Ratiometric SERS imaging for indication of peroxynitrite fluctuations in diabetic wound healing process

Peroxynitrite (ONOO−) involves in diabetic wounds and its concentration is fluctuated in different pathological stages during the wound healing process. Thus, ONOO− may be utilized as a powerful biomarker to indicate the healing process of diabetic wound. However, the pathological roles of ONOO− can’t be fully understood yet. Herein, inspired by the mechanism that phenylboronic pinacol ester can react with ONOO− specifically, we report a new kind of SERS nanoprobes to monitor ONOO− fluctuation during diabetic wound healing process. The gold-silver (Au@Ag) core-ultrathin shell nanoparticles were utilized as active substrate and conjugated with phenylboronic pinacol ester molecules on the surface of Ag shell to simultaneously act as Raman reporter molecules and recognition moiety of ONOO−. In addition, functional polyethylene glycol (HS-PEG) and bovine serum albumin layers were sequentially immobilized on the surface of Ag shell to improve the stability of the nanoprobes. In the presence of ONOO−, phenylboronic pinacol ester could be converted into the corresponding phenol, inducing the SERS signal changes. The concentration fluctuation of ONOO− could be quantitatively detected through the SERS signal intensity ratio (1076 cm−1/998 cm−1) changes of typical peaks. The nanoprobes exhibited a wide response range from 0 to 75 μM with 0.12 μM as the detection limit. In the diabetic wound skin models, ONOO− concentration fluctuations during the wound healing process before and after drug treatment could be obtained by SERS imaging. We expect the proposed SERS imaging assay could be a noninvasive and powerful tool to monitor the diabetic wound healing.