One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates
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NANO EXPRESS
Open Access
One-step colloidal synthesis of biocompatible water-soluble ZnS quantum dot/chitosan nanoconjugates Fábio P Ramanery, Alexandra AP Mansur and Herman S Mansur*
Abstract Quantum dots (QDs) are luminescent semiconductor nanocrystals with great prospective for use in biomedical and environmental applications. Nonetheless, eliminating the potential cytotoxicity of the QDs made with heavy metals is still a challenge facing the research community. Thus, the aim of this work was to develop a novel facile route for synthesising biocompatible QDs employing carbohydrate ligands in aqueous colloidal chemistry with optical properties tuned by pH. The synthesis of ZnS QDs capped by chitosan was performed using a single-step aqueous colloidal process at room temperature. The nanobioconjugates were extensively characterised by several techniques, and the results demonstrated that the average size of ZnS nanocrystals and their fluorescent properties were influenced by the pH during the synthesis. Hence, novel ‘cadmium-free’ biofunctionalised systems based on ZnS QDs capped by chitosan were successfully developed exhibiting luminescent activity that may be used in a large number of possible applications, such as probes in biology, medicine and pharmacy. Keywords: Nanoparticle; Quantum dot; Colloid; Biopolymer; Chitosan; Bioconjugates; Nanomaterials PACS: 81.07.Ta; 78.67.Hc; 78.67.Sc; 82.35.Pq
Background Since the classic talk from Richard Feynman, titled ‘There's plenty of room at the bottom’, presented on 29 December 1959 at the annual meeting of the American Physical Society (at the California Institute of Technology, USA), introduced the concept of nanotechnology, this technology has evolved at an outstanding pace in practically all areas of sciences [1,2]. To be considered as nanotechnology, nanosized and nanostructured systems should present one or more components with at least one dimension ranging from 1 to 100 nm. In recent years, innovation in nanotechnology and nanoscience for medicine (or nanomedicine) has been a major driving force in the creation of new nanocomposites and nanobioconjugates. Essentially, these materials may bring together the intrinsic functionalities of inorganic nanoparticles and the biointerfaces offered by biomolecules and polymers of natural origin, such as * Correspondence: [email protected] Center of Nanoscience, Nanotechnology and Innovation - CeNano2I, Department of Metallurgical and Materials Engineering, Escola de Engenharia, Federal University of Minas Gerais, Bloco 2, Sala 2233, Av. Antônio Carlos, 6627, Belo Horizonte, Minas Gerais 31270-901, Brazil
carbohydrates and derivatives, glycoconjugates, proteins, DNA, enzymes and oligopeptides [3-5]. In view of the large number of available alternatives to produce hybrids and conjugates for bioapplications, carbohydrates have been often chosen, due to their biocompatibility, physicochemical and mechanical properties, and relative chemical solubility and stability in aqueous physiological environment [5-8]. Among t
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