Ratio type nanoprobe with boric acid as recognition unit for imaging intracellular HO with SERS.

Fluctuations of intracellular HO level are intricately linked to diverse biological processes, e.g., cellular proliferation, biosynthesis, and metabolic activities. The dynamics of intracellular HO levels holds immense significance as it represents a pivotal metabolite within the realm of free radicals. This study describes a novel internal standard assisted surface enhanced Raman scattering (SERS) nanoprobe based on HO boronic acid oxide group for precise detection of HO levels in vitro and within living cells. The nanoprobe consists of a core molecule shell Au nanostar (Au@MPBN@Au NPs) embedded with internal marker (4-mercaptobenzonitrile, 4-MPBN) as a high plasma active SERS substrate and a 4-mercaptophenylboronic acid (4-MPBA) molecule fixed on its surface as HO recognition unit. The presence of HO leads to a decrease of the band intensity for B-O group at 998 cm, while the absorption for the internal standard molecule 4-MPBN at 2223 cm remains unaffected by the variation of external environment. HO quantification may be achieved by analyzing the ratio of band intensities at I/I, with a linear relationship between I/I and HO concentration within the range of 5-100 μM, along with a limit of detection (LOD) of 1.97 μM. Meanwhile, due to the presence of internal marker molecules, measurement errors caused by environmental or instrumental fluctuations can be calibrated in real-time. The AuNPs/4-MPBN/4-MPBA nanoprobe provides an accurate tool for dynamic monitoring and quantitative characterization of intracellular HO content during cell apoptosis or other cell growth processes.