Visualization of Sweat Fingerprints on Various Surfaces Using a Conjugated Polyelectrolyte

Area of Science:

• Forensic Science
• Polymer Chemistry
• Analytical Chemistry

Background:

• Latent fingerprint (LFP) detection is crucial in forensic science.
• Existing LFP imaging methods often require complex treatments or lack sensitivity on diverse surfaces.
• Conjugated polyelectrolytes offer potential for sensitive and specific molecular detection.

Purpose of the Study:

• To investigate the utility of a conformation-variable conjugated polyelectrolyte, sulfonated poly(diphenylacetylene) (SPDPA), as a fluorescent imaging agent for LFPs.
• To evaluate the mechanism of fluorescence enhancement in SPDPA upon interaction with LFP components.
• To assess the effectiveness of SPDPA for LFP visualization on various surfaces.

Main Methods:

• SPDPA solution was used to wet target objects containing LFPs.
• Fluorescence imaging was employed to capture LFP images.
• Model reactions between SPDPA and amino acids were conducted to study fluorescence enhancement mechanisms.
• LFP visualization was tested on paper, glass, and plastic surfaces.

Main Results:

• SPDPA enabled high-resolution, "turn-on" fluorescence imaging of LFPs without additional treatments.
• Electrostatic interactions between SPDPA and LFP sweat components, particularly amino acids, significantly enhanced fluorescence.
• Effective LFP visualization was achieved on both rough (paper) and smooth (glass, plastic) surfaces.
• SPDPA demonstrated efficacy in detecting extremely thin LFPs, especially on smooth glass.

Conclusions:

• SPDPA is a promising fluorescent imaging agent for sensitive and high-resolution latent fingerprint detection.
• The "turn-on" fluorescence mechanism based on electrostatic interactions with sweat components offers a simple and effective detection strategy.
• SPDPA's versatility across different surfaces and its ability to detect faint prints highlight its potential in forensic applications.