6.4.2. Polyacrylates

Polyacrylates are polymers derived from acrylic acid via free radical polymerization. Nevertheless, Garay-Jimenez et al. (2011) reported an alternative method for producing polyacrylate nanoparticles between 40 and 50 nm by emulsion polymerization using a 7:3 mixture of butyl acrylate and styrene in water containing sodium dodecyl sulfate as a surfactant and potassium persulfate as a water-soluble radical initiator. The resulting method seemed promising for the encapsulation of bioactive agents of interest in the biomedical field [150].

Polyacrylates are anionic polymers that present maximum swelling at pH neutral to alkaline, and minimum under acidic conditions, making them ideal for colon-specific drug delivery systems [151].

Feuser et al. (2016) modified with folic acid polymethyl meta acrylate and ferrous sulfate to produce superparamagnetic nanoparticles with excellent colloidal stability and high e fficacy in encapsulating lauryl gallate (antioxidant). The release profile of lauryl gallate showed an initial burst effect followed by a slow and sustained release, indicating a biphasic release system. The lauryl gallate loaded in superparamagnetic polymethyl methacrylate (PMMA) nanoparticles did not have any cytotoxic e ffects on non-tumoral cells. Moreover, the folic acid promoted folate receptor-mediated endocytosis in tumoral cells, enhancing the anticancer e ffect of lauryl gallate [152].

Ramalingam et al. (2018) loaded curcumin in electrospun fibers to generate a dressing for the treatment of skin cancer. The dressing induced cell proliferation and free radical scavenging activity and up-regulated the expression of CDKN2A in A375 melanoma cells. The cell death of A375 melanoma cells was dose- and time-dependent, which indicates that treatment with curcumin loaded in the nanofibers inhibited the growth and induced the cell death of the skin cancer cells [151].

Ballestri et al. (2018) developed a synthetic antioxidant (porphyrin) and encapsulated it in polymethyl methacrylate (PMMA) core-shell nanoparticle (70 nm diameter) for photodynamic cancer therapy. Photodynamic cancer therapy uses a light to activate an antioxidant compound. The capsule

protected porphyrin against unwanted bleaching while preserving the anticancer activity, which was similar to that of free porphyrin under in vitro testing [153].

Recently, Sobh et al. (2019) synthesized a multi-walled carbon nanotube (MWCNT)/Poly(methyl methacrylate-co-2-hydroxyethyl methacrylate) P(MMA-co-HEMA) nanocomposite loaded with either curcumin or its water-soluble derivative via an in situ microemulsion polymerization technique by using different ratios of multi-walled carbon nanotube MWCNT to drug. Curcumin could be loaded in higher amounts with high entrapment efficiency values with improved thermal stability with an increased MWCNT ratio. The in vitro drug release studies of the nanocomposite showed a prolonged controlled release in the intestinal fluid at pH 7.4 and that ≤ 8% of the drug was lost in the stomach fluid at pH 1.2 [154].

Sunoqrot et al. (2019) developed a pH-sensitive polymeric nanoparticle of quercetin as a potential colon cancer-targeted nanomedicine. Quercetin is an abundant plant polyphenol with demonstrated efficacy in CRC. The researcher developed polymeric nanoparticles of quercetin based on the pH-sensitive polymer methacrylic acid and copolymers (Eudragit® S100) to achieve colon pH-specific drug release. The researchers found nanoparticles with a mean diameter of 66.8 nm and a partially negative surface charge of −5.2 mV. In vitro release testing showed a delay in drug release in acidic pH but complete release within 24 h at pH 7.2. A cytotoxicity assay on CT26 murine colon carcinoma cells displayed a significantly higher potency of encapsulated quercetin (IC50 = 0.8 μM) than free quercetin (IC50 = 65.1 μM) [155].
