Fluorescence-based quantitative platform for ultrasensitive food allergen detection: From immunoassays to DNA sensors

Food allergies are global health issue with an increasing prevalence that affect food safety; hence, food allergen detection, labeling, and management are considered to be important priorities in the food industry. In this critical review, we provide a comprehensive overview of several fluorescence-based platforms based on different biorecognition ligands, such as antibodies, DNA, aptamers, and cells, for food allergen quantification. Traditional analytical methods are generally unsuitable for food manufacturers to accomplish the real-time identification of food allergens in food products. Therefore, it is important to develop simple, rapid, inexpensive, accurate, and sensitive methods to improve user accessibility. A fluorescence-based quantitative platform provides an excellent detection platform for food allergens because of its high sensitivity. This review summarizes the traditional antibody-based fluorescent techniques for food allergen detection, such as the time-resolved fluoroimmunoassay , immunofluorescence imaging, fluorescence enzyme-linked immune sorbent assay, flow injection fluoroimmunoassay, and fluorescence immunosensors. However, these methods suffer from disadvantages such as the significant rate of false-positive and false-negative results due to antibody cross-reactivity with nontarget food components in the complex food matrix and epitope degradation during food processing. Hence, different types of fluorescence-based immunoassays are suitable for standardization and quantification of allergens in fresh foods. In addition, we summarize new fluorescence-based quantitative platforms, including fluorescence genosensors, fluorescence cell sensors, and fluorescence aptamer sensors. With the advantages of high sensitivity and simple operation, fluorescence biosensors will have great potential in the future and could provide portable methods for multiallergen real-time detection in complex food systems.

Optical characterization of the antigen-antibody thin layer using the whispering gallery mode

We immobilized an antibody (anti-β-Galactosidase) on a polystyrene microsphere by using a covalent bond, and observed the resonance peaks in the scattered light intensity spectra related to the whispering gallery mode (WGM) excitation of the microsphere. The amount and the optical parameters, i.e., thickness and refractive index, of anti-β-Galactosidase on the sphere surface were evaluated based on an absorbance measurement and a resonance peak shift measurement, respectively. Moreover, we measured the variation of the WGM spectra depending on the concentration of the enzyme solution (β-Galactosidase), which allowed us to optically evaluate the thickness and the refractive index of the antigen-antibody layer from the shift of the WGM spectra peak.

Evaluation of optical detection platforms for multiplexed detection of proteins and the need for point-of-care biosensors for clinical use

This review investigates optical sensor platforms for protein multiplexing, the ability to analyze multiple analytes simultaneously. Multiplexing is becoming increasingly important for clinical needs because disease and therapeutic response often involve the interplay between a variety of complex biological networks encompassing multiple, rather than single, proteins. Multiplexing is generally achieved through one of two routes, either through spatial separation on a surface (different wells or spots) or with the use of unique identifiers/labels (such as spectral separation-different colored dyes, or unique beads-size or color). The strengths and weaknesses of conventional platforms such as immunoassays and new platforms involving protein arrays and lab-on-a-chip technology, including commercially-available devices, are discussed. Three major public health concerns are identified whereby detecting medically-relevant markers using Point-of-Care (POC) multiplex assays could potentially allow for a more efficient diagnosis and treatment of diseases.

Recent developments in emerging microimmunoassays

Creative and novel microimmunoassay approaches continue to proliferate across many platforms originating from several fields of study. These efforts are aimed at improving one or more metrics for clinical tests, including improved sensitivity, increased speed, reduced cost, smaller sample size, the ability to analyze multiple antigens in parallel and ease of use. Many approaches focus on the production of microarrays that accomplish standard assays in parallel, or mobile solid-support formats to overcome issues of high background noise and long incubation times. In this article, innovative developments beyond existing commercial tests in the microimmunoassay arena are reviewed, covering January 2008 to April 2012. These developing experimental platforms are discussed in terms of their ability to augment or replace current commercial approaches.