pH‐Responsive Poly(methacrylic acid)‐Grafted Hollow Silica Vesicles

Abstract

Poly(methacrylic acid)-grafted hollow silica vesicles (PMAA-g-hollow silica vesicles) were obtained through a grafting-from approach. PMAA brushes were formed by performing atom-transfer radical polymerisation of sodium methacrylate with an initiator attached to the hollow silica spheres. PMAA-g-hollow silica vesicles were characterised by using TEM, thermogravimetric analysis (TGA) and FTIR spectroscopy. pH-dependent ξ potential and (1)H NMR spectra of PMAA-g-hollow silica vesicles were measured, and the results indicated that MAA brushes in PMAA-g-hollow silica vesicles had a lower ionisation degree and low solubility in acidic aqueous solution, for example, pH 3.4, but a higher ionisation degree and high solubility when the pH was higher than 7. Also it was demonstrated that calcein blue and fluorescein isothiocyanate (FITC) labelled dextran (M(n):10 kDa) could be encapsulated in the interiors of the PMAA-g-hollow silica vesicles with a negligible amount in PMAA brushes at pH 2, and pH-triggered release of calcein blue and FITC-labelled dextran from PMAA-g-hollow silica vesicles was observed at pH 7.4.

A Rocket‐Like Encapsulation and Delivery System with Two‐Stage Booster Layers: pH‐Responsive Poly(methacrylic acid)/Poly(ethylene glycol) Complex‐Coated Hollow Silica Vesicles

“…Figure B(a,b) shows 1 H NMR spectra of the solution obtained at pH 8.9 and 2.6, respectively. When pH is adjusted from pH 8.9 to 2.6, the peaks attributed to the protons of PMAA become broader and shift downfield similar to what was observed for PMAA‐g‐hollow silica vesicles . Quantitatively, the integral intensity of the peaks attributed to the protons of PMAA decreases from 10.3 to 4.8 by 215%, which was determined using dimethylsulfoxide (DMSO) as an external reference.…”

“…Quantitatively, the integral intensity of the peaks attributed to the protons of PMAA decreases from 10.3 to 4.8 by 215%, which was determined using dimethylsulfoxide (DMSO) as an external reference. In contrast, the decrease in the integral intensity of the peaks attributed to the protons of PMAA in PMAA‐g‐hollow silica vesicles is by 181% . This suggests that the chain mobility of PMAA in the PMAA/PEG complex layers is lower than those in the PMAA layers formed on the surfaces of hollow silica spheres under an acidic condition.…”

“…Because only the protons of the polymer segments with a high mobility in a solution can be observed in 1 H NMR spectrum, the effects of the formation of PMAA/PEG complex on the chain mobility of PMAA and PEG can be investigated using 1 H NMR. In a typical process, sodium PMAA with of 6.5 kDa and PEG‐g‐hollow silica vesicles were mixed in D 2 O at pH 8.9 with a molar ratio of MAA unit to EG unit at 1:1 followed by adjusting pH to 2.6.…”

“…This indicates that the PMAA/PEG complex reduces the mobility of the whole PEG brushes significantly. Hence, it can be expected that the first booster layer consisting of PMAA/PEG complex can provide more secure encapsulation than PMAA layers only in PMAA‐g‐hollow silica vesicles . Furthermore, the formation of PMAA/PEG complex via hydrogen bonding on the surfaces of hollow silica spheres was investigated using FTIR.…”

pH‐ and Redox‐Responsive Poly(ethylene glycol) and Cholesterol‐Conjugated Poly(amido amine)s Based Micelles for Controlled Drug Delivery

“…DLS measurement illustrated that the micelles in aqueous solution have an average hydrodynamic diameter of 135.7 ± 13.6 nm, which is larger than the micelles in a dry state observed in TEM probably due to swelling of micelles. Since only the protons of polymer segments with a high solution mobility can be observed in solution 1 H NMR spectrum, solution 1 H NMR spectra were used to get more information of the micelles formed. Figure d shows the 1 H NMR spectrum of poly(BAC‐AMPD)‐ g ‐PEG‐ g ‐CE in D 2 O.…”