Nanomaterials and paper-based electrochemical devices: merging strategies for fostering sustainable detection of biomarkers

Development of a highly sensitive CNT-metal graphene hybrid nano-IDA electrochemical biosensor for the diagnosis of Alzheimer's disease

The blood-based detection of Alzheimer's disease (AD) is becoming challenging since the blood-brain barrier (BBB) restricts the direct circulation of AD molecules in the blood, thereby precluding the detection of AD at an early-stage. Herein, we report the development of a novel CNT-metal-porous graphene hybrid (CNT-MGH) nano-interdigitated array (n-IDA) electrochemical 8-well biosensor for the successful early-stage diagnosis of AD from blood. Laser-induced graphene (LIG) technology has been used to fabricate the proposed CNT-MGH n-IDA 8-well sensor. Firstly, the electrochemical characterization (i.e., electrode gap, material composition, etc.) of the proposed sensor was demonstrated by measuring p-aminophenol (PAP) with a limit of detection (LOD) of 0.1 picomole. Subsequently, the CNT-MGH n-IDA 8-well sensor was then used to diagnose AD via novel blood biomarkers p-Tau 217 and p-Tau 181 using an electrochemical enzyme-linked immunosorbent assay (e-ELISA) enzyme by-product PAP. During e-ELISA, the alkaline phosphatase enzyme (IgG-AP) tagged to the detection antibody produced an electroactive ELISA by-product PAP by reacting with the enzyme-substrate 4-aminophenyl phosphate (PAPP). Finally, the CNT-MGH n-IDA 8-well sensor was then used to measure the current generated by the redox reaction via the e-ELISA by-product PAP. While quantified, the proposed CNT-MGH n-IDA 8-well sensor successfully detected p-Tau 217 and p-Tau 181 proteins in blood with LODs of 0.16 pg ml-1 and 0.08 pg ml-1, respectively.

Electrocatalytic FeFe2O4 embedded, spermine-imprinted polypyrrole (Fe/MIPpy) nanozymes for cancer diagnosis and prognosis

Developing synthetic materials, with enzyme-like molecular recognition capabilities, as functional receptors in electronic or electrochemical devices for the timely diagnosis of major diseases is a great challenge. Herein, we present the development of Fe/MIPpy nanozymes, characterized as enzyme-like artificial receptors, for the precise and non-invasive monitoring of cancer biomarkers in aqueous solutions and human saliva. Through the integration of PVA-stabilized FeFe2O4 nanocrystals in a molecularly imprinted conducting polypyrrole matrix, the Fe/MIPpy nanozymes demonstrate 424 nA cm-2 nM-1 sensitivity and 220 pM detection limit. Charge-transfer mechanisms, Fe/MIPpy-spermine interactions, and the principle of spermine recognition are investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The disposable Fe/MIPpy sensor operates wirelessly and offers rapid and remote quantification of spermine, making it a promising material for the development of cost-effective tools for non-invasive cancer diagnosis and prognosis.

Electrochemical and optical (bio)sensors for analysis of antibiotic residuals

Antibiotic residuals in foods may lead to crucial health and safety issues in the human body. Rapid and in-time analysis of antibiotics using simple and sensitive techniques is in high demand. Among the most commonly applicable modalities, chromatography-based techniques like HPLC and LC-MS, along with immunological approaches, particularly ELISA have been exampled in the analysis of antibiotics. Despite being highly sensitive, these methods are considerably time-consuming, thus the presence of skilled personnel and costly equipment is essential. Nanomaterial-based (bio)sensors, however, are de novo analytical equipment with some beneficial characteristics, such as simplicity, low price, on-site, high accuracy, and sensitivity for the detection of analytes. This review aimed to collect the latest developments in NM-based sensors and biosensors for the observation of highly used antibiotics like Vancomycin (Van), Linezolid (Lin), and Clindamycin (Clin). The current challenges and developmental perspectives are also debated in detail for future research directions.

Paper as smart support for bioreceptor immobilization in electrochemical paper-based devices

The use of paper as a smart support in the field of electrochemical sensors has been largely improved over the last 15 years, driven by its outstanding features such as foldability and porosity, which enable the design of reagent and equipment-free multi-analysis devices. Furthermore, the easy surface engineering of paper has been used to immobilize different bioreceptors, through physical adsorption, covalent bonding, and electrochemical polymerization, boosting the fine customization of the analytical performances of paper-based biosensors. In this review, we focused on the strategies to engineer the surface of the paper for the immobilization of (bio)recognition elements (eg., enzymes, antibodies, DNA, molecularly imprinted polymers) with the overriding goal to develop accurate and reliable paper-based electrochemical biosensors. Furthermore, we highlighted how to take advantage of paper for designing smart configurations by integrating different analytical processes in an eco-designed analytical tool, starting from the immobilization of the (bio)receptor and the reagents, through a designed sample flow along the device, until the analyte detection.

Nanomaterials in tumor immunotherapy: new strategies and challenges

Tumor immunotherapy exerts its anti-tumor effects by stimulating and enhancing immune responses of the body. It has become another important modality of anti-tumor therapy with significant clinical efficacy and advantages compared to chemotherapy, radiotherapy and targeted therapy. Although various kinds of tumor immunotherapeutic drugs have emerged, the challenges faced in the delivery of these drugs, such as poor tumor permeability and low tumor cell uptake rate, had prevented their widespread application. Recently, nanomaterials had emerged as a means for treatment of different diseases due to their targeting properties, biocompatibility and functionalities. Moreover, nanomaterials possess various characteristics that overcome the defects of traditional tumor immunotherapy, such as large drug loading capacity, precise tumor targeting and easy modification, thus leading to their wide application in tumor immunotherapy. There are two main classes of novel nanoparticles mentioned in this review: organic (polymeric nanomaterials, liposomes and lipid nanoparticles) and inorganic (non-metallic nanomaterials and metallic nanomaterials). Besides, the fabrication method for nanoparticles, Nanoemulsions, was also introduced. In summary, this review article mainly discussed the research progress of tumor immunotherapy based on nanomaterials in the past few years and offers a theoretical basis for exploring novel tumor immunotherapy strategies in the future.

Optimized paper-based electrochemical sensors treated in acidic media to detect carbendazim on the skin of apple and cabbage

Wearable sensors such as those made with paper are needed for non-destructive routine analysis of pesticides on plants, fruits, and vegetables. Herein we report on electrochemical sensors made with screen-printed carbon electrodes on kraft and parchment papers to detect the fungicide carbendazim. A systematic optimization was performed to find that electrochemical sensors on kraft paper treated in an acidic medium led to the highest performance, with a detection limit of 0.06 µM for carbendazim. The enhanced sensitivity for this sensor was attributed to the porous nature of kraft paper, which allowed for a large electrode surface area, and to the carboxylic groups formed during electrochemical activation. As a proof-of-concept, the electrochemical sensor attached to the skin of apple and cabbage was used to detect carbendazim with the same performance as the gold standard method, thus demonstrating that the sensor can be used in the farm and on supermarket shelves.

Paper card-like electrochemical platform as a smart point-of-care device for reagent-free glucose measurement in tears

This communication describes the development of polyvinyl chloride electrochemical system in which a paper layer loaded with reagents is inserted into the device, demonstrating a new concept of a paper card-like pad for a reagent-free and easy measurement of the target analyte in solution. This device detects glucose in artificial tears in the range of 0.2-2 mM with a detection limit of 50 μM by simply adding the artificial tears to the paper card-like pad. The novel configuration goes beyond the state of the art, widening the application range of paper in the design of smart analytical devices.

Nanomaterials: Breaking through the bottleneck of tumor immunotherapy

Immunotherapy exerts its excellent anti-tumor effects by stimulating and enhancing the immune response of the body, and has become another important class of anti-tumor therapy besides chemotherapy, targeted therapy and radiotherapy. Various types of immunotherapeutic drugs have gained their clinical values, but the in vivo delivery of drugs still faces many challenges, such as poor tumor permeability and low tumor cell uptake rate. In recent years, owing to highly targeting properties, better biocompatibility, and easy functionalization, nanomaterials have been widely applicated in tumor treatment, especially in tumor immunotherapy. Furthermore, nanomaterials have large drug loading capacity, strong tumor targeting and easy modification, which can effectively overcome the drawbacks of traditional immunotherapy. This paper reviews the progress of nanomaterial-based tumor immunotherapy in recent years and provides a theoretical basis for exploring new nanomaterial-based tumor immunotherapy strategies.

A smart paper-based electrochemical sensor for reliable detection of iron ions in serum

The fast-growing healthcare demand for user-friendly and affordable analytical tools is driving the efforts to develop reliable platforms for the customization of therapy based on individual health conditions. In this overall scenario, we developed a paper-based electrochemical sensor for the quantification of iron ions in serum as a cost-effective sensing tool for the correct supplement administration. In detail, the working electrode of the screen-printed device has been modified with a nanocomposite constituted of carbon black and gold nanoparticles with a drop-casting procedure. Square wave voltammetry has been adopted as an electrochemical technique. This sensor was further modified with Nafion for iron quantification in serum after sample treatment with trifluoroacetic acid. Under optimized conditions, iron ions have been detected with a LOD down to 0.05 mg/L and a linearity up to 10 mg/L in standard solution. The obtained results have been compared with reference methods namely commercial colorimetric assay and atomic absorption spectroscopy, obtaining a good correlation within the experimental errors. These results demonstrated the suitability of the developed paper-based sensor for future applications in precision medicine of iron-deficiency diseases.