The construction and application of a new PPY-MSPQC for l-asparaginase activity assay

There is a perceived need for a simple and real time sensor for NH3 detection which will function at both room temperature and high humidity to be compatible with biological applications. A new polypyrrole multi-channel series piezoelectric quartz crystal system (PPY-MSPQC) is proposed for this purpose. In this system, polypyrrole chemically deposited on the surface of polyimide was used as a probe instead of parallel electrodes. The probe can react with NH3, which causes an increase of electric impedance and results in frequency shift changes at both room temperature and high humidity. Compared with parallel electrode, the new probe has some advantages as follows: (1) the sensor can respond to a gas change and was not limited by the sensitive range of MSPQC; (2) using polyimide instead of metal electrode, the effect of metal corrosion in liquid medium was eliminated. The optimum conditions of probe prepared were discussed in detail. raginase can convert l-asparagine to l-aspartic acid and ammonia and induce remission in acute lymphoblastic leukemia (ALL). It was chosen as a model enzyme, the activity of which was detected using proposed system. The initial reaction rate had a linear relationship with the activity of l-asparaginase in the range of 0.01–0.10 U ml−1. The detection limit was 0.01 U ml−1. Compared with Nesslerization method, proposed method was simple, non-toxic and real time.