Cerium dioxide (CeO2) finds applications in areas such as corrosion protection, solar cells, or catalysis, finding increasing applications in biomedicine. This work reports on surface-modified CeO2 ...particles in order to tune their applicability in the biomedical field. Stable aqueous CeO2 sol, consisting of 3–4 nm in size crystallites, was synthesized using forced hydrolysis. The coordination of catecholate-type of ligands (catechol, caffeic acid, tiron, and dopamine) to the surface-Ce atoms is followed with the appearance of absorption in the visible spectral range as a consequence of interfacial charge-transfer complex formation. The spectroscopic observations are complemented with the density functional theory calculations using a cluster model. The synthesized samples were characterized by X-ray diffraction analysis, transmission electron microscopy, and nitrogen adsorption–desorption isotherms. The ζ-potential measurements indicated that the stability of CeO2 sol is preserved upon surface modification. The pristine CeO2 nanoparticles (NPs) are nontoxic against pre-osteoblast cells in the entire studied concentration range (up to 1.5 mM). Hybrid CeO2 NPs, capped with dopamine or caffeic acid, display toxic behavior for concentrations ≥0.17 and 1.5 mM, respectively. On the other hand, surface-modified CeO2 NPs with catechol and tiron promote the proliferation of pre-osteoblast cells.
Novel Zn-Co-CeO2 protective composite coatings were deposited successfully from chloride plating solutions. Two different types of ceria sources were used and compared: commercial ceria powder and ...home-made ceria sol. Electrodeposition was performed by a direct current in the range of 1–8 A dm−2. Two different agitation modes were used and compared, magnetic stirring and ultrasound-assisted stirring (US). The influence of magnetic stirring on the stability of the related plating baths was evaluated via a dynamic scattering method. The results pointed to better stability of the prepared ceria sol. The morphology of the composite coatings was examined by scanning electron microscopy (SEM), and particle content was determined by energy-dispersive X-ray spectroscopy (EDS). The results showed that the increase in the deposition current density was not beneficial to the coating morphology and particle content. The corrosion behavior of the Zn-Co-CeO2 composite coatings was analyzed and compared by electrochemical impedance spectroscopy and polarization resistance. The ultrasound-assisted electrodeposition at small current densities was favorable for obtaining composite coatings with enhanced corrosion stability. The protection was more effective when US was applied and, additionally, upon utilization of ceria sol as a particle source, which was revealed by higher polarization resistance and greater low-frequency impedance modulus values for sol-derived composite coatings deposited under ultrasound.
The sorption ability of biogenic hydroxyapatite (BHAP) towards heavy metal ions (Pb, Cu, Ni, Cd, and Zn) is compared with functionalized BHAP powders with caffeic acid (CA) and 3,4-dihydroxybenzoic ...acid (3,4-DHBA). The functionalization of the BHAP with either CA or 3,4-DHBA is indicated by the appearance of the colored powders due to the formation of the interfacial charge transfer (ICT) complexes. The detailed characterization of as-prepared and functionalized BHAP samples was performed using transmission electron microscopy, reflection spectroscopy, thermogravimetric analysis and determination of zeta potential. All three sorbents clearly displayed preferential sorption of Pb ions when the total concentration of multi-component equimolar solutions of heavy metal ions is high. It should be emphasized that the sorption capacity of functionalized BHAP with either CA or 3,4-BHAP was found to be higher, up to 60%, compared to as-prepared BHAP without the decrease of selectivity towards Pb ions.
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•AgNPs were synthesized electrochemically in poly(vinyl alcohol)/chitosan hydrogels.•AgNPs were smaller than 10 nm, which enhanced their antibacterial activity.•Non-cytotoxicity of ...AgNPs-containing hydrogels was confirmed by MTT test.•Nanocomposite hydrogels could be used as wound dressing materials.
In this work, we provide a facile path for the preparation of wound dressing materials with improved characteristics based on biocompatible chitosan and poly(vinyl alcohol) hydrogels with embedded silver nanoparticles (AgNPs) as a potent antimicrobial agent. The hydrogels were prepared via freezing-thawing method, whereas AgNPs were synthesized via an in situ electrochemical route. The excellent physicochemical properties of the obtained nanocomposite hydrogels were validated using different spectroscopic and microscopic techniques. The formation of sub-10 nm AgNPs was confirmed by UV–visible spectroscopy, dynamic light scattering and transmission electron microscopy. Swelling and silver release profiles were validated using several diffusion models. The hydrogels were proven to be non-cytotoxic using MTT test and possessed powerful antibacterial activity against Staphylococcus aureus and Escherichia coli, as determined by test in suspension, which affirmed their feasibility for wound dressing applications.
•Enhanced mechanical and thermal properties of PVA matrix with incorporated Gr.•Antibacterial activity of PVA/Gr nanocomposite against S. aureus.•PVA/Gr nanocomposite is noncytotoxic to healthy ...peripheral blood mononuclear cells.•High potential of PVA/Gr nanocomposite for biomedical applications.
Poly(vinyl alcohol)/graphene (PVA/Gr) nanocomposite was synthesized with the aim of developing a novel improved material. The PVA/Gr nanocomposite was characterized by UV–visible spectroscopy, cyclic voltammetry, Raman spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analyses, and the interaction of PVA molecules with graphene was examined. Introduction of Gr led to improved mechanical and thermal properties of the PVA/Gr nanocomposite compared to pure PVA, as well as strong antibacterial activity against the bacterial strain Staphylococcus aureus. The PVA/Gr nanocomposite was non-cytotoxic against healthy peripheral blood mononuclear cells by MTT assay, indicating its high potential for biomedical applications.
District heating systems are important utility systems. If these systems are properly managed, they can ensure economic and environmentally friendly provision of heat to connected customers. ...Potentials for further improvement of district heating systems' operation lie in the improvement of current control strategies. One of the options is the introduction of model predictive control. Multi-step ahead predictive models of consumers’ heat load are a starting point for creating a successful model predictive strategy. For the purpose of this article, short-term multi-step ahead predictive models of heat load of consumers connected to a district heating system were created. The models were developed using the novel method based on SVM (Support Vector Machines) coupled with a discrete wavelet transform. Nine different SVM-WAVELET predictive models for a time horizon from 1 to 24 h ahead were developed. Estimation and prediction results of the SVM-WAVELET models were compared with GP (genetic programming) and ANN (artificial neural network) models. The experimental results show that an improvement in predictive accuracy and capability of generalization can be achieved by the SVM-WAVELET approach in comparison with GP and ANN.
•District heating systems application for increasing in fuel efficiency.•Control and prediction of heat load for individual consumers in district heating systems.•Support vector machine application for district heating system control algorithm.
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•Polysaccharides (PS) levan and pullulan were hydrophobized by cholesterol.•New C60-PS non-covalent hybrid NPs were synthesized and studied by DLS and SEM.•The size of C60-PS NPs in ...water was reduced compared to starting PS NPs.•DPPH radical scavenging and β-carotene bleaching abilities of NPs were studied.•The antioxidant potency increases with the growing hydrophobicity.
An efficient encapsulation of the fullerene into two hydrophobized and one native polysaccharide provided water soluble supramolecular hybrids. After covalent modification of polysaccharides by cholesterol, noncovalent hybrids were prepared by a three-step procedure, including mixing of individual aqueous solutions of hydrophobized, as well as native sugar with solution of the fullerene in pyridine, dialysis and lyophilization. Although the degree of the fullerene incorporation into hydrophobized substrates, cholesterol-levan and cholesterol-pullulan, was lower in comparison to the native polysaccharide levan, hydrophobization provided nanoparticles with improved properties. The particle size distribution, studied by dynamic light scattering and scanning electron microscopy revealed formation of moderately polydisperse aggregates, with the diameter contraction in comparison to the corresponding free polysaccharide, especially in the case of hydrophobized substrates. The morphological examination, done by scanning electron microscopy indicated the self-organization of the fullerene-native polysaccharide to round individual structures, while fullerene-hydrophobized polysaccharide hybrids tend to form networks. The antioxidant activity of the synthesized polysaccharide-C60 noncovalent hybrids versus starting polysaccharides was investigated by the DPPH radical scavenging and the β-carotene-linoleic acid bleaching methods. In all three complexes, the radical scavenging ability of the fullerene remained preserved, and a positive effect of levan hydrophobization was observed.
Fire blight disease, caused by plant pathogenic bacteria
Erwinia amylovora
represents a global threat for pome fruit industry, affecting yield and causing serious economic damage. During six year ...period (2011–2016), a total of 45 isolates typical for
E. amylovora
were isolated from four different host plants (apple, pear, quince and medlar) in 21 localities within four Serbian regions (Southeast, Central, West, and North). Isolates were primarily identified using biochemical and serological tests, polymerase chain reaction (PCR) with species-specific primer pair (A/B) and their pathogenicity. Polyclonal antibodies used in DAS ELISA and IF were found to be specific and sensitive enough for rapid
E. amylovora
detection. In virulence test performed on immature pear fruitlets, higher variability (CV) was found between regions than among hosts from which isolates originated. Slighter virulence of isolates originated from North region of Serbia (Vojvodina) was found in comparison to the isolates from Central Serbia, which were the most variable. Principal components analysis (PCA) segregated quince as a host among the most prevalent isolates in group of highly virulent, but failed to identify difference related to geographic origin of Serbian isolates. The same results enabled multivariate statistical analysis. Different DNA fingerprinting techniques such as repetitive element sequence based PCR (rep-) with BOX, ERIC, REP, GTG
5
and SERE primers, then Random Amplified Polymorphic DNA (RAPD) with M13-PCR primer revealed genetic homogeneity among all Serbian
E. amylovora
isolates. ERIC, SERE and M13 primers generated the most complex and visually perceptible patters. Restriction fragment length polymorphism analysis (RFLP) of
gyrA
and
recA
genes, digested with three restriction endonucleases
Bst
UI,
BgI
II and
Bsm
I and
rpoS
gene digested with
Bst
UI gave the unuque, characteristic patterns for all Serbian isolates.
The increased commercial use and spread of nanoceria raises concerns about the risks associated with its effects on living organisms. Although Pseudomonas aeruginosa may be ubiquitous in nature, it ...is largely found in locations closely linked with human activity. P. aeruginosa san ai was used as a model organism for a deeper understanding of the interaction between biomolecules of the bacteria with this intriguing nanomaterial. A comprehensive proteomics approach along with analysis of altered respiration and production of targeted/specific secondary metabolites was conducted to study the response of P. aeruginosa san ai to nanoceria. Quantitative proteomics found that proteins associated with redox homeostasis, biosynthesis of amino acids, and lipid catabolism were upregulated. Proteins from outer cellular structures were downregulated, including transporters responsible for peptides, sugars, amino acids and polyamines, and the crucial TolB protein of the Tol-Pal system, required for the structural formation of the outer membrane layer. In accordance with the altered redox homeostasis proteins, an increased amount of pyocyanin, a key redox shuttle, and the upregulation of the siderophore, pyoverdine, responsible for iron homeostasis, were found. Production of extracellular molecules, e.g. pyocyanin, pyoverdine, exopolysaccharides, lipase, and alkaline protease, was significantly increased in P. aeruginosa san ai exposed to nanoceria. Overall, nanoceria at sublethal concentrations induces profound metabolic changes in P. aeruginosa san ai and provokes increased secretion of extracellular virulence factors, revealing the powerful influence this nanomaterial has on the vital functions of the microorganism.
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