SYNTHESIS OF CHITOSAN NANOPARTICLES AND CARBON NAN000TS FOR POTENTIAL BIO-APPLICATIONS

Abstract

The addition of carbon dots (C-dots) into the category of fluorescent nanomaterials has been relatively new, but the preliminary findings indicate a perceptible impact on various bioapplications. Interestingly, the multicolour fluorescence feature of C-dots has implications in the field of biolabeling. Herein, we report a one-step method for synthesizing multicolour, surface passivated carbon dots (CPs) using chitosan as a 'greener' source through microwave pyrolysis approach. In our study, surface passivation with PEG-4000 played a key role in synthesizing C-dots with superior photoluminescent properties. These CPs were further characterized by transmission electron microscopy (TEM), field emission-scanning electron microscope (FE-SEM) and X-ray diffraction (XRD) to ascertain their size, morphology and phase behaviour. The mechanism of formation of fluorescent carbon nanorods from CPs was also explored .The morphological changes in CPs were investigated through microscopic and spectral analysis. As a consequence of inhomogeneity in the emission wavelength peak of CPs, they were further applied for biolabeling of Gram-negative recombinant GFP E.coli and Gram-positive S.aureus bacteria. Results of time—dependent fluorescence microscopic studies of recombinant GFP E.coli cells enabled the prediction of optimal labeling time, while TEM images further provided an insight into the underlying mechanism of biolabeling. The present study highlights the potential of CPs to serve as high -performance optical nanoprobes and could very well be adopted for various biolabeling applications. The strategy of combining a biodegradable polymeric nanocarrier and fluorescence imaging * agent on a single platform can serve the dual purpose of gene delivery and bioimaging with minimal side effects. Among the non-viral vector systems, chitosan has been frequently used for pDNA delivery on account of its biocompatibility and biodegradability. The present study deals with the synthesis of chitosan-pDNA (GFP) nanocomplexes by a complex coacervation process. The physicochemical properties of nanocomplexes such as size, morphology and charge were studied through atomic force microscopy (AFM) and zeta potential analysis. The complexation/condensation ability of various vector/pDNA ratios were evaluated by gel retardation assay and ethidium bromide (EtBr) condensation assay. The pDNA loading efficiency was calculated by UV-visible spectrophotometer. Similarly, pDNA release studies -ç were done by monitoring the pDNA concentration at 260 nm by UV-visible spectrophotometer. Such a non-viral vector system could be used for gene delivery studies. pDNA encoding green fluorescent protein (GFP) could be used to monitor the transfection efficiency and gene expression, further, the intrinsic fluorescence property of carbon dots could be used to track the nanovector and monitor the cellular uptake. Thus, the development of such biofriendly fluorescent nanovectors as therapeutic and diagnostic system has huge theranostic potential.