Immersion In Physiological Solution Research Articles

Surface modifications of biodegradable AZ31 alloy after immersion in physiological solution

Internal prosthesis and grafts are currently made of Ti alloys, stainless steels and Co–Cr alloys. In spite of excellent biocompatibility, they show some drawbacks that concern their mechanical properties (e.g. elastic modulus) and the need of secondary surgery for removing the implant. For this reason, a growing attention has been focused on biodegradable materials that can be absorbed into the body after tissue remodelling. In particular, Mg alloys are promising candidates for temporary implants thanks to their high biocompatibility, biodegradability and good mechanical properties that match those of human bone. In this work, the surface modifications of biodegradable AZ31 alloy were analysed after immersion for 15 days in a physiological solution (NaCl 0.09%) by using X‐ray photoelectron spectroscopy (XPS), X‐ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. XPS analysis of the surface of as‐supplied AZ31 alloy showed the presence of MgO, whereas after immersion in the physiological solution, only Mg (OH)2 was detected. The result has been discussed with reference to literature data. From the photoemission spectra and quantitative analysis, a small amount of Ca (about 2 wt%) was also detected.

Bacillus cereus SN7 Encapsulation process as a substitute protein source in fish feed

Bacillus Cereus SN7 bacteria can inhibit the growth of pathogenic bacteria. Encapsulation is a technology for wrapping the core material in micro-sized capsules that can release their contents in a certain environment. The research aimed to encapsulate the biomass yield as a protection for B. cereus SN7 bacteria from contaminants. This study used an experiment method, namely conducting experiments on the formation of bacterial encapsulation with 2 sources of emulsion: CaCl2 0,1 M and chitosan mixture, 1% acetic acid in 100 ml-1, then tested the effectiveness of encapsulation by looking at the viability of B. cereus SN7 bacteria by counting the number of colonies pH, temperature and physiological aspect of the bacterium. The results of encapsulation studies carried out using emulsion of chitosan mixture, 1% acetic acid in 100 ml- can be formed into capsule beads that can protect bacteria. Meanwhile, using citosan could not last for 75 minutes. After testing the effectiveness of the capsule and its bacterial viability, it is very effective for the production process or for further applications. then the best storage temperature is 100C, pH 5 and stable immersion in physiological solutions.

Characterization of heat resistant hydraulic sealer for warm vertical obturation

ObjectiveWarm vertical compaction of gutta-percha is a technique that is used by most specialists for root canal obturation. The sealers currently available exhibit irriversible chemical changes when heated. New biologically active sealers that do not sustain irreversible changes when heated are an attractive alternative to be used with warm vertical compaction obturation technique. The aim of this study was to measure the heat generated by warm vertical compactors inside the root canal, characterize a newly developed root canal sealer at different temperatures and verify its suitability at the actual temperature window used clinically. MethodsThe typical temperatures generated by two heat carriers in a root canal were assessed by thermocouples. Two premixed root canal sealers TotalFill BC and HiFlow BC (FKG, Switzerland) were allowed to set and they were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction analysis (XRD) immediately after setting and by XRD after 28 days in physiological solution. The ion leaching in solution was assessed by inductively coupled plasma (ICP). The organic component was extracted in acetone and assessed by Fourier transform infrared spectroscopy (FT-IR) for both the unset sealer and sealer subjected to different temperatures. The heat profiles of both sealers were investigated by FT-IR and thermographic analysis. ResultsNone of the devices tested achieved the temperatures set on the dial. The highest temperatures were coronal followed by apical for both devices. The sealers were identical except for the vehicle. The inorganic components included tricalcium silicate, dicalcium silicate and zirconium oxide. No calcium hydroxide was produced by any of the sealers after immersion in physiological solution but calcium was released in solution. The chemistry of both sealers was modified when heated but both recovered when cooled. SignificanceThe heat carriers were unreliable and the heat generated inside the canal was not the same as the temperature set on the dial. Since both sealers had identical chemistry save for minimal modifications to the organic component and were both resistant to heat, TotalFill BC sealer is recommended for use with warm vertical compaction technique as it is cheaper and as effective as the HiFlow.

Influence of textural characteristics on biomineralization behavior of mesoporous SiO2-P2O5-CaO bioactive glass and glass-ceramics

The present work demonstrates the novel synthesis of multi-components, ternary SiO2-P2O5-CaO mesoporous bioactive glass (MBG) and bioactive glass-ceramics (MBGC) through acid assisted sol-gel route by using Pluronic, P123 as structure directing agent followed by evaporation induced self-assembly (EISA) process. As synthesized samples has been characterized by different analytical techniques before and after immersion in physiological solution to unravel the structural, morphological and textural properties and correlate with biomineralization process. The different structural species of the pristine MBG/MBGC samples have been confirmed by high resolution x-ray diffraction (HR-XRD) and Fourier transforms infra-red (FTIR) spectroscopy studies. Bright field transmission electron microscopy (BF TEM) study reveal a wormhole like structures in the pristine samples, which is a typical characteristic of mesoporous samples. Moreover, the obtained samples exhibit superior textural characteristics like enhanced surface area and mesoporosity revealed by nitrogen adsorption-desorption technique. The presence of various anionic species in the pristine samples has been revealed by magic angle spinning nuclear magnetic resonance (MAS NMR) technique. The textural characteristics and the biomineralization behavior of pristine and soaked samples have been studied by varying the calcium and phosphorous contents with respect to silica. The in-vitro bioactivity analysis performed over three different samples in simulated body fluid (SBF) for different immersion duration leads to the formation of hydroxy carbonated apatite (HCA). The formed HCA layer is confirmed by analytical techniques such as HR-XRD and FTIR spectroscopy, which indicates the nano sized HCA crystals are impregnated in the amorphous matrix. Furthermore, significant modifications on the surface of samples have been illustrated by FE-SEM micrographs before and after SBF immersion, which specifies growth of thin-HCA layer. The mesostructured glassy samples showed an excellent cell viability response without toxicity up to the concentration of 100 mg ml−1. Additionally, cell-culture studies like cell-proliferation and cell viability test were also performed on the MBG and MBGC to show the material-cell interaction and it was found to be in good agreement within the desired range.

Synthesis of borate modified bioactive glass scaffold using PVP burning-out method for bone tissue replacement

Three-dimensional (3D) bioactive glass scaffolds are one of the most studied types of scaffolds for bone tissue replacement because of their excellent bioactivity and potential for stimulating osteogenesis and angiogenesis. In the present study, modified Hench- based bioglass was fabricated by polyvinyl pyrrolidone (PVP) burning-out method for producing porous scaffold. In vitro investigation of the scaffolds’ bioactivity was achieved through examining changes in its composition during exposing to physiological simulated body fluid (SBF) solution via Fourier transform-infrared (FT-IR) absorption spectroscopy, X-ray diffraction (XRD) analysis, Scanning electron microscopy (SEM) supported by Energy-dispersive X-ray (EDX). FT-IR spectral data was used to validate the formation of hydroxyapatite as an indication of the bioactivity potential of the studied scaffold post incubation in SBF. The prepared samples were examined by XRD to recognize the crystalline phase/phases that may formed after immersion in physiological solutions and supported via (SEM/EDX) data.

Approach for fabricating bioglass coatings on reticulated vitreous carbon foams for tissue engineering applications

Reticulated vitreous carbon foams have recently been used in the fabrication of scaffolds for biomedical applications, and have been shown to support cell adhesion. In this research, a methodology for coating reticulated vitreous carbon foams with two different bioglasses synthesized using the sol-gel technique is presented, towards enhancing the bioactivity of the reticulated vitreous carbon scaffolds. These coatings were morphologically characterized by confocal optical microscopy and scanning electron microscopy. Moreover, reactivity of the coated foams was also evaluated through in vitro tests by immersion in physiological solution. The results show successful deposition of the bioglass coating on the surface of the foams without compromising foam porosity. Coating morphological studies revealed a relationship between the composition of the bioglass and the final morphology of the coating. Additionally, preliminary in vitro tests showed that coating reactivity was also related to initial coating composition. Although the coatings dissolved after 21 days in PBS, the precipitation of a calcium-phosphate layer indicated the potential presence of the initial phases of the apatite formation process.

Nanostructural insights into the dissolution behavior of Sr-doped hydroxyapatite

In this study, high-resolution transmission electron microscopy (HRTEM) was employed to characterize the nanostructure of strontium-substituted hydroxyapatite (Sr-HA) and its evolution following in vitro immersion in physiological solutions. HRTEM images showed that the substitution of Sr induced local distortions in the hydroxyapatite (HA) lattice: minor levels of edge dislocations were detected at low doping contents of Sr ions (1 at%); when the Sr content exceeded 10 at%, the density of grain boundaries increased notably and triple junctions were clearly observed. The dissolution of undoped HA was initiated at crystallite surfaces, whereas the dissolution of Sr-HA started around grain boundaries. Acicular nanocrystal reprecipitation was observed on grain surfaces immersed in simulated body fluid (SBF), while not in dilute hydrochloric acid (HCl). These findings suggest appropriate levels of Sr incorporation can introduce imperfections in the crystal structure of apatite and thus enhance its dissolution rate towards enhanced physicochemical performance in biomedical applications.

Avaliação microbiológica e físico-química de pernis suínos tratados com ácidos orgânicos e/ou vapor no controle da contaminação superficial por Salmonella Typhimurium

Asymptomatic carrier pigs are the main risk factor for carcass contamination during the slaughter. Several post-slaughter prevention programs have been tested, such as organic acids and steam under pressure. These alternatives show low cost and high efficiency. This study tested the use of organic acid solutions and steam, in isolated tests and its associations. This experiment also evaluated the physical-chemistry features of the pork. Forty pork legs were contaminated with Salmonella Typhimurium DT 177 and subsequently divided into 4 treatments: immersion in physiological solution for 5 seconds (control, T1); immersion in physiological solution with 1000 ppm of organic acids for 5 seconds (T2); sprinkling of steam under pressure (4 bar) at 140oC (T3); and T2 after T3 (T4). An area of 100cm 2 was sampled through superficial swabs for Salmonella counts by Most Probable Number method (MPN). Aspect, color, consistency, smell, and levels of fat, protein, pH, and moisture were also evaluated before and after each treatment. The use of steam associated to the immersion in organic acid solution showed better efficiency for reduction of superficial contamination (decreasing 100% of counts) but the better effectiveness was observed through the decreasing of 0.8 log of MPN at skin and 0.77 log of MPN at muscle by using the physiological solution (T1) and the organic acid solution (T2), respectively. The steam treatment associated with the organic acid solutions (T4) decreased the pH and increased moisture of pork legs, although it did not mischaracterize the quality (within required parameters for human consumption). All the other treatments did not change physical-chemistry fefatures. KEYWORDS: organic acids; physical-chemistry; pork leg; Salmonella sp.; steam.

Fibrinogen nanofibers for guiding endothelial cell behavior.

This paper describes the biological consequences of presenting electrospun fibrinogen (FBG) to endothelial cells as a spatially organized nanofibrous matrix. Aligned and randomly oriented FBG nanofibers with an average diameter of less than 200 nm were obtained by electrospinning of native FBG solution. Electrophoretic profiling confirmed that the electrospun FBG resembled the native protein structure, and fluorescent tracing of FITC-labeled FBG showed that electrospun fibers withstood immersion in physiological solutions reasonably well for several days. With respect to cellular interactions, the nanofibrous FBG matrix provided better conditions for initial recognition by human umbilical vein endothelial cells compared to pre-adsorbed FBG on a flat surface. Furthermore, the spatial organization of electrospun FBG fibers presented opportunities for guiding the cellular behavior in a way that is not possible when the protein is presented in another form (e.g. adsorbed or soluble). For example, on aligned FBG fibers, cells rapidly oriented themselves along the fibers, and time-lapse recordings revealed pronounced cellular movements restricted to the fiber direction. In great contrast, on randomly deposited fibers, cells acquired a stellate-like morphology and became locally immobilized by the fibers. We also show that the FBG fiber orientation significantly influenced both the cytoskeleton organization in confluent cell layers and the orientation of the extracellular fibronectin matrix secreted by the cells. In conclusion, this study demonstrates that electrospun FBG nanofibers can be a promising tool for guiding endothelial cell behavior for tissue engineering applications.

Novel fast-setting calcium silicate bone cements with high bioactivity and enhanced osteogenesis in vitro

Novel calcium silicate cements (CSCs) consisting of sol-gel-derived calcium silicate powder as a solid phase and ammonium phosphate solution as a liquid phase were developed. The diametral tensile strength, morphology, and phase composition of various cements were evaluated before and after immersion in physiological solution, in addition to setting time. The proliferation and osteogenetic expression of human osteosarcoma cell line U2OS for the cement specimens were also analyzed. The results indicated that the simultaneous formation of apatite and calcium silicate hydrates (CaO–SiO2–H2O, C–S–H) may endow CSCs with unique properties after mixing with a phosphate buffer solution. These CSCs were not only fast-setting within 9 min, as well as highly bioactive, but they also enhanced proliferation and differentiation of U2OS cells. The development of fast-setting CSCs with high bioactivity may thus have numerous applications as biomaterials.

Immersion behavior of gelatin-containing calcium phosphate cement

Calcium phosphate cements (CPCs) have many favorable properties that support their clinical use as bone defect repair. However, it is difficult to deliver to the required site and hard to compact adequately due to inherently low ductility of ceramics. The aim of this study focused on the effect of the gelatin content on properties of CPCs. The diametral tensile strength, morphology, and weight loss of gelatin cements were evaluated after immersion in physiological solution, in addition to setting time. The results indicated that the setting time significantly increased with increasing gelatin amount. The 2 wt.% gelatin could make CPCs attain the maximum strength value of 2.1 MPa at 15-day immersion, while 1.6 MPa for the cement without gelatin. It is concluded that the presence of gelatin improved mechanical properties of CPCs; in particular, 2 wt.% gelatin. CPCs containing 2 wt.% gelatin hardened in an acceptable time recommended for clinical applications.

Development of an Array of Ion-Selective Microelectrodes Aimed for the Monitoring of Extracellular Ionic Activities

In this study, we present the development and the characterization of a generic platform for cell culture able to monitor extracellular ionic activities (K+, NH4+) for real-time monitoring of cell-based responses, such as necrosis, apoptosis, or differentiation. The platform for cell culture is equipped with an array of 16 silicon nitride micropipet-based ion-selective microelectrodes with a diameter of either 2 or 6 microm. This array is located at the bottom of a 200-microm-wide and 350-microm-deep microwell where the cells are cultured. The characterization of the ion-selective microelectrode arrays in different standard and physiological solutions is presented. Near-Nernstian slopes were obtained for potassium- (58.6 +/- 0.8 mV/pK, n = 15) and ammonium-selective microelectrodes (59.4 +/- 3.9 mV/pNH4, n = 13). The calibration curves were highly reproducible and showed an average drift of 4.4 +/- 2.3 mV/h (n = 10). Long-term behavior and response after immersion in physiological solutions are also presented. The lifetime of the sensors was found to be extremely long with a high recovery rate.

Synergistic reinforcement of in situ hardening calcium phosphate composite scaffold for bone tissue engineering

Calcium phosphate cement (CPC) hardens in situ to form solid hydroxyapatite, can conform to complex cavity shapes without machining, has excellent osteoconductivity, and is able to be resorbed and replaced by new bone. Therefore, CPC is promising for use in craniofacial and orthopaedic repairs. However, the low strength and lack of macroporosity of CPC limit its use. The aim of the present study was to increase the strength and toughness of CPC while creating macropores suitable for cell infiltration and bone ingrowth, and to investigate the effects of chitosan and mesh reinforcement on the composite properties. Specimens were self-hardened in 3 mm×4 mm×25 mm molds, immersed in a physiological solution for 1–84 d, and tested in three-point flexure. After 1 d, the unreinforced CPC control had a flexural strength (mean±s.d.; n=6) of (3.3±0.4) MPa. The incorporation of chitosan or mesh into CPC increased the strength to (11.9±0.8) and (21.3±2.7) MPa, respectively. The incorporation of both chitosan and mesh synergistically into CPC dramatically increased the strength to (43.2±4.1) MPa. The work-of-fracture (WOF) (toughness) was also increased by two orders of magnitude. After 84 d immersion in a simulated physiological solution, the meshes in CPC dissolved and formed interconnected cylindrical macropores. The novel CPC scaffold had a flexural strength 39% higher, and WOF 256% higher than the conventional CPC without macropores. The new composite had an elastic modulus within the range for cortical bone and cancellous bone, and a flexural strength higher than those for cancellous bone and sintered porous hydroxyapatite implants. In conclusion, combining two different reinforcing agents together in self-hardening CPC resulted in superior synergistic strengthening compared to the traditional use of a single reinforcing agent. The strong and macroprous CPC scaffold may be useful in stress-bearing craniofacial and orthopaedic repairs.

Bone Bonding Through Bioadhesives : Present Status

Until recently use of adhesives was confined to cases in which glued areas could be pre-treated or at least cleaned. Thus, grease or oil contaminated surfaces could not be joined together by glueing. More recently, some adhesives have been developed which allow previous treatment of greasy surfaces to be avoided. Among these we find epoxy resins, acrylics and polyurethances. These adhesives have been used until now in various industries. We have begun a research program with these products and in aiming to design an adhesive which would enable immediate and strong bone bonding and avoid problems of metallic fixation, this study is a continuation of our previous research. Thus we tested - currently available surgical and dental adhesives - original mixtures developed in our laboratory. Mechanical assays were performed on bone samples from human femurs in different conditions : dried, cleaned, fresh, or after immersion in physiological solution. They consist essentially of tensile tests on Lhomargy and Zwick's machine wherein the stress is directed perpendicular to the interface. Variations of tensile strength (in h bar) are related to hardening time and to mixture composition. The specimens are joined together either in monolayers or in multilayers. The use of adequate catalysts ensures setting at room temperature. Torsion tests and fatigue tests are carried out concomitantly. Standardized bevel fermoral osteotomies were performed on mice with a dental saw after I.P. Nembutal anesthesia in order to test biological tolerance : - for the control group we study the evolution of bone repair after circumferential wiring - for the animals under test, bones are glued together with one of the proposed adhesives. Radiological and histological studies (using classical Azantrichrome staining after demineralization) are carried out at regular time intervals. In the control animals particular attention is paid to the time course of the formation, constitution and evolution of callus. In the test animals, we can observe callus formation, bone growth into the adhesive material and glue resorption, and look for specific antigenic phenomena. Despite expected improvements, bone glueing remains a challenge and only restricted clinical applications can be proposed.

Modifications Histoenzymologiques Comparées entre le Noeud Sino-atrial et le Muscle Auriculaire en Anoxie, chez le Lapin

Left rabbit auricles are investigated histoenzymatically to determine the metabolic profile of atrial and sino-atrial fibers, directly or after immersion in physiological solution, normally oxygenated or submitted to anoxy. Oxygenated physiologic medium does not disturb the enzymatic profiles, excepting the NADH2-TR and the glycogen in the nodal tissue. The anoxy increases strongly the glycogenolysis in the node and considerably less in the auricular muscle. In the node, the Krebs cycle and the ATPA are also increased. In auricular fibers some enzymes of Krebs cycle diminishes (MDH, ICDH), or remain indifferent (SDH, COX). The authors conclude that, despite important changes of the activities in the sino-atrial fibers, these are better protected against anoxy, because of their more rapid adaptation facilities to unfavourable situation. The mechanism involved in this adaptive possibility remains still open.