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The complexity of wrist anatomy and mechanics makes it challenging to develop standardized measurements and establish a normative reference database of wrist biomechanics despite being studied extensively. Moreover, heterogeneity factors in both demographic characteristics (e.g. gender) and physiological properties (e.g. ligament laxity) could lead to differences in biomechanical behaviour even within healthy groups. We investigated the kinematic behaviour of the carpal bones by creating a virtual web-like network between the bones using electromagnetic (EM) sensors. Our objective was to quantify the changes in the carpal bones’ biomechanical relative motions and orientations during active wrist motion in the form of orb-web architecture. Models from five cadaveric specimens at different wrist positions: (1) Neutral to 30° Extension, (2) Neutral to 50° Flexion, (3) Neutral to 10° Radial Deviation, (4) Neutral to 20° Ulnar Deviation, and (5) Dart-Throw Motion – Extension (30° Extension/10° RD) to Dart-Throw Motion Flexion (50° Flexion/20° UD), in both neutral and pronated forearm have been analyzed. Quantification analyses were done by measuring the changes in the network thread length, as well as determining the correlation between the threads at different wrist positions. We observed similarities in the kinematic web-network patterns across all specimens, and the interactions between the network threads were aligned to the carpal bones’ kinematic behaviour. Furthermore, analyzing the relative changes in the wrist web network has the potential to address the heterogeneity challenges and further facilitate the development of a 3D wrist biomechanics quantitative tool.

Red blood cells (RBCs) capability to deliver oxygen (O2) has been routinely measured by P50. Although this defines the ability of RBCs to carry O2 under equilibrium states, it cannot determine the efficacy of O2 delivery in dynamic blood flow. Here, we developed a microfluidic analytical platform (MAP) that isolates single RBCs for assessing transient changes in their O2 release rate. We found that in vivo (biological) and in vitro (blood storage) aging of RBC could lead to an increase in the O2 release rate, despite a decrease in P50. Rejuvenation of stored RBCs (Day 42), though increased the P50, failed to restore the O2 release rate to basal level (Day 0). The temporal dimension provided at the single-cell level by MAP could shed new insights into the dynamics of O2 delivery in both physiological and pathological conditions.Kevin Ziyang Chng et al. develop a microfluidic platform using a fluorescence quenching approach to assess transient changes in oxygen release rate of single red blood cells. They observe that biologically older red blood cells have a faster O2 release rate than younger cells and that storage of blood enhances this release rate.

Advances in material science and innovative medical technologies have allowed the development of less invasive interventional procedures for deploying implant devices, including scaffolds for cardiac tissue engineering. Biodegradable materials (e.g., resorbable polymers) are employed in devices that are only needed for a transient period. In the case of coronary stents, the device is only required for 6–8 months before positive remodelling takes place. Hence, biodegradable polymeric stents have been considered to promote this positive remodelling and eliminate the issue of permanent caging of the vessel. In tissue engineering, the role of the scaffold is to support favourable cell-scaffold interaction to stimulate formation of functional tissue. The ideal outcome is for the cells to produce their own extracellular matrix over time and eventually replace the implanted scaffold or tissue engineered construct. Synthetic biodegradable polymers are the favoured candidates as scaffolds, because their degradation rates can be manipulated over a broad time scale, and they may be functionalised easily. This review presents an overview of coronary heart disease, the limitations of current interventions and how biomaterials can be used to potentially circumvent these shortcomings in bioresorbable stents, vascular grafts and cardiac patches. The material specifications, type of polymers used, current progress and future challenges for each application will be discussed in this manuscript.

The complexity of aortic diseases demands sophisticated modeling approaches to better understand their pathophysiology and optimize treatment strategies [...].The complexity of aortic diseases demands sophisticated modeling approaches to better understand their pathophysiology and optimize treatment strategies [...].

Heart failure (HF) with preserved ejection fraction (HFpEF) accounts for about half of heart failure cases, but the progression of cardiac biomechanics during pathogenesis is not completely understood. We investigated a published porcine model of HFpEF, generated by progressive constriction of an aortic cuff causing progressive left ventricle (LV) pressure overload, and characterized by hypertrophy, diastolic dysfunction and overt HF with elevated plasma beta natriuretic peptide (BNP). We characterized morphological and functional features and performed image-based finite element modelling over multiple time points, so as to understand how biomechanics evolved with morphological and functional changes during pathogenesis, and to provide data for future growth and remodeling investigations. Results showed that the hypertrophic responses quickly manifested and were effective at preventing an elevation of systolic myocardial stresses, suggesting active compensated remodeling. Consequent to the hypertrophy, diastolic myocardial stresses decreased despite the elevations in diastolic pressures. The left ventricle hypertrophy (LVH) myocardium also exhibited a quick elevation of active tension at the onset of the disease. There was a progressive and significant decrease in myocardial strain, which was more significant in the longitudinal direction. Further, elevated myocardial stiffness and diastolic pressures, which reflected diastolic dysfunction, also manifested, but this was delayed from the onset of the disease. Correlation analysis showed that hypertrophy was closely correlated to systolic pressure, active tension and systolic myocardial stress, suggesting that these factors may play a role in initiating hypertrophy. Myocardial stiffness was weakly correlated to LV pressures and myocardial stresses.

Superhydrophobic (SHP) surfaces can provide substantial reductions in flow drag forces and reduce blood damage in cardiovascular medical devices. However, strategies for functional durability are necessary, as many SHP surfaces have low durability under abrasion or strong fluid jetting or eventually lose their air plastron and slip-flow capabilities due to plastron gas dissolution, high fluid pressure, or fouling. Here, we present a functional material that extends the functional durability of superhydrophobic slip flow. Facile modification of a porous superhydrophobic polytetrafluoroethylene (PTFE, Teflon) foam produced suitable surface structures to enable fluid slip flow and resist protein fouling. Its monolithic nature offered abrasion durability, while its porosity allowed pressurized air to be supplied to resist fluid impalement and to replenish the air plastron lost to the fluid through dissolution. Active pore pressure control could resist high fluid pressures and turbulent flow conditions across a wide range of applied pressures. The pneumatically stabilized material yielded large drag reductions (up to 50%) even with protein fouling, as demonstrated from high-speed water jetting and closed loop pressure drop tests. Coupled with its high hemocompatibility and impaired protein adsorption, this easily fabricated material can be viable for incorporation into blood-contacting medical devices.Facile modification of a porous superhydrophobic polytetrafluoroethylene foam produced suitable surface structures to enable fluid slip flow and resist protein fouling. Its monolithic nature offered abrasion durability, while its porosity allowed pressurized air to be supplied to resist fluid impalement and to replenish the air plastron lost to the fluid. Active pore pressure control could resist high fluid pressures and turbulent flow conditions across a wide range of applied pressures. The pneumatically stabilized material yielded large drag reductions even with protein fouling. Coupled with its high hemocompatibility, this easily fabricated material can be viable for incorporation into blood-contacting medical devices.

Microvascular anastomosis is fundamental to free-flap reconstruction, yet hand-sutured techniques remain highly skill-dependent and prolong ischemic time, contributing to thrombosis and flap loss. Current suture-less devices accelerate anastomosis but are constrained by vessel-size mismatch, eversion-related intimal injury, and inconsistent arterial performance. A clinically adaptable, arterial-capable system is needed. We developed a customizable, 3D-printed intraluminal coupler with a snap-fit connection and elastic external clasp that avoids vessel eversion and preserves length. Devices were fabricated via SLA or PolyJet printing using clinically used resins. Benchtop evaluation included burst-pressure testing, tensile testing, wettability and endothelial cytocompatibility assays with oxygen-plasma surface modification. Deployment was assessed ex vivo using porcine coronary vessels and in vivo in a porcine carotid arterial model with patency monitoring over 4 h. Couplers sustained leakage pressures of ~ 90 mmHg vs. ~16 mmHg for hand-sutured controls ( P  < 0.01), while maintaining comparable mechanical strength (≈ 2–3 N). Plasma surface treatment reduced water contact angles (≈ 85°→≈60°) and tripled endothelial attachment, restoring confluent morphology. Ex vivo deployment achieved completion in 9.47 ± 1.20 min, a ~ 62.5% reduction vs. published suturing times. In vivo, couplers restored immediate perfusion with no leakage or thrombosis. This 3D-printed intraluminal coupler demonstrates mechanical feasibility, rapid deploy-ability, and surface-modifiable endothelial compatibility in benchtop and short-term large-animal feasibility testing, supporting its potential for further preclinical development as a vascular anastomosis technology. Future survival studies and anti-thrombogenic surface engineering will advance readiness for clinical implementation.

Coronary artery stenting is commonly used for the treatment of coronary stenosis, and different stent structures indeed have various impacts on the stress distribution within the plaque and artery as well as the local hemodynamic environment. This study aims to evaluate the performance of different stent structures by characterizing the mechanical parameters after coronary stenting. Six stent structures including three commercially-shaped stents (Palmaz-Schatz-shaped, Xience Prime-shaped, and Cypher-shaped) and three author-developed stents (C-Rlink, C-Rcrown, and C-Astrut) implanted into a curved stenotic coronary artery were investigated. Structural analyses of the balloon-stent-plaque-artery system were first performed, and then followed by hemodynamic analyses. The results showed that among the three commercially-shaped stents, the Palmaz-Schatz-shaped had the least stent dogboning and recoiling, corresponding to the greatest maximum plastic strain and the largest diameter change, nevertheless, it induced the highest maximum von Mises stress on plaque, arterial intima and media. From the viewpoint of hemodynamics, the Palmaz-Schatz-shaped displayed smaller areas of adverse low wall shear stress (<0.5 Pa), low time-averaged wall shear stress (<0.5 Pa), and high oscillating shear index (>0.1). Compared to the Cypher-shaped, the C-Rcrown and C-Astrut had smaller recoiling, greater maximum plastic stain and larger diameter change, which indicated the improved mechanical performance of the Cypher-shaped stent. Moreover, both C-Rcrown and C-Astrut exhibited smaller areas of adverse low wall shear stress, and low time-averaged wall shear stress, but only the C-Rcrown displayed a smaller area of adverse high oscillating shear index. The present study evaluated and compared the performance of six different stents deployed inside a curved artery, and could be potentially utilized as a guide for the selection of suitable commercially-shaped stent for clinical application, and to provide an approach to improve the performance of the commercial stents.

BackgroundEjection Fraction (EF) has been an important parameter describing cardiac function, because of earlier work demonstrating its correlation with outcomes. However, during conditions such as Heart Failure preserved ejection fraction (HFpEF), EF fails to distinguish HFpEF from healthy patients. There are further reports that EF can be skewed by the geometry of the heart, and Heart Failure (HF) can present a wide variety of cardiac morphologies due to remodelling. The reason for the poor performance of EF and its dependency on geometry is unclear, and it is further unclear if such geometric changes from HF remodelling affects cardiac function. We strive to address this here, and derive an improve and simple EF parameter to resolve this.MethodsWe developed a simple discretized numerical model to relate incompressible myocardial strains to stroke volume. We used data from two porcine animal models of heart failure, one for HFpEF and one for HF reduced EF (HFrEF), and literature clinical measurements to inform our model. We used the model to test the effects of geometric changes relevant to HF on the ability of the heart to convert myocardial strains to flow function.ResultsOur animal models showed that cardiac dilation and wall thickening are primary features relevant to HF. Further investigation via our numerical model showed that wall thickening with no change to strain artificially increased EF, while cardiac dilation with no change to strain artificially decreased EF, demonstrating that EF can be skewed by geometric changes during HF remodelling, and is an inaccurate representation of cardiac function. We further showed that this is because EF is calculated using the endocardial boundary rather than the mid-wall layer, because a corrected EF parameter (CEF) that uses the mid-wall layer for quantification resolves this shortcoming. This CEF became independent of cardiac geometry, and could successfully distinguish HFpEF and healthy heart in our animal models, where EF could not. The CEF can be calculated easily with measurements of EF, wall thickness, and LV inner diameter. We further showed that the myocardial strains at the endocardial and epicardial boundary deviated significantly from each other and from the strains at the mid-wall layer, and this magnitude of deviation depended on the cardiac geometry, suggesting that any quantification of cardiac function using the epi- or endo- boundaries can be skewed by geometric changes to the heart, and will be ineffective. Finally, we tested specific types of HF morphologies, namely, eccentric hypertrophy, concentric hypertrophy, and concentric remodelling with our numerical model. We found that the concentric remodelling morphology is the most inefficient in converting myocardial strains to stroke volume, while eccentric hypertrophy is the most efficient. This may explain why HFpEF hearts, which are likely have wall thickening similar to concentric remodelling, have exercise intolerant, and our results suggest that cardiac dilation during HFrEF is providing advantages to help with flow function.ConclusionWe demonstrated that geometric changes during HF remodeling can significantly impact cardiac function, and can skews functional parameters like EF. We further showed that the reason for EF’s shortcoming is due to a flawed reliance on quantification using the endocardial boundary of the heart rather than the mid-wall layer. We proposed a new CEF parameter to replace EF that can resolve the shortcoming, and that can distinguish HFpEF from healthy hearts.Conflict of InterestNone to declare

In the present work, numerical simulations were conducted for a typical end-to-side distal graft anastomosis to assess the effects of inducing secondary flow, which is believed to remove unfavourable flow environment. Simulations were carried out for four models, generated based on two main features of 'out-of-plane helicity' and 'spiral ridge' in the grafts as well as their combination. Following a qualitative comparison against in vitro data, various mean flow and hemodynamic parameters were compared and the results showed that helicity is significantly more effective in inducing swirling flow in comparison to a spiral ridge, while their combination could be even more effective. In addition, the induced swirling flow was generally found to be increasing the wall shear stress and reducing the flow stagnation and particle residence time within the anastomotic region and the host artery, which may be beneficial to the graft longevity and patency rates. Finally, a parametric study on the spiral ridge geometrical features was conducted, which showed that the ridge height and the number of spiral ridges have significant effects on inducing swirling flow, and revealed the potential of improving the efficiency of such designs.