Development of an implantable d-serine biosensor for in vivo monitoring using mammalian d-amino acid oxidase on a poly ( o-phenylenediamine) and Nafion-modified platinum–iridium disk electrode

• Published in: Biosensors & bioelectronics 2010-02, Vol.25 (6), p.1454-1459
• Main Authors: Zain, Zainiharyati M., O’Neill, Robert D., Lowry, John P., Pierce, Kenneth W., Tricklebank, Mark, Dewa, Aidiahmad, Ghani, Sulaiman Ab
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biosensors; Biotechnology; Conductometry - instrumentation; Corpus Striatum - metabolism; d-amino acid oxidase; D-Amino-Acid Oxidase - chemistry; d-serine; Electrodes, Implanted; Enzymes, Immobilized - chemistry; Fluorocarbon Polymers - chemistry; Fundamental and applied biological sciences. Psychology; Humans; Implantable; Iridium - chemistry; Male; Methods. Procedures. Technologies; Microbiosensor; Neurochemical monitoring; Phenylenediamines - chemistry; Platinum - chemistry; Prostheses and Implants; Rats; Rats, Sprague-Dawley; Serine - analysis; Serine - metabolism; Various methods and equipments
• ISSN: 0956-5663; 1873-4235
• DOI: 10.1016/j.bios.2009.10.049

d-serine has been implicated as a brain messenger, promoting not only neuronal signalling but also synaptic plasticity. Thus, a sensitive tool for d-serine monitoring in brain is required to understand the mechanisms of d-serine release from glia cells. A biosensor for direct fixed potential amperometric monitoring of d-serine incorporating mammalian d-amino acid oxidase (DAAO) immobilized on a Nafion coated poly- ortho-phenylenediamine (PPD) modified Pt–Ir disk electrode was therefore developed. The combined layers of PPD and Nafion enhanced the enzyme activity and biosensor efficiency by ∼2-fold compared with each individual layer. A steady state response time ( t 90%) of 0.7 ± 0.1 s ( n = 8) and limit of detection 20 ± 1 nM ( n = 8) were obtained. Cylindrical geometry showed lower sensitivity compared to disk geometry (61 ± 7 μA cm −2 mM −1, ( n = 4), R 2 = 0.999). Interference by ascorbic acid (AA), the main interference species in the central nervous system and other neurochemical electroactive molecules was negligible. Implantation of the electrode and microinjection of d-serine into rat brain striatal extracellular fluid demonstrated that the electrode was capable of detecting d-serine in brain tissue in vivo.