Construction of self-powered cytosensing device based on ZnO nanodisks@g-C3N4 quantum dots and application in the detection of CCRF-CEM cells

SILAR Growth of ZnO NSs/CdS QDs on the Optical Fiber-Based Opto-Electrode with Guided In Situ Light and Its Application for the "Signal-On" Detection of Inflammatory Cytokine

In this study, a novel integrated photoelectrochemical (PEC) sensor platform was proposed, utilizing an optical fiber (OF) as the working electrode for guided in situ light. A CdS quantum dots (QDs)/ZnO nanosheets (NSs) n-n heterojunction was quickly and easily constructed on the OF surface by successive ionic layer adsorption and reaction (SILAR). Au nanoparticles (NPs)@dsDNA as a capturing probe were modified on the CdS QDs/ZnO NSs@OF (CZ@OF). Due to the energy transfer between Au NPs@dsDNA and CdS QDs, the resultant opto-electrode has a lower background near zero, enabling the "signal-on" detection of biomarkers (interleukin-6 (IL-6) as a model). The OF-PEC biosensor demonstrated a wide linear range from 1 to 100 pg mL-1 with a regression coefficient (R2) of 0.9958 and an impressive detection limit (LOD) of 0.19 pg mL-1. More significantly, the proposed OF-PEC can be successfully used for the detection of IL-6 in serum samples from patients with pulmonary arterial hypertension, and it showed consistency and is more sensitive to trace concentrations compared to BD FACSCanto II flow cytometry used at the hospital. This holds significance for an early disease diagnosis. Therefore, the proposed OF-PEC not only achieves integration of the light source and sensing interface but also enables sensitive and accurate "signal-on" detection of IL-6. Furthermore, due to the flexibility and remote detection capabilities of OF, the application of OF-PEC is expected to be expanded more widely. This approach opens up possibilities for advances in PEC sensing.

Advancements in Bio-inspired Self-Powered Wireless Sensors: Materials, Mechanisms, and Biomedical Applications

The rapid maturation of smart city ecosystems is intimately linked to advances in the Internet of Things (IoT) and self-powered sensing technologies. Central to this evolution are battery-less sensors that are critical for applications such as continuous health monitoring through blood metabolites and vital signs, the recognition of human activity for behavioral analysis, and the operational enhancement of humanoid robots. The focus on biosensors that exploit the human body for energy-spanning wearable, attachable, and implantable variants has intensified, driven by their broad applicability in areas from underwater exploration to biomedical assays and earthquake monitoring. The heart of these sensors lies in their diverse energy harvesting mechanisms, including biofuel cells, and piezoelectric, triboelectric, and pyroelectric nanogenerators. Notwithstanding the wealth of research, the literature still lacks a holistic review that integrates the design challenges and implementation intricacies of such sensors. Our review seeks to fill this gap by thoroughly evaluating energy harvesting strategies from both material and structural perspectives and assessing their roles in powering an array of sensors for myriad uses. This exploration offers a comprehensive outlook on the state of self-powered sensing devices, tackling the nuances of their deployment and highlighting their potential to revolutionize data gathering in autonomous systems. The intent of this review is to chart the current landscape and future prospects, providing a pivotal reference point for ongoing research and innovation in self-powered wireless sensing technologies.

Graphitic Carbon Nitride Quantum Dots (g-C3 N4 QDs): From Chemistry to Applications

Since their emergence in 2014, graphitic carbon nitride quantum dots (g-C3 N4 QDs) have attracted much interest from the scientific community due to their distinctive physicochemical features, including structural, morphological, electrochemical, and optoelectronic properties. Owing to their desirable characteristics, such as non-zero band gap, ability to be chemically functionalized or doped, possessing tunable properties, outstanding dispersibility in different media, and biocompatibility, g-C3 N4 QDs have shown promise for photocatalysis, energy devices, sensing, bioimaging, solar cells, optoelectronics, among other applications. As these fields are rapidly evolving, it is very strenuous to pinpoint the emerging challenges of the g-C3 N4 QDs development and application during the last decade, mainly due to the lack of critical reviews of the innovations in the g-C3 N4 QDs synthesis pathways and domains of application. Herein, an extensive survey is conducted on the g-C3 N4 QDs synthesis, characterization, and applications. Scenarios for the future development of g-C3 N4 QDs and their potential applications are highlighted and discussed in detail. The provided critical section suggests a myriad of opportunities for g-C3 N4 QDs, especially for their synthesis and functionalization, where a combination of eco-friendly/single step synthesis and chemical modification may be used to prepare g-C3 N4 QDs with, for example, enhanced photoluminescence and production yields.

MOFs-derived Co3O4@MnO2@Carbon dots with enhanced nanozymes activity for photoelectrochemical detection of cancer cells in whole blood

Nanozymes have attracted widespread attention, and rationally designing high-activity nanozymes to improve their application performance are a long-term objective. Herein, taking metal-organic frameworks-derived Co3O4 polyhedron with large surface area and high porosity as nanoconfinement carriers, Co3O4@MnO2@CDs polyhedron was successfully synthesized by the room-temperature reduction of MnO4- ions and physical load of carbon dots (CDs). Through cancer cells-triggered double antibody sandwich strategy, the Co3O4@MnO2@CDs polyhedron were introduced to the TiO2 nanoparticle (NPs) modified electrode, leading to the decreased photocurrent. The Co3O4@MnO2@CDs polyhedron can not only quench the photocurrent of TiO2 NPs, also act as nanozymes to catalyze precipitates. Moreover, the precipitates can not only reduce the photoelectrochemical (PEC) response, also increase the quenching capacity of the Co3O4@MnO2@CDs polyhedron. Additionally, the steric hindrance effect of the Co3O4@MnO2@CDs-Ab conjugates further weaken the photocurrent. Based on the multifunctional Co3O4@MnO2@CDs polyhedron, the proposed PEC biosensor for the detection of A549 cancer cells exhibits a wide linear range from 102 to 106 cells/mL and a low detection limit of 11 cells/mL. Furthermore, this strategy can differentiate between lung cancer patients and healthy individuals. The designed multifunctional Co3O4@MnO2@CDs nanozymes provide a new horizon for PEC detection of cancer cells, and may have great potential in early clinical diagnosis and biomedical research.

DNA-Functionalized Porphyrinic Metal-Organic Framework-Based Drug Delivery System for Targeted Bimodal Cancer Therapy

A DNA-functionalized porphyrinic MOF (porMOF) drug delivery system was successfully constructed. porMOF as a photosensitizer and drug delivery carrier can integrate photodynamic therapy (PDT) and chemotherapy. Via the strong coordination interaction between the zirconium cluster of porMOF and the terminal phosphate group of DNA, the stable modification of the DNA layer on the porMOF surface is achieved. Meanwhile, the introduction of C/G-rich base pairs into the DNA double-stranded structure provides more binding sites of chemotherapeutic drug doxorubicin (DOX). AS1411, an aptamer of nucleolin proteins that are overexpressed by cancer cells, is introduced in the double-stranded terminal, which can endow the nanosystem with the ability to selectively recognize cancer cells. C-rich sequences in DNA double strands form an i-motif structure under acidic conditions to promote the highly efficient release of DOX in cancer cells. In vitro and in vivo experiments demonstrate that the synergistic PDT/chemotherapy modality achieves highly efficient cancer cell killing and tumor ablation without undesirable side effects.

Nanotechnology-based diagnostics and therapeutics in acute lymphoblastic leukemia: a systematic review of preclinical studies

Background: Leukemia is a malignant disease that threatens human health and life. Nano-delivery systems improve drug solubility, bioavailability, and blood circulation time, and release drugs selectively at desired sites using targeting or sensing strategies. As drug carriers, they could improve therapeutic outcomes while reducing systemic toxicity. They have also shown promise in improving leukemia detection and diagnosis. The study aimed to assess the potential of nanotechnology-based diagnostics and therapeutics in preclinical human acute lymphoblastic leukemia (h-ALL). Methods: We performed a systematic search through April 2022. Articles written in English reporting the toxicity, efficacy, and safety of nanotechnology-based drugs (in the aspect of treatment) and specificity, limit of detection (LOD), or sensitivity (in the aspect of the detection field) in preclinical h-ALL were included. The study was performed according to PRISMA instructions. The methodological quality was assessed using the QualSyst tool. Results: A total of 63 original articles evaluating nanotechnology-based therapeutics and 35 original studies evaluating nanotechnology-based diagnostics were included in this review. As therapeutics in ALL, nanomaterials offer controlled release, targeting or sensing ligands, targeted gene therapy, photodynamic therapy and photothermic therapy, and reversal of multidrug-resistant ALL. A narrative synthesis of studies revealed that nanoparticles improve the ratio of efficacy to the toxicity of anti-leukemic drugs. They have also been developed as a vehicle for biomolecules (such as antibodies) that can help detect and monitor leukemic biomarkers. Therefore, nanomaterials can help with early diagnostics and personalized treatment of ALL. Conclusion: This review discussed nanotechnology-based preclinical strategies to achieve ALL diagnosis and therapy advancement. This involves modern drug delivery apparatuses and detection devices for prompt and targeted disease diagnostics. Nonetheless, we are yet in the experimental phase and investigational stage in the field of nanomedicine, with many features remained to be discovered as well as numerous problems to be solved.

A novel photoelectrochemical immunosensor based on TiO2@Bi2WO6 hollow microspheres and Ag2S for sensitive detection of SARS-COV-2 nucleocapsid protein

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-COV-2) is a cluster of β coronaviruses. The 2019 coronavirus disease (COVID-19) caused by SARS-COV-2 is emerging as a global pandemic. Thus, early diagnosis of SARS-COV-2 is essential to prevent severe outbreaks of the disease. In this experiment, a novel label-free photoelectrochemical (PEC) immunosensor was obtained based on silver sulfide (Ag₂S) sensitized titanium dioxide@bismuth tungstate (TiO₂@Bi₂WO₆) nanocomposite for quantitative detection of SARS-COV-2 nucleocapsid protein. The constructed TiO₂@Bi₂WO₆ hollow microspheres had large specific surface area and could produce high photocurrent intensity under visible light illumination. Ag₂S was in-situ grown on the surface of thioglycolic acid (TGA) modified TiO₂@Bi₂WO₆. In particular, TiO₂@Bi₂WO₆ and Ag₂S formed a good energy level match, which could effectively enhance the photocurrent conversion efficiency and strength the photocurrent response. Ascorbic acid (AA) acted as an effective electron donor to effectively eliminate photogenerated holes. Under optimal experimental conditions, the constructed immunosensor presented a supersensitive response to SARS-COV-2 nucleocapsid protein, with a desirable linear relationship ranged from 0.001 to 50 ng/mL for nucleocapsid protein and a lower detection limit of 0.38 pg/mL. The fabricated sensor exhibited a wide linear range, excellent selectivity, specificity and stability, which provided a valuable referential idea for the detection of SARS-COV-2.

Two-Dimensional Graphitic Carbon Nitride (g-C3N4) Nanosheets and Their Derivatives for Diagnosis and Detection Applications

The early diagnosis of certain fatal diseases is vital for preventing severe consequences and contributes to a more effective treatment. Despite numerous conventional methods to realize this goal, employing nanobiosensors is a novel approach that provides a fast and precise detection. Recently, nanomaterials have been widely applied as biosensors with distinctive features. Graphite phase carbon nitride (g-C₃N₄) is a two-dimensional (2D) carbon-based nanostructure that has received attention in biosensing. Biocompatibility, biodegradability, semiconductivity, high photoluminescence yield, low-cost synthesis, easy production process, antimicrobial activity, and high stability are prominent properties that have rendered g-C₃N₄ a promising candidate to be used in electrochemical, optical, and other kinds of biosensors. This review presents the g-C₃N₄ unique features, synthesis methods, and g-C₃N₄-based nanomaterials. In addition, recent relevant studies on using g-C₃N₄ in biosensors in regard to improving treatment pathways are reviewed.

Nanotechnology: A Promising Approach for Cancer Diagnosis, Therapeutics and Theragnosis

Cancer remains the most devastating disease and the major cause of mortality worldwide. Although early diagnosis and treatment are the key approach in fighting against cancer, the available conventional diagnostic and therapeutic methods are not efficient. Besides, ineffective cancer cell selectivity and toxicity of traditional chemotherapy remain the most significant challenge. These limitations entail the need for the development of both safe and effective cancer diagnosis and treatment options. Due to its robust application, nanotechnology could be a promising method for in-vivo imaging and detection of cancer cells and cancer biomarkers. Nanotechnology could provide a quick, safe, cost-effective, and efficient method for cancer management. It also provides simultaneous diagnosis and treatment of cancer using nano-theragnostic particles that facilitate early detection and selective destruction of cancer cells. Updated and recent discussions are important for selecting the best cancer diagnosis, treatment, and management options, and new insights on designing effective protocols are utmost important. This review discusses the application of nanotechnology in cancer diagnosis, therapeutics, and theragnosis and provides future perspectives in the field.

Design of Smart Nanomedicines for Effective Cancer Treatment

Nanomedicine is a novel field of study that involves the use of nanomaterials to address challenges and issues that are associated with conventional therapeutics for cancer treatment including, but not limited to, low bioavailability, low water-solubility, narrow therapeutic window, nonspecific distribution, and multiple side effects of the drugs. Multiple strategies have been exploited to reduce the nonspecific distribution, and thus the side effect of the active pharmaceutical ingredients (API), including active and passive targeting strategies and externally controllable release of the therapeutic cargo. Site-specific release of the drug prevents it from impacting healthy cells, thereby significantly reducing side effects. API release triggers can be either externally applied, as in ultrasound-mediated activation, or induced by the tumor. To rationally design such nanomedicines, a thorough understanding of the differences between the tumor microenvironment versus that of healthy tissues must be pared with extensive knowledge of stimuli-responsive biomaterials. Herein, we describe the characteristics that differentiate tumor tissues from normal tissues. Then, we introduce smart materials that are commonly used for the development of smart nanomedicines to be triggered by stimuli such as changes in pH, temperature, and enzymatic activity. The most recent advances and their impact on the field of cancer therapy are further discussed.

A Comprehensive Review of Graphitic Carbon Nitride (g-C3N4)-Metal Oxide-Based Nanocomposites: Potential for Photocatalysis and Sensing

g-C3N4 has drawn lots of attention due to its photocatalytic activity, low-cost and facile synthesis, and interesting layered structure. However, to improve some of the properties of g-C3N4, such as photochemical stability, electrical band structure, and to decrease charge recombination rate, and towards effective light-harvesting, g-C3N4-metal oxide-based heterojunctions have been introduced. In this review, we initially discussed the preparation, modification, and physical properties of the g-C3N4 and then, we discussed the combination of g-C3N4 with various metal oxides such as TiO2, ZnO, FeO, Fe2O3, Fe3O4, WO3, SnO, SnO2, etc. We summarized some of their characteristic properties of these heterojunctions, their optical features, photocatalytic performance, and electrical band edge positions. This review covers recent advances, including applications in water splitting, CO2 reduction, and photodegradation of organic pollutants, sensors, bacterial disinfection, and supercapacitors. We show that metal oxides can improve the efficiency of the bare g-C3N4 to make the composites suitable for a wide range of applications. Finally, this review provides some perspectives, limitations, and challenges in investigation of g-C3N4-metal-oxide-based heterojunctions.

Recent Advances of Nanostructured Materials for Photoelectrochemical Bioanalysis

Nowadays, the emerging photoelectrochemical (PEC) bioanalysis has drawn intensive interest due to its numerous merits. As one of its core elements, functional nanostructured materials play a crucial role during the construction of PEC biosensors, which can not only be employed as transducers but also act as signal probes. Although both chemical composition and morphology control of nanostructured materials contribute to the excellent analytical performance of PEC bioassay, surveys addressing nanostructures with different dimensionality have rarely been reported. In this review, according to classification based on dimensionality, zero-dimensional, one-dimensional, two-dimensional, and three-dimensional nanostructures used in PEC bioanalysis are evaluated, with an emphasis on the effect of morphology on the detection performances. Furthermore, using the illustration of recent works, related novel PEC biosensing patterns with promising applications are also discussed. Finally, the current challenges and some future perspectives in this field are addressed based on our opinions.

Multifunctional Gold Nano-Cytosensor With Quick Capture, Electrochemical Detection, and Non-Invasive Release of Circulating Tumor Cells for Early Cancer Treatment

Circulating tumor cells (CTCs) are metastatic tumor cells that shed into the blood from solid primary tumors, and their existence significantly increases the risk of metastasis and recurrence. The timely discovery and detection of CTCs are of considerable importance for the early diagnosis and treatment of metastasis. However, the low number of CTCs hinders their detection. In the present study, an ultrasensitive electrochemical cytosensor for specific capture, quantitative detection, and noninvasive release of EpCAM-positive tumor cells was developed. The biosensor was manufactured using gold nanoparticles (AuNPs) to modify the electrode. Three types of AuNPs with controllable sizes and conjugated with a targeting molecule of monoclonal anti-EpCAM antibody were used in this study. Electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) of the cytosensors were performed to evaluate the cell capture efficiency and performance. The captured 4T1 cells by the AuNPs hindered electron transport efficiency, resulting in increased EIS responses. The cell capture response recorded using EIS or DPV indicated that the optimal AuNPs size should be 17 nm. The cell capture response changed linearly with the concentration range from 8.0 × 10 to 1 × 10⁷ cells/mL, and the limit of detection was 50 cells/mL. After these measurements, glycine-HCl (Gly-HCl) was used as an antibody eluent to destroy the binding between antigen and antibody to release the captured tumor cells without compromising their viability for further clinical research. This protocol realizes rapid detection of CTCs with good stability, acceptable assay precision, significant fabrication reproducibility with a relative standard deviation of 2.09%, and good recovery of cells. Our results indicate that the proposed biosensor is promising for the early monitoring of CTCs and may help customize personalized treatment options.

On-site electrochemical determination of phosphate with high sensitivity and anti-interference ability in turbid coastal waters

Phosphate is considered to be an important biogenic element and responsible for eutrophication in aquatic ecosystems, existing in both dissolved and absorbed forms. Due to the complex matrix of coastal seawater, a high sensitivity and anti-interference method for phosphate detection is required for environmental protection. In this study, a novel electrochemical method was proposed based on reduced graphene oxide-ordered mesoporous carbon screen-printed electrode (rGO-OMC/SPE) analysis, allowing sensitivity and reliable determination of phosphate in turbid coastal waters. Combining the good absorption capacity of OMC with the excellent electroconductivity of rGO, the fabricated electrode exhibits improved signal responses, enhanced by up to 43-fold. The platform was evaluated using turbidity interference test with good recovery percentages comprised between 96% and 105% in different phosphate concentration, and salinity interference test between 92% and 105%, respectively. A linear range from 0.2 to 150 μM phosphate was achieved, with a detection limit of 0.05 μM (s/n = 3). The fabricated platform was successfully used for on-site analysis of phosphate in turbid coastal waters. This reliable and effective method for the analysis of phosphate in turbid coastal waters allows for sensitivity and anti-interference determination, while also representing a significant step towards comprehensive and convenient analysis of phosphorus species.

A 'smart' aptamer-functionalized continuous label-free cell catch-transport-release system

Label-free cell sorting devices are of great significance for biomedical research and clinical therapeutics. However, current platforms for label-free cell sorting cannot achieve continuity and selectivity simultaneously, resulting in complex steps and limited reliability. Here, an immunoaffinity-based cell catch-transport-release thermo-chemo-mechanical coupling hydrogel (iCatch) device is reported. It contains a temperature-responsive hydrogel that can generate spatial movement synergically with the reversible binding of affinity handle modified. The functionalized hydrogel is embedded inside a biphasic microfluidic platform to enable cell transportation between the flows. The cell sorting capability and biocompatibility of the iCatch device were validated with CCRF-CEM cells as a proof-of-concept, and CCRF-CEM-specific aptamers with thermo-responsive affinity as well as a hydrogel with temperature-dependent volume were employed accordingly. A cell catching efficiency of ∼40% and a recovery rate of ∼70% were achieved. The iCatch device provides a high-throughput (∼900 cells mm-1 s-1) platform for cell sorting and is ultimately valuable for downstream biomedical applications.

Enzymatic photoelectrochemical bioassay based on hierarchical CdS/NiO heterojunction for glucose determination

The design and development of a 3D hierarchical CdS/NiO heterojunction and its application in a self-powered cathodic photoelectrochemical (PEC) bioanalysis is introduced. Specifically, NiO nanoflakes (NFs) were in situ formed on carbon fibers via a facile liquid-phase deposition method followed by an annealing step and subsequent integration with CdS quantum dots (QDs). The glucose oxidase (GOx) was then coated on the photocathode to allow the determination of glucose. Under 5 W 410 nm LED light and at a working voltage of 0.0 V (vs. Ag/AgCl), this method can assay glucose concentrations down to 1.77×10^-9 M. The linear range was 5×10^-7 M to 1×10^-3 M, and the relative standard deviation (RSD) was below 5%. The photocathodic biosensor achieved target detection with high sensitivity and selectivity. This work is expected to stimulate more passion in the development of innovative hierarchical heterostructures for advanced self-powered photocathodic bioanalysis. Design of 3D hierarchical CdS/NiO heterojunction and its application in a self-powered cathodic photoelectrochemical (PEC) bioanalysis.

Visible light mediated self-powered sensing based on target induced recombination of photogenerated carriers

Self-powered sensing platforms have received widespread attention in areas such as portable, wearable and point-of-care devices. Here we reported visible light mediated self-powered electrochemical sensing based on target induced recombination of photogenerated carriers, which has highly sensitive to detect copper ions concentration. We utilized the recombination of photogenerated carriers mechanism to design visible light-responsive Fe₂O₃-CdS n-n heterojunction as photoanode material, which greatly improved the problem of output energy in photocatalytic self-powered sensors. Expectedly, our proposed visible light mediated self-powered electrochemical system has high separation efficiency of photogenerated carriers, which is 8.4 times that in presence of Cu²⁺. Furthermore, this self-powered electrochemical sensing platform used Cu²⁺ induced recombination of photogenerated carriers, showed a clear linear relationship from 1 nM to 5000 nM with an acceptable detection limit of 0.4 nM. This self-powered electrochemical sensing platform with excellent selectivity, accredited reproducibility and believable stability exhibited promising prospects in developing portable sensing devices and detection chip for real-time and rapid monitoring of Cu²⁺.

Polymeric Carbon Nitride-Derived Photocatalysts for Water Splitting and Nitrogen Fixation

Photocatalysis is a promising energy conversion and environmental restoration technology. The main focus of photocatalysis is the development and manufacture of highly efficient photocatalysts. Semiconductor-based photocatalysis technology based on harnessing solar energy is considered as an attractive approach to solve the problems of global energy shortage and environmental pollution. Since 2009 pioneering work has been carried out on polymeric carbon nitride (PCN) for visible photocatalytic water splitting, thus PCN-based photocatalysis has become a hot research topic, demanding significant research attention. This article reviews the physical and chemical properties, synthesis methods, and the methods to control the morphology, heteroatom doping, and construction of heterojunctions to improve the performance of PCN-based photocatalysts in water splitting and nitrogen fixation. Through different design strategies, the photo-generated electron-hole pair separation efficiency of PCN materials can be effectively improved, thereby improving their photocatalytic performance. Finally, the challenges of PCN-based photocatalysts in water splitting and nitrogen fixation applications are discussed herein. It is strongly believed that through different design strategies, efficient PCN-based photocatalysts can be constructed for both water splitting and nitrogen reduction. These excellent modification strategies can be used as a guiding theory for photocatalytic reactions of other promising catalysts and further promote the development of photocatalysis.

Photo-driven self-powered biosensors for ultrasensitive microRNA detection based on metal-organic framework-controlled release behavior

We developed a "signal-on" self-powered biosensing strategy by taking full advantage of both photoelectrochemical biofuel cells (PBFCs) and metal-organic framework (MOF)-controlled release behavior for ultrasensitive microRNA assay. PBFC-based self-powered sensors have the unique characteristics of non-requirement of external power sources, simple fabrication process, miniature size, good anti-interference ability and low cost. Furthermore, based on the target microRNA-induced release of the electron donor ascorbic acid and the high catalytic ability of the biocathode to catalyse the oxygen reduction reaction, photo-driven self-powered biosensors for ultrasensitive microRNA detection were successfully realized. The as-proposed signal-on biosensor not only provides a simple and effective strategy, but also possesses the merits of a wide dynamic concentration response range and high sensitivity for microRNA detection, with a limit of detection down to 0.16 fM.

Molecularly imprinted photoelectrochemical sensing based on ZnO/polypyrrole nanocomposites for acrylamide detection

A highly sensitive quenching molecular imprinting (MIP) photoelectrochemical (PEC) sensor was proposed to detect acrylamide (AM) by using the photoactive composite of ZnO and polypyrrole (PPy) as the PEC signal probe. ZnO, with high electron mobility, excellent chemical and thermal stability as well as good biocompatibility, was selected as the photoelectrically active material. A polypyrrole film was formed on the nanodisk ZnO by electrochemical polymerization, and the recognition site of AM was left on the surface of the PPy film by elution, enabling the specific detection of AM. The transfer of electrons will be hindered when AM is adsorbed on the ZnO/PPy nanocomposites surface, which results in the decrease of photocurrent signal. The proposed molecularly imprinted PEC sensor exhibits significant detection performance of AM in the range of 10-1 M-2.5 × 10-9 M with a LOD of 2.147 × 10-9 M (S/N = 3). The use of photoelectrochemical technology combined with molecular imprinting technology enables the PEC sensor to have excellent selectivity, superior repeatability, preferable stability, low cost, and easy construction, providing a new method for the detection of AM. The high recovery rate in the detection of real samples of potato chips and biscuits indicates that the proposed PEC sensor has potential in monitoring the emerging food safety risks.

Label-free and "signal-on" homogeneous photoelectrochemical cytosensing strategy for ultrasensitive cancer cell detection

We report a label-free and "signal-on" homogeneous photoelectrochemical cytosensing system for ultrasensitive detection of cancer cells, which is a truly homogeneous PEC cytosensing system without the photoactive material immobilization and target recognition probe modification, providing a new avenue in early and accurate cancer diagnosis and clinical analysis.

Dendrimer-Au Nanoparticle Network Covered Alumina Membrane for Ion Rectification and Enhanced Bioanalysis

Ion transport in an artificial asymmetric nanoporous membrane, which is similar to biological ion channels, can be used for biosensing. Here, a dendrimer-Au nanoparticle network (DAN) is in situ assembled on a nanoporous anodic aluminum oxide (AAO) surface, forming a DAN/AAO hybrid membrane. Benefiting from the high surface area and anion selectivity of DAN, the prepared DAN/AAO hybrid presents selective ion transport. Under a bias potential, a diode-like current-potential (I-V) response is observed. The obtained ionic current rectification (ICR) property can be tuned by the ion valence and pH value of the electrolyte. The rectified ionic current endows the as-prepared DAN/AAO hybrid with the ability of enhanced bioanalysis. Sensitive capture and detection of circulating tumor cells (CTCs) with a detection limit of 80 cells mL^-1 as well as excellent reusability can be achieved.

A high-energy sandwich-type self-powered biosensor based on DNA bioconjugates and a nitrogen doped ultra-thin carbon shell

A high-energy self-powered sensing platform for the ultrasensitive detection of proteins is developed based on enzymatic biofuel cells (EBFCs) by using DNA bioconjugate assisted signal amplification.

Nanotechnology in cancer diagnosis: progress, challenges and opportunities

In the fight against cancer, early detection is a key factor for successful treatment. However, the detection of cancer in the early stage has been hindered by the intrinsic limits of conventional cancer diagnostic methods. Nanotechnology provides high sensitivity, specificity, and multiplexed measurement capacity and has therefore been investigated for the detection of extracellular cancer biomarkers and cancer cells, as well as for in vivo imaging. This review summarizes the latest developments in nanotechnology applications for cancer diagnosis. In addition, the challenges in the translation of nanotechnology-based diagnostic methods into clinical applications are discussed.

Highly sensitive detection of microcystin-LR under visible light using a self-powered photoelectrochemical aptasensor based on a CoO/Au/g-C3N4 Z-scheme heterojunction

Based on the unique photoelectrochemical properties of a CoO/Au/g-C₃N₄ Z-scheme heterojunction, a self-powered photoelectrochemical (PEC) aptasensor was constructed for the detection of microcystin-leucine arginine (MC-LR). Z-scheme heterojunctions can promote the separation of a photo-induced electron-hole pair, and the surface plasmonic resonance (SPR) of Au nanoparticles can significantly enhance the adsorption of visible light. Importantly, MC-LR molecules were captured by aptamers initially immobilized on the modified electrode due to their high affinity, and then oxidized by the photogenerated holes, which caused an amplified photocurrent signal, allowing the quantitative analysis of MC-LR by measuring the photocurrent intensity change. This PEC MC-LR aptasensor showed high sensitivity and selectivity within a wide linear response range from 0.1 pM to 10 nM and a detection limit of 0.01 pM. The application of this sensor in the analysis of lake water samples provided accurate results with a relative standard deviation (RSD) of 2.6%-4.2%.

Metal-organic frameworks-derived MnO2/Mn3O4 microcuboids with hierarchically ordered nanosheets and Ti3C2 MXene/Au NPs composites for electrochemical pesticide detection

Transition metal oxides (TMOs) derived from metal - organic frameworks (MOF) combined with two-dimensional (2D) transition metal carbides possibly pave an innovative pathway for designing promising biosensors. Herein, a novel electrochemical sensing platform has been fabricated for ultra-sensitive determination of organophosphorus pesticides (OPs), based on MOF-derived MnO₂/Mn₃O₄ and Ti₃C₂ MXene/Au NPs composites. Remarkably, the three-dimensional (3D) MnO₂/Mn₃O₄ hierarchical microcuboids derived from Mn-MOF are composed of vertically aligned, highly ordered nanosheets, and further combined with MXene/Au NPs yields synergistic signal amplification effect, with outstanding electrochemical performance, large specific surface area, and good environmental biocompatibility. Under the optimum conditions, the reported sensing platform AChE-Chit/MXene/Au NPs/MnO₂/Mn₃O₄/GCE can be utilized to detect methamidophos in a broad concentration range (10^-12-10^-6 M), together with a good linearity (R = 0.995). Besides that, the biosensor possesses a low limit of detection (1.34 × 10^-13 M), which far exceeds the maximum residue limits (MRLs) for methamidophos (0.01 mg/kg) established by European Union. Additionally, the feasibility of the proposed biosensor for detecting methamidophos in real samples has been demonstrated with excellent recoveries (95.2%-101.3%). Interestingly, the unique structures and remarkable properties of these composites make them attractive materials for various electrochemical sensors for monitoring either pesticide residuals or other environmentally deleterious chemicals.

Decontamination and disinfection of wastewater by photocatalysis under UV/visible light using nano-catalysts based on Ca-doped ZnO

Nano-catalysts based on ZnO-Ca x% (with x = 0, 0.1, 0.3, 0.5, 0.7, and 1.0 mol % Ca²⁺) were synthesized with a bio-friendly adaptation of the sol-gel method using gelatin as template. These materials were characterized by Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Micro-Raman, transmission electron microscopy (TEM), scanning electron microscopy (SEM), N₂ physisorption, photoacoustic absorption spectroscopy (PAS), and photoluminescence spectroscopy (PL). The Raman results indicated that the signal, attributed to an E₁(LO) mode at 580 cm^-1, was characteristic of oxygen vacancies that decreased with the increased Ca²⁺ content in doped oxides. This agreed with the PL results, which showed that the green emission centered at 510 nm and attributable to structural defects in ZnO decreased for Ca-doped ZnO. Our oxides are constituted by nanoparticles with rod-like and spherical morphologies. All the nano-catalysts exhibited the band gap characteristics of semiconductor materials around 3.0 eV. ZnO-Ca 1.0% exhibited the best photocatalytic performance for degradation of Methyl Orange (MO) model dye, degrading about 82% after 240 min of UV-Vis irradiation at pH 7.0. The reaction mechanism was influenced by hydroxyl (OH) and superoxide (O₂^-) radicals and mainly by active holes (h⁺). This doped oxide also demonstrated efficiency in wastewater disinfection against heterotrophic bacteria and total coliforms, exhibiting a potential use as an antimicrobial agent for the treatment of hospital wastewater. Furthermore, our nanoparticles did not show significant cytotoxic effects on L929 fibroblast cells.

A label-free PFP-based photoelectrochemical biosensor for highly sensitive detection of PARP-1 activity

Poly(ADP-ribose) polymerase-1 (PARP-1), as an original tumor marker, has aroused wide attention in recent years. However, only a few researches have been done for PARP-1 activity detection because PARP-1 is lack of optical or electrochemical property. In this work, a label-free and high-sensitive photoelectrochemical (PEC) biosensor for PARP-1 activity detection based on poly[9,9-bis(6'-N,N,N-trimethylammonium)hexyl]fluorenylene phenylene (PFP) has been designed. To the best of our knowledge, it is the first time that PEC has been used to monitor PARP-1 activity. PARP-1 were activated under the function of activated dsDNA, as a result, branched polymers of ADP-ribose (PAR) with plentiful negative charge were formed in the presence of nicotinamide adenine dinucleotide (NAD⁺). Subsequently, positively charged PFP with good photoelectrochemical properties, were absorbed on PAR via electrostatic interaction. High photocurrent was produced under light induction, which was depended on the PARP-1 activity. The biosensor has a wide linear range from 0.01 to 2 U with a detection limit of 0.007 U. The strategy has been applied in breast and ovarian cancer cells to detection PARP-1 activity with approving results, which signifies that it is a promising tool for clinical diagnosis.

Photocatalytic removal using g-C3N4 quantum dots/Bi2Ti2O7 composites

In this work, a simple method to load of g-C₃N₄ quantum dots (CN QDs) onto Bi₂Ti₂O₇ (BTO) microsphere with the amount of CN QDs (3, 7, 10 and 15%). The photocatalyst was used for the treatment of water pollutants under visible-light illumination, which proved that CNBTO composites showed improved photocatalytic activity matched up to pure BTO. Reformation of BTO with CN QDs enhanced the light assimilation capacity, and promoted the isolation of photo-induced electron-hole pairs. The trapping experiments and ESR were announced the holes (h⁺) and superoxide oxide (O₂^-) played the key role, and the relative mechanism of the photocatalytic process was proposed. Meanwhile, the effects of CN QDs content, pH and initial pollutant concentration on the removal efficiency of ciprofloxacin (CIP) were studied. Results showed that the CN QDs loaded on BTO presented higher photocatalytic efficiency, and an optimum value for the dosage of photocatalytic in pH 8.0.

Direct Plasmon-Enhanced Electrochemistry for Enabling Ultrasensitive and Label-Free Detection of Circulating Tumor Cells in Blood

In this work, we developed a simple electrochemical method for ultrasensitive and label-free detection of circulating tumor cells (CTCs) based on direct plasmon-enhanced electrochemistry (DPEE). After plasmonic gold nanostars (AuNSs) were modified on the glassy carbon (GC) electrode, the aptamer probe was immobilized on the AuNSs surface, which can selectively capture the CTCs in samples. Upon localized surface plasmon resonance (LSPR) excitation, the electrochemical current response can be enhanced remarkably due to efficient hot electrons transport from AuNSs to the external circuit. The captured cells on the AuNSs surface will influence the hot electrons transport efficiency, leading to a decreased current response. Using ascorbic acid (AA) as the electroactive probe, it was found that the current responses of the AuNSs/GC electrode upon light irradiation decrease with the cell concentration. Due to the special molecular recognition of the aptamer and enhanced electrochemical performance of the plasmon, the proposed method enables an ultrasensitive and label-free detection of CTCs with excellent selectivity. The experimental results show that CCRF-CEM cell concentrations as low as 5 cells/mL can be successfully detected, which is superior to most reported work up to now. Using the present method, MCF-7 cells as low as 10 cells/mL can be also successfully detected, indicating the universality of the proposed method for CTCs detection. Furthermore, the cytosensor can successfully distinguish CTCs from normal cells in blood samples. The as-proposed strategy provides a promising application of DPEE in the development of novel biosensors for nondestructive analysis of biological samples.

Light-driven ultrasensitive self-powered cytosensing of circulating tumor cells via integration of biofuel cells and a photoelectrochemical strategy

Herein, a light-driven, membrane-less and mediator-less self-powered cytosensing platform via integration of biofuel cells (BFCs) and a photoelectrochemical strategy was developed for ultrasensitive detection of circulating tumor cells (CTCs). To construct cytosensors, an elaborately designed SH-Sgc8c aptamer/AuNP/g-C₃N₄ photoelectrode was used as an alternative anode for glucose oxidation, avoiding the introduction of anodic enzymes. Initially, glucose could favorably reach the photoanode surface and be easily oxidized by the photogenerated holes, while the photogenerated electrons would transfer to the biocathode and achieve biocatalytic reduction of O₂, leading to a high E^OCV. However, in the presence of CTCs, they could preferentially interact with the Sgc8c aptamer via specific recognition, and then complexes with large steric hindrance were immobilized on the photoanode surface, which could greatly affect the electron transfer between glucose and the photoanode surface. In this case, the E^OCV decreased sharply. Encouragingly, this self-powered cytosensor exhibited an ultrasensitive response to the target CTCs in a wide concentration range from 20 to 2 × 10⁵ cells mL^-1 with a low detection limit of 10 cells mL^-1 (S/N = 3), being superior to those of the reported methods. Moreover, this as-proposed self-powered cytosensor integrated with a photoelectrochemical strategy possessed unique advantages of not requiring an external power source, being anodic enzyme-free, having a simple construction process, facile miniaturization, and high selectivity and sensitivity, providing a promising and powerful tool for fundamental biochemical research and clinical diagnosis.

Facile Synthesis of Cu2O@TiO2-PtCu Nanocomposites as a Signal Amplification Strategy for the Insulin Detection

Novel ultrasensitive sandwich-type electrochemical immunosensor was proposed for the quantitative detection of insulin, a representative biomarker for diabetes. To this end, molybdenum disulfide nanosheet-loaded gold nanoparticles (MoS₂/Au NPs) were used as substrates to modify bare glassy carbon electrodes. MoS₂/Au NPs not only present superior biocompatible and large specific surface area to enhance the loading capacity of primary antibody (Ab₁) but also present good electrical conductivity to accelerate electron transfer rate. Moreover, the amino-functionalized cuprous oxide decorated with titanium dioxide octahedral composites (Cu₂O@TiO₂-NH₂) were prepared to load dendritic platinum-copper nanoparticles (PtCu NPs) to realize signal amplification strategy. The resultant nanocomposites (cuprous oxide decorated with titanium dioxide octahedral loaded dendritic platinum-copper nanoparticles) demonstrate uniform octahedral morphology and size, which effectively increases the catalytically active sites and specific surface area to load the secondary antibody (Ab₂), even increases conductivity. Most importantly, the resultant nanocomposites possess superior electrocatalytic activity for hydrogen peroxide (H₂O₂) reduction, which present the signal amplification strategy. Under the optimal conditions, the proposed immunosensor exhibited a linear relationship between logarithm of insulin antigen concentration and amperometric response within a broad range from 0.1 pg/mL to 100 ng/mL and a limit detection of 0.024 pg/mL. Meanwhile, the immunosensor was employed to detect insulin in human serum with satisfactory results. Furthermore, it also presents good reproducibility, selectivity, and stability, which exhibits broad application prospects in biometric analysis.

Fabrication of a novel and ultrasensitive label-free electrochemical aptasensor for detection of biomarker prostate specific antigen

In this study, a novel and efficient aptasensor based on immobilization of thiol terminated prostate specific antigen (PSA) binding DNA aptamer onto Au nanoparticles/fullerene C₆₀-chitosan-ionic liquid/multiwalled carbon nanotubes/screen printed carbon electrode has been fabricated for ultrasensitive aptasensing of biomarker PSA. Formation of PSA-aptamer complex caused a variation in electrochemical impedance spectroscopic (EIS) and differential pulse voltammetric (DPV) responses of the aptasensor which enabled us to aptasensing of the PSA by EIS and DPV methods. Morphology and electrochemical properties of the fabricated aptasensor were examined by scanning electron microscopy (SEM), cyclic voltammetry (CV) and EIS. The aptasensor was successfully applied to the determination of PSA by EIS and DPV in the range of 1-200 pg mL^-1 with a limit of detection (LOD) of 0.5 pg mL^-1 and 2.5-90 ng mL^-1 with a LOD of 1.5 ng mL^-1, respectively. This aptasensor exhibited outstanding anti-interference ability towards co-existing molecules with good stability, sensitivity, repeatability and reproducibility. Practical application of the aptasensor was examined with analysis of the PSA levels in serum samples obtained from patients with prostate cancer using both the aptasensor and a reference method. The results revealed the proposed system to be a promising candidate for clinical analysis of PSA.

Red light-driven photoelectrochemical biosensing for ultrasensitive and scatheless assay of tumor cells based on hypotoxic AgInS2 nanoparticles

A novel red light-driven photoelectrochemical (PEC) biosensing platform based on hypotoxic ternary mercaptopropionic acid (MPA)-capped AgInS₂ nanoparticles (NPs) with excellent hydrophily and biocompatibility was proposed. AgInS₂ NPs as a PEC sensing substrate exhibited high photon-to-current conversion efficiency under red light excitation, generating an intensive photocurrent for enhancing the sensitivity of PEC determination. After the introduction of the amino-terminated sgc8c aptamer onto the interface of AgInS₂ NPs, the overexpressed protein tyrosine kinase-7 on the surface of lymphoblast CCRF-CEM cells could be efficiently captured. Using CCRF-CEM cell as a model analyte, an ultrasensitive PEC biosensor for scatheless assay of cells at the applied potential of 0.15 V under a red light excitation of 630 nm was designed based on the significant decline of photocurrent intensity after capturing CCRF-CEM cells. The developed PEC cytosensor demonstrated an excellent cell-capture ability, as well as a wide linear range from 1.5 × 10² to 3.0 × 10⁵ cells/mL and a low detection limit of 16 cells/mL for CCRF-CEM cells. In addition, the resulting assay method verified high selectivity and negligible cytotoxicity for cells assay. This work provided an alternative method for scatheless assay of tumor cells, which would have promising prospect in clinical diagnoses of cancer.