# Polymers and Polymer Nanocomposites for Cancer Therapy +
## 4 Polymer Micelles
The results of an in vitro study confirmed that such micelles could be used as a surfactant-free effective carrier for the delivery of DTX [76]. Poly[L-co-N,_N'_-bis(acryloyl) cystamine-co-dodecylamine] nanomicelles (Nms) were synthesized through addition depolymerization. DOX was loaded onto Nms for the investigation of its delivery. The Nms were biocompatible and biodegradable and could be potentially used as drug vehicles in controlled release [77]. Carbon quantum dots (Qds) are believed to play a key role in the field of targeted drug delivery [78]. The synthetic polymer \(\dot{\alpha}\),\(\beta\)-poly(N-hydroxyethyl)-DL-asparamide (PHEA) was functionalized with lipoic acid (LA) pendant moieties to obtain a synthetic derivative (PHEA-LA-PEG-FA) able to self-assemble in aqueous medium, giving rise to polymer micelles exposing their FA- and PEG-targeting groups. The drug-carrying ability of the copolymer micelles was studied along with the cytotoxicity of the obtained nanostructure, aiming at breast cancer cells employing DOX. The properties of the Au shell Qds incorporated in the micelles as cell imaging agents and a photothermal anticancer treatment tool were explored [79]. It was found that an ultrasensitive reduction-responsive polymeric spherical micelle based on a polytriphenylporphyrin polydisulfide ester as a porphyrin photosensitized delivery system in aqueous solution exhibited rapid and effective release of the porphyrin photosensitizer under an intracellular reductive atmosphere. The results of in vitro intracellular endocytosis and cytotoxicity validated that compared to the polymeric micelles, cellular uptake ability was enhanced, and antitumor efficiency was improved. Thus, as a photosensitizer delivery system, the copolymer showed promising potential applications in photodynamic cancer therapy, with excellent reductive responsiveness [80]. Block copolymer micelles made of PEG, dimethyl thioketal (DMTK), SS, and PLA (PEG-DMTK-SS-PLA) were obtained, and their self-assembled redox and oxidative stress dual-responsiveness were studied, and they were proven to be promising as an efficient drug delivery system. The analyses were conducted with several cancer cells (cervix, lung, gastric, and colon) [81]. In a recent study, nanocarriers based on amphiphilic block copolymers with tailored temperatures and pH responsiveness were prepared. The hydrophilic blocks consisted of temperature-sensitive N-isopropylacrylamide and pH-sensitive units of 5-methacryloyloxy pentatonic acid or 4-methacryloyloxy benzoic acid, while the hydrophobic blocks were composed of n-hexyl acrylate or styrene. Some of these types of micelles may find applications as drug carriers [82]. DOX-mixed micelles for biotin-targeted drug delivery and enhanced photothermal/photodynamic therapy (PTT/PDT) and glutathione-mixed micelles were prepared from a polycarbonate-disulfide bond-biodegradable photoluminescence polymer (PCL-SS-BPLP) and biotin PEG-cypate. Chemically linking cypate into the mixed micelles greatly improved cypate solubility and the PTT/PDT effect. The micelles also exhibited good monodispersity, stability in the cell medium (\(\sim\)119.7 nm), low critical micelle concentration, good biodegradability, and resistance to photodecomposition. The designed biodegradable micelles showed promise as carriers for antitumor drug delivery and chemo/PTT/PDT combination therapy [83]. Multifunctional smart carriers, which can release their payload upon an external or internal stimuli such as pH or temperature, are proving to be major frontrunners in the development of effective strategies to combat cancer with minimal side effects. Among pH-responsive polymers are PAA, poly(methacrylic acid), and poly(\(N\),\(N\) dimethyl aminoethyl methacrylate). Temperature-response polymer micelles have been the most studied to date. They can be categorized according to either lower critical solution temperatures or upper critical solution temperatures. Other micelles are light-responsive or even multiresponsive [84].