Smart Ferrogels Based on pNIPAM and Polysaccharides for Controlled Uptake and Magnetically Triggered Release of Organic Probes

Poly( N -isopropylacrylamide) (pNIPAM) hydrogels are well-known stimuli-responsive materials, particularly attractive for remotely triggered release applications when combined with mechanisms that can activate their phase transition, such as magnetic nanoparticles (NPs). However, the underlying limitations of pure pNIPAM gels mean that reinforcing strategies must be introduced to exploit their full structural and functional potential. In this work, we prepared and characterized three thermoresponsive ferrogels based on pNIPAM reinforced with alginate, chitosan, or hydroxypropyl methylcellulose and loaded with iron oxide NPs. The NPs were synthesized by coprecipitation, functionalized to improve polymer compatibility, and incorporated during polymerization with the different polysaccharides. The resulting ferrogels successfully integrated both the NPs and the reinforcing polymers without significantly altering the thermoresponsive behavior of pNIPAM. We evaluated the adsorption and release performance of the ferrogels using two model organic probes. Uptake was strongly dependent on the polysaccharide present in the ferrogel, likely reflecting charge-based interactions between the probes and the polymeric network. Release could be triggered either by external heating in a water bath or by internal magnetic heating produced by an alternating field through the embedded NPs. Higher initial loading levels led to increased specific release, while absolute release values appeared nearly independent of the ferrogel–probe interactions. These results highlight the potential of reinforced ferrogels as magnetically triggered delivery systems, where the interaction with target molecules can be tuned by selecting appropriate polysaccharide components.