RSC Adv., 2015,5,30023

Elucidation of acid strength effect on ibuprofen
adsorption and release by aluminated mesoporous
silica nanoparticles†

Mesoporous silica nanoparticles (MSN) with 1–10 wt% loading of aluminum (Al) were prepared and
characterized by XRD, N2 physisorption, 29Si and 27Al NMR, FT-IR and FT-IR preadsorbed pyridine. All
samples were evaluated for ibuprofen adsorption and release. The results showed that MSN gave almost
complete ibuprofen adsorption while the addition of 1, 5, and 10 wt% Al onto MSN (1Al-MSN, 5Al-MSN
and 10Al-MSN) resulted in 35%, 58%, and 79% of adsorption, respectively. The characterization results
elucidated that the highest adsorptivity of MSN was due to its highest surface silanol groups, while the
increase in Br¨onsted acidity upon loading of Al provided more adsorption sites for the higher activity.
Regardless of its highest adsorption capacity, MSN demonstrated the highest and fastest release (100%)
in 10 h, followed by 1Al-MSN, 5Al-MSN and 10Al-MSN. The increase in Al loading increased the acid sites
that hold the ibuprofen molecules, which raised the retention in ibuprofen release. The pKa of Si–OH–Al
that is lower than Si–OH sites also attracted the ibuprofen more strongly, which resulted in the slower
release of Al-MSN as compared to MSN. The cytotoxicity study exhibited that ibuprofen loaded Al-MSN
was able to reduce the toxicity in the WRL-68 cells, verifying its ability to hold and slow the release of
ibuprofen as well as minimize the risk of drug overdose.