Interactions in aromatic probe molecule loaded poly(N-isopropylacrylamide) hydrogels and implications for drug delivery

Phenol-Induced Isothermal Shape Change of Poly(N-isopropylacrylamide-co-acrylamide) Hydrogel

Interactions between phenols and poly(N-isopropylacrylamide) hydrogels have attracted considerable interest due to their potential applications in various fields. In this study, phenol-induced shape changes of poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-AAm)) hydrogels with gradient structures are investigated systematically. The P(NIPAM-co-AAm) hydrogel exhibits either bending or uniform shrinking behaviors in different aqueous solutions of phenol. The different shape-morphing behaviors of hydrogels in various phenols are related to the degree of phase transition and the elastic modulus. Phenols with a phenolic OH number less than or equal to 3 (such as phenol, gallic acid, and ethyl gallate) diffuse uniformly into the hydrogel network, resulting in hydrogel bending due to the heterogeneous phase transition of the network at both sides. In contrast, phenols with a phenolic OH group number greater than 3 (such as epigallocatechin gallate (EGCG), epigallocatechin, and tannic acid (TA)) interact strongly with the hydrogel network, causing the network at both sides to undergo the same phase transition and a larger elastic modulus, which leads to shrinkage without bending of the hydrogel. Moreover, P(NIPAM-co-AAm) hydrogels exhibit reversible and irreversible responsive characteristics in EGCG and TA solutions, respectively. We demonstrate the applications of phenol-induced phase transitions in P(NIPAM-co-AAm) hydrogels for phenolic-responsive grippers, shape reprogramming of hydrogel, and erasable information displays. The results provide useful insights to understand the interaction between phenols and PNIPAM hydrogels, thus shining light on their applications in soft robots, sensors, and information storage.

Brain delivery of antidotes by polymeric nanoparticles

Accidental intoxications from environmental pollutants, as well as intentional self- and chemical warfare-related poisonings affect millions of people worldwide each year. While many toxic agents can readily enter the central nervous system (CNS), the blood-brain barrier (BBB) prevents the brain uptake of most pharmaceuticals. Consequently, poisoning antidotes usually cannot reach their site of action in the CNS in therapeutically relevant concentrations, and thus only provide effective protection to the peripheral nervous system. This limitation can be overcome by encapsulating the antidotes in nanoparticles (NP), which can enhance their CNS accumulation without damaging the integrity of the BBB. Among nanocarriers, polymer-based drug delivery systems exhibit remarkable benefits, such as bioavailability, cell uptake and tissue retention. Furthermore, due to their capacity to mask unfavorable physicochemical properties of cargo drugs, polymeric NPs were able to improve BBB transport of various pharmaceuticals. However, while polymer NP-mediated treatment of various pathological brain conditions, such as glioma and Alzheimer's disease were exhaustively studied, the application of polymeric nanocarriers for brain-targeted delivery of antidote molecules has not been adequately examined. To display its therapeutic potential, we review the state of the art of polymer NP-assisted CNS delivery of antidotes for various poisonings, including heavy metal and organophosphorus intoxications.