Preparation of degradable magnetic temperature- and redox-responsive polymeric/Fe3O4 nanocomposite nanogels in inverse miniemulsions for loading and release of 5-fluorouracil

Nanogels are nanosized crosslinked polymer networks capable of absorbing large quantities of water. Specifically, smart nanogels are interesting because of their ability to respond to biomedically relevant changes like pH, temperature, etc. In the last few decades, hybrid nanogels or composites have been developed to overcome the ever increasing demand for new materials in this field. In this context, a hybrid refers to nanogels combined with different polymers and/or with nanoparticles such as plasmonic, magnetic, and carbonaceous nanoparticles, among others. Research activities are focused nowadays on using multifunctional hybrid nanogels in nanomedicine, not only as drug carriers but also as imaging and theranostic agents. In this review, we will describe nanogels, particularly in the form of composites or hybrids applied in nanomedicine.

The miniemulsion process allows the formation of complex structured polymeric nanoparticles and the encapsulation of a solid or liquid, an inorganic or organic, or a hydrophobic or hydrophilic material into a polymer shell. Many different materials, ranging from organic and inorganic pigments, magnetite, or other solid nanoparticles, to hydrophobic and hydrophilic liquids, such as fragrances, drugs, or photoinitators, can be encapsulated. Functionalization of the nanoparticles can also be easily obtained. Compared to polymerization processes in organic solvents, polymerization to obtain polymeric nanoparticles can be performed in environmentally friendly solvents, usually water.

This review summarises smart thermo-responsive polymeric materials with reversible and ‘on–off’ remotely switchable properties for a wide range of biomedical and biomaterials applications. The drastic development of polymeric materials for a wide range of biomedical and biomaterial applications has been explored in the last few decades. Among these materials, a new class of ‘smart’ or ‘intelligent’ biomaterial has been developed, and these materials are highly responsive to slight changes in their environments. Due to their dynamically alterable properties, smart materials allow for smart biomaterials to be developed. This review presents smart thermo-responsive polymers and discusses how they may be used as smart biomaterials. We describe typical thermo-responsive polymers that are either lower critical solution temperature-type, upper critical solution temperature-type, or thermo-induced shape-memory polymers. The basic mechanisms of the thermo-response processes will also be described. The applications of smart biomaterials with various forms, such as smart fibres, surfaces and hydrogels, will also be introduced.