Chitosan has been widely used in the preparation of microparticles for drug delivery; however, it has not been considered in forensic applications. Tripolyphosphate- (TPP-) chitosan microparticles were formed using ionotropic gelation in the presence of a coloured dye and deposited onto latent fingerprints enabling fingerprint identification. 1. Introduction Chitosan is the generic name for a family of strongly polycationic derivatives of poly-N-acetyl-D-glucosamine (chitin) extracted from the shells of crustaceans or from the mycelia of fungi [1]. In chitosan the N-acetyl group is replaced either fully or partially by NH2, and therefore the degree of acetylation can vary from DA = 0 (fully deacetylated) to DA = 1 (fully acetylated, i.e., chitin). The long carbon chains of chitosan molecules render them lipophilic. Furthermore, chitosan is the second most abundant polymer on earth (after cellulose) and it is the only known naturally occurring polycationic polysaccharide; therefore, chitosan and its derivatives, including microparticles, have received a great deal of attention from the food, cosmetic, and pharmaceutical industries [2–4]. Microparticles can be prepared by the electrostatic interaction and the resultant ionotropic gelation between chitosan and the tripolyphosphate (TPP) (Figure 1) polyanion [2–4]. Size can be controlled by varying the chitosan？？: TPP ratio, pH, and the molar mass of the chitosan. Figure 1: Formation of the tripolyphosphate-chitosan complex by ionotropic gelation [ 4, 5]. Fingerprint detection is probably the oldest and most common method of identification used in forensic science. Fingerprints, therefore, present a perfect method for personal recognition; they are traces of an impression from the friction ridges on a person’s fingertips. Fingerprinting is used in the tracking and identification of criminals, and because they are unique (identical twins have different fingerprints), fingerprints can provide a clear and positive proof of identity. Recently, there has been great interest in the use of nanotechnology in the design of novel fingerprint detection systems. This is due to the fact that microparticles can provide improved latent fingerprint detection by using dye-functionalized microparticles (the dye or fluorophore may also be encapsulated within the microparticle) which can therefore provide an opportunity for improved visualisation. In this study, TPP-chitosan microparticles (loaded with red dye for visualisation purposes) have been used to attach to the lipid residues present in the latent fingerprint. In
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