Higher Bond Research Articles

Robust profiled carbon rovings made of multiple yarns for textile reinforcements in concrete and asphalt matrix

The load-bearing behavior and the performance of composites depends largely on the bond between the individual components. Conventional grid-like textile reinforcement structures with thin and smooth yarn structures transmit forces primarily by an adhesive bond with the surrounding matrix. A sufficient load transmission is not possible. Thick, pultruded rebars made of fiber-reinforced plastics can be profiled by subtractive (e.g. milling) or additive (e.g. wrapping) techniques in order to create a rip-like structure and increased shear bond. Yet the discontinuous fiber course results in material inefficiency. A newly developed profiling technique allows a tetrahedral profiling of the complete roving structure, yet considering its anisotropic properties. In the article, we present this approach, and the first results from single yarn tensile and pull-out tests of single, double and triple plied profiled rovings in concrete and asphalt matrix. Thus, the highest bond is achieved in the brittle concrete matrix. Plied rovings with strong tetrahedral profiles show up to 600% higher bond stress compared with rovings with circular profiles, while maintaining high tensile properties. However, splitting-induced failure of the reinforced test specimens occurs, making plied profiled rovings favorable for high concrete cover and less brittle matrixes; for example, asphalt. The reinforced asphalt specimens show at −10°C similar bond properties, but at 30°C the bond decreases by 80%. In summary, the study shows that bond properties of profiled rovings are superior to conventional circular rovings, and promise a high material efficiency for use in concrete and asphalt reinforcements.

Organohydrogel‐Based Soft SEMG Electrodes for Algorithm‐Assisted Gesture Recognition

AbstractEpidermal electronics that can monitor physiological signals such as surface electromyogram (sEMG) signals attract widespread attentions in personalized healthcare, human–machine interfaces (HMI) and virtual/augmented reality (AR/VR). However, conventional electromyographic electrodes suffer from skin discomfort, susceptibility to motion artifact interference, and short service lifetime. Here, an organohydrogel‐based sEMG electrode endows with high conductivity, low modulus and long‐term stability is developed by doping partially reduced graphene oxide (pRGO) into highly cross‐linked organohydrogel network. The as‐fabricated polyacrylamide/sodium alginate/tannic acid/partially reduced graphene oxide (PAM/SA/TA/pRGO) organohydrogel possesses farewell conductivity (4.22 S m−1) while preserving tissue‐like compliance (Young's modulus ≈32 KPa), excellent stretchability (≈600%), high adhesion as well as superior anti‐drying properties. In addition, a stretchable sEMG electrode for long‐term reliable service is fabricated via immobilizing the organohydrogel electrodes onto a flexible very high bond (VHB) substrate. As a result, the integrated electrodes show high signal‐to‐noise ratio (SNR) (35.15 db) comparable to that of the commercial electrodes. Furthermore, with assistance of deep learning, the proposed sEMG electrodes obtain high identification accuracy of 97.11% in distinguishing sophisticated gestures. This system can be further exploited for real‐time tele‐operations and offers broad prospects in human–machine immersive interactive application.

Optimisation of the investment strategy of the Norwegian Sovereign Wealth Fund by adjusting the real estate quota

Purpose This paper compares the benefits of direct international real estate investments in a mixed asset portfolio from the perspective of a passive investor with high and low bond allocation.Design/methodology/approach Due to high data availability and its professionalism, the Norwegian sovereign wealth fund was used as a representative example. Real estate indices from 8 countries were used for the portfolio analysis. The data were desmoothed according to Geltners’s 1993 approach.Findings The optimal real estate ratio in the present case is around 20–55%. However, this is strongly dependent on the bond ratio of the multi-asset portfolio. Portfolios with a high equity ratio benefit more from the additional direct real estate investments than portfolios with high bond ratios.Research limitations/implications A rebalancing of individual stocks and bonds was not analysed. Only indexes from MSCI (Morgan Stanley Capital International) were available.Practical implications Concludes that the weighting of stocks and bonds has a strong influence on the optimal real estate ratio and therefore structural changes that affect this weighting.Originality/value The originality of the paper lies in the analysis with different weights of stocks and bonds, the consideration of 8 real estate markets and the observation period. The results of the work highlight areas of interest for further research.

Mechanical response of adhesive and hybrid joints containing novel additive manufacturing adherends

The paper presents a novel concept of purely adhesive and hybrid joints fabrication with the application of Additive Manufacturing (AM) technology. 5 different models of metal-polymer single lap joints (SLJ) were manufactured using VHB (Very High Bonding) 5925 double-sided tape and experimentally tested. To reduce the SLJ eccentricity during the tensile loading an appropriate chamfering of the polymer part shape was proposed by applying the AM technology. The Zortax M300 printer was used to produce the polymer adherends and “dog bone” type specimens, which allowed the determination of tensile strength, which value was 6.62 MPa. The effectiveness of the joints was assessed by the maximum force values, the absorption energy, and the repeatability of the results for each model. The highest force of 400.4 N was obtained for the single-lap reference model. Finally, hybrid joints were produced by the application of double-sided tape and mechanical connectors, like tenons placed in the 3D printed polymer part and mortises situated in the aluminium adherends. This new joining technique allowed for an increase in maximum force to a value of 832.5 N.

Alternatives to amalgam: Is pretreatment necessary for effective bonding to dentin?

The aim of this study was to determine whether pretreatment of the dentin surface is beneficial or not by analysis of the bond strengths of four self-adhesive restoratives and four restoration materials where pretreatment of dentin was necessary. Bovine incisors (n=160) were ground flat on the labial surfaces to expose dentin using a grinder and silicon carbide (SiC) abrasive papers under running water. Between preparation and bonding procedures, the crowns were stored in Chloramine-T solution at 4°C. Eight different restorative materials were studied: Activa BioActive (ABA), Cention Forte (CNF), Ceram.x Spectra ST (CXS), Riva self-cure (RSC), Equia Forte (EQF), Fuji II LC (FJI), Ketac Molar (KTM), Surefil one (SFO). Four materials required pretreatment of the dental hard tissue before placement, whereas the other four were self-adhesive (no pretreatment). The specimens were mounted vertically in plaster. A preload of 5N was applied and the subsequent cross-head speed was 0.8mm/min. Shear bond strengths (MPa) were calculated as the failure load divided by the bonding area. Failure modes were recorded as adhesive, cohesive or pretest. Data were statistically analyzed via ordinal regression for inference and Tukey's method to adjust for multiple comparisons. All computations were done using R version 4.1.2 (R Core Team 2021). Smax (failure stress in MPa) of the combined groups with pretreatment were significantly higher than the self-adhesive materials. The highest frequency of pretest-failure was seen with FJI. Glass-ionomer cements without pretreatment were the only restoratives with pretest failures. Amongst materials without pretreatment, SFO had the highest bond strengths. The further reduction of the placement steps for materials used as an amalgam alternative, namely the omission of pretreatment of the dentin, results in these self-adhesive materials having lower bond strengths than materials that require pretreatment of the dentin.

Enhanced Interfacial Adhesion of Nylon 66 to Epoxy Resin EPON 825 by Non-thermal Atmospheric Pressure Dielectric Barrier Discharge Plasmas

Poly(hexamethylene adipamide), nylon 66, is a popular plastic that requires high surface wettability and strong adhesive bonds for many applications. However, pristine nylon is difficult to bond due to its hydrophobic nature and poor surface wettability. The objective of this work was to modify the physio-chemical surface properties of nylon 66 via a novel atmospheric plasma surface treatment approach using oxygen (O2) or water vapor (H2O) plasma glow. The surface hydrophilicity of the plasma-treated nylon surface was substantially enhanced immediately after either helium (He)/H2O or He/O2 plasma surface treatment. The average water contact angle was reduced from 65 degrees to ~30 degrees after He/H2O plasma and ~40 degrees after He/O2 plasma treatments. The improved hydrophilicity was also evidenced by the increased intensities of the surface oxygen and hydroxyl bonds in the X-ray photoelectron spectra. The interfacial adhesion strength of nylon surfaces before and after plasma treatment was further evaluated by uniaxial tensile tests of nylon single-joint lap shears bonded with three adhesives, i.e., thermoset epoxy resins EPON 825/ JEFFAMINE D-230 and EPON825/JEFFAMINE D-2000, and the thermoelastic polyurethane adhesive Sikaflex 252. The most significant improvements in bond strengths due to plasma treatment were found for lap shears bonded with the EPON 825/JEFFAMINE D-230 epoxy resin; their shear strengths with maximum loads were more than doubled—from 299–451 to 693–1594 N—after plasma treatment and were further enhanced by a factor of four to 895–1857 N after a subsequent silane treatment. In contrast, the bond strength of lap shears bonded with EPON 825/JEFFAMINE D-2000 and Sikaflex was not significantly improved because of the different a, re-affirming the importance of adhesive bulk properties This work presents the preliminary success of effective surface functionalization leading to enhanced interfacial adhesive bonds for nylon 66 via the development of scalable atmospheric plasma surface treatments.

The bond strength development of coconut wood in relation to its density variations

ABSTRACT This study examines the influence of density variations in coconut palm wood (Cocos nucifera L.) on bond strength development using three types of adhesives: urea formaldehyde (UF), melamine urea formaldehyde (MUF), and polyvinyl-acetate (PVAc). A special testing device called Automated Bonding Evaluation System (ABES) was used to investigate the bond strength development between coconut veneers as a function of adhesive type, wood density (moisture content of 10%), pressing time, and bond-temperature development. Coconut wood density was shown to greatly affect the bond line. The bond strength of medium-density material (600–700 kg/m3) was lower than that of high-density material (900–1,000 kg/m3). Interestingly, the medium-density coconut veneers achieved higher bond strength with shorter pressing times, while the high-density coconut veneers reached better results with longer pressing times. Moreover, the bond strength improved by increasing the hot-pressing time resulting in higher bond-line temperatures. A comparison was made between coconut wood and beech wood for similar bonding parameters.

Effectiveness of investing in war bonds

When facing the threat of war, one of the critical decisions the authorities are obliged to take concerns war finance. The most common methods are taxation and debt. The work addresses financing war through war bonds and the profitability of investments in these bonds from investors’ perspectives. Research has shown that parties to a conflict at the beginning of warfare can obtain cheap financing. As the conflict develops, bond yields increase but only to a certain level. Once a certain threshold is exceeded, there is no increase in the yield. The phenomenon was explained by the clientele effect, i.e., the differentiation of groups that purchase financial instruments. The first issuances of war bonds are mainly covered by investors seeking profit and the so-called “patriotic demand”. As the conflict develops, the risk increases, and only patriotic demand persists. The second regularity observed is that it is unprofitable to invest in war bonds. It appears inefficient since war bonds are below the CAPM line. The inefficiency results from patriotic demand, namely when bonds are purchased by citizens whose desire for profit is of secondary importance. The analysis also shows that countries, where no warfare is taking place are more likely to discharge their obligations. That is logical, as economies of not destroyed countries are more likely to repay their liabilities. However, it indicates that the war bond market is not efficient. Investors should consider their expectations and request higher bond yields, which has not happened so far. Another regularity noted is that, at the beginning of the conflict, bonds do not signal which side to the conflict has a better chance of winning.

Mechanical Properties of SDR™ and Biodentine™ as Dentin Replacement Materials: An In Vitro Study

The aim of this study is to evaluate the shear bond strength of nanohybrid composite resins (NCR) and microhybrid composite resins (MCR) placed over three different dentin replacement materials: SDR-Smart Dentin Replacement™, Biodentine™, and resin-modified glass ionomer cement (RMGIC). Thirty acrylic blocks (50 mm × 20 mm × 15 mm), each with a central hole, were prepared, which were randomly distributed into three equal groups, each corresponding to one of the three dentin replacement materials-SDR, Biodentine, and RMGIC. The central holes were then filled with these materials. After setting and application of the respective adhesive system, the specimens were further divided into two subgroups each of NCR or MCR. The respective composite material was then applied to the dentin replacement materials using a cylindrical plastic matrix. Shear bond strength was tested on a universal testing machine (Instron 3366), at a crosshead speed of 1.0 mm/minute. SDR attained consistently higher shear bond strength (means: 21.18, 22.19 Mpa) values than RMGIC and Biodentine, with both types of composite resins (MCR and NCR), which were statistically significant (p <0.001). When considering the means of the shear bond strength measurements obtained by the two types of the composite resin, no significant difference (p <0.05) was found between them with all three types of dentin replacement materials. There is no significant difference in the bond strengths achieved between MCR and NCR to the different dentine replacement materials. Hence, either type of composite resin may be expected to achieve similar bond strengths to the underlying substrate. SDR™ is a suitable dentine replacement material for placing below a composite resin veneer as it can achieve immediate higher bond strengths. SDR can be used as an effective bulk fill material in deep dentinal caries which can be capped with composite resins.

Numerical simulation of single bubble motion along inclined walls: A comprehensive map of outcomes

The bubble interactions with a wall affect many industrial application's performance. The single bubble rising in a stagnant fluid is studied next to an inclined wall. The two phases are incompressible, and the interface between phases is captured with the volume of fluid (VoF) method. The influence of various parameters such as wall slope (θ), contact angle (φ), and dimensionless numbers (Morton and Bond) on the bubble-wall regime is investigated. The numerical results (bubble shape and terminal velocity) are validated with experiments.After comprehensive numerical simulation over a wide range of Bond (1≤Bo≤40) and Morton (2.54×10−11≤Mo≤1×100) for inclined walls (0∘<θ<90∘), three bubble-wall interaction regimes: sliding, intermittent and non-contact are proposed and a regime map is plotted. We recognized two sliding regimes based on Bond numbers at small inclined walls (θ≤30∘). In the sticking sliding regime (Bo≤5), bubbles remain attached to the inclined wall. They make the wall dry along their path. But at higher Bond in film sliding, bubbles slip over a thin liquid film. Thus, the wall surface is always wet. The film thickness is linearly proportional to bubble diameter. Non-contact regimes occur at steep walls (θ≥70∘), where the bubble never touches the wall. In moderate wall slopes (30∘<θ<70∘), a bubble repeatedly impacts on and rebounds from the wall. The intermittent regime is an unstable regime, and it alters to a sliding or a non-contact regime based on Bond and Morton numbers.

Enhancement of Pressure‐Sensitive Adhesive by CO 2 Laser Treatment

Pressure-sensitive adhesives (PSAs) are polymeric films that can be adhered to and detached from surfaces without leaving residue. Researchers are looking to enhance the bond strength between PSAs and different substrates. It can be achieved by tuning PSA's peeling, shear, and tack properties for every specific case. ‘Very High Bond’ (VHB) is a widely used PSA because of its high compliance suitable for stretchable and soft-matter devices. In this study, a simple and fast surface treatment approach to modify the adhesion of VHB by CO2 laser engraving is reported. We characterized this surface treatment method for VHB with different substrates. Multiple laser settings were tested for each material combination to determine the conditions at which the surface adhesion would be the highest. Tests on mechanical properties, ablation directions, chemical composition, tackiness, surface viscosity, and peeling forces were conducted to understand the adhesion and viscoelasticity changes. A higher concentration of non-crosslinked materials was determined in the VHB structure after treatment than before. Thus, we reason that laser treatment changes the surface adhesion of the PSA by cleavage of the polymer network. This work provides a simple route for tuning peeling, shear, and tack forces of a popular VHB using common equipment.

Electroactive Polymer-Based Soft Actuator with Integrated Functions of Multi-Degree-of-Freedom Motion and Perception.

Soft actuators have received extensive attention in the fields of soft robotics, biomedicine, and intelligence systems owing to their advantages of pliancy, silence, and essential safety. However, most existing soft actuators have only single actuation elements and lack sensing. Therefore, it is difficult for them to perform complex motions with multiple degrees of freedom (multi-DOFs) and high precision. This article reports a miniature columnar dielectric elastomer actuator (DEA) with multi-DOF actuation and sensing, which was fabricated with an electroactive polymer acrylic film (Very High Bond [VHB] acrylic film by 3M Company) and carbon black grease electrodes. The arrangement of the simulation electrodes on the VHB was optimized to realize multi-DOF actuation, and the sensing electrodes were configured on the outer part of the DEA to realize real-time sensing. The results showed that the soft actuator can achieve all-round actuation through the selective power of the stimulation electrodes with a controllable voltage. The maximum bending angle and axial strain of the actuator reached 50° and 13%, respectively. Moreover, the deformation modes, direction, and quantity could be precisely measured using the integrative sensing function. In addition, to demonstrate the advantages of the proposed actuator, a manipulator with multiple actuators was designed and controlled to realize different actions of screwing and grasping with sensing. This research is useful not only for the design of multifunctional soft actuators but also for the development of soft robots with flexible, complex, and precisely controllable motions.

Influence of the atmosphere and temperature on the properties of the oxygen-affine bonding system titanium-diamond during sintering

Grinding tools can be manufactured from metal, vitrified, and resin bond materials. In combination with superabrasives like diamond grains, metal-bonded tools are used in a wide range of applications. The main advantages of metal over vitrified and resin bonds are high grain retention forces and high thermal conductivity. This paper investigates the influence of the atmosphere and manufacturing parameters such as sintering temperature on the properties of titanium-bonded grinding layers. Titanium is an active bond material, which can increase the retention of diamond grains in metal-bonded grinding layers. This can lead to higher bond stress and, consequently, decreased wear of grinding tools in use when compared to other commonly used bond materials like bronze. The reason for this is the adhesive bond between titanium and diamond due to the formation of carbides in the interface, whereas bronze can only form a mechanical cohesion with diamond grains. However, when using oxygen-affine metals such as titanium, oxidizing effects could limit the strength of the bond due to insufficient adhesion between Ti-powder particles and the prevention of carbide formation. The purpose of this paper is to show the influence of the sintering atmosphere and temperature on the properties of titanium-bonded diamond grinding layers using the mechanical and thermal characterization of specimens. A higher vacuum (Δpatm = − 75 mbar) reduces the oxidation of titanium particles during sintering, which leads to higher critical bond stress (+ 38% @ Ts = 900 °C) and higher thermal conductivity (+ 3.4% @Ts = 1000 °C, Ta = 25 °C). X-ray diffraction measurements could show the formation of carbides in the cross-section of specimens, which also has a positive effect on the critical bond stress due to an adhesive bond between titanium and diamond.

Profile structures for economical hybrid lightweight design

Especially in the transport sector, lightweight design with fiber reinforced plastics (FRP) is of major relevance due to CO2 reduction through mass saving [1]. In sectors like automotive, FRP are mainly used in secondary structures such as seat shells. In order to be able to operate effective FRP lightweight design in load-bearing structural components, pultruded hybrid profiles are to be established as a new tool for engineers. The profile components are characterized by a FRP base structure and a metallic core that increases the ductility. The manufacturing of the components with pultrusion ensures a large scale production. To guarantee a high covalent bond between the metal cores and the FRP, the inserts are provided by using a newly developed powder coating, which acts like a latent reactive adhesive [2]. Three different profile constructions have been verified, which are identical in the external cross-sectional shape and size, but differing in core structure. A glass-FRP-steel-combination was chosen as material and a pure FRP sample was used as a reference. The mechanical properties were investigated by using a 4-point bending test. Depending on the core structure, various failure behavior and mechanical parameters like energy absorption could be determined.

Dearomative Periphery Modification of Quinolinium Salts to Assemble Ring-Encumbered Pyrrolidine-Tetrahydroquinoline Polycycles.

We report an unexpected dearomative periphery modification strategy for transforming quinolinium salts into structurally crowded pyrrolidine-tetrahydroquinoline polycyclic systems with complete regio- and diastereoselectivity. Importantly, the reaction pathway was regulated by simply tuning the substituents, achieving substituent-directed divergent synthesis. The notable features of this transformation include readily available starting materials, green conditions, a simple workup procedure, high bond- and ring-forming efficiency, and substituent-directed diverse synthesis.

Push-out Bond Strength of Two Fiber Posts in Composite Resin Using Different Types of Silanization.

The aim of this study was to evaluate the effect of different surface treatments and thermocycling (TC) on the push-out bond strength of two brands of glass fiber posts (GFPs) to composite resin. White Post DC (WP) (FGM Dental Group International, Joinville, Santa Catarina, BR) and Exacto (EC) (Angelus, Clinical Research Dental, Londrina, PR, Brazil). GFPs were cleaned with 70% alcohol and divided into five groups, according to the surface treatment (n=15): control (C), without treatment; prehydrolyzed silane (S-pre) (Prosil, FGM Dental Group International); 37% phosphoric acid + prehydrolyzed silane (AcS-pre); Scotchbond Universal Adhesive System (AdU), 3M Oral Care; two-bottle silane (S2B) (Dentsply Sirona Inc). The composite resin was inserted around the posts by using a split matrix. The samples were cut into 1-mm slices. Half of the samples were subjected to the push-out test immediately, and the other half underwent TC before the test. After failure analysis, the data were submitted to three-way analysis of variance (ANOVA) (α=0.05). EC achieved higher bond strength than WP, regardless of TC (p<0.05). Regarding WP, surface treatments (p<0.001) and TC (p<0.001) influenced bonding strength. As for EC without TC, the highest bond strength (p<0.05) was found for C, then AcSpre, S-pre, AdU, and S2B. Application of TC resulted in a statistically higher bond strength values for the EC AcS-pre group (p<0.05), followed by S2B, S-pre, C, and AdU. The WP failures were predominantly cohesive, similar to the EC AdU and EC S2B groups. The other EC groups showed mostly mixed failures. Surface treatment and TC affected the bond strength to composite resin, depending on which post was used. It is important for dentists to understand the effects of different types of silanization on their chosen post.

Chlorhexidine added to different adhesive systems - Assessment of antibacterial activity and bond strength

This study aimed to assess the effects of adding chlorhexidine (CHX) to different adhesive systems on antibacterial activity and bond strength after 24 hours and 30 days under in vitro conditions. A total of 210 bovine incisor crowns and divided into three groups, based on the adhesive system: Single Bond Plus (SB), Clearfil SE Bond (CL), and AdheSE Primer and Bond (AD). All groups were subdivided by CHX concentration (n=7): no CHX, CHX applied before the adhesive (CPA), and the adhesive incorporated with 0.5% CHX, 1.0% CHX, and 2.0% CHX. The micro shear test was conducted on one-half of the specimens after 24 hours, and on the other half after 30 days. Antibacterial activity was evaluated using the agar diffusion test with Streptococcus mutans. The bond strength variable was assessed using the factorial analysis of variance for repeated measurements, whereas the variable of the bacterial halo size was subjected to the Kruskal–Wallis nonparametric test. The significance level was 5% for both tests. The qualitative variable of fracture pattern was assessed by descriptive statistical analysis. Thus, CHX concentration of 2% (10.80 ±2.83) and CPA (9.95 ±1.47) (p &gt;0.05) helped to increase the bond strength values for most adhesive systems, whereas CL had the highest bond strength values. The CL adhesive system also presented the best results in the antibacterial test with S.mutans.

Curing through Ceramics: Influence of Different Light-Curing Units and Curing Modes on Bond Strength

Objectives: To measure and compare the bond strength between three different types of ceramics and resin cement, as well as the degree of conversion of resin cement after using different light-curing units and curing modes. Methods: Three types of ceramics—Leucite-reinforced (Empress CAD), Lithium disilicate (Emax CAD), and Zirconia (Emax ZirCAD)—of varying thicknesses (1.5 mm and 2.0 mm) were bonded to a light-cure resin cement (Variolink Esthetic LC). Light-curing was carried out using a monowave LCU (3M Elipar DeepCure-S LED Curing Light with irradiance of 1470 mW/cm2) and with polywave LCU (Ivoclar Bluephase PowerCure) using High, Turbo, and 3 s curing modes, respectively (1200, 2100, 3000 mW/cm2). A chevron-notch bond strength test (total n = 288) was conducted to calculate the fracture energy and interfacial bond strength (J/m2). The degree of cure (%DC) of the residual resin cement on debonded surfaces was measured using Fourier Transform Infrared Spectroscopy (FTIR). Collected data were statistically analysed under SPSS ver. 27 by conducting an ANOVA and Bonferroni post hoc test. The mode of failure was established using a scanning electron microscope (SEM). Results: A significant difference in interfacial bond strength was found between the three types of ceramic material groups (p &lt; 0.01). Cement cured through Empress that was 2 mm thick showed the highest bond strength (1.36 ± 0.46 J/m2), while the lowest was observed (0.26 ± 0.07 J/m2) in 2 mm Emax CAD using the 3 s mode. The use of different LCUs and curing modes had a significant influence on the %DC of resin cement seen in all groups, except 2 mm Emax ZirCAD. The dominant mode of failure for Empress, EmaxCAD, and EmaxZirCAD were cohesive, adhesive, and mixed, respectively. Conclusions: The type of ceramic and its thickness can significantly affect bond strength, and the results showed that polywave LCU is more effective than monowave LCU when curing through ceramics.

Abstract P3-02-08: Diagnosis, navigation, treatment: A versatile biocompatible and biodegradable mesoporous silica platform of NIR II fluorescence imaging for early diagnosis, breast cancer precisely surgery, and radiosensitization

Abstract Background: Triple-negative breast cancer (TNBC) has the highest recurrence and distant metastasis rates among breast cancer molecular types. In breast-conserving surgery, the insensitivity discrimination of negative margins correlating with locoregional recurrence and poor patient outcomes. As for immunotherapy, only 20 %-40 % of the patients respond to the atezolizumab treatment due to the change of PDL1 receptor. Meanwhile, TNBC has radiotherapy resistance. Novel radiosensitization targets need to be found to enhance both the local and systematic benefits of radiotherapy. Objectives and rationale: We aim to construct an “all in one” multi-functional nanoprobe (MSN-Gd@Aptamer-ICG, NPs) using mesoporous silica as the framework. The mesoporous silica nanospheres are co-doped with gadolinium (Gd3+), loads indocyanine green (ICG) in its mesoporous channel, and conjugates with a specific PDL1 targeting aptamer on the surface. The biocompatible and biodegradable NPs are capable of release ICG by the reaction of intracellular high GSH and tetrasulfide bonds in silica frame. In the diagnosis, NIR II fluorescent imaging of ICG with the high resolution and deep tissue penetration depth screens out PDL1 highly expressed tumors. In surgical resection, it can show a real-time cancerous tissues margin in intraoperative scenarios and the tumors are successfully remove under the navigation of NIR II fluorescent imaging. During metastasis therapy of post-operation, the released Gd3+ effectively deposits X-rays and produces abundant hydroxyl radicals (•OH) and oxidative stress to induce radiosensitizing effects. More importantly, the therapy efficiency is monitored by NIR II fluorescent imaging. Therefore, our multifunctional NPs have roles in the accurate diagnosis of PDL1 expression of tumor in early stage, intraoperative navigation for radical excision, and metastasis eradication with radiosensitization efficiency enhanced, which lays a solid foundation for clinical TNBC therapy. Methods: The probe was 50 nm and it was successfully synthesized and certified. MTT assay suggested that it was nontoxic to normal breast cells and TNBC cells. Transmission Electron Microscope images showed that the probe was stable at the extracellular fluid and was degradable at tumor intracellular conditions. The leaching of ICG and Gd3+ was negligible at the extracellular fluid. The tumor targeting capability of the probe in vitro was evaluated on 4T1 (TNBC, PDL1 low expressed) and MDA-MB-231 (TNBC, PDL1 high expressed) cells by flow cytometry and laser confocal microscope. In vivo, the NIR II fluorescence imaging with a high resolution and tissue penetration depth successfully distinguished 4T1 and MDA-MB-231 bearing mice indicated the superior diagnostic capability of PDL1 via aptamer. In the surgical resection, the NIR II fluorescence imaging of NPs guided to remove the tumor with precisely discriminate the boundary of the tumor. When combined with RT, IHC staining of Ki67 showed that the NPs exhibited superior radiosensitizing effects under NIR II fluorescent imaging guidance in comparison with undoped Gd mesoporous silica nanoprobes. TUNEL fluorescent staining and H&amp;E staining further confirmed that NPs radiation therapy induced more •OH and extensive DNA double-strand breaks. Results and Conclusion: Our biocompatible and biodegradable platform is nontoxic, can screen out PDL1 high expression tumors, and navigate the precise resection in the operation. Besides, it enhances the radioimmunotherapy efficacy of breast metastasis. Our platform is potential to provide new hope for breast cancer diagnostic, guiding resection, and radiosensitization under NIR II fluorescent imaging. Citation Format: Min Wei, Peiyuan Wang, Guojun Zhang. Diagnosis, navigation, treatment: A versatile biocompatible and biodegradable mesoporous silica platform of NIR II fluorescence imaging for early diagnosis, breast cancer precisely surgery, and radiosensitization [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-02-08.

How the translucency of direct anatomic fiber posts affects the bond strength and microhardness of a self-adhesive luting agent in flared roots.

To evaluate the influence of the composite resin translucency used in direct anatomic fiber posts on the bond strength (BS) and microhardness (VHN) of a luting agent into flared roots. The root canals of 70 single-rooted premolars were endodontically treated and prepared to simulate an oversized root canal. Prior to post cementation, composite resins with varying translucency (high translucent, HT; medium translucent, MT; high opacity, HO) were placed around the fiber posts to create anatomic fiber posts. The attenuation profile (%) of light passing either through the post or through the anatomic posts (n = 8) was obtained prior to the cementing procedures. A positive control group (PC) in which a prefabricated fiber post (PFP) with the diameter compatible with the root canal was cemented and a poorly adapted fiber post (negative control group, NC) were also evaluated. For both tests, the data were subjected to 2-way ANOVA and Bonferroni tests (α = 0.05). A more severe light attenuation through the post at the cervical (P < .001) and medium (P < 0.001) thirds was noted when less translucent composite resin surrounded the anatomic post. HO groups showed lower BS (P = .009) and VHN (P < .001) values than the other groups, regardless of root third. No significant difference in BS values was noted between PC and HT groups. The use of a more translucent composite resin in anatomic fiber posts increased the microhardness and bond strength of a dual polymerization self-adhesive RLA compared to the use of MT and HO composite. A well-adapted PFP showed the highest adhesive and mechanical behavior. Clinicians should choose more translucent composite resins to create direct anatomic fiber posts to be cemented in flared root canals. That choice may allow improved mechanical properties of self-adhesive RLA and higher bond strength to the root canal as a consequence.