Rare Earth Nanocomposites Based on Chitosan Platforms for Biological Applications
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Rare Earth Nanocomposites Based on Chitosan Platforms for Biological Applications Zannatul Yasmin1, Maogen Zhang2, Waldemar Gorski2, Saher Maswadi3, Randolph Glickman3, Kelly L. Nash1 1 Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, U.S.A. 2 Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, U.S.A. 3 Ophthalmology, University of Texas Health Science Center-San Antonio, San Antonio, TX 78229, U.S.A. ABSTRACT Chitosan (CHIT), a natural biopolymer, has established its applicability in numerous studies including, tissue scaffolds, topical antimicrobial agents, glucose biosensors and drug delivery platforms. Among these applications, biosensors utilizing CHIT has been championed due its excellent film-forming ability, biocompatibility, good adhesion, non-toxicity, and susceptibility to chemical modification due to the presence of plentiful amino groups and hydroxyl groups. The challenge in development of many biosensing materials is that they should offer robust and tunable characteristics (fluorescence, magnetic, thermal, etc.) while remaining biocompatible. In this work, a facile method was developed to synthesize biocompatible hetero-nanoparticles which inherently display multifunctionality based on a few interchangeable components. As an example, we present a system composed of rare earth metal oxide (REMO) nanoparticles, Er doped Y2O3, with the attachment of gold nanostructures using CHIT. The resulting REMO@CHIT@Au0 hybrid nanoparticles are capable of displaying tunable optical properties due to the surface plasmon resonance of the gold nanoparticles useful to photoacoustic applications. An overview of the nanostructure components are given followed by morphological and spectroscopic analyses. The results of the characterizations are the focus of our future work towards the applicability of these systems to biological sensing, detection and contrast agents. INTRODUCTION Rare earth (RE) ions have been widely used as luminescent materials because of their spectroscopic properties [1, 2]. In recent decade the technological applications of rare earth nanocomposites have grown dramatically [3]. Applications of them are as far ranging as remote sensing [4], optical imaging [5], magnetic contrast agents [6], photoacoustic detection & imaging [7], capillary electrophoresis [8], biosensors [6] and drug delivery [9] platforms. More recently, there has been growing interest in tunability of the luminescence from these materials by addition of transition metals (e.g. Au, Ag, Pt) [10-14] based on their effective emission intensity and photo-stability of appropriately positioned fluorophores and RE nanoparticles (NP). However, most of these transition metal nanocrystals have been attached by aminosilane coupling agents which limit the surface functionality of the NP and require to synthesis gold (Au) nanoparticles in a separate method. To overcome these limitations as previously reported in [11], an alternate approach is the use of chitosan (CHIT) [15]. CHIT is a well-known b
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