Fluorescence sensor for detecting protamines based on competitive interactions of polyacrylic acid modified with sodium 4-amino-1-naphthalenesulfonate with protamines and aminated graphene oxide

Abstract

An easy-to-use fluorescent probe for detecting protamines was developed. Protamines are detected using the probe because of competitive interactions of polyacrylic acid modified with sodium 4-amino-1-naphthalenesulfonate (ANS-PAA) with protamines and aminated graphene oxide (GO-NH₂). The ANS-PAA fluorescence was effectively quenched by the GO-NH₂, the high quenching efficiency being caused by the ANS-PAA becoming non-covalently bound to the GO-NH₂ surface through electrostatic interactions, forming a ANS-PAA/GO-NH₂ complex. Adding protamines recovered the fluorescence of the ANS-PAA/GO-NH₂ complex. This recovery was due to the positively charged protamines removing ANS-PAA from the GO-NH₂ surfaces and forming ANS-PAA/protamine complexes. Displacement of GO-NH₂ by protamines gave a high fluorescence recovery efficiency. Under optimal conditions, the fluorescence intensity when protamines were added was proportional to the protamine concentration over the range 0 to 6.0 μg mL⁻¹. The detection limit was 0.4 μg mL⁻¹. This approach offers a new quantitative method for determining protamines.