26 November 2010
An enzyme printing process that prints the product of an enzyme-catalysed reaction, but not the enzyme molecule itself, has been designed by scientists in Australia to produce bioactive paper.
Taking their inspiration from traditional printing methods such as ink jet and thermal contact printing, Wei Shen and colleagues from Monash University, Australia, have used relief and planographic printing methods to print the product of a reaction catalysed by an enzyme, in this case horseradish peroxidise (HRP).
Most current enzyme printing techniques use an 'ink' that contains the enzyme for biosensing. The problem with this method is that when the enzyme is transferred from the printer to the paper in the ink, it is difficult to recover the enzyme and reuse it. The enzyme may also interfere with any further reactions that occur on the paper.
A pattern of a cat's head was digitally generated and an ink jet printer was used to print a solution of horseradish peroxidase onto a nitrocellulose film
One technique developed by Shen to avoid the movement of the enzyme molecules involves the immobilisation of HRP on a nitrocellulose film to form the printing plate. They then coat paper with a liquid substrate that changes colour on contact with HRP. When the printing plate is pressed against the paper, the biochemical reaction makes the paper change colour at the point of contact.
Another technique investigated involves the use of an ink jet printer to make a digitally-generated enzyme pattern on a flat printing plate. When this plate is placed in contact with paper, the different surface chemistries of the plate generate an image.
By simply printing the reaction, and not the molecule, Shen has developed methods that can be reused for as long as the enzyme remains active.
Brian Derby, a specialist in biomaterials from the University of Manchester, UK, felt that the authors 'demonstrate the flexibility of their approach by using non-contact printing (ink jet) to pattern their printing plate' and comments, 'this is a very clever piece of lateral thinking'.
This kind of printing has many practical uses. 'It has potential applications in novel packaging materials, low-cost diagnostics, food safety, anti-counterfeiting, and pathogen detection using bioactive papers,' explains Shen. Research into developing these applications is currently underway.