scholarly journals Heterogeneous strains in tissue collagen show that high strains locally suppress degradation by collagenase

2021 ◽  
Author(s):  
K. Saini ◽  
M. Tiwari ◽  
S. Cho ◽  
A. Jalil ◽  
M. Vashisth ◽  
...  
Keyword(s):  
Physical Properties ◽  
Degradation Rate ◽  
Molecular Level ◽  
Second Harmonic ◽  
Mechanical Strain ◽  
Collagen Content ◽  
Peak Strain ◽  
Tendon Tissue ◽  
Physiological Strain ◽  
Matrix Metalloproteinase 1

AbstractCollagen, the most abundant protein in mammals, contributes to the physical properties of different tissues during development, homeostasis, and disease. The adaptation of physical properties of tissues to mechanical stimuli is thus dependent on the control of tissue collagen levels by well-regulated synthesis and degradation of collagen. Importantly, how various molecular-level events within a tissue sustaining a range of mechanical strains contribute towards maintaining its collagen levels, remains unclear to date. Such molecular level processes in tissues are studied here in the case of isolated tendons consisting of collagen fibrils oriented along tissue loading-axis and beating embryonic hearts to gain understanding of mechanical load dependent tissue sculpting. Using a novel bioreactor design, starved mice tail tendon fascicles were used as a “cell-free” model and were subjected to heterogeneous and uniaxial deformation modes. Patterned photobleaching of fluorescent probes, a novel Aza-peptide or dye, on fascicles used to quantify tissue strains. Tissue microstructure was simultaneously imaged using second harmonic generation (SHG) signal to assess tissue collagen content while deformed fascicle samples were exposed to purified matrix metalloproteinase-1 (MMP-1) or bacterial collagenase (BC). A decrease in the degradation rate (relative to strain-free) was observed for physiological strain limits of tendon tissue (i.e. ∼5-8%) while at higher strains (i.e. pathological) the degradation rate was independent of strain magnitude changes. Interestingly, the strain dependence of degradation rate was independent of cleavage-site specificity of the collagenase molecules and the mode of tendon tissue deformation. Although spatially different within a tissue sample, the values of strain, degradation rate and collagen fiber organization with time during degradation of each tendon fascicle region were highly correlated. Tendon regions dominated by collagen fibers inclined to fascicle-axis were observed to follow non-affine deformation. The dependence of the degradation rate on mechanical strain is due to sequestration of collagen cleavage sites within fibrils. Permeation, tissue mass density and mobility of fluorescent collagenase and dextran are strain-independent for fascicle strains up to ∼5-8% while the degradation rate is positively correlated to unfolded triple-helical collagen content. Normal beating chick hearts subjected to ∼5% peak strain in a spatiotemporal coordinate contractile wave were observed to maintain their collagen mass until the beating strain is suppressed by inhibition of myosin-II. Based on the presence of exogeneous MMP inhibitors, endogenous MMPs within the non-beating hearts degrade the collagens immediately (in ∼30-60 mins). Both tissue systems under mechanical strains suggest degradative sculpting where mechanical strain-dependent collagen fibril architecture changes appear to play a key role in determining collagen lifetime within tissues.Graphical abstract

Synthesis and Properties of Biodegradable Liquid Crystalline Poly(ester-Urethane)s Based on Poly(L-Lactic Acid)

2013 ◽  
Vol 652-654 ◽  
pp. 459-462
Author(s):  
Ya Tong Guo ◽  
Zhu Zheng ◽  
Zhen Qi Hou ◽  
Jie Du
Keyword(s):  
Phase Transition ◽  
Thermal Stability ◽  
Lactic Acid ◽  
Physical Properties ◽  
Liquid Crystalline ◽  
Degradation Rate ◽  
Hydrolytic Degradation ◽  
Hexamethylene Diisocyanate ◽  
Solution Polymerization ◽  
Phase Transition Temperatures

A series of biodegradable segmented liquid crystalline poly(ester-urethane)s were prepared by solution polymerization of poly(L-lactic acid) (PLLA), mesogenic diol prepolymer poly(butylene terephthaloyldioxy dibenzoates) (MD), and hexamethylene diisocyanate (HDI). The MD content was varied from 0 to 40 mol% so that the effects of the mesogen content on the thermal and physical properties, and hydrolytic degradation were examined respectively. It was found that introducing mesogens units could increase the thermal stability and the elastic properties, while reduced the phase transition temperatures and the hydrolytic degradation rate.

Measurement of bone surface strains on the sheep metacarpus in vivo and ex vivo

2003 ◽  
Vol 16 (01) ◽  
pp. 38-43 ◽  
Author(s):  
R. Steck ◽  
C. Gatzka ◽  
E. Schneider ◽  
P. Niederer ◽  
M. L. Tate
Keyword(s):  
Ex Vivo ◽  
Longitudinal Axis ◽  
Peak Strain ◽  
Bone Surface ◽  
Interstitial Fluid Flow ◽  
Ex Vivo Model ◽  
Physiological Strain ◽  
Bending Load ◽  
Walking Speeds

SummaryBone surface strains were measured on the dorsal ovine metacarpus during normal locomotion on a treadmill at different walking speeds to determine physiological strain levels. These measured strains were related to the strains measured in an ex vivo model of the sheep forelimb with two types of load application: loading by two Schanz-screws and loading via the radius. In vivo, the average surface strains were found to be dependent upon body weight as well as the walking speed. The orientation of the peak principal strain corresponded to the longitudinal axis of the bone. Ex vivo, loads applied via Schanz screws in the screw-loading model lead to strains on the dorsal metacarpus that corresponds to strains experienced in vivo during intermittent peak loads. Screw loading imparted primarily a bending load to the metacarpus, with the dorsal aspect in compression and the palmar aspect in tension. Loads, applied via the radius and the hoof in the radius-loading model, resulted in bone surface strains comparable to those measured during slow walking in vivo. In both ex vivo loading situations, peak strain orientation was parallel to the longitudinal axis of the sheep metacarpus. In conclusion, the results show that although the ex vivo loading models do not exactly replicate the load experienced in vivo, the magnitude and orientation of the principal strains on the dorsal metacarpus are within the range of strains occurring during normal physiological loading. These data validate the physiological significance of the ex vivo model and aid in understanding effects of mechanical loading on interstitial fluid flow and mass transport through bone.

Gastrointestinal mucus, a medium for survival and for elimination of parasitic nematodes and protozoa

Parasitology ◽  
1987 ◽  
Vol 94 (S1) ◽  
pp. S77-S100 ◽  
Author(s):  
H. R. P. Miller
Keyword(s):  
Physical Properties ◽  
Elastic Material ◽  
Molecular Level ◽  
Mucosal Surface ◽  
Parasitic Nematodes ◽  
Physical Injury ◽  
Mucin Glycoproteins ◽  
Mucosal Surfaces ◽  
Additional Support

Mucus is a sticky visco-elastic material which coats all mucosal surfaces. Florey, in 1955, noted the following three functions for gastrointestinal mucus: protection of the underlying mucosa from chemical and physical injury, lubrication of the mucosal surface to facilitate passage of luminal contents, and removal of parasites by binding and entrapment. In the 31 years since Florey's review, detailed analyses of the composition of mucus and of the biochemistry of mucin glycoproteins, as well as measurements of the physical properties of mucus from different organs and sites have yielded information at the molecular level which provide additional support for his views on its function (Allen, 1981; Forstner, Wesley & Forstner, 1982).

scholarly journals The Stiffness of Cardiac Fibroblast Substrates Exerts a Regulatory Influence on Collagen Metabolism via α2β1 Integrin, FAK and Src Kinases

Cells ◽  
2021 ◽  
Vol 10 (12) ◽  
pp. 3506
Author(s):  
Małgorzata Gałdyszyńska ◽  
Paulina Radwańska ◽  
Jacek Szymański ◽  
Jacek Drobnik
Keyword(s):  
Cardiac Fibroblasts ◽  
Substrate Inhibition ◽  
Mechanical Strain ◽  
Collagen Metabolism ◽  
Collagen Content ◽  
Substrate Stiffness ◽  
Type I ◽  
Src Kinases ◽  
Downstream Signaling ◽  
Regulatory Influence

Information about mechanical strain in the extracellular space is conducted along collagen fibers connected with integrins and then transmitted within cells. An aim of the study is to verify the hypothesis that the stiffness of cardiac human fibroblast substrates exerts a regulatory effect on collagen metabolism via integrin α2β1 and downstream signaling. The experiments were performed on human cardiac fibroblasts cultured on stiff or soft polyacrylamide gels. Extracellular and intracellular collagen content, metalloproteinase-1 (MMP-1), metalloproteinase-9 (MMP-9) and expression of the α1 chain of the procollagen type I gene (Col1A1) were elevated in cultures settled on soft substrate. The substrate stiffness did not modify tissue inhibitors of matrix metalloproteinase capacity (TIMPs 1–4). Integrin α2β1 inhibition (TC-I 15) or α2 subunit silencing resulted in augmentation of collagen content within the culture. Expression of Col1A1 and Col3A1 genes was increased in TC-I 15-treated fibroblasts. Total and phosphorylated levels of both FAK and Src kinases were elevated in fibroblasts cultured on stiff substrate. Inhibition of FAK (FAK kinase inhibitor 14) or Src kinase (AZM 47527) increased collagen content within the culture. The substrate stiffness exerted a regulatory influence on collagen metabolism via integrin α2β1 and its downstream signaling (FAK and Src kinases) in cardiac fibroblasts.

Physico-chemical Effects of Gelatin Addition in Carboxymethylcellulose and Calcium Phosphate Cement-based Nanocomposites

MRS Advances ◽  
2019 ◽  
Vol 4 (46-47) ◽  
pp. 2453-2459
Author(s):  
Esra Güben ◽  
Duygu Ege
Keyword(s):  
Mechanical Properties ◽  
Liquid Phase ◽  
Calcium Phosphate ◽  
Physical Properties ◽  
Biomedical Applications ◽  
Degradation Rate ◽  
Mechanical Tests ◽  
Physical Interaction ◽  
Gel Structure ◽  
Physico Chemical

Abstract:Nanocomposites comprising of biopolymers and calcium phosphate cements (CaP) are promising due to their biocompatibility, non-toxicity, biodegradability and suitable mechanical properties for biomedical applications. In here, a new composite material was synthesized with carboxymethylcellulose (CMC) and gelatin (GEL) as the liquid phase and CaP based powder as the solid phase. In this study, the effect of addition of different wt% of GEL including 0, 5, 10, 20 in the liquid phase was investigated on the physical properties of the nanocomposites. Physico-chemical characteristics of materials were determined by using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and mechanical tests. Swelling analysis was performed after 1, 8, 16, 24 and 48 hours and degradation of samples was studied after 7 and 14 days. FTIR results showed that there was physical interaction between CMC and GEL with H bonding which was evident from the peak at 3288cm-1. Disruption in GEL structure was observed from the band at 1600-1400 cm-1 Disruption of GEL structure may increase the interaction between CMC and GEL molecules. After mixing of solid and liquid phases, negative charged COO- groups on CMC and Ca2+ molecules from CaP start to interact with each other. This produces attraction sites for PO43- molecules. This lead to accumulation of hydroxyapatite-like structures. A homogenous and porous microstructure was observed by using SEM in all samples. Mechanical tests showed that GEL improved the strength of the samples up to 20 wt% of GEL. The addition of 20 wt% of GEL decreased the mechanical properties. The compressive strength values were found up to approximately 6 MPa. Swelling results revealed that increasing in GEL concentration cause decrease in swelling until the 16th hour, after that 10wt% GEL samples had the lowest swelling which was approximately 28%. Finally, degradation studies indicated that the highest degradation rate was for 10% GEL incorporated samples. Addition of further GEL also reduced the degradation rate. Overall, the addition of GEL improved physical properties of the samples for potential biomedical applications.

scholarly journals Direct molecular level characterization of different heterogeneous freezing modes on mica

2017 ◽  
Author(s):  
Ahmed Abdelmonem
Keyword(s):  
Molecular Level ◽  
Second Harmonic ◽  
Ice Nucleation ◽  
Oxide Surface ◽  
Transient Phase ◽  
Weather Modification ◽  
Phase Liquid ◽  
Nonlinear Signal ◽  
Second Harmonic Generation Spectroscopy

Abstract. The mechanisms behind heterogeneous ice nucleation are of fundamental importance to the prediction of the occurrence and properties of many cloud types, which influence climate and precipitation. Aerosol particles act as cloud condensation and freezing nuclei. The surface-water interaction of an ice nucleation particle plays a major, not well explored, role in its ice nucleation ability. This paper presents a real–time–molecular–level comparison of different freezing modes on the surface of an atmospherically relevant metal oxide surface (mica) under varying supersaturation conditions using second harmonic generation spectroscopy. Two sub-deposition nucleation modes were identified (one- and two-stage freezing). The nonlinear signal at water-mica interface was found to drop upon the formation of a thin film on the surface regardless of 1) the formed phase (liquid or ice) and 2) the freezing path (one- or two-step), indicating similar molecular structuring. The results also revealed a transient phase of ice at water-mica interfaces during freezing, which has a lifetime of around one minute. Such information will have a significant impact on climate change, weather modification, and tracing of water in hydrosphere studies.

Structure and properties of organic liquid crystals

1993 ◽  
Vol 51 ◽  
pp. 656-657
Author(s):  
I.G. Voigt-Martin
Keyword(s):  
Liquid Crystals ◽  
Physical Properties ◽  
Molecular Conformation ◽  
Phase Transfer ◽  
Second Harmonic ◽  
Organic Liquid ◽  
Molecular Characteristics ◽  
Electronic Charge ◽  
Imaging Method ◽  
Contrast Imaging

Organic liquid crystals (LCs), both in the monomeric and polymeric state, are capable of self organisation because of the anisotropic shape of their molecules. By suitable molecular engineering it is thus possible to induce interesting physical properties like ferroelectricity, second harmonic generation (SHG) and photoconductivity. For a deeper understanding it is necessary to gain insight into the relationship between molecular characteristics (electronic charge distribution, dipole moments, hyperpolarisabilities, molecular conformation), structural relations (symmetry relations, space groups, defects) and the above physical propertiesFor structure analysis electron diffraction patterns from different crystallographic zones with many higher orders of diffraction are required. Unfortunately a characteristic feature of LCs is their loss of all higher order reflections and a change in symmetry. Furthermore, LCs give rise to specific defects, which give important information about the elastic energy density of the system. These can only be characterised by a phase contrast imaging method in which the small angle spatial frequencies are transferred by the electron microscope phase transfer function.

scholarly journals Marine Biomaterial-Based Bioinks for Generating 3D Printed Tissue Constructs

Marine Drugs ◽  
2018 ◽  
Vol 16 (12) ◽  
pp. 484 ◽  
Author(s):  
Xiaowei Zhang ◽  
Gyeong Kim ◽  
Min Kang ◽  
Jung Lee ◽  
Jeong Seo ◽  
...  
Keyword(s):  
Tissue Engineering ◽  
Mechanical Strength ◽  
Physical Properties ◽  
Degradation Rate ◽  
Polymer Network ◽  
Three Dimensional ◽  
Pharmaceutical Products ◽  
Biologically Active ◽  
Interpenetrating Polymer Network ◽  
Biomedical Fields

Biologically active materials from marine sources have been receiving increasing attention as they are free from the transmissible diseases and religious restrictions associated with the use of mammalian resources. Among various other biomaterials from marine sources, alginate and fish gelatin (f-gelatin), with their inherent bioactivity and physicochemical tunability, have been studied extensively and applied in various biomedical fields such as regenerative medicine, tissue engineering, and pharmaceutical products. In this study, by using alginate and f-gelatin’s chemical derivatives, we developed a marine-based interpenetrating polymer network (IPN) hydrogel consisting of alginate and f-gelatin methacryloyl (f-GelMA) networks via physical and chemical crosslinking methods, respectively. We then evaluated their physical properties (mechanical strength, swelling degree, and degradation rate) and cell behavior in hydrogels. Our results showed that the alginate/f-GelMA hydrogel displayed unique physical properties compared to when alginate and f-GelMA were used separately. These properties included high mechanical strength, low swelling and degradation rate, and an increase in cell adhesive ability. Moreover, for the first time, we introduced and optimized the application of alginate/f-GelMA hydrogel in a three-dimensional (3D) bioprinting system with high cell viability, which breaks the restriction of their utilization in tissue engineering applications and suggests that alginate/f-GelMA can be utilized as a novel bioink to broaden the uses of marine products in biomedical fields.

Surface-Site Charge-Displacement Model for Analysis of Electromodulated Optical Second-Harmonic Response at a Metal Surface

1998 ◽  
Vol 52 (9) ◽  
pp. 1240-1247 ◽  
Author(s):  
S. G. Lambrakos ◽  
P. P. Trzaskoma-Paulette ◽  
I. A. Triandaf
Keyword(s):  
Nonlinear Response ◽  
Molecular Level ◽  
Second Harmonic ◽  
Functional Dependence ◽  
Model Representation ◽  
Local Surface ◽  
Harmonic Response ◽  
Dc Electric Field ◽  
Charge Displacement ◽  
Displacement Model

We present an analysis of second-harmonic (SH) response from metal surfaces that is based on a model representation whose associated parameters are defined in terms of nonlinear polarizabilities originating from charge displacement occurring on a molecular level. Our analysis suggests that the general functional dependence of SH response at a metal/electrolyte interface on the time-independent (dc) electric field is typically different from that implied by previous models. The analysis shows that our model representation is sufficiently general for extracting features from second-harmonic generation (SHG) data in order to analyze such data by methods based on system identification and pattern recognition. Our model, which is based on a classical representation of the nonlinear response of bound (or constrained) charge, is found to be consistent with trends observed in experimental measurements of second-harmonic response as a function of surface charge density. The results of this analysis suggest that SH data are relatively rich in terms of features that can be correlated with local surface structure and that the data should be interpreted by means of a more general model representation than has been previously proposed.

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