Viscoelastic properties
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The viscoelastic properties of biological membranes are crucial in controlling cellular functions and are determined primarily by the lipids' composition and structure. This work studies these properties by varying the structure of the constituting lipids in order to influence their interaction with high-density lipoprotein (HDL) particles. Various fluorescence-based techniques were applied to study lipid domains, membrane order, and the overall lateral as well as the molecule-internal glycerol region mobility in HDL-membrane interactions (i.e., binding and/or cargo transfer). The analysis of interactions with HDL particles and various lipid phases revealed that both fully fluid and some gel-phase lipids preferentially interact with HDL particles, although differences were observed in protein binding and cargo exchange. Both interactions were reduced with ordered lipid mixtures containing cholesterol. To investigate the mechanism, membranes were prepared from single-lipid components, enabling step-by-step modification of the lipid building blocks. On a biophysical level, the different mixtures displayed varying stiffness, fluidity, and hydrogen bond network changes. Increased glycerol mobility and a strengthened hydrogen bond network enhanced anchoring interactions, while fluid membranes with a reduced water network facilitated cargo transfer. In summary, the data indicate that different lipid classes are involved depending on the type of interaction, whether anchoring or cargo transfer.
- Publikační typ
- časopisecké články MeSH
Understanding the mechanics of the respiratory system is crucial for optimizing ventilator settings and ensuring patient safety. While simple models of the respiratory system typically consider only flow resistance and lung compliance, lung tissue resistance is usually neglected. This study investigated the effect of lung tissue viscoelasticity on delivered mechanical power in a physical model of the respiratory system and the possibility of distinguishing tissue resistance from airway resistance using proximal pressure measured at the airway opening. Three different configurations of a passive physical model of the respiratory system representing different mechanical properties (Tissue resistance model, Airway resistance model, and No-resistance model) were tested. The same volume-controlled ventilation and parameters were set for each configuration, with only the inspiratory flow rates being adjusted. Pressure and flow were measured with a Datex-Ohmeda S/5 vital signs monitor (Datex-Ohmeda, Madison, WI, USA). Tissue resistance was intentionally tuned so that peak pressures and delivered mechanical energy measured at airway opening were similar in Tissue and Airway Resistance models. However, measurements inside the artificial lung revealed significant differences, with Tissue resistance model yielding up to 20% higher values for delivered mechanical energy. The results indicate the need to revise current methods of calculating mechanical power delivery, which do not distinguish between tissue resistance and airway flow resistance, making it difficult to evaluate and interpret the significance of mechanical power delivery in terms of lung ventilation protectivity.
A film-forming system (FFS) represents a convenient topical dosage form for drug delivery. In this study, a non-commercial poly(lactic-co-glycolic acid) (PLGA) was chosen to formulate an FFS containing salicylic acid (SA) and methyl salicylate (MS). This unique combination is advantageous from a therapeutic point of view, as it enabled modified salicylate release. It is beneficial from a technological perspective too, because it improved thermal, rheological, and adhesive properties of the in situ film. DSC revealed complete dissolution of SA and good miscibility of MS with the polymer. MS also ensures optimal viscoelastic and adhesive properties of the film, leading to prolonged and sustained drug release. The hydrolysis of MS to active SA was very slow at skin pH 5.5, but it apparently occurred at physiological pH 7.4. The film structure is homogeneous without cracks, unlike some commercial preparations. The dissolution study of salicylates revealed different courses in their release and the influence of MS concentration in the film. The formulated PLGA-based FFS containing 5 % SA and 10 % MS is promising for sustained and prolonged local delivery of salicylates, used mainly for keratolytic and anti-inflammatory actions and pain relief.
- MeSH
- aplikace kožní MeSH
- aplikace lokální MeSH
- farmaceutická chemie metody MeSH
- koncentrace vodíkových iontů MeSH
- kopolymer kyseliny glykolové a mléčné * chemie MeSH
- kůže metabolismus MeSH
- kyselina mléčná * chemie MeSH
- kyselina polyglykolová * chemie MeSH
- kyselina salicylová * aplikace a dávkování chemie farmakokinetika MeSH
- lékové transportní systémy * metody MeSH
- léky s prodlouženým účinkem MeSH
- rozpustnost MeSH
- salicylany * aplikace a dávkování chemie farmakokinetika MeSH
- uvolňování léčiv MeSH
- Publikační typ
- časopisecké články MeSH
BACKGROUND: The purpose of dermal substitutes is to mimic the basic properties of the extracellular matrix of human skin. The application of dermal substitutes to the defect reduces the formation of hypertrophic scars and improves the scar quality. This study aims to develop an original dermal substitute enriched with stable fibroblast growth factor 2 (FGF2-STAB®) and test it in an animal model. METHODS: Dermal substitutes based on collagen/chitosan scaffolds or collagen/chitosan scaffolds with nanofibrous layer were prepared and enriched with FGF2-STAB® at concentrations of 0, 0.1, 1.0, and 10.0 μg ‧ cm-2. The performance of these dermal substitutes was tested in vivo on artificially formed skin defects in female swine. The outcomes were evaluated using cutometry at 3 and 6 months. In addition, visual appearance was assessed based on photos of the scars at 1-month, 3-month and 6-month follow-ups using Yeong scale and Visual Analog Scale. RESULTS: The dermal substitute was fully integrated into all defects and all wounds healed successfully. FGF2-STAB®-enriched matrices yielded better results in cutometry compared to scaffolds without FGF2. Visual evaluation at 1, 3, and 6 months follow-ups detected no significant differences among groups. The FGF2-STAB® effectiveness in improving the elasticity of scar tissues was confirmed in the swine model. This effect was independently observed in the scaffolds with nanofibres as well as in the scaffolds without nanofibres. CONCLUSION: The formation of scars with the best elasticity was exhibited by addition 1.0 μg ‧ cm-2of FGF2-STAB® into the scaffolds, although it had no significant effect on visual appearance at longer follow-ups. This study creates the basis for further translational studies of the developed product and its progression into the clinical phase of the research.
- MeSH
- chitosan * MeSH
- fibroblastový růstový faktor 2 * MeSH
- hojení ran účinky léků MeSH
- jizva hypertrofická MeSH
- kolagen MeSH
- kůže MeSH
- modely nemocí na zvířatech MeSH
- nanovlákna terapeutické užití MeSH
- popálení MeSH
- prasata MeSH
- pružnost * MeSH
- tkáňové podpůrné struktury MeSH
- umělá kůže * MeSH
- viskozita MeSH
- zvířata MeSH
- Check Tag
- ženské pohlaví MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
Kyselina hyaluronová (KH) je lineární, přirozeně se vyskytující polysacharid o vysoké molekulové hmotnosti. Je součástí řady bio logických procesů, zejména regulačních, protizánětlivých, imunosupresivních nebo antiproliferativních. Významně váže vodu a podílí se na udržování viskoelasticity tkání, na supramolekulárním prostorovém uspořádání proteoglykanů v extracelulární matrix a na regulaci osmotického tlaku, což významně ovliňuje homogenitu tkáně a její homeostatickou integritu. Díky těmto vlastnostem lze neimunogenní KH použít v mnoha klinických aplikacích. V otorinolaryngologii jsou možnosti jejího využití široké zejména v otologii, laryngologii, rinologii nebo při léčbě zánětlivý stavů a keloidních jizev. Ně kte ré potenciální oblasti využití jsou stále ve stadiu experimentu (genová terapie).
Hyaluronic acid (HA) is a linear, naturally occurring polysaccharide of high molecular weight. It is part of a number of bio logical processes, especially regulatory, anti-inflammatory, immunosuppressive or antiproliferative. It significantly binds water and participates in the maintenance of tissue viscoelasticity, in the supramolecular spatial arrangement of proteoglycans in the extracellular matrix and in the regulation of osmotic pressure, which significantly affects tissue homogeneity and its homeostatic integrity. Due to these properties, non-immunogenic HA can be used in many clinical applications. In otorhinolaryngology, the possibilities of its use are wide, especially in otology, laryngology, rhinology or in the treatment of inflammatory conditions and keloid scars. Some potential areas of use are still in the experimental stage (gene therapy).
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.
- Publikační typ
- časopisecké články MeSH
New studies have shown the great potential of the combination of in situ enzymatically cross-linked hydrogels based on tyramine derivative of hyaluronic acid (HA-TA) with platelet-rich plasma (PRP) and platelet lysate in regenerative medicine. This study describes how the presence of PRP and platelet lysate affects the kinetics of gelation, viscoelastic properties, swelling ratio, and the network structure of HA-TA hydrogels and how the encapsulation of PRP in hydrogels affects the bioactivity of released PRP determined as the ability to induce cell proliferation. The properties of hydrogels were tuned by a degree of substitution and concentration of HA-TA derivatives. The addition of platelet derivatives to the reaction mixture slowed down the cross-linking reaction and reduced elastic modulus (G') and thus cross-linking efficiency. However, low-swellable hydrogels (7-190%) suitable for soft tissue engineering with G' 200-1800 Pa were prepared with a gelation time within 1 min. It was confirmed that tested cross-linking reaction conditions are suitable for PRP incorporation because the total bioactivity level of PRP released from HA-TA hydrogels was ≥87% and HA-TA content in the hydrogels and thus mesh size (285-482 nm) has no significant effect on the bioactivity level of released PRP.
A study of mechanical properties of native tissues is a great challenge in biomechanics. Especially, hardly accessible structures that play a very important role within a locomotive system. A study of a cartilaginous endplate (CEP) is just such a challenge. CEP is approximately 0.6 mm thin layer of hyaline cartilage between an intervertebral disc (IVD) and a vertebral body (VB). A calcification or any mechanical damage of CEP can cause restrictions of nutrition and metabolic waste flow inward and outward from IVD, respectively. Degenerative processes influence mechanical properties of the tissue. Due to very small thickness of CEP, instrumental nanoindentation seems to be suitable method for this task. This paper presents a study of time dependent viscoelastic properties of native porcine CEP using nanoscale dynamic mechanical analysis in the range of frequency from 5 Hz to 215 Hz. The storage moduli were obtained in the range from 11.78 MPa to 17.11 MPa. The loss moduli were obtained in the range from 2.96 MPa to 5.32 MPa.
Osteoarthritisis a highly prevalent musculoskeletal disorder characterized by degradation of cartilage and synovial fluid (SF). Platelet derivatives as platelet-rich plasma (PRP) and platelet lysate have great potential in the treatment of osteoarthritis because they contain biologically active substances including growth factors (GFs). Rapid release of GFs and their short biological half-life are factors that can limit the therapeutic impact of PRP therapy. Herein, the first work that describes hydrogels based on polyaldehyde derivative of hyaluronic acid (HA-OX) as carriers of platelet derivatives for in situ applications is presented, which can be a possible solution to the problem. HA-OX hydrogels containing 50% (w/w) of PRP or platelet lysate can be injected using a syringe due to low viscosity(<10 Pa s) and injection force (<20 N), and reach elastic modulus up to 2000 Pa. Insulin-like GF-1 and Platelet-derived GF-AB release from HA-OX hydrogels (mesh size 297-406 nm) by Fickian and non-Fickian diffusion respectively. The released PRP GFs maintain their ability to induce cell proliferation (87%-92%). Based on the obtained results, the unique concept of a new material that can restore viscoelastic properties of SF and at the same time gradually deliver GFs from platelet derivatives is designed.
Krzysztofik, M, Spieszny, M, Trybulski, R, Wilk, M, Pisz, A, Kolinger, D, Filip-Stachnik, A, and Stastny, P. Acute effects of isometric conditioning activity on the viscoelastic properties of muscles and sprint and jumping performance in handball players. J Strength Cond Res 37(7): 1486-1494, 2023-The effects of conditioning activity (CA) on muscle stiffness are currently unknown, suggesting that maximum CA effort can increase or decrease the stiffness of involved muscle groups. Therefore, this study aimed to investigate the effect of maximal isometric half-squats on the viscoelastic properties of muscles and postactivation performance enhancement (PAPE) in sprints and jumps. Twelve handball players underwent a standard warm-up and baseline assessment of muscle stiffness and tone of vastus lateralis and gastrocnemius medialis muscle, followed by 20-m sprint with intermediate measures at 5 and 10 m and countermovement jump. The PAPE was assessed by repeating the tests (at 4th, 8th, and 12th minute post-CA) after a CA protocol consisting of 3 sets of 3-second maximal isometric half-squats (EXP) or a control condition (CTRL) without any CA. The vastus lateralis stiffness in the 4th and 12th minute and muscle tone in the 4th minute post-CA significantly decreased compared with baseline ( p = 0.041, ES = 0.57; p = 0.013, ES = 0.52; p = 0.004, ES = 0.81, respectively) in the EXP condition. The 20-m sprint time significantly decreased at all post-CA time points compared with the baseline for the EXP condition ( p < 0.033) and the after values in the CTRL condition ( p < 0.036). In comparison to baseline, the 10-m sprint time decreased in the eighth minute post-CA ( p = 0.021; ES = 0.82) in the EXP condition. Moreover, it was significantly lower at the 8th and 12th minute post-CA ( p = 0.038; ES = 0.71 and p = 0.005; ES = 1.26) compared with that time points in the CTRL condition. The maximal isometric half-squats effectively improved sprint performance and significantly decreased vastus lateralis tone and stiffness. These findings offer new insights into the assessment of viscoelastic properties for evaluating the fatigue or potentiation state, which requires further investigation.
- MeSH
- čtyřhlavý sval stehenní MeSH
- kosterní svaly fyziologie MeSH
- lidé MeSH
- postura těla MeSH
- sportovní výkon * fyziologie MeSH
- svalová síla fyziologie MeSH
- Check Tag
- lidé MeSH
- Publikační typ
- časopisecké články MeSH
