Page - (000356) - in Biomedical Chemistry: Current Trends and Developments

the pores, high surface area and large pore volume enables high-drug- loading capacity. The confinement of large amounts of drug molecules, together with their interaction with the nanocarriers, and depending on the physicochemical properties of the PSi materials, leads to a tunable and controllable release of cargos (Mäkilä, 2014; Salonen, 2008). Controlled release of drug molecules can be also achieved through the uniform incorporation of the drug into matrix-based systems (water- insoluble polymer carriers). These systems enable sustained drug release because the diffusion of drug molecules from the inner matrix of the polymers to the surface takes time and may depend on the physicochemical properties of the drug, on the interactions between the drug and the polymeric matrix, and on the density of the matrix itself (Sun, 2014). Ma have synthesized a PCL-Tween 80 copolymer nanoparticulate matrix from ε-caprolactone and Tween 80 to maintain the release of cargos through diffusion for as long as 28 days, with a better in vitro cytotoxicity towards C6 glioma cells compared to the commercial docetaxel (Taxotere) at the same drug concentration (Ma, 2011). Sustained release can similarly be achieved by using nanocarriers made of erodible or degradable materials. The release can be tailored by tuning the erosion kinetics of nanoparticles through the selection of biodegradable polymers, such as poly(lactic acid) (PLA), poly(lactic-co- glycolic acid) (PLGA), polyethylene glycol (PEG), polycaprolactone (PCL) among others (Sun, 2014), and through different encapsulation methods (Zilberman, 2008). Sun have successfully constructed a biodegradable nanoparticle based on a triblock copolymer PEG-b-PCLb-poly (2- aminoethylethylene phosphate) (Fig. 3.5.2) with a proven fruitful delivery of small interfering RNA (siRNA) and paclitaxel for synergistic tumor suppression (Sun, 2011).