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

Prapatsorn Techawanitchai*, Naokazu Idota, Koichiro Uto, Mitsuhiro Ebara, Takao Aoyagi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Citations (Scopus)


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 pKa 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.

Original languageEnglish
Article number064202
JournalScience and Technology of Advanced Materials
Issue number6
Publication statusPublished - 2012 Dec
Externally publishedYes


  • pH-jump reaction
  • pH-responsive hydrogels
  • photoacid generators (PAGs)
  • smart polymers
  • time bomb

ASJC Scopus subject areas

  • General Materials Science


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