www.advhealthmat.de www.MaterialsViews.com FULL PAPER © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 wileyonlinelibrary.com Co-encapsulation of Biodegradable Nanoparticles with Silicon Quantum Dots and Quercetin for Monitored Delivery Qi Wang, Yongping Bao,* Jayshree Ahire, and Yimin Chao* DOI: 10.1002/adhm.201200178 Q. Wang, J. Ahire, Dr. Y. Chao Energy Materials Laboratory School of Chemistry University of East Anglia Norwich, NR4 7TJ, UK E-mail: y.chao@uea.ac.uk Dr. Y. Bao Norwich Medical School University of East Anglia Norwich, NR4 7TJ, UK E-mail: y.bao@uea.ac.uk Polymer nanoparticles have emerged as a promising new strategy for the efficient delivery of drugs. They have several advantages when used as drug carriers, such as high stability, high capacity, improvement of drug bioavaila- bility, as well as allowing for sustained drug release. Quercetin has therapeutic potential as an anticancer drug, but has poor solubility and low bioavailability. In this study it is shown that co-encapsulation of quercetin and fluorescent Silicon quantum dots (SiQDs) in poly (ethylene glycol)-block-polylactide (PEG–PLA) nanoparticles can be used for simultaneous in vitro imaging and to improve the biocompatibility of quercetin. Fluorescent imaging with SiQDs can provide a new concept to monitor the delivery of anti-cancer drugs. The nanoparticles are synthesized based on the double emulsion method and are extensively characterized and assayed for cytotoxicity in vitro. HepG2 cells are incubated with quercetin and SiQDs dual-loaded PEG–PLA nanoparticles, resulting in a red fluorescent staining which can be detected with a confocal microscope. PEG–PLA nanoparticle encapsulated quercetin suppresses human hepatoma HepG2 cell proliferation more effectively than the free-standing form. In addition, nanoparticle-encapsulated quercetin significantly inhibits hydrogen peroxide-induced DNA damage in HepG2 cells. These data show that nanocapsulated quercetin possesses the potential bioactivity to reduce the drug dosage frequency, as well as increase patient compliance. The combina- tion of polymeric nanoparticles and semiconductor quantum dots can allow monitoring of delivery, improve aqueous solubility, and enhance biocompat- ibility. Such nanoparticulated systems could shape the future of drug delivery. nanotechnology for the development of efficient anticancer drug delivery systems is one of the most recent advances in bio- medical science. [1,4] The development of nanovectors, such as nanoparticles (NPs), can be used to load drugs or imaging agents which can then be targeted to tumors. [1,5] Nanoparticles are produced from a wide variety of materials including carbon, heavy metals, semiconductors, and polymers, which each have their own advantages and disadvantages. [6–8] Bio- degradable polymeric nanoparticles have attracted considerable attention as poten- tial drug delivery devices. [9,10] Most drugs formulated with organic solvents have poor solubility and low bioavailability. [11] The use of polymeric nanoparticles allows for the preparation of hydrophobic cancer medications which have improved bio- availability. [12] Furthermore, the structure of polymeric nanoparticles can allow them to encapsulate multiple anticancer drugs, and visibility enhancers, simultaneously; while the tunable surface functionality allows them to conjugate with permeation enhancers and targeting ligands such as polyethylene glycol, aptamer, or antibodies on intended treatment. [13] Polyacrylic acid- terminated SiQDs (PAAc-SiQDs), possess strong luminescence characteristics, as well as low inherit cyto- toxicity compared to conventional heavy metal QDs, making them potentially very useful in biological imaging applica- tions. [14,15] Moreover, the red fluorescence possessed by SiQDs is not strongly absorbed by cells, rendering them even more suitable when used as imaging agents. [14–16] Polymeric nanoparticles can be synthesised using various methods tailored to the needs of the application and the type of drugs to be encapsulated. [17] The synthesised nanoparticles are: stable in blood; non-toxic; biodegradable, which provide con- trolled release; sub-cellular size; biocompatible with tissue and cells. [18] Polylactide (PLA) is a synthetic biodegradable polymer, while poly(ethylene glycol) (PEG) possesses good hydrophilicity, flexibility, resistance to immunological recognition, and biocom- patibility. [19] Consequently PEG–PLA copolymer has great advan- tages, such as improved hydrophilicity and degradation rate, and shows a high potential for development in drug delivery. [19] 1. Introduction In recent years, nanotechnology has been employed in cancer diagnosis, detection and treatment. [1–3] Utilization of Adv. Healthcare Mater. 2012, DOI: 10.1002/adhm.201200178