Validation of a Fluorescence Sensor Microtiterplate for Biogenic Amines in Meat and Cheese

Facile Synthesis of PEGylated Gold Nanoparticles for Enhanced Colorimetric Detection of Histamine

Histamine is among the biogenic amines that are formed during the microbial decarboxylation of amino acids in various food products, posing a significant threat to both food safety and human health. Herein, we present a one-step synthesis of PEGylated gold nanoparticles (PEG-AuNPs) for rapid, simple, and cost-effective colorimetric histamine detection. PEG-AuNPs' surface plasmon resonance (SPR) range at 520-530 nm with a hydrodynamic size distribution of 20-40 nm. Fourier transform infrared (FT-IR) spectra confirmed the reduction of AuNPs at 1645 cm-1 along with the other observed peaks at 2870, 1350, and 1100 cm-1 as a strong evidence for the presence of PEG. Upon the addition of histamine to the PEG-AuNP solution, transmission electron microscopy (TEM) highlighted the aggregation of nanoparticles. In addition, red shifting and a decrease in the absorbance of the SPR peak along with the appearance of an additional peak at ∼690 nm was observed in the PEG-AuNP absorption spectra in the presence of histamine. Increasing the PEG concentration in the gold colloids leads to the formation of a protective barrier around the surface of nanoparticles, which influences the colloidal stability by impeding the aggregation of PEG-AuNPs upon histamine addition. The minimum colorimetric response of PEG-AuNPs to histamine concentration is 30 ppm, as assessed by the naked eye. The absorption ratio (A690/A526) showed a linear dynamic range from 20 to 100 ppm with a limit of detection of 9.357 μM. Additionally, the assay demonstrates a commendable selectivity toward histamine analyte.

Tectomer-Mediated Optical Nanosensors for Tyramine Determination

The development of optical sensors for in situ testing has become of great interest in the rapid diagnostics industry. We report here the development of simple, low-cost optical nanosensors for the semi-quantitative detection or naked-eye detection of tyramine (a biogenic amine whose production is commonly associated with food spoilage) when coupled to Au(III)/tectomer films deposited on polylactic acid (PLA) supports. Tectomers are two-dimensional oligoglycine self-assemblies, whose terminal amino groups enable both the immobilization of Au(III) and its adhesion to PLA. Upon exposure to tyramine, a non-enzymatic redox reaction takes place in which Au(III) in the tectomer matrix is reduced by tyramine to gold nanoparticles, whose reddish-purple color depends on the tyramine concentration and can be identified by measuring the RGB coordinates (Red-Green-Blue coordinates) using a smartphone color recognition app. Moreover, a more accurate quantification of tyramine in the range from 0.048 to 10 μM could be performed by measuring the reflectance of the sensing layers and the absorbance of the characteristic 550 nm plasmon band of the gold nanoparticles. The relative standard deviation (RSD) of the method was 4.2% (n = 5) with a limit of detection (LOD) of 0.014 μM. A remarkable selectivity was achieved for tyramine detection in the presence of other biogenic amines, especially histamine. This methodology, based on the optical properties of Au(III)/tectomer hybrid coatings, is promising for its application in food quality control and smart food packaging.

Dipsticks with Reflectometric Readout of an NIR Dye for Determination of Biogenic Amines

Electrospun nanofibers (ENFs) are remarkable analytical tools for quantitative analysis since they are inexpensive, easily produced in uniform homogenous mats, and provide a high surface area-to-volume ratio. Taking advantage of these characteristics, a near-infrared (NIR)-dye was doped as chemosensor into ENFs of about 500 nm in diameter electrospun into 50 µm thick mats on indium tin oxide (ITO) supports. The mats were made of cellulose acetate (CA) and used as a sensor layer on optical dipsticks for the determination of biogenic amines (BAs) in food. The ENFs contained the chromogenic amine-reactive chameleon dye S0378 which is green and turns blue upon formation of a dye-BA conjugate. This SN1-reaction of the S0378 dye with various BAs was monitored by reflectance measurements at 635 nm where the intrinsic absorption of biological material is low. The difference of the reflectance before and after the reaction is proportional to BA levels from 0.04–1 mM. The LODs are in the range from 0.03–0.09 mM, concentrations that can induce food poisoning but are not recognized by the human nose. The calibration plots of histamine, putrescine, spermidine, and tyramine are very similar and suggesting the use of the dipsticks to monitor the total sample BA content. Furthermore, the dipsticks are selective to primary amines (both mono- and diamines) and show low interference towards most nucleophiles. A minute interference of proteins in real samples can be overcome by appropriate sample pretreatment. Hence, the ageing of seafood samples could be monitored via their total BA content which rose up to 21.7 ± 3.2 µmol/g over six days of storage. This demonstrates that optically doped NFs represent viable sensor and transducer materials for food analysis with dipsticks.

Optical sensors for determination of biogenic amines in food

This review presents the state-of-the-art of optical sensors for determination of biogenic amines (BAs) in food by publications covering about the last 10 years. Interest in the development of rapid and preferably on-site methods for quantification of BAs is based on their important role in implementation and regulation of various physiological processes. At the same time, BAs can develop in different kinds of food by fermentation processes or microbial activity or arise due to contamination, which induces toxicological risks and food poisoning and causes serious health issues. Therefore, various optical chemosensor systems have been devised that are easy to assemble and fast responding and low-cost analytical tools. If amenable to on-site analysis, they are an attractive alternative to existing instrumental analytical methods used for BA determination in food. Hence, also portable sensor systems or dipstick sensors are described based on various probes that typically enable signal readouts such as photometry, reflectometry, luminescence, surface-enhanced Raman spectroscopy, or ellipsometry. The quantification of BAs in real food samples and the design of the sensors are highlighted and the analytical figures of merit are compared. Future instrumental trends for BA sensing point to the use of cell phone-based fully automated optical evaluation and devices that could even comprise microfluidic micro total analysis systems.

Optical Recognition of Ammonia and Amine Vapor Using "Turn-on" Fluorescent Chitosan Nanoparticles Imprinted on Cellulose Strips

A practical fluorescent test dipstick for an efficient recognition of ammonia and amines vapors was developed. The prepared testing strip was based on a composite of molecularly imprinted chitosan nanoparticles, supported on cellulose paper assay, with artificial fluorescent receptor sites for ammonia/amines recognition in aqueous and gaseous phases. A modified chitosan nanoparticles containing fluorescein molecules, were successfully prepared and employed on cellulose paper strip creating fluorescent cellulose (FL-Cell) to act as "turn-on" fluorescent sensor for sensing and determining ammonia and organic amine vapor. We employed chitosan nanoparticles that had fluorescein incorporated as the fluorescent probe molecule, with a readout limit achieved for aqueous ammonia as low as 280 ppm at room temperature and atmospheric pressure. The sensor responded linearly relying on the aqueous ammonia concentration in the range of 0.13-280 ppm. The chromogenic fluorescent cellulose platform response depended on the acid-base characteristic effects of the fluorescein probe. The protonated form of fluorescein molecules immobilized within the chitosan nanoparticles were in a nanoenvironment demonstrating only weak fluorescence. When binding to ammonia/amine vapor, the fluorescein active sites were deprotonated and exhibited higher "turned-on" fluorescence as a result of exposure to those alkaline species. The simple fabrication and abovementioned characteristics of such fluorescent chitosan nanoparticles are such that they should be applicable for monitoring of ammonia/amines in either aqueous or vapor states. We studied the distribution of the fluorescent chitosan onto paper sheets fabricated from bleached bagasse pulp and coated with two different thicknesses of a fluorescent nanochitosan and blank nanochitosan solutions. A thin fluorescent nanochitosan layer was created on the surface of cellulose strips using an applicator. Its distribution was assessed by scanning electron microscopic (SEM) and transmission electron microscopic (TEM) analysis as well as Fourier-transform infrared spectroscopic (FT-IR) measurements. The mechanical properties were also tested. The exploitation of this "turn-on" fluorescence sensor invented platform should be amenable to different situations where determination of ammonia/amine vapor or aqueous solution is required.

Occurrence of biogenic amines in sufu obtained from Chinese market

This study aims at examining the level of biogenic amines (BAs) in different kinds of sufu commonly consumed in China. The correlation between different BAs and physical and chemical index in sufu samples was also investigated. The results proved that different processing technologies altered the distribution of BAs in commercial sufu. Total BA level was significantly correlated with salt content and pH. Some of the sufu samples in this survey contained higher levels of BAs, of which 26.6% of the samples might induce histamine poisoning, 15.6% might induce headache in virtue of phenylethylamine, and 23.4% might cause migraine and headache in virtue of tyramine. Moreover, 6.3% of the sufu samples with total BA content over 1000 mg/kg may be harmful to human health. From the food safety perspective, some sufu should not be excessively consumed daily and should be processed under strict sanitary conditions to decrease the BA level.

Functional electrospun nanofibers for multimodal sensitive detection of biogenic amines in food via a simple dipstick assay

Electrospun nanofibers (ENFs) are promising materials for rapid diagnostic tests like lateral flow assays and dipsticks because they offer an immense surface area while excluding minimal volume, a variety of functional surface groups, and can entrap functional additives within their interior. Here, we show that ENFs on sample pads are superior in comparison to standard polymer membranes for the optical detection of biogenic amines (BAs) in food using a dipstick format. Specifically, cellulose acetate (CA) fibers doped with 2 mg/mL of the chromogenic and fluorogenic amine-reactive chameleon dye Py-1 were electrospun into uniform anionic mats. Those extract cationic BAs from real samples and Py-1 transduces BA concentrations into a change of color, reflectance, and fluorescence. Dropping a BA sample onto the nanofiber mat converts the weakly fluorescent pyrylium dye Py-1 into a strongly red emitting pyridinium dye. For the first time, a simple UV lamp excites fluorescence and a digital camera acts as detector. The intensity ratio of the red to the blue channel of the digital image is dependent on the concentration of most relevant BAs indicating food spoilage from 10 to 250 μM. This matches the permitted limits for BAs in foods and no false positive signals arise from secondary and tertiary amines. BA detection in seafood samples was also demonstrated successfully. The nanofiber mat dipsticks were up to sixfold more sensitive than those using a polymer membrane with the same dye embedded. Hence, nanofiber-based tests are not only superior to polymer-based dipstick assays, but will also improve the performance of established tests related to food safety, medical diagnostics, and environmental testing. Graphical Absract ᅟ.

Development of new chemiluminescence biosensors for determination of biogenic amines in meat

Development of chemiluminescence one-shot biosensors for determination of biogenic amines is described and compared with high-performance liquid chromatography (HPLC) method coupled with pre-column derivatisation. The biosensors are based on enzymatic oxidation to 4-aminobutyraldehyde with putrescine oxidase or diamine oxidase as catalysts. The lowest measured concentration for the biosensor with putrescine oxidase was 1mg/L. The detection limit, calculated as 3σ value, was 0.8mg/L. The biosensor with diamine oxidase had the lowest measured concentration of 1mg/L of putrescine. Detection limit, calculated as 3σ value, was 1.3mg/L. Biosensors were tested on five different meat samples, and the results were compared with HPLC coupled with pre-column derivatization. Results showed that new biosensors could be used in determination of putrescine concentration in meat samples but improvements, such as sample pretreatment before determination or design of interference free biosensor, are required.