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Conniotet al. Nanocarriers for immunecell targetingand tracking FIGURE2 |Examplesofpolymeric, lipid,andmetaland inorganicnanocarriers. liposomesas carriers for antisenseoligonucleotides, as siRNA, in cancer therapy(Tari etal., 1996). Van Broekhoven et al. (2004) have reported a DC-targeting vaccine, based on a liposomal formulation, as an outstanding platformtoinduceahighlyeffectiveimmunityagainsttumorcells (Van Broekhoven et al., 2004). Preclinical studies of liposome- DNAcomplexes have also beendescribed, constituting an effec- tive strategy toelicit anti-tumor immunity(U’renetal., 2006). The phase I clinical trial of a liposomal cancer vaccine for breast, ovarian andprostate cancer has alreadybeen reported. It has been proved that this peptide vaccine, which is intended to elicitmulti-functionalT-cell responses, is safe and immunogenic (Berinsteinetal., 2012). Additionally, liposomeshavebeenstudiedascarriers foralter- native bioorganic and biodegradable contrast agents, as glyco- gen and poly-L-Lysine.With these liposomes, it was possible to develop an in vivomulti-colormagnetic resonance imaging for lymphnodemapping(Chanetal., 2014). Polymericnanoparticles (NPs) Polymeric NPs are submicron-sized polymeric colloidal par- ticles with excellent features as vehicle for the delivery of drugs, biomolecules andgenes (PanyamandLabhasetwar, 2003; MahapatroandSingh,2011). Polymerproperties such as biocompatibility, low toxicity and biodegradability have highlighted polymericNPs as an interest- ing delivery strategy. The chemical structure of the polymers is easilymodified, allowing the development ofmultifunctional engineered systems.Nanoparticle size, shapeandsurfaceproper- ties can also be tailored, as well as the degradation kinetics and mechanicalproperties (Albertsson,2002). PolymericNPs are usually highly stable and can easily entrap and/oradsorbbothhydrophilicandhydrophobicmoleculeswith good efficacy (Gelperina et al., 2005). The drug entrapment protectsmolecules fromdegradation (Singh and Lillard, 2009). Additionally, asnano-sizedpolymericparticles, thesecarriers are easily transported through extra and intracellular barriers. As a result, entrapped agentsmay be delivered site-specifically, for instance in inflamedareasor tumors, after crossing theendothe- lium(ProkopandDavidson,2008;SinghandLillard,2009). Twodifferent types of polymericNPs are usually considered: nanospheresandnanocapsules (Figure3B).Nanospheres consist inapolymericmatrixinwhichthedrugorcargoishomogenously dispersed,whereasnanocapsules arevesicular systems formedby www.frontiersin.org November2014 |Volume2 |Article105 | 76