304. DEVELOPMENT OF KEY COMPONENTS IN A SMALL, PORTABLE DEVICE FOR THE THERAPEUTIC MONITORING OF LITHIUM

Abstract Background Lithium pharmacotherapy is an effective, first line treatment for bipolar disorder and included in the WHO list of essential medicines. However, it is underutilised because it has a narrow therapeutic window and requires therapeutic drug monitoring (TDM) to establish and maintain a safe dose. Lithium TDM requires patients to attend a pathology clinic for a blood draw with results available to clinicians after 24 hours or longer. From the consumer perspective, little has changed in the experience of lithium TDM for decades. Recent technological advances suggest that it should be feasible to develop a small portable device that can provide rapid blood lithium results without the burden and stigma of attending a pathology laboratory. Rapid blood lithium results at the point of care will allow to check results and if necessary, adjust the dosage during a single consultation. Aims & Objectives To present the results to date for the development of the basic components of a small device to the TDM of lithium. These components are (i) the biosensor, that interfaces between the biological matrix that is being measured for lithium concentration (usually whole blood) and produces a measurable signal that is proportional to the lithium concentration, and (ii) the electronic components that transpose the signal from the biosensor into a numerical measure of blood concentration that can be read of a display. Method (i) Electrochemical impedance spectroscopy was explored as a method for detecting and measuring lithium ions. A conductive system of carbon conductive ink as the working electrode and counter electrode and an Ag ink as reference electrode was modified with lithium salts in acetonitrile. (ii) A printed circuit board was adapted from an existing design, including potentiostat and Bluetooth capability. Results (i) The working electrode was modified with a suspension of LiMn2O4 in Acetonitrile (15g/kg). Cyclic voltammetry was conducted in KCl and LiNO3 solutions. (ii) A printed circuit board was produced, and testing has demonstrated that a signal can be displayed on a computer. Discussion & Conclusions Key components of a small portable device for the TDM of lithium have been developed. The components need to be tested and optimised for performance parameters of accuracy, precision, specificity and sensitivity. An assembled prototype device needs to be manufactured, and field tested.