Researchers in Canada are using a bioorganometallic approach to detect HIV-1 protease, an essential enzyme in the assembly and activity of the HIV virus and key AIDS drug target.

A protease is an enzyme that cleaves proteins into their component peptides. HIV-1 protease (HIV-1 PR) hydrolyzes viral polyprotein precursors into individual mature proteins, which are essential for the development of the infectious form of the HIV virus. Due to the key role that HIV-1 PR plays in the lifecycle of HIV, it has become a key therapeutic target in tackling AIDS.

Up until now, electrochemical detection of unlabelled non-redox active proteins, such as HIV-1 PR, had remained a challenge to analytical chemists. However, Heinz-Bernhard Kraatz and colleagues at the University of Saskatchewan, Saskatoon, have developed a new electrochemical biosensor, detecting HIV-1 PR for the first time using a bioorganometallic approach.

Kraatz' biosensor is made up of pepstatin, a peptide known to bind to and inhibit HIV-1 protease, and ferrocene. This iron-containing group acts as the electrochemical sensor due to its well-known redox activity. The biosensing molecule is also readily attached to a gold electrode surface allowing the electrochemical response of the ferrocene centres to be monitored, in the presence of varying amounts of HIV-1 PR. Increased concentrations of HIV-1 PR means that the oxidation of the ferrocene groups becomes more difficult. This change in electrochemical response can then be used as a measure of the quantity of HIV-1 protease present.

Kraatz and co-workers also wanted to see whether this new electrochemical sensor could work in biological conditions, where a mixture of many other proteins could interfere with the sensor. The biosensor was tested in the presence of human serum albumin, a protein present in blood at high concentrations. Encouragingly Kraatz found that the electrochemical changes were only observed when HIV-1 PR was present, showing the specificity of this new method, which 'demonstrates proof-of-concept of our electrochemical approach', according to the team.

While Kraatz and co-workers admit these results are preliminary, they hope to see their approach being adopted in the future. 'Our electrochemical method provides an easy-to-use and low-cost alternative to the existing technologies. Especially, during the screening of hundreds of candidate drug molecules, a high-throughput and low-cost method would be very beneficial for pharmaceutical companies,' he said.

May Copsey