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.
2-Thienyl and 2,6-bisthienyl BODIPY derivatives (BS-SS and BS-DS) were prepared that show intense absorption (ε = 65000 M–1 cm–1 at 507 nm) and a large Stokes shift (96 nm) vs the small Stokes shift ...of typical BODIPY (<15 nm). Control compounds with a thienyl unit at the 8-position or phenyl substituents at the 2,6-positions were prepared (BS-1 and 9). BS-1 shows absorption/emission in the blue-shifted range and a small Stokes shift (12 nm). Compound 9 shows absorption in the red-shifted range, but the Stokes shift (<30 nm) is much smaller than that for BS-SS and BS-DS. DFT calculations propose the large Stokes shifts of BS-SS and BS-DS are due to the remarkable geometry relaxation upon photoexcitation and its substantial effect on the energy levels of molecular orbitals. For the dyes with small Stokes shifts, much smaller geometry relaxations were found. The fluorophores were used for fluorescent thiol probes, with 2,4-dinitrobenzenesulfonyl (DNBS) as the fluorescence switch. Both fluorescence OFF–ON and unprecedented ON–OFF transduction were observed, which are attributed to the different photoinduced intramolecular electron-transfer (PET) profile. All the photophysics were rationalized by DFT calculations based on the concept of “electronic states” instead of the very often used approximation of “molecular orbitals”.
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.
•A novel microfluidic platform integrating graphene with metasurface is reported.•Sensitive terahertz molecular detection in liquid environment is realized.•DNA sequences of foodborne pathogen can be recognized with high selectivity.•The biosensing capability can be restored through a simple regeneration process.•The hybrid metasurface-graphene structure can improve the sensitivity.
•Near infrared spectroscopy was used for evaluating soluble solids content (SSC) of citrus fruits.•Genetic algorithm and successive projection algorithm (GA–SPA) was proposed to select effective ...wavelengths.•GA–SPA multiple linear regression model could be used to detect the SSC of citrus fruit online.
Several variable selection methods were investigated to select effective wavelengths (EWs) for determination of soluble solids content (SSC) of citrus fruits using NIR spectroscopy. The EWs selected by successive projection algorithm (SPA), stepwise multiple linear regression (SMLR), regression coefficient analysis (RCA) and x-loading weights analysis (x-LWA) were directly used for multiple linear regression (MLR). The variables selected by genetic algorithm (GA), uninformative variable elimination (UVE) and Monte Carlo UVE (MC-UVE) were used for partial least squares (PLS) regression. Finally the variables selected by GA, UVE and MC-UVE were further selected by SPA, SMLR, RCA and x-LWA, and corresponding MLR models were established. Results showed that the GA–SPA–MLR model yielded promising results, with rp and RMSEP being 0.893 and 0.436°Brix. The GA–SPA method was suggested to select EWs for MLR calibrations. Corresponding MLR function was provided and was supposed to be valuable for online SSC determination of citrus fruits.
•Optimal combination of spectrum transformation and model were selected for different heavy metal.•Results showed that the accuracy of RF was higher than that of SVM and PLS.•This study can provide ...technical support for the nondestructive monitoring of soil heavy metal content.
Hyperspectral remote sensing technology has considerable research value in monitoring and evaluating soil heavy metal pollution. In this study, the Three-River Source Region was taken as the study area. The occurrence relationship of six heavy metals in soil, such as Mn, Cu, Zn, Pb, Cr, Ni, with soil organic matter, clay minerals, and iron-manganese oxides, was studied through the determination and analysis of soil samples and the collection of soil reflectance spectrum. Spectral transformation was carried out by first derivative, second derivative, inverse-log, continuum removal and multiple scattering correction of the spectrum. The correlation between soil heavy metal content and soil spectrum was analyzed to select the characteristic band, and partial least squares (PLS) method, support vector machine (SVM) method and random forest (RF) model were used to build inversion model based on characteristic band. Then the best combination of spectral transformation and inversion model were explored. The results showed that Pb contents were the twice of the background in Qinghai province. The combination spectrum processing method can improve the correlation between spectrum and heavy metals. The location and quantity of characteristic bands of six heavy metals are different. The accuracy of RF was significantly better than that of SVM and PLS for all six heavy metal (i.e. pb: R2RF = 0.83, R2SVM = 0.62, R2PLS = 0.18), and the model effective of soil properties in non-polluted sites were reliable (i.e. clay: R2RF = 0.93, R2SVM = 0.87, R2PLS = 0.74). This study can provide technical support for the larger-scale monitoring of soil heavy metal content and heavy metal pollution assessment.
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.
Sensitive and selective detection in a mixture using terahertz devices.
Cu-SSZ-13 samples prepared by a novel one-pot synthesis method achieved excellent NH3-SCR performance and high N2 selectivity from 150 to 550 °C after ion exchange treatments. The selected ...Cu3.8-SSZ-13 catalyst was highly resistant to large space velocity (800 000 h(-1)) and also maintained high NOx conversion in the presence of CO2, H2O, and C3H6 in the simulated diesel exhaust. Isolated Cu(2+) ions located in three different sites were responsible for its excellent NH3-SCR activity. Primary results suggest that the one-pot synthesized Cu-SSZ-13 catalyst is a promising candidate as an NH3-SCR catalyst for the NOx abatement from diesel vehicles.
We have detected trace amounts of molecules of antibiotics (kanamycin sulfate) dispersed on metasurfaces with terahertz (THz) spectroscopy. Utilizing the extraordinary optical transmission resonance ...of an array of square-shaped slits on a silicon substrate at ~0.3 THz, we were able to monitor varying concentrations of kanamycin sulfate as low as ~100 picogram/L. In contrast, the lowest detectable concentration of kanamycin sulfate on silicon without any metallic structure was ~1 gram/L. This dramatic ~10(10) times enhancement of sensitivity is due to the near-field enhancement of THz electric fields by the metamaterial structure. This result thus demonstrates the power and usefulness of metamaterial-assisted THz spectroscopy in trace molecular detection for biological and chemical sensing as well as for food product quality and safety inspection and control.
Accumulating evidence has indicated that oxidative stress (OS) is associated with the development of hepatocellular carcinoma (HCC). However, the mechanisms remain largely unknown. Normally, OS ...occurs when the body receives any danger signal—from either an internal or external source—and further induces DNA oxidative damage and abnormal protein expression, placing the body into a state of vulnerability to the development of various diseases such as cancer. There are many factors involved in liver carcinogenesis, including hepatitis B virus (HBV) and hepatitis C virus (HCV) infection, alcohol abuse, and nonalcoholic fatty liver disease (NAFLD). The relationship between OS and HCC has recently been attracting increasing attention. Therefore, elucidation of the impact of OS on the development of liver carcinogenesis is very important for the prevention and treatment of liver cancer. This review focuses mainly on the relationship between OS and the development of HCC from the perspective of cellular and molecular mechanisms and the etiology and therapeutic targets of HCC.
We report the use of terahertz time-domain spectroscopy (THz-TDS) to detect tetracyclines hydrochloride (TCsH) in infant milk powder for the first time. Four kinds of TCsH exhibited their unique ...spectral features in the region of 0.3–1.8 THz. The main spectral features of these TCsH were still detectable when mixed with infant milk powder with concentrations at 1%–50%, even in the ternary mixtures. The results from chemometrics analysis showed that qualitative and quantitative detection of TCsH in infant milk powder could be successfully achieved. The residual predictive deviation (RPD) values of all these TCsH models were all higher than 2, indicating these models were considered good and could be used in screening purposes. The RPD values of TCH, DTCH, and CTCH models were higher than 3, which were considered excellent for prediction purposes. These preliminary results indicated that THz-TDS combined with chemometrics analysis was suitable for detecting the presence of TCsH residues in a food matrix.
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