Mesoporous matrices for the delivery of the broad spectrum bacteriocin, nisin A

Mesoporous matrices of different pore size and chemical composition were explored as potential delivery matrices for the broad spectrum bacteriocin, nisin A. The adsorption of nisin A onto two mesoporous silicates (MPS - SBA-15, MCM-41) and two periodic mesoporous organosilanes (PMO - MSE, PMO-PA) was examined. It was found that hydrophobic interactions dominated in the adsorption of this peptide to the matrices, lending the highest adsorption to MCM-41 with a small pore size of 2.8 nm. The hydrophobic ethylene-bridged MSE (6 nm pore) improved the loading and protection of nisin A from degradation by a non-specific protease pepsin, over un-functionalised SBA-15 which had a slightly larger pore size and less hydrophobic moieties. Nisin A did not adsorb onto an amine-functionalised PMO. Upon suspension in modified fasted state simulated gastric fluid (pH 1.6), the highest release of nisin A was observed from MCM-41, with a lower release from SBA-15 and MSE, with release following Higuchi release kinetics. No release was detected into modified fasted state simulated intestinal fluid (pH 6.5) but despite this, the suspended matrices loaded with nisin A remained active against Staphylococcus aureus.