Using immunosensors to detect biomarkers in even ultra-low quantities, a new disposable device can identify common allergens — such as egg proteins in wine — in food and drinks. Quicker, easier to use and less expensive to manufacture than commercial alternatives, the innovation could also potentially be adapted to detect biomarkers in other substances, including blood, urine and saliva. 

A paper published May 1 in Talanta outlines the design of the new electrochemical microfluidic device, proposed by researchers in Brazil. It was tested by measuring levels of ovalbumin, a protein found in egg whites, in five samples of wine. The device is based on magneto-immunoassay detection; it relies on magnetic beads and antibodies to detect the protein at lower concentrations and at faster speeds than current state-of-the-art methods that use traditional immunoassays, which measure the levels of a protein through antibodies alone.

Egg-white allergy is one of the most common food allergies in the world, yet ovalbumin is included in many hair and skin care products. It also has many applications in foods and beverages. The protein is commonly used in wine fining, the removal of polyphenols, such as tannins, from wine to improve its taste. Decantation or filtration steps then eliminate the ovalbumin from the end product, but the process is not perfect. Traces of the protein may still remain in the wine, which can cause significant allergic reactions in sensitive consumers.

Ronaldo Censi Faria, a co-author of the paper and an associate professor at Universidade Federal de São Carlos, told The Academic Times that his research group has recently been focused on creating simple and low-cost devices for detecting protein biomarkers in order to help diagnose diseases such as cancer, Alzheimer's and COVID-19. 

"We have been working on the development of new analytical methods for the detection of biomarkers that include proteins and genetic materials. The devices involve the use of biosensors in this case, [also known as] immunosensors," Faria said. "The immunosensors that we developed employ the same electrochemical techniques used in commercial glucometers, which can lead to a simple and portable device."

Faria explained that his system's use of both antibodies and magnetic beads makes it more versatile and better able to capture the biomarker inside the wine than alternatives. "We proposed the construction of a new device that involves electrochemical sensors and microfluidics in a unique platform [that is] fully disposable," he continued, noting that the physical device was fabricated with a low-cost home cutting machine using inexpensive materials, including plastics, vinyl adhesives and conductive inks.

"The differential of our method is the simplicity of the immunoassay, requiring just a few steps to perform the analyses in a short time — 60 minutes," Faria said. The portable device needs only a few microliters of samples. It was capable of eight simultaneous analyses in this study, and the authors said it can easily be modified to simultaneously detect up to eight other allergen proteins in different foods or beverages.

The researchers compared their device with the enzyme-linked immunosorbent assay, known as ELISA, which is a commonly applied method for protein detection. ELISA is frequently used in medicine to diagnose diseases and in food-allergen detection, according to the paper. "However, in addition to requiring qualified personnel, in some cases ELISA tends to provide only semi-quantitative information, or else it does not have enough sensitivity for the allergen detection in some foods," the authors reported. 

They tested both ELISA and their new approach, using them to measure ovalbumin in the red and white wine samples. Both approaches detected more of the protein in the red wines than in the white wines. The newly proposed device achieved "simple and fast determination of ovalbumin with remarkable sensitivity" on par with ELISA. Importantly, however, the team's novel device cost less than $1 per unit to manufacture, while materials for the ELISA method cost about $5.25.

"The next step would be to expand the tests to other foods that have ovalbumin in their composition or production process, such as cookies, pasta and chicken meat," Faria explained. The platform could also be used to detect mycotoxins — toxins that can be found in food and are produced by fungi — and specifically ochratoxin, which is common in coffee and grapes.

In making this technology commercially available, Faria indicated that more dedicated government funding will play a key role, noting that this has been "significantly decreasing" over the last few years in Brazil.

"The proposed device can open many routes, [and] it could be easily adapted for the detection of other proteins. The magneto-immunoassay developed could be applied not only in food samples but even for the detection of protein as biomarkers in biological samples," he said.

The study, "Disposable electrochemical microfluidic device for ultrasensitive detection of egg allergen in wine samples," published May 1 in Talanta, was authored by Thaísa Aparecida Baldo, Camila dos Anjos Proença, Tayane Aguiar Freitas and Ronaldo Censi Faria, Universidade Federal de São Carlos; Fabiana da Silva Felix, Universidade Federal de Lavras; Solange Kazumi Sakata, Instituto de Pesquisa Energéticas e Nucleares; and Lúcio Angnes, Universidade de São Paulo.