Novel fingermark detection methods using biomolecular recognition

University of Technology Sydney. Faculty of Science.Over the past decade, there has been a resurgence of interest to design fingermark enhancement reagents capable of biomolecular recognition; such reagents would offer high selectivity and sensitivity, two areas where some believe improvement is desired with current fingermark detection methods. In addition to these, a high degree of adaptability for visualisation can be achieved with biomolecular recognition probes, such as antibodies and aptamers, allowing for the selection of the most appropriate visualisation wavelength for a particular luminescent probe or substrate without the need for sophisticated instrumentation or imaging systems. However, the major hurdle to overcome is the balance between sensitivity and selectivity. Single-target biomolecular recognition may be highly selective, purported to have better detection limits than chemical reactions or stains, and can provide information about identity and/or activity, but often results in incomplete ridge pattern development because only a fraction of the fingermark residue is being specifically targeted. Consequently, the development and evaluation of multi-target biomolecular reagents for fingermark enhancement was investigated, with the focus on endogenous eccrine secretions. A variety of parameters (i.e., processing time, fixing and working solution conditions) were optimised on a wide range of non-porous and semi-porous substrates representative of casework materials to assess the suitability of the biomolecular reagents for potential operational use. The relative performance of biomolecular reagents was compared to that of routine methods applied to latent and body fluid-contaminated fingermarks. The incorporation of these novel reagents into routine technique sequences was also investigated. The experimental results indicated that the multi-target biomolecular reagents were not a suitable alternative to routine detection methods, did not provide any significant enhancement when included in routine sequences; however, they may still have potential for a niche application yet to be identified. While a larger fraction of the fingermark was being targeted by multi-target reagents, the resulting development seemed to be influenced by inter-donor variability; it was unknown which combination of biomolecular recognition probes would be the most “universal”. The focus of this research shifted to aptamers due to their many advantageous features over antibodies, one being their versatile in vitro selection process called Systematic Evolution of Ligands by EXponential enrichment or SELEX. Up to sixteen fingermark donors deposited variously aged natural fingermarks onto two realistic substrates (i.e., pooled target approach), which were then subjected to a novel SELEX variation termed fingermark-SELEX. Select DNA aptamer candidates, developed specifically against genuine fingermark residues, were subsequently incorporated into a fingermark enhancement reagent. The proof-of-concept work demonstrated this novel reagent’s ability to successfully develop friction ridge detail on non-porous substrates. Its relative performance was superior to that of single-target and multi-target biomolecular reagents previously designed within the same research group. This study has further opened up the possibilities of incorporating biomolecular recognition into fingermark detection methods by recognising and tapping into the potential of SELEX and resulting aptamer candidates in this forensic discipline