Adhesion Model Research Articles

Efficacy of Naldemedine on Intestinal Hypomotility and Adhesions in Rodent Models of Postoperative Ileus.

Postoperative ileus (POI) often decreases patients' QOL because of prolonged hospitalization and readmission. Alvimopan, a peripheral μ-opioid receptor antagonist, is currently the only therapeutic drug for POI. The aim of this study was to examine the efficacy of naldemedine (a peripheral μ-opioid receptor antagonist with a non-competitive pharmacological profile different from that of alvimopan) on postoperative intestinal hypomotility and adhesion in rodent models, and compare it with the effects of alvimopan. Oral administration of naldemedine (0.3 mg/kg) and alvimopan (3 mg/kg) significantly inhibited the decrease in intestinal motility induced by mechanical irritation in mice (p < 0.01, for both). Naldemedine (1 mg/kg) significantly shortened the adhesion length in chemical-induced postoperative adhesion model rats (p < 0.05). Alvimopan (3 mg/kg) also significantly reduced the adhesion ratio (p < 0.01). These findings suggest that naldemedine is effective for postoperative intestinal hypomotility and adhesions in rodents (i.e., as for alvimopan). Thus, naldemedine may be a useful option for the treatment of POI.

Development of wet adhesion of honeybee arolium incorporated polygonal structure with three-phase composite interfaces

Inspired by the dynamic wet adhesive systems in nature, various artificial adhesive surfaces have been developed but still face different challenges. Crucially, the theoretical mechanics of wet adhesives has never been sufficiently revealed. Here, we develop a novel adhesive mechanism for governing wet adhesion and investigate the biological models of honeybee arolium for reproducing the natural wet adhesive systems. Micro-nano structures of honeybee arolium and arolium-prints were observed by Cryogenic scanning electron microscopy (Cryo-SEM), and the air pockets were found in the contact interface notably. Subsequently, the adhesive models with a three-phase composite interface (including air pockets, liquid secretion, and hexagonal frames of arolium), were formed to analyze the wet adhesion of honeybee arolium. The results of theoretical calculations and experiments indicated an enhanced adhesive mechanism of the honeybee by liquid self-sucking effects and air-embolism effects. Under these effects, normal and shear adhesion can be adjusted by controlling the proportion of liquid secretion and air pockets in the contact zone. Notably, the air-embolism effects contribute to the optimal coupling of smaller normal adhesion with greater shear adhesion, which is beneficial for the high stride frequency of honeybees. These works can provide a fresh perspective on the development of bio-inspired wet adhesive surfaces.

PLLA-COI multilayer nanofiber membrane for anti-adhesion of the Achilles tendon

Peritendinous Adhesion is a complication after surgery for Achilles tendon injury. This complication can be treated with surgical stents. Anti-adhesion membrane is an effective scaffold material to prevent adhesion. However, currently available PLA anti-adhesion membranes have the problems of poor anti-adhesion performance and low healing effect on the Achilles tendon. In this study, combined the advantages of L-polylactic acid (PLLA) hydrophobicity and Collagen type I (COI) hydrophilicity, a PLLA-COI multilayer nanofiber membrane composed of a multilayer structure was prepared by solution electrospinning and characterized its morphology, physical, mechanical, and in vitro properties. The membrane has a structure characteristic of gradually decreasing fiber diameter, increasing porosity and increasing hydrophilicity from the outer to the inner layer. The cell experiment results show that the PLLA-COI multilayer nanofiber membrane has good cell compatibility. We also carried out in vivo research with the rabbit Achilles tendon adhesion model. The results indicate that the membrane has an excellent anti-adhesion effect and strong hydrophilicity, effectively promoting Achilles tendon injury recovery and preventing adhesion. In addition, this membrane does not require sutures for surgery, effectively reducing the complexity of use, with great potential in preventing peritendinous adhesion.

Anti-adhesive effect of naturally obtained dicalcium phosphate dihydrate nanoparticles in the rat uterine wound model.

In this study, we aimed to compare the anti-adhesive effects of contractubex and dicalcium phosphate dihydrate (DCPD) particles in rats treated with the uterine horn adhesion model. Newly adult, 60 Wistar albino rats were used as experimental animals. The modified rat uterine horn adhesion model was used to induce intra-abdominal adhesion. Tumor necrosis factor (TNF)-α, interleukin (IL)-1, vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β1 were studied for biochemical and immunohistochemical examination. TNF-α decreased in each group, while it decreased more in G2 and G3 than in G1. IL-1β decreased in each group, while it decreased the most in G3. TGF-β1 and VEGF localization was less in the G2 compared to G1, the least TGF-β1 and VEGF immunolocalization was detected in the G3 and G4. For both antibodies, the least localization among all groups belonged to G3. From day 7 to day 21, the highest TGF-β1 immunolocalization was observed in G1, lesser localization in G2 and lowest in G3. DCPD nanoparticles show promise as a clinical antiadhesive agent and should be further evaluated in experimental animal models and human trials.

Fewer polymer chains but higher adhesion: How gradient-stiffness hydrogel layers mediate adhesion through network stretch.

The presence of gradient softer outer layers, commonly observed in biological systems (such as cartilage and ocular tissues), as well as synthetic crosslinked hydrogels, profoundly influences their interactions with opposing surfaces. Our prior research demonstrated that gradient-stiffness hydrogel layers, characterized by increasing elasticity with depth, control contact mechanics, particularly in proximity to the layer thickness. We postulate that the distribution of polymers within these gradient layers imparts extraordinary stretch and adhesion characteristics due to network adaptability and stress-induced reorganization. To investigate this phenomenon, we utilized Atomic Force Microscopy nanoindentation to assess the depth-dependent adhesion behavior of polyacrylamide hydrogels with varying gradient layer thicknesses. Two gradient layer thicknesses were achieved by employing different molding materials: glass and polyoxymethylene (POM). Glass-molded hydrogels exhibited a thinner gradient layer alongside a stiffer bulk layer compared to their POM-molded counterparts. In indentation experiments, the POM-molded hydrogel had larger adhesion compared to glass-molded hydrogel. We find that indenting within the gradient layer engenders increased load-unload hysteresis due to heightened fluid transport in the sparse outer polymer network. Consequently, this led to augmented adhesion and work of separation at shallow depths. We suggest that the prominent stretching capability of the sparse outer polymer network during probe retraction contributes to enhanced adhesion. The Maugis-Dugdale adhesive model only fits well to indentations on the thin layer or indentations which engage significantly with the bulk. These results facilitate a comprehensive characterization of adhesion mechanics in gradient-stiffness hydrogels, which could foster their application across emerging contexts in health science and environmental domains.

Modeling adhesion and aerodynamic removal of particles and spores from substrates

During launch operations, mission critical hardware and materials are encapsulated in a fairing prior to deployment. Depressurization can induce particle removal from fairing walls and redistribute them onto the payload. This poses serious challenges for current and future missions. This includes organic, inorganic, and biological material which can contaminate the surrounding environment. Given the risks associated with these events, efforts have been made to perform predictive simulations of particle contamination and redistribution. This work outlines the modeling efforts related to adhesion and aerodynamic removal of particles for prediction of redistribution in fairing environments. Physics-based models for adhesion and removal mechanisms are discussed. This includes the application of existing particle and spore adhesion models. Validation is performed for simplified canonical flow configurations. Future work regarding model improvements and extensions to large scale simulations is also discussed.

Injectable nanoengineered adhesive hydrogel for treating enterocutaneous fistulas

Enterocutaneous fistula (ECF) is a severe medical condition where an abnormal connection forms between the gastrointestinal tract and skin. ECFs are, in most cases, a result of surgical complications such as missed enterotomies or anastomotic leaks. The constant leakage of enteric and fecal contents from the fistula site leads to skin breakdown and increases the risk of infection. Despite advances in surgical techniques and postoperative management, ECF accounts for significant mortality rates, estimated between 15 and 20 %, and causes debilitating morbidity. Therefore, there is a critical need for a simple and effective method to seal and heal ECFs. Injectable hydrogels with combined properties of robust mechanical properties and cell infiltration/proliferation have the potential to block and heal ECFs. Herein, we report the development of an injectable nanoengineered adhesive hydrogel (INAH) composed of a synthetic nanosilicate (Laponite®) and a gelatin-dopamine conjugate for treating ECFs. The hydrogel undergoes fast cross-linking using a co-injection method, resulting in a matrix with improved mechanical and adhesive properties. INAH demonstrates appreciable blood clotting abilities and is cytocompatible with fibroblasts. The adhesive properties of the hydrogel are demonstrated in ex vivo adhesion models with skin and arteries, where the volume stability in the hydrated internal environment facilitates maintaining strong adhesion. In vivo assessments reveal that the INAH is biocompatible, supporting cell infiltration and extracellular matrix deposition while not forming fibrotic tissue. These findings suggest that this INAH holds promising translational potential for sealing and healing ECFs. Statement of significanceThis research manuscript presents a groundbreaking INAH for treating ECFs. The INAH, composed of a synthetic nanosilicate and gelatin-dopamine conjugate, offers versatile implications in tissue regeneration and localized drug delivery. Acting as a scaffold, the shear-thinning hydrogel enables easy injection, forming a stable structure that supports tissue regeneration and integrates with surrounding tissues. By incorporating bioactive cues, it guides cell behavior and promotes functional tissue regeneration. The INAH also demonstrates potential for localized drug delivery, releasing therapeutic agents over time to enhance efficacy and minimize side effects. This research showcases INAH as a promising solution for ECFs, with applications in tissue engineering and regenerative medicine, marking a significant advancement in the field.

Is hydrophobic coating on glass equally efficient in reducing % soiling loss of solar PVs in clean and polluted environments?

Hydrophobic-coated glass (CS) on PV surfaces is known to reduce particulate matter (PM) accumulation. However, there is no comparative study on the % reduction in soiling loss (% RSL) on CS with respect to uncoated glass (UCS) for clean and polluted environments (higher atmospheric PM). The present field study (∼210 km2 in Gujarat, Western India) focuses on the evaluation of particle-size distribution of PM on CS and UCS, quantification of size-resolved soiling due to PM accumulation on CS and UCS, and comparison of % RSL of CS in cleaner and polluted environments. The findings show that 3 to 10 µm particles contribute to ∼21 % and ∼12 % of the total mass accumulated on CS and UCS, respectively. The observations are also validated using the theoretical adhesion model and critical rebounding velocity. Moreover, this particle-size fraction contributes to ∼50 % of the total soiling loss for CS against only ∼27 % soiling loss for UCS. Therefore, CS surfaces under polluted environments are expected to have a higher % of finer particle-size fraction in accumulated PM, which contributes significantly to the total soiling loss of CS and reduces the difference in % soiling loss between CS and UCS. Although CS reduces PM accumulation in both clean and polluted regions, the % RSL using CS is comparatively less in a polluted environment. The observations from the present study provide greater insight into the soiling aspect of solar PVs and have significant economic implications in deploying PV surfaces with hydrophobic coated glass.

The effect of natural surfactants on the development of postoperative intraabdominal adhesion.

The development of postoperative adhesion after abdominal surgery is sometimes a severe problem. Our study investigates the effectiveness of exogenous surfactant application in preventing adhesion development in the experimental adhesion model. This randomized-controlled interventional study was carried out in the animal laboratory of Kahramanmaraş Sütçü İmam University between March 1 and March 31, 2020. An experimental intra-abdominal adhesion model was established in 24 adult female rats by cecal abrasion. Rats were randomly divided into four groups. Groups I, II, and III were taken intraperitoneally as beractant, poractant, and calfactant applied groups, respectively. Group IV was the control group. Relaparotomy was performed in all groups on the 15th postoperative day, and intra-abdominal adhesions were scored macroscopically according to the Canbaz scoring system. In addition, the cecal regions were evaluated microscopically and scored according to the Zühlke microscopic classification system. The scores of the groups were compared statistically. The Zühlke adhesion development score was significantly lower in the exogenous surfactant applied groups. In addition, when the surfactant-applied groups were compared among themselves, it was seen that the adhesion score in the beractant group was significantly better than the other surfactant types (p < 0.01). Our study results showed that prophylactic intraperitoneal surfactant application significantly reduced postoperative adhesion development, particularly beractant.

Compression properties of bimodal powders with different plasticities in the elastoplastic powder compression process: A numerical analysis

Powder compression has been utilized in various industries, including pharmaceuticals, foods, metals, and batteries. Although powder properties affect the compact structure, these effects remain unclear. In this study, we used the discrete element method to investigate the effects of particle cohesiveness and plasticity on the compression of bimodal powders. The Edinburgh elastoplastic adhesion model, which considers particle cohesiveness and plastic deformation, was applied as the contact model. The particle plasticity λp was varied from 0 to 0.7. The macroscopic and microscopic properties of the powder compression were investigated. The void fractions of two-component powder mixtures with different plasticities were evaluated. In contrast to that for the elastic model, the void fraction at Vf = 0.5 was smaller than that at Vf = 0.3 for the high plastic condition (λp = 0.7). In addition, as the number of fine particles increased, the largest contact type changed in the order of coarse–coarse, coarse–fine, and fine–fine. The plasticity of the particles enhanced the effects of fine particle addition. This study suggests that it is essential to determine the optimal addition ratio of fine particles based on the plastic deformability of the material.

On shear adhesion of adhesive fibrils

Natural fibrillar adhesives, widely recognized for their strong and reversible adhesion, have inspired the development of numerous synthetic adhesive systems applied in diverse fields. These biological and bioinspired adhesive fibrils exhibit a wide range of aspect ratios spanning four orders of magnitude. Accurate prediction of their adhesion performance is crucial for their practical applications. Prior investigations have primarily focused on adhesion under normal loading, although shear loading is also commonly encountered in various scenarios. To date, only a few shear adhesion models exist, and they are limited to either high or low aspect ratios. Rigorous mechanics analysis of adhesive fibrils’ shear adhesion strength across a wide range of aspect ratios is lacking. In this study, we developed a mechanics model based on the compliance method for evaluating the energy-controlled interfacial failure of the adhesive fibrils, estimated the shear adhesion strength of a lap shear system across a wide range of fibrillar aspect ratios, and carried out the finite element analysis (FEA) to validate the model prediction. Our model reveals that, depending on the fibrillar aspect ratio, the adhesive fibril exhibits three distinct deformation regimes: thin film shearing, thick block shearing, and slender beam bending. The important parameters governing the shear adhesion of the lap shear system are the aspect ratio of fibrils, elastic moduli of the fibrils and substrates, while the Poisson's ratio of fibrils has no noticeable effect. Our model captures the shear compliance across a wide aspect ratio range from 10−4 to 102 accurately and is in excellent agreement with the FEA results. Based on this compliance solution, a rigorous scaling law for shear adhesion strength is derived, which can predict the energy-controlled adhesion regime as well as the theoretical strength-limited regime, as the aspect ratio decreases. These results reveal the underlying mechanisms governing the shear adhesion strength of fibrillar adhesives and provide guidance for future design and optimization of fibrillar adhesives.

THE ROLE OF ANTICOAGULANT, THROMBOLYTIC, AND FIBRINOLYTIC ACTIVITIES IN THE PREVENTION OF PERITONEAL ADHESION

Peritoneal adhesion occurs as a result of surgery, peritoneal injury, peritonitis, hypoxia, and ischemia. Surgical trauma causes many pathophysiological processes which include inflammation, oxidation, coagulation, fibrinolysis, cell proliferation, and apoptosis. After intra-abdominal operations, the adhesion tissue may occur on the peritoneal surface due to low fibrinolytic activity. This may result in permanent excessive adhesion tissue bands instead of properly formed fibrin structures. Therefore, anticoagulant, thrombolytic, and fibrinolytic activities have a key role in preventing peritoneal adhesion. Indeed, several studies have been conducted to find out new and effective agents against intra-abdominal adhesion. Thus, revealing the causes, development processes, and investigation techniques are highly important for designing and conducting such scientific studies. In this context, this study aims to summarize the pathophysiological processes of above-mentioned activities and to emphasize their importance in the peritoneal adhesion model as well as to explain the evaluation methods, particularly in terms of the investigation of natural products.

Model for an elastic-plastic spherical contact with the DMT adhesion

This paper studied the elastic-plastic spherical contact with the DMT adhesion, and presented an improved smooth formula for the local separation outside the elastic-plastic contact area on the KE empirical formula. The elastic-plastic local separation was equal to the elastic local separation with the same contact area and a equivalent elastic contact displacement. When the contact entered the elastic deformation regime, due to zero residual plastic contact displacement, the present formula for the elastic-plastic local separation could reduce to that for the elastic local separation naturally. Utilizing the present formula for the local separation, a unified adhesion model suitable for between the elastic and elastic-plastic spherical contact with the DMT adhesion was presented. In comparison with the KE adhesion model, the present adhesion model had higher fitting accuracy and could approach the Bradley’s value as the contact displacement approached zero well, which was a good approximation to the complete integration calculation. The present adhesion model could be used for the study of the elastic and elastic-plastic spherical contact with adhesion.

Metal-soil interface adhesion in clay clogging during shield tunneling: Theoretical model and experimental validation

Clogging is a major geohazards risk in mechanized tunnelling through cohesive soils. Clay clogging results from the high adhesion between the clay and metal. Based on the water film theory and Reynolds fluid equation, the interfacial adhesion between metal and soil is simplified in this study as viscous hydrodynamic behavior between planes. Considering the influence of capillary force and the viscous force of water film at the interface between metal and soil, a theoretical calculation model of interfacial adhesion between metal and soil is established. The influence of water film thickness and separation rate on the interfacial adhesion between metal and soil is qualitatively analyzed. Then, the adhesion stress between the clay and the metal surface was tested with a pullout test and the influence of moisture content, pullout rates and types of clay minerals on the adhesion stress was analyzed. Finally, the calculation model of adhesion force was compared with the experimental results. The calculation model of soil adhesion stress established in this paper can quantitatively describe the relationship between soil adhesion force and moisture content and can also qualitatively reveal the influence mechanism of soil moisture content on adhesion stress.

Modelling of damage and failure within polymeric adhesives

AbstractWithin this contribution, we propose a fully thermo‐mechanical coupled isotropic damage model for polymeric adhesives under finite strains. This model is based on the multiplicative decomposition of the deformation gradient into mechanical and thermal parts. We consider rate‐dependent damage behaviour (e.g. creep damage) of the material by applying a Perzyna‐type ansatz for the damage evolution equations. To overcome the pronounced mesh dependencies which would result from the usage of a local damage model, we make use of a gradient‐extended damage formulation. Besides the main aspects of model, we show the thermodynamically consistent derivation of constitutive quantities as well as the numerical treatment of the governing equations. Finally, we show selected numerical examples to demonstrate the capabilities of the model.

Switchable shape memory polymer bio-inspired adhesive and its application for unmanned aerial vehicle landing

Controlled and switchable adhesion is commonly observed in biological systems. In recent years, many scholars have focused on making switchable bio-inspired adhesives. However, making a bio-inspired adhesive with high adhesion performance and excellent dynamic switching properties is still a challenge. A Shape Memory Polymer Bio-inspired Adhesive (SMPBA) was successfully developed, well realizing high adhesion (about 337 kPa), relatively low preload (about 90 kPa), high adhesion-to-preload ratio (about 3.74), high switching ratio (about 6.74), and easy detachment, which are attributed to the controlled modulus and contact area by regulating temperature and the Shape Memory Effect (SME). Furthermore, SMPBA exhibits adhesion strength of 80–337 kPa on various surfaces (silicon, iron, and aluminum) with different roughness (Ra = 0.021–10.280) because of the conformal contact, reflecting outstanding surface adaptability. The finite element analysis verifies the bending ability under different temperatures, while the adhesion model analyzes the influence of preload on contact area and adhesion. Furthermore, an Unmanned Aerial Vehicle (UAV) landing device with SMPBA was designed and manufactured to achieve UAV landing on and detaching from various surfaces. This study provides a novel switchable bio-inspired adhesive and UAV landing method.

Analysis of abdominal adhesion using the ileostomy model.

Abdominal adhesion occurs commonly in clinical practice, causing unfavorable symptoms and readmission. The ileostomy operation is a common surgical procedure and we utilized this model to evaluate abdominal adhesion. Adhesion grade score was calculated in 35 patients (Cohort 1) and subjected to correlation and receiver operating characteristic analysis. Then 98 consecutive patients (Cohort 2) who underwent ileostomy and ileostomy closure were included into a retrospective study. Logistic regression analysis was performed, and the risk of small bowel obstruction was also assessed. The time of ileostomy closure correlated with adhesion grade score in Cohort 1, justifying its use as an indicator of abdominal adhesion. All patients in Cohort 2 were then divided into the high- and low-adhesion group. A multi-variable logistic regression analysis indicated that type of surgery and peritoneum suture during ileostomy were significant factors affecting the risk of abdominal adhesion. Abdominal adhesion had the trend to prolong the length of stay postoperatively without increasing the risk of bowel obstruction. Nine patients suffered bowel obstruction, and age older than 65 significantly increased the risk. We proposed the ileostomy procedure to be a model of abdominal adhesion, and the operative time of ileostomy closure could be used as an alternative of adhesion score. Type of surgery and peritoneum suture may be risk factors of abdominal adhesion. Older age increased the risk of small bowel obstruction after ileostomy surgery.

Quercetin inhibits mesothelial-mesenchymal transition and alleviates postoperative peritoneal adhesions by blocking the TGF-β1/PI3K/AKT pathway

Ethnopharmacological relevanceCarthami flos is a dried flower of the Asteraceae plant Carthamus tinctorius (L.). Danhong injection, composed of Carthami flos and Danshen can prevent the formation of postoperative peritoneal adhesions. Quercetin (QUE), an active compound of Carthami flos, has also been proved to prevent postoperative abdominal and uterine cavity adhesions. However, whether QUE is the key component in Carthami flos and the mechanism in preventing postoperative peritoneal adhesions has not been studied. Aim of the studyTo predict whether QUE is the key molecule in Carthami flos and explore the effect and mechanism of QUE in preventing postoperative peritoneal adhesions. Materials and methodsDrug composition and target analysis was used to predict the key component in Carthami flos. The method of cecum-sidewall abrasion was used to establish adhesion models, and the antiadhesion effect of QUE was evaluated with the adhesion scoring system. Network pharmacology was used to predict the targets and potential mechanism of QUE in preventing adhesion. The mechanism was further verified by immunofluorescence, Western blot, wound healing experiment, and molecular docking. ResultsQuercetin was predicted to be the key to preventing postoperative peritoneal adhesions in Carthami flos. Animal experiments revealed that QUE effectively ameliorated adhesions and reduced the expression of mesothelial-mesenchymal transition (MMT) related markers and TGF-β1. Moreover, the TGF-β1/PI3K/AKT pathway was predicted via protein-protein interaction and Kyoto encyclopedia of Genes and Genomes enrichment analysis to play a crucial part in preventing adhesion by QUE. Furthermore, in vitro experiments and molecular docking demonstrated that QUE could block the TGF-β1/PI3K/AKT pathway through forming a stable combination with TβR-II, thereby inhibiting MMT and ameliorating peritoneal adhesion. ConclusionsQUE can not only reduce postoperative TGF-β1 but also block the TGF-β1/PI3K/AKT pathway to inhibit MMT of mesothelial cells, and finally alleviate postoperative peritoneal adhesions. These findings may provide insights towards development of a safe and effective anti-adhesive drug for prevention of postoperative peritoneal adhesions.

Development and verification of adhesion models for track shoes operating on clay soils

Development and verification of adhesion models for track shoes operating on clay soils

Adhesion in soft contacts is minimum beyond a critical shear displacement

The most direct measurement of adhesion is the pull-off force, i.e. the tensile force necessary to separate two solids in contact. For a given interface, it depends on various experimental parameters, including separation speed, contact age and maximum loading force. Here, using smooth contacts between elastomer spheres and rigid plates, we show that the pull-off force also varies if the contact is sheared prior to separation. For shear displacements below a critical value about 10% of that necessary to yield gross sliding, the pull-off force steadily decreases as shear increases. For larger shear, the pull-off force remains constant, at a residual value 10%–15% of its initial value. Combining force measurements and in situ imaging, we show how the unloading path leading to contact separation is modified by the initial shear. In particular, we find that the residual pull-off force prevails if the contact reaches full sliding during unloading. Based on those observations, a first modeling attempt of the critical shear displacement is proposed, involving a competition between jump instability and transition to sliding. Overall, those results offer new insights into the interplay between adhesion and friction, provide new constraints on adhesion measurements and challenge existing adhesive models. They will be useful wherever soft contacts undergo both normal and shear stresses, including tire grip, soft robotics, haptics and animal locomotion.