Inulinase immobilization on polyethylene glycol/polypyrrole multiwall carbon nanotubes producing a catalyst with enhanced thermal and operational stability.

This paper describes the development of a simple method for mixed non-covalent and covalent bonding of partially purified inulinase on functionalized multiwall carbon nanotubes (f-MWCNTs) with polypyrrole (PPy). The pyrrole (Py) was electrochemically polymerized on MWCNTs in order to fabricate MWCNTs/PPy nanocomposite. Two multiple forms of enzyme were bound to N-H functional groups from PPy and -COO- from activated MWCNTs to yield a stable MWCNTs/PPy/PEG immobilized preparation with increased thermal stability. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) were used to confirm functionalization of nanoparticles and immobilization of the enzyme. The immobilization yield of 85% and optimal enzyme load of 345 µg protein onto MWCNTs was obtained. The optimum reaction conditions and kinetic parameters were established using the UV-Vis analytical assay. The best functional performance for prepared heterogeneous catalyst has been observed at pH 3.6 and 10, and at the temperatures of 60 and 80ºC. The half-life (t 1/2) of the immobilized inulinase at 60 and 80ºC was found to be 231 and 99 min, respectively. The reusability of the immobilized formulation was evaluated based on a method in which the enzyme retained 50% of its initial activity, which occurred after the eighteenth operation cycle.

Hydrofluoric Acid: Burns and Systemic Toxicity, Protective Measures, Immediate and Hospital Medical Treatment.

BACKGROUND: Hydrofluoric acid is a commonly used chemical in many industrial branches, but it can also be found as an ingredient in household products such as cleaning agents. Possessing high corrosive potential, HF acid causes burns and tissue necrosis, while when absorbed and distributed through the bloodstream, its extremely high toxic potential is expressed. Acute symptoms are often followed by pain, particularly in the case of skin burns, which intensiveness does not often correlate with the expressiveness of the clinical findings. Even exposure to low-concentrated solutions or gasses, or low-doses of high-concentrated acid, may provoke delayed systemic disorder which may eventually have a lethal outcome. AIM: Therefore, having information regarding the possible hazardous effects of hydrofluoric acid usage, a variety of symptoms, as well as a treatment approach, is of great importance in the case of HF exposure. METHODS: Available scientific articles published in literature databases, scientific reports and governmental recommendations from the internet websites, written in English, using the following search terms "Hydrofluoric acid, skin burns, eye injury, ingestion, inhalation, systemic toxicity, decontamination, antidote, medical treatment" have been reviewed. RESULTS: This review is useful not only for physicians but for everyone who may come in contact with a person exposed to HF acid. CONCLUSION: It highlights the mechanism of action, presents the acute and chronic symptoms, personal and general protective measures and devices that should be used, as well as decontamination procedures, immediate, antidote and hospital medical treatment.

Contemporary Dental Ceramic Materials, A Review: Chemical Composition, Physical and Mechanical Properties, Indications for Use.

BACKGROUND: The high esthetic expectations from the prosthodontic restorations have directed the qualitative development of the materials towards the all-ceramic materials that are capable of replacing porcelain-fused-to-metal systems. AIM: This article reviews the literature covering the contemporary all-ceramic materials and systems with a focus on the chemical composition and materials' properties; also it provides clinical recommendations for their use. RESULTS: The glass-matrix ceramics and polycrystalline ceramics are presented, as well as recently introduced machinable materials, all-zirconia and resin-matrix ceramics. The specific properties of zirconia, such as transformation toughening, stabilisation of the crystallographic structure, low-temperature degradation and factors affecting the zirconia's ageing, are emphasised. CONCLUSION: The favourable properties of the resin-matrix ceramics, such as modulus of elasticity similar to dentin, shock-absorbing characteristics and high resilience and fracture resistance, are also covered in this article.

Acid Etching as Surface Treatment Method for Luting of Glass-Ceramic Restorations, part 1: Acids, Application Protocol and Etching Effectiveness.

AIM: The purpose of this review is to represent acids that can be used as surface etchant before adhesive luting of ceramic restorations, placement of orthodontic brackets or repair of chipped porcelain restorations. Chemical reactions, application protocol, and etching effect are presented as well. STUDY SELECTION: Available scientific articles published in PubMed and Scopus literature databases, scientific reports and manufacturers' instructions and product information from internet websites, written in English, using following search terms: "acid etching, ceramic surface treatment, hydrofluoric acid, acidulated phosphate fluoride, ammonium hydrogen bifluoride", have been reviewed. RESULTS: There are several acids with fluoride ion in their composition that can be used as ceramic surface etchants. The etching effect depends on the acid type and its concentration, etching time, as well as ceramic type. The most effective etching pattern is achieved when using hydrofluoric acid; the numerous micropores and channels of different sizes, honeycomb-like appearance, extruded crystals or scattered irregular ceramic particles, depending on the ceramic type, have been detected on the etched surfaces. CONCLUSION: Acid etching of the bonding surface of glass - ceramic restorations is considered as the most effective treatment method that provides a reliable bond with composite cement. Selective removing of the glassy matrix of silicate ceramics results in a micromorphological three-dimensional porous surface that allows micromechanical interlocking of the luting composite.

Lactobacillus casei Encapsulated in Soy Protein Isolate and Alginate Microparticles Prepared by Spray Drying.

This article presents a novel formulation for preparation of Lactobacillus casei 01 encapsulated in soy protein isolate and alginate microparticles using spray drying method. A response surface methodology was used to optimise the formulation and the central composite face-centered design was applied to study the effects of critical material attributes and process parameters on viability of the probiotic after microencapsulation and in simulated gastrointestinal conditions. Spherical microparticles were produced in high yield (64%), narrow size distribution (d50=9.7 µm, span=0.47) and favourable mucoadhesive properties, with viability of the probiotic of 11.67, 10.05, 9.47 and 9.20 log CFU/g after microencapsulation, 3 h in simulated gastric and intestinal conditions and four-month cold storage, respectively. Fourier-transform infrared spectroscopy confirmed the probiotic stability after microencapsulation, while differential scanning calorimetry and thermogravimetry pointed to high thermal stability of the soy protein isolate-alginate microparticles with encapsulated probiotic. These favourable properties of the probiotic microparticles make them suitable for incorporation into functional food or pharmaceutical products.

Enhanced model for determining the number of graphene layers and their distribution from X-ray diffraction data.

A model consisting of an equation that includes graphene thickness distribution is used to calculate theoretical 002 X-ray diffraction (XRD) peak intensities. An analysis was performed upon graphene samples produced by two different electrochemical procedures: electrolysis in aqueous electrolyte and electrolysis in molten salts, both using a nonstationary current regime. Herein, the model is enhanced by a partitioning of the corresponding 2θ interval, resulting in significantly improved accuracy of the results. The model curves obtained exhibit excellent fitting to the XRD intensities curves of the studied graphene samples. The employed equation parameters make it possible to calculate the j-layer graphene region coverage of the graphene samples, and hence the number of graphene layers. The results of the thorough analysis are in agreement with the calculated number of graphene layers from Raman spectra C-peak position values and indicate that the graphene samples studied are few-layered.

Optimization of the formulation for preparing Lactobacillus casei loaded whey protein-Ca-alginate microparticles using full-factorial design.

CONTEXT: This article presents specific approach for microencapsulation of Lactobacillus casei using emulsion method followed by additional coating with whey protein. METHODS: Experimental design was employed using polynomial regression model at 2nd level with three independent variables, concentrations of alginate, whey protein and CaCl2. Physicochemical, biopharmaceutical and biological properties were investigated. RESULTS: In 11 series generated, negatively charged microparticles were obtained, with size 6.99-9.88 µm, Ca-content 0.29-0.47 mg per 10 mg microparticles, and viability of the probiotic 9.30-10.87 log10CFU/g. The viability after 24 hours in simulated gastrointestinal conditions was between 3.60 and 8.32 log10CFU/g. DISCUSSION: Optimal formulation of the microparticles that ensures survival of the probiotic and achieves controlled delivery was determined: 2.5% (w/w) alginate, 3% (w/w) CaCl2 and 3% (w/w) whey protein. CONCLUSION: The advantageous properties of the L. casei-loaded microparticles make them suitable for incorporation in functional food and/or pharmaceutical products.