Sensing Methods of Immunosuppressant Drugs: Calcineurin Inhibitors and Purine Synthesis Inhibitor Agents

Today, immunosuppression is associated as a necessary protocol in renal posttransplantation follow-up to improve both patient and graft survival rates. Two typical classes of immunosuppressants that have been used in oral long-term medication are calcineurin inhibitors, cyclosporine A (CsA) and tacrolimus (TAC), and purine synthesis inhibitor agents, azathioprine (AZT) and mycophenolate mofetil (MMF). As a common feature for all of them, they have a narrow therapeutic index (TI) which may lead to toxicity or effectiveness of therapy in super therapeutic and subtherapeutic concentrations, respectively. So, despite the undisputed value of immunosuppressants, therapeutic drug monitoring (TDM) is a vital necessity for post-renal transplantation follow-up to maintain an appropriate balance between a predefined therapeutic dose and toxicity and the likelihood of adverse effects. Previously, most of the analytical methods that have been employed for immunosuppressant detection are based on immunoassay and chromatography methods. Both of these methods suffer from drawbacks such as expensiveness, time-consuming responding, lack of stability, and need of skilled persons to interpret obtained results which make them inappropriate platforms for in-situ applications. In this way, we need facile, fast responding analytical methods as like as optical and electrochemical sensors which can be developed to use in point-of-care (POC) applications. Here, we summarized the analytical methods for the determination of CsA, TAC, AZT, and MMF which are based on fast responding methods.