A comprehensive review of methods for determination of l-lysine with detailed description of biosensors.

l-lysine being one of the essential amino acids is not produced by the body, but is obtained through diet. l-lysine determination is important in the food and pharmaceutical industries as well as have medical and diagnostic applications. The normal l-lysine levels in a healthy human serum sample is 150 to 250 μmol/l. There is imbalance in l-lysine levels in certain diseased conditions. So, it could be a biomarker for diagnosis. Various basic methods are available for the determination of l-lysine such as colorimetric, radioisotope dilution, chromatographic, fluorometric and voltammetric methods. These methods have certain disadvantages like sample pretreatment, costly, time consuming and requirement of skilled personnel. These drawbacks are overcome by the use of biosensors due to their high sensitivity, stability and specificity. The present review article discusses about the principles, merits and demerits of the various analytic methods for determination of l-lysine with special emphasis on biosensors. l-lysine biosensors work ideally under the optimum pH 5 to 10, potential range -0.05 to 1.5 V, temperature 25 to 40 °C, with linear range 0.01 to 5500 μM, detection limit 0.000004 to 650 μM and response time 2 to 300 s. The sensor had storage stability between 14 and 200 days.