title: Sol-gel encapsulation of binary Zn(II) compounds in silica nanoparticles. Structure-activity correlations in hybrid materials targeting Zn(II) antibacterial use.
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.
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Halevas
authors.affiliation: 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.
authors.forename: C M
authors.initials: CM
authors.lastname: Nday
authors.affiliation: Laboratory of Analytical Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Kaprara
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, N.C.S.R. "Demokritos", Aghia Paraskevi 15310, Attiki, Greece.
authors.forename: V
authors.initials: V
authors.lastname: Psycharis
authors.affiliation: Institute of Advanced Materials, Physicochemical Processes, Nanotechnology and Microsystems, N.C.S.R. "Demokritos", Aghia Paraskevi 15310, Attiki, Greece.
authors.forename: C P
authors.initials: CP
authors.lastname: Raptopoulou
authors.affiliation: Department of Chemistry, University of Cape Town, Rondebosch 7700, Cape Town, South Africa.
authors.forename: G E
authors.initials: GE
authors.lastname: Jackson
authors.affiliation: Laboratory of Materials for Electrotechnics, Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Litsardakis
authors.affiliation: Laboratory of Inorganic Chemistry, Department of Chemical Engineering, Aristotle University of Thessaloniki, Thessaloniki 54124, Greece. Electronic address: salif@auth.gr.
authors.forename: A
authors.initials: A
authors.lastname: Salifoglou
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry* / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D002625:Chemistry, Organic; D018360:Crystallography, X-Ray; D016503:Drug Delivery Systems; D005782:Gels / Q000737:chemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008826:Microbial Sensitivity Tests; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry*; D019904:Polymethyl Methacrylate / Q000737:chemistry; D012545:Schiff Bases / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry*; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry*
chemical_list: D000890:Anti-Infective Agents; D005782:Gels; D008024:Ligands; D012545:Schiff Bases; D012822:Silicon Dioxide; D019904:Polymethyl Methacrylate; D015032:Zinc
keywords: Antibacterial activity; Binary Zn(II)-Schiff materials; Microorganisms; Nanoparticles; Sol–gel encapsulation-release