Genipin-Based Crosslinking of Jellyfish Collagen 3D Hydrogels

Collagen-based hydrogels are an attractive option in the field of cartilage regeneration with features of high biocompatibility and low immunogenic response. Crosslinking treatments are often employed to create stable 3D gels that can support and facilitate cell embodiment. In this study, we explored the properties of JellaGel™, a novel jellyfish material extracted from Rhizostoma pulmo. In particular, we analyzed the influence of genipin, a natural crosslinker, on the formation of 3D stable JellaGel™ hydrogels embedding human chondrocytes. Three concentrations of genipin were used for this purpose (1 mM, 2.5 mM, and 5 mM). Morphological, thermal, and mechanical properties were investigated for the crosslinked materials. The metabolic activity of embedded chondrocytes was also evaluated at different time points (3, 7, and 14 days). Non-crosslinked hydrogels resulted in an unstable matrix, while genipin-crosslinked hydrogels resulted in a stable matrix, without significant changes in their properties; their collagen network revealed characteristic dimensions in the order of 20 µm, while their denaturation temperature was 57 °C. After 7 and 14 days of culture, chondrocytes showed a significantly higher metabolic activity within the hydrogels crosslinked with 1 mM genipin, compared to those crosslinked with 5 mM genipin.

COMPARATIVE STUDY OF SPECTRAL CHARACTERISTICS OF COMPLEXES OF HOECHST 33258 AND METHYLENE BLUE WITH BOVINE SERUM ALBUMIN

The comparative study on interaction of bisbenzimidazole compound Hoechst 33258 and thiazine dye methylene blue (MB) with bovine serum albumin (BSA) was carried out by spectroscopic methods. Denaturation curves as well as absorption spectra and differential absorption spectra of protein-ligand complexes were obtained. Denaturation temperature of albumin complexes of BSA with Hoechst 33258 was shown to decrease with the growth of concentration ratio of ligand/protein, while for MB, vice versa, denaturation temperature increases. Changes in absorption spectra and differential absorption spectra of the complexes of ligands with albumin were revealed, which result from the binding of these DNA-specific ligands to protein. It is supposed that at the interaction of Hoechst 33258 with BSA some loosening of protein compact structure occurs due to the partial loss of helicity of α-structures, while for MB an increase of the protein compact structure takes place.

Effect of Solvent on the Hydrodynamic Properties of Collagen

In this study, the effect of solvent on the hydrodynamic properties of collagen extracted from tail tendons of young rats was researched. Collagen was dissolved in various aqueous carboxylic acid solutions, including acetic acid (AA), acetic acid with the addition of sodium chloride (AA/NaCl), formic acid (FA), lactic acid (LA), citric acid (CA), and also citrate buffer at pH = 3.7 (CB). The properties of collagen solutions at a concentration of 0.45 mg/mL were characterized based on the viscometric method. The reduced viscosity, intrinsic viscosity, and Huggins coefficient of collagen solutions and effect of solvent, temperature, and UV irradiation on these properties were investigated. Collagen solutions in acetic acid, acetic acid/NaCl, and citrate buffer were irradiated with UV light up to 1 h, and the viscosity of collagen solutions was measured. It was found that the organic acids used as solvent affected viscosity behavior, denaturation temperature, and stability of collagen solutions. The lowest values of studied parameters were obtained for the collagen solutions in acetic acid with the addition of sodium chloride. Thus, the effect of various aqueous carboxylic acid solutions on collagen solutions properties and denaturation temperature can also be affected by the sodium chloride addition. The results of this research can be crucial for the preparation of collagen solutions for both cosmetic and biomedical applications.

Isolation and properties of collagen extracted from mixed by-products obtained from different fish species

Fish by-products consisting of skin, bones, or scales are collagen sources. Acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC) mixed by-products derived from different fish species were extracted and evaluated. The properties evaluated for both collagens were chemical composition, amino acid- and SDS-PAGE- protein profiles, Fourier transform infrared spectroscopy (FTIR), denaturation temperature (Tmax), enthalpy (ΔH), and solubility. The ASC and PSC registered a protein content of 48.56 and 38.80 %, respectively. From the total amino acids detected, hydroxyproline accounted for 7 % and 6 % for ASC and PSC, respectively. The electrophoretic profile showed the presence of the type I collagen bands (α1, α2, β, and γ), whereas FTIR spectrum showed the presence of diverse collagen functional groups (Amide A, B, I, II, and III) for both extracted types, and demonstrated that the extraction process did not affect the collagen´s triple-helical structure. The Tmax of ASC and PSC were 38.27 and 38.07° C, respectively, whereas ΔH were 0.64 and 0.33 J g-1. The lowest solubility was registered at pH 5 for ASC and pH 9 for PSC. The caractheristics of the collagen extracted, indicated that a mixture of by-products from different species could be an alternative for their reutilization by the local markets.

Heat development at the knife roller during leather shaving

Leather, which is regularly tanned from whole hides of up to 5 m2, needs a constant thickness over the entire surface in order to be processed into high-quality consumer goods such as shoes, furniture and car interiors. Precise adjustment of the thickness is achieved by shaving. On an industrial scale, rotating knife rollers are used to remove chips from the flesh side of semi-finished leathers whereby adjusting the specified thickness and generating a smooth surface. Care must be taken to prevent the temperature from rising above the denaturation temperature of the leather during shaving in order to avoid any loss of quality. Beside this, temperature rise is always a sign of friction showing avoidable energy expenditure. In order to localize the source of friction during shaving, actual temperature development at the roller knife is studied. Different measuring methods are used to evaluate the temperature increase at the blade roll of the shaving machine. The finite element method is used to thermally simulate the process. Measured temperatures, the geometry of the blade roll and process data are taken into account for modelling the temperature development close to the blade edge. The obtained results enhance the understanding of temperature generating processes during machine operation and allow conclusions about potential improvements in the design of the machine and blades. Graphical abstract

Effect of cryogenic freezing on the rheological and calorimetric properties of pasteurized liquid egg yolk

The egg yolk undergoes an irreversible gelation process when freezing to –6 °C or lower. In this experiment, liquid egg yolk (LEY) was frozen in liquid nitrogen and stored at –18 °C for 150 days. The measurement of pH and colour of LEY were performed. The examination of the rheological and calorimetric properties of samples was also carried out. The results indicated that the pH of LEY changed significantly during frozen storage, increasing from 6.37 ± 0.02 to 6.58 ± 0.03 over five months. The colour of the samples also showed a significant change compared to the fresh sample. The rheological properties of the LEY also changed significantly after 1 day of freezing and during frozen storage, with a clear increasing trend of the yield stress. The results of the calorimetric study showed that freezing and frozen storage did not affect the denaturation temperature, however, the denaturation enthalpy was reduced by about half after five months of frozen storage.

Effect of Protein Denaturation Temperature on Rheological Properties of Baltic Herring (Clupea harengus membras) Muscle Tissue

The technological properties of raw fish are influenced by the changes in protein structure under heating, which determines the texture and quality of the product. The aim of the study was to examine the protein denaturation temperature and the rheological properties of Baltic herring muscle tissue. The thermal properties were determined by the differential scanning calorimetry (DSC) method and the rheological properties were determined using dynamic oscillatory tests. DSC showed four peaks associated with denaturing transformations of myosin (39.59 °C), sarcoplasm (51.67 °C), connective tissue (63.16 °C), and actin (74.40 °C). Analysis showed that not all transformations occurred according to the same kinetic model. The first two and the last peak are described by 1st order kinetics, while peak 3 is described by 2nd order kinetics. Correlating the changes in fish tissue structure during heating with the rheological characteristics provides more information. The obtained kinetics models correlated very strongly with the results of model testing. Rheological changes of the G’ and G” values had two inflexion points and demonstrate a high degree of convergence with the DSC changes of herring muscle tissue from 20 to 85 °C.