6.4.7. Polyesters

Polyesters are polymers that contain the ester functional group in their main chain [156]. Polyesters are produced via condensation or ring-opening reactions. Due to the strong presence of oxygen groups, this polymer can poses a negative charge that can respond to pH changes [177]. Moreover, some polyesters can be enzymatically degraded such as in the case of polycaprolactone (PCL), polylactic acid (PLA), and polyhydroxyalkanoates (PHA), among others [178–181]. Lipases are an important group of esterases for the biodegradation of aliphatic polyesters. They are produced in the pancreas, liver, and digestive system to break down fat [180]. Fat and polyesters have the same functional groups (esters), which leads the enzyme to degrade these polymers. For CRC, antioxidants have been successfully encapsulated in PLA and in Poly (dl-lactic-co-glycolic) acid (PLGA). PCL and PHA have been employed via mixtures and copolymers, as described in Section 6.4.9.

Alippilakkotte et al. (2018) encapsulated curcumin in polylactic acid (PLA) using an eco-friendly emulsification-solvent evaporation strategy. The method resulted in an efficiency of around 90%. The in vitro release studies showed a sustained curcumin release, after a burst release, in the initial 12 h. The curcumin-loaded PLA nanocapsules could easily penetrate into the cancer cells and can cause a sustained drug release for effective cancer treatment [177].

Pereira et al. (2018) encapsulated Guabiroba phenolic extract in Poly (dl-lactic-co-glycolic) acid (PLGA) nanoparticles to improve the stability, bioavailability, and bioactivity of the extract. The encapsulated extract proved to present a higher antioxidant capacity compared to free extract. Moreover, a reduction in ROS generation in non-cancer cells was achieved with lower extract concentrations (*p* < 0.05) after encapsulation [181].
