Page - 38 - in Cancer Nanotheranostics - What Have We Learnd So Far?

Dawidczyketal. Nanomedicines for cancer therapy Table3 |Summaryofnanoparticleplatformsfornanomedicine. Particle type Composition/Structure Properties Applications Polymer e.g.,PLGA,glycerol, chitosan,DNA; monomers, copolymers,hydrogels Somebiodegradable Drugdelivery; passive release (diffusion), controlled release (triggered) Dendrimer PAMAM,etc. Lowpolydispersity, cargo, biocompatible Drugdelivery Lipid Liposomes,micelles Cancarryhydrophobiccargo, biocompatible, typically50–500nm Drugdelivery Quantumdots CdSe,CulnSe,CdTe,etc. Broadexcitation,nophotobleaching, tunableemission, typically5–100nm Optical imaging Gold Spheres, rods,or shells Biocompatibility, typically5–100nm Hyperthermia therapy,drugdelivery Silica Spheres, shells,mesoporous Biocompatibility Contrast agents,drugdelivery (encapsulation) Magnetic Ironoxideorcobalt-based; spheres, aggregates indextranorsilica Superparamagnetic, ferromagnetic (small remanence tominimize aggregation), superferromagnetic (∼10nm),paramagnetic Contrast agents (MRI), hyperthermia therapy Carbon-based Carbonnanotubes,buckyballs, graphene Biocompatible Drugdelivery Organic polymer systems include synthetic polymers [e.g., polyethyleneimine (PEI),polyethyleneglycol] (Knopet al., 2010; Nicolas et al., 2013), synthetic hydrogels (e.g., polyacrylamide) (Ando et al., 2012; Liechty andPeppas, 2012), natural polymers (e.g., chitosan, hyaluronic acid, alginate, gelatin) (Ando et al., 2012) and hydrolytically or enzymatically degradable polymers (e.g., collagen, polylactic acid, polycaprolactone) (Balogh et al., 2007).Combinationsofcomponentsand/ormonomerunits and incorporation of other building blocks such asDNA contribute to theflexibilityofpolymer-basednanoparticleplatforms.These systems can be passively loaded with a cargo, or a cargo can be incorporated to allow triggered release (Davis et al., 2008). Particles such as block copolymers, liposomes, and dendrimers canprovideareservoir for largeamountsof cargo.Blockcopoly- mers combine the attributes of two or more monomer units allowing further functionality (Duncan, 2006;GrecoandVicent, 2009). Lipid-basednanoparticles includemicelles, liposomes, or water oil emulsions. Dendrimers are hyperbranched synthetic polymers forwhichbiodistribution, size, andmultifunctionality canbe tunedwithavery lowdegreeofpolydispersity (Choetal., 2008). Proteins (e.g., albumin) (Fuchs and Coester, 2010) and viruses (Steinmetz, 2010) have also been extensively studied for drugandgenedelivery. Inorganic nanoparticles provide advantages in function and properties not possible with organic nanoparticle platforms, althoughthisisoftenattheexpenseofbiocompatibility.Examples ofmaterials include semiconductors (quantumdots) (Gaoet al., 2004;Medintzet al., 2005;Michalet et al., 2005;Parket al., 2011; Chen et al., 2012a; Petryayeva et al., 2013), silica (Vanblaaderen andVrij, 1992; Giri et al., 2005, 2007; Burns et al., 2006), gold (BoisselierandAstruc,2009;Arvizoetal., 2010),magneticmate- rials (Arruebo et al., 2007; Banerjee et al., 2010; Haun et al., 2010),andcarbon-basedmaterials(Pratoetal.,2008; Jain,2012). Semiconductor nanoparticles, or quantum dots, have a narrow andtunableemissionspectrum,abroadexcitationspectrum,and donotphotobleach.These characteristics are attractive for opti- cal imaging, however,manyquantumdots are synthesized from heavy metal elements and hence toxicity is a concern. Silicon dioxide (silica), themost widely used oxide, is a versatilemate- rial that is relatively inert. Silica canbeused toencapsulateother materials or cargoes and the surface can be conjugated using silane chemistry. Silica can be synthesizedwith nanometer scale pores (mesoporoussilica) thatcanbeused toholdothercargoes. Of themetallicmaterials, gold iswidelyused forbiologicalappli- cationsas it iseasytosynthesize,canbefunctionalizedusingthiol chemistry,andisrelatively inert.Manyofthenoblemetalsabsorb Frontiers inChemistry | ChemicalEngineering August2014 |Volume2 |Article69 | 38