Multifaceted Interaction Studies between Carbon Dots and Proteins of Clinical Importance for Optical Sensing Signals

Abstract

Carbon dots (CDs) are emerging as efficient optical probes. However, their application potential for clinical diagnosis has not been adequately explored. Herein, we examined the suitability of pyroglutamate CDs for detecting glucose, cholesterol, and alcohol in blood serum through their peroxidative activity in the respective enzyme-catalyzed reactions following fluorometric and colorimetric approaches. In buffer, the CD’s fluorescence intensity (λex 354nm) enhanced over 115% after interaction with the enzyme proteins due to different lifetime components on its surface. The enhancement was also linked to FRET with the proteins (λex 274nm for TRP/TYR). The electrostatic interactions, as revealed from the zeta potential study, generated binding energy (ΔG, kcal/mol) in the range of −5.8 to −6.3 and greatly shifted the protein’s secondary structure to β-strand contents. The CD’s fluorescence in the blood serum medium was also enhanced where serum’s particulate components contributed to the emission. All these subvert fluorescence emissions could be substantially cleaned for detection of peroxide generated in the enzymatic reaction by filtering the serum particulates and redox proteins prior to the addition of CDs to the reaction systems. The CD, however, could complement well in ABTS-based (absorbance at λmax 414nm) colorimetric reaction in blood serum without introducing protein or particle separation steps for sensitive detection of peroxide. The limit of detection, dynamic range, and sensitivity discerned for peroxide in the glucose oxidase-catalyzed reaction system were 183 μM, 0.02–0.10 mM (R 2 = 0.98), and 0.2482 AU mM–1, respectively. Overall, these findings will guide clinical application of the peroxidatic CDs to detect various analytes in blood serum following fluorometric- and colorimetric-based principles.

One‐Step Hydrothermal Synthesis of Boric Acid‐Functionalized Carbon Dots and their Applications in Glucose Sensing

“…Serum samples were diluted 500 times during the assay to effectively reduce interference from complex matrices. We learned that serum may affect the optical properties of CDs in related work [27] . For example, Smita Das et al.…”

“…We learned that serum may affect the optical properties of CDs in related work. [27] For example, Smita Das et al found the CDs' fluorescence in the blood serum medium was also enhanced where serum's particulate components contributed to the emission. When CDs were mixed with diluted serum, the fluorescence of CDs was significantly increased compared with that of CDs in the buffer system.…”

Insight into the Modulation of Carbon-Dot Optical Sensing Attributes through a Reduction Pathway

“…Nevertheless, a FL sensor renders much more flexibility in terms of simple instrumentation/operation, fast responses, multiple analyses, high sensitivity, and good selectivity with ample scopes to attune CDs as required. Furthermore, a wide range of cheaper sources with green synthesis routes such as hydrothermal methods have also been explored to date for making them more reliable in practical applications. , …”

“…Furthermore, a wide range of cheaper sources with green synthesis routes such as hydrothermal methods have also been explored to date for making them more reliable in practical applications. 31,32 Though many attempts have already been made for sensing of a range of contaminants including heavy metals by differently functionalized CDs, very few works particularize a detailed investigation of physicochemical attributes of CDs responsible for their heavy-metal sensing behavior. Herein, a deliberate attempt has been made to understand how reduction could affect the surface functionalities for tuning useful photophysical attributes to be used for the speciation of heavy metals (Co 2+ and Hg 2+ ) and their dual sensing at trace levels.…”

“…Furthermore, a wide range of cheaper sources with green synthesis routes such as hydrothermal methods have also been explored to date for making them more reliable in practical applications. 31 , 32 …”