This study provides a description of the systematic investigation of the thermal response of collagen hydrogel phantoms, which serve as a model for venous wall tissue, to endovenous laser ablation (EVLA). We investigated two key wavelengths (980 nm and 1470 nm) and two optical fibre types (bare and radial). Applying a combination of numerical simulations and controlled experiments, we analysed the heat distribution, peak temperatures and spatial extent of the thermal damage. Furthermore, the structural alterations of the collagen across its hierarchical organisation were assessed applying complementary analytical techniques, including high-performance liquid chromatography (primary structure; amino acid composition), Fourier transform infrared spectroscopy (secondary structure), and scanning electron microscopy (fibrillar organisation and morphology). Only a small number of studies have systematically combined thermal modelling with the quantitative analysis of the collagen composition, secondary structure and fibrillar morphology within a single controlled experimental platform. The results indicated that 1470 nm radiation, particularly with respect to the radial fibres, provides for more localised heating and effective collagen modification than 980 nm radiation and results in the confinement of the thermal damage to, and the more pronounced structural disruption of, the collagen matrix. These findings established a consistent relationship between the laser parameters, thermal distribution and collagen structural response, thus providing the structural basis for the understanding of the differences observed between the clinical EVLA outcomes. This approach provides a more rational basis for the optimisation of the EVLA parameters and reduces the reliance on empirically-derived treatment protocols.

Estrogen deficiency is known to affect connective tissues, yet its impact on collagen organization beyond bone remains insufficiently understood. In this study, we investigated tissue-specific alterations in type I collagen in rat skin and tendon following ovariectomy, with and without alendronate treatment. Native tissues were analyzed in parallel with corresponding crude collagen isolates to distinguish between collagen-related properties and extracellular matrix (ECM)-level contributions. Estrogen deficiency was associated with tissue-dependent changes, with skin exhibiting increased collagen content together with higher acid extractability, while tendon remained comparatively stable. These findings suggest that collagen extractability is influenced not only by collagen abundance but also by ECM-related factors, including matrix composition and organization. Differences between native tissues and isolates are further consistent with selective extraction effects that may be related to fibrillar organization and matrix interactions. Changes in lipid distribution and glycosaminoglycan content were consistent with tissue-specific matrix remodeling. FTIR analysis of amide I band ratios indicated differences consistent with changes in FTIR-detectable molecular organization; however, these observations should be interpreted as indirect indicators due to potential contributions from non-collagenous components and extraction-related effects. Alendronate treatment was associated with condition-dependent changes primarily at the ECM level, affecting collagen extractability and matrix composition without clear evidence of direct modification of collagen secondary structure. Overall, the results suggest that estrogen deficiency is associated with tissue-specific differences in collagen behavior and extractability, likely reflecting combined effects of ECM composition, organization, and extraction selectivity.

Background:Guided bone regeneration (GBR) relies on barrier membranes to stabilize the blood clot and maintain a protected healing space. Collagen membranes are typically derived from mammalian sources; however, concerns regarding zoonotic transmission, ethics, and cost have driven interest in alternative materials. Fish-derived collagen has emerged as a potential substitute. A novel membrane from European carp (Cyprinus carpio) skin has shown favorable soft-tissue outcomes, but its performance in bone healing has not yet been evaluated. Methods:Standardized cortical defects were created in the femora of 21 Wistar rats. Four treatments were evaluated: empty defect, carp collagen membrane alone, Bio-Oss® + carp collagen membrane, and Bio-Oss® + Bio-Gide®. Animals were euthanized at 4, 12, and 16 weeks. Healing was assessed by micro-CT and histology. Descriptive statistics (median, IQR) were used, and group comparisons were performed using non-paramertic Kruskal-Wallis tests with Dunn's post-hoc testing; effect sizes were reported as η². Results:Defects treated with the carp collagen membrane alone showed a consistent trend toward higher median healing scores, greater new bone formation, and smaller residual defect size, although differences were not statistically significant. When combined with Bio-Oss®, outcomes were less favorable than with Bio-Oss® + Bio-Gide®. Conclusions:The carp collagen membrane supported bone healing in a non-critical-size rat femoral defect model and demonstrated favorable biocompatibility. These findings suggest that fish-derived collagen may represent a promising alternative membrane material, particularly in indications where membrane function alone is sufficient. Further validation in large-animal critical-size defect models is required.

Collagen hydrogels serve as biomimetic scaffolds that closely resemble the natural extracellular matrix, thus providing an ideal 3D biocompatible environment for cells. However, based on our previous experience, not all collagen isolates are capable of gelling, which appears to depend on the type, origin, species, age and sex of the source animal and the collagen isolation method applied. We therefore decided to evaluate porcine collagen-rich materials isolated from two different porcine genotypes applying two different specific isolation methods, and to analyse other main components, i.e., lipids and glycosaminoglycans, as well as amino acid composition and structural and morphological properties. While all the collagen isolates obtained were subjected to the gelling process, only one of them successfully gelled. In addition, the gelling ability of this isolate was confirmed repeatedly on collagens that were isolated from other pigs of the same porcine genotype. The results revealed that the gelling process proceeds via cooperation between the composition and the structure of the collagen isolate. With respect to the composition, one of the most important factors in terms of the success of the gelation process of collagen isolates concerns elevated glycosaminoglycan contents. The structural factors that characterise collagen isolates, i.e., cross-links (immature and mature) and their mutual ratio, as well as the presence of telopeptides, strongly impact the progress of the gelling process and the resulting character of the hydrogel structure. All these factors are influenced by the isolation procedure.

Collagen membranes are widely used in tissue and bone engineering, including guided bone regeneration (GBR). For effective and uninterrupted bone healing, a GBR membrane must maintain its functionality for an initial critical period of 4 weeks. A novel carp collagen sponge has already shown promise as a wound coating and vascular graft coating, making it a candidate for GBR applications as well. To enhance the mechanical properties and longevity of GBR membranes, we modified the basic carp collagen membrane with combinations of l-lactide, ε-caprolactone, d,l-lactide, and glycolide in various molar ratios. While traditional methods rely on histological evaluation to assess the degradation pattern and therefore suitability of GBR membranes ex vivo, this study employed micro-MRI as an innovative, noninvasive approach to monitor the in vivo degradation of carp collagen membrane and its polymer-modified variants. Our findings demonstrated that micro-MRI is a reliable and effective method for visualizing collagen membrane degradation in vivo, up to scaffold disintegration. Among the variants tested, collagen GBR membrane coated with d,l-lactide and glycolide in a 50:50 M ratio emerged as the most suitable for GBR purposes. However, since this study was conducted in the subcutaneous tissue of a rat model, further research is required to determine the behavior of carp collagen GBR membrane variants on bony surfaces.

In this study, large amplitude oscillation shear (LAOS) test was used to investigate the nonlinear behavior of collagen (COL) over a wide range of mass fractions. The original COL material is used in food industry with mass fraction of 7.6% (w/w) and another six mass fractions (1.5%, 2%, 3%, 4%, 5%, and 6%) were prepared by diluting. The structure of COL was evaluated via Fourier transform infrared spectroscopy and COL surface morphology was studied via scanning electron microscope (SEM). The results showed that the storage and the loss modulus increase with increasing COL mass fraction and COL showed a weak strain overshoot behavior. The Lissajous-Bowditch curves showed a gradual transition from narrow elliptical to wider elliptical shaped loops as the strain amplitude increases and the third-order Fourier coefficients G3 '$$ {G}_3<^>{\prime } $$, G3 ''$$ {G}_3<^>{\prime \prime } $$ values were changed significantly with the collagen mass fraction. The morphology results showed that dilution does not affect the internal structure of the COL gels. The results from this work are important since the nonlinear rheological response under LAOS of industrial collagen with a high mass fraction has not been reported.Highlights The viscoelasticity is tested and quantified for different mass fractions of COL. Tested COL is used in the food industry and has a high mass fraction (MF) The novelty for COL is in the combination of MF and evaluation methods. The structure of COL is evaluated via Fourier transform infrared spectroscopy. The surface morphology was studied via a scanning electron microscope.

This study examined the impacts of electron beam irradiation (0.25; 0,5; 1; 10 and 25 kGy) on bovine collagen hydrogels at a concentration of 3 wt%. The impact of irradiation was verified via the analysis of the mechanical, thermal and rheological properties, changes in the composition and structure of the collagen, its stability in the enzymatic environment, and its swelling and morphology. Both the degradation and cross-linking of the collagen mass were demonstrated in relation to the radiation dose. Degradation was proven via a decrease in the content of the triple helical part of the collagen and transformation into other collagen structural states, and cross-linking was demonstrated by an increase in the network chain density with the radiation dose. When compared with the non-irradiated gels, no significant qualitative changes in the configuration or ordering over longer distances were evident following the application of the irradiation doses. The apparent elastic modulus, overall thermal stability and rheological characteristics in the oscillatory regime, and the storage and loss moduli of elasticity correlated positively with the radiation dose.

Pulmonary artery banding is a surgical procedure performed when there is a shunt between the left and right ventricle. Its aim is to constrict the lumen of the pulmonary artery by using a band to reduce blood flow to the lungs. In this study, we report the results of investigating the mechanical properties of a composite composed of poly(L-lactide-co-ε-caprolactone) layers and a collagen matrix (PLCL-COLL). PLCL layers were obtained by electrospinning, impregnated with collagen solution, and finally cross-linked to increase the stiffness of the material. Bands of PLCL-COLL were implanted into a rat peritoneum and explanted after 1, 3, and 6 months in vivo. The mechanical properties of the material before and after implantation were determined using uniaxial tensile tests. The same was done with samples of strips prepared from GORE-TEX material. By comparing the results of tensile tests before implantation and after explantation, it was found that PLCL-COLL degrades in the rat's body and that it exhibits a mechanical response showing of elastic modulus values that correspond well to arterial biomechanics (elastic modulus measured in the initial linear region of the deformation was found to be: 4.14 MPa ± 1.11 MPa, 2.34 MPa ± 1.02 MPa, 1.11 MPa ± 0.77 MPa, and 0.88 MPa ± 0.60 MPa before implantation, and 1, 3, and 6 months after implantation respectively). Similar to the elastic modulus, the strength of the PLCL-COLL composite decreased during in vivo exposure (1.32 ± 0.32 MPa, 0.60 ± 0.26 MPa, 0.44 ± 0.11 MPa, and 0.46 ± 0.28 MPa before implantation, and 1, 3, and 6 months after implantation respectively). In our experiments, PLCL-COLL material was always more compliant than GORE-TEX (elastic modulus 34.7 MPa ± 2.06 MPa before implantation, and 9.35 MPa ± 6.80 MPa after implantation). The results suggest that PLCL-COLL could be a suitable candidate for the development of artery banding tapes, and also for further use in cardiovascular surgery.

By differentiating into mature adipocytes, 3T3 -L 1 cells can be utilized as a model cell line to investigate (pre)adipocyte function in vitro . Here, we present a protocol for combining qualitative and quantitative analysis of lipid droplets in mature 3T3 -L 1 adipocytes using oil red O. We describe steps to differentiate 3T3 -L1 preadipocytes to adipocytes and give detailed procedures to determine total lipid amount as well as lipid droplet size and number using microscopic devices and an ImageJ macro. For complete details on the use and execution of this protocol, please refer to Kaczmarek et al. 1

Various studies have correlated the mechanical properties of the aortic wall with its biochemical parameters and inner structure. Very few studies have addressed correlations with the cohesive properties, which are crucial for understanding fracture phenomena such as aortic dissection, i.e. a life-threatening process. Aimed at filling this gap, we conducted a comprehensive biochemical and histological analysis of human aortas (the ascending and descending thoracic and infrarenal abdominal aorta) from 34 cadavers obtained post-mortem during regular autopsies. The pentosidine, hydroxyproline and calcium contents, calcium/phosphorus molar ratio, degree of atherosclerosis, area fraction of elastin, collagen type I and III, alpha smooth muscle actin, vasa vasorum, vasa vasorum density, aortic wall thickness, thicknesses of the adventitia, media and intima were determined and correlated with the delamination forces in the longitudinal and circumferential directions of the vessel as determined from identical cadavers. The majority of the parameters determined did not indicate significant correlation with age, except for the calcium content and collagen maturation (enzymatic crosslinking). The main results concern differences between enzymatic and non-enzymatic crosslinking and those caused by the presence of atherosclerosis. The enzymatic crosslinking of collagen increased with age and was accompanied by a decrease in the delamination strength, while non-enzymatic crosslinking tended to decrease with age and was accompanied by an increase in the delamination strength. As the rate of calcification increased, the presence of atherosclerosis led to the formation of calcium phosphate plaques with higher solubility than the tissue without or with only mild signs of atherosclerosis. STATEMENT OF SIGNIFICANCE: This study presents a detailed biochemical and histological analysis of human aortic samples (ascending thoracic aorta, descending thoracic aorta and infrarenal abdominal aorta) taken from 34 cadavers. The contribution of this scientific study lies in the detailed biochemical comparison of the enzymatic and non-enzymatic glycosylation-derived crosslinks of vascular tissues and their influence on the delamination strength of the human aorta since, to the best of our knowledge, no such comprehensive studies exist in the literature. A further benefit concerns the notification of the limitations of the various analytical methods applied; an important factor that must be taken into account in such studies.

Collagen nanofibrous materials have become integral to tissue engineering due to their exceptional properties and biocompatibility. Dehydrothermal crosslinking (DHT) enhances stability and maintains structural integrity without the formation of toxic residues. The study involved the crosslinking of electrospun collagen, applying DHT with access to air and under vacuum conditions. Various DHT exposure times of up to 72 h were applied to examine the time dependance of the DHT process. The DHT crosslinked collagen was subsequently chemically crosslinked using carbodiimides. The material crosslinked in this way evinced elevated Young’s modulus values and ultimate tensile strength values, a lower swelling rate and lower shrinkage ratio during crosslinking, and a higher degree of resistance to degradation than the material crosslinked solely with DHT or carbodiimides. It was shown that the crosslinking mechanism using DHT occupies different binding sites than those using chemical crosslinking. Access to air for 12 h or less did not exert a significant impact on the material properties compared to DHT under vacuum conditions. However, concerning longer exposure times, it was determined that access to air results in the deterioration of the properties of the material and that reactions take place that occupy the free bonding sites, which subsequently reduces the effectiveness of chemical crosslinking using carbodiimides.

New biomaterials are routinely evaluated for their degradation behaviour in the real body environment. Following the 3R strategy, in vitro simulated body conditions are often preferred. No studies that simultaneously compare such conditions with the real body environment have been conducted to date. Model porous collagen scaffolds were exposed for 21 days to eight different environments: simple salt-based and enzymatic media, human blood plasma, cell culture media with and without human fibroblasts and ex vivo model cortical bone, and subsequently compared with an in vivo environment represented by a pig peritoneum. The mechanical properties of the scaffolds were then determined via uniaxial compression testing, and the structural properties via the micro-CT, weight loss, infrared spectroscopy, X-ray diffraction and histological methods. Interestingly, the various analysed simulated body conditions caused differing alterations in the collagen scaffold characteristics when compared with the real body environment. The mechanical properties were similar during the first 7 days of incubation but diverged after 14 and 21 days. The structural properties varied significantly after just 7 days of incubation. The histological evaluation of the scaffolds exposed to the cellular, ex vivo and in vivo conditions revealed the poor ability of cells to completely populate the scaffolds, accompanied by the massive ingrowth of connective tissue into the in vivo exposed scaffolds, which resulted in their variable global behaviour. In conclusion, the value of in vitro simulated body environments lies in their screening capacity and feasibility; however, direct extrapolation to real body conditions needs to be verified going forward.

Diamond-like carbon (DLC) layers are known for their high corrosion and wear resistance, low friction, and high biocompatibility. However, it is often necessary to dope DLC layers with additional chemical elements to strengthen their adhesion to the substrate. Ti-DLC layers (doped with 0.4, 2.1, 3.7, 6.6, and 12.8 at.% of Ti) were prepared by dual pulsed laser deposition, and pure DLC, glass, and polystyrene (PS) were used as controls. In vitro cell–material interactions were investigated with an emphasis on cell adhesion, proliferation, and osteogenic differentiation. We observed slightly increasing roughness and contact angle and decreasing surface free energy on Ti-DLC layers with increasing Ti content. Three-week biological experiments were performed using adipose tissue-derived stem cells (ADSCs) and bone marrow mesenchymal stem cells (bmMSCs) in vitro. The cell proliferation activity was similar or slightly higher on the Ti-doped materials than on glass and PS. Osteogenic cell differentiation on all materials was proved by collagen and osteocalcin production, ALP activity, and Ca deposition. The bmMSCs exhibited greater initial proliferation potential and an earlier onset of osteogenic differentiation than the ADSCs. The ADSCs showed a slightly higher formation of focal adhesions, higher metabolic activity, and Ca deposition with increasing Ti content.

The field of arterial biomechanics is shifting from the application of phenomenological to structural models that use the microstructural and chemical parameters of the arterial wall to describe remodeling, adaptation, growth and healing. However, the cohesive properties crucial for understanding fracture processes such as aortic dissection lack such models due to structural and biochemical data limitations. This study presents a detailed biochemical and histological analysis of human aortic samples (ascending thoracic aorta, descending thoracic aorta and infrarenal abdominal aorta) taken from 34 cadavers. The analysis assessed the calcium content, calcium/phosphate molar ratio, degree of atherosclerosis and quantitative histology results for elastin, collagen, smooth muscle cell content and aortic wall thickness. However, the main result concerned the determination of the enzymatic and non-enzymatic glycosylation-derived cross-links, i.e. the degree of collagen maturation and the quantitative determination of the degree of advanced glycation products based on the pentosidine content. These quantities were correlated with the delamination strength, age and the degree of atherosclerosis. It was shown that whereas the non-enzymatic crosslinking of collagen attributable to advanced glycation end products tends to decrease with age and, thus, increases with the delamination strength, the enzymatic crosslinking of collagen of the human aorta evinces the opposite trend, i.e. the rate of collagen maturation increases with age, accompanied by a decrease in the delamination strength of the wall. The positive correlation between the pentosidine content and the delamination strength is in alignment with clinical observations of aortic dissection in diabetic patients.

The micro-CT evaluation of structural parameter values is dependent on the processing of the image prior to its analysis. However, the degree of bias introduced by the image-processing process is generally unknown. The micro-CT analysis of three basic parameters (volume, surface, and pore size) was performed for 20 collagen-based porous scaffolds. The image data were processed using various approaches (noise reduction, binarization), analyzed and results were compared. A high degree of variability was observed in the values of the structural parameters. The differences between the mean values were as follows: 190% (volume), 160% (surface density), and 210% (pore size). Significant differences were observed with respect to the noise reduction in terms of the pore size values (frequently in excess of 300%). Our study proved the significant dependence of image processing on the results obtained. The data presented can be used as an estimate for the introduced bias. We suggest improvements in terms of the selection of the image-processing approach based on a combination of subjective selection (the standard method) and numerical analysis based on the consistency of the results. Although we focused on tissue engineering scaffolds, the principles are similar for all fields of the micro-CT application.

The aim of this study was to investigate batch-to-batch inconsistencies in the processing of pig and fish collagen isolates processed using two protocols that differed in terms of the acetic acid concentrations applied and the preand post-extraction steps, and which were previously tested in our laboratory with the intention of preserving the biological structures and functions of the collagen isolates for biomedical purposes. Both the major and minor components such as the amino acids, lipids, water, glycosaminoglycan and ash contents and elemental content, as well as the structure and morphology of the raw sources and the resulting batches of isolates were subsequently examined in detail applying standardized analytical methods including high perfomance liquid chromatography, ultraviolet-visible and infrared spectrometry, polyacrylamide gel electrophoresis, energy dispersive spectroscopy and scanning electron microscopy. All the fish isolates provided severalfold higher yields (8-45 wt %) than did the pig isolates (3-9 wt%). In addition, the variability of the fish isolate yields (the coefficient of variation for processing A: 16.4-32.9 % and B: 6.8-17.4 %) was significantly lower (p <= 0.05, n = 5) than that of the pig isolates (A: 27.7-69.8 %; B: 35.3-87.9 %). In general, the fish skin batches had significantly higher protein contents (>60 wt%) and lower lipid contents (<10 wt%) than the pig skin batches (<55 wt% protein and up to 66 wt% lipid). In addition, the fish skin batches did not differ significantly in terms of their composition applying the same processing method, whereas the pig skin batches exhibited considerable variations in terms of their compositions, particularly regarding the protein and lipid contents. It can be stated that, concerning the fish isolates, processing B was, in most cases, slightly more efficient and reproducible than processing A. However, concerning the pig isolates, although processing A appeared to be more efficient than processing B in terms of the yield, it resulted in the production of isolates that contained a certain level of contaminants. The study provides a comprehensive discussion on the suitability of the processing protocol in terms of producing batches of reproducible quality according to the specific type of biomaterial processed from different animal species.

Condylar hyperplasia is one of the causes of facial asymmetry and malocclusion, characterized by enlargement of the lower jaw due to excessive condyle growth activity. The aim of this study was to use micro-computed tomography (micro-CT) to evaluate the bone architecture of the condylar head and determine whether there are differences between patients with various forms of unilateral condylar hyperplasia (UCH): hemimandibular hyperplasia, elongation, and mixed form. The cohort consisted of 28 patients with a mean age of 21.9 years. All patients underwent surgical treatment (condylar shaving) for active pathological growth activity. The portion of the condylar head removed was imaged by micro-CT and subsequently evaluated. Micro-CT imaging and semiquantitative and quantitative evaluation of the bone structure (percentage bone volume, surface density, trabecular thickness, trabecular separation, degree of anisotropy, and porosity of the subchondral bone) did not reveal significant differences between the individual types of condylar hyperplasia (P > 0.05). There were no significant differences in bone structure between the anterior and posterior portions of the condylar head. No statistically significant differences between individual groups of UCH were found in the micro-CT evaluation of the condylar head bone architecture.

OBJECTIVES:To investigate the influence of the presence and position of bidirectional E-glass fibers under a CAD-CAM resin composite on the fracture pattern evaluated both after quasi-static mechanical loading and after fatigue. METHODS:Rectangular specimens (10 mm-long, 5 mm-large and 4.2 mm-thick) were prepared and divided into four groups (n = 30/group). The control group (C-Group) consisted of a 4.2 mm-thick layer of monolithic CAD/CAM resin composite resin (Cerasmart, GC). In the 3 other groups including the placement of a fiber layer (F-Groups), the CAD/CAM resin composite layer was reduced to 3-, 2- and 1-mm thickness (F3-, F2- and F1-Groups, respectively). Two bonded layers of bidirectional E-glass FRC (Dentapreg, ADM A.S.) were bonded underneath and a light-curable resin composite base (Gaenial Posterior, GC) was then added to reach a total thickness of 4.2 mm for all samples. In each group, half of the specimens (n = 15) were submitted to quasi-static mechanical loading to failure in a universal testing machine. The other half (n = 15) was subjected to cyclic isometric stepwise loading until failure or completion of 105000 cycles (5000 cycles at 500 N, followed by five stages of 20000 cycles at 750 N, 1000 N, 1250 N, 1500 N, and 1750 N). The data were analyzed by Weibull statistics for quasi-static loading, and by the Kaplan-Meier product limit estimation procedure after fatigue. All fractured specimens were studied using light and electron microscopy techniques, and the types of fracture were determined. RESULTS:For quasi-static mechanical loading, significant differences were observed for Weibull modulus and characteristic strength between groups, with values ranging from 10.8 to 22.4 for the former and from 2336.6 to 2974.7 for the latter. Also, survival after stepwise fatigue revealed statistically significant differences between groups (p < 0.05), the lowest values of cycles before failure being observed for F1-Group - Median = 61223 (50415; 65446) - as compared to the other groups - C-Group: Median = 89005 (86189; 98195); F3-Group: Median = 85198 (77279; 87860); F2-Group: Median = 89306 (87454; 97024). Both in quasi-static loading and after fatigue, the observation of fracture modes revealed major differences. While all fractures were vertical (split) in C-Group, the majority of the specimens in F-Groups presented some degree of horizontal deflection of the crack. In all deviated fractures, fractographic analysis confirmed a toughening effect of the fiber layer. SIGNIFICANCE:The present in vitro work tends to show that the fracture pattern of CAD-CAM resin composites is favorably affected by the presence and position of an underlying bidirectional E-glass fiber layer. The placement of E-glass fibers under a CAD-CAM resin composite may therefore represent an interesting strategy to reduce the risk of catastrophic restoration failure, which could be integrated in the development of the new generation of indirect materials, possibly in 3D-printing approaches.

The physical properties and structure of collagen treated with high-pressure technologies have not yet been investigated in detail. The main goal of this work was to determine whether this modern gentle technology significantly changes the properties of collagen. High pressure in the range of 0–400 MPa was used, and the rheological, mechanical, thermal, and structural properties of collagen were measured. The rheological properties measured in the area of linear viscoelasticity do not statistically significantly change due to the influence of pressure or the duration of pressure exposure. In addition, the mechanical properties measured by compression between two plates are not statistically significantly influenced by pressure value or pressure hold time. The thermal properties Ton and ∆H measured by differential calorimetry depend on pressure value and pressure hold time. Results from amino acids and FTIR analyses show that exposure of collagenous gels to high pressure (400 MPa), regardless of applied time (5 and 10 min), caused only minor changes in the primary and secondary structure and preserved collagenous polymeric integrity. SEM analysis did not show changes in collagen fibril ordering orientation over longer distances after applying 400 MPa of pressure for 10 min.

This study considered the examination of the influence of electron beam irradiation (2 and 100 kGy) on bovine collagen gels with various concentrations (3, 6 and 8 wt%). The impact of irradiation was verified via the analysis of the mechanical properties and the secondary structure of the collagen. The irradiated collagen gels behaved non-linearly and stiffened with increasing strain in contrast to the non-irradiated state in which they softened with increasing strain. The impact of irradiation was reflected by an increase in the tensile modulus and strain energy density. The observed increase was greater the higher the water content of the collagen gels. The impact of irradiation on the secondary structure was less clear; infrared spectrometry revealed that the events that take place are complex, with the occurrence of cross-linking, partial denaturation and other structural changes. The electron beam irradiated collagen gels continued to exhibit collagenous polymeric structures and integrity.