# A Photonic Label-Free Biosensor to Detect _Salmonella_ spp. in Fresh Vegetables and Meat
## 4 Conclusions  
This paper validates a novel approach to detect _Salmonella_ spp. in food samples using a photonic biosensor. The method, which is part of the Feder Bacterio project, was observed to have high sensitivity, specificity, and overall accuracy when compared to the using cultures. This finding indicates that the photonic biosensor has the potential to become a reliable and effective tool in the agroindustry for the early detection of pathogens in food samples. The biosensor was fabricated using silicon nitride and was developed using CMOS-compatible techniques. It relied on electron beam lithography and RIE-ICP etching. The immunosensor's surface was composed of eight ring resonators. These resonators were functionalized with a variety of antibodies specifically selected to detect _Salmonella_ spp. in meat and vegetable matrices. A preliminary validation of the biosensor was conducted with 100 fabricated PICs. After functionalizing the rings with these specific antibodies and attaching a microfluidic layer to the PIC, the biosensor successfully detected various bacterial concentrations. This innovative method was found to be a well-performing and feasible detection technique. The results of the immobilization control experiments provide valuable insights. They indicate that the surfaces activated for immobilization had significantly higher fluorescence intensity values than nonactivated surfaces, underlining the effectiveness of the activation process in promoting immobilization. Interestingly, no statistically significant differences were observed between the fluorescence values of the monoclonal antibody and the polyclonal antibody. Hence, both antibodies appeared to be successfully immobilized on the sensor surfaces and supported the development of the biosensor. Both the selected monoclonal antibody and the polyclonal antibody specific to _Salmonella_ spp. were immobilized on silicon nitride surfaces. Overall, these findings verify the successful immobilization of antibodies on the sensor surfaces, a critical step in biosensor development. The results underscore the effectiveness of the biosensor method in accurately detecting _Salmonella_ spp. in meat and vegetable samples, even at low concentrations. The chosen _Salmonella_ spp. specific monoclonal antibody had heightened specificity and a robust binding affinity at lower antigen concentrations. Conversely, the selected polyclonal antibody specific to _Salmonella_ spp. had a higher binding capacity to antigens across a wide range of concentrations. Nevertheless, at very high antigen concentrations, no significant results were observed. This finding highlights the strengths and limitations of the method in different contexts. The novelty of this study lies in its detection methodology. The integrated system described in this paper enables the detection of changes in the light response when specific binding occurs between the immobilized antibody on the sensor surface and the target antigen (a particular protein or enzyme found on the surface of _Salmonella_ spp.). Crucially, this process does not require the antibody to be labeled with a fluorophore to detect the antigen. This label-free detection method simplifies analysis and enhances the efficiency of _Salmonella_ spp. detection. Another notable innovation is the integration of the detection system. To date, this integrated system has not been used to detect the food pathogen _Salmonella_ spp. This novel approach offers a promising way of achieving more efficient and reliable _Salmonella_ spp. detection in food samples. Conceptualization, A.F.B., J.G.-H., M.H.P. and Y.M.T. ; methodology, A.F.B., J.G.-H., M.H.P. and Y.M.T. ; validation, A.F.B., [PERSON]-H., M.H.P. and Y.M.T. ; investigation, A.F.B., [PERSON]-H., M.H.P. and Y.M.T. ; data curation, A.F.B., J.G.-H., M.H.P. and Y.M.T. ; writing--original draft preparation, A.F.B. ; writing--review and editing, J.G.-H., M.H.P. and Y.M.T. ; funding acquisition, A.F.B., [PERSON]-H., M.H.P. and Y.M.T.