# Aptamer-Based Biosensors for the Analytical Determination of Bisphenol A in Foodstuffs
## 3. Aptamer-Based Biosensor Applications Tested for the Determination of BPA in Real Food Samples  
So far, aptamer-based biosensors have not been applied to an extensive monitoring of the levels of BPA in food samples. However, several authors reported the designs of various kinds of aptasensors to be specifically used in the detection of BPA in food samples. After their construction, all the aptasensors were tested to verify their feasibility in the analysis of real samples. All foods used in the applicability tests were liquids, mostly tap or mineralized water [45; 49; 51; 52; 53; 54; 55; 56; 57; 58; 59; 60; 61], followed by milk and fruit juices [47; 53; 59; 60; 62; 63] and red wine samples [64]. Either no treatment (water samples) or just a quick pre-treatment of samples was necessary. Fruit juices were filtered to remove any residues of solid particles. Milk samples required a slightly time-consuming pre-treatment to eliminate fats by centrifugation and to eliminate proteins by precipitation and further centrifugation. [PERSON] et al. [65] analyzed two different brands of canned food (green beans and sweet peas), but they carried out the experiments only on the liquid portion of the cans. However, studies in the literature demonstrated that, when canned foods are analyzed, the BPA concentrations are higher in the solid portion than those detected in the liquid portion [33; 66]. Especially in the case of canned seafoods, this should be considered in relation to the high probability of contamination due to the ingestion of microplastics by fish in the marine environment [6; 8; 9]. At last, [PERSON] et al. [67] investigated the application of their colorimetric aptasensor directly on grains of commercially available steamed rice pre-treated with a solution of BPA.  
The limit of detection (LOD) and recovery at different concentrations of BPA were the main performance parameters that the authors evaluated. In addition, the selectivity of each aptasensor was generally assessed vs. possible interferent substances or BPA analogs, including some compounds currently used as substitutes of BPA in plastic manufacturing. In several studies the reproducibility was also measured. Both selectivity and reproducibility proved to be good.  
In Table 2 the LOD and recovery percentage values obtained in the analysis of real samples are reported, along with a brief description of the developed aptasensor strategies (see next paragraph). The LODs, estimated mostly using BPA solutions at different concentrations, were generally very low. [PERSON] et al. [45] compared the performance of their aptasensor to other more traditional methods. They showed that the LOD obtained by the aptasensor was generally lower, except for the case of GC-MS and electrochemical methods. Nonetheless, the authors concluded that their detection technique was preferable considering the undoubted advantages offered by the aptasensor, such as a low cost and a simple detection process in addition to a still-high sensitivity.  
Generally, aptasensors tested in food samples showed good stability. Only [PERSON] et al. found that their biosensor was not very stable when compared to the LC-MS/MS method, although they suggested that this problem could be overcome by carefully checking the temperature and buffering solution [59].