Conjugation of Carbon Dots with β-Galactosidase Enzyme: Surface Chemistry and Use in Biosensing

Abstract

Nanoparticles have been conjugated to biological systems for numerous applications such as self-assembly, sensing, imaging, and therapy. Development of more reliable and robust biosensors that exhibit high response rate, increased detection limit, and enhanced useful lifetime is in high demand. We have developed a sensing platform by the conjugation of β-galactosidase, a crucial enzyme, with lab-synthesized gel-like carbon dots (CDs) which have high luminescence, photostability, and easy surface functionalization. We found that the conjugated enzyme exhibited higher stability towards temperature and pH changes in comparison to the native enzyme. This enriched property of the enzyme was distinctly used to develop a stable, reliable, robust biosensor. The detection limit of the biosensor was found to be 2.9 × 10−4 M, whereas its sensitivity was 0.81 µA·mmol−1·cm−2. Further, we used the Langmuir monolayer technique to understand the surface properties of the conjugated enzyme. It was found that the conjugate was highly stable at the air/subphase interface which additionally reinforces the suitability of the use of the conjugated enzyme for the biosensing applications.

Highly Sensitive Fluorescent Biosensor Based on Acetylcholinesterase and Carbon Dots–Graphene Oxide Quenching Test for Analytical and Commercial Organophosphate Pesticide Detection

“…In the same graph, we can see that the conjugated mixture of CD and AChE presents a higher peak at the same wavelength, due to the absorption of the amide bond whose presence has increased due to conjugation (Song and Zhang, 2019). The formation of an apparent new peak at 260 nm associated with the conjugation process is also observed, although the signal is noisy (Sharma et al, 2019). Regarding the fluorescence spectrum, for all the samples, a maximum emission peak was obtained at 420 with 320 nm as excitation value.…”

Recent Developments of Carbon Dots in Biosensing: A Review

“…Thus, CDs have been frequently used to design enzyme-involved electrochemical biosensors. For example, because a change in electrochemical signal is normally observed during redox reactions between oxidoreductase and its substrates, various CDs-derived biosensors have been designed to detect oxidoreductase substrates (i.e., glucose, , H 2 O 2 , and galactose). When an electrode containing an oxidase comes into contact with a substrate-containing solution, a redox reaction occurs on the interface of the electrode and is accompanied by transfer of electrons, resulting in a change in electrode current.…”

An Overview on Carbon Quantum Dots Optical and Chemical Features

“…Alternatively, CDs could be coupled with enzymes to monitor and guide their effects [ 144 , 145 ] on metal centers for high-field magnetic resonance analysis [ 146 ]. Interestingly, Zhou et al [ 147 ] coupled GQDs with gel-like CDs in order to magnify the drug loading ability, leaving the biocompatibility and mobility in all body districts untouched.…”