Quantitative Assessment of Copper(II) in Wilson's Disease Based on Photoacoustic Imaging and Ratiometric Surface-Enhanced Raman Scattering.

Cu is closely related to the occurrence and development of Wilson's disease (WD), and quantitative detection of various copper indicators (especially liver Cu and urinary Cu) is the key step for the early diagnosis of WD in the clinic. However, the clinic Cu detection approach was mainly based on testing the liver tissue through combined invasive liver biopsy and the ICP-MS method, which is painful for the patient and limited in determining WD status in real-time. Herein, we rationally designed a type of Cu-activated nanoprobe based on nanogapped gold nanoparticles (AuNNP) and poly(-isopropylacrylamide) (PNIPAM) to simultaneously quantify the liver Cu content and urinary Cu in WD by photoacoustic (PA) imaging and ratiometric surface-enhanced Raman scattering (SERS), respectively. In the nanoprobe, one Raman molecule of 2-naphthylthiol (NAT) was placed in the nanogap of AuNNP. PNIPAM and the other Raman molecule mercaptobenzonitrile (MBN) were coated on the AuNNP surface, named AuNNP-NAT@MBN/PNIPAM. Cu can efficiently coordinate with the chelator PNIPAM and lead to aggregation of the nanoprobe, resulting in the absorption red-shift and increased PA performance of the nanoprobe in the NIR-II window. Meanwhile, the SERS signal at 2223 cm of MBN is amplified, while the SERS signal at 1378 cm of NAT remains stable, generating a ratiometric SERS / signal. Both NIR-II PA and SERS / signals of the nanoprobe show a linear relationship with the concentration of Cu. The nanoprobe was successfully applied for quantitative detection of liver Cu of WD mice through NIR-II PA imaging and accurate quantification of urinary Cu of WD patients by ratiometric SERS. We anticipate that the activatable nanoprobe might be applied for assisting an early, precise diagnosis of WD in the clinic in the future.