Detachment Stress Research Articles

Bio-inspired chitosan/polyvinyl alcohol/tannic acid hydrogels as plant grafting wood adhesives

Recently, there has been growing interest in plant-inspired materials for various biological, medical, and industrial applications. Notably, tannic acid-based materials exhibit remarkable adhesive properties and can be used in a variety of applications, particularly biomedical applications. In addition, mixtures composed of tannic acid and polymers (e.g., polyvinyl alcohol) exhibit excellent adhesion to various substrates. In this study, we developed gallol-containing chitosan (G-CS), polyvinyl alcohol (PVA), and tannic acid (TA) composite (G-CPT) hydrogels as wood adhesive materials. G-CPT hydrogels were immediately formed by mixing the G-CS/PVA solution with the TA solution. Rheological analysis revealed an increase in the elastic modulus (G′) with the addition of small amounts of G-CS. In addition, the detachment stress of wood sticks attached using G-CPT hydrogels was 142.2 ± 7.2 MPa, which was substantially higher than that of G-CS (5.3 ± 1.4 kPa), PVA (2.2 ± 0.2 kPa), TA (0.4 ± 0.1 kPa), and PVA/TA hydrogels (106.5 ± 2.5 MPa). Furthermore, G-CPT hydrogels can be used as wood adhesives for scion grafting into the rootstock of English ivy. These findings highlight the importance of G-CPT hydrogels as eco-friendly wood adhesives with enormous potential for various industrial and agricultural applications.

From Field to Pharmacy: Isolation, Characterization and Tableting Behaviour of Microcrystalline Cellulose from Wheat and Corn Harvest Residues.

A lack of strategies for the utilization of harvest residues (HRs) has led to serious environmental problems due to an accumulation of these residues or their burning in the field. In this study, wheat and corn HRs were used as feedstock for the production of microcrystalline cellulose (MCC) by treatment with 2-8% sodium hydroxide, 10% hydrogen peroxide and further hydrolysis with 1-2 M hydrochloric acid. The changes in the FT-IR spectra and PXRD diffractograms after chemical treatment confirmed the removal of most of the lignin, hemicellulose and amorphous fraction of cellulose. A higher degree of crystallinity was observed for MCC obtained from corn HRs, which was attributed to a more efficient removal of lignin and hemicellulose by a higher sodium hydroxide concentration, which facilitates the dissolution of amorphous cellulose during acid hydrolysis. MCC obtained from HRs exhibited lower bulk density and poorer flow properties but similar or better tableting properties compared to commercial MCC (CeolusTM PH101). The lower ejection and detachment stress suggests that MCC isolated from HRs requires less lubricant compared to commercial MCC. This study showed that MCC isolated from wheat and corn HRs exhibits comparable tableting behaviour like commercial sample, further supporting this type of agricultural waste utilization.

Characterizing thrombus adhesion strength on common cardiovascular device materials.

Thrombus formation in blood-contacting medical devices is a major concern in the medical device industry, limiting the clinical efficacy of these devices. Further, a locally formed clot within the device has the potential to detach from the surface, posing a risk of embolization. Clot embolization from blood-contacting cardiovascular devices can result in serious complications like acute ischemic stroke and myocardial infarction. Therefore, clot embolization associated with device-induced thrombosis can be life-threatening and requires an enhanced fundamental understanding of embolization characteristics to come up with advanced intervention strategies. Therefore, this work aims to investigate the adhesive characteristics of blood clots on common biocompatible materials used in various cardiovascular devices. This study focuses on characterizing the adhesion strength of blood clots on materials such as polytetrafluoroethylene (PTFE), polyurethane (PU), polyether ether ketone (PEEK), nitinol, and titanium, frequently used in medical devices. In addition, the effect of incubation time on clot adhesion is explored. Results from this work demonstrated strongest clot adhesion to titanium with 3h of incubation resulting in 1.06 ± 0.20kPa detachment stresses. The clot adhesion strength on titanium was 51.5% higher than PEEK, 35.9% higher than PTFE, 63.1% higher than PU, and 35.4% higher than nitinol. Further, adhesion strength increases with incubation time for all materials. The percentage increase in detachment stress over incubation time (ranging from 30min to 3h) for polymers ranged from at least 108.75% (PEEK), 140.74% (PU), to 151.61% (PTFE). Whereas, for metallic surfaces, the percentage rise ranged from 70.21% (nitinol) to 89.28% (titanium). Confocal fluorescence imaging of clot remnants on the material surfaces revealed a well-bounded platelet-fibrin network at the residual region, representing a comparatively higher adhesive region than the non-residual zone of the surface.

Influence of spike anchors in the bond behaviour of FRCM systems applied on concave masonry substrates

One of the methods that can be used for strengthening masonry arch structures is through the use of composite systems bonded to the external surfaces, preferably to the intrados, such as textile reinforced mortar systems (FRCM, TRM, SRG etc). The application of such systems to the intrados allows the ultimate load to be increased while keeping the structure in service. The load increment depends on the performance of the bond between the matrix and the masonry substrate and between the matrix and the fabric, and also the radial detachment stresses (normal for the strengthening system) that are generated when applying this technology to concave surfaces must also be taken into account, as they have a negative effect on the load transfer mechanism. Spike anchors are generally used to reduce the negative effect of curvature in order to postpone the debonding process of the strengthening system. This paper presents the results obtained from a direct shear test campaign on curved masonry specimens strengthened with a fiber-reinforced cement-based matrix (FRCM) with pozzolanic reaction and a carbon fiber fabric. In particular, the effects of spike anchors on the load transfer mechanism between FRCM and the masonry substrate are shown. The use of such spike anchors produced, on average, a higher maximum ultimate force than specimens without spike anchors.

Enhancing Flow Properties and Preventing Sticking and Picking in Tablet Formulations: Exploring the Efficacy of StarTab® as a Multifunctional Additive

This study investigates the flow and compression behaviour of four excipients (StarTab®, MCC, Mannitol, Lactose) when combined with caffeine as a model drug for direct compression. Notably, pure caffeine particles demonstrate high adhesion to punch and die walls. However, the incorporation of StarTab®led to improved flow of the pre-blend, along with reductions in detachment stress (DS) and ejection stress (ES) during tabletting. Contrarily, blending caffeine with MCC, Mannitol, and Lactose did not result in considerable improvements in flow properties and also did not address sticking and picking issues. The potential of StarTab® in enhancing flow properties and addressing sticking issues in pharmaceutical applications is highlighted. These findings contribute to optimizing formulations for efficient tablet production.

Development of a PAT platform for the prediction of granule tableting properties

In this work, the feasibility of implementing a process analytical technology (PAT) platform consisting of Near Infrared Spectroscopy (NIR) and particle size distribution (PSD) analysis was evaluated for the prediction of granule downstream processability. A Design of Experiments-based calibration set was prepared using a fluid bed melt granulation process by varying the binder content, granulation time, and granulation temperature. The granule samples were characterized using PAT tools and a compaction simulator in the 100-500kg load range. Comparing the systematic variability in NIR and PSD data, their complementarity was demonstrated by identifying joint and unique sources of variation. These particularities of the data explained some differences in the performance of individual models. Regarding the fusion of data sources, the input data structure for partial least squares (PLS) based models did not significantly impact the predictive performance, as the root mean squared error of prediction (RMSEP) values were similar. Comparing PLS and artificial neural network (ANN) models, it was observed that the ANNs systematically provided superior model performance. For example, the best tensile strength, ejection stress, and detachment stress prediction with ANN resulted in an RMSEP of 0.119, 0.256, and 0.293 as opposed to the 0.180, 0.395, and 0.430 RMSEPs of the PLS models, respectively. Finally, the robustness of the developed models was assessed.

How APTMS Acts as a Bridge to Enhance the Compatibility of the Interface between the Hydrophilic Poly(vinyl alcohol) Film and the Hydrophobic Stearic Acid Coating.

The hydrophobic modification of poly(vinyl alcohol) (PVA) film as a biodegradable packaging material has received significant attention in recent research. Despite the use of stearic acid (SA) as a coating for the PVA film, a challenge persists due to the poor compatibility between SA and PVA. This study addressed the aforementioned issue by utilizing (3-aminopropyl)trimethoxysilane (APTMS) as a bridging agent to establish a connection between the hydrophilic PVA film and the hydrophobic SA coating through hydrogen bonding and chemical reactions. First, SEM and EDS analyses confirmed the enhanced interfacial compatibility between the SA coating and the PVA film. Subsequently, the results from 1H NMR, FTIR, and XPS experiments presented evidence of hydrogen bonding and chemical reactions among APTMS, SA, and the PVA film. Interestingly, the PVA-APTMS-SA film demonstrated a contact angle of 120.77°, a water absorption of 7.81%, and a water vapor transmission rate of 8.69 g/m2/h. Furthermore, such a composite film displayed exceptional adhesion performance, requiring detachment stresses of 9.86 ± 0.91 and 6.17 ± 0.75 MPa when tested on glass and marble surfaces, respectively. In conclusion, the PVA-APTMS-SA film exhibited significant potential in extending the freshness of fresh-cut apples, making it a promising eco-friendly packaging material for food preservation.

Application of Machine-Learning Algorithms for Better Understanding the Properties of Liquisolid Systems Prepared with Three Mesoporous Silica Based Carriers.

The processing of liquisolid systems (LSS), which are considered a promising approach to improving the oral bioavailability of poorly soluble drugs, has proven challenging due to the relatively high amount of liquid phase incorporated within them. The objective of this study was to apply machine-learning tools to better understand the effects of formulation factors and/or tableting process parameters on the flowability and compaction properties of LSS with silica-based mesoporous excipients as carriers. In addition, the results of the flowability testing and dynamic compaction analysis of liquisolid admixtures were used to build data sets and develop predictive multivariate models. In the regression analysis, six different algorithms were used to model the relationship between tensile strength (TS), the target variable, and eight other input variables. The AdaBoost algorithm provided the best-fit model for predicting TS (coefficient of determination = 0.94), with ejection stress (ES), compaction pressure, and carrier type being the parameters that influenced its performance the most. The same algorithm was best for classification (precision = 0.90), depending on the type of carrier used, with detachment stress, ES, and TS as variables affecting the performance of the model. Furthermore, the formulations with Neusilin® US2 were able to maintain good flowability and satisfactory values of TS despite having a higher liquid load compared to the other two carriers.

Detachment stress mediated bioenergetic switch of malignant melanoma cells into anti-Warburg phenotype.

One of the biological features of cancer cells is their aerobic glycolysis by extensive glucose fermentation to harvest energy, so called Warburg effect. Melanoma is one of the most aggressive human cancers with poor prognosis and high mortality for its high metastatic ability. During the metastatic process, the metastatic tumor cells should survive under detachment stress. However, whether the detachment stress could affect the tumor phenotype is worthy to investigate.We had established the cell model of human melanoma cells under detachment stress, which mimicked circulating melanoma. It had been demonstrated that the detachment stress altered melanoma cell activities, malignancy, and drug sensitivity. In this study, we found that adherent melanoma cells were more sensitive to glucose depletion. Gene expression profiling altered expressions of transporters associated with glucose metabolism. In addition, detachment stress reduced lactate secretion owing to the reduced MCT4 and GLUT1 expressions, the altered glycolytic and respiratory capacities, and the increased superoxide production. Detachment stress also increases the sensitivity of melanoma cells toward the blockade of electron transport chains. Investigation of the change in glucose metabolism of melanoma cells under detachment stress would be critical to provide a novel molecular mechanism to develop potential therapeutics.

Pullulan and Pluronic F-127 based in situ gel system for intranasal delivery: Development, in vitro and in vivo evaluation

The current work seeks to use Pullulan and Pluronic F-127 (PF-127), a new gel-forming material, for sildenafil citrate (SLC) intranasal delivery. The cold approach was used to develop an SLC-loaded in situ gel based on thermoreversible polymer PF-127 and mucoadhesive polymer Pullulan. In situ gel systems based on Pullulan responds intelligently to environmental stimuli like charge, pH, temperature, light, and redox. To achieve gelation at physiological temperature formulations were modified to have gelation temperatures lower than 34.1°C. Physical appearance and rheological measurements were used to calculate the temperature of gelation. With the addition of increasing quantities of Pullulan, the gelation temperatures fell (from 34.1°C for 8% w/v, 10% w/v, and 12% w/v 0.5% Pullulan). In the goat nasal mucosal membrane, Pullulan concentration increased the mucoadhesive force in terms of detachment stress. The results of drug permeation testing in vitro investigations over the goat nasal mucosa showed that utilizing an in situ gelling formulation with a Pullulan content of 0.5% or higher can greatly boost the effective penetration coefficient. The formulation was shown to be safe for the nasal mucosa after a histological investigation. Conclusively, Pullulan and PF-127 may be appropriate carriers for SLC intranasal administration.

Detachment Stress Calculation of Projection Stereolithography based on Cohesive Zone Simulation

Detachment Stress Calculation of Projection Stereolithography based on Cohesive Zone Simulation

Improving Tableting Performance of Lactose Monohydrate by Fluid-Bed Melt Granulation Co-Processing.

Co-processing is commonly used approach to improve functional characteristics of pharmaceutical excipients to become suitable for tablet production by direct compression. This study aimed to improve tableting characteristics of lactose monohydrate (LMH) by co-processing by fluid-bed melt granulation with addition of hydrophilic (PEG 4000 and poloxamer 188) and lipophilic (glyceryl palmitostearate) meltable binders. In addition to binding purpose, hydrophilic and lipophilic excipients were added to achieve self-lubricating properties of mixture. Co-processed mixtures exhibit superior flow properties compared to pure LMH and comparable or better flowability relative to commercial excipient Ludipress®. Compaction of mixtures co-processed with 20% PEG 4000 and 20% poloxamer 188 resulted in tablets with acceptable tensile strength (>2 MPa) and good lubricating properties (ejection and detachment stress values below 5 MPa) in a wide range of compression pressures. While the best lubricating properties were observed when glyceryl palmitostearate was used as meltable binder, obtained tablets failed to fulfil required mechanical characteristics. Although addition of meltable binder improves interparticle bonding, disintegration time was not prolonged compared to commercial excipient Ludipress®. Co-processed mixtures containing 20% of either PEG 4000 or poloxamer 188 showed superior tabletability and lubricant properties relative to LMH and Ludipress® and can be good candidates for tablet production by direct compression.

Mucoadhesive and Rheological Studies on the Co-Hydrogel Systems of Poly(Ethylene Glycol) Copolymers with Fluoroalkyl and Poly(Acrylic Acid)

A self-assembled co-hydrogel system with sol-gel two-phase coexistence and mucoadhesive properties was developed based on the combined properties of fluoroalkyl double-ended poly(ethylene glycol) (Rf-PEG-Rf) and poly(acrylic acid) (PAA), respectively. We have synthesized an Rf-PEG-g-PAA (where g denotes grafted) copolymer and integrated it into the Rf-PEG-Rf physically cross-linked micellar network to form a co-hydrogel system. Tensile strengths between the co-hydrogel surfaces and two different sets of mucosal surfaces were acquired. One mucosal surface was made of porcine stomach mucin Type II, while the other one is a pig small intestine. The experimental results show that the largest maximum detachment stresses (MDSs) were obtained when the Rf-PEG-g-PAA’s weight percent in the dehydrated polymer mixture is ~15%. Tensile experiments also found that MDSs are greater in acidic conditions (pH = 4–5) (123.3 g/cm2 for the artificial mucus, and 43.0 g/cm2 for pig small intestine) and basic conditions (pH = 10.6) (126.9 g/cm2, and 44.6 g.cm2, respectively) than in neutral pH (45.4 g/cm2, and 30.7 g.cm2, respectively). Results of the rheological analyses using shear strain amplitude sweep and frequency sweep reveal that the Rf-PEG-g-PAA was physically integrated into the Rf-PEG-Rf micellar network, and the co-hydrogels remain physically cross-linked in three-dimensional micellar networks with long-term physical dispersion stability. Therefore, the co-hydrogel system is promising for drug delivery applications on mucosal surfaces.

On the Effect of a Rate-Dependent Work of Adhesion in the Detachment of a Dimpled Surface

Patterned surfaces have proven to be a valuable design to enhance adhesion, increasing hysteresis and the detachment stress at pull-off. To obtain high adhesive performance, soft materials are commonly, used, which easily conform to the countersurface, such as soft polymers and elastomers. Such materials are viscoelastic; i.e., they show rate-dependent properties. Here, the detachment of two half spaces is studied, one being flat and the other having a dimple in the limit of short range adhesion and a power law rate-dependent work of adhesion, as observed by several authors. Literature results have suggested that the dimpled surface would show pressure-sensitive adhesion, showing two possible adhered states, one weak, in partial contact, and one strong when full contact is achieved. By accounting for a power law rate-dependent work of adhesion, the “weak state” may be much stronger than it was in the purely elastic case, and hence the interface may be much more tough to separate. We study the pull-off detachment stress of the dimpled surface, showing that it weakly depends on the preload, but it is strongly affected by the dimensionless unloading rate. Finally, possible implications of the presented results in the detachment of soft materials from rough substrates are discussed.

Effect of the Size of Particles on Their Adhesion in Composite Polypropylene/SiO2

The effect of particle size on the mechanical characteristics of biaxially oriented composite polypropylene/SiO2 is studied. The material is oriented in plane by squeezing two lead-tin alloy plates with the composite film being placed between them. Deformation is defined by the composition of the plates. This makes it possible to obtain the material with low degrees of orientation. The oriented composite preserves plasticity typical of the polypropylene matrix. After biaxial orientation of the unfilled PP, the yield point decreases by approximately 40% upon subsequent stretching. A reduction in the size of particles changes their adhesion behavior during stretching. Coarse particles with a size of about 20 µm separate from PP during stretching. On the contrary, nanoparticles with sizes of 200 and 500 nm do not separate even under plastic deformation of the composite. As a result, nanoparticles reinforce the thermoplastic the same way as carbon black nanoparticles reinforce rubber. The energy detachment criterion explaining an increase in the detachment stress with decreasing particle size is derived.

Dislocation creep modelling of Sanicro 25 based on microstructural evolution and particle hardening mechanism

A dislocation model for predicting creep deformation and long-term life of Sanicro 25 austenitic steel was proposed on the basis of microstructural evolution and particle hardening mechanism. This approach was integrated by four sub-models of (i) time- and strain-induced detachment stress model, (ii) Orowan strengthening model of two precipitates, (iii) void nucleation and growth model, and (iv) temperature-induced strain energy model. The validation of the proposed model was verified by the experimental data of different testing conditions of Sanicro 25. In addition, the microstructural fracture mechanism and the variation of detachment stress were discussed. The framework of the proposed model may provide a basis for evaluating the creep life of high temperature austenitic material.

Anchorage independence altered vasculogenic phenotype of melanoma cells through downregulation in aminopeptidase N /syndecan-1/integrin β4 axis.

The detachment of tumor cells from extracellular matrix and survival under anchorage-independence were recognized as the initial step of tumor metastasis. Previously we had demonstrated that anchorage-independence altered gene expressions and showed characteristics of cell invasiveness loss, enhanced chemosensitivity, and enhanced subcutaneous tumor formation. However, whether it affected histological phenotypes in tumor tissues remained unclear.Melanoma metastases were generated in nude mice using adherent or suspended melanoma cells. Examination of melanoma metastases revealed histological features of extensive vascular structures in adherent cell-derived tumors, while not seen in suspended cell-derived tumors. Quantitative proteomic analysis at adherent, suspended, and re-attached melanoma cells suggested that aminopeptidase N was potentially downregulated upon cell suspension or reattachment. Downregulation of aminopeptidase N by gene-specific shRNAs showed reduced cell invasiveness and enhanced subcutaneous tumor formation that was consistent with previous observations. Experiments by suppression or overexpression of aminopeptidase N expression demonstrated that aminopeptidase N regulated syndecan-1 and integrin β4 expression through PKCδ pathway. Histological analysis at melanoma metastases further suggested that CD31+/aminopeptidase N+/syndecan-1+/integrin β4+ phenotypes were associated with vascular structures.In summary, we suggested the expression axis of aminopeptidase N/syndecan-1/integrin β4 in melanoma cells was suppressed by detachment stress, which diminished vascular phenotypes of melanoma metastases.

High-temperature creep deformation in FeCrAl-oxide dispersion strengthened alloy cladding

The FeCrAl-oxide dispersion strengthened (ODS) alloy is the promising cladding material for the accident-tolerant fuel (ATF) of the light water reactors (LWR) to suppress the oxidation reaction with hot steam by Al2O3 formation. Ring-creep tests for FeCrAl-ODS alloy cladding were carried out at 973 K and 1273 K to evaluate the deformation mechanism at the sever accident. The temperature-compensated strain rate by Fe-diffusion coefficient versus the normalized stress by shear modulus was constructed. The dislocation detachment stress from the dispersoid was derived by considering the dislocation-dispersoid elastic interaction and the dislocation relaxation effect by climb motion. When the applied stress exceeds the dislocation detachment stress, dislocations overcome the dispersoids with the reduced values of the stress exponent, which is attributed to the dislocation climb motion. When the stress is lower than the dislocation detachment stress, large size of cavities exists at the grain boundaries. Grain boundary sliding (GBS) is dominant factor for the low strain rate creep deformation at 1273 K, where dislocation climb also plays a critical role for release of the stress concentration induced by GBS. Based on those findings, new constitutive equations for creep deformation were constructed, which is applicable to low stress, low strain rate and high temperature conditions encountered at the reactor sever accident.

Cling performance and surface area of attachment in plethodontid salamanders.

Plethodontid salamanders inhabit terrestrial, scansorial, arboreal and troglodytic habitats in which clinging and climbing allow them to access additional food and shelter as well as escape from unfavorable temperature and moisture conditions and ground-dwelling predators. Although salamanders lack claws and toe pads found in other taxa, they successfully cling to and climb on inclined, vertical and inverted substrates in nature. Maximum cling angle was tested on smooth acrylic, and the relationship between cling angle, body mass and surface area of attachment (contact area) was investigated. This study found that many salamander species can cling fully inverted using only a portion of their ventral surface area to attach. Salamanders fall into three functional groups based on mass and maximum cling angle: (1) high-performing, very small salamanders, (2) moderately high performing small and medium-sized salamanders and (3) low-performing large salamanders. They show significant differences in maximum cling angle, even between species of similar mass. In species of similar mass experiencing significantly different detachment stress (resulting from significantly different contact area), differences in morphology or behavior affect how much body surface is attached to the substrate. High performance in some species, such as Desmognathus quadramaculatus, is attributable to large contact area; low performance in a similarly sized species, Ensatina eschscholtzii, is due to behavior that negatively impacts contact area. There was no clear evidence of scaling of adhesive strength with increasing body size. Salamander maximum cling angle is the result of morphology and behavior impacting the detachment stresses experienced during clinging.

Tableting of hot-melt coated paracetamol granules: Material tableting properties and quality characteristics of the obtained tablets

Hot-melt coating (HMC) has been recognized as a promising technique in the production of solid dosage forms e.g., HMC of granules can be applied prior to compression in order to obtain modified drug release or taste masking. However, tableting properties of HMC granules have not been studied yet. In this work, we explored the influence of the lipid coating on granules tableting properties, and assessed quality attributes of the obtained tablets. Paracetamol granules, previously coated with the lipid excipient Precirol® ATO 5 using a hot-melt coating technique in modified fluidized-bed system, were evaluated in terms of work of compression, elastic recovery, tablets tensile strength, detachment stress and ejection stress. Regarding the product quality, tablets content uniformity, friability, disintegration time and drug release properties were tested. Our results demonstrated that tablets made of coated granules exhibited more pronounced elastic behaviour, and increased tensile strength in comparison to tablets made of uncoated granules, suggesting that lipid coating promotes elastic deformation and forms lipid matrix within the tablets. Additionally, low detachment and ejection stresses for tablets made of HMC granules indicated no need to add lubricant prior to tableting process. Evaluation of tablets properties revealed that tablets friability was not influenced by the presence of lipid coating on the compressed granules. However, formation of lipid matrix within the tablets made of HMC granules resulted in prolonged tablet disintegration time, and sustained drug release. Moreover, the performance of lipid matrix tablets, in terms of drug dissolution rate, was relatively insensitive to compression pressure variations in 104–173 MPa range. The obtained results indicate that tableting of HMC granules is a promising technique to obtain sustained release lipid matrix tablets of suitable pharmaceutical-technical properties.