Hydrogels are materials with wide applications in several fields, including the biomedical and pharmaceutical industries. Their properties such as the capacity of absorbing great amounts of aqueous solutions without losing shape and mechanical properties, as well as loading drugs of different nature, including hydrophobic ones and biomolecules, give an idea of their versatility and promising demand. As they have been explored in a great number of studies for years, many routes of synthesis have been developed, especially for chemical/permanent hydrogels. In the same way, stimuli-responsive hydrogels, also known as intelligent materials, have been explored too, enhancing the regulation of properties such as targeting and drug release. By controlling the particle size, hydrogel on the micro- and nanoscale have been studied likewise and have increased, even more, the possibilities for applications of the so-called XXI century materials. In this paper, we aimed to produce an overview of the recent studies concerning methods of synthesis, biomedical, and pharmaceutical applications of macro-, micro, and nanogels.

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The application of polymers as medical devices has steadily increased in almost all medical fields because of the versatility of these materials. Thus, research has focused both on the development of more appropriate materials for specific situations and on the modification of already useful materials for the improvement of their intrinsic properties. Modifications on this kind of materials have increased their potential uses by adapting their mechanical properties to specific needs. Moreover, biocompatibility of the polymeric materials has been improved by the inclusion of certain functional groups, providing responses to physical and chemical stimuli present in physiological conditions.Until recently, one of the most worrying problems in hospitals has been infections derived from medical devices usage. Typically, this kind of infections was handled with the use of prophylactic and therapeutic treatments with 'classic' (low-molecular weight) antimicrobial agents. This strategy has been effective in most patients suffering from nosocomial infections. However, it has the disadvantage of substantially increasing the probability of antimicrobial-resistant pathogens appearance, which continue to be especially dangerous in hospital environments (Cohen et al., 2017; World Health Organization, n.d.;Zegers et al., 2017). Additionally, due to

The modification of medical devices is an area that has attracted a lot of attention in recent years; particularly, those developments which search to modify existing devices to render them antimicrobial. Most of these modifications involve at least two stages (modification of the base material with a polymer graft and immobilization of an antimicrobial agent) which are both time-consuming and complicate synthetic procedures; therefore, as an improvement, this project sought to produce antimicrobial silicone (PDMS) in a single step. Using gamma radiation as both an energy source for polymerization initiation and as a source of reducing agents in solution, PDMS was simultaneously grafted with acrylic acid and ethylene glycol dimethacrylate (AAc:EGDMA) while producing antimicrobial silver nanoparticles (AgNPs) onto the surface of the material. To obtain reproducible materials, experimental variables such as the effect of the dose, the intensity of radiation, and the concentration of the silver salt were evaluated, finding the optimal reaction conditions to obtain materials with valuable properties. The characterization of the material was performed using electronic microscopy and spectroscopic techniques such as 13C-CPMAS-SS-NMR and FTIR. Finally, these materials demonstrated good antimicrobial activity against S. aureus while retaining good cell viabilities (above 90%) for fibroblasts BALB/3T3.

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