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Bank notes can spread diseases from one person to another, or could even be
deliberately contaminated by terrorists. So Textile Biocides of Philadelphia has
filed a world patent to address the problem (WO 99/42658). Its answer is to dose
the linen and cotton fibres of a note with polyhexamethylene biguanide, an
ingredient of contact lens cleaning solutions. The chemical is added to the mix
used to treat the note’s surface, where it will kill microorganisms, or at least
inhibit their growth. A bonus is that the treatment helps notes survive
laundering.