Estimation of a minimum laser power with wavelengths of 1.47, 1.56, and 1.68 μm for efficient obliteration of varicose veins

Experiments modelling endovenous laser obliteration (EVLO) are performed. As a result, laser radiation powers Pc at which collagen denaturation, tissue necrosis, and vasa vasorum destruction occur throughout the entire venous-wall thickness and, at the same time, the surrounding tissues are not subjected to unnecessary heating, are found. The main criterion for determining Pc is the achievement of 100% denaturation of venous-wall proteins, confirmed by morphological and calorimetric analysis. The Pc values for laser wavelengths of 1.47, 1.56, and 1.68 mm are found to be 6.0 ± 0.2, 5.0 ± 0.2, and 6.0 ± 0.2 W, respectively. It is established for all wavelengths in use that the temperature of the external venous-wall surface reaches 91 plusmn; 2 deg;C at the corresponding power Pc. We relate the dependence of Pc on the radiation wavelength to the formation of a coagulum on the optical fibre tip moving through a blood-filled vessel. The achievement of temperature necessary for coagulum formation is determined by the simultaneously occurring processes of energy absorption and its dissipation in the form of heat. These processes become more intense with an increase in the absorption coefficient of the medium. A mechanism is proposed to explain the relationship between the Pc value and laser wavelength, based on the influence of the absorption coefficient of medium (blood) on the temperature near the fibre tip.

A Rapid and Convenient Approach to Construct Porous Collagen Membranes via Bioskiving and Sonication-Feasible for Mineralization to Induce Bone Regeneration

Porous mineralized collagen membranes efficiently promote bone regeneration. To generate them, we need to fabricate collagen membranes that are porous. However, the current fabrication method is primarily based on a bottom-up strategy, with certain limitations, such as a long manufacturing process, collagen denaturation, and failure to control fibril orientation. Using a top-down approach, we explore a novel method for constructing porous collagen membranes via the combined application of bioskiving and sonication. Numerous collagen membranes with well-aligned fibril structures were rapidly fabricated by bioskiving and then sonicated at 30, 60, 90, and 120 W for 20 min. This treatment allowed us to study the effect of power intensity on the physicochemical traits of collagen membranes. Subsequently, the prepared collagen membranes were immersed in amorphous calcium phosphate to evaluate the feasibility of mineralization. Additionally, the bioactivities of the membranes were assessed using preosteoblast cells. Tuning the power intensity was shown to modulate fibril orientation, and the porous membrane without denatured collagen could be obtained by a 20-min sonication treatment at 90 W. The prepared collagen membrane could also be further mineralized to enhance osteogenesis. Overall, this study offers a rapid and convenient approach for fabricating porous collagen membranes via bioskiving and sonication.

The biaxial mechanics of thermally denaturing skin - Part I: Experiments

The mechanics of collageneous soft tissues, such as skin, are sensitive to heat. Thus, quantifying and modeling thermo-mechanical coupling of skin is critical to our understanding of skin's physiology, pathophysiology, as well as its treatment. However, key gaps persist in our knowledge about skin's coupled thermo-mechanics. Among them, we haven't quantified the role of skin's microstructural organization in its response to superphysiological loading. To fill this gap, we conducted a comprehensive set of experiments in which we combined biaxial mechanical testing with histology and two-photon imaging under liquid heat treatment. Among other observations, we found that unconstrained skin, when exposed to high temperatures, shrinks anisotropically with the principle direction of shrinkage being aligned with collagen's principle orientation. Additionally, we found that when skin is isometrically constrained, it produces significant forces during denaturing that are also anisotropic. Finally, we found that denaturation significantly alters the mechanical behavior of skin. For short exposure times, this alteration is reflected in a reduction of stiffness at high strains. At long exposure times, the tissue softened to a point where it became untestable. We supplemented our findings with confirmation of collagen denaturation in skin via loss of birefringence and second harmonic generation. Finally, we captured all time-, temperature-, and direction-dependent experimental findings in a hypothetical model. Thus, this work fills a fundamental gap in our current understanding of skin thermo-mechanics and will support future developments in thermal injury prevention, thermal injury management, and thermal therapeutics of skin.

Extraction of Type I Collagen from Tilapia Scales Using Acetic Acid and Ultrafine Bubbles

Type I collagen is commonly used in medical materials and cosmetics. While it can be extracted from the skin and bones of mammals, marine collagen has attracted attention recently, since the use of mammalian collagen could result in zoonosis, and products containing mammalian collagen are avoided due to some religious beliefs. Chemical extractions using strong acids and alkalis, thermal extractions, and other nonconventional methods have been used for collagen extraction. However, there are few reports on environmentally friendly methods. Although heat extractions provide higher yields of collagen, they often cause collagen denaturation. Therefore, dilute acetic acid and ultrafine bubbles of oxygen, carbon dioxide, and ozone were used to extract type I collagen from tilapia scales. The extraction performance of the different conditions employed was qualitatively analyzed by SDS-PAGE electrophoresis, and the collagen concentration was quantified using circular dichroism spectroscopy by monitoring the peak intensity at 221 nm, which is specific to the triple helix of type I collagen. Collagen was extracted from tilapia scales with a yield of 1.58% by the aeration of ultrafine bubbles of carbon dioxide gas in a 0.1 M acetic acid solution for 5 h.

Collagen/PCL Nanofibers Electrospun in Green Solvent by DOE Assisted Process. An Insight into Collagen Contribution

Collagen, thanks to its biocompatibility, biodegradability and weak antigenicity, is widely used in dressings and scaffolds, also as electrospun fibers. Its mechanical stability can be improved by adding polycaprolactone (PCL), a synthetic and biodegradable aliphatic polyester. While previously collagen/PCL combinations were electrospun in solvents such as hexafluoroisopropanol (HFIP) or trifluoroethanol (TFE), more recently literature describes collagen/PCL nanofibers obtained in acidic aqueous solutions. A good morphology of the fibers represents in this case still a challenge, especially for high collagen/PCL ratios. In this work, thanks to preliminary rheological and physicochemical characterization of the solutions and to a Design of Experiments (DOE) approach on process parameters, regular and dimensionally uniform fibers were obtained with collagen/PCL ratios up to 1:2 and 1:1 w/w. Collagen ratio appeared relevant for mechanical strength of dry and hydrated fibers. WAXS and FTIR analysis showed that collagen denaturation is related both to the medium and to the electrospinning process. After one week in aqueous environment, collagen release was complete and a concentration dependent stimulatory effect on fibroblast growth was observed, suggesting the fiber suitability for wound healing. The positive effect of collagen on mechanical properties and on fibroblast biocompatibility was confirmed by a direct comparison of nanofiber performance after collagen substitution with gelatin.

EKSTRAKSI GELATIN DARI TULANG IKAN KAKAP PUTIH (Lates calcarifer) DENGAN ASAM HCl

Extraction of Gelatin from Fish White Bone (Lates Calcarifer) with HCl Concentration Variance Gelatin is a food added ingredient used in emulsifiers, thickeners, food stabilizers. Gelatin is a type of protein in the form of gel obtained from the denaturation of skin, bone and fish tissue collagen denaturation. The process of making gelatin from the bones of white snapper (Lates calcarifer) uses the HCl acid method with the parameters of yield, water content, ash content, and protein content. The immersion process carried out with varoius of HCl acid concentration 3%, 7% and 11%.The results show that the best value of% yield at a concentration of 7% of 1.90%, 10.16% water content. Ash content 3%. Protein content is 3.25%. FTIR spectrum revealed the presence of amida group at wave number 3269 cm-1, amide I; II; and Amida III sequentially at wave number 1656 cm-1; 1525.69 cm-1; 1161.15 cm-1.Keywords : Gelatin ; collagen ; Lates calcarifer ; FTIRABSTRAK Gelatin merupakan bahan tambah pangan yang digunakan dalam pengemulsi, pengental, penstabil makanan. Gelatin merupakan salah satu jenis protein yang berbentuk gel yang didapatkan dari hasil denaturasi kolagen kulit, tulang dan jaringan ikan. Proses ekstrak gelatin dari bahan tulang ikan kakap putih (Lates calcarifer) menggunakan asam HCl dengan parameter rendemen, kadar air, kadar abu, kadar protein dan analisis FTIR. Proses perendaman dilakukan variasi asam HCl 3%, 7% dan 11%. Dari hasil penelitian didapatkan nilai % rendemen tertinggi pada konsentrasi 7% sebesar 1,90%, dengan nilai kadar air 10,16%, kadar abu 3,00%, kadar protein 3,25%. Dari spektrum FTIR didapatkan gugus Amida A pada bilangan gelombang 3269 cm-1, amida I ; II ; dan amida III secara berturut-turut pada bilangan gelombang 1656 cm-1 ; 1525,69 cm-1 ; 1161,15 cm-1.Kata kunci : Gelatin ; ikan kakap putih ; FTIR

Physical disruption of intervertebral disc promotes cell clustering and a degenerative phenotype

To test the hypothesis that physical disruption of an intervertebral disc disturbs cell-matrix binding, leading to cell clustering and increased expression of matrix degrading enzymes that contribute towards degenerative disc cell phenotype. Lumbar disc tissue was removed at surgery from 21 patients with disc herniation, 11 with disc degeneration, and 8 with adolescent scoliosis. 5 μm sections were examined with histology, and 30-µm sections by confocal microscopy. Antibodies were used against integrin α5beta1, matrix metalloproteinases (MMP) 1, MMP-3, caspase 3, and denatured collagen types I and II. Spatial associations were sought between cell clustering and various degenerative features. An additional, 11 non-herniated human discs were used to examine causality: half of each specimen was cultured in a manner that allowed free ‘unconstrained’ swelling (similar to a herniated disc in vivo), while the other half was cultured within a perspex ring that allowed ‘constrained’ swelling. Changes were monitored over 36 h using live-cell imaging. 1,9-Di-methyl methylene blue (DMMB) assay for glycosaminoglycan loss was carried out from tissue medium. Partially constrained specimens showed little swelling or cell movement in vitro. In contrast, unconstrained swelling significantly increased matrix distortion, glycosaminoglycan loss, exposure of integrin binding sites, expression of MMPs 1 and 3, and collagen denaturation. In the association studies, herniated disc specimens showed changes that resembled unconstrained swelling in vitro. In addition, they exhibited increased cell clustering, apoptosis, MMP expression, and collagen denaturation compared to ‘control’ discs. Results support our hypothesis. Further confirmation will require longitudinal animal experiments.