Monoolein cubic phase incorporating poly(dimethylaminoethyl methacrylate-co-phenyl vinyl sulfide) and its hydrogen peroxide, temperature, and near infrared-responsive release properties

Abstract

Monoolein cubic phase incorporating poly(dimethylaminoethyl methacrylate-co-phenyl vinyl sulfide) (P(DMAEMA-co-PVS)) and indocyanine green (ICG, a photosensitizer) was prepared as a multiple-responsive carrier. P(DMAEMA-co-PVS), prepared by a free radical polymerization, was air/water interface-active and it exhibited lower critical solution temperature (LCST). The polymer increased in its LCST by H2O2 treatment, possibly because of the hydrolytic detachment of DMAEMA pendant, evidenced by 1H NMR and FT-IR spectroscopy. Water channels surrounded by lipid matrix, characteristic of cubic phase, was observed on TEM photos and the inclusion of the additives (e.g., P(DMAEMA-co-PVS) had little effect on the structure. The cubic phases increased their thermal stability upon the inclusion of the polymer chains and they maintained their integrity once the temperature was kept below 60 °C, supported by the polarized optical microscopy and the differential scanning calorimetry. The release of a cargo (i.e., fluorescent dextran) was suppressed at body temperature (37 °C) at the H2O2 concentration of normal tissue (e.g., 0.000002%), possibly due to an entangled network structure formed by the thermally induced inter/intramolecular hydrophobic interaction of the polymer chains. The release was markedly promoted at the H2O2 concentration of tumor tissue (e.g., 0.0034%), possibly because the thermally induced hydrophobic interaction can be weakened by the hydrolytic degradation. In addition, the release was significantly enhanced by NIR irradiation. The cubic phase would be used as a drug carrier which releases its payload at a target site in a selected manner in answering to H2O2 and NIR irradiation.