Distinguishable Magnetic Reporter Coordination with Buoyancy-Magnetism Separation for Immobilization-Free Dual-Target Electrochemical Immunosensing.

Simultaneous sensitive and precise determination of multibiomarkers is of great significance for improving detection efficiency, reducing diagnosis and treatment expenses, and elevating survival rates. However, the development of simple and portable biosensors for simultaneous determination of multiplexed targets in biological fluids still faces challenges. Herein, a unique and versatile immobilization-free dual-target electrochemical biosensing platform, which combines distinguishable magnetic signal reporters with buoyancy-magnetism separation, was designed and constructed for simultaneous detection of carcinoembryonic (CEA) and α-fetoprotein (AFP) in intricate biological fluids. To construct such distinguishable magnetic signal reporters with signal transduction, amplification, and output, secondary antibodies of CEA and AFP were respectively functionalized on methylene blue (MB) and 6-(ferrocenyl)hexanethiol (FeC) modified Fe3O4@Au magnetic nanocomposites. Meanwhile, a multifunctional flotation probe with dual target recognition, capture, and isolation capability was prepared by conjugating primary antibodies (Ab1-CEA, Ab1-AFP) to hollow buoyant microspheres. The target antigens of CEA and AFP can trigger a flotation-mediated sandwich-type immunoreaction and capture a certain amount of the distinguishable magnetic signal reporter, which enables the conversion of the target CEA and AFP quantities to the signal of the potential-resolved MB and FeC. Thus, the MB and FeC currents of magnetically adsorbed distinguishable magnetic reporters can be used to determine the CEA and AFP targets simultaneously and precisely. Accordingly, the proposed strategy exhibited a delightful linear response for CEA and AFP in the range of 100 fg·mL-1-100 ng·mL-1 with detection limits of 33.34 and 17.02 fg·mL-1 (S/N = 3), respectively. Meanwhile, no significant nonspecific adsorption and cross-talk were observed. The biosensing platform has shown satisfactory performance in the determination of real clinical samples. More importantly, the proposed approach can be conveniently extended to universal detection just by simply substituting biorecognition events. Thus, this work opens up a new promising perspective for dual and even multiple targets and offers promising potential applications in clinical diagnosis.

A perylene diimide electrochemical probe with persulfate as a signal enhancer for dopamine sensing.

Dopamine (DA) is an important biomarker related to parkinsonism, schizophrenia and renal disease. Traditional electrochemical sensors for DA were based on the direct electrochemical oxidation of DA. In this paper, we report a new sensing strategy using N,N'-di(trimethylaminoethyl)perylene diimide (TMPDI) as an electrochemical probe and K2S2O8 as a signal enhancer for DA detection between 0 and -0.7 V with the DPV technique. MoS2 nanoflowers prepared by the hydrothermal method were used as a nanocarrier to load TMPDI. The reduction current of TMPDI was found to show a stepwise and significant increase at -0.24 V with the increase of concentration of K2S2O8 due to the continuous cycle of TMPDI molecules' electrochemical reduction and chemical oxidation. The presence of DA caused a large decrease of the reduction current of TMPDI due to the synergistic interaction of the competitive consumption of DA for K2S2O8 and the blocking effect of polyDA adhering to the electrode surface. The decreased current exhibited a linear response for DA from 10 pM to 100 µM with a detection limit of 4.1 pM and the proposed sensor showed high selectivity and excellent feasibility in human urine/serum sample detection.

A novel dual-signal output strategy for POCT of CEA based on a smartphone electrochemical aptasensing platform.

A smartphone-based electrochemical aptasensing platform was developed for the point-of-care testing (POCT) of carcinoembryonic antigen (CEA) based on the ferrocene (Fc) and PdPt@PCN-224 dual-signal labeled strategy. The prepared PdPt@PCN-224 nanocomposite showed a strong catalytic property for the reduction of H2O2. Phosphate group-labeled aptamer could capture PdPt@PCN-224 by Zr-O-P bonds to form PdPt@PCN-224-P-Apt. Therefore, a dual signal labeled probe was formed by the hybridization between Fc-DNA and PdPt@PCN-224-P-Apt. The presence of CEA forced PdPt@PCN-224-P-Apt to leave the electrode surface due to the specific affinity, leading to the decrease of the reduction current of H2O2. At the same time, the Fc-DNA strand changed to hairpin structure, which made Fc closer to the electrode and resulted in the increase of the oxidation current of Fc. Thus, CEA can be accurately determined through both signals: the decrease of H2O2 reduction current and the increase of Fc oxidation current, which could avoid the false positive signal. Under the optimal conditions, the prepared aptasensor exhibited a wide linear range from 1 pg·mL-1 to 100 ng·mL-1 and low detection limits of 0.98 pg·mL-1 and 0.27 pg·mL-1 with Fc and PdPt@PCN-224 as signal labels, respectively. The aptasensor developed in this study has successfully demonstrated its capability to detect CEA in real human serum samples. These findings suggest that the proposed sensing platform will hold great potential for clinical tumor diagnosis and monitoring.

Fascinating Immobilization-Free Electrochemical Immunosensing Strategy Based on the Cooperation of Buoyancy and Magnetism.

Rapid and accurate detection of biomolecules is of vital importance for the diagnosis of disease and for performing timely treatments. The point-of-care analysis of cancer biomarkers in the blood with low cost and easy processing is still challenging. Herein, an advanced and robust strategy, which integrates the buoyant recognition probe with the magnetic reporter probe in one solution, was first proposed for immobilization-free electrochemical immunosensing. The tumor marker of alpha fetoprotein (AFP) can be captured immune-buoyantly, and then a multifunctional magnetic reporter probe in pseudo-homogeneous solution was further captured to fulfill a sandwich-type immunoreaction. The residual magnetic reporter probe can be firmly and efficiently attracted on a magnetic glassy carbon electrode to fulfill the conversion of the target AFP amount into the residual magnetic electrochemical signal indicator. As a result, the electrochemical signal of methylene blue can accurately reflect the original level of target antigen AFP concentration. By integrating buoyancy-driven quasi-homogenous biorecognition with magnetism-mediated amplification and signal output, the proposed immobilization-free electrochemical immunosensing strategy displayed a wide range of linear response (100 fg mL-1 to 10 ng mL-1), low detection limit (14.52 fg mL-1), and good reproducibility, selectivity, and stability. The designed strategy manifests remarkable advantages including assay simplicity, rapidness, and high sensitivity owing to the in-solution instead of on-electrode biorecognition that could accelerate and improve the biorecognition efficiency. To the best of our knowledge, this is the first cooperation of buoyancy-driven biorecognition with magnetism-mediated signal output in bioanalysis, which would be attractive for rapid clinic biomedical application. Thus, this work provides a fresh perspective for convenient and favorable immobilization-free electrochemical biosensing of universal biomolecules.

A label-free electrochemical aptasensor based on Bi-Sb alloy materials for potential POCT of HER-2.

As a prognostic biomarker for breast cancer, human epidermal growth factor receptor 2 (HER-2) is of crucial diagnostic value. Here, a label-free electrochemical aptasensor was established for the ultrasensitive detection of HER-2 using a modified electrode of Bi-Sb alloy materials (Bi-Sb AMs). The performance of the aptasensor was enhanced greatly due to the introduction of Bi-Sb alloy materials (Bi-Sb AMs) with high conductivity. Furthermore, by integrating the aptasensor with the Sensit Smart U-disk electrochemical analyzer, the point-of-care testing (POCT) for HER-2 was realized. Under the optimal experimental parameters, the POCT analyzer showed a wide linear response from 0.01 pg mL-1 to 100 ng mL-1, with a low detection limit (LOD) of 5.96 fg mL-1 for the detection of HER-2. The presented POCT analyzer exhibited good specificity, stability, and reproducibility. Benefiting from the simple operation and rapid testing, the developed analyzer will have potential application in the prognostic diagnosis and treatment of breast cancer.

Tungsten-based polyoxometalate nanoclusters with remarkable reactive oxygen species-scavenging activity efficiently quenched luminol-based electrochemiluminescence for sensitive detection of Her-2.

This study aimed to develop a quenching-type electrochemiluminescence (ECL) immunosensor for human epidermal growth factor receptor (Her-2) detection. Firstly, Pd/NiFeOx nanoflowers decorated by in situ formation of gold nanoparticles (Au NPs) and 2D Ti3C2 MXene nanosheets were synthesized (AuPd/NiFeOx/Ti3C2) as carriers to load luminol and primary antibodies. Impressively, AuPd/NiFeOx/Ti3C2 with excellent peroxidase-like activity could accelerate the decomposition of the coreactant H2O2 generating more reactive oxygen species (ROSs) under the working potential from 0 to 0.8 V, resulting in highly efficient ECL emission at 435-nm wavelengths. The introduction of tungsten-based polyoxometalate nanoclusters (W-POM NCs) which exhibit remarkable ROSs-scavenging activity as secondary antibody labels could improve the sensitivity of immunosensors. The ZnO nanoflowers were employed to encapsulate minute-sized W-POM NCs, and polydopamine was self-polymerized on the surface of Zn(W-POM)O to anchor secondary antibodies. The mechanism of the quenching strategy was explored and it was found that W-POM NCs could consume ROSs by the redox reaction of W5+ resulting in W6+. The proposed ECL immunosensor displayed a wide linear response range of 0.1 pg·mL-1 to 50 ng·mL-1, and a low detection limit of 0.036 pg mL-1 (S/N = 3). The recoveries ranged from 93.9 to 99.4%, and the relative standard deviation (RSD) was lower than 10%. This finding is promising for the design of detecting new protein biomarkers.

Ratiometric Electrochemiluminescence Sensing of Carcinoembryonic Antigen Based on Luminol.

Ratiometric electrochemiluminescence (ECL) sensors can efficiently remove environmental interference to attain precise detection. Nonetheless, two eligible luminophores or coreactants were usually needed, increasing the complexity and restricting their practical application. In this study, a single luminophore of luminol with a single coreactant of H2O2 was employed to construct a dual-potential ratiometric ECL sensor for the detection of carcinoembryonic antigen (CEA). The produced palladium nanoclusters (Pd NCs) employing a DNA duplex as a template could not only stimulate luminol to produce cathodic ECL (Icathodic) but also quench its anodic ECL (Ianodic). During the detection process, CEA could damage the double-stranded structure and reduce the Pd NCs' amount, triggering a significant decrease in the ratio of Icathodic to Ianodic (Icathodic/Ianodic) and thereby achieving sensitive CEA's detection. Furthermore, the Icathodic/Ianodic was independent of the H2O2 concentration, which avoided a prejudicial effect from H2O2 decomposition and considerably enhanced the detection's reliability. The developed ratiometric ECL sensor demonstrated a sensitive detection toward CEA with a wide linear range from 100 ag/mL to 10 ng/mL and a detection limit of 87.1 ag/mL (S/N = 3). In conclusion, this study offers a new idea for constructing ratiometric ECL sensors based on a single luminophore and technical support for cancer's early diagnosis.

Latissimus Dorsi Muscle Flap for Scalp Reconstruction and Postoperative Ulceration Management.

ABSTRACT: The latissimus dorsi muscle (LDM) flap has been widely accepted as the best choice for subtotal or total scalp reconstruction. Because of the unique anatomic and functional features of scalp, ulcerations formation would occur after reconstructive surgeries. in this study, we are presenting a patient with a large scalp defect successfully reconstructed by a latissimus dorsi muscle free flap. Ulcerations with skull exposure formed on the transplanted flap after the first surgery. They were subsequently repaired by flap recycling and tissue expansion techniques. An excellent reconstructive outcome was achieved at the 30-month follow-up after the last surgery and no further complication was found. This clinical report highlights the possibility of ulcer formation after scalp reconstructive surgeries and supports the use of recycle flaps and tissue expanders to manage postoperative ulcerations after latissimus dorsi muscle free flap transplantation.

Reconstruction of Severe Neck Scar Contracture After Electrical Injury.

ABSTRACT: High-voltage (≥1000 V) electrical injury is always related to high mortality and poor prognosis. The incidence rates of the high-voltage electrical injuries of the neck are lower than those of the other parts of the body. This article reports a case of the reconstruction of severe neck scar contracture after electrical injury. Compared with cases of scar contractures caused by nonelectrical injuries, this case had the following remarkable characteristics: extremely severe difficult airway, contracture scars involving whole layers of tissue, muscle and nerve damage, mandibular retraction, and poor occlusal relationship. The chief complaints of the patient upon admission, including forced position and continuous salivation, were greatly relieved through several operations by using different kinds of flaps and offering support to the flap from the palmar tendon and relocated mandible. However, the problem of salivation was incompletely solved. This problem might be caused by damage to related nerves and masticatory muscle function caused by high-voltage electrical injury. The patient was satisfied with the recovery of his appearance and movement function.

Highly Sensitive Adsorption and Detection of Iodide in Aqueous Solution by a Post-Synthesized Zirconium-Organic Framework.

Effective methods of detection and removal of iodide ions (I-) from radioactive wastewater are urgently needed and developing them remains a great challenge. In this work, an Ag+ decorated stable nano-MOF UiO-66-(COOH)2 was developed for the I- to simultaneously capture and sense in aqueous solution. Due to the uncoordinated carboxylate groups on the UiO-66-(COOH)2 framework, Ag+ was successfully incorporated into the MOF and enhanced the intrinsic fluorescence of MOF. After adding iodide ions, Ag+ would be produced, following the formation of AgI. As a result, Ag+@UiO-66-(COOH)2 can be utilized for the removal of I- in aqueous solution, even in the presence of other common ionic ions (NO2-, NO3-, F-, SO42-). The removal capacity as high as 235.5 mg/g was calculated by Langmuir model; moreover, the fluorescence of Ag+@UiO-66-(COOH)2 gradually decreases with the deposition of AgI, which can be quantitatively depicted by a linear equation. The limit of detection toward I- is calculated to be 0.58 ppm.

Lowly-aggregated perylene diimide as a near-infrared electrochemiluminescence luminophore for ultrasensitive immunosensors at low potentials.

In the electrochemiluminescence (ECL) field, most reported luminophores were focused on high-triggering potential and short wavelength, which was adverse for the ECL theory study and application at low potentials. Perylene diimide derivatives could emit near-infrared (NIR) ECL at low-triggering potential; however, they are always highly aggregated into a microrod structure and stacked together, which largely limited their application in biological fields such as bio-sensing and bio-imaging. To overcome these obstacles, we designed a novel perylene diimide molecule, namely N,N'-dicaproate sodium-3,4,9,10-perylenedicarboximide (PDI-COONa). This molecule self-assembled into a two-dimensional network nanostructure, which largely decreased the aggregation degree of PDI molecules and provided solid bases for designing lowly-aggregated PDI molecules. Also, the formed nanoluminophore produced strong emission at -0.26 V with an NIR wavelength 700 nm, which should be due to the excited J-type PDI-COO- dimers. Moreover, this network nanoluminophore well-dispersed on graphene oxide (GO) as an ECL nanomaterial to label secondary antibodies and fabricate a sandwiched immunosensor for alpha-fetoprotein (AFP) detection between 0 and -0.6 V. This immunosensor showed a wider linear response for AFP ranging from 0.1 fg mL-1 to 1 µg mL-1 with a low detection limit 0.0353 fg mL-1 compared with other immunosensors based on PDI microrod-modified GO ECL materials. The fabricated immunosensor also showed good feasibility in human serum samples.

A novel ratiometric electrochemical biosensing strategy based on T7 exonuclease-assisted homogenous target recycling coupling hairpin assembly-triggered double-signal output for the multiple amplified detection of miRNA.

A novel ratiometric electrochemical biosensing strategy based on T7 exonuclease (T7 Exo)-assisted homogenous target recycling coupling hairpin assembly triggered dual-signal output was proposed for the accurate and sensitive detection of microRNA-141 (miRNA-141). Concretely, in the presence of target miRNA, abundant signal transduction probes were released via the T7 Exo-assisted homogenous target recycling amplification, which could be captured by the specially designed ferrocene-labeled hairpin probe (Fc-H1) on -electrode interface and triggered the nonenzymatic catalytic hairpin assembly (Fc-H1 + MB-H2) to realize the cascade signal amplification and dual-signal output. Through such a conformational change process, the electrochemical signal of Fc (IFc) and MB (IMB) is proportionally and substantially decreased and increased. Therefore, the signal ratio of IMB/IFc can be employed to accurately reflect the true level of original miRNA. Benefiting from the efficient integration of the T7 Exo-assisted target recycle, nonenzymatic hairpin assembly and dual-signal output mode, the proposed sensor could realize the amplified detection of miRNA-141 effectively with a wide detection range from 1 fM to 100 pM, and a detection limit of 200 aM. Furthermore, it exhibits outstanding sequence specificity to discriminate mismatched RNA, acceptable reproducibility and feasibility for real sample. This strategy effectively integrated the advantages of multiple amplification and ratiometric output modes, which could provide an accurate and efficient method in biosensing and clinical diagnosis.

Two-dimensional BCN nanosheets self-assembled with hematite nanocrystals for sensitively detecting trace toxic Pb(II) ions in natural water.

In the present work, hematite-boron-carbonitride (Fe2O3-BCN) nanosheets were synthesized by a simple hydrothermal reaction and the following high temperature treatment. The morphology, structure and chemical composition of the as-prepared material were carefully characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The Fe2O3-BCN nanosheets were used to modified on the surface of the glassy carbon electrode to fabricate an electrochemical sensor for lead ions (Pb(II)) via differential pulse anodic stripping voltammetry (DPASV). At the same time, the influence of the modification concentration, solution acidity, deposition potential and deposition time on response peak current of Pb(II) at the Fe2O3-BCN-based electrochemical sensor was well investigated. Under the optimized conditions, the electrochemical signal and concentration of Pb(II) show two-stage linear relationship in the range of 0.5 - 40 µg/L and 40 -140 µg/L, with a limit of detection (LOD) of 0.129 µg/L. The Fe2O3-BCN-based electrochemical sensor shows excellent selectivity and anti-interference ability in the anti-interference experiments and actual sample analysis experiments, revealing its broad application in environmental monitoring of Pb(II).

Graphene-PtPd nanocomposite for low-potential-driven electrochemiluminescent determination of carcinoembryonic antigen using Ru(bpy)32.

As well known, the electrochemiluminescence (ECL) of tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)32+) heavily relies on highly positive or negative triggered voltage, prejudicing the detection toward the bio-molecules. In this work, Ru(bpy)32+ could generate enhanced and stable ECL at a low potential of 0.05 V (vs. Ag/AgCl) on graphene-PtPd hybrid, attributing to its excellent electrocatalysis from the synergistic effect between Pt and Pd. The obtained low-potential-driven ECL could be quenched by MoS2 nanoflowers. Based on the quenching effect, a sandwich "signal-off" ECL immunosensor was fabricated to sensitively detect carcinoembryonic antigen (CEA). A linear calibration curve from 1 fg mL-1 to 1 ng mL-1 was obtained along with a low detection limit of 0.54 fg mL-1 (S/N = 3) under optimal conditions. The sensor showed satisfactory specificity, stability, and reproducibility and was successfully applied to determine CEA in actual samples. The recoveries ranged from 98.80 to 100.23%, and the relative standard deviation (RSD) was lower than 5%. Above all, this work explored new materials in low-potential-driven ECL system and provided a reliable sensing strategy for clinical applications.

Nasal and Oral Subunits Reconstruction of Localized Scleroderma Deformities.

ABSTRACT: Localized scleroderma is a rare soft tissue disorder characterized by a thickening of the skin from excessive collagen deposits. For patients with face involved, soft tissue depression and atrophy could cause serious facial contour deformity and adversely affect the patients' quality of social life. However, localized scleroderma cases with delicate facial aesthetic subunits defects were rarely reported to be surgically reconstructed. In this study, we present 2 patients with nasal subunits and oral subunit deformities caused by localized scleroderma respectively. The first patient with a right-side alar defect and nasal dorsum depression, forehead depression and eyebrow depression were treated through a 2-stage surgical approach, with microvascular preauricular and helical rim flap and dermofat graft transplantation. The lower lip and mandible defects of the second patient were reconstructed with a combination of submental flap and fat grafting. The transplanted dermofat graft, fat graft, the microvascular free flap, and the submental flap survived completely and maintained adequate tissue volume and facial contour during the follow-up time of 2 years. Both patients were satisfied with the overall aesthetic results. This clinical report supports the use of microsurgical flap and tissue grafts on the treatment of localized scleroderma (LS) caused facial aesthetic subunits deformities.

Enzyme-free and triple-amplified electrochemical sensing of 8-hydroxy-2'-deoxyguanosine by three kinds of short pDNA-driven catalyzed hairpin assemblies followed by a hybridization chain reaction.

A sensitive and enzyme-free electrochemical aptasensor was constructed for the sensing of 8-hydroxy-2'-deoxyguanosine (8-OH-dG). In the process of constructing the aptasensor, triple signal amplification strategies were introduced to enhance the sensitivity. First, every aptamer/pDNA complex immobilized on magnetic beads could release three kinds of pDNAs when 8-OH-dG was introduced, which caused three-fold magnification of the target. Second, the released three kinds of pDNAs initiated catalyzed hairpin assembly between two hairpin DNAs (HP1 and HP2) on a gold electrode. Meanwhile, the three kinds of pDNAs were released again by a strand displacement reaction to obtain the next catalyzed hairpin assembly. Third, the emerging toehold of HP2 further induced a hybridization chain reaction (HCR) between two hairpin DNAs (HP3 and HP4), forming a long double-stranded DNA concatemer on the surface of the electrode. Finally, [Ru(NH3)6]3+, an electroactive cation, was adsorbed onto the long dsDNA concatemer by electrostatic interactions and consequently, an electrochemical signal was generated. Under this triple signal amplification, a low detection limit down to 24.34 fM has been obtained for 8-OH-dG determination, which is superior to those of most previously reported methods.

Sensitive determination of formamidopyrimidine DNA glucosylase based on phosphate group-modulated multi-enzyme catalysis and fluorescent copper nanoclusters.

In this work, a method for quantifying the activity of formamidopyrimidine DNA glucosylase (Fpg) was designed based on phosphate group (P)-modulated multi-enzyme catalysis and fluorescent copper nanoclusters (CuNCs). By eliminating 8-oxoguanine from double-stranded DNA, Fpg generates a nick with P at both 3' and 5' termini. Subsequently, part of the DNA is digested by 5'P-activated lambda exonuclease (λ Exo), and the generated 3'P disables exonuclease I (Exo I), resulting in the generation of single-stranded DNA containing poly(thymine) (poly(T)). Using poly(T) as templates, CuNCs were prepared to emit intense fluorescence as the readout of this method. However, in the absence of Fpg, the originally modified 5'P triggers the digestion of λ Exo. In this case, fluorescence emission is not obtained because CuNCs cannot be formed without DNA templates. Therefore, the catalysis of λ Exo and Exo I can be tuned by 5'P and 3'P, which can be further used to determine the activity of Fpg. The fluorescent Fpg biosensor works in a "signal-on" manner with the feature of "zero" background noise, and thus shows desirable analytical features and good performance. Besides, Fpg in serum samples and cell lysate could be accurately detected with the biosensor, indicating the great value of the proposed system in practical and clinical analysis.

Facile Synthesis of Hierarchical Nanosized Single-Crystal Aluminophosphate Molecular Sieves from Highly Homogeneous and Concentrated Precursors.

The synthesis of hierarchical nanosized zeolite materials without growth modifiers and mesoporogens remains a substantial challenge. Herein, we report a general synthetic approach to produce hierarchical nanosized single-crystal aluminophosphate molecular sieves by preparing highly homogeneous and concentrated precursors and heating at elevated temperatures. Accordingly, aluminophosphate zeotypes of LTA (8-rings), AEL (10-rings), AFI (12-rings), and -CLO (20-rings) topologies, ranging from small to extra-large pores, were synthesized. These materials show exceptional properties, including small crystallites (30-150 nm), good monodispersity, abundant mesopores, and excellent thermal stability. A time-dependent study revealed a non-classical crystallization pathway by particle attachment. This work opens a new avenue for the development of hierarchical nanosized zeolite materials and understanding their crystallization mechanism.

A dandelion-like liposomes-encoded magnetic bead probe-based toehold-mediated DNA circuit for the amplification detection of MiRNA.

The development of facile and sensitive miRNA quantitative detection methods is a central challenge for the early diagnosis of miRNA-related diseases. Herein, we propose a strategy for a liposome-encoded magnetic bead-based DNA toehold-mediated DNA circuit for the simple and sensitive detection of miRNA based on a toehold-mediated circular strand displacement reaction (TCSDR) coupled with a personal glucometer (PGM ). In this strategy, a glucoamylase-encapsulated liposomes (GELs)-encoded magnetic bead (GELs-MB) probe is designed to integrate target binding, magnetic separation, and signal response. Upon sensing the target miRNA-21, a GELs-MB probe-based toehold-mediated circular strand displacement reaction (TCSDR) was initiated with the help of fuel-DNA, constructing a DNA circuit system, and realizing target recycling amplification and the disassembly of the liposomes. The disassembled liposomes were finally removed via magnetic separation, and the encapsulated glucoamylase was liberated to catalyze amylose hydrolysis with multiple turnovers to glucose for a PGM readout. Benefiting from target recycling amplification initiated by the toehold-mediated DNA circuit and the liposome multiple-label amplification, a small quantity of target miRNA-21 can be transformed into a large glucose signal. The strategy realized the quantification of miRNA-21 down to a level of 0.7 fM without enzymatic amplification or precise instrumentation. Moreover, the high-density GELs-MB probe allows the sensitive detection of miRNA-21 to be accomplished within 1.5 h. Furthermore, this strategy exhibits the advantages of specificity and simplicity, since a toehold-mediated strand displacement reaction, magnetic separation and portable PGM were used. Importantly, this strategy has been demonstrated to allow the high-confidence quantification of miRNA. Therefore, with the advantages of low cost, ease of use, portability, and sensitivity, the reported method holds great potential for the early diagnosis of miRNA-related diseases.

Near-Infrared Light Excited and Localized Surface Plasmon Resonance-Enhanced Photoelectrochemical Biosensing Platform for Cell Analysis.

Under near-infrared (NIR) light of 810 nm wavelength for irradiation, a very simple and highly sensitive photoelectrochemical (PEC) biosensing platform has been established using the localized surface plasmon resonance effect of Au nanoparticles (NPs) as signal amplification for the nondestructive analysis of living cells. The water-dispersible Ag2S quantum dots (QDs) synthesized by a one pot method were employed as photoelectrochemically active species, and they exhibited excellent PEC properties irradiated with NIR light which was chosen due to the obvious absorption and fluorescent emission in the NIR light region. After the incorporation of Au NPs on the Ag2S QDs modified ITO electrode, the photoelectric conversion efficiency was greatly increased, at ∼2.5 times that of the pure Ag2S QDs modified electrode. Additionally, 4-mercaptophenylboronic acid (MPBA) molecules, as recognition elements, self-assembled on the electrode surface through Au-S bonds. On the basis of the chemical reaction between sialic acid on the cytomembranes and boric acid of MPBA, the very simple PEC biosensing platform was used for the quantitative determination of MCF-7 cells and dynamic evaluation of cell surface glycan expression under the external stimulus of sialidase. Under NIR light of 810 nm and a potential of 0.15 V, this proposed strategy exhibited a wide linear range from 1 × 102 to 1 × 107 cells/mL, with an experimental detection limit of 100 cells/mL. Importantly, this work provided a promising application for NIR Ag2S QDs coupled with Au NPs in the development of a novel PEC biosensing platform for the nondestructive analysis of biological samples.