Peptide-coated palladium nanoparticle for highly sensitive bioanalysis of trypsin in human urine samples

In recent years, palladium nanoparticles have been proved as energy acceptor candidates in fluorescence resonance energy transfer-based sensors for analytical and biological purposes. In this article, peptide-coated palladium nanoparticles were prepared using a simple one-step preparation method. The peptide Cys-Ala-Leu-Asn-Asn was used as a ligand, whereas hydrazine hydrate was used as a reductant to obtain water-soluble and stable peptide-coated palladium nanoparticles. Additionally, peptide-coated palladium nanoparticles were functionalized by adding the functional peptide CALNNGGARK(FITC) in combination with Cys-Ala-Leu-Asn-Asn during the preparation process. The prepared functionalized peptide-coated palladium nanoparticles were used for trypsin detection based on the fluorescence resonance energy transfer approach. Under optimized conditions, the proposed method can be used for the detection of trypsin concentrations in the range of approximately 0.2–8-μg/mL with a limit of detection of 0.18-μg/mL. The functionalized peptide-coated palladium nanoparticles were successfully applied for the detection of trypsin in urine samples. Our findings also indicated that peptide-coated palladium nanoparticles can highly quench fluorophores and are suitable for the manufacture of off–on state fluorescent sensors. We anticipated that the peptide-coated palladium nanoparticles proposed in this article will have great potential for the detection of trypsin in urine and other analytical, biological, and clinical applications.