The Use of a Harmless Invisible Ink to Send Secret Messages on Nitrocellulose Membranes and as a Substitute for the Harmful Radioactive Ink Used as a Marker in ECL Membrane Assays

Abstract

AbstractThe use of invisible ink and the art of writing secret messages have been part of man’s fantasy for a long time and have proven useful in clandestine and high-sensitivity areas. Security inks having invisible materials provide important non-photocopiable-printed images that can be read only under special environments. An ink preparation based on silicon(IV) 2,3-naphthalocyanine bis(trihexylsilyloxide) as colorant, invisible to the naked eye, but infrared readable has been described previously. Biometric DNA ink has also been developed for security authentication. In a lighter vein, many budding scientists and others have often experimented with writing secret messages on paper, either for purposes of fun or actually sending secret messages to friends. Such a method involved lemon juice, milk, or other solutions that could be used with a dip pen, brush, or a fountain pen to write invisible messages on a blank white paper. Words turn up like magic as the paper is exposed to heat in one form or the other. This chapter attempts a slightly humorous proposition by showing that invisible messages can be written on nitrocellulose membranes (but not on polyvinylidene difluoride membranes) using an appropriately diluted horseradish peroxidase/alkaline phosphatase anti-IgG conjugate (rabbit, mouse, or human anti-IgG). Any message can be written on the membrane, preferably with a fountain pen, and the membrane is allowed to dry. One can unravel the messages magically using detection systems commonly used in western blotting – namely, detection with enhanced chemiluminescence plus or nitro blue tetrazolium/5-bromo-4-chloro-3-indolyl phosphate. Besides, one could use this method to mark nitrocellulose membranes for orientation purposes using ECL detection system and thus eliminate the use of pens containing the harmful radioactive ink.KeywordsNitrocellulose membraneSecret messageInvisible inkMolecular penECL detectionAutoradiography pens