Colourimetric detection of swine-specific DNA for halal authentication using gold nanoparticles

Magnetic-gold nanoparticle-mediated paper-based biosensor for highly sensitive colorimetric detection of food adulteration

Food adulteration presents a significant challenge due to the evasion of legal oversight and the difficulty of identification. Addressing this issue, there is an urgent need for on-site, rapid, visually based small-scale equipment, along with large-scale screening technology, to enable prompt results without providing opportunities for dishonest traders to react. Colorimetric reactions offer advantages in terms of speed, visualization, and miniaturization. However, there is a scarcity of suitable colorimetric reactions for food adulteration detection, and interference from colored food impurities and easily comparable color results affects accuracy. To overcome limitations, this study introduces a novel approach utilizing polydopamine magnetic nanoparticles to enrich DNA in food samples, effectively eliminating interfering components. By employing gold nanoparticles to generate magnetic-gold nanoparticles, a single magnetic bead achieves simultaneous enrichment, impurity removal, and detection. The use of paper-based biosensors and visualization equipment allows for the visualization and digital analysis of results, achieving a low detection limit of 4.59 nmol mL-1. The method also exhibits high accuracy and repeatability, with a RSD ranging from 1.6 % to 4.0 %. This innovative colorimetric method addresses the need for rapid, miniaturized, and large-scale detection, thus providing a solution for food adulteration challenges.

Advances and challenges in conventional and modern techniques for halal food authentication: A review

Food is one of the most necessary needs since human civilization. For Muslims, it is mandatory to consume halal food. From a halal authentication perspective, adulteration of food products is an emerging challenge worldwide. The demand for halal food consumption has resulted in an ever-increasing need for halal product validity. In the market, there are several food products in which actual ingredients and their source are not mentioned on the label and cannot be observed by the naked eye. Commonly nonhalal items include pig derivatives like lard, pork, and gelatin derivatives, dead meats, alcohol, blood, and prohibited animals. Purposely, various conventional and modern methods offer precise approaches to ensure the halalness and wholesomeness of food products. Conventional methods are physiochemical (dielectric) and electrophoresis. At the same time, modern techniques include high-pressure liquid chromatography (HPLC), gas chromatography (GC), electronic nose (E-Nose), polymerase chain reaction (PCR), enzyme-linked immunosorbent assay (ELISA), differential scanning calorimetry (DSC), nuclear magnetic resonance (NMR), near-infrared (NIR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. This review intends to give an extensive and updated overview of conventional and modern analytical methods for ensuring food halal authenticity.

Advances in colorimetric aptasensors for heavy metal ion detection utilizing nanomaterials: a comprehensive review

Heavy metal ion contamination poses significant environmental and health risks, necessitating rapid and efficient detection methods. In the last decade, colorimetric aptasensors have emerged as powerful tools for heavy metal ion detection, owing to their notable attributes such as high specificity, facile synthesis, adaptability to modifications, long-term stability, and heightened sensitivity. This comprehensive overview summarizes the key developments in this field over the past ten years. It discusses the principles, design strategies, and innovative techniques employed in colorimetric aptasensors using nanomaterials. Recent advancements in enhancing sensitivity, selectivity, and on-site applicability are highlighted. The review also presents application studies of successful heavy metal ion detection using colorimetric aptasensors, underlining their potential for environmental monitoring and health protection. Finally, future directions and challenges in the continued evolution of these aptasensors are outlined.

The Optimization of a Label-Free Electrochemical DNA Biosensor for Detection of Sus scrofa mtDNA as Food Adulterations

Fast, sensitive, and easy-to-use methods for detecting DNA related to food adulteration, health, religious, and commercial purposes are evolving. In this research, a label-free electrochemical DNA biosensor method was developed for the detection of pork in processed meat samples. Gold electrodeposited screen-printed carbon electrodes (SPCEs) were used and characterized using SEM and cyclic voltammetry. A biotinylated probe DNA sequence of the Cyt b S. scrofa gene mtDNA used as a sensing element containing guanine substituted by inosine bases. The detection of probe-target DNA hybridization on the streptavidin-modified gold SPCE surface was carried out by the peak guanine oxidation of the target using differential pulse voltammetry (DPV). The optimum experimental conditions of data processing using the Box-Behnken design were obtained after 90 min of streptavidin incubation time, at the DNA probe concentration of 1.0 µg/mL, and after 5 min of probe-target DNA hybridization. The detection limit was 0.135 µg/mL, with a linearity range of 0.5-1.5 µg/mL. The resulting current response indicated that this detection method was selective against 5% pork DNA in a mixture of meat samples. This electrochemical biosensor method can be developed into a portable point-of-care detection method for the presence of pork or food adulterations.

LSPR-based colorimetric biosensing for food quality and safety

Ensuring consistently high quality and safety is paramount to food producers and consumers alike. Wet chemistry and microbiological methods provide accurate results, but those methods are not conducive to rapid, onsite testing needs. Hence, many efforts have focused on rapid testing for food quality and safety, including the development of various biosensors. Herein, we focus on a group of biosensors, which provide visually recognizable colorimetric signals within minutes and can be used onsite. Although there are different ways to achieve visual color-change signals, we restrict our focus on sensors that exploit the localized surface plasmon resonance (LSPR) phenomenon of metal nanoparticles, primarily gold and silver nanoparticles. The typical approach in the design of LSPR biosensors is to conjugate biorecognition ligands on the surface of metal nanoparticles and allow the ligands to specifically recognize and bind the target analyte. This ligand-target binding reaction leads to a change in color of the test sample and a concomitant shift in the ultraviolet-visual absorption peak. Various designs applying this and other signal generation schemes are reviewed with an emphasis on those applied for evaluating factors that compromise the quality and safety of food and agricultural products. The LSPR-based colorimetric biosensing platform is a promising technology for enhancing food quality and safety. Aided by the advances in nanotechnology, this sensing technique lends itself easily for further development on field-deployable platforms such as smartphones for onsite and end-user applications.

CRISPR-Cas12-Based Rapid Authentication of Halal Food

The halal food market is globally growing along with the increased risk of adulteration. We proposed an amplification-free and mix-to-read CRISPR-Cas12-based nucleic acid analytical strategy allowing rapid identification and analysis of pork components, thus enriching the toolbox for ensuring halal food authenticity. We designed and optimized guide RNA (gRNA) targeting the pork cytochrome b (Cyt b) gene. gRNA allowed specific identification of the target Cyt b gene from pork components followed by activation of Cas12 protein to abundantly cleave single-stranded DNA probes with terminally labeled fluorophore and quencher groups, thus turning on fluorescence. The presence of the pork Cyt b gene thus can be mix-and-read- and only-one-step-detected, which may indicate the risk of halal food adulteration. The method allowed specific discrimination of pork meat from beef, mutton, and chicken and yielded a detection limit of 2.7 ng/μL of total DNA from pork meat. The reliability of the method was tested using the following processed meat products: halal foods beef luncheon meat and spiced beef and non-halal foods sausage and dried pork slices. The CRISPR-Cas12-based nucleic acid test strategy is promising for rapid food authentication.

Development and comparison of cross-linking and non-crosslinking probe-gold nanoparticle hybridization assays for direct detection of unamplified bovine viral diarrhea virus-RNA

BACKGROUND

Bovine viral diarrhea virus (BVDV) is a major economic disease that has been spread in most countries. In addition to vaccination, one of the main ways to control the disease and prevent it from spreading is to detect and cull infected animals, especially those with persistent infection (PI). We developed and compared two colorimetric biosensor assays based on probe-modified gold nanoparticles (AuNPs) to detect BVDV. Specific probes were designed to detect the 5' untranslated region of BVDV-RNA. The thiolated probes were immobilized on the surface of the AuNPs. Two methods of cross-linking (CL) and non-crosslinking (NCL) probe-AuNPs hybridization were developed and compared.

RESULTS

The hybridization of positive targets with the two probe-AuNPs formed a polymeric network between the AuNPs which led to the aggregation of nanoparticles and color change from red to blue. Alternatively, in the NCL mode, the hybridization of complementary targets with the probe-AuNPs resulted in the increased electrostatic repulsion in nanoparticles and the increased stabilization against salt-induced aggregation. The CL and NCL assays had detection limits of 6.83 and 44.36 ng/reaction, respectively.

CONCLUSION

The CL assay showed a higher sensitivity and specificity; in contrast, the NCL assay did not require optimizing and controlling of hybridization temperature and showed a higher response speed. However, both the developed methods are cost-effective and easy to perform and also could be implemented on-site or in local laboratories in low-resource countries.

Current analytical methods for porcine identification in meat and meat products

Authentication of meat products is critical in the food industry. Meat adulteration may lead to religious apprehensions, financial gain and food-toxicities such as meat allergies. Thus, empirical validation of the quality and constituents of meat is paramount. Various analytical methods often based on protein or DNA measurements are utilized to identify meat species. Protein-based methods, including electrophoretic and immunological techniques, are at times unsuitable for discriminating closely related species. Most of these methods have been replaced by more accurate and sensitive detection methods, such as DNA-based techniques. Emerging technologies like DNA barcoding and mass spectrometry are still in their infancy when it comes to their utilization in meat detection. Gold nanobiosensors have shown some promise in this regard. However, its applicability in small scale industries is distant. This article comprehensively reviews the recent developments in the field of analytical methods used for porcine identification.

High affinity truncated aptamers for ultra-sensitive colorimetric detection of bisphenol A with label-free aptasensor

The widespread exposure of bisphenol A (BPA) presents a significant risk to human health. A rapid, ultra-sensitive and label-free colorimetric aptasensor using high affinity truncated aptamers was developed for BPA detection. Truncated 38-mer and 12-mer aptamers specific for BPA were obtained through rationally truncation from 63-mer BPA aptamer. The dissociation constants (K_d) of 38-mer and 12-mer aptamers were determined to be 13.17 nM and 27.05 nM. Then, truncated aptamers were used in label-free colorimetric detection assays based on gold nanoparticles (AuNPs). The limit of detections of aptasensors using 38-mer and 12-mer aptamers were 7.60 pM and 14.41 pM, which were 265-fold and 140-fold lower than that of the aptasensor using 63-mer aptamer, respectively. The recovery rates in milk, orange juice and mineralized water samples were 93.88% to 107.30%. Therefore, the developed BPA colorimetric aptasensor using truncated aptamers has great application prospects in food safety control and environmental monitoring.

Synthesis of magnetic nanoparticles to detect Sudan dye adulteration in chilli powders

Magnetic nanoparticles were synthesised to extract Sudan dyes from chilli powders. The adsorbents used were magnetic ferroferric oxide nanoparticles coated with polystyrene. The extraction procedures for Sudan dyes comprised liquid-solid extraction and magnetic solid phase extraction. The conditions were optimised to achieve efficient magnetic solid phase extraction, including extraction and desorption time, type and volume of the desorption solvent, and the mass of the adsorbents. Repeatability tests showed satisfactory recovery rates of 80.2-115.8%, with a relative standard deviation <3.8%. The results suggested that the proposed extraction method was effective and efficient to extract Sudan dyes from chilli powders. The extraction process was simpler compared with traditional approaches because the adsorbents can be rapidly removed from the sample matrix using a permanent magnet. The use of recyclable adsorbents decreased the cost greatly. Chilli powder samples collected from local markets in Singapore were tested using the proposed method under optimum conditions.

New Vortex-Synchronized Matrix Solid-Phase Dispersion Method for Simultaneous Determination of Four Anthraquinones in Cassiae Semen

In this study, a green ionic-liquid based vortex-synchronized matrix solid-phase dispersion (VS-MSPD) combined with high performance liquid chromatography (HPLC) method was developed as a quantitative determination method for four anthraquinones in Cassiae Semen. Two conventional adsorbents, C₁₈ and silica gel were investigated. The strategy included two steps: Extraction and determination. Wasted crab shells were used as an alternative adsorbent and ionic liquid was used as an alternative solvent in the first step. Factors affecting extraction efficiency were optimized: A sample/adsorbent ratio of 2:1, a grinding time of 3 min, a vortex time of 3 min, and ionic liquid ([Domim]HSO₄, 250 mM) was used as eluent in the VS-MSPD procedure. As a result, the established method provided satisfactory linearity (R > 0.999), good accuracy and high reproducibility (RSD < 4.60%), and it exhibited the advantages of smaller sample amounts, shorter extraction time, less volume of elution solvent, and was much more environmental-friendly when compared with other conventional methods.

Structural Modification of Fish Gelatin by the Addition of Gellan, κ-Carrageenan, and Salts Mimics the Critical Physicochemical Properties of Pork Gelatin

Pork gelatin is not suitable for halal and kosher application; however, fish gelatin (FG) can be modified for use as a pork gelatin (PG) mimetic. Herein, low-acyl gellan (GE), κ-carrageenan (KC), and salts (CaCl₂ or KCl) were combined with a 180 Bloom tilapia FG. A formulation comprising 5.925% (w/v) FG + 0.025% (w/v) GE + 3mM CaCl₂ best matched the physicochemical properties of PG. The modification increased the FG gel strength from 115 ± 2 to 149 ± 2 g (matching the 148 ± 2 of PG), while the T_m increased from 27.9 ± 1.0 to 32.4 ± 0.8 °C (matching the 33.1 ± 0.3 °C of PG). Nanoaggregates (diameter between 150 and 300 nm) could be an important structural factor affecting the physicochemical properties, as both PG and GE-modified FG showed a similar frequency distribution in this size group (57.4 ± 1.6% (PG) compared with 56.3 ± 2.2% (modified FG)). To further explore the differences between KC and GE in modifying of FG's structure, the FG-KC and FG-GE gels were compared. The zeta potential and Fourier transform infrared (FTIR) spectroscopy results for the FG-KC gel supported an associative interaction with complex formation, as indicated from the large aggregates and amorphous phase under atomic force microscopy (AFM). Contrastingly, a segregative FG-GE interaction took place in presence of CaCl₂ . These structures and interaction differences between FG-GE and FG-KC influenced the macro-properties of FG, possibly explaining the differences in the modification of the melting temperature of FG. A diagram representing the interaction-structure-physicochemical properties was proposed to explain the differences between the FG-GE and FG-KC gels.

PRACTICAL APPLICATION

Certain people cannot consume any pork product or derivatives for religious reasons, thus it is essential to find a pork gelatin (PG) substitute for food product development. The commonly used polysaccharides, gellan and carrageenan, together with salt, can be added to fish gelatin (FG) to match the textural properties of PG, representing a promising substitute for PG. The difference in the mechanism of gellan and carrageenan to improve properties of FG has been revealed from nanostructure level. The use of food grade ingredients and simple mixing process are favorable in the food industry.