•Favorable properties of MOF used in synthesizing biocomposites are introduced.•Combination strategies between the biomolecules and MOFs are presented.•Sensing applications of various MOF ...biocomposites are summarized.
Metal-organic frameworks (MOFs) are a novel class of highly porous materials, coordinated by the self-assembly of inorganic metal-containing nodes and organic ligands. By virtue of the advantages of MOFs, like tunable pores, diverse functional sites, and large surface area, they have become a promising candidate to immobilize various biomolecules. On the other hand, the introduction of biomolecules including enzymes, nucleic acids, antibodies, peptides, and phages on the surface or in the cavity of MOFs enables the sensing application with enhanced sensitivity, specificity, and broad range of targets. The integration of biomolecules with MOFs generates MOF biocomposites with synergistic properties and functions, attracting the broad interests in the field of sensing applications. This review presents the recent progress on the rational synthesis and sensing applications of MOF biocomposites. First of all, we introduce the favorable properties of MOFs used in the preparation of biocomposites for sensing applications. Then, the synthesis strategies between the biomolecules and MOFs are summarized. Thirdly, MOF biocomposite-based sensors are comprehensively reviewed according to the types of the biomolecules. Finally, some significant prospects and further challenges in this field are discussed.
Antibiotics are able to be accumulated in human body by food chain and may induce severe influence to human health and safety. Hence, the development of sensitive and simple methods for rapid ...evaluation of antibiotic levels is highly desirable. Nanomaterials with excellent electronic, optical, mechanical, and thermal properties have been recognized as one of the most promising materials for opening new gates in the development of next-generation biosensors. This review highlights the current advances in the nanomaterial-based biosensors for antibiotics detection. Different kinds of nanomaterials including carbon nanomaterials, metal nanomaterials, magnetic nanoparticles, up-conversion nanoparticles, and quantum dots have been applied to the construction of biosensors with two main signal-transducing mechanisms, i.e. optical and electrochemical. Furthermore, the current challenges and future prospects in this field are also included to provide an overview for future research directions.
•An overview about current advances in nanomaterial-based biosensors for antibiotics detection was present.•Several nanomaterials that widely applied to the fabrication of biosensors were discussed in details.•Two main signal transducing mechanisms of biosensors including electrochemical and optical were discussed.•Some challenges and futures about the development of nanomaterial-based antibiotic biosensors were summarized.
Continuous transformation and development of new detection tools for bacteria has converted the laborious scientific work into smart apparatus in recent years. The journey had begun with the ...culture-based plate enumeration, and now it has evolved into several culture-independent techniques. Polymerase chain reaction (PCR) is on the top of the list that is now a routinely used biological approach to detect bacterial cells. Instrumental techniques are also helpful in this regard, as they are more sensitive for detection of various microbes.
In this review, we described new trends and their practical application in the fields of detection microbiology and food technology. This study provides a brief overview of conventional and modern detection techniques which includes nucleic-acid sequence based techniques to non-destructive imaging techniques.
Besides the availability of antibiotics and clinical treatments, bacterial infections significantly increase the mortality rate. It is necessary to detect apparent infectious agents beforehand. Therefore, the detection methods for microorganisms should be more rapid, smart and reliable in response to the need. Conventional detection techniques are slow and time-consuming but more accurate and reliable than the modern detection techniques. By combing the mentioned techniques, scientists can achieve better results.
•Microbial detection techniques are frequently evolving from conventional methods.•Advanced, label-free detection of living bacterial cell in solution is possible now.•Now sensitive and noninvasive detection methods are gaining much attraction.•Combination of given techniques results in the creation of robust methods in future.
Nitrite is widely found in the natural environment and human life, but the abuse and potential toxicity of nitrite poses a great threat to human health. Therefore, it is necessary to develop ...effective, robust, and reliable methods for nitrite detection. Carbon nanomaterials have shown their great potential in the development of high-performance electrochemical sensors in view of their numerous fascinating properties. Carbon nanomaterial-enabled electrochemical sensors have been regarded as one of the most promising detection tools for nitrite due to their high sensitivity, simplicity of operation, and excellent selectivity. In this review, we introduce the state-of-art of carbon nanomaterial-enabled electrochemical sensors in nitrite detection in the past years (2014–2018). The properties and advantages of carbon nanotubes, graphene, graphene oxide, carbon nanofibers, carbon nanodots, nanodiamonds, and nanoporous carbon in the development of nitrite sensors are discussed in details. Furthermore, the challenges and prospects for the application of carbon nanomaterial-enabled electrochemical sensors for nitrite analysis are also included.
•Recent advances and new trends in carbon nanomaterial-enabled electrochemical nitrite sensors.•Advantages of carbon nanotubes, graphene, carbon nanofibers, and carbon nanodots are summarized.•Current challenges and future perspectives of nitrite sensors are discussed.
Interfacing DNA with two-dimensional (2D) materials has been intensely researched for various analytical and biomedical applications. Most of these studies have been performed on graphene oxide (GO) ...and two metal dichalcogenides, molybdenum disulfide (MoS2) and tungsten disulfide (WS2); all of them can all adsorb single-stranded DNA. However, they use different surface forces for adsorption based on their chemical structures. In this work, fluorescently labeled DNA oligonucleotides were used and their adsorption capacities and kinetics were studied as a function of ionic strength, DNA length, and sequence. Desorption of DNA from these surfaces was also measured. DNA is more easily desorbed from GO by various denaturing agents, whereas surfactants yield more desorption from MoS2 and WS2. Our results are consistent with the fact that DNA can be adsorbed by GO via π–π stacking and hydrogen bonding, and MoS2 and WS2 mainly use van der Waals force for adsorption. Finally, fluorescent DNA probes were adsorbed by these 2D materials for detecting complementary DNA. For this assay, GO gave the highest sensitivity, whereas they all showed a similar detection limit. This study has enhanced our fundamental understanding of DNA adsorption by two important types of 2D materials and is useful for further rational optimization of their analytical and biomedical applications.
In recent years, due to the increasing consciousness of food safety and human health, much progress has been made in developing rapid and nondestructive techniques for the evaluation of food hazards, ...food authentication, and traceability. Near infrared (NIR) spectroscopy and imaging techniques have gained wide acceptance in many fields because of their advantages over other analytical techniques. Following a brief introduction of NIR spectroscopy and imaging basics, this review mainly focuses on recent NIR spectroscopy and imaging applications for food safety evaluation, including (1) chemical hazards detection; (2) microbiological hazards detection; (3) physical hazards detection; (4) new technology-induced food safety concerns; and (5) food traceability. The review shows NIR spectroscopy and imaging to be effective tools that will play indispensable roles for food safety evaluation. In addition, on-line/real-time applications of these techniques promise to be a huge growth field in the near future.
Surface-enhanced Raman scattering (SERS) is capable of detecting a single molecule with high specificity and has become a promising technique for rapid chemical analysis of agricultural products and ...foods. With a deeper understanding of the SERS effect and advances in nanofabrication technology, SERS is now on the edge of going out of the laboratory and becoming a sophisticated analytical tool to fulfill various real-world tasks. This review focuses on the challenges that SERS has met in this progress, such as how to obtain a reliable SERS signal, improve the sensitivity and specificity in a complex sample matrix, develop simple and user-friendly practical sensing approach, reduce the running cost, etc. This review highlights the new thoughts on design and nanofabrication of SERS-active substrates for solving these challenges and introduces the recent advances of SERS applications in this area. We hope that our discussion will encourage more researches to address these challenges and eventually help to bring SERS technology out of the laboratory.
The rapidly growing demand for humidity sensing in various applications such as noninvasive epidermal sensing, water status tracking of plants, and environmental monitoring has triggered the ...development of high-performance humidity sensors. In particular, timely communication with plants to understand their physiological status may facilitate preventing negative influence of environmental stress and enhancing agricultural output. In addition, precise humidity sensing at bio-interface requires the sensor to be both flexible and stable. However, challenges still exist for the realization of efficient and large-scale production of flexible humidity sensors for bio-interface applications. Here, a convenient, effective, and robust method for massive production of flexible and wearable humidity sensor is proposed, using laser direct writing technology to produce laser-induced graphene interdigital electrode (LIG-IDE). Compared to previous methods, this strategy abandons the complicated and costly procedures for traditional IDE preparation. Using graphene oxide (GO) as the humidity-sensitive material, a flexible capacitive-type GO-based humidity sensor with low hysteresis, high sensitivity (3215.25 pF/% RH), and long-term stability (variation less than ± 1%) is obtained. These superior properties enable the sensor with multifunctional applications such as noncontact humidity sensing and human breath monitoring. In addition, this flexible humidity sensor can be directly attached onto the plant leaves for real-time and long-term tracking transpiration from the stomata, without causing any damage to plants, making it a promising candidate for next-generation electronics for intelligent agriculture.
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•A convenient, effective, and robust method for massive production of flexible and wearable humidity sensor is developed based on laser-induced technology.•A flexible capacitive-type GO-based humidity sensor with low hysteresis, high sensitivity, and long-term stability is obtained.•The fabricated flexible and wearable sensor can be used for noncontact humidity sensing and human breath monitoring.•Real-time and long-term tracking of plant transpiration at bio-interface in realized without causing any physical damage to plants.
The development of chemometrics aims to provide an effective analysis approach for data generated by advanced analytical instruments. The success of existing analytical approaches in spectral ...analysis still relies on preprocessing and feature selection techniques to remove signal artifacts based on prior experiences. Data-driven deep learning analysis has been developed and successfully applied in many domains in the last few years. How to integrate deep learning with spectral analysis received increased attention for chemometrics. Approximately 20 recently published studies demonstrate that deep neural networks can learn critical patterns from raw spectra, which significantly reduces the demand for feature engineering. The composition of multiple processing layers improves the fitting and feature extraction capability and makes them applicable to various analytical tasks. This advance offers a new solution for chemometrics toward resolving challenges related to spectral data with rapidly increased sample numbers from various sources. We further provide a practical guide to the development of a deep convolutional neural network-based analytical workflow. The design of the network structure, tuning the hyperparameters in the training process, and repeatability of results is mainly discussed. Future studies are needed on interpretability and repeatability of the deep learning approach in spectral analysis.
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•Summarize the challenges of existing chemometric methods in spectral analysis.•Review the research progress on deep learning-based spectral analysis.•Provide a practical guide on deep learning approach in spectral analysis.
► A disposable electrode made from graphene-based screen-printing ink was proposed. ► Large potential window, low background current and fast electron transfer kinetics. ► Three well-defined and ...fully resolved peaks for oxidation of three species. ► High sensitivity, selectivity, stability, reproducibility and easy fabrication.
A disposable and sensitive screen-printed electrode using an ink containing graphene was developed. This electrode combined the advantages of graphene and the disposable characteristic of electrode, which possessed wide potential window, low background current and fast electron transfer kinetics. Compared with the electrodes made from other inks, screen-printed graphene electrode (SPGNE) showed excellent electrocatalytic activity for the oxidation of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Three well-defined sharp and fully resolved anodic peaks were found at the developed electrode. Differential pulse voltammetry was used to simultaneous determination of AA, DA, and UA in their ternary mixture. In the co-existence system of these three species, the linear response ranges for the determination of AA, DA, and UA were 4.0–4500μM, 0.5–2000μM, and 0.8–2500μM, respectively. The detection limits (S/N=3) were found to be 0.95μM, 0.12μM, and 0.20μM for the determination of AA, DA, and UA, respectively. Furthermore, the SPGNE displayed high reproducibility and stability for these species determination. The feasibility of the developed electrode for real sample analysis was investigated. Results showed that the SPGNE could be used as a sensitive and selective sensor for simultaneous determination of AA, DA, and UA in biological samples, which may provide a promising alternative in routine sensing applications.
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