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Water pollution is one of the most important problems for human beings. BTEX (Benzene, Toluene, Ethylbenzene and Xylenes) have vast application in industry and their carcinogenic effect on human body has approved. Hence these part of water pollutants (water-soluble aromatic components) have more importance. Monitoring systems that can detect presence of BTEX in water supplies are much expensive such as gas chromatography so we need simple systems to reduce the number of samples that we are suspected to them for more analysis by much more expensive systems. Bioreporters are a subgroup of biosensors which are using for sensing and monitoring some signals or reagents. A bioreporter is an organism like a bacteria or a plant that is genetically manipulated to have a promoter which is sensitive to a chemical or physical signal. Activation of the promoter In presense of the signal leads to product of the reporter gene which can be sensed or calculated by our laboratory supplies. A green fluorescent protein gene has been used as a reporter gene downstream of PtbuA1 as a BTEX sensitive promoter in Escherichia coli and its response to BTEX has been investigated in this study. Our results show our bioreporter can sense Toluene.The optimum time and temperature for the bioreporter is also defined.

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Aims: The accumulation of free radicals in the body leads to damages to cellular biopolymers through oxidative stress. Due to the increasing proliferation of heavy metals in soil and water environments, finding efficient methods for diagnostic detection and measurement of heavy metals in contaminated environments is very important. Cell-based biosensors can produce a measurable signal in response to specific chemical or physical agent in their environment. In this study, stable hepatoma Huh7 ARE-reporter cell line was developed containing luciferase gene with the aim of monitoring lead toxicity. This biosensor is reported to be able to detect lead by expressed signal which is measurable. The luciferase assay and Real time-PCR were performed.
Materials and Methods: In this experimental research, the Huh7-1x-ARE-luc was stably transferred in to the Huh7 cells and transfected cells were selected. After 5 passages, stable clones were isolated to confirm plasmid entrance. Luciferase activity of the Huh7-1x-ARE-luc cell line was performed with 0-80μM lead concentration to induce oxidative stress response. Cell viability was assessed by MTT.  With Real time PCR, AREKEAP1 pathway gene expression were detected. Statistical analysis was performed by ΔCt method, using graphpad prism 6 software.
Findings: The gene expression of the reporter gene increased with increasing oxidative stress. Reducing the expression of the reporter gene was observed after 30 μM. 35 μM lead inhibited 50% cell metabolism. Expression of antioxidant pathway genes was significantly increased in 30 μM leaded cells compared to control gene.
Conclusion: The biosensor prepared from Huh7-1x-ARE-luc cell line of the reporter gene can be a convenient and efficient means for measuring oxidative compounds such as heavy metals such as lead.

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Diatoms biosilica shell, frustule, is substitute biostructures to mesoporous silica particles, which possesses their wide surfaces, nano-diameter porosity, mechanical strength, and thermal stability, optical capabilities, and the ability to bind to biomolecules can be used in biosensing applications. In this study, diatom species called Chaetoceros muelleri, was used for the fabrication of the Fe₂O₃-Au-Biosilica magnetic package. After micro-algae cultivation, the synthesis of gold nanoparticles (AuNPs) on silica walls was carried out using the bio-synthesis method, which evaluations have demonstrated the continuous formation of spherical AuNPs on the walls and its surfaces. After this step, the magnetic iron oxide nanoparticles were attached to the silica surface of the diatom, this, in turn, leads to system guiding using a magnetic field. Surface modification of diatoms magnetic complex, by using the APTES, allowed the attachment of fluorescence Rhodamine and the Herceptin antibody (Trastuzumab) to the structure. As well as the attachment of the fabricated system to target cells (SKBR3) was confirmed by fluorescence microscopic analysis. The results of this study indicate the ability and specificity of the diatom silicone shell as a "multipurpose" package for diagnostic and therapeutic activities.

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Breast cancer is a serious health concern for women. It contributes to about 23% of the cancer cases, and accounts for the second largest number of deaths among all cancers. Expensive and time consuming recognition methods currently available for recognition of breast cancer potentiates the need for improvement of novel, specific and ultrasensitive strategies. Biosensors are sensitive, specific and cost effective procedures. These also display the benefit of quick response due to direct calculation in physiological fluids (saliva, blood, serum, milk, urine etc.) in a non-invasive way. Aptamer-based biosensors for cancer cell recognition have shown advantages of rapidness, simplicity and cost-efficiency over traditional approaches. In this study, by linking DNAzyme and aptamer together, we established colorimetric biosensor for the detection of MCF7 breast cancer cells.  MUC1 and PTK7 aptamers used as specific aptamers to binding to the breast cancer cells. This manner may also evade the modification of DNA and the use of labels, which can intensely rise the cost-efficiency and simplicity of cancer cell discovery. Our results indicated that these aptamers showed good activity for breast cancer cells detection in which in the control cells no activity was observed. Results also indicated that there is a good linear relationship between the cancer cell values and colorimetric signal. Finally, the obtained results indicated a cost effective and conveniently operated approach for cancer diagnosis in future.

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These days biosensors have worthy applications in different fields such as biomedicine, disease diagnosis, treatment monitoring, various aspects of the environment, food control, drug production, and assorted sides of medical science. Recently, different types of biosensors such as enzyme biosensors, immune, tissue, DNA, and thermal biosensors have been studied precisely by some research groups. These biosensors have many advantages such as simplicity in implementation, very high sensitivity, automatic performance, intrinsic and natural small size. Another valuable benefit of biosensors is that their high-affinity paring with biomolecules allows sensitive (high-sensitivity) and selective detection from a wide range of analytes. Artificial intelligence (AI) due to its high potency, if combined with biotechnology, like biosensors, can be effective in accurate prediction, diagnosis and treatment of some diseases, including cancer. Today, Machine learning (ML) as one of the branches of AI has become a beneficial tool in analyzing and categorizing obtained data from biosensors for bioanalysis. Using ML algorithms automates the complicated processes of extraction, processing, and assaying data achieved from biosensors. This article is a review for introducing and survey of various biosensors, their applications, and ways to apply them, focusing on cancer and Covid19 which are important diseases in the world obtained from previous studies, as a summary and providing information for researchers which working in this field.
 

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Aflatoxin B1 is a type of mycotoxin produced by Aspergillus fungi during food production and storage. Aflatoxins have many toxic effects on the body that cause mutagens, teratogens and have high carcinogenic properties that cause cancer in the liver and other organs. Although conventional device methods for measuring aflatoxin B1 in food are sensitive and accurate, they have disadvantages such as high diagnostic time, high cost, the need for a trained user, and the creation of false positive results. Therefore, the development of new measuring methods has been prioritized by researchers. Among these measurement methods is the use of biosensors, which are fast, simple and more affordable and are used in the food industry today. In this work, a colorimetric optical aptasensor using gold nanoparticles with appropriate sensitivity and high selectivity was used to detect aflatoxin B1 in serum and buffer. For this purpose, gold nanoparticles were synthesized by reducing HAuCl₄ by sodium citrate (with a size of 14.40 nm and a zeta potential of -27.5). In this method, the protective effect of DNA sequence on the surface of gold nanoparticles has been used in the presence or absence of aflatoxin with the intervention of salt and the characteristic of visual color change. The detection limit of this method was estimated to be 50 ng/L and its linear range was 200-28000 ng/L. As a result, the designed aptasensor can be used for quick identification and screening of this toxin in contaminated food.
 

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Gold nanoparticles (GNPs) with unique optical properties, such as easy operation and visualized assay, have a great ability to detect different types of analytes. Today, the use of gold nanoparticles has wide applications in the field of medicine and biotechnology, including the detection of microorganisms that cause contamination in water, air and food and it is considered a suitable alternative for chemical and physical methods. New technologies in the design of biosensors based on GNPs provide the ability to identify biological compounds accurately and quickly. One of these technologies is a detection sensor based on surface plasmon resonance (SPR), which based on its optical properties, is capable of very sensitive and specific measurement of biomolecule interactions without time delay. This technology can quantify in a short time the properties of biomolecular mediators (such as oligonucleotides, proteins and bacteria) on the surface, including reaction speed, tendency and concentration of surface mediators. In this review, while investigating the surface plasmon properties of gold nanoparticles, the simple diagnostic applications of gold nanoparticles based on the localized surface plasmon (LSPR) method and detection in biomedicine.

 

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APC gene in ctDNA has been proposed as a potential biomarker for cancer diagnosis. A biosensor based on a multi-walled carbon nanotube (MWCNT) and DNA probe with fluorophore FAM (6-carboxyfluorescein) for detection of APC gene in ctDNA was developed to identify patients with colorectal cancer (CRC).
This method was designed based on the adsorption and immobilization of FAM-labeled single-stranded DNA (ssDNA) on MWCNT, which leads to the quenching of FAM fluorescence emission. By adding its cDNA could release single-stranded DNA probe (ssDNA) from the MWCNT surface and a double-stranded DNA (dsDNA) was formed. It led to the return of FAM fluorescence emission. While in the case of non-complementary DNA the corresponding dsDNA was not formed and therefore we did not have the return of FAM fluorescence emission. The results of this study showed that the biosensor based on carbon nanotubes can be used as a high-sensitivity method for the early detection of CRC.

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Milk, from its production to consumption, is exposed to a variety of microbial and chemical contaminants. Aflatoxin M1 (AFM1) is one of the most important contaminants in milk, which has always received attention due to its carcinogenic and destructive effects on the consumer. Accordingly, the rapid, sensitive, and cost-effective identification of AFM1 in milk is essential. In the present paper, an electrochemical aptasensor based on screen printed electrode (SPE) modified with magnetic nanoparticles (MNPs) and gold nanoparticles (AuNPs) was proposed to identify AFM1 in cow milk samples. SPE was activated by applying a potential within the range of -1.5 to +1 V versus the reference electrode at a scan rate of 200 mV/s for 5 continuous cycles in the 0.5 M sulfuric acid and 0.1 M potassium chloride solution. Changes of the electrode surface at different stages of preparation were assessed using cyclic voltammetry (CV) technique. Using CV in optimal conditions, it was found that the aptasensor presents a concentration range of 100-700 ng/l and a limit of detection (LOD) of 50 ng/l.  There was a linear relationship between changes of the current peak (∆I) and analyte concentration. This relationship follows the regression equation of ∆I=0.0209C+2.14 (R²=0.9897). Calculation of the relative standard deviation (RSD=3.2%) indicated the acceptable repeatability of the electrochemical aptasensor. The current peak was obtained to be 7.4% in the investigation of RSD reproducibility, indicating the good reproducibility of the electrochemical aptasensor. The obtained results showed that the aptasensor response after 8 days has only reduced by 7% compared to the first day, indicating the desirable stability of the aptasensor. The recovery percentage range for cow milk samples at concentrations of 100 and 200 ng/l was obtained to be 86.5 and 93%, respectively, showing the acceptable recovery percentage of the electrochemical aptasensor.

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