Preparation of pH-sensitive carboxymethyl cellulose/chitosan/alginate hydrogel beads with reticulated shell structure to deliver Bacillus subtilis natto

pH-sensitive hydrogels have been applied in delivering probiotics and drugs. However, pH sensitivity has been found to be contradictory with structural stability in hydrogel preparation. In this work, a novel strategy based on two systems of sodium carboxymethyl cellulose (CMC)/chitosan (CS) and sodium alginate (SA)/calcium chloride was designed to construct a reticulated shell structure stable for 3 h in simulated gastric fluid (pH 1.2) but began to break up at 2 h in simulated intestinal fluid (pH 6.8), exhibiting obvious pH sensitivity. The embedding rate of Bacillus subtilis natto reached to 67.3%, and the sustained release lasted for more than 10 h. It is implicated that the reticulated shell structure has harmoniously balanced the two incompatible properties of pH sensitivity and sustained release of CMC/CS/SA beads.