Fabrication of large pore mesoporous silica microspheres by salt-assisted spray-drying method for enhanced antibacterial activity and pancreatic cancer treatment

Large-pore mesoporous silica (LPMS) microspheres with tunable pore size have received intensive interest in the field of drug delivery due to their high storage capacity and fast delivery rate of drugs. In this work, a facile salt-assisted spray-drying method has been developed to fabricate LPMS microspheres using continuous spray-drying of simple inorganic salts as pore templates and colloidal SiO₂ nanoparticles as building blocks, followed by washing with water to remove the templates. More importantly, the porosity of the LPMS microspheres can be finely tuned by adjusting the furnace temperature and relative concentration of the salt to SiO₂, which could lead to optimal pharmaceutical outcomes. Then, the biological roles of these LPMS microspheres were evaluated in antibacterial and cancer therapy. In this regard, rhodamine b as a probe was initially loaded inside the LPMS microspheres. The obtained particles not only showed high entrapment efficiency (up to 30%) and a pH-responsive drug release but also presented pore-size-controlled drug release performance. Then, in vitro antibacterial activities of multiple antibiotics, namely nalidixic acid, chloramphenicol, and ciprofloxacin, loaded in the LPMS particles were investigated against two pathogenic bacteria, Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The results indicated bacterial inhibition up to 70% and 20% in less than 2 h for Escherichia coli and Staphylococcus aureus, respectively. This inhibition of bacterial growth was accompanied by no bacterial regrowth within 30 h. Finally, the versatility of LPMS microspheres as drug carriers in pancreatic cancer treatment was explored. In this regard, a pro-apoptotic NCL antagonist agent (N6L) as an antitumor agent was successfully loaded onto LPMS microspheres. Interestingly, the resulting particles showed pore-size-dependent anticancer activity with inhibition of cancer cell growth up to 60%.