Blown spun fibers-based colorimetric sensor for detecting trace zinc in seminal fluid

Rapid and accurate analysis of zinc in seminal fluid is an important tool for male infertility diagnosis and forensic investigation of sexual assault. Among the traditional techniques employed for this purpose, colorimetric solid-state sensors offer a simple and efficient alternative for screening this analyte. Herein, we evaluated the feasibility of using solution blow spinning as a fast, simple, and cost-effective method to develop porous membranes that can be manufactured as low-cost colorimetric solid-state sensing materials. Specifically, we report a one-step approach to prepare blown spun polylactic acid (PLA)/poly(ethylene oxide) (PEO) fibrous membranes modified with 1-(2-pyridylazo)-2-naphthol (PAN) for the quantitative and qualitative screening of Zn²⁺ in human seminal fluid. The fibrous membranes were fully characterized and then used to prepare discs and swabs. By digital image colorimetry, a spot-like assay was established using PLA/PEO@PAN membrane discs, which under optimized conditions, exhibited a linear range of up to 15 mg L^-1, a limit of detection of 0.06 mg L^-1 and high selectivity in the presence of several interfering species commonly found in seminal fluid. Additionally, the sensor was successfully applied in the detection of Zn²⁺ in human semen samples, showing no significant differences compared to the standard method. Furthermore, PLA/PEO@PAN swabs were employed in a naked-eye presumptive test to identify semen stains, showing satisfactory visual response even in the presence of only 0.11 μg of zinc. Moreover, the swabs' color changes were highly unambiguous, revealing a concordance rate of almost 90% in a blind study. This outstanding performance can be ascribed to the high porosity and wettability of the fibrous membrane and the PAN's coordination ability towards Zn²⁺. Overall, the remarkable advantages achieved with our approach lie in the easy production, on-site, and cost-effective analysis of zinc as a biomarker for clinical and forensic applications.