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Bifunctional peptide-mediated partitioning controls gold nanoparticle assembly for colorimetric detection of polystyrene nanoplastics
Summary
Scientists have developed a quick color-changing test that can detect tiny plastic particles (nanoplastics) in liquid within just 3-5 minutes, using a special protein that reacts differently depending on whether these plastics are present. This matters because nanoplastics are so small they've been hard and expensive to detect using current lab equipment, yet they're increasingly recognized as a potential health concern—so a fast, simple test like this could make it much easier to monitor our exposure to plastic pollution in water and other products.
Colorimetric detection using gold nanoparticles (AuNPs) has emerged as a simple and rapid molecular sensing approach. Growing environmental concerns regarding nanoplastics (<100 nm), which pose risks to human health and ecosystems, have intensified interest in developing effective detection methods. Owing to their extremely small size, nanoplastic detection has conventionally relied on expensive benchtop analytical instruments, underscoring the need for rapid and simple, on-site detection methods. In this study, we screened a library of over 1,000 AuNP-binding peptides using peptide array and identified several bifunctional peptide sequences that bind polystyrene nanoparticles (PSNPs, 50 nm) and AuNPs (25 nm). Among these, peptide GWWARTLSKR, which exhibited the strongest binding affinity toward PSNPs, produced a blue-colored solution in the absence of PSNPs owing to AuNP aggregation; in the presence of PSNPs, the AuNPs remained dispersed and retained a red color. This behavior can be explained by peptide partitioning between PSNPs and AuNPs, where preferential binding to PSNPs reduces peptide availability for AuNP aggregation, enabling aggregation-dispersion transitions for signal generation. In contrast, AuNP aggregation was observed in the presence of other nanoparticles, demonstrating the high selectivity of this system for PSNPs. PSNPs were detected within 3–5 min because the use of free peptides enhanced diffusion and increased collision frequency with PSNPs. The detection limit was 0.033 mg/mL and quantitative capability (R² = 0.95). To our knowledge, this is the first report of colorimetric PSNP detection using bifunctional peptides, and the peptide array-based strategy provides a versatile platform for designing probes for other environmental pollutants.