Different Concentrations Of Glutaraldehyde Research Articles

Enhanced proton conductivity and mechanical stability of crosslinked sodium alginate as a biopolymer electrolyte membrane in fuel cell application

Abstract Nafion is a commercial polymer membrane that is commonly used in fuel cell systems, despite its major limitations such as high fuel crossover and high manufacture cost. The production of sodium alginate (SA) blended membrane with crosslinking agent (glutaraldehyde) and plasticizer (glycerol) is one of several current efforts to discover an alternative membrane with improved proton conductivity and mechanical properties. In this study, SA biomembranes were prepared using solution casting method and dried at a certain temperature. Then, the prepared membranes were immersed with 5% glycerol in different concentrations of glutaraldehyde. The cross-linked biomembranes underwent various tests such as liquid uptake, swelling ratio, ion exchange capacity, proton conductivity and mechanical stability. The best membrane achieved the highest proton conductivity with a value of 8.28 mS cm-1 and mechanical stability with a value of 218.00 MPa. Glutaraldehyde made a positive modification and had a beneficial impact on the characteristics of SA. The incorporation of glutaraldehyde and glycerol within the biopolymer notably improved the otherwise lacking mechanical properties of SA.

Antimicrobial Activity of Chitosan Scaffold Loaded with Soluble Factors of Different Probiotic Strains Against Multidrug Resistant Pseudomonas aeruginosa.

Bacterial infection remains the most frequent complication of burn injury, which can lead to sepsis, even if antibiotics are used topically and systemically. Pseudomonas aeruginosa (P. aeruginosa) is the main causative agent in many cases. The emergence of antibiotic-resistant strains in recent years has increased the need to find novel alternative therapies, such as probiotics. Therefore, this study aimed to examine the antimicrobial properties of probiotic cell-free supernatant (CFS), along with the potential use of a chitosan scaffold both as an antimicrobial agent and as a carrier for the delivery of these complexes. Evaluation of the antimicrobial properties of cell-free soluble factors of probiotic bacteria both alone and in combination with chitosan scaffolds. Nine isolates of P. aeruginosa previously identified by standard diagnostic tests were investigated. The antimicrobial effects of probiotics in the form of Pedilact® oral drop which contained three probiotic strains, Kidilact® sachet, which contained seven probiotic strains, and strains of Lactobacillus casei (L. casei) and Lactobacillus acidophilus (L. acidophilus) isolated from yogurt were studied by an agar well diffusion assay and by using CFS harvested at various growth stages, without pH neutralization. Chitosan with different concentrations of glutaraldehyde (GA) as a crosslinking agent was fabricated to produce a suitable scaffold for loading cell-free supernatants of probiotic strains. The scaffolds were then characterized using scanning electron microscopy. The antimicrobial properties of the CFS, chitosan, and chitosan scaffolds loaded with CFS were analyzed against MDR P. aeruginosa. In the agar well diffusion assay, CFS obtained from probiotic strains effectively inhibited the growth of a clinical strain of P. aeruginosa. This effect was observed when CFS was assessed without pH neutralization. Kidilact® was the most promising synbiotic formulation based on its inhibitory activity. The chitosan scaffold was successfully fabricated, as shown by SEM, and its structure was not affected by acidic CFS. The fabricated scaffolds were able to deliver CFS and, interestingly, antibacterial activity against P. aeruginosa when CFS was loaded on the chitosan scaffold was enhanced significantly. The results of this study showed chitosan scaffold loaded with cell-free probiotics metabolites can be considered to be a promising antimicrobial dressing in wound healing applications.

Magnetic CLEAs of β-Galactosidase from Aspergillus oryzae as a Potential Biocatalyst to Produce Tagatose from Lactose

β-galactosidase is an enzyme capable of hydrolysing lactose, used in various branches of industry, mainly the food industry. As the efficient industrial use of enzymes depends on their reuse, it is necessary to find an effective method for immobilisation, maintaining high activity and stability. The present work proposes cross-linked magnetic cross-linked enzyme aggregates (mCLEAs) to prepare heterogeneous biocatalysts of β-galactosidase. Different concentrations of glutaraldehyde (0.6%, 1.0%, 1.5%), used as a cross-linking agent, were studied. The use of dextran-aldehyde as an alternative cross-linking agent was also evaluated. The mCLEAs presented increased recovered activity directly related to the concentration of glutaraldehyde. Modifications to the protocol to prepare mCLEAs with glutaraldehyde, adding a competitive inhibitor or polymer coating, have not been effective in increasing the recovered activity of the heterogeneous biocatalysts or its thermal stability. The biocatalyst prepared using dextran-aldehyde presented 73.6% recovered activity, aside from substrate affinity equivalent to the free enzyme. The thermal stability at 60 °C was higher for the biocatalyst prepared with glutaraldehyde (mCLEA-GLU-1.5) than the one produced with dextran-aldehyde (mCLEA-DEX), and the opposite happened at 50 °C. Results obtained for lactose hydrolysis, the use of its product to produce a rare sugar (D-tagatose) and operational and storage stability indicate that heterogeneous biocatalysts have adequate characteristics for industrial use.

Synthesis, modification and application of fish skin gelatin-based hydrogel as sustainable and versatile bioresource of antidiabetic peptide

Gelatin hydrogel is widely employed in various fields, however, commercially available gelatin hydrogels are mostly derived from mammalian which has many disadvantages due to the supply and ethical issues. In this study, the properties of hydrogels from fish-derived collagen fabricated with varying Glutaraldehyde (GA) determined. The antidiabetic properties of salmon gelatin (SG) and tilapia gelatin (TG) was also evaluated against α-glucosidase. Glutaraldehyde-crosslinked salmon gelatin and tilapia gelatin were used, and compared with different concentrations of GA by 0.05 %, 0.1 %, and 0.15 %. Water absorbency, swelling, porosity, pore size and water retention of the hydrogels were dependent on the degree of crosslinking. The synthesis of hydrogels was confirmed by FTIR study. Scanning electron microscope (SEM) observation showed that all hydrogels have a porous structure with irregular shapes and heterogeneous morphology. Performance tests showed that gelatin-GA 0.05 % mixture had the best performance. Antidiabetic bioactivity in vitro and in silico tests showed that the active peptides of SG and TG showed a high binding affinity to α-glucosidase enzyme. In conclusion, SG and TG cross-linked GA 0.05 % have the potential as an antidiabetic agent and as a useful option over mammalian-derived gelatin.

Chitosan@TiO2 composites for the adsorption of copper(II) and antibacterial applications

Chitosan (CS) is a biopolymer that is well known for its ubiquity, biodegradability, lack of toxicity, low cost, antibacterial activity, and excellent heavy metal adsorption ability. We synthesized CS and CS@TiO2 composites (CST) with different concentrations of glutaraldehyde (crosslinking agent) solution by a simple method involving a crosslinking process (using glutaraldehyde as the crosslinking agent), a freeze-drying technique, and exchange with ammonia solution. The interaction mechanisms of the as-synthesized samples were systematically characterized by scanning electron microscopy, electron dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and the Brunauer-Emmett-Teller method. Among the as-synthesized samples, 3%CS-V (CS composites synthesized using 3% glutaraldehyde for crosslinking and exchanged with ammonia solution) at an initial concentration of 300 ppm exhibited a preferable adsorption capacity for copper ions (Cu2+), with a maximum adsorption capacity of 31 mg g− 1. Sorption equilibrium isotherms fit the Freundlich model. Compared to CS, 7%CST-V (CST composite synthesized using 7% glutaraldehyde for crosslinking and exchanged with ammonia solution) exhibited higher antibacterial activity against Staphylococcus epidermidis due to a synergistic effect. The antimicrobial efficacy against Escherichia coli was more affected by copper ions than TiO2 addition and glutaraldehyde concentration, whereas the antimicrobial efficacy against S. epidermidis was more affected by TiO2 addition and exchange with ammonia solution.

Lipase immobilization on a novel class of Zr-MOF/electrospun nanofibrous polymers: Biochemical characterization and efficient biodiesel production

In this study, due to the favorable properties of MOF compounds and fibrous materials, new nanostructures of Zr-MOF/PVP nanofibrous composites were synthesized by electrospinning procedure. The related features of these samples were characterized by relevant analyzes, including SEM, BET surface area analysis, XRD, and FTIR spectroscopy. The final product showed significant properties such as small particle size distribution, large surface area, and high crystallinity. This strategy for producing these nanostructures could lead to new compounds as novel alternative materials for biological applications. Lipase MG10 was successfully immobilized on the mentioned nanofibrous composites and biochemically characterized. The lipase activity of free and immobilized lipases was considered by measuring the absorbance of pNPP (500 μM in 40 mM Tris/HCl buffer, pH 7.8, and 0.01% Triton X100) at 37 °C for 30 min. Different concentrations of glutaraldehyde, different crosslinking times, different times of immobilization, different enzyme loading, and different pH values have been optimized. Results showed that the optimized immobilization condition was achieved in 2.5% glutaraldehyde, after 2 h of crosslinking time, after 6 h immobilization time, using 180 mg protein/g support at pH 9.0. The immobilized enzyme was also totally stable after 180 min incubation at 60 °C. The free enzyme showed the maximum activity at pH 9.0, but the optimal pH of the immobilized lipase was shifted about 1.5 pH units to the alkaline area. The immobilized lipase showed about 2.7 folds (78%) higher stability than the free enzyme at 50 °C. Some divalent metal ions, including Cu2+ (22%), Co2+ (37%), Mg2+ (12%), Hg2+ (11%), and Mn2+ (17%) enhanced the enzyme activity of immobilized enzyme. The maximum biodiesel production (27%) from R. communis oil was obtained after 18 h of incubation by lipase MG10. The immobilized lipase displayed high potency in biodiesel production, about 83% after 12 h of incubation. These results indicated the high potency of Zr-MOF/PVP nanofibrous composites for efficient lipase immobilization.

Optimization of Collagen Chemical Crosslinking to Restore Biocompatibility of Tissue-Engineered Scaffolds.

Collagen scaffolds, one of the most used biomaterials in corneal tissue engineering, are frequently crosslinked to improve mechanical properties, enzyme tolerance, and thermal stability. Crosslinkers such as 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) are compatible with tissues but provide low crosslinking density and reduced mechanical properties. Conversely, crosslinkers such as glutaraldehyde (GTA) can generate mechanically more robust scaffolds; however, they can also induce greater toxicity. Herein, we evaluated the effectivity of double-crosslinking with both EDC and GTA together with the capability of sodium metabisulfite (SM) and sodium borohydride (SB) to neutralize the toxicity and restore biocompatibility after crosslinking. The EDC-crosslinked collagen scaffolds were treated with different concentrations of GTA. To neutralize the free unreacted aldehyde groups, scaffolds were treated with SM or SB. The chemistry involved in these reactions together with the mechanical and functional properties of the collagen scaffolds was evaluated. The viability of the cells grown on the scaffolds was studied using different corneal cell types. The effect of each type of scaffold treatment on human monocyte differentiation was evaluated. One-way ANOVA was used for statistical analysis. The addition of GTA as a double-crosslinking agent significantly improved the mechanical properties and enzymatic stability of the EDC crosslinked collagen scaffold. GTA decreased cell biocompatibility but this effect was reversed by treatment with SB or SM. These agents did not affect the mechanical properties, enzymatic stability, or transparency of the double-crosslinked scaffold. Contact of monocytes with the different scaffolds did not trigger their differentiation into activated macrophages. Our results demonstrate that GTA improves the mechanical properties of EDC crosslinked scaffolds in a dose-dependent manner, and that subsequent treatment with SB or SM partially restores biocompatibility. This novel manufacturing approach would facilitate the translation of collagen-based artificial corneas to the clinical setting.

Immobilization of β-galactosidase from Bacillus licheniformis for application in the dairy industry.

The food industry has developed a wide range of products with reduced lactose to allow people with intolerance to consume dairy products. Although β-galactosidase has extensive applications in the food, pharma, and biotechnology industries, the enzymes are high-cost catalysts, and their use makes the process costly. Immobilization is a viable strategy for enzyme retention inside a reactor, allowing its reuse and application in continuous processes. Here, we studied the immobilization of β-galactosidase from Bacillus licheniformis in ion exchange resin. A central composite rotational design (CCRD) was proposed to evaluate the immobilization process in relation to three immobilization solution variables: offered enzyme activity, ionic strength, and pH. The conditions that maximized the response were offered enzyme activity of 953 U, 40 mM ionic strength, and pH 4.0. Subsequently, experiments were performed to provide additional stabilization for biocatalyst, using a buffer solution pH 9.0 at 25 °C for 24 h, and crosslinking with different concentrations of glutaraldehyde. The stabilization step drastically impacted the activity of the immobilized enzyme, and the reticulation with different concentrations of glutaraldehyde showed significant influence on the activity of the immobilized enzyme. In spite of substantially affecting the initial activity of the immobilized enzyme, higher reagent concentrations (3.5 g L-1) were effective for maintaining stability related to the number of cycles of the enzyme immobilized. The β-galactosidase from Bacillus licheniformis immobilized in Duolite A568 is a promising technique to produce reduced or lactose-free dairy products, as it allows reuse of the biocatalyst, decreasing operational costs.Key Points• Immobilization of β-galactosidase from Bacillus licheniformis in batch reactor• Influence of buffer pH and ionic concentration and offered enzyme activity on immobilization• Influence of glutaraldehyde on operational stability.

Kinetics, absorption and diffusion mechanism of crosslinked Chitosan Hydrogels

Green polymers are extremely useful for various environmental applications. One such biopolymer is Chitosan. In this study, crosslinked and physical Chitosan hydrogels were synthesized. The swelling of disc-shaped hydrogels crosslinked using different concentrations of Glutaraldehyde were compared with physical film and bead shaped hydrogels. Best swelling of around 3000% was observed in case of square film shaped hydrogels but they lacked rigidity and dissolved in mild acids. In case of crosslinked hydrogels, as the crosslinker concentration increased, the hydrogels entrapped less water but gained better mechanical strength. Characterization of synthesized crosslinked hydrogels was carried out using FTIR, TGA and DSC. Equilibrium swelling results indicated more water absorption at acidic pH (2.5). Simultaneously, increase in temperature led to enhancement of swelling degree. The hydrogels trapped more water leading to increased swelling, in case of lower molar salt concentrations. Second order kinetics was followed due to stress relaxation of polymeric chain. Diffusion was found to be anomalous since exponent values lied between 0.5 and 1. Peleg‟s and Exponential association model were used to carry out absorption modeling. The data was found to fit the Peleg‟s absorption model. Degree of swelling is a major factor for deciding a hydrogels utility. Swelling ability, biocompatibility and availability of lone pairs of oxygen and nitrogen on the surface of CS makes it ideal for applications in drug delivery, controlled release of fertilizers and adsorption of environmental contaminants.

Innovative ecological method for producing easy care characteristics and antibacterial activity onto viscose fabric using glutaraldehyde and chitosan nanoparticles

PurposeThis study aims to explore the incorporation of the authors previously prepared chitosan nanoparticles (CNPs) of size around 60-100 nm in the cross-linking formulation of viscose fabrics to see CNPs impact in terms of imparting multi-functional characteristics such as tensile strength, dry wrinkle recovery angles and antibacterial properties.Design/methodology/approachCNPs of size around 60-100 nm were incorporated in cross-linking formulations for viscose fabrics, including different concentrations of glutaraldehyde as a non-formaldehyde cross-linking agent and magnesium chloride hexahydrate as a catalyst. The formulations were applied at different curing times and temperatures in 100 mL distilled water, giving rise to a wet pickup of ca. 85 per cent. The fabrics were dried for 3 min at 85°C and cured at specified temperatures for fixed time intervals in thermo fixing oven according to the traditional pad-dry-cure method.FindingsThe above eco-friendly method for finished viscose fabrics was found to obtain high dry wrinkle recovery angle and maintain the tensile strength of the finished fabric within the acceptable range, as well as antibacterial properties against Escherichia coli and Staphylococcus aureus as a gram-negative and gram-positive bacteria, respectively. Both, scanning electron microscope and nitrogen percent on the finished fabric confirm the penetration of CNPs inside the fabric structure. Finally, viscose fabrics pageant antibacterial activity against gram-positive and gram-negative bacteria assessed even after 20 washing cycle.Research limitations/implicationsCNPs with its flourishing effect with respect to cationic nature, biodegradability, reactivity, higher surface area and antimicrobial activity; in addition to glutaraldehyde as non-formaldehyde finishing agent can be used as multi-functional agents for viscose fabrics instead of DMDHEU, polyacrylate and monomeric composites as hazardous materials.Practical implicationsCNPs as cationic biopolymers were expected to impart multi-functional properties to viscose fabrics especially with obtaining reasonable dry wrinkle recovery angle and tensile strength in addition to antibacterial properties.Originality/valueThe novelty addressed here is undertaken with a view to impart easy care characteristics and antibacterial activities onto viscose fabrics using CNPs as antimicrobial agent and glutaraldehyde as non-formaldehyde durable press finishes to-replace the traditional formaldehyde-based resins. Besides, to the authors’ knowledge, there is no published work so far using the above cross-linking formulation written above.

Biofunctionalized microbead arrays for early diagnosis of breast cancer

A high-performance method is suspension microbead arrays which facilitate HER2 recognition for rapid prognosis in its preliminary stages before cancer reaches to its metastases level or first prevalence of tumor growth. To achieve this goal, we synthesized gelatin microbeads by oil in water (o/w) emulsion method and the size and stability of micro-particles were optimized with different concentrations of glutaraldehyde. The non-toxicity of microbeads was proved by MTT assay. Then the Herceptin was immobilized on the microbeads surface by carbodiimide coupling method. FITC was used as a fluorescent marker for recognizing HER2 receptors on SKBr3 cancer cells (clinical sample) and the recognition was tracked by flow cytometry. Results showed significant discrimination between SKBr3 cancer cells sample concerning HER2 negative cancer cells as a control sample.

Effect of Glutaraldehyde Crosslinking on Degree of Substitution, Thermal, Structural, and Physicochemical Properties of Corn Starch

Native corn starch (NCS) is chemically modified by crosslinking with glutaraldehyde (GLU) at different concentrations of GLU (at constant reaction time) and different reaction times (at constant GLU concentration). Crosslinked corn starches with varying degree of substitution (DS) are produced in acidic (pH = 1.43 ± 0.01) and alkaline (11.04 ± 0.02) reaction mediums and DS values are determined. Thermal, structural, swelling, and solubility properties of the crosslinked starches are also investigated. The increase in DS become greater as the reaction pH increases to alkaline. Fourier transform infrared spectroscopy (FTIR) results indicate that hydroxyl band frequency values of crosslinked starches prepared in acidic medium shift to a higher frequency value as a result of the decrease in the number of hydrogen bonds in starch. However, no change in the frequency value of the hydroxyl band is observed in the FTIR spectrum of the crosslinked starch prepared in alkaline medium. Gelatinization temperatures of crosslinked starches produced in the acidic medium increase while gelatinization enthalpy, swelling power, and solubility considerably decrease. When the reaction medium is alkaline, crosslinked starches display slightly lower gelatinization temperatures and dramatically reduce gelatinization enthalpy values, although solubility does not change significantly compared to NCS. Swelling power decreases considerably when the starch is treated with 20% GLU in the alkaline medium. As a result, glutaraldehyde with different functional properties based on the pH of the reaction medium can be an effective crosslinking reagent for starch.

Preparation of meglumine antimonate loaded albumin nanoparticles and evaluation of its anti-leishmanial activity: an in vitro assay.

Cutaneous leishmaniasis is still a health problem worldwide, especially in tropical and subtropical areas. Currently, pentavalent antimony compounds are used to treat leishmaniasis. These compounds cause various side effects in the body. Therefore, there is a need to discover new drugs with less toxicity and more therapeutic effects. In this study, we encapsulated the meglumine antimonate into the albumin as a drug carrier and evaluated the anti-leishmanial effect of the prepared nanoparticles. The precipitation method was used for this purpose by applying different concentrations of glutaraldehyde and N-(3-Dimethylaminopropyl)-N-ethyl carbodiimide hydro chloride Ethyl (DEC) and then, field emission test was performed using Scanning Electron Microscopy for evaluating the morphology and size particles. The cytotoxicity and inhibitory of drugs were evaluated on J774 macrophages and Leishmania major promastigotes, respectively. Nanodrugs prepared using glutaraldehyde (10μl/ml) and DEC (13mg/ml) had the smallest and largest size, respectively. The highest anti-leishmanial activity was observed in the drugs prepared with glutaraldehyde (10μl/ml). Also this nanodrug had the lowest cytotoxicity against macrophages. Given that meglumine antimonate loaded albumin nanoparticles prepared with glutaraldehyde (10μg/ml), can improve the anti-leishmanial effects of this old drug, it can be a good option as a drug delivery system.

The effect of two different crosslinkers on in vitro characteristics of ciprofloxacin-loaded chitosan implants.

The objective of this study was to determine and evaluate a controlled release implant of ciprofloxacin using bovine hydroxyapatite (BHA)-chitosan composite and glutaraldehyde or genipin as crosslinking agents. Ciprofloxacin implants were prepared using BHA, chitosan, ciprofloxacin at 30:60:10 and using three different concentrations of glutaraldehyde or genipin (0.3, 0.5, or 0.7%) as crosslinkers. Implants were formed as mini-tablet with 4.0 mm diameter weighing 100 mg using compression method. Further, the prepared ciprofloxacin implants were characterized for porosity, density, water absorption capacity, swelling, degradation, compressive strength, compatibility (Fourier transforms-infrared spectroscopy (FT-IR)), morphology (scanning electron microscope (SEM)), X-ray diffraction (X-RD), and in vitro drug release. The addition of glutaraldehyde or genipin as crosslinkers in ciprofloxacin implant showed controlled release profile of ciprofloxacin over a time period of 30 days. SEM photomicrograph revealed low porosity of the implant after crosslinking with glutaraldehyde or genipin. The FTIR study confirmed the formation of covalent imine bonds between chitosan and glutaraldehyde. Moreover, the addition of glutaraldehyde or genipin as crosslinkers caused a decrease in the mechanical strength of the implant. Increased concentration of glutaraldehyde or genipin reduced the crystallinity of BHA and chitosan, which were confirmed by X-RD studies. The results obtained from this study indicated that glutaraldehyde or genipin had the potential effect to retard ciprofloxacin release from BHA-chitosan-ciprofloxacin implant for 30 days.

Preparation and Optimisation of Cross-Linked Enzyme Aggregates Using Native Isolate White Rot Fungi Trametes versicolor and Fomes fomentarius for the Decolourisation of Synthetic Dyes.

The key to obtaining an optimum performance of an enzyme is often a question of devising a suitable enzyme and optimisation of conditions for its immobilization. In this study, laccases from the native isolates of white rot fungi Fomes fomentarius and/or Trametes versicolor, obtained from Czech forests, were used. From these, cross-linked enzyme aggregates (CLEA) were prepared and characterised when the experimental conditions were optimized. Based on the optimization steps, saturated ammonium sulphate solution (75 wt.%) was used as the precipitating agent, and different concentrations of glutaraldehyde as a cross-linking agent were investigated. CLEA aggregates formed under the optimal conditions showed higher catalytic efficiency and stabilities (thermal, pH, and storage, against denaturation) as well as high reusability compared to free laccase for both fungal strains. The best concentration of glutaraldehyde seemed to be 50 mM and higher efficiency of cross-linking was observed at a low temperature 4 °C. An insignificant increase in optimum pH for CLEA laccases with respect to free laccases for both fungi was observed. The results show that the optimum temperature for both free laccase and CLEA laccase was 35 °C for T. versicolor and 30 °C for F. fomentarius. The CLEAs retained 80% of their initial activity for Trametes and 74% for Fomes after 70 days of cultivation. Prepared cross-linked enzyme aggregates were also investigated for their decolourisation activity on malachite green, bromothymol blue, and methyl red dyes. Immobilised CLEA laccase from Trametes versicolor showed 95% decolourisation potential and CLEA from Fomes fomentarius demonstrated 90% decolourisation efficiency within 10 h for all dyes used. These results suggest that these CLEAs have promising potential in dye decolourisation.

Effects of glutaraldehyde concentration and fixation time on material characteristics and calcification of bovine pericardium: implications for the optimal method of fixation of autologous pericardium used for cardiovascular surgery.

Autologous pericardium, which is widely used in the field of cardiovascular surgery, is usually fixed with glutaraldehyde (GA) to improve handling and provide biomechanical stability. However, an optimal method of GA fixation of autologous pericardium is not known. The objective of this study was to evaluate the effects of GA concentration and fixation time on material characteristics and calcification of bovine pericardium. Bovine pericardial tissues were fixed with different concentrations of GA (0.3, 0.4, 0.5 and 0.6%) for different exposure times (10 and 20 min). Material characteristics of the fixed tissues were assessed by mechanical test, thermal stability test and pronase test. The tissues were subcutaneously implanted into 3-week-old rats for 2months, and the calcium contents of the explanted tissues were measured. Differences between the groups were evaluated by two-way analysis of variance. Differently treated tissues showed no significant differences in tensile strength. The mean elongation at break of the pericardial tissues fixed with 0.5 and 0.6% was significantly higher compared with 0.3 and 0.4% when fixed for 20 min. The mean elongation at break of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min when fixed with 0.5 and 0.6%. Thermal stability test revealed significantly higher mean shrinkage temperature of the pericardial tissues fixed with 0.6% compared with lower concentrations irrespective of fixation time. The mean shrinkage temperature of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min irrespective of GA concentration. Pronase test revealed significantly lower mean percent remaining weight of the pericardial tissues fixed with 0.3% compared with higher concentrations irrespective of fixation time. The mean percent remaining weight of the pericardial tissues fixed for 20 min was significantly higher compared with 10 min irrespective of GA concentration. The mean calcium content of the pericardial tissues fixed with 0.6% was significantly lower than that of the pericardial tissues fixed with 0.4% irrespective of fixation time. Fixation of bovine pericardium with 0.5 and 0.6% GA for 20 min produced superior results with regard to material characteristics (mechanical properties, degree of fixation and resistance to enzymatic degradation) and postimplantation calcification. These results may have implications for optimal fixation of autologous pericardium used for cardiovascular surgery.

Ca2+-induced soy protein nanoparticles as pickering stabilizers: Fabrication and characterization

The development of food-grade Pickering stabilizers has recently attracted fast increasing interest in the food science field. The work reports a novel non-thermal process to fabricate soy protein isolate (SPI) nanoparticles to perform as effective Pickering stabilizers. The nanoparticles were formed by Ca2+-induced aggregation and subsequent glutaraldehyde (GAD) crosslinking. At a protein concentration of 2% (w/v), increasing Ca2+ concentration (from 0 to 7.5 mM) led to a progressive increase in turbidity and particle size (60–130 nm), indicating aggregation and formation of nano-sized particles. The Ca2+-induced SPI nanoparticles, further treated with different concentrations of GAD (0–200% equivalents), were characterized in terms of particle size, surface hydrophobicity and charge, internal integrity, emulsification performance and interfacial packing, as well as emulsion stability. The results indicated that the crosslinking treatment resulted in larger particle sizes, lower surface hydrophobicity and higher surface charge, stronger internal integrity, lower emulsification performance and higher emulsion stability against coalescence, with the extent of changes increasing with the applied GAD concentration. The emulsions stabilized by these fabricated nanoparticles followed the rule of limited coalescence, and had a very low surface coverage (3.8–12.6%). The surface coverage is considerably lower than that of many Pickering emulsions previously reported in the literature. All the results confirmed that the fabricated SPI nanoparticles could perform as effective Pickering stabilizers. The findings would be of great importance for the development of food-grade Pickering stabilizers suitable for the formulations of functional foods and medicine.

Studies On hydrolysis of skimmed milk using immobilized β-galactosidase in a membrane reactor

In the present investigation, an attempt has been made to investigate the hydrolysis of skimmed milk in a batch membrane bioreactor using β-galactosidase immobilized on a 30 kDa PES membrane. The skimmed milk solutions of different concentrations(30 kg m-3 – 80 kg m-3)were deproteinated through 30 kDa and 5 kDa cross-flow ultrafiltration membrane modules successively and about 95%-97% lactose present in the feed was recovered in the permeate stream. The deproteinated milk permeates thus obtained were subjected to hydrolysis in a batch membrane bioreactor fitted with the enzyme-immobilized PES membrane. Immobilization of enzyme on the ultrafiltration membrane was performed by cross-linking using two different concentrations of glutaraldehyde (3%v/v and 4%v/v). It was observed that high percent retention ofenzyme activity(94.2%) and percent enzyme loading(98%) were attained when the immobilization was performed using 4%v/v glutaraldehyde. For an initial feed concentration of 70 kg m-3,the percentage lactose conversion achieved were 45.2% and 21.4% using β-galactosidase immobilized with 4%v/v and 3%v/v glutaraldehyde respectively. However, a significant percentage reduction in pure water fluxwas observed in case of enzyme-immobilized membranes (27.5% and 67.5% for immobilization carried out using 3% and 4%v/v glutaraldehyde respectively)from that obtained using the fresh membrane. The enzyme-immobilized membrane(cross-linked with 4%v/v glutaraldehyde) could be used for six successive runs with more than 90% retention in activity and less than 5% loss due to leaching. The unsteady state mass balance equation was developed in order to predict the concentration profile above the membrane surface.The model equation could also predict the permeate concentration well within 95% confidence interval

K88 Fimbrial Adhesin Targeting of Microspheres Containing Gentamicin Made with Albumin Glycated with Lactose.

The formulation and characterization of gentamicin-loaded microspheres as a delivery system targeting enterotoxigenic Escherichia coli K88 (E. coli K88) was investigated. Glycated albumin with lactose (BSA-glucose-β (4-1) galactose) was used as the microsphere matrix (MS-Lac) and gentamicin included as the transported antibiotic. The proposed target strategy was that exposed galactoses of MS-Lac could be specifically recognized by E. coli K88 adhesins, and the delivery of gentamicin would inhibit bacterial growth. Lactosylated microspheres (MS-Lac1, MS-Lac2 and MS-Lac3) were obtained using a water-in-oil emulsion, containing gentamicin, followed by crosslinking with different concentrations of glutaraldehyde. Electron microscopy displayed spherical particles with a mean size of 10–17 µm. In vitro release of gentamicin from MS-Lac was best fitted to a first order model, and the antibacterial activity of encapsulated and free gentamicin was comparable. MS-Lac treatments were recognized by plant galactose-specific lectins from Ricinus communis and Sophora japonica and by E. coli K88 adhesins. Results indicate MS-Lac1, produced with 4.2 mg/mL of crosslinker, as the best treatment and that lactosylated microsphere are promising platforms to obtain an active, targeted system against E. coli K88 infections.

Formulation and characterization of gentamicin-loaded albumin microspheres as a potential drug carrier for the treatment of E. coli K88 infections

The aim of this study was to formulate and characterize gentamicin-loaded albumin microspheres for their potential therapeutic use in E. coli K88 infections. Based on in vitro assays, it is proposed that microspheres may serve as a carrier of gentamicin and may provide localized antibacterial activity in the treatment of porcine colibacillosis. Gentamicin-albumin microspheres (GAM) were obtained using a water/oil (W/O) emulsion followed by cross-linking with different concentrations of glutaraldehyde. Electron microscopy showed spherical particles with indentations. The average size of the GAM was 10.5-12.3 µm. At pH 7.2, the release kinetics of gentamicin from the GAM was successfully described as an initial burst defined by a first order equation. Gentamicin release was unaffected by the glutaraldehyde concentrations used but was affected by acidic conditions. The behavior of gentamicin release from the GAM was not altered by digestion with trypsin and chymotrypsin at pH 7.2. Additionally, the concentration of gentamicin released from GAM to reach antibacterial activity was similar to that of free gentamicin against E. coli K88. This work shows the potential use of GAM as therapeutic vehicles of gentamicin to counteract intestinal infections in pigs