Cobalt Polypyridyl Complexes as Redox Mediators for Lipoamide Dehydrogenase

✍ Scribed by Carmen M. Colón; Ana R. Guadalupe

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 168 KB
• Volume: 10
• Category: Article
• ISSN: 1040-0397
• DOI: 10.1002/(sici)1521-4109(199807)10:9<621::aid-elan621>3.0.co;2-m

✦ Synopsis

A series of cobalt polypyridyl complexes were synthesized and characterized by cyclic voltammetry in aqueous and acetonitrile solutions. Their mediation ability toward FADH 2 oxidation in a monoenzyme (lipoamide dehydrogenase) and a bienzyme (lipoamide dehydrogenase coupled to lactate dehydrogenase) system was studied. Of all the complexes tested, only the [Co(tpy) 2 ](PF 6 ) 2 , [Co(NH 2 -phen) 3 ](PF 6 ) 2 and [Co(CH 3phen) 3 ](PF 6 ) 2 showed a current enhancement indicative of an EC cat mechanism in the presence of lipoamide dehydrogenase and NADH. No cross reactivity was observed for these complexes in the presence of lactate dehydrogenase/ NAD þ and lactate. The results also suggest that factors such as hydrophobic interactions, steric hindrance, H-bonding and driving force are important when designing a redox mediator for a biosensor. Protein and/or cofactor adsorption fouled the electrode surface lowering the current response. A self-contained bienzymatic biosensor exhibited a linear response (peak current versus log [lactate]) for lactate concentrations between 5 M to 5 mM with a lowest detectable lactate concentration of 4.76 M.