Highly sensitive determination of capsaicin with tris(2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence

Preparation of a capsaicinoids broad spectrum antibody and its application in non-enzyme immunoassay based on DMSNs@PDA@Pt

Capsaicinoids (CPCs) is a special ingredient with pungent smell in condiments, which can also be used as an exogenetic marker for kitchen waste oil. Development of immunoassay for CPCs remains a challenging due to relatively difficult preparation of the broad-spectrum antibody (Ab). In this work, a broad-spectrum polyclonal antibody (pAb) which can simultaneously recognize capsaicin (CPC), dihydrocapsaicin (DCPC), nordihydrocapsaicin (NDCPC), and N-vanillylnonanamide (N-V) is produced, and a non-enzyme immunoassay (NISA) based on this Ab, dendritic mesoporous silica nanomaterials (DMSNs), polydopamine (PDA), and high catalytic efficiency of Pt nanoparticles to prepare signal probe (DMSNs@PDA@Pt) is established. Here, the limit of detection (LOD) of NISA for CPC is as low as 0.04 μg L-1. It is worth mentioning that the LOD of the proposed NISA is at least 23 times lower than that of traditional enzyme-linked immunosorbent assay (ELISA) based on horseradish peroxidase (HRP). Moreover, the proposed NISA is applied to detect CPCs in edible oil samples, the result has good consistency with that of ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The proposed NISA based on DMSN@PDA@Pt and broad-spectrum Ab is an ideal tool for highly effective screening CPCs for kitchen waste oil abuse surveillance.

Genetic Regulation, Environmental Cues, and Extraction Methods for Higher Yield of Secondary Metabolites in Capsicum

Capsicum (chili pepper) is a widely popular and highly consumed fruit crop with beneficial secondary metabolites such as capsaicinoids, carotenoids, flavonoids, and polyphenols, among others. Interestingly, the secondary metabolite profile is a dynamic function of biosynthetic enzymes, regulatory transcription factors, developmental stage, abiotic and biotic environment, and extraction methods. We propose active manipulable genetic, environmental, and extraction controls for the modulation of quality and quantity of desired secondary metabolites in Capsicum species. Specific biosynthetic genes such as Pun (AT3) and AMT in the capsaicinoids pathway and PSY, LCY, and CCS in the carotenoid pathway can be genetically engineered for enhanced production of capsaicinoids and carotenoids, respectively. Generally, secondary metabolites increase with the ripening of the fruit; however, transcriptional regulators such as MYB, bHLH, and ERF control the extent of accumulation in specific tissues. The precise tuning of biotic and abiotic factors such as light, temperature, and chemical elicitors can maximize the accumulation and retention of secondary metabolites in pre- and postharvest settings. Finally, optimized extraction methods such as ultrasonication and supercritical fluid method can lead to a higher yield of secondary metabolites. Together, the integrated understanding of the genetic regulation of biosynthesis, elicitation treatments, and optimization of extraction methods can maximize the industrial production of secondary metabolites in Capsicum.

A universal CRISPR/Cas12a-powered intelligent point-of-care testing platform for multiple small molecules in the healthcare, environment, and food

Growing studies focusing on nuclear acid detection via the emerging CRISPR technique demonstrate its promising application. However, limited works solve the identification of non-nucleic acid targets, especially multiple small molecules. To address challenges for point-of-care testing (POCT) in complex matrices for healthcare, environment, and food safety, we developed CRISPR Cas12a-powered highly sensitive, high throughput, intelligent POCT (iPOCT) for multiple small molecules based on a smartphone-controlled reader. As a proof of concept, aflatoxin B1 (AFB1), benzo[a]pyrene (BaP), and capsaicin (CAP) were chosen as multiple targets. First, three antigens were preloaded in independent microwells. Then, the antibody/antigen-induced fluorescent signals were consecutively transferred from the biotin-streptavidin to CRISPR/Cas12a system. Third, the fluorescent signals were recorded by a smartphone-controlled handheld dark-box readout. Under optimization, detection limits in AFB1, BaP, and CAP were 0.00257, 4.971, and 794.6 fg/mL with wide linear ranges up to four orders of magnitude. Using urine, water, soybean oil, wheat, and peanuts as the complex matrix, we recorded high selectivity, considerable recovery, repeatability, and high consistency comparison to HPLC-MS/MS methods. This work promises a practical intelligent POCT platform for multiple targets in lipid-soluble and water-soluble matrices and could be extensively applied for healthcare, environment, and food safety.

Ru(bpy)32+ as a photoinduced oxidase mimic for colorimetric detection of biothiols

We have found that tris (2,2'-bipyridyl) ruthenium (II) (Ru(bpy)₃²⁺) possesses a high photo-induced oxidase-like activity and is capable of catalyzing the color reaction of 3,3',5,5'-tetramethylbenzidine (TMB) with dissolved oxygen. Ru(bpy)₃²⁺ has a catalytic constant (K_cat) that is twice as high as that of fluorescein, 170 and 275-fold higher than that of 9-mesityl-10-methyl acridine and Eosin Y, respectively. Electron spin resonance spectroscopy (ESR) and radical scavenging experiments have verified the major active radicals involved in the color reaction are •OH. A colorimetric biothiol assay has been successfully developed for the oxidase-like activity of Ru(bpy)₃²⁺ can be suppressed by sulfhydryl compounds. A linear dependence between the decrease in absorbance and the logarithm of thiol concentrations can be found ranging from 5.0 to 50 μM, with a detection limit of 1.0 μM. This work reveals a new oxidase mimic with high catalytic activity and will facilitate the utilization of this oxidase mimic in biochemical analysis.