# Polymers and Polymer Nanocomposites for Cancer Therapy +
## 3 Biopolymers and Biopolymer Nanocomposites
Ag chloride/polypyrrole (PP)/CS, an AgCl/PP/CS core-shell nanocomposite, was prepared by in situ oxidative polymerization of pyrrole using ferric chloride in the presence of CS and Ag nitrate to develop a carrier and controlled release system for 3-amino-2-phenyl-4(3H)-quinazoline (I). For a comparison, PP/CS core-shell nanoparticles were prepared and loaded by I. The study revealed that loaded AgCl/PP/CS exhibited excellent antibacterial and anticancer efficacy against Ehrlich ascite carcinoma cells [42]. Poly(d,l,-lactic-co-glycolic acid) (PLGA) is the most frequently used biodegradable and biocompatible polymer in terms of preparation nanoparticles for biomedical applications. It was prepared to obtain nanocarriers for the Pt-based antitumor drug Carboplatin. In order to improve its delivery, folic acid (FA)-conjugated CS (FA/CS/PLGA) nanoparticles have been produced. The modified PLGA nanoparticles are expected to enhance cellular uptake for tumor accumulation promoted by embraced permeability and a retention effect [43]. Release studies have indicated that CS beads coated with pH-dependent poly(acrylic acid) PAA-PVP polyblends offer much protection from drug release in simulated gastric fluid. A controlled release of the drug Dexamethasone from CS was observed once the coating layer of the pH-dependent polymer complex started to dissolve at a higher pH (6.8). It was concluded that the CS nanoparticles coated with PAA-PVP complexes can be used for effective controlled delivery of the drug directly to the colon [44]. A composite made of CS, hydroxy apatite (HAP), and a glycopymer grafted on a Cloisite 30B clay surface (CS/HAP/clay-g) and another one based on CS/HAP pristine Cloisite 30B (CS/HAP/clay-g) have been synthesized. Their cytotoxicity was tested against breast carcinoma cell line (Hep G-2) and a normal human skin fibroblast cell line (BJ-I) using an MTT as well as a lactate dehydrogenase assay. The results showed that the biopolymer composite CS/HAP/clay-g can be used in biomedical applications [45]. Besides other already discussed properties, CS nanocomposites have the ability to increase retention time and thus are able to release drugs for a longer time, making them an ideal drug delivery vehicle. Study of the drug delivery behavior of nanostructured CS composites may lead to the realization of more effective vehicles in drug delivery systems. The therapeutic application of nanostructured CS composites in various types of cancers, such as bladder cancer, breast cancer, pancreatic cancer, metastatic cancer, lung cancer, colon cancer, and prostate cancer, is being focused on [46]. FA-modified carboxy methyl CS was polymerized with N-3-acrylamidophenyl boronic acid monomer to prepare tumor-targeting nanoparticles that enhanced drug accumulation in tumors, which finally increased antitumor efficiency in H22 tumor-bearing mice [47]. The anticancer effect of Alphastatin (AS), a 24-amino acid peptide, is limited by its short half-life and degradation in the body. The prepared AS/CS nanoparticles had a sustained release of 6 days and were stable in serum for at least 24 h. In a subcutaneous LA975 lung carcinoma xenograft T739 mouse model, the nanoparticles significantly inhibited tumor growth, tumor volume, and microvessel density, and the antitumor effect was even stronger than that of AS. The study indicated that AS/CS nanoparticles inhibited the SphK1 signaling pathway and enhanced the antiangiogenic effect of the drug both in vitro and in vivo [48]. In one study, the researchers grew colon and hepatocellular carcinoma cells (HCCs) on CS membranes and evaluated the tumor progression and cancer stem cell (CSC) properties. The results showed that developing cancer cells on CS increased cell motility, drug resistance, quiescent population, self-renewal capacity, and the expression levels of stemness and CSC marker genes. The CS culture system provides a convenient platform for research on CSC biology and the screening of anticancer drugs [49].