# Polymers and Polymer Nanocomposites for Cancer Therapy +
## 4 Polymer Micelles  
Polymer micelles are an important group of drug carriers in chemotherapy treatments. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Macromolecular Carrier** & **Carrier Structure** & **Carrier Morphology** & **Experimented Drug** & **Reference** \\ \hline Polyurethane & Synthetic & Homopolymer & DOX & [20] \\ Poly(ethylene glycolo- & Synthetic copolymer & Nanocomposite & DOX & [25] \\ poly(vinylpyridine)/nSi & Poly(methylmethacrylate- & Synthetic copolymer & Nanocomposite & Naproxen & [27] \\ comicroporous Si & Chitosan-copoly & Bio-co-synthetic copolymer & Nanocomposite & DOX/HCI & [38] \\ (methylmethacrylate/)Fe\({}_{3}\)O\({}_{4}\) & copolymer & & & \\ Folic Acid-Chitosan-poly(d,- & Biopolymers & Nanocomposite & Carboplatin & [43] \\ lactic acidco-glycolic acid) & Hitosan-gpoly(ethylene glycol & Graft copolymer & Nanocomposite & Bevacizumab & [52] \\ (methacrylate) & Biodegradable blend & Nanocomposite & DOX & [66] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Carriers and drugs used in different studies. The need for smart materials in the area of biotechnology has accelerated the development of stimuli-responsive copolymer micelles. To achieve the simultaneous delivery of chemotherapeutic drugs and gene agents, the carriers must be able to protect them from degradation and premature release. Micelleplexes consisting of amphiphilic block copolymers are made of interior hydrophobic blocks, with hydrophilic blocks forming the shell. The first ones act as a reservoir for poorly soluble hydrophobic drugs, and the hydrophillics mask the payloads. A study has shown that the block copolymer adsorbed on a nanoparticle can acquire the structure of a micelle [70]. Redox-responsive core-crosslinked polymers were prepared by crosslinking mPEGylated starch (St) (mPEG-St) with 3,3'-dithiodipropionic acid (DPA), a crosslink containing a disulfide bond. The (mPEG-St-DPA) micelles showed good stability, and a protein adsorption test indicated that the micelles were homcompatible. In vitro release studies showed that DOX-loaded micelles exhibited enhanced release of DOX in the presence of glutathione. An in vitro MTT assay confirmed that the core-crosslinked mPEG-St-DPA micelles were biocompatible with HeLa cells and that DOX-loaded micelles displayed a higher inhibition of HeLa cell proliferation. The study suggested that the redox-responsive mPEG-St-DPA micelles hold great potential as ideal drug delivery carriers for cancer therapy [71]. To optimize nanosized micelles based on the PEG-PLA-PEG triblock copolymer, the effect of PLA on the physicochemical properties of micelles was studied. It was established that the loading amount of DOX encapsulated in micelles as well as the release of DOX from the micelles depended on the molecular weight (MW) of PLA. The triblock copolymers themselves did not show any toxicity over a wide range of concentration. DOX-loaded micelles killed more tumor cells than the free DOX [72]. Polymeric micelles consisting of hydrophobic polyethyleneimine and cis 1,2-cyclohexandycarboxylic anhydride were used to deliver drugs such as Candesartan and Paclitaxel (PTX) in the chemotherapy treatment of cervical cancer. The PTX-loaded micelles have great potential as a binary drug delivery system for efficient cancer therapy via synergism [73]. Other micelles based on a 1-pyrenemethanol-modified carboxymethyl CS conjugate with succinyl linkage were produced to regulate tumor extracellular pH. This study provided a new strategy for the design of tumor extracellular pH nanocarriers for drug delivery [74]. An amphiphilic copolymer based on a PEG hydrophilic segment, an FA-targeting agent, a lysine (L) linker, and a polycarbonate (PCL) hydrophobic segment was produced. The tests done revealed that the copolymer was practically nontoxic and that the obtained micelles have great potential for use in drug delivery [75]. A biocompatible and biodegradable diblock copolymer based on a PEG-poly(DL-lactide) micelle was prepared for the delivery of DTX to treat cervical cancer.