N, S-Doped Carbon Dots Prepared by Peanut Protein Isolates and Cysteamine as Highly Sensitive Fluorescent Sensors for Fe2+, Fe3+ and Lactoferrin

Abstract

Lactoferrin (LF) is an iron-binding glycoprotein with various biological activities that has been extensively used in food and medical applications. Several methods for detecting LF have been reported, but they still face challenges in terms of sensitivity and simplicity of detection. To achieve an accurate and efficient detection of LF, we developed a method for the determination of LF in lactoferrin supplements using carbon dots (CDs) fluorescent probes. The N, S-doped PPI carbon dots (N, S-PPI-CDs) were prepared using a protein (peanut protein isolate) and cysteamine as precursors. The prepared N, S-PPI-CDs exhibited intense blue fluorescence and good biocompatibility, while the fluorescence intensity of the N, S-PPI-CDs showed a good linear relationship with Fe2+/Fe3+ concentration (0–2 μM). The N, S-PPI-CDs exhibited a high potential ability to rapidly detect Fe2+/Fe3+ within 30 s, with a limit of detection (LoD) of 0.21 μM/0.17 μM. Due to the reversible binding of LF to Fe, the N, S-PPI-CDs showed a high sensitivity and selectivity for LF, with a limit of detection (LoD) of 1.92 μg/mL. In addition, LF was quantified in real sample LF supplements and showed a fluctuation in recovery of less than 2.48%, further demonstrating the effectiveness of the fluorescent N, S-PPI-CDs sensor.

Folic Acid Adjustive Polydopamine Organic Nanoparticles Based Fluorescent Probe for the Selective Detection of Mercury Ions

“…For all we know that the N/C value of FA is 0.43, and the N/C value ranges of PDA is often from 0.08 to 0.17, interestingly, the N/C value of FA-PDA FONs here is 0.226, therefore, FA-PDA FONs may be hybrid materials and composed of folic acid, polydopamine, even Tris moieties [37]. As represented in Figure 3b, the C1s region can be integrated into four major component bands: C-C/C=C (284.82 eV), C-N/C-O (286.23 eV), C-C=O (287.70 eV), and C=N (288.63 eV) [5,38], correspondingly. In addition, the N1s region has three bands: C=N-R (398.6 eV), R 1 -NH-R 2 (399.06 eV), and R-NH 2 (401.87 eV), respectively [32], and the O1s region is fitted with two prominent bands: O-C (532.9 eV) and O=C (531.85 eV) [12,32].…”

“…Fluorescent organic nanoparticles (FONs) have attracted extensive interest in many fields, owing to their excellent optical property, diffusion capability, biocompatibility and photostability, which gives them potential for application in fields such as sensing and bioimaging. [1][2][3][4][5]. Polydopamine (PDA) based organic nanomaterials have received lots of attention due to their excellent biocompatibility, strong adhesive properties, being easy to prepare, metal ion chelating, and chemical reactivity, among other properties [6][7][8][9][10].…”