CHARACTERIZATION AND COMPARATIVE EVALUATION OF ANTIBACTERIAL AND CYTOTOXIC EFFICACY BETWEEN TWO QUERCETIN-AU-NANOCONJUGATES SYNTHESIZED USING PURE TRI-SODIUM CITRATE AND ITS NATURAL ALTERNATIVE - LEMON EXTRACT

Abstract

Green synthesis of AuNPs that have potential anticancer properties is relatively simple, cheap and eco-friendly compared to the conventional chemical/physical approaches. Quercetin is known for its antioxidant and anticancer properties, i.e., induction of apoptosis, tumour suppression, etc. This study aims to characterize and compare between two differentially synthesized Quercetin-Au-Nanoconjugates, Q-Au-NCTSC and Q-AU-NCLE using a pure biochemical reductant, trisodium citrate and its natural alternative, citrus lemon extract respectively. Antibacterial and anticancer effects of both the nanoconjugates would also be checked and compared to analyze whether the use of a lemon extract has any impact on its structure and functional properties. A series of physicochemical characterizations viz. UV-Vis spectrophotometry, DLS, Zeta Potential, FT-IR, and SEM of the nanoconjugates were done. Further, evaluation of in vitro antibacterial activity was done against two Gram-positive bacteria: Staphylococcus aureus; Bacillus Subtilis; and two Gram-negative bacteria: Pseudomonas aeruginosa; Klebsiella pneumonia and cytotoxicity efficacy were checked on breast cancer (MCF7) cell line. Effective reduction of Au+3 to Au0 with quantum confinement in nano-regime was confirmed by a change of bulk colour of the HAu+3Cl4 solution, whereas conjugation of Quercetin to AuNPs was confirmed by FTIR. DLS showed the average size of the Q-Au-NCTSC and Q-Au-NCLE are 30 nm and 35.6 nm, respectively. The Q-Au-NCLE has shown comparatively better stability and antibacterial activity. In the case of cytotoxicity study on MCF7 cell line, the Q-Au-NCLE showed better efficacy (cell death ~ 75%) with respect to Q-Au-NCTSC (cell death ~66%). Natural sources rich in citric acid would serve as the best alternative to tri-sodium citrate in the synthesis of Au-NPs and different nanoconjugates for biomedical applications.