Considering the significant evidential values of fingerprints in underwater criminal investigations and the need to visualise them using a user- and environmentally-friendly reagent, development of a novel, rapid and relatively greener nanobio-based reagent (NBR) is deemed beneficial. Lipase from the commercial Candida rugosa immobilised onto acid-functionalised multi-walled carbon nanotubes (NBR) was used as the safer and cheap lipid-sensing reagent to visualise groomed whole/split fingerprints on non-porous objects immersed in stagnant tap water for up to 30 days under a laboratory-controlled setting. Attenuated Total Reflectance - Fourier Transform Spectrometry, Field Emission Scanning Electron Microscopy and bioinformatics (molecular docking and molecular dynamics simulations) were employed to characterise and confirm the attachment of NBR onto the lipid constituents of wet fingerprints. Chromatographic results further confirmed the presence of n-hex-adecanoic and octadecanoic acids on fingerprints up to 30 days of immersion. Thus, NBR may potentially be useful as the future state-of-the-art fingerprint visualisation technology.

Evidences of crime are often disposed in waterways to destroy all ties to the crime. Nonetheless, these evidences are not inevitably lost as the water insoluble lipid components may remain on the object. Currently, Small Particle Reagent (SPR) is used for visualizing such wet fingerprints and it comprises of several chemicals that are relatively hazardous to the crime investigator and the environment. The adaptation of a greener nano-biotechnological route might be useful, but there is still much to be done to improve this fingerprint visualisation method. Henceforth, this study was carried out to optimise the visualization protocol for CRL-MWCNTs/GA/I3K/SAF on split natural fingerprints immersed in purified tap water for one-and 15 days using response surface methodology (RSM). The addition of I3K as the mordant expedited the overall staining process. This study achieved a better mean fingerprints quality for the one-day immersed samples fared better compared to 15 days, thus suggesting the adequate use of CRL in the formulation. Hence, it was shown that RSM is reliable in predicting the optimum condition that yielded the highest mean fingerprint quality for both time intervals (one and 15 days).