Hollow mesoporous silica capsules loaded with copper, silver, and zinc oxide nanoclusters for sustained antibacterial efficacy

Abstract

Intensive and overuse of antibiotics during the last years has triggered a distinct rise in antibiotic resistance worldwide. In addition to the newly developed antimicrobials, there is a high demand for alternative treatment options against persistent bacterial infections. The biocidal impact of transition metal ions like copper (Cu 2+ ), silver (Ag + ), and zinc (Zn 2+ ) also known as oligodynamic effect has been used through ages to kill or inhibit the growth of microorganisms and to employ long-term prevention strategies against their biological antagonists. Herein, we report on the synthesis of Cu, Ag and Zn metal Accepted ArticleThis article is protected by copyright. All rights reserved and corresponding oxide nanoparticles immobilized on hollow mesoporous silica capsules (HMSCs) obtained by a hard-template assisted sol-gel synthesis followed by reduction of appropriate metal salts in the presence of HMSCs. Compartmentalization of nanosized metal and oxide clusters in Ag@HMSCs, Cu@HMSCs and ZnO@HMSCs particles prevented their agglomeration and offered a high release kinetics of metal ions between 2.0-3.7 mM during 24 hours, as monitored by UV-vis analyses. The distribution and morphology of pristine and metal functionalized HMSCs was evaluated by transmission electron microscopy (TEM) analysis revealing the successful synthesis of Ag, Cu and ZnO nanoparticles supported on HMSCs. X-ray photoelectron spectroscopy (XPS) revealed that mainly Cu(II), Ag(0) and Zn(II) species were present in the modified HMSCs. In addition to the surface attachment of preformed metal (Ag and Cu) and metal oxide (ZnO) cluster, nucleation of metal nanoparticles inside the void of HMSCs provided an internal reservoir which allowed for a time-dependent release of metal ions through slower dissolution rates leading to a long-term and sustained bacterial inhibition over several hours. The high antimicrobial efficiency of Ag@HMSCs, Cu@HMSCs, and ZnO@HMSCs particles was investigated towards both Grampositive (B. subtilis) and Gram-negative (E. coli) bacteria by INT assays showing a complete growth inhibition for both bacteria types after 24 hours. While Ag@HMSCs and Cu@HMSCs showed a higher susceptibility against Gram-negative bacteria, ZnO@HMSCs showed a higher susceptibility against Grampositive bacteria. This demonstrates the promise of metal-loaded capsules as antibacterial delivery vehicles with dual-mode time release profiles being potential alternatives for antibiotic drugs.

Carriers for hydrophobic drug molecules: lipid-coated hollow mesoporous silica particles, and the influence of shape and size on encapsulation efficiency

“…3). 32 The FTIR analysis showed absorption bands at 1073 cm −1 , 960 cm −1 , and 800 cm −1 corresponding to Si–O–Si stretches (Fig. 4).…”

“…(Figure 2, S2) The etching process offered purified amorphous mesoporous nanocarriers (nanocubes and nanocapsules), demonstrating the complete removal of crystalline Fe2O3 nanoparticles (Figure 3). 32 The FTIR analysis showed absorption bands at 1073 cm -1 , 960 cm -1 , and 800 cm -1 corresponding to Si-O-Si stretches (Figure 4). 33,34 Page 4 of 32 Nanoscale volume for all nanocarriers.…”

Multifunctional mesoporous silica nanoparticles for biomedical applications

“…There is a wide variety of nanocomposites formed by metal compound NPs with MSNs, and the available noble metal-free elements include 13 elements, such as calcium (Ca), 151,152 titanium (Ti), 153,154 vanadium (V), 155,156 manganese (Mn), 157,158 iron (Fe), 159,160 cobalt (Co), 161 copper (Cu), 162,163 zinc (Zn), 164,165 Niobium (Nb), 166,167 molybdenum (Mo), 168,169 cadmium (Cd), 51,170 iridium (Ir), 171 and bismuth (Bi) 172,173 (Fig. 4b).…”