## 5 Conclusions  
In this review, electrochemical (bio)sensors for the detection of b AAs were summarized. Electrochemical (bio)sensors as well as POC devices are relatively new avenues for reliable, accurate, sensitive, selective, green, cheap on the detection of b AA, involved in metabolic diseases such as MSUD, and are in line with current European and worldwide developments, concerning public health issues and representing the state of art on developing analytical methodologies. However, the use of electrochemical (bio)sensors in the detection of b AA have been poorly studied, as it can be seen from the lack of relevant studies in the literature. Although years of research have provided a lot of information on conventional analytical methods such as MS, limited research was made in the field of electrochemical (bio)sensors, which could improve the analytical features of b AA detection. Furthermore, investigating the prospects of increasing the accuracy, the sensitivity, the selectivity, the simplicity as well as minimizing the cost and toxicity of present b AA analytical methods is also an innovative approach to an old need for the world clinical diagnostics and electrochemical (bio)sensor are suitable tools towards this direction. In Table 1 selected studies in electrochemical (bio)sensing MSUD and b AA are summarized.  
Meanwhile, greater analytical features are attained when electrochemical techniques are coupled with NPs. To that end, the great antifouling trait of NP electrodes is notably meaningful, considering that they are skilled to execute a considerable number of detections without the loss of their analytical features as has been disclosed by their valuable repeatability. This particular trait awards them respectable facilities to be practiced on the determination of biomarkers in real samples.  
Notwithstanding, the dominant challenge continues existing, when real samples are to be analyzed, due to problems related to reproducibility, stability, as well as interferences. These elements can be worked out by evolving innovative sensors built on chiral nanostructured components, favoring the selectivity of the determination. Admirable analytical enforcement may be brought about through the coupling of enzymes to NPs and electroactive arbiters.  
Conclusively, the captious prospects of the leading edge on the determination of b AAs, clearly launches innovative frontiers on electrochemical sensors for rapid monitoring of a disease, initiating modern concepts in diagnostics. A forthcoming advancement in electrochemical sensing may be the growth of implantable sensors for prolonged disease screening. Thus, novel (bio)materials must integrate into devices, achieving stability and limiting the infections with unwanted substances. Late determination methodologies, such as ultra-fast CV may be occupied for real-time b AA monitoring. The advancement of mercantile arrangements on b AA monitoring predicated on electrochemical (bio)sensors and chromatographic or electrophoretic techniques may be the next step in the field.  
S.K.; investigation, S.K.; writing--original draft preparation, S.K.; writing--review and editing, S.K.; visualization, S.K.; funding acquisition, S.K.; review S.G.; supervision. All authors have read and agreed to the published version of the manuscript.  
This research is co-financed by Greece and the European Union (European Social Fund--ESF) through the Operational Programme <<Human Resources Development, Education and Lifelong Learning>> in the context of the project \"Reinforcement of Postdoctoral Researchers--2 nd Cycle\" (MIS-5033021), implemented by the State Scholarships Foundation (IKY), grant number MIS 5033021.  
The authors declare no conflict of interest and the funders had no role in the design of the study; in the writing of the manuscript, or in the decision to publish this review.