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Organic acids are important components in determining fruit taste, and it is necessary to develop rapid analysis methods for them. A simple and effective method based on laser-engraved free-standing terahertz (THz) metamaterials has been developed for rapid analysis of fruit acids. Compared with traditional fabrication methods for THz metamaterials, laser direct writing technology was employed for fabricating the Cu-foil-based THz devices in this research, which is time-saving, cost-effective, and high-throughput. To realize effective fabrication of metamaterials, proper fabrication parameters were selected according to morphology and spectral characterization. Numerical analysis was performed to reveal the fundamental mechanism of THz sensing based on metamaterials. Furthermore, experimental results indicate that fruit acid with a concentration of 0.1 mg L−1 can be successfully distinguished, which is quick and simple compared with traditional acid–base titration. The proposed strategy demonstrates great potential for rapid in situ analysis of flavor components in food products.

Performing sensitive and selective detection in a mixture is challenging for terahertz (THz) sensors. In light of this, many methods have been developed to detect molecules in complex samples using THz technology. Here we demonstrate a defect-rich monolayer graphene-coated metamaterial operating in the THz regime for pesticide sensing in a mixture through strong local interactions between graphene and external molecules. The monolayer graphene induces a 50% change in the resonant peak excited by the metamaterial absorber that could be easily distinguished by THz imaging. We experimentally show that the Fermi level of the graphene can be tuned by the addition of molecules, which agrees well with our simulation results. Taking chlorpyrifos methyl in the lixivium of rice as a sample, we further show the molecular sensing potential of this device, regardless of whether the target is in a mixture or not.

Terahertz (THz) electromagnetic waves strongly interact with complex molecules, making THz spectroscopy a promising tool for high-sensitivity molecular detection, especially for biomedical applications. Metamaterials are typically used for enhancing THz-molecule interactions to achieve higher sensitivities. However, a primary challenge in THz molecular sensing based on metallic metamaterials is the limited tunability of optical constants of metals. Here, we present an ultrahigh-sensitivity molecular sensor based on carbon nanotube (CNT) THz metamaterials. The sensor, consisting of a CNT cut-wire array on a Si substrate prepared by a novel two-step method, exhibits a reflectance resonance whose frequency strongly varies with the substrate composition, geometries of periodic arrays, and analyte composition. We used this sensor to detect glucose, lactose, and chlorpyrifos-methyl molecules, achieving limit-of-detection values of 30, 40, and 10 ng/mL (S/N = 3), respectively, higher than that of metallic metamaterials by 2 orders of magnitude. We attribute this ultrahigh sensitivity to the high conductivity of CNTs and the efficient adsorption of the target analyte by CNTs through van der Waals forces and π-π stacking. These easy-to-fabricate CNT-based THz metamaterials pave the way for versatile and reliable ultrahigh-sensitivity THz molecular detection.

The accurate and rapid detection of foreign materials in food products is essential for ensuring food safety and quality. Terahertz (THz) imaging is an emerging technology for non-destructive detection in food industrial with the advantages of non-ionization and spectroscopic fingerprinting. In this study, we have attempted to explore the effectiveness of THz spectroscopic imaging for foreign material detection in food with complicated compositions. The feasibility of locating contaminations in sausages were demonstrated through typical spectral comparison, spectral classification assisted by principal component analysis and discriminant analysis methods, and one-dimensional scanning spectral analysis. Our imaging results indicated THz spectroscopic imaging has the ability to locate metal contaminations in sausages no matter what part of sausages is as the food matrix. This study will provide new knowledge about foreign material detection in food with complicated compositions and a basis for parameters selection of continuous-wave THz imaging for contamination detection in this case.

Terahertz (THz) technology is now drawing increasing attention around the world; it has been considered as an efficient non-destructive, non-contact and label-free optical method for biological detection. In this field, nanomaterials and nanostructures have been constantly advancing the development of THz technology. Here, we proposed some latest applications of nanotechnology to improve THz biological detection capability for providing progressive THz systems, thus enabling outstanding detection performance utilizing THz spectroscopy and imaging; these will encourage broader interest in various fields. The uniqueness, limitations, and future prospects of THz biological applications based on nanomaterials and nanostructures will also be reviewed in light of recent developments.

There is an increasing recognition that terahertz (THz) spectroscopy can be used for high-sensitivity molecular sensing. Therefore, in recent years, much work has been devoted to developing flexible, compact, and high-sensitivity THz sensors. However, most designs employ metamaterials, which require complicated, and often expensive, fabrication procedures. Also, the metamaterial structures create a gap between the sensor surface and the target surface, which decreases the effective contact area between them, resulting in reduced sensing performance. Here, we fabricated a metamaterial-free graphene-based THz sensor with user-designed patterns for sensing at bio-interfaces. External molecules can strongly interact with π electrons in graphene, which moves the Fermi level and changes the amount of THz absorption. We used this sensor to successfully detect chlorpyrifos methyl with a limit of detection at 0.13 mg/L. We also detected pesticide molecules of a concentration of 0.60 mg/L on the surface of an apple, revealing the flexibility of this sensor. The flexible graphene THz sensor showed high sensing stability and robustness over 1000 cycles of bending. These results show that our graphene-based thin-film sensors are easy to fabricate, flexible, versatile, and suited for a wide range of sensing applications.

Metasurface assisted terahertz (THz) real-time and label-free biosensors have attracted intense attention. However, it is still challenging for specific detection of highly absorptive liquid samples with high sensitivity in the THz range. Here, we incorporated graphene with THz metasurface into a microfluidic cell for sensitive biosensing. The proposed THz graphene-metasurface microfluidic platform can effectively reduce the volume of the sample solution and boost the interaction between biomolecules and THz waves, thus enhancing the sensitivity. As a proof of concept, comparative experiments using other three kinds of microfluidic cells (pure microfluidic cell, metasurface-based microfluidic cell and graphene-based microfluidic cell) were conducted to explore and verify the sensing mechanism, which evidences the high sensitivity of delicate sensing based on the hybrid graphene-metasurface THz microfluidic device. Furthermore, to perform biosensing applications on that basis, specific aptamers were modified on the graphene-metasurface, enabling DNA sequences of foodborne pathogen Escherichia coli O157:H7 to be recognized. Based on the THz microfluidic biosensor, 100 nM DNA short sequences can be successfully detected. The sensing results of antibiotics and DNA based on the graphene-metasurface microfluidic biosensor confirm the superiority of the proposed design and considerable promise in THz biosensing. The novel sensing platform provides the merits of enabling highly sensitive, label-free, low-cost, easy to use, reusable, and real-time biosensing, which opens an exciting prospect for nanomaterial-metasurface hybrid structure assisted THz label-free biosensing in liquid environment.

Summary To expand utilisation of meat in various products, the characterisation and functionalities of water-soluble myofibrillar proteins (WSMP) induced by high-pressure homogenisation (HPH) were determined by comparison with those of soy protein isolate (SPI) and whey protein isolate (WPI). WSMP had high contents of protein (87.40%), which was mainly composed of myosin, actin and tropomyosin. The essential amino acids of WSMP achieved the FAO/WHO/UNO (2007) standards for preschool children, and the contents of lysine and sulphur-containing amino acids of WSMP were higher than those of SPI, making it desirable for children formulations. WSMP showed higher surface hydrophobicity while its water solubility was similar to that of SPI, but lower than that of WPI. WSMP demonstrated superior water/oil absorption capacities and emulsifying properties. The fibrous structure and high hydrophobic activity characteristics of WSMP were able to stabilise oil droplets with submicron droplet size, consequently responsible for its excellent emulsifying properties.

Terahertz (THz) spectroscopy has emerged as an attractive technique for qualitative and quantitative detection. Analysis of these chemicals in the THz range under various temperatures can yield detailed information on molecular vibrational modes, which is of utmost importance for effective detection. Here we report the use of THz time-domain spectroscopy (THz-TDS) to measure tetracyclines hydrochloride (TCH) and its degradation products including epitetracycline hydrochloride (ETCH), anhydrotetracycline hydrochloride (ATCH), and epianhydrotetracycline hydrochloride (EATCH) over the temperature range of 4.5–300 K for the first time. The results showed that these four tetracyclines exhibited numerous distinct spectral features in frequency-dependent absorption spectra, which demonstrated the qualitative capacity of THz-TDS. Through density functional theory (DFT) calculations and analysis of temperature-dependent absorption spectra, the origin of the observed terahertz absorption peaks of these four tetracyclines were well interpreted. This study could lay the foundation for high-performance analysis of biological and chemical molecules by THz spectroscopy, which is essential for sensing application.

In the study, osmotically dehydrated cherry tomatoes were partially dried to water activity between 0.746 and 0.868, vacuum-packed and stored at 4-30 °C for 60 days. Adaptive neuro-fuzzy inference system (ANFIS) was utilized to predict the physicochemical and microbiological parameters of these partially dried cherry tomatoes during storage. Satisfactory accuracies were obtained when ANFIS was used to predict the lycopene and total phenolic contents, color and microbial contamination. The coefficients of determination for all the ANFIS models were higher than 0.86 and showed better performance for prediction compared with models developed by response surface methodology. Through ANFIS modeling, the effects of storage conditions on the properties of partially dried cherry tomatoes were visualized. Generally, contents of lycopene and total phenolics decreased with the increase in water activity, temperature and storage time, while aerobic plate count and number of yeasts and molds increased at high water activities and temperatures. Overall, ANFIS approach can be used as an effective tool to study the quality decrease and microbial pollution of partially dried cherry tomatoes during storage, as well as identify the suitable preservation conditions.

Summary The effects of 5 mm l-histidine (l-His) on water-binding capacity, gel strength, thermal gelling properties of chicken breast myofibrillar proteins (MPs) in 1 mm NaCl or 0.6 m NaCl solutions (pH 7.0) were investigated. l-His could significantly increase the solubility and thermal gelling ability of MPs in 1 mm NaCl. l-His at 1 mm NaCl shortened the water relaxation time and decreased the water mobility of MPs gel. l-His promoted the formation of MPs gel structure with small pores and thin strands at 1 mm NaCl. These resulted in the enhanced water retention and weak gel strength of MPs in low ionic strength solution. The water-binding capacity of MPs gels formed in 1 mm NaCl containing 5 mm l-His was equivalent to that with 0.6 m NaCl. The information could offer certain theoretical foundation to apply l-His as sodium salt substitute for developing low-salt meat gelling product with high yield.

Terahertz (THz) technique, with plenty attractive properties such as its prominent detecting ability, non-destruction and non-ionization, has been getting increased attention. THz modulator, enabling efficient manipulation, is crucial for THz devices and sensing applications. However, its practical implementation still remains a challenge because of the small modulation depth, slow modulation rate and difficult operation way. Nanomaterials have been constantly creating possibilities for the advancement of THz technology. Considering their excellent optical and electrical characteristics, gold nanorods (GNRs) are integrated with silicon-based materials to improve the performance for THz modulation, so as to promote the possibility of THz sensing in aqueous environment. In this paper, the modulation ability of THz wave based on bare silicon with/without dried GNR film, liquid cell with GNR solutions, and silicon channel with GNR solutions is systematically investigated. According to the results, a six-time larger modulation depth can be realized with the plasmonic effect of GNRs through infrared laser irradiation, which is employed to increase the protein detection sensitivity up to ppm level in water state. It is anticipated that integrating nanomaterials with THz functional devices is meaningful to improve the performance of THz technology, which could facilitate its wide applications in various fields.

Food-derived biomaterials have attracted increasing attention due to their renewability, excellent biocompatible and biodegradable properties, tunable solubility, and multi-active binding sites for introducing novel functionalities. As the three major food biomaterials, polysaccharides, lipids, and proteins from diverse natural sources are environmentally friendly and possess potential functions for emerging applications. Food-derived nanomaterials can be obtained from one or more types of food biomaterials or the combination of various biopolymers by many manufacturing methods. Applications of food-derived nanomaterials or bionanocomposites to biosensing are current research trends owing to their new optical, catalytic, and structural functionalities. This review provides a broad overview of the functional properties of food-derived nanomaterials, the preparation techniques for creating food-derived nanomaterials, and their potential applications for biosensing. Moreover, the major challenges and future perspectives of this fast-growing field are also highlighted.

Terahertz (THz) spectroscopy has the advantages of non-ionization and spectroscopic fingerprint, which can be used for biological and chemical compound analysis. However, because of the strong absorption of water in the THz region, it is still a challenge for THz waves to realize aqueous solution detection. In this study, taking a doxycycline hydrochloride (DCH) aqueous solution as the target, we proposed a THz metallic mesh device (MMD) based reflection platform for the first time for sensing. The angle characteristics of the THz MMD was investigated through numerical simulations and experimental measurements to get an optimized configuration for the platform. When the projection of THz electric field polarization onto the MMD plane gets parallel to latitudinal direction of the MMD apertures, a strong resonant surface mode can be achieved, and our proposed platform can be successfully used to detect the DCH solution with a concentration as low as 1 mg L−1. The sensing mechanism of our platform was also explored by analyzing the influences of the immersion depth into the MMD holes and the extinction coefficient of droplets on the reflection spectra. Our work presents a rapid, low-cost, and practical platform for antibiotic solution sensing using THz radiation, which opens new avenues for the microanalysis of chemicals or biomolecules in strongly absorptive solutions in the THz region.

The aim of the present study was to investigate the association of TNF-α-308 and TNF-α-238 gene polymorphisms with the risk of bone-joint and spinal tuberculosis (TB) by meta-analysis. By searching PubMed, Web of Science, Wanfang databases, CNKI, Medline, and Cochrane Library, the published articles about studies of the association of the TNF-α-308, TNF-α-238 gene polymorphisms with risk of bone-joint and spinal tuberculosis were collected by two reviewers. Begg’s and Egger’s tests were performed to assess publication bias. Stata 12.0 software was used for data analysis. The symmetry of the funnel plot indicated no significant publication bias in the Begg’s test (A: P=1.00, B: P=0.764), and the results of the Egger’s test showed no evidence of publication bias (A: P=0.954, B: P=0.626). Seven studies assessed the relationship between TNF-α-308 gene polymorphisms and risk of bone-joint and spinal tuberculosis risk. The heterogeneity (I2) of GG vs. AA or AG was 0% and there was no heterogeneity (χ2 = 0.06 and P=0.944) in a fixed-effects model. There was also a lack of association between TNF-α-308 polymorphism and bone-joint and spinal tuberculosis risk under the recessive model. The remaining models of the TNF-α-308 genotype and further studies of TNF-α-238 did not show a noteworthy association. Overall, there was no significant association between TNF-α-308, TNF-α-238 gene polymorphisms and bone-joint and spinal tuberculosis risk. Our study suggests that tumor necrosis factor α (TNF-α) gene polymorphisms may not contribute to bone-joint and spinal tuberculosis based on the current evidence.

The capability to design, fabricate, and optimize metamaterials based on various structures and material platforms has been crucial for the rapid development of modern terahertz (THz) technology. While the detailed structures of artificial unit cells within a metamaterial is certainly worth investigating, there has been increasing demand to integrate novel metamaterials with a traditional functional photonic device to form a hybrid device, whose performance is so significantly improved as to be promising for real-world applications. In this study, we proposed, for the first time, a THz parallel-plate resonator based on metallic mesh devices (MMDs) for chemical sensing applications. We studied the influences of various structural parameters through simulations, fabricated MMD-based resonator devices, and fully characterized the device performance through THz spectroscopy experiments. Furthermore, we experimentally demonstrated that our device can detect a doxycycline hydrochloride aqueous solution whose concentrations is as low as 1 mg L−1 through resonance frequency shifts, evidencing the device sensitivity capable of delicate chemical sensing tasks. Our work presents a practical and low cost architecture for chemical sensing using THz radiation, which opens new avenues for numerous useful THz devices based on metamaterials.

To expand utilization of meat in various products, the structural, physicochemical and functional changes of water soluble myofibrillar protein powder (WSMP-P) were investigated as affected by high-pressure homogenization (HPH) intensities (0-20,000psi). HPH modified the structure of WSMP-P by random dissociation (myofibril and myosin polymer dissociation), partial unfolding and rearrangement (actin trimer formation), producing an amorphous protein structure with high thermal stability. α-Helix and β-turn conversion to β-sheet structures occurred at pressures above 15,000psi, suggesting an increase in myosin conformation flexibility with minor aggregation. Moreover, HPH was able to improve the water solubility and emulsifying properties of WSMP-P. This might be resulted from its unfolded flexible structure with submicron size and high surface net charge in aqueous suspensions induced by HPH. The findings regarding the improved functionality evidence potential of applying WSMP-P as protein supplements in formulated food or beverage at low ionic conditions.