High-dose radiotherapy is known to enhance cuproptosis, and when combined with copper-coordinated delivery to tumors, it shows promise as a synergistic treatment mechanism. In this study, we present a simple method for synthesizing stimuli-responsive copper-iodide nanoparticles using a commercial, insoluble copper-iodide powder that emitted a strong radioluminescence matching the absorbance of the clinical dye indocyanine green. The copper-iodide nanoparticles efficiently absorbed and transferred radiation energy to ICG activating an X-ray-induced photodynamic therapy (X-PDT) mechanism. After accumulating in tumors, the low-dose X-PDT process first generated reactive oxygen species to induce cell death. The tumor microenvironment then caused the copper-iodide nanoparticles to decompose and release copper and iodide ions, which promoted cuproptosis. X-PDT followed by ion-induced cell death achieved 87.7% tumor regression in CT26 tumor-bearing mice without systemic toxicity. This work establishes a therapeutic paradigm that exploits metal metabolism dysregulation to potentiate radiation-based therapies. STATEMENT OF SIGNIFICANCE: Stimuli-responsive copper-iodide nanoparticles were synthesized and induced by X-ray-induced photodynamic therapy to decompose, releasing copper and iodide ions that caused tumor cell death. (1) Commercial copper-iodide powder exhibited strong radioluminescent properties and formed stable nanoparticles with the clinical dye indocyanine green, which realized X-ray-induced photodynamic therapy under X-ray irradiation. (2) After accumulating in tumors and following X-ray-induced photodynamic therapy, the decomposition of copper-iodide nanoparticles in the tumor tissue induced cell death.

Bacterial adhesion to biomaterials/tissues can lead to inevitable infection, inflammation, and even death, posing a serious threat to human health. An in-depth understanding of interactions between bacteria and biomaterial surfaces could provide effective strategies for inhibiting bacterial adhesion. Adhesion behavior can be quantified using adhesion forces measured by atomic force microscopy (AFM)-based force spectroscopy. Although AFM-based force spectroscopy has been applied to investigate bacterial adhesion, the effect of biomaterials (including metals, ceramics, polymers, and cells) and surface modifications (including patterning and coating) on bacterial adhesion forces has not been systematically summarized. Therefore, this review provides a comprehensive overview of recent developments in bacterial adhesion on biomaterials, focusing on the use of AFM-based force spectroscopy with bacterial probes. Surface topography on metals and ceramics reduces the contact area and inhibits bacterial adhesion. Coatings and chemical modifications on ceramic surfaces can either inhibit or promote bacterial adhesion, depending on the surface properties. The discussion about the bacterial adhesion on different biomaterial surfaces would benefit the inhibition of adhesion and the rational surface design for enhanced antibacterial properties. STATEMENT OF SIGNIFICANCE: The growing threat of antimicrobial resistance has led to increased interest in developing antibacterial materials with tailored surface properties. A critical aspect of understanding bacterial adhesion on surfaces is quantifying bacterial adhesion forces, often using atomic force microscopy (AFM)-based force spectroscopy. While numerous studies have explored how biomaterials and surface modifications influence bacterial adhesion, a systematic review focusing on the nanomechanical aspects of adhesion forces is lacking. Here, a broad overview of the state-of-the-art research addresses this gap by summarizing the influence of biomaterials and surface modifications on bacterial adhesion forces in the context of AFM-based force spectroscopy. It will be of interest to researchers designing more effective antimicrobial materials and surfaces.

Mitral valve mechanics play a significant role in its function and alterations in mechanics are classical indicators of valvular disease. In-vivo large animal models are inherently limited for the study of mitral mechanics, as they lack pathology, anatomical consistency and reproducibility. In-vitro flow rigs with ex-vivo specimens have similar issues. Synthetic mitral valves are being developed for flow examinations, but to-date lack anisotropy and capacity for physiological pressures and flow simultaneously. In this work, a mechano-mimetic synthetic mitral valve with anisotropic leaflet mechanical properties is presented with experimental findings and complemented by finite element predictions. Attaining peak systolic transmitral pressures exceeding 120 mmHg with flow rates greater than 3.5 L/min, this represents a significant advancement over existing synthetic approaches. This low-cost physical model addresses the compelling need for anatomically representative, repeatable, and durable synthetic mitral valves with precise control over leaflet thickness and incorporating anisotropic material properties to advance our understanding mitral mechanics. STATEMENT OF SIGNIFICANCE: Synthetic mitral valves models are an increasingly important tool in studying mitral valve mechanics. However, there are few models available currently, most of which have limitations such as lack of anisotropy, precise control over leaflet thickness, reproducibility, and/or capability to replicate physiological flows. The mechano-mimetic mitral valve presented in this study is the first of its kind to be anisotropic, anatomically representative with precise control over leaflet thickness and chordae attachment, and reproducible. The separate chordae allow adjustment of chordae tension individually and proper closure of the valve, leading to physiological pressures and flow inside the flow rig. This work paves the way for more representative synthetic mitral valve models and realistic experimental simulations of mitral valve mechanics.

Many marine sessile organisms achieve robust underwater adsorption through 3,4-dihydroxyphenylalanine (Dopa)-independent strategies, yet the underlying self-assembly mechanisms remain elusive. Here, we decipher the Ca2+-triggered interfacial adsorption of a sea anemone thrombospondin-1 type I repeat-like (TSRL) protein, identifying its tyrosine-rich T3 subunit as the core mediator for coating formation. The fabricated T3 coatings exhibited strong wet adsorption stability, biocompatibility, and intrinsic antioxidant activity. Mechanistically, T3 self-assembly is driven by favorable enthalpy, initiating with nanosphere aggregation and forming hierarchical fishnet-like microstructures. Molecular dynamics simulations revealed that, unlike the rapid collisions of T1 subunit, the slower diffusion of T3 enables precise orientation and pairing, leading to a marked increase in inter-residue contacts dominated by cation-π interactions between lysine and tyrosine residues, alongside π-π stacking. Mutant studies confirm that disrupting these interactions impairs both self-assembly and interfacial adsorption, establishing positioned tyrosine residues as molecular stickers. Together, these findings establish a tyrosine-mediated, non-Dopa marine adsorption paradigm and highlight the T3 protein as a promising biomaterial platform for tissue engineering and antioxidant biomedical applications. STATEMENT OF SIGNIFICANCE: This work reports a tyrosine-driven, Dopa-independent wet adsorption paradigm in marine biological systems, fundamentally expanding the current understanding of underwater adsorption mechanisms. The discovery that precisely positioned tyrosine residues can orchestrate hierarchical self-assembly through specific π-π and cation-π interactions establishes a new conceptual framework for designing bioinspired coatings. Beyond its fundamental implications, this system offers a versatile combination of robust wet adsorption and inherent biocompatibility, addressing a critical challenge in biomedical adhesive development. Moreover, the intrinsic reactive oxygen species (ROS)-scavenging capacity positions this protein-based platform as a multifunctional biomaterial with promising applications in wound healing, tissue engineering, and antioxidant therapeutics.

Along with the rising interest in regenerative medicine and tissue engineering comes the necessity to gain a deeper understanding of the underlying nature behind the mechanical responses of various soft tissues. This study investigates the differences in mechanical responses of the aorta and pulmonary artery, both of which share similar trilayered structures, by examining how their microstructural architectures influence their response to traction forces. As such, two-photon microscopy was used to visualize elastin and collagen fibers, via two-photon excited autofluorescence and second-harmonic generation respectively, during a mode I tensile fracture test on trouser-shaped specimens harvested from the aorta and pulmonary artery. The tensile tests revealed that while the aorta exhibited significantly higher low-strain elasticity compared to the pulmonary artery (aorta: 184.9 ± 37.4 kPa, pulmonary artery: 25.9 ± 6.0 kPa), both tissues required comparable forces for fracture propagation under mode I fracture (aorta: 7.6 ± 3.4 N, pulmonary artery: 6.3 ± 4.5 N). In this study, the possible reasons behind these mechanical disparities are discussed based on the microscopic images depicting the specimen's histologic structural deformation throughout the tensile test. Elastic responses from the aorta and pulmonary artery were discussed using static images of the elastin and collagen networks taken at a fixed interval during the tensile test. Moreover, this study presents the first successful acquisition of a microscopic video capturing the microstructural failure dynamics during arterial fracture, which served as a basis for discussion on the fracture properties of the aorta and pulmonary artery under mode I loading. These findings offer insights into fracture propagation mechanisms in arteries and underscore the importance of microstructural analysis for elucidating soft tissue biomechanics. STATEMENT OF SIGNIFICANCE: An artery's biomechanical response is essential for its physiological function and is influenced by the vessel's microstructure. While prior studies have focused on the elastic response of the aorta alone, this study examines both elastic and fracture behavior in the aorta and pulmonary artery. Microscopic image sequences capturing elastic and plastic deformation were acquired in both vessels, revealing microstructural differences leading to distinct biomechanical responses. From an engineering perspective, the results show that differences in elastin and collagen organization lead to artery-specific biomechanical properties, indicating that biomechanical models should incorporate vessel-specific structure rather than assuming uniform behavior. Clinically, these differences are relevant for vascular graft design, where matching both mechanical response and structural characteristics may improve performance and durability.

Tendon is critical for musculoskeletal function as it transfers forces generated by muscle to bone and stores energy during movement. Impaired mechanical function in tendon limits mobility and results from fatigue-induced damage progression that outpaces the restorative processes maintaining tissue health, a phenomenon we term mechanopathology. Early and non-invasive detection of tendon mechanopathologies is vital to prevent further damage but is lacking in the clinical space. Here, we evaluate the ability of diffusion tensor magnetic resonance imaging (DT-MRI) to detect mechanical fatigue damage in tendon and validate our findings using histologic assessments of collagen fiber microstructure and molecular structure. We found that fatigue-induced changes in DT-MRI metrics of tendon are spatially heterogeneous and correspond to regions with damaged collagen fiber microstructure. While secondary structures of collagen molecules were damaged by fatigue loading, they do not spatially correspond to fatigue-induced changes in DT-MRI metrics. Fatigue-induced changes in DT-MRI metrics can be partially explained by quantitative metrics of post-fatigue collagen fiber microstructure, estimating the limit of detection of DT-MRI metrics to fatigue-induced damage in tendon. Our findings indicate that DT-MRI metrics are sensitive to fatigue-induced local damage in tendon, supporting the use of DT-MRI as a non-invasive tool to detect tendon mechanopathologies and motivating future work toward clinical translation. STATEMENT OF SIGNIFICANCE: Non-invasive imaging techniques capable of detecting fatigue-induced damage in tendon are lacking in the clinical practice. Diffusion Tensor MRI (DT-MRI) is a non-invasive imaging technique that is sensitive to tissue microstructure, but its sensitivity to detect fatigue-induced damage in tendon - and other connective soft tissues - has not been evaluated. Here, we show that DT-MRI can identify local damage to the collagen fiber microstructure of tendon and establish the detection limits of 9.4 tesla DT-MRI metrics to such damage. Collectively, our findings support DT-MRI as a noninvasive tool for detecting fatigue-induced damage in tendon, and potentially other soft connective tissues, warranting further development to facilitate clinical translation.

Myocardial infarction (MI) often leads to adverse ventricular remodeling, a major precursor to heart failure, while current clinical approaches remain limited in effectively promoting myocardial regeneration and suppressing fibrosis. To address these challenges, we developed an injectable, smart-responsive hydrogel integrated with catalytic nanozyme and conductive components for synergistic MI repair. The hydrogel is constructed using phenylboronic acid-modified oxidized hyaluronic acid (OHA-PBA) and dopamine-grafted gelatin (GelDA) as the backbone, cross-linked via dynamic Schiff base and boronate ester bonds, conferring rapid self-healing and specific MI microenvironment-responsive properties. This biomimetic network not only replicates the structure and function of the native extracellular matrix but also responds specifically to the acidic and highly reactive oxygen species (ROS) microenvironment within the infarcted zone, enabling on-demand drug release. Incorporated into the hydrogel are black phosphorus nanosheets (BP Ns) to restore electrical conductivity, and puerarin-loaded honeycomb-like manganese dioxide nanozymes (PHMP NPs) that act as both ROS scavengers and in situ oxygen generators. Together, these components work synergistically to promote angiogenesis, alleviate local hypoxia, and reestablish blood and oxygen supply to the ischemic tissue. This integrated platform thus concurrently delivers mechanical support, restores electrical signaling, alleviates hypoxia, and combines antioxidant, anti-inflammatory, pro-angiogenic, and anti-fibrotic capabilities, offering a comprehensive multi-target therapeutic strategy for MI. Both in vitro and in vivo evaluations demonstrate that the developed hydrogel can effectively inhibit pathological ventricular remodeling, enhance vascularization, and modulate inflammatory responses, with histopathological and transcriptomic analyses further confirming these therapeutic effects, thereby significantly promoting the recovery of cardiac functions and offering a promising and advanced therapeutic strategy for MI treatment. STATEMENT OF SIGNIFICANCE: This work presents an injectable hydrogel platform that uniquely integrates electrical conductivity, catalytic oxygen generation, and smart microenvironment responsiveness for myocardial infarction (MI) therapy. Its significance lies in overcoming the limitation of current single-target approaches by enabling a synergistic multi-functional therapy. The system simultaneously restores electrical conduction, scavenges reactive oxygen species, alleviates hypoxia, and inhibits fibrosis within the infarcted heart. This integrated biomaterial strategy establishes a new paradigm for addressing the complex pathophysiology of MI, offering broad interest to researchers in biomaterials science, cardiac tissue engineering, and regenerative medicine.

The spatial organisation of mechanical cues is increasingly recognised as a key regulator of tissue development and disease, yet in vitro systems capable of replicating such environments remain limited. Fibroblast migration and the fibroblast-to-myofibroblast transition, which affect scar formation, are examples of mechanisms affected by mechanical cues. We report a photolithographic platform that enables precise, spatial patterning of the Young's modulus of gelatin methacryloyl (GelMA) hydrogels, using a ruthenium/sodium persulfate (SPS) photoinitiation system. By altering light intensity, we achieved Young's modulus tunability between 4 kPa and 46 kPa in non-patterned gels. By displaying a binary light intensity pattern over the gel, the Young's modulus could be switched from 10 kPa to 45 kPa, representing healthy and fibrotic Young's moduli, over a distance of ∼20 μm (2.3MPa·mm⁻¹). This system could also generate relatively linear Young's modulus gradients that are more physiologically relevant, ∼10 kPa⋅mm-1. Non-patterned and binary-patterned gels confirmed that increasing the Young's modulus drives the fibroblast-to-myofibroblast transition, observed by significantly greater cell volumes and α-smooth muscle actin (α-SMA) stress fibre formation, from encapsulated cardiac fibroblasts after 7 days. In gradient-patterned gels, fibroblasts exhibited a progressive, modulus-dependent increase in both cell volume and α-SMA stress fibre formation, alongside expressing a durotactic response, moving from healthy to fibrotic environments, and also aligning themselves between ±45 degrees to the Young's modulus gradient. Beyond cardiac fibrosis, this versatile platform enables rapid generation of biologically relevant mechanical landscapes for diverse mechanobiological applications, bridging the gap between simplified, mechanically uniform models and the heterogeneous microenvironments of native tissues. STATEMENT OF SIGNIFICANCE: This study developed a platform for spatially controlling the Young's modulus of GelMA using a digital light projection system. Using this system, a change in Young's modulus from 10 kPa to 45 kPa was achieved with a resolution of 20 µm. Natural Young's modulus gradients observed in tissues (∼10 kPa·mm⁻¹) can also be achieved. The fibroblast-to-myofibroblast transition was controlled spatially in the patterned gels, evidenced by changes in cell volume and α-SMA fibrillation. Fibroblasts demonstrated alignment and migration to the Young's modulus gradient. Our photopatterning system demonstrates ease of pattern/gradient definition with adaptability to a diverse range of systems, highlighting the impact of mechanical properties on cardiac scar formation, offering avenues for studying these effects.

The repair of soft tissue defects remains a leading clinical challenge for patients with active lifestyles, unintentional falls and injuries, cancer, and age-related diseases. Tissue engineering and 3D printing have been developed over the last decades as strategies to create personalized tissue mimics by precisely depositing biomaterials and cells to fabricate static constructs. However, long-term clinical solutions call for increasing the complexity of engineered models to incorporate bioactive processes that mimic the dynamic nature of human tissues. 4D printing has therefore become a growing strategy for building soft tissue constructs that exert function with time. The critical challenge lies in balancing biologically relevant tissue-specific function with programmable material capabilities in response to environmental stimuli. This review highlights the technological advancements that have improved progress in soft tissue engineering to build complex skin, cardiovascular, nerve, skeletal muscle, and connective tissue constructs. We first discuss mechanisms for 4D material actuation through external stimuli, which, when combined with advanced additive manufacturing tools, can assemble and program responsive tissue mimics. We next address progress in engineering functional soft tissues, which are characterized by tissue type, and discuss their limitations. Finally, the challenges associated with the fabrication of next generation 4D printed soft tissues are defined, and emerging frontiers are highlighted. STATEMENT OF SIGNIFICANCE: Soft tissue regeneration remains a clinical reconstructive challenge due to the hierarchical nature and intricate mechanics of native tissue. While 3D printing is an effective strategy for short-term healing outcomes, most tissues in the human body rely on dynamic properties to support normal physiological function. 4D printing strategies offer improvements in complexity to embed tissue-specific function into bioprinted constructs. Many existing reviews thoroughly cover 4D printing technologies and stimuli; however, their applications in soft tissue engineering toward prototyping functional tissue mimics remain underexplored. This review explores programmable stimuli for 4D printed soft tissues, advancements and limitations in function classified by soft tissue type, and insights and strategies for future challenges to work toward 4D printed functional, engineered soft tissues.