Biomimetic-mineralized bifunctional nanoflowers for enzyme-free and colorimetric immunological detection of protein biomarker.

Detection of protein biomarkers relies largely on the development of modern immunological methods. Herein, a new enzyme-free immunological method is proposed to detect protein biomarkers. Employment of antibody-Cu3(PO4)2 hybrid nanoflowers, which are prepared through a facile and mild biomimetic-mineralizing process, is the core concept of the method. These nanoflowers can perform functions: one is to bind to target protein biomarkers with high specificity; the other is to release large amounts of Cu2+ upon acid treatment, which can interact with creatinine and exert peroxidase-mimicking enzyme activity, therefore producing a distinctly amplified signal. Using osteocalcin, a well-known circulating protein biomarker for bone formation, as a model, the method affords a linear range from 0.1 to 50 ng/mL with a detection limit of 0.042 ng/mL, which is superior to reported methods. Moreover, the method shows considerable specificity, desirable performance in serum samples and eliminates the use of enzymes, so a great potential for this method is expected to meet the need of the clinical diagnosis.