGF165 were detached from the PEC aptasensing interface, thus resulting in the decrease of the charge-transfer resistance and the increase of the photocurrent response. The shedding of the aptamers also makes the ALP approach the electrode surface, thus catalyzing the reduction of AAP to produce ascorbic acid (AA). Subsequently, AA reduces in situ chloroauric acid to produce AuNPs on the Nd-MOF-based sensing interface. With the excellent conductivity and localized surface plasmon resonance effect, the AuNPs can accelerate the separation of electron-hole pairs generated from Nd-MOF nanorods, thus promoting the photoelectric conversion efficiency and achieving signal amplification. Under optimized conditions, the PEC responses were linearly related to the VEGF165 concentrations in the range of 0.01-100 ng mL-1 and exhibit a low detection limit of 3.51 pg mL-1 (S/N = 3). VEGF165 in human serum samples was detected by the NIR PEC aptasensor. Their concentrations were found to be well consistent with that obtained from ELISA. Furthermore, the PEC aptasensor demonstrated recoveries from 96.07 to 103.8%. The relative standard deviations were within 5%, indicating good accuracy and precision. The results further verify its practicability for clinical diagnosis.

A high performance dual-mode biosensor based on Nd-MOF nanosheets functionalized with ionic liquid and gold nanoparticles for sensing of ctDNA.

A dual-mode biosensor constructed based on photoelectrochemical (PEC) and electrochemical (EC) property was developed for assaying circulating tumor DNA (ctDNA), which is commonly used for triple-negative breast cancer diagnosis. Ionic liquid functionalized two-dimensional Nd-MOF nanosheets were successfully synthesized through a template-assisted reagent substituting reaction. Nd-MOF nanosheets integrated with gold nanoparticles (AuNPs) were able to improve photocurrent response and supply active sites for assembling sensing elements. To achieve selective detection of ctDNA, thiol-functionalized capture probes (CPs) were immobilized on the Nd-MOF@AuNPs modified glassy carbon electrode surface, thereby generating a "signal-off" photoelectrochemical biosensor for ctDNA under visible light irradiation. After the recognition of ctDNA, ferrocene-labeled signaling probes (Fc-SPs) were introduced into the biosensing interface. After hybridization between ctDNA and Fc-SPs, the oxidation peak current of Fc-SPs generated from square wave voltammetry can be employed as a "signal-on" electrochemical signal for ctDNA quantification. Under the optimized conditions, a linear relationship was obtained to the logarithm of ctDNA concentration in between 1.0 fmol L-1 to 10 nmol L-1 for the PEC model and 1.0 fmol L-1 to 1.0 nmol L-1 for the EC model. The dual-mode biosensor can provide accurate results for ctDNA assays, effectively eliminating the probable occurrence of false-positive or false-negative results in single-model assays. By switching DNA probe sequences, the proposed dual-mode biosensing platform can serve as a strategy for detecting other DNAs and possesses broad applications in bioassay and early disease diagnosis.

A near-infrared photoelectrochemical aptasensing system based on Bi2O2S nanoflowers and gold nanoparticles for high-performance determination of MCF-7 cells.

Circulating tumor cells (CTCs) are commonly considered as the major cause of tumor metastasis and can eventually lead to death. Therefore, developing a high-performance method for the determination of CTCs is very significant for promoting the cancer survival rate. Photoelectrochemical biosensing systems have been extensively investigated and applied for bioassays. Herein, Bi2O2S nanoflowers were successfully prepared through a simple one-step hydrothermal method. After being integrated with gold nanoparticles with a diameter of ∼45 nm, AuNPs/Bi2O2S nanocomposites were coated onto an ITO electrode surface to build a photoelectrochemical sensing platform which can be excited with near-infrared light to produce photocurrent response. Subsequently, mercapto-group functionalized aptamer (SH-Apt) was fixed onto the AuNPs/Bi2O2S/ITO surface. Due to the overexpress of MUC1 protein in the cell membrane, MCF-7 cells were specifically trapped on the SH-Apt/AuNPs/Bi2O2S/ITO surface. The introduce of MCF-7 cells lead to an obvious decrease on the photocurrent response. The photocurrent variation shows a satisfied linear relationship to the logarithm of MCF-7 cells concentration ranged from 50 to 6 × 105 cell mL-1. The detection limit obtained is 17 cell mL-1. The PEC biosensor shows excellent sensitivity, selectivity and stability for sensing MCF-7 cells, even for determining MCF-7 cells in clinical serum samples.

An Antibacterial and Anti-Oxidative Hydrogel Dressing for Promoting Diabetic Wound Healing and Real-Time Monitoring Wound pH Conditions with a NIR Fluorescent Imaging System.

The design and synthesis of multifunctional chitosan hydrogels based on polymerized ionic liquid and a near-infrared (NIR) fluorescent probe (PIL-CS) is a promising strategy, which not only prevents the transition from acute to chronic wounds, but also provides prompt measures regarding microenvironmental alterations in chronic wounds. PIL-CS hydrogel can real-time visualize wound pH through in vivo NIR fluorescent imaging and also feature the pH-responsive sustained drug release, such as antioxidant, to eliminate reactive oxygen species (ROS) and to boost diabetic wound healing. PIL-CS hydrogel is specific, sensitive, stable, and reversible in response to pH changes at the wound site. It, therefore, enables real-time monitoring for a dynamic pH change in the microenvironment of irregular wounds. PIL-CS hydrogel is also designed to possess many merits including high water containment and swelling rate, good biocompatibility, electrical conductivity, antifreeze, tissue adhesion, hemostatic performance, and efficient antibacterial activity against MRSA. In vivo studies showed that PIL-CS hydrogel provided fast diabetic wound healing support, promoted vascular endothelial growth factor (VEGF) production, and reduced ROS and tumor necrosis factor (TNF-α) generation. The results support that the hydrogels coupled with NIR fluorescent probes can be an excellent diabetic wound dressing for enhancing and real-time monitoring skin restoration and regeneration.

Dual-wavelength responsive photoelectrochemical aptasensor based on ionic liquid functionalized Zn-MOFs and noble metal nanoparticles for the simultaneous detection of multiple tumor markers.

A single tumor marker may correspond to a variety of diseases, and a specific disease requires the joint detection of multiple tumor markers for improving the accuracy of diagnoses. An ionic liquid-functionalized metal-organic framework (Zn-MOF microspheres) was used as the substrate to capture the aptamer (Ab1), and noble metal nanoparticles were used to label a signal aptamer (Ab2) to construct a dual-wavelength responsive sandwich-type photoelectrochemical (PEC) aptasensor. Due to the size effect, plasma resonance and the response of the noble metal nanoparticle enhancement system to different excitation wavelengths, the simultaneous detection of CEA and CA153 tumor markers was realized. Under the optimized conditions, CA153 and CEA at concentrations of 0.05-100 U mL-1 and 0.005-10 ng mL-1 were detected by the PEC aptasensor. Detection limits calculated for CA153 and CEA determinations were 0.0275 U mL-1 and 2.85 pg mL-1 (S/N = 3), respectively. CA153 and CEA in serum samples were detected by the PEC aptasensor, and their concentrations were well consistent with that obtained from the ELISA. In addition, the PEC aptasensor exhibited a recovery rate of 96.98%-103.4%, and a relative standard deviation of 1.1%-3.6%, indicating good practical value and accuracy, further confirming its potential for clinical diagnosis.