A smart hydrogel-based time bomb triggers drug release mediated by pH-jump reaction

• Published in: Science and technology of advanced materials Vol. 13; no. 6; p. 064202
• Main Authors: Techawanitchai, Prapatsorn, Idota, Naokazu, Uto, Koichiro, Ebara, Mitsuhiro, Aoyagi, Takao
• Format: Journal Article
• Language: English
• Published: United States Taylor & Francis 01-12-2012; IOP Publishing; Taylor & Francis Ltd; Taylor & Francis Group
• Subjects: Diffusion; Dihydroxyphenylalanine; Drug delivery systems; Focus Papers; Hydrogels; Irradiation; Isopropylacrylamide; pH-jump reaction; pH-responsive hydrogels; photoacid generators (PAGs); Protons; Reaction kinetics; smart polymers; time bomb; Ultraviolet radiation; pH-jump reaction; pH-responsive hydrogels; smart polymers; time bomb; photoacid generators (PAGs)
• ISSN: 1468-6996; 1878-5514
• DOI: 10.1088/1468-6996/13/6/064202

We demonstrate a timed explosive drug release from smart pH-responsive hydrogels by utilizing a phototriggered spatial pH-jump reaction. A photoinitiated proton-releasing reaction of o-nitrobenzaldehyde (o-NBA) was integrated into poly(N-isopropylacrylamide-co-2-carboxyisopropylacrylamide) (P(NIPAAm-co-CIPAAm)) hydrogels. o-NBA-hydrogels demonstrated the rapid release of protons upon UV irradiation, allowing the pH inside the gel to decrease to below the pK
a
value of P(NIPAAm-co-CIPAAm). The generated protons diffused gradually toward the non-illuminated area, and the diffusion kinetics could be controlled by adjusting the UV irradiation time and intensity. After irradiation, we observed the enhanced release of entrapped L-3,4-dihydroxyphenylalanine (DOPA) from the gels, which was driven by the dissociation of DOPA from CIPAAm. Local UV irradiation also triggered the release of DOPA from the non-illuminated area in the gel via the diffusion of protons. Conventional systems can activate only the illuminated region, and their response is discontinuous when the light is turned off. The ability of the proposed pH-jump system to permit gradual activation via proton diffusion may be beneficial for the design of predictive and programmable devices for drug delivery.