A highly sensitive competitive immunosensor based on branched polyethyleneimine functionalized reduced graphene oxide and gold nanoparticles modified electrode for detection of melamine

Functionalized graphene oxide as a nanocarrier for delivering oridonin to improve anti-breast cancer cell activity

In this study, a targeted nanocarrier was developed by functionalizing graphene oxide with polyethyleneimine and folic acid, intended for loading oridonin. The nanocarrier was successfully synthesized and characterized using an ultraviolet spectrum, Fourier transform infrared spectroscopy and scanning electron microscopy. The nanocarrier demonstrated a remarkable oridonin loading capacity, reaching 424.8 μg/mg, as determined by ultra-high performance liquid chromatography. In vitro drug release experiments exhibited a pH-dependent release profile, with a higher cumulative release in an acidic environment. The release mechanism followed the Ritger-Peppas equation model. Cytotoxicity assays indicated minimal toxicity of the nanocarrier. Enhanced cellular uptake by MCF7 cells was observed for carriers functionalized with folate and polyethyleneimine. These findings highlight the potential of functionalized graphene oxide as a promising carrier for oridonin delivery in biomedical applications.

A new difunctional liquid crystal nanosurface molecularly imprinted polyitaconic acid nanoprobe for SERS/RRS determination of ultratrace melamine

In this paper, a new dimode scattering spectral method for rapid detection of ultratrace melamine (ML) in dairy products was established by coupling nanosurface molecular imprinting technology with nanocatalytic amplification reaction of liquid crystal particles. It was found that liquid crystal cholesteryl butyrate (CBU) nanosurface imprinted polymers (CBU@MIP) not only recognized ML but also catalyzed the nano indicator reaction of HAuCl4-sodium formate to produce gold nanoparticles with surface-enhanced Raman scattering (SERS) and resonance Rayleigh scattering (RRS) effect. When ML was added, it specifically combined with CBU@MIP to form CBU@MIP-ML conjugates with strong catalytic activity, and SERS and RRS signals increased linearly with the detection limits of 0.0072 pmol/L and 0.093 pmol/L respectively. The method was applied to the determination of ML in dairy products and plastic tablewares with relative standard deviation (RSD) of 2.2-4.4 % and 1.6-4.7 %, and recovery of 95.4 %-108.3 % and 95.9-108.6  % respectively.

A novel sensor based on Ti3C2 MXene/Co3O4/carbon nanofibers composite for the sensitive detection of 4-aminophenol

A novel, sensitive Ti3C2 MXene/Co3O4/carbon nanofibers (Ti3C2 MXene/Co3O4/CNFs) composite was synthesized via a HF exfoliating Ti3AlC2 strategy, followed by doping Co3O4 and Ti3C2 MXene into the CNFs via a combination electrospinning and thermal annealing process. Ti3C2 MXene/Co3O4/CNFs composite exhibits higher catalytic effect, conductivity, chemical stability, and electrochemical performance than Co3O4 and Ti3C2 MXene in electrochemical impedance, differential pulse stripping voltammetry, chronocoulometry, and cyclic voltammetry tests. This Ti3C2 MXene/Co3O4/CNFs hybrid modified electrode provides fast analysis of 4-aminophenol (4-AP) with ultrahigh sensitivity, enhanced reproducibility and strong anti-interference capability. Furthermore, the level of 4-AP was quantified by this electrode with a wide linear range from 0.5 to 150 μM (R2 > 0.99) and a low detection limit about 0.018 μM was achieved. Finally, the fabricated electrode was used for fast and sensitive analysis of 4-AP spiked in tap water and blood serum samples. This work presents the new Ti3C2 MXene/Co3O4/CNFs electrode provides a platform for 4-AP monitoring and has the advantages of high selectivity, accuracy, simplicity, and rapid analysis.

Strategies for Improving Selectivity and Sensitivity of Schiff Base Fluorescent Chemosensors for Toxic and Heavy Metals

Toxic cations, including heavy metals, pose significant environmental and health risks, necessitating the development of reliable detection methods. This review investigates the techniques and approaches used to strengthen the sensitivity and selectivity of Schiff base fluorescent chemosensors designed specifically to detect toxic and heavy metal cations. The paper explores a range of strategies, including functional group variations, structural modifications, and the integration of nanomaterials or auxiliary receptors, to amplify the efficiency of these chemosensors. By improving selectivity towards targeted cations and achieving heightened sensitivity and detection limits, consequently, these strategies contribute to the advancement of accurate and efficient detection methods while increasing the range of end-use applications. The findings discussed in this review offer valuable insights into the potential of leveraging Schiff base fluorescent chemosensors for the accurate and reliable detection and monitoring of heavy metal cations in various fields, including environmental monitoring, biomedical research, and industrial safety.

One step construction of an electrochemical sensor for melamine detection in milk towards an integrated portable system

Excessive intake of melamine (MEL) can be harmful to human health, and it is important to establish a rapid and accurate MEL detection method. As the electrochemical activity of MEL is very low, ferrocenylglutathione (Fc-ECG) was used as an electron transfer mediator to assist with the detection of MEL using screen-printed carbon electrode (SPCE). This modified electrode (MEL/Fc-ECG/SPCE) was prepared by stepwise drop-casting and was fully characterized. Results showed that MEL significantly enhanced signal of Fc-ECG/SPCE sensor due to the three p-π conjugated double bonds that facilitated electron transfer. Under optimal conditions, the sensor exhibits two linearities in the range of 0.20-2.00 μM and 8.00-800 μM, with a sensitivity of 15.03 μA·μM^-1·cm^-2. The selectivity, stability, and reproducibility were investigated and successfully used to detect MEL in raw milk and confirms safety verification of foods. Moreover, a portable testing platform was designed for MEL detection based on a CH32 chip.

Green syntheses of graphene and its applications in internet of things (IoT)-a status review

Internet of Things (IoT) is a trending technological field that converts any physical object into a communicable smarter one by converging the physical world with the digital world. This innovative technology connects the device to the internet and provides a platform to collect real-time data, cloud storage, and analyze the collected data to trigger smart actions from a remote location via remote notifications, etc. Because of its wide-ranging applications, this technology can be integrated into almost all the industries. Another trending field with tremendous opportunities is Nanotechnology, which provides many benefits in several areas of life, and helps to improve many technological and industrial sectors. So, integration of IoT and Nanotechnology can bring about the very important field of Internet of Nanothings (IoNT), which can re-shape the communication industry. For that, data (collected from trillions of nanosensors, connected to billions of devices) would be the 'ultimate truth', which could be generated from highly efficient nanosensors, fabricated from various novel nanomaterials, one of which is graphene, the so-called 'wonder material' of the 21st century. Therefore, graphene-assisted IoT/IoNT platforms may revolutionize the communication technologies around the globe. In this article, a status review of the smart applications of graphene in the IoT sector is presented. Firstly, various green synthesis of graphene for sustainable development is elucidated, followed by its applications in various nanosensors, detectors, actuators, memory, and nano-communication devices. Also, the future market prospects are discussed to converge various emerging concepts like machine learning, fog/edge computing, artificial intelligence, big data, and blockchain, with the graphene-assisted IoT field to bring about the concept of 'all-round connectivity in every sphere possible'.

A novel aptamer RRS assay platform for ultratrace melamine based on COF-loaded Pd nanocluster catalytic amplification

Two COFs of BzBD and BzBD loaded Pd nanoclusters (BzBD_Pd) were prepared using 1,3,5-benzenetricarboxaldehyde (Bz), benzidine (BD) and CO reducing agent, and were characterized by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), infrared spectroscopy (IR) and other techniques. BzBD_Pd can strongly catalyze the new and stable Au@NiP nanoreaction that exhibit a strong resonance Rayleigh scattering (RRS) peak at 538 nm and a surface plasmon resonance (SPR) absorption peak at 395 nm, and the sensitive and facile RRS technique was used to study the indicator reaction. Combining the nanocatalytic amplification reaction with specific aptamer (Apt) of some target molecules such as melamine (ML), urea (UR) and bisphenol A (BPA), a simple, sensitive and selective Apt RRS assay platform was established. The linear range of the RRS detection platform for melamine is 0.0025-0.04 nmol/L, and the detection limit (DL) is 1.96 × 10^-4 nmol/L. In addition, ML in real sample was analyzed, the stability of BzBD, BzBD_Pd, PdNPs and the catalytic mechanism of COF_Pd were also considered.

Electrochemical sensing of nitrofurazone on Ru(bpy)32+ functionalized polyoxometalate combined with graphene modified electrode

Nitrofurazone is forbidden to be used in aquaculture, but it is often used illegally because of its good bactericidal effect, and its content in animals is extremely low and difficult to detect directly. Hence, a functionalized polyoxometalate combined with graphene modified electrodes through layer-by-layer assembly has achieved a sensitive detection of nitrofurazone in a pH = 6 Na₂HPO₄-citrate buffer solution and its detection limit as low as 0.08952 μM. Nitrofurazone has accelerated its electron transfer through [Ru-PMo₁₂/PDDA-GO]₃ modified electrode, thus realizing its direct detection at low levels through actual samples. This study provides a new perspective for the direct detection of nitrofurazone by electrochemical methods, which is of great significance for the supervision of nitrofurazone and the improvement of the quality and safety of aquatic products.

An Electrochemical Immunosensor Based on SPA and rGO-PEI-Ag-Nf for the Detection of Arsanilic Acid

A sensitive electrochemical immunosensor was prepared for rapid detection of ASA based on arsanilic acid (ASA) monoclonal antibody with high affinity. In the preparation of nanomaterials, polyethyleneimine (PEI) improved the stability of the solution and acted as a reducing agent to generate reduced graphene oxide (rGO) with relatively strong conductivity, thereby promoting the transfer of electrons. The dual conductivity of rGO and silver nanoparticles (AgNPs) improved the sensitivity of the sensor. The synthesis of nanomaterials were confirmed by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. In the optimal experiment conditions, the sensor could achieve the detection range of 0.50–500 ng mL⁻¹ and the limit of detection (LOD) of 0.38 ng mL⁻¹ (S/N = 3). Moreover, the sensor exhibited excellent specificity and acceptable stability, suggesting that the proposed sensor possessed a good potential in ASA detection. Thus, the as-prepared biosensor may be a potential way for detecting other antibiotics in meat and animal-derived foods.

Application of Functionalized Graphene Oxide Based Biosensors for Health Monitoring: Simple Graphene Derivatives to 3D Printed Platforms

Biosensors hold great potential for revolutionizing personalized medicine and environmental monitoring. Their construction is the key factor which depends on either manufacturing techniques or robust sensing materials to improve efficacy of the device. Functional graphene is an attractive choice for transducing material due to its various advantages in interfacing with biorecognition elements. Graphene and its derivatives such as graphene oxide (GO) are thus being used extensively for biosensors for monitoring of diseases. In addition, graphene can be patterned to a variety of structures and is incorporated into biosensor devices such as microfluidic devices and electrochemical and plasmonic sensors. Among biosensing materials, GO is gaining much attention due to its easy synthesis process and patternable features, high functionality, and high electron transfer properties with a large surface area leading to sensitive point-of-use applications. Considering demand and recent challenges, this perspective review is an attempt to describe state-of-the-art biosensors based on functional graphene. Special emphasis is given to elucidating the mechanism of sensing while discussing different applications. Further, we describe the future prospects of functional GO-based biosensors for health care and environmental monitoring with a focus on additive manufacturing such as 3D printing.

Detection of Cu2+ and S2- with fluorescent polymer nanoparticles and bioimaging in HeLa cells

Novel spherical polymer nanoparticles were synthesized by hyperbranched polyethylenimine (hPEI) and 6-hydroxy-2-naphthaldehyde (HNA) via Schiff base reaction (one-pot reaction), which had great advantages in water solubility and green synthesis. Meanwhile, probe PEI-HNA could quickly detect Cu²⁺ in the range of 0-60 μM in 30 s with the detection limit of 243 nM. The fluorescence of PEI-HNA-Cu²⁺ could be recovered by the addition of S^2- in 50 s with the detection limit of 227 nM. Based on the excellent optical properties, PEI-HNA has been used in the bioimaging of living cells with excellent cell penetrability and low toxicity. More importantly, PEI-HNA has been doped into filter paper, hydrogel, and nanofibrous film to prepare solid-phase sensors, displaying rapid response and excellent sensitivity. Moreover, the low-cost and simple preparation of these sensors offers great potential and possibilities for industrialization, which could help accelerate the development of sensors in environmental and biological fields.

Synthesis of biological quantum dots based on single-strand DNA and its application in melamine detection

By taking TC base-rich single-stranded DNA (ssDNA) as the raw material, a fluorescent biological quantum dots (Bio-dots) probe was prepared in one step through hydrothermal method, where its lifetime was greatly extended in comparison with Carbon quantum dots (CQDs), reaching 10.7 ns. The fluorescent detection of melamine in milk samples was realized by using the base pairing principle. Under the optimal conditions, the linear range of Bio-dots probe fluorescence sensor for melamine detection is 5-600 μM, and the detection limit is (3σ) 1.4 μM. Bio-dots can not only emit photoluminescence, but also detect target molecules as a functional recognition group. As the raw material ssDNA was basically non-toxic and there was no toxic substances participated in its synmanuscript process, this Bio-dots probe was a kind of green and environmentally-friendly photoluminescent functional material.

Magnetic nanomaterials based electrochemical (bio)sensors for food analysis

It is widely accepted that nanotechnology attracted more interest because of various values that nanomaterial applications offers in different fields. Recently, researchers have proposed nanomaterials based electrochemical sensors and biosensors as one of the potent alternatives or supplementary analytical tools to the conventional detection procedures that consumes a lot of time. Among different nanomaterials, researchers largely considered magnetic nanomaterials (MNMs) for developing and fabricating the electrochemical (bio)sensors for numerous utilizations. Among several factors, healthier and higher quality foods are the most important preferences of consumers and manufacturers. For this reason, developing new techniques for rapid, precise as well as sensitive determination of components or contaminants of foods is very important. Therefore, developing the new electrochemical (bio)sensors in food analysis is one of the key and effervescent research fields. In this review, firstly, we presented the properties and synthesis strategies of MNMs. Then, we summarized some of the recently developed MNMs-based electrochemical (bio)sensors for food analysis including detecting the antioxidants, synthetic food colorants, pesticides, heavy metal ions, antibiotics and other analytes (bisphenol A, nitrite and aflatoxins) from 2010 to 2020. Finally, the present review described advantages, challenges as well as future directions in this field.

Detection of Six β-Agonists by Three Multiresidue Immunosensors Based on an Anti-bovine Serum Albumin-Ractopamine-Clenbuterol-Salbutamol Antibody

According to an indirect competitive immunoassay, six β-agonists (clenbuterol (CL), salbutamol (SAL), ractopamine (RAC), terbutaline (TER), mabuterol (MAB), and tulobuterol (TUL)) were detected by three novel multiresidue immunosensors on the basis of the successful preparation of bovine serum albumin (BSA)-RAC-CL-SAL multideterminant antigen and anti-BSA-RAC-CL-SAL antibody. A new strategy was reported to detect six β-agonists by combining nanotechnology, electrochemical detection, and specific immune technology. At the same concentration, the amperometric response for detection of six β-agonists was in a sequence of GCE/GNP/SAL > GCE/GNP/RAC > GCE/GNP/CL. Detection limits of six β-agonists show that the multiresidue detection performance of the GCE/GNP/RAC immunosensor is better than those of GCE/GNP/SAL and GCE/GNP/CL immunosensors. Three immunosensors manifest superior properties with a wide linear range, low detection limit, excellent reproducibility, and stability. The proposed GCE/GNP/RAC immunosensor displays high accuracy and can be effectively used for real sample detection.