# Polymers and Polymer Nanocomposites for Cancer Therapy +
## Polymer Hydrogels and Nanogels
Then, N-isopropylacrylamide and itaconic acid were successfully copolymerized to prepare the thermo- and pH-responsive magnetic nanohydrogels. Drug loading was examined along with other tests, with Mitoxantrone as an anticancer drug. The results confirmed the low toxicity and enhanced anticancer effect of the drug-loaded magnetic nanogels [113]. A biocompatible nanogel based on glycogen and 2-hydroxy ethyl methacrylate using an ethylene glycol dimethacrylate crosslinker was produced. Mesoporous silica was used as a template. The nanogel was shown to effectively load the 5 FU drug. An intercellular release experiment demonstrated that 5 FU-loaded nanogel could efficiently kill MG-63 cancer cells [114]. Functionalized biocompatible disulfide nanogel on the basis of \(N\),\(N^{\prime}\)-di-(tert butoxy carbonyl) cysteine-crosslinked magnetite PEG containing FA was synthesized. For this purpose, star-shaped PEG coupled with amino silane was grafted onto Fe\({}_{3}\)O\({}_{4}\) nanoparticles. L-cystine amino acid was used to crosslink two free hydroxyl groups of PEG to produce the desired redox-sensitive disulfide nanogel 5 FU as a drug. The structure of the nanogel was designed so that the toxic active drugs could be released only inside the targeted cells after a controlled time. The produced nanogel demonstrated specific targeting of FA receptor-positive cells [115]. In the development of a tumor targeting pH-responsive and enzymatically degradable crosslinked fluorescent nanogels made of boronic acid-conjugated lactose-modified CS (chitlac-BOH) and dopamine, nitric oxide-conjugated partially carbonized HA for DOX loading was reported. Carbonized HA and NO were released from DOX-loaded fluorescent nanogels due to the pH-dependent cleavage of anticancer agent loading. The system used tumor-targeting HA to deliver DOX and NO within cancer cells, while tracking was performed [116]. Various specially designed copolymers, such as poly(N-isopropylacrylamide-co-acrylic acid) nanogels with different molar compositions, were synthesized and evaluated as carriers for drug delivery. After testing, DOX-HCl presented excellent dispersibility in physiological environments (pH 7.4 and 5 at 37 \({}^{\circ}\)C). Their release behavior coupled with their size and low cytotoxicity makes these nanogels good carriers in cancer therapies based on an enhanced permeability and retention effect with drug pH-triggered release after endocytosis in tumor cells [11]. It was shown that the therapeutic efficacy of thermoresponsive nanogels as protein carriers was triggered by a decrease in temperature. The authors of the research envisioned the use of such thermal triggers as being relevant for the treatment of superficial tumors, in which the induction of apoptosis can be controlled through the application of local cooling agents [117]. Temperature- and pH-sensitive core-shell nanogels were synthesized based on N-isopropylacrylamide and methacryloxy benzoic acid and PEG (core) as a crosslinker. With the use of another crosslinker, such as 9-divynil-2,4,8,10 tetraoxaspirol (5,5\({}^{\prime}\))-undecane (DVA), the nanogels were reduced in size to around 100 nm. The empty nanogels were biocompatible with a lung cancer cell line (NCl H1437), while the DOX-loaded DVA-crosslinked nanogels resulted in efficient cytotoxicity for that cell line [118]. Hydrogels and nanogels offer a versatile platform for the therapy of several diseases, particularly cancers. With subtle improvements, they could become exceptional drug delivery vehicles. Their main characteristics are biocompatibility, biodegradability, high drug loading capacity, and colloidal stability. It is also important to know that some are double- and triple-stimuli sensitive.