Investigation of bioconjugation between CdTe@cys quantum-dot and BSA, Trypsin and Cytochrome c proteins applying PARAFAC on fluorescence data

Quantum dots (QDs) have gained a lot of attention in the past decade. The quantum confinement of their electronic states makes them quite attractive, showing some unique optical properties such as high quantum yield, symmetrical emission spectra, broad-band excitation, photostability, and readily tunable spectra 1, compared to conventional dyes. QDs and their molecular conjugates are becoming increasingly important for a wide range of applications in biotechnology, and medicine[ 2]. The water soluble cysteine functionalized CdTe@cys quantum dots were synthesized. The three-way data array was recorded by measuring excitation emission matrix (EEM) 3, during the covalent interaction between CdTe@cys QDs and BSA, Trypsin and Cytochrome c proteins using different cross-inkers such as: Formaldehyde, glutaraldehyde (G) and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC)/Nhydroxysuccinimide (NHS). Multiway analysis was performed to analyze the resulting data. The PARAFAC model 4, is useful for the identification of pure components spectra and leads to estimation of concentration and pure spectral profiles of components in the considered bioconjugation system3. PARAFAC showed two, three and three components when using formaldehyde, EDC/NHS and G cross linkers in this bioconjugate systems. Third component was present for this biconjugation systems when using EDC/NHS and G cross linkers, with a distinctly different location and emission intensity compared to CdTe@cys and proteins. Although new very strong florescent peaks 5, appeared after addition of G cross linker, for CdTe@cys and three proteins. This was further proof that the QDs and three proteins were covalent conjugated successfully. The new peak obtained from bioconjugated component can be used for improving sensitivity and limit of detection analysis of proteins. Therefore, we using spectroscopic data and multiway analysis, as a simple method, low cost, fast and efficiency for determination correct number of component in CdTe@cys with BSA, Trypsin and Cytochrome c, and improve detection proteins. This work ability to extend to similar systems by different QDs and proteins. The improvement in the latter could lead to an increase in applications of the QDs such as in fluorescence imaging and other biological applications such as pathogen and toxin detection [6].