Sol-gel encapsulation of binary Zn(II) compounds in silica nanoparticles. Structure-activity correlations in hybrid materials targeting Zn(II) antibacterial use

E Halevas; C M Nday; E Kaprara; V Psycharis; C P Raptopoulou; G E Jackson; G Litsardakis; A Salifoglou

doi:10.1016/j.jinorgbio.2015.06.004

Sol-gel encapsulation of binary Zn(II) compounds in silica nanoparticles. Structure-activity correlations in hybrid materials targeting Zn(II) antibacterial use

J Inorg Biochem. 2015 Oct:151:150-63. doi: 10.1016/j.jinorgbio.2015.06.004. Epub 2015 Jun 6.

Authors

E Halevas¹, C M Nday², E Kaprara³, V Psycharis⁴, C P Raptopoulou⁴, G E Jackson⁵, G Litsardakis⁶, A Salifoglou⁷

Affiliations

¹ Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
² Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece; Department of Chemistry, University of Cape Town, Rondebosch 7700, Cape Town, South Africa.
³ Laboratory of Analytical Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
⁴ Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, N.C.S.R. "Demokritos", Aghia Paraskevi 15310, Attiki, Greece.
⁵ Department of Chemistry, University of Cape Town, Rondebosch 7700, Cape Town, South Africa.
⁶ Laboratory of Materials for Electrotechnics, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
⁷ Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. Electronic address: salif@auth.gr.

PMID: 26198972
DOI: 10.1016/j.jinorgbio.2015.06.004

Abstract

In the emerging issue of enhanced multi-resistant properties in infectious pathogens, new nanomaterials with optimally efficient antibacterial activity and lower toxicity than other species attract considerable research interest. In an effort to develop such efficient antibacterials, we a) synthesized acid-catalyzed silica-gel matrices, b) evaluated the suitability of these matrices as potential carrier materials for controlled release of ZnSO4 and a new Zn(II) binary complex with a suitably designed well-defined Schiff base, and c) investigated structural and textural properties of the nanomaterials. Physicochemical characterization of the (empty-loaded) silica-nanoparticles led to an optimized material configuration linked to the delivery of the encapsulated antibacterial zinc load. Entrapment and drug release studies showed the competence of hybrid nanoparticles with respect to the a) zinc loading capacity, b) congruence with zinc physicochemical attributes, and c) release profile of their zinc load. The material antimicrobial properties were demonstrated against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and negative (Escherichia coli, Pseudomonas aeruginosa, Xanthomonas campestris) bacteria using modified agar diffusion methods. ZnSO4 showed less extensive antimicrobial behavior compared to Zn(II)-Schiff, implying that the Zn(II)-bound ligand enhances zinc antimicrobial properties. All zinc-loaded nanoparticles were less antimicrobially active than zinc compounds alone, as encapsulation controls their release, thereby attenuating their antimicrobial activity. To this end, as the amount of loaded zinc increases, the antimicrobial behavior of the nano-agent improves. Collectively, for the first time, sol-gel zinc-loaded silica-nanoparticles were shown to exhibit well-defined antimicrobial activity, justifying due attention to further development of antibacterial nanotechnology.

Keywords: Antibacterial activity; Binary Zn(II)-Schiff materials; Microorganisms; Nanoparticles; Sol–gel encapsulation-release.

MeSH terms

Anti-Infective Agents / chemistry*
Anti-Infective Agents / pharmacology
Bacteria / drug effects
Chemistry, Organic
Crystallography, X-Ray
Drug Delivery Systems*
Gels / chemistry
Ligands
Magnetic Resonance Spectroscopy
Microbial Sensitivity Tests
Microscopy, Electron, Transmission
Molecular Structure
Nanoparticles / chemistry*
Polymethyl Methacrylate / chemistry
Schiff Bases / chemistry
Silicon Dioxide / chemistry*
Structure-Activity Relationship
X-Ray Diffraction
Zinc / chemistry*

Substances

Anti-Infective Agents
Gels
Ligands
Schiff Bases
Silicon Dioxide
Polymethyl Methacrylate
Zinc