Collagen Structure Research Articles

Features of Congenital Arthrogryposis Due to Abnormalities in Collagen Homeostasis, a Scoping Review.

Congenital arthrogryposis (CA) refers to the presence of multiple contractures at birth. It is a feature of several inherited syndromes, notable amongst them are disorders of collagen formation. This review aims to characterize disorders that directly or indirectly impact collagen structure and function leading to CA in search for common phenotypic or pathophysiological features, possible genotype-phenotype correlation, and potential novel treatment approaches based on a better understanding of the underlying pathomechanism. Nine genes, corresponding to five clinical phenotypes, were identified after a literature search. The most notable trend was the extreme phenotype variability. Clinical features across all syndromes ranged from subtle with minimal congenital contractures, to severe with multiple congenital contractures and extra-articular features including skin, respiratory, or other manifestations. Five of the identified genes were involved in the function of the Lysyl Hydroxylase 2 or 3 enzymes, which enable the hydroxylation and/or glycosylation of lysyl residues to allow the formation of the collagen superstructure. Whilst current treatment approaches are post-natal surgical correction, there are also potential in-utero therapies being developed. Cyclosporin A showed promise in treating collagen VI disorders although there is an associated risk of immunosuppression. The treatments that could be in the clinical trials soon are the splice correction therapies in collagen VI-related disorders.

Electron Microscopy (EM) Analysis of Collagen Fibers in the Peri-Implant Soft Tissues around Two Different Abutments.

The design of the implant prosthesis-abutment complex appears crucial for shaping healthy and stable peri-implant soft tissues. The aim of the present animal study was to compare two implants with different healing abutment geometries: a concave design (TEST) and a straight one (CTRL). Transmission electron microscopy (TEM) was used to quantify the three-dimensional topography and morphological properties of collagen at nanoscale resolution. 2 swine were included in the experiment and 6 implants per animal were randomly placed in the left or right hemimandible in either the physiologically mature bone present between the lower canine and first premolar or in the mandibular premolar area, within tooth extraction sites. Each CTRL implant was positioned across from its respective TEST implant on the other side of the jaw. After 12 weeks of healing, 8 specimens (4 CTRL and 4 TEST) were retrieved and prepared for histological and TEM analysis. The results showed a significantly higher percentage of area covered by collagen bundles and average bundle size in TEST implants, as well as a significant decrease in the number of longitudinally oriented bundles with respect to CTRL implants, which is potentially due to the larger size of TEST bundles. These data suggest that a concave transmucosal abutment design serves as a scaffold, favoring the deposition and growth of a well-organized peri-implant collagen structure over the implant platform in the early healing phase, also promoting the convergence of collagen fibers toward the abutment collar.

Matrix metalloproteinase- 9 may contribute to collagen structure modification during postmortem aging of beef

Matrix metalloproteinases (MMPs) are responsible for the turnover of intramuscular connective tissue in live animals. We hypothesize that MMPs may play a role in postmortem aging of beef muscles for the degradation of connective tissues. Four different experiments were performed to: 1) characterize MMP activity during postmortem aging of beef; 2) determine if the native beef MMP can contribute to connective tissue degradation in a simulated standard industry postmortem aging condition; 3) explore approaches to improve the native beef MMP activity and 4) characterize MMP activity in beef from cattle supplemented with supranutritional level of Zn. In experiment 1, MMP was active throughout the entire aging periods (3, 21, 42 and 63 d) for beef muscles Longissimus lumborum, Gluteus medius and Gastrocnemius, and the unknown MMP responsible for the collagen degradation was identified as MMP-9 by Western Blot. In experiment 2 and 3, MMP-9 activity was noticeable in the gels after 42 d of storage in the cooler. Moreover, the addition of ZnCl2 in the model system significantly increased MMP-9 activity when compared to the control (P < 0.01). In experiment 4, Longissimus thoracis from animals supplemented with a supranutritional Zn level had increased Zn availability and MMP-9 activity than those from animals fed with a control diet (P < 0.05). Further research is needed better understand MMP-9 mechanism during postmortem aging of meat. With a better understanding of MMP-9 in the aging process, the beef industry can provide better connective tissue management strategies for lower-quality beef cuts.

Skin Extracellular Matrix Breakdown Following Paclitaxel Therapy in Patients with Chemotherapy-Induced Peripheral Neuropathy.

The chemotherapeutic agent paclitaxel causes peripheral neuropathy, a dose-limiting side effect, in up to 68% of cancer patients. In this study, we investigated the impact of paclitaxel therapy on the skin of breast cancer patients with chemotherapy-induced peripheral neuropathy (CIPN), building upon previous findings in zebrafish and rodents. Comprehensive assessments, including neurological examinations and quality of life questionnaires, were conducted, followed by intraepidermal nerve fiber (IENF) density evaluations using skin punch biopsies. Additionally, RNA sequencing, immunostaining for Matrix-Metalloproteinase 13 (MMP-13), and transmission electron microscopy provided insights into molecular and ultrastructural changes in this skin. The results showed no significant difference in IENF density between the control and CIPN patients despite the presence of patient-reported CIPN symptoms. Nevertheless, the RNA sequencing and immunostaining on the skin revealed significantly upregulated MMP-13, which is known to play a key role in CIPN caused by paclitaxel therapy. Additionally, various genes involved in the regulation of the extracellular matrix, microtubules, cell cycle, and nervous system were significantly and differentially expressed. An ultrastructural examination of the skin showed changes in collagen and basement membrane structures. These findings highlight the presence of CIPN in the absence of IENF density changes and support the role of skin remodeling as a major contributor to CIPN.

Morpho-mechanical mapping of human dura mater microstructure

The human dura mater is known to impact vastly traumatic brain injury mechanopathology. In spite of this involvement, dura mater is typically neglected in computational and physical human head models. The lack of location-dependent microstructural and related mechanical data of dura mater may be considered a rationale behind this simplification. The anisotropic nature of dura mater under various loading conditions so far remains unelucidated. Furthermore, principal collagen fiber orientation is yet to be quantified for a morpho-mechanically-informed material model on the dura mater. This study aims to assess how location-dependent mechanical anisotropy is linked to principal collagen fiber orientation. Uniaxial extension tests were performed in a heated tissue bath for 60 samples from six individuals and correlated to the three-dimensional collagen structure in four individuals using second-harmonic generation (SHG) imaging. Failure stress and stretch at failure, elastic modulus, and a microstructurally motivated material model were integrated to examine local differences in dura mater morpho-mechanics. The quantitative observation of collagen fiber orientation and dispersion confirmed that collagen is highly aligned in the human dura mater and that both fiber orientation and dispersion differ depending on the location investigated. This observation provides a possible explanation for the previously observed isotropic mechanical behavior, as the main collagen fiber direction is not oriented along the anterior-posterior or medial-lateral direction at most of the mapped locations. Additionally, these site-dependent structural properties have implications for the mechanical load response and therefore potentially for the regional functions dura mater has to fulfill. The here chosen non-symmetrical fiber dispersion material model fits the data well and provides a comprehensive parameter base for further studies and future finite element models. Statement of significanceThe human dura mater greatly affects traumatic brain injury mechanisms, but it is often ignored in computational and physical head models. This is because there is a lack of detailed microstructural and mechanical data specific to the dura mater. Its anisotropic nature and collagen fiber orientation have not been fully understood, hindering the development of an accurate material model. Hence, this study combines morphological data on collagen fiber orientation and dispersion at multiple locations of human cranial dura mater, and links microstructure to location-specific load-displacement behavior. It provides microstructurally informed mechanical information towards realistic head models for predicting location-dependent tissue behavior and failure for assessing brain injury and graft material development.

Molecular Subtypes and Machine Learning-Based Predictive Models for Intracranial Aneurysm Rupture

The determination of biological mechanisms and biomarkers related to intracranial aneurysm (IA) rupture is of utmost significance for the development of effective preventive and therapeutic strategies in the clinical field. GSE122897 and GSE13353 datasets were downloaded from Gene Expression Omnibus. Data extracted from GSE122897 were used for analyzing differential gene expression, and consensus clustering was performed to identify stable molecular subtypes. Clinical characteristics were compared between subgroups, and fast gene set enrichment analysis and weighted gene coexpression network analysis were performed. Hub genes were identified via least absolute shrinkage and selection operator analysis. Predictive models were constructed based on hub genes using the Light Gradient Boosting Machine, eXtreme Gradient Boosting, and logistic regression algorithm. Immune cell infiltration in IA samples was analyzed using Microenvironment Cell Population counter, CIBERSORT, and xCell algorithm. The correlation between hub genes and immune cells was analyzed. The predictive model and immune cell infiltration were validated using data from the GSE13353 dataset. A total of 43 IA samples were classified into 2 subgroups based on gene expression profiles. Subgroup I had a higher risk of rupture, while 70% of subgroup II remained unruptured. In subgroup I, specific genes were associated with inflammation and immunity, and weighted gene coexpression network analysis revealed that the black module genes were linked to IA rupture. We identified 4 hub genes (spermine synthase, macrophage receptor with collagenous structure, zymogen granule protein 16B, and LIM and calponin-homology domains 1), which constructed predictive models with good diagnostic performance in differentiating between ruptured and unruptured IA samples. Monocytic lineage was found to be a significant factor in IA rupture, and the 4 hub genes were linked to monocytic lineage (P<0.05). We reveal a new molecular subtype that can reflect the actual pathological state of IA rupture, and our predictive models constructed by machine learning algorithms can efficiently predict IA rupture.

Mycelium-based biomaterials as smart devices for skin wound healing.

Introduction: Recently, mycelia of Ganoderma lucidum and Pleurotus ostreatus, edible fungi, have been characterized in vitro as self-growing biomaterials for tissue engineering since they are constituted of interconnected fibrous networks resembling the dermal collagen structure. Aim: This work aims to investigate the biopharmaceutical properties of G. lucidum and P. ostreatus mycelia to prove their safety and effectiveness in tissue engineering as dermal substitutes. Methods: The mycelial materials were characterized using a multidisciplinary approach, including physicochemical properties (morphology, thermal behavior, surface charge, and isoelectric point). Moreover, preclinical properties such as gene expression and in vitro wound healing assay have been evaluated using fibroblasts. Finally, these naturally-grown substrates were applied in vivo using a murine burn/excisional wound model. Conclusions: Both G. lucidum and P. ostreatus mycelia are biocompatible and able to safely and effectively enhance tissue repair in vivo in our preclinical model.

Coating of Carbonized Leather Waste with the Conducting Polymer Polyaniline: Bicontinuous Composites for Dye Adsorption

Leather waste carbonized at 800 °C in an inert atmosphere was coated in situ with the conducting polymer polyaniline. The composition of composites varied from neat carbonaceous to polyaniline. Due to the fibrous collagen structure of the original leather after carbonization, the composites had a bicontinuous conducting morphology. The resistivity of composites determined as a function of applied pressure from 0.1 to 10 MPa fell mainly into the range of units to tens of Ω cm. In contrast to neat polyaniline, the composites maintained a good level of conductivity even under alkaline conditions. The application of a composite as an adsorbent of organic-dye pollutants in water treatment was illustrated using methylene blue and methyl orange with an eye to future functional adsorbents controllable by applied electrical potential.

Development of a zinc chloride-based chemo-mechanical system for potential minimally invasive dental caries removal system

Background/purposeThe chemo-mechanical caries-removal technique is known to offer advantages of selective dentin caries treatment while leaving healthy dental tissues intact. However, current sodium hypochlorite based reagents usually excessively damage dentin collagen. Therefore, the purpose of this study was to develop a novel chemo-mechanical caries-removal system to preserve the collagen network for subsequent prosthetic restorations. Materials and methodsThe calfskin-derived collagen was chosen as a model system to investigate the dissolution behavior of collagen under different operating conditions of chemical-ultrasonic treatment systems. The molecular weight, triple-helix structure, the morphology, and functional group of collagen after treatment were investigated. ResultsVarious concentrations of sodium hypochlorite or zinc chloride together with ultrasonic machinery were chosen to investigate. The outcomes of circular dichroism (CD) spectra demonstrated stability of the triple-helix structure after treatment of a zinc chloride solution. In addition, two apparent bands at molecular weights (MWs) of 130 and 121 kDa evidenced the stability of collagen network. The positive 222 nm and 195 nm negative CD absorption band indicated the existence of a triple-helix structure for type I collagen. The preservation of the morphology and functional group of the collagen network on the etched dentin surface were investigated by in vitro dentin decalcification model. ConclusionUnlike NaOCl, the 5 wt% zinc chloride solution combined with ultra-sonication showed dissolution rather than denature as well as degradation of the dentin collagen network. Additional in vivo evaluations are needed to verify its usefulness in clinical applications.

A judicious approach to induce large size growth of hydroxyapatite via applying graphene modified silicon nitride nanowires

Mimicking the structure of natural bone collagen fibers/hydroxyapatite (HA) to synthesize large size of HA for accelerated bone repair remains a challenge. Herein, silicon nitride nanowires (SN)-graphene (GE) was designed by the chemical vapor deposition, forming SN-GE (SG) similar to collagen fibers. Then, the large size HA was assembled onto SG by pulsed electrochemical deposition, the SG/HA (SGH) mimics the collagen fibers/HA structure of bone. The introduction of SG induces HA to large size grow in the form of coral-like. HA can be grown on a large size inextricably with the existence of GE modified layers. On the one hand, the upright GE sheets effectively increases the surface roughness which enhances the nucleation site of HA. On the other hand, the CO provides chemical bonding and induces HA nucleation. Compared with SN/HA(SH), the porosity of SGH decreased by 71%. The average diameter of the SGH is (9.76 ± 0.25) μm. Compared with SH, the diameter of SGH is 22 times larger than the diameter of SH. Indicating that SG induces large size growth of HA. Our work can provide a general strategy for the efficient preparation of biological scaffolds with large size HA that can be used in bone tissue engineering.

Single-Sided Nuclear Magnetic Resonance (NMR) for the Analysis of Skin Thickness and Collagen Structure in Scarred and Healthy Skin

Monitoring of skin scar thickness and structural properties is desirable when assessing the efficacy of the healing process. In this work, we report the use of single-sided, low-field nuclear magnetic resonance (NMR) for the analysis of the thickness and collagen structure of healthy and scarred skin. Acquisition of T2 relaxation profiles was proven to provide quantification of porcine skin thickness as accurate as standard histological techniques. Subsequent analysis of human participants highlighted the utility of this technique for identifying different types of scar and in identifying differences between the thickness of moderate hypertrophic scars and healthy skin. Using bead packings as a model system, determination of the surface-to-volume (S/V) ratio and tortuosity (k) was successfully measured on the single-sided apparatus based on time-resolved diffusion analysis. Application of this method to human skin was able to detect regional differences in collagen structures, consistent with qualitative expectations. It was also able to differentiate between healthy and scarred skin tissue. Preliminary results indicated that scarred tissue exhibited decreased S/V ratios and tortuosities, which is coherent with the formation of less-aligned collagen within scar tissue and indicated the potential for this technique to differentiate scar types. This novel application of single-sided low-field NMR has the potential to be deployed in clinical settings for the differentiation of scar types and for the assessment and monitoring of skin scarring and healing.

Imaging and quantification of the tumor microenvironment of triple negative breast cancer using TPEF and scanning laser optical tomography.

Triple-negative breast cancer is an aggressive subtype of breast cancer that has a poor five-year survival rate. The tumor's extracellular matrix is a major compartment of its microenvironment and influences the proliferation, migration and the formation of metastases. The study of such dependencies requires methods to analyze the tumor matrix in its native form. In this work, the limits of SHG-microscopy, namely limited penetration depth, sample size and specificity, are addressed by correlative three-dimensional imaging. We present the combination of scanning laser optical tomography (SLOT) and multiphoton microscopy, to depict the matrix collagen on different scales. Both methods can be used complementarily to generate full-volume views and allow for in-depth analysis. Additionally, we explore the use of SHG as a contrast mechanism for complex samples in SLOT. It was possible to depict the overall collagen structure and specific fibers using marker free imaging on different scales. An appropriate sample preparation enables the fixation of the structures while simultaneously conserving the fluorescence of antibody staining. We find that SHG is a suitable contrast mechanism to depict matrix collagen even in complex samples and using SLOT. The insights presented here shall further facilitate the study of the tumor extracellular matrix by correlative 3d imaging.

Evaluation and Application of Silk Fibroin Based Biomaterials to Promote Cartilage Regeneration in Osteoarthritis Therapy.

Osteoarthritis (OA) is a common joint disease characterized by cartilage damage and degeneration. Traditional treatments such as NSAIDs and joint replacement surgery only relieve pain and do not achieve complete cartilage regeneration. Silk fibroin (SF) biomaterials are novel materials that have been widely studied and applied to cartilage regeneration. By mimicking the fibrous structure and biological activity of collagen, SF biomaterials can promote the proliferation and differentiation of chondrocytes and contribute to the formation of new cartilage tissue. In addition, SF biomaterials have good biocompatibility and biodegradability and can be gradually absorbed and metabolized by the human body. Studies in recent years have shown that SF biomaterials have great potential in treating OA and show good clinical efficacy. Therefore, SF biomaterials are expected to be an effective treatment option for promoting cartilage regeneration and repair in patients with OA. This article provides an overview of the biological characteristics of SF, its role in bone and cartilage injuries, and its prospects in clinical applications to provide new perspectives and references for the field of bone and cartilage repair.

The Effect of γ-Aminobutyric Acid Intake on UVB- Induced Skin Damage in Hairless Mice.

The skin, the largest organ in the body, undergoes age-related changes influenced by both intrinsic and extrinsic factors. The primary external factor is photoaging which causes hyperpigmentation, uneven skin surface, deep wrinkles, and markedly enlarged capillaries. In the human dermis, it decreases fibroblast function, resulting in a lack of collagen structure and also decreases keratinocyte function, which compromises the strength of the protective barrier. In this study, we found that treatment with γ-aminobutyric acid (GABA) had no toxicity to skin fibroblasts and GABA enhanced their migration ability, which can accelerate skin wound healing. UVB radiation was found to significantly induce the production of matrix metalloproteinase 1 (MMP-1), but treatment with GABA resulted in the inhibition of MMP-1 production. We also investigated the enhancement of filaggrin and aquaporin 3 in keratinocytes after treatment with GABA, showing that GABA can effectively improve skin moisturization. In vivo experiments showed that oral administration of GABA significantly improved skin wrinkles and epidermal thickness. After the intake of GABA, there was a significant decrease observed in the increase of skin thickness measured by calipers and erythema. Additionally, the decrease in skin moisture and elasticity in hairless mice exposed to UVB radiation was also significantly restored. Overall, this study demonstrates the potential of GABA as functional food material for improving skin aging and moisturizing.

Non-invasive imaging of pathological scars using a portable handheld two-photon microscope.

Pathological scars are a disorder that can lead to various cosmetic, psychological, and functional problems, and no effective assessment methods are currently available. Assessment and treatment of pathological scars are based on cutaneous manifestations. A two-photon microscope (TPM) with the potential for real-time non-invasive assessment may help determine the under-surface pathophysiological conditions in vivo . This study used a portable handheld TPM to image epidermal cells and dermal collagen structures in pathological scars and normal skin in vivo to evaluate the effectiveness of treatment in scar patients. Fifteen patients with pathological scars and three healthy controls were recruited. Imaging was performed using a portable handheld TPM. Five indexes were extracted from two dimensional (2D) and three dimensional (3D) perspectives, including collagen depth, dermo-epidermal junction (DEJ) contour ratio, thickness, orientation, and occupation (proportion of collagen fibers in the field of view) of collagen. Two depth-dependent indexes were computed through the 3D second harmonic generation image and three morphology-related indexes from the 2D images. We assessed index differences between scar and normal skin and changes before and after treatment. Pathological scars and normal skin differed markedly regarding the epidermal morphological structure and the spectral characteristics of collagen fibers. Five indexes were employed to distinguish between normal skin and scar tissue. Statistically significant differences were found in average depth ( t = 9.917, P <0.001), thickness ( t = 4.037, P <0.001), occupation ( t = 2.169, P <0.050), orientation of collagen ( t = 3.669, P <0.001), and the DEJ contour ratio ( t = 5.105, P <0.001). Use of portable handheld TPM can distinguish collagen from skin tissues; thus, it is more suitable for scar imaging than reflectance confocal microscopy. Thus, a TPM may be an auxiliary tool for scar treatment selection and assessing treatment efficacy.

Effect of the Electric Field on the Biomineralization of Collagen.

Collagen/hydroxyapatite hybrids are promising biomimetic materials that can replace or temporarily substitute bone tissues. The process of biomineralization was carried out through a double diffusion system. The methodological principle consisted in applying an electric field on the incubation medium to promote the opposite migration of ions into collagen membranes to form hydroxyapatite (HA) on the collagen membrane. Two physically separated solutions were used for the incubation medium, one rich in phosphate ions and the other in calcium ions, and their effects were evaluated against the traditional mineralization in Simulated Body Fluid (SBF). Pre-polarization of the organic membranes and the effect of incubation time on the biomineralization process were also assessed by FTIR and Raman spectroscopies.Our results demonstrated that the membrane pre-polarization significantly accelerated the mineralization process on collagen. On the other side, it was found that the application of the electric field influenced the collagen structure and its interactions with the mineral phase. The increment of the mineralization degree enhanced the photoluminescence properties of the collagen/HA materials, while the conductivity and the dielectric constant were reduced. These results might provide a useful approach for future applications in manufacturing biomimetic bone-like materials.

Histological indicators of sheep skin of different directions of productivity

The purpose of the research was to study the histological indicators of sheep skin of different directions of productivity and to identify the effectiveness of using sheep of foreign breeds on the breeding stock of domestic fine-wooled sheep of the meat-wool direction of productivity. An analysis of histological indicators of sheep skin in diff erent areas of productivity, including the histostructure of the skin of sheep breeds of foreign selection such as Poll Dorset, Charolais and Ile de France, sheep breeds of domestic selection Stavropol, Manych merino and Dzhalginsky merino has been presented in the article. The study of the mechanism of growth and development of wool fi bers is one of the main tasks of increasing the quantity and improving the quality of wool. In studying the morphology of the skin, it is important to establish the breed and age features of the structure of the root, glandular systems, collagen structures that ensure the quality of sheep skin and wool fi bers. Thus, in sheep of Poll Dorset breed the total skin thickness was 10,3 and 3,6 % higher than in Charolais and Ile-de-France animals, respectively. At the same time, the thickness of the epidermis was almost 1,0 % of the total thickness of the skin, while the pilar layer averaged 61,8 %, the reticular layer 37,23 %, which is consistent with the breed parameters. The biggest density of follicles was observed in sheep of Ile-de-France and Charolais breeds. The superiority over animals of Poll Dorset breed was 17,5 and 10,0 %, respectively. By the ratio of secondary follicles/primary follicles animals of Poll Dorset and Ile-de-France breeds had superiority over Charolais breed by an average of 12,4 and 11,2 %. Sheep of domestic selection had an advantage in skin thickness in animals of Manych merino breed. They surpassed their herdmates of Stavropol breed by 5,2 % and Dzhalginsky merino breed by 11,2 %. In terms of the total density of follicles, animals of Stavropol breed had a slight advantage. The animals of Manych merino breed were 3,2 % inferior to them and Dzhalginsky merino by 1,4 %. There was no diff erence between the breeds by the ratio of secondary follicles/primary follicles.

Single-cell transcriptome sequencing–based analysis: probing the mechanisms of glycoprotein NMB regulation of epithelial cells involved in silicosis

Chronic exposure to silica can lead to silicosis, one of the most serious occupational lung diseases worldwide, for which there is a lack of effective therapeutic drugs and tools. Epithelial mesenchymal transition plays an important role in several diseases; however, data on the specific mechanisms in silicosis models are scarce. We elucidated the pathogenesis of pulmonary fibrosis via single-cell transcriptome sequencing and constructed an experimental silicosis mouse model to explore the specific molecular mechanisms affecting epithelial mesenchymal transition at the single-cell level. Notably, as silicosis progressed, glycoprotein non-metastatic melanoma protein B (GPNMB) exerted a sustained amplification effect on alveolar type II epithelial cells, inducing epithelial-to-mesenchymal transition by accelerating cell proliferation and migration and increasing mesenchymal markers, ultimately leading to persistent pulmonary pathological changes. GPNMB participates in the epithelial-mesenchymal transition in distant lung epithelial cells by releasing extracellular vesicles to accelerate silicosis. These vesicles are involved in abnormal changes in the composition of the extracellular matrix and collagen structure. Our results suggest that GPNMB is a potential target for fibrosis prevention.

Experimental study of the effect of temperature on collagen conformational changes in skin tissue welded by femtosecond laser

In this study, in vitro skin tissues were welded using various laser settings at four temperature ranges, 30–40 °C, 40–60 °C, 60–80 °C, and > 80 °C., Raman spectra between 500 and 2000 cm−1 were examined in order to examine the relationship between the changes of collagen and the mechanical properties of skin tissue bonding and the degree of thermal damage of tissue. How collagen in skin tissues changed into disordered and less stable structures due to the thermal damage, and how the structure of protein and amino acid-related bands changed with increasing temperature were analyzed. Analysis of the deconvolution of the amide I band (1580–1720 cm−1) and the secondary structure of collagen showed that the secondary structure of collagen changed from α-like helix-dominated to β-aggregate-dominated structures due to the thermal damage. As the temperature increased, the number of protein molecule chain dissociation and reconnection within the skin tissue increased, which contributed to the improvement of the tensile strength of the skin after welding. However, when the temperature was too high, the collagen structure presented an extremely unstable state, and the degree of protein denaturation increased, causing serious thermal damage. When the skin tissue was welded using the femtosecond laser process parameters of laser power of 18 W, scanning speed of 50 mm/s, and scanning 50 times, the tensile strength of the in vitro skin tissue incision was greater and the degree of protein denaturation was less. The degree of thermal damage characterized by the degree of protein denaturation was consistent with that characterized by the microstructure texture characteristics parameters of the skin tissue.

Influence of Staphylococcus epidermidis on Collagen Crimp Patterns of Soft Tissue Allograft

Background: Postoperative infections, commonly from Staphylococcus epidermidis, may result in anterior cruciate ligament graft failure and necessitate revision surgery. In biomechanical studies, S. epidermidis has been shown to establish biofilms on tendons and reduce graft strength. Purpose/Hypothesis: The goal of this study was to determine the effect of bacterial bioburden on the collagen structure of tendon. It was hypothesized that an increase in S. epidermidis biofilm would compromise tendon crimp, a pattern necessary for mechanical integrity, of soft tissue allografts. Study design: Controlled laboratory study. Methods: Cultures of S. epidermidis were used to inoculate tibialis anterior cadaveric tendons. Conditions assessed included 5 × 105 colony-forming units or concentrated spent media from culture (no living bacteria). Incubation times of 30 minutes, 3 hours, 6 hours, and 24 hours were utilized. Second-harmonic generation imaging allowed for visualization of collagen autofluorescence. Crimp lengths were determined using ImageJ and compared based on incubation time. Results: Incubation time positively correlated with increasing S. epidermidis bioburden. Both fine and coarse crimp patterns lengthened with increasing incubation time. Significant coarse crimp changes were observed after only 30-minute incubations (P < .029), whereas significant fine crimp lengthening occurred after 6 hours (P < .0001). No changes in crimp length were identified after incubation in media lacking living bacteria. Conclusion: The results of this study demonstrate that exposure to S. epidermidis negatively affects collagen crimp structure. Structural alterations at the collagen fiber level occur within 30 minutes of exposure to media containing S. epidermidis. Clinical Relevance: Our study highlights the need for antimicrobial precautions to prevent graft colonization and maximize graft mechanical strength.