Blockchain Papers

Soumya Narayana, B.H. Jaswanth Gowda, Umme Hani, Mohammed Gulzar Ahmed · 6 authors

Hydrogels are innovative materials characterized by a water-swollen, crosslinked polymeric network capable of retaining substantial amounts of water while maintaining structural integrity. Their unique ability to swell or contract in response to environmental stimuli makes them integral to biomedical applications, including drug delivery, tissue engineering, and wound healing. Among these, "smart" hydrogels, sensitive to stimuli such as pH, temperature, and light, showcase reversible transitions between liquid and semi-solid states. Thermoresponsive hydrogels, exemplified by poly(N-isopropylacrylamide) (PNIPAM), are particularly notable for their sensitivity to temperature changes, transitioning near their lower critical solution temperature (LCST) of approximately 32 °C in water. Structurally, PNIPAM-based hydrogels (PNIPAM-HYDs) are chemically versatile, allowing for modifications that enhance biocompatibility and functional adaptability. These properties enable their application in diverse therapeutic areas such as cancer therapy, phototherapy, wound healing, and tissue engineering. In this review, the unique properties and behavior of smart PNIPAM are explored, with an emphasis on diverse synthesis methods and a brief note on biocompatibility. Furthermore, the structural and functional modifications of PNIPAM-HYDs are detailed, along with their biomedical applications in cancer therapy, phototherapy, wound healing, tissue engineering, skin conditions, ocular diseases, etc. Various delivery routes and patents highlighting therapeutic advancements are also examined. Finally, the future prospects of PNIPAM-HYDs remain promising, with ongoing research focused on enhancing their stability, responsiveness, and clinical applicability. Their continued development is expected to revolutionize biomedical technologies, paving the way for more efficient and targeted therapeutic solutions.

A. Schmalz, Holger Schmalz, Axel H. E. Müller

A series of smart hydrogels based on dual stimuli responsive star-block copolymers responding to pH and temperature were prepared via atom transfer radical polymerization (ATRP) employing the core-first method. They consist of poly(2-(dimethylamino)ethyl methacrylate) (PDMA) inner blocks and outer blocks comprised of poly(di(ethylene glycol) methyl ether methacrylate) (PDEGMA). The aggregation behavior of these block copolymer stars is analyzed by dependence on block length and arm number. The dual stimuli responsiveness of the stars is demonstrated by turbidity as well as dynamic light scattering on dilute aqueous solution, and the gelation behavior of concentrated aqueous solutions is studied by rheology. Above the transition temperature of the PDEGMA outer blocks the stars form flower-like aggregates in dilute solution or free-standing gels at higher concentrations. When the temperature is increased further above the transition temperature of the PDMA inner block, the aggregates start to contract and a weakening was observed for soft gels, whereas for strong gels no influence on the moduli was detected. The behavior is controlled by both concentration and pH value. In addition, we show that the minimum polymer concentration for gel formation can be lowered by quaternizing the inner block of the stars, but a second response to stimuli is lost during the procedure.