Bioactive Materials

Chronic wound healing is often impaired in conditions such as metabolic syndrome, requiring effective therapeutic interventions to promote tissue regeneration and repair. In this study, we evaluated the wound healing potential of petroleum jelly (P Jelly)-based bioactive glass ointments (PBGCu) with varying copper concentrations (0, 1, and 3 wt%) in both in vitro and in vivo models of wound healing. PBGCu formulations demonstrated high biocompatibility with human dermal fibroblasts (HDF) and human umbilical vein endothelial cells (HUVEC). Additionally, PBGCu ointments exhibited strong antibacterial activity against Staphylococcus aureus, suggesting their utility for the care of chronic wounds. In both metabolic syndrome mouse and pig models, PBGCu3-treated wounds showed significantly faster wound closure, enhanced epithelial regeneration, and increased dermal thickness compared to saline and P Jelly controls. Histological analysis also revealed 50% increased vascularization (p < 0.0001) and a 90% reduction in scar formation (p < 0.0001) in PBGCu3-treated wounds. These findings show that PBGCu formulations, especially at 3 wt% copper concentration, significantly improve wound healing by promoting epithelial regeneration, dermal tissue formation, and vascularization, while also offering antibacterial protection. The sustained Cu2+ ions release from PBGCu ointments provides long-term support for tissue regeneration, positioning this ointment composition as a promising therapeutic tool for chronic wound management. Future studies will focus on elucidating the underlying mechanisms and evaluating the therapeutic efficacy of PBGCu formulations in infected wounds. HighlightsO_LIDeveloped a Petroleum Jelly-based copper-doped bioactive glass ointment (PBGCu) enabling sustained and controlled Cu{superscript 2} ion release. C_LIO_LIPBGCu significantly accelerated wound closure and improved epithelial and dermal tissue regeneration. C_LIO_LIPBGCu enhanced hair follicle regeneration and tissue remodeling in full-thickness wounds. C_LIO_LIValidated therapeutic efficacy in both mouse and pig models that support translational relevance. C_LIO_LIOffers a simple, low-cost, and clinically adaptable topical formulation for metabolic syndrome-related wound complications. C_LI

Traumatic cranial defects often involve concurrent loss of soft and hard tissues and can progress to chronic defects due to delayed healing associated with infection or other co-morbidities. Despite autologous reconstruction remaining the clinical standard, it requires staged procedures using heterogeneous tissues, increasing operative time, costs, and surgical risks. Moreover, current tissue engineering approaches focus on single tissues or acute tissue defect models, limiting their clinical applications. Herein, we describe an acellular, material-driven 3D-printed composite scaffold designed to regenerate both bone and skin within composite cranial defects. The scaffold integrates controlled copper ion release from both organic and inorganic components with 3D-printed citrate polymer and citrate polymer-ceramic composites. Integrated thermoresponsive citrate-based hydrogels further enable spatially defined dermoconductive and osteoconductive properties, supporting a one-step surgical approach. At 12 weeks post-implantation, our scaffold enhanced keratinocyte organization, collagen deposition, and defect coverage with mature bone, achieving histological outcomes comparable to autografts. Furthermore, the system suppressed bacterial burden. Thus, this acellular platform represents a clinically promising synchronized strategy to address the complex demands of traumatic craniofacial composite defects.

Disruption of the wound healing cascade can result in pathological outcomes, including fibrosis due to myofibroblast-mediated contraction and collagen deposition. Despite the clinical significance, effective treatments for fibrosis remain limited as current therapies often show inconsistent efficacy, adverse effects, and patient discomfort. Combinatorial therapeutic strategies integrating biomaterial scaffolds with gene delivery have shown promise in regenerative healing. MicroRNAs (miRNAs) are key regulators of fibrotic signalling in cells, including fibroblasts and myofibroblasts. Specifically, miRNA-29b is notable for downregulating pro-fibrotic genes, including collagen type I, reducing ECM accumulation, and limiting fibroblast/myofibroblast overactivation. In this context, the present work develops a collagen-GAG (CG) scaffold platform for delivery of miRNA-29b complexed GET nanoparticles to inhibit fibrosis. Initially, bioinformatic analysis of miRNA-29b validated its involvement in ECM-associated pathways and processes, followed by successful nanoparticle internationalisation in primary dermal fibroblasts. The anti-fibrotic efficacy of the optimised miRNA-29b nanoparticles was subsequently demonstrated by significant reductions in collagen deposition and -SMA expression, both key indicators of myofibroblast differentiation and fibrosis. The optimised miRNA-29b formulation was then incorporated into 3D porous collagen-GAG (CG) scaffolds, which modulated fibrotic gene expression while preserving scaffold structure conducive to fibroblast/myofibroblast infiltration and proliferation. Finally, functional outcomes of seeded TGF-{beta}-stimulated fibroblasts, including reduced matrix contraction, -SMA expression, and ECM deposition, were comparable to those observed in non-fibrotic conditions, thereby confirming the therapeutic potential of scaffold-mediated miRNA-29b delivery. Together, these findings demonstrate that scaffold-mediated miRNA-29b delivery represents a promising anti-fibrotic strategy for wound healing by mitigating myofibroblast activation, limiting matrix contraction, and preventing pathological ECM accumulation.

Chronic diabetic wounds resist healing due to impaired angiogenesis, stalled cellular migration, and persistent inflammation, a challenge further compounded by the rapid degradation of therapeutic growth factors in the proteolytic wound bed. To overcome this, Traditional Chinese Medicine (TCM) compounds are employed not as standalone drugs, but as biomolecular stimuli to precondition the secretome of Wharton's Jelly-derived mesenchymal stem cells (WJMSCs). To overcome these critical translational barriers, this study engineers a core-shell coaxial electrospun nanofibrous scaffold (polyvinyl alcohol core/gelatin shell) designed for the stabilizing and sustained dual-delivery of biologics. We introduce a novel synergistic payload with WJMSCs conditioned medium (WJMSCs-CM) uniquely primed by two specific chinese herbal compounds, Astragaloside IV (AS-IV) and Formononetin (FMN). This core-shell architecture provides native-like contact guidance for cells while converting conventional burst release into a sustained, weeks-long elution. In vitro, this functionalized scaffold restores Akt/eNOS signaling, rescues cellular viability, and promotes robust tube formation in high-glucose-stressed fibroblasts and endothelial cells. In vivo, within an STZ-induced diabetic rat model, the application of this WJMSCs-CM-loaded coaxial scaffold actively inhibits early inflammation and comprehensively accelerates healing, driving near-complete wound closure (98.2 by day 21), mature collagen deposition, and hair follicle neogenesis. Ultimately, this bio-instructive platform successfully integrates physical structural cues with sustained biochemical signaling, offering a potent, multifaceted strategy for chronic wound regeneration.

Spinal metastases often occur secondary to breast, lung and prostate cancer and lead to instability, pain and poor quality of life. Standard care for spine metastases includes a multidisciplinary approach with surgery playing a major role in tumor resection, stabilization and decompression. Surgical resection with adjuvant is an effective treatment, yet it is often accompanied by tumor recurrence from residual disease. Furthermore, acrylic cements applied to defect sites provide stability, but they do not promote bone repair and can become destabilized during recurrence events. Developing new tools to stabilize defect sites, promote bone repair and locally deliver therapeutics may circumvent these limitations. We have previously developed mechanically competent 3D printed lactide/mineral scaffolds conducive to bone repair in vivo. We have also developed 3D printed nanoporous scaffolds conducive to both bone repair and chemotherapeutic delivery. Here, we set out to assess doxorubicin and cisplatin uptake and release rates and efficacy of drug delivery in 2D and custom physiological 3D cultures of two human cancer cell lines associated with metastases, MDA-MB-231 (human breast) and C42B (human prostate). Composite scaffolds had a compressive modulus close to trabecular bone, and could sustainably and effectively release doxorubicin and cisplatin as measured against both breast and prostate cell lines in 2D and 3D custom physiological metastases models. As a proof-of-concept, doxorubicin loaded composite scaffolds were implanted into rat caudal vertebrae following MDA-MB-231 xenograft resection. Following 6 weeks of implantation, no adverse events were noted and microCT analysis revealed boney integration of the construct. Taken together, these data indicate that our composite scaffolds may be an appropriate alternate therapy to stabilize bone defects, promote bone repair and effectively inhibit cancer recurrence post-tumor resection. Future work will test composite scaffolds using in vivo bone metastases models.

Tympanic membrane perforations remain a common clinical problem, and although surgical intervention through tympanoplasty achieves high success rates, it is associated with donor-site morbidity, surgical complexity and limited restoration of the native radial and circumferential collagen architecture. In this study, 3D extrusion printing was utilized to create an active scaffold and attempt to promote collagen organization through shear-mediated structural alignment. An alginate-carboxymethyl cellulose (CMC) hydrogel with bovine SIS-dECM was prepared and investigated for its suitability as a bioink alternative to tympanoplasty grafts. The physiochemical, rheological and printability characteristics of the hydrogel were assessed. Successful decellularization was confirmed by histological analysis. The incorporation of the SIS-dECM into the hydrogel led to increased swelling, lower apparent viscosity, yield stress and flow stress while maintaining favourable printability and filament stability. Polarized optical microscopy was also used to study the influence of printing speed on the alignment of collagen to mimic the native tympanic membrane radial collagen architecture. Compared with the cast controls, the printed samples presented stronger birefringence signals. Biological evaluation demonstrated that the 15% dECM hydrogel exhibited the highest live cell area percentage and live/dead ratio after 48 h. In addition, the chick chorioallantoic membrane assay demonstrated that the dECM-containing hydrogels improved vascular density. The findings establish a printable, biologically active dECM bioink capable of generating bulk collagen organization through extrusion printing as a platform for tympanic membrane regeneration.

Articular cartilage damage often progresses to osteoarthritis (OA), a degenerative joint disease characterized by chronic pain, limited mobility, and reduced quality of life. Tissue engineering approaches using poly (ethylene glycol) (PEG)-based hydrogels offer tunable mechanical properties and bioactive functionalization, yet the influence of surface charge on cartilage regeneration remains underexplored. Moreover, recombinant fibroblast growth factor 18 (FGF18) has successfully improved cartilage tissue thickness in clinical trials, but required high dosages and recurring injections may limit compliance. Here, we developed a granular microgel-based platform with bioorthogonally tethered FGF18 to evaluate the interplay of microgel surface charge and growth factor presentation on chondrogenesis. Azide groups were incorporated onto the microgel surfaces to enable site specific FGF18 conjugation across microgel scaffolds with distinct surface charges. When seeded with mesenchymal stromal cells, microgel scaffolds functionalized with FGF18 outperformed their unmodified counterparts, evidenced by higher GAG content, collagen content, and compressive modulus. In a murine microfracture model, anionic and zwitterionic microgel scaffolds tethered with FGF18 increased cartilage regeneration compared to nonionic microgels. We detected increased collagen II content within defects treated with tethered FGF18 microgel scaffolds. This work demonstrates the role of surface charge and growth factor presentation in directing cell behavior and tissue repair, advancing the design of biomaterials for cartilage regeneration. HIGHLIGHTSO_LICovalent tethering of FGF18 to microgel surface enables localized bioactivity C_LIO_LIFGF18 tethered microgel scaffolds enhance extracellular matrix deposition and chondrogenic differentiation of murine mesenchymal stromal cells in vitro C_LIO_LILocalized FGF18 presentation improves cartilage tissue formation and mechanical properties in vivo, with anionic and zwitterionic microgel scaffolds outperforming nonionic scaffolds C_LIO_LIFGF18 presentation is a more potent stimulus than microgel surface charge for cartilage regeneration C_LI

Chronic diabetic wounds remain a major clinical challenge because current therapies address infection or supplement growth factors without correcting the cellular dysfunction that prevents regeneration. We identify pathological glycocalyx thickening in diabetic dermal fibroblasts (DDFs) as a driver of elevated caspase 3, 8, and 9 expression and heightened apoptosis -- deficits that stall wound repair. Cleavage of sialic acid residues by neuraminidase (NMase) reverses this dysfunction, restoring fibroblast migration, proliferation, and contractility. We engineer a photo-crosslinked hybrid hydrogel combining methacrylated gelatin (GelMA) with high-molecular-weight methacrylated chitosan (HMW ChMA). ChMA increases storage modulus 8-12-fold, reduces pore size, and confers antibacterial activity against gram-positive and gram-negative bacteria, addressing infection susceptibility. The fortified HMW hybrid (HMWH) network enables sustained, localized NMase delivery that outperforms GelMA alone in resisting degradation and controlling release kinetics. NMase-loaded HMWH (N-HMWH) gels enhance DDF proliferation and migration in vitro, correlating with reduced focal adhesion size and increased turnover. In a diabetic rat model, N-HMWH patches achieve superior wound closure, outperforming EGF therapy, with robust epidermal regeneration, neovascularization, and collagen deposition. This work establishes glycocalyx-targeting hydrogels as a new class of wound therapeutics addressing the root cause of diabetic fibroblast failure, not just compensating with growth factors.

Adult skin normally resolves injury through rapid closure and fibrotic matrix deposition, often at the cost of permanent appendage loss. We tested whether spatially controlled microtrauma could instead serve as a regenerative entry point when paired with temporally coordinated molecular cues. We engineered a hierarchical extracellular-matrix-based microneedle patch that combines rapid local availability of verteporfin, an inhibitor of YAP-associated mechanotransduction, with sustained retinoic-acid delivery to support follicle-regenerative signalling. The microneedle interface was evaluated in full-thickness rabbit ear wounds, which are prone to hypertrophic scarring, and in Bama miniature-pig wounds, whose skin architecture more closely resembles human skin. Across both models, staged dual-cue treatment accelerated wound closure, reduced collagen-dense scar formation and promoted the appearance of hair-bearing tissue and histologically identifiable follicular structures. These findings support a trauma-guided regeneration framework in which controlled microinjury is used not only for delivery but also to open a transient repair niche that can be molecularly redirected toward appendage-bearing skin restoration. ImportanceMicroneedles are generally treated as minimally invasive delivery devices. Here, the microinjury itself is incorporated into the therapeutic design. The study provides cross-species proof of concept that a patterned injury interface, combined with staged anti-fibrotic and pro-regenerative signalling, can shift wound repair away from fibrotic closure and toward hair-follicle-containing skin. This concise preprint reports the central concept and the rabbit and porcine evidence supporting it; expanded mechanistic and source datasets will be reported separately.

Damage to the skin by trauma, burns, or surgical procedures often results in uncontrolled bleeding, which remains a leading cause of preventable death following injury, yet most conventional hemostatic materials are engineered solely to arrest bleeding and often adhere strongly to the wound bed, causing pain, rebleeding, and disruption of newly formed tissue upon removal. Here, we report a DNA hydrogel that structurally mimics neutrophil extracellular traps (NETs) and is crosslinked using a bioactive small molecule with potent autophagy-inducing, cardioprotective, anti-inflammatory, antioxidant, and mitochondria-protective properties, integrating rapid hemostasis with active support for tissue regeneration in a single biomaterial. The DNA network provides an intrinsically biocompatible, biodegradable scaffold capable of recruiting platelets and erythrocytes to achieve rapid clot formation, while the bioactive crosslinker is released as the network degrades, delivering a sustained cytoprotective and anti-inflammatory stimulus directly at the wound site. The hydrogel was characterised physiochemically and evaluated for cytocompatibility, hemolytic potential, hemostatic efficacy, and wound-healing performance in a murine model. Results demonstrate that the bioactive-crosslinked DNA hydrogel achieves rapid, effective hemostasis, while accelerating wound closure and supporting regenerative tissue remodelling. This dual-function platform offers a promising strategy for next-generation wound-care biomaterials that unite immediate bleeding control with accelerated, natural tissue healing.

Vocal fold (VF) fibrosis is a major cause of persistent dysphonia due to excessive extracellular matrix deposition and tissue stiffening that disrupt normal vocal fold vibration. Current treatment approaches are limited by the need for repeated local injections and inadequate long-term therapeutic control. Pirfenidone (PFD), an FDA-approved antifibrotic agent, has demonstrated potential for reducing fibrosis; however, its short half-life and systemic adverse effects limit conventional administration strategies. In this study, we developed a sustained and near-infrared (NIR)-responsive local delivery platform by integrating PFD-loaded poly(lactic-co-glycolic acid) (PLGA) nanoparticles into biodegradable PLGA implants for dose-controllable antifibrotic delivery. PFD-loaded PLGA nanoparticles were fabricated using an oil-in-water emulsion solvent evaporation method and characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Nanoparticles with small, medium, and large hydrodynamic diameters were generated to evaluate the effect of particle size on release behavior. Gold nanorods (AuNRs) were incorporated to enable photothermal NIR-triggered release enhancement. The nanoparticles were subsequently loaded into non-porous PLGA (90:10) implants and evaluated for long-term in vitro release under physiological conditions with and without pulsed 1064 nm laser irradiation. The nanoparticle-loaded implants demonstrated sustained PFD release for over 190 days with minimal initial burst release (<2.5%). NIR irradiation enhanced PFD release compared with non-irradiated controls across all nanoparticle sizes. Smaller nanoparticles produced greater cumulative release than medium and large nanoparticles due to shorter diffusion pathways and larger surface-area-to-volume ratios. Prior to implant fracture, cumulative PFD release reached approximately 20.2%, 14.8%, and 12.3% of total loading for small, medium, and large nanoparticle groups under 2-min irradiation conditions, respectively. Dialysis membrane studies further demonstrated that the PLGA capsule acted as an additional diffusion barrier that substantially prolonged release compared with nanoparticles alone. Overall, this study demonstrates a hybrid nanoparticle-in-implant strategy capable of providing sustained and irradiation-enhanced local PFD delivery with tunable release characteristics. These findings support the potential of biodegradable, dose-controllable implant systems for long-term management of vocal fold fibrosis while reducing the need for repeated interventions.

Precise control of growth factor delivery remains a challenge for directing stem cell differentiation in three-dimensional (3D) engineered tissues. In this study, engineered cell-like vesicles are used as programmable microenvironments to enable sustained and localized delivery of growth factors within visible-light-crosslinked GelMA hydrogels. Giant unilamellar vesicles (GUV) loaded with FGF-2 and TGF-{beta}3 were incorporated into bioinks with BM-MSC to drive keratocyte differentiation without repeated soluble growth factor supplementation. ELISA measurements confirmed the removal of non-encapsulated growth factors and the release of the vesicle cargo following induced vesicle rupture. Fluorescence monitoring showed a progressive reduction in detectable FGF-2- and TGF-{beta}3-loaded GUV during culture, while droplet-scale analysis demonstrated the co-deposition of cells and vesicles after printing. After 14 days of differentiation, differentiated cells expressed ALDH1A1, ALDH3A1, lumican, keratocan, and collagen I without induction of -SMA. Interestingly, keratocyte-associated differentiation was retained after drop-on-demand bioprinting, confirmed by qPCR analysis. These findings establish growth factor-loaded vesicles as bioprintable instructive niches capable of supporting localized keratocyte differentiation within 3D corneal constructs.

Ex vivo airway engineering approaches such as 3D bioprinting offer a promising strategy for generating functional airway replacements, but the fabrication of hollow, patient-specific proximal airway constructs using translationally relevant bioinks remains challenging. This study describes the development of biocompatible, polymer-blended human airway-derived decellularized extracellular matrix (AW-dECM) bioinks for engineering structurally and mechanically relevant airway tissues. An optimal formulation consisting of 30 mg/mL AW-dECM and nanofibrillar cellulose alginate conjugated to RGD supported the bioprinting of simple and complex hollow airway structures with mechanical properties comparable to native airways ([~]8-10 kPa). The bioinks also promoted primary human airway epithelial cell viability, adhesion, and differentiation into mucociliary and secretory phenotypes during 28 days of air-liquid interface culture. Furthermore, subcutaneous implantation in immunocompetent rats demonstrated excellent biodegradative stability and overall biocompatibility over 30 days. Collectively, these findings establish a foundation for improved physiological airway models and future tissue-engineered airway replacements.

Avascular meniscus tears exhibit minimal intrinsic healing and often progress to joint degeneration due to restricted biological repair capacity and inadequate restoration of tissue-level structure and function. Here, we report a hydrophilic polydopamine (hPDA) fueled bioglue platform that overcomes the solubility limitations of conventional polydopamine (PDA) and enables functional repair of avascular meniscus injuries. Water-soluble hPDA was synthesized via controlled depolymerization and recrystallization, yielding monomeric and oligomeric species rich in catechol, amine, and hydroxyl functionalities. Incorporation of hPDA into fibrin bioglues markedly enhanced mechanical performance, producing 520-525% increases in lap-shear modulus, 165-190% increases in adhesive strength, and a 160% increase in compressive modulus relative to fibrin controls, while degradation was markedly attenuated over 14 days. hPDA exhibited excellent cytocompatibility in both 2D and 3D cultures. In a bovine avascular meniscus explant model, hPDA fueled bioglues promoted tissue integration and aligned collagen remodeling, restoring interfacial mechanics with a 488% increase in tensile modulus and up to 150% higher pull-out strength after 6 weeks. These findings establish hPDA as a versatile bioadhesive building block with strong potential for repairing avascular meniscus tears and other mechanically demanding connective tissues. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC="FIGDIR/small/738365v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@1f376dborg.highwire.dtl.DTLVardef@10029feorg.highwire.dtl.DTLVardef@1c4f191org.highwire.dtl.DTLVardef@cfa2fe_HPS_FORMAT_FIGEXP M_FIG C_FIG

Artificial skin substitutes that simultaneously achieve mechanical robustness, regenerative bioactivity, and transplantation-scale tissue integration remain challenging to engineer. Here we report a mechanically adaptive bilayer artificial skin based on entanglement-mediated protein networks. By integrating protein chain entanglement, flexible molecular linkers, and photo-triggered intermolecular crosslinking, we establish a hierarchically organized protein matrix with enhanced toughness, structural adaptability, and regenerative compatibility. Spatial biofunctionalization further enables integration of an antibacterial Zn{superscript 2}-coordinated epidermal layer and a regenerative CLP-EGF-functionalized dermal layer within a unified construct. The engineered skin promotes cellular proliferation through PI3K-AKT-mTOR activation, exhibits sustained antibacterial activity, and supports large-area full-thickness skin replacement covering approximately 40% of the dorsal skin surface in mice. The construct further accelerates diabetic wound repair and extracellular matrix remodeling in vivo. These findings establish entanglement-mediated protein engineering as a strategy for mechanically adaptive regenerative biomaterials and provide a platform for transplantation-scale skin regeneration.

Collagen, a major component of the extracellular matrix, regulates cellular behaviors, such as adhesion, differentiation, and angiogenesis. These functions are mediated by interactions between specific amino acid motifs within the collagen triple-helical structure and collagen-binding biomolecules. These include cell-surface receptors, such as integrins, discoidin domain receptors (DDRs), and syndecans, a family of transmembrane heparan sulfate proteoglycans (HSPGs). Signals mediated by these receptors are integrated to regulate cell fate. However, native collagen simultaneously presents multiple receptor-binding motifs, making it difficult to isolate receptor-specific functions and to evaluate receptor crosstalk. Here, we introduce a composition-controlled artificial collagen matrix platform that enables independent tuning of multiple receptor-binding motifs within a constant triple-helical scaffold. This material was produced by disulfide crosslinking of chemically synthesized collagen-like triple-helical peptides, each bearing a single defined receptor-binding sequence. By varying the mixing ratios of these peptides before crosslinking, we systematically controlled the composition of receptor-binding motifs within the matrices. We applied this platform to nerve growth factor-dependent neuronal differentiation of PC12 cells, a process supported by collagen. Matrices containing only integrin-binding sequences were sufficient to support this differentiation. Incorporation of an HSPG-binding sequence had little additional effect, whereas incorporation of a DDR-binding sequence suppressed integrin-mediated differentiation and coincided with DDR phosphorylation. These results reveal opposing roles of collagen-binding integrins and DDRs in regulating PC12 cell differentiation. Composition-controlled artificial collagen provides a versatile matrix platform for dissecting functional crosstalk among collagen receptors.

Silk proteins, including sericin and fibroin, are natural biopolymers with broad applications in tissue engineering where angiogenesis plays an essential role. However, the pro-angiogenic effects of silk proteins with varying molecular weights (MWs) remain poorly understood. Here, silk proteins with MW distributions at 40-180 kDa or less than 25 kDa were obtained through alkaline hydrolysis to evaluate their effects on angiogenesis. Structurally, reducing MW induced a conformational transition in silk proteins, accompanied by a striking morphological shift in sericin from nanofibers to nanoparticles. Functionally, high-MW sericin (SSH) suppressed, whereas low-MW sericin (SSL) and both high- and low-MW silk fibroin (SFH/SFL) directly promoted endothelial angiogenic activity. Transcriptomic analysis revealed that angiogenesis-related genes such as Id1 and Smad6/9 may underlie the angiostatic effects of SSH. Notably, both SSH and SSL enhanced angiogenesis indirectly via macrophages; however, SSH induced mixed M1/M2-like polarization, while SSL preferentially drove an M2-like phenotype. In a subcutaneous implantation model, SSH promoted angiogenesis but yielded vessels with weak integrity and increased fibrosis, whereas SSL enhanced angiogenesis with improved vascular maturity and reduced fibrotic response. These findings elucidate how the MWs of silk proteins shape angiogenic behavior and highlight the importance of MW tailoring for optimized tissue engineering applications.

Engineering biomimetic tissues with dynamically evolving 3D architectures represents an important direction for next-generation tissue engineering, as it enables recapitulation of the continuous morphogenesis of native tissues during development and regeneration. Here, a self-actuating 4D cell-strand bioprinting platform is developed to engineer complex tissue architectures through autonomous cell contractile force (CCF)-driven morphing without requiring external stimuli. The platform integrates a mechanically compliant and self-softening base hydrogel with embedded high-density cell strands printed using a fast-degrading carrier bioink. During culture, the carrier bioink rapidly degrades while the encapsulated cells proliferate and establish connected cellular networks, generating localized contraction that drives programmable shape transformation. Through spatial patterning of embedded cell strands, constructs with diverse morphologies, including V-shaped, helical, folded, and tubular architectures, are generated via controllable self-actuated morphogenesis. The platform further enables engineering of cartilage-like and bone-like tissues with well-defined curvature configurations and mechanically robust tissue matrices. In addition, programmable multi-tissue engineering is demonstrated through fabrication of a muscle-tendon junction-mimicking construct containing spatially organized fibroblast and myoblast compartments. This self-actuating 4D bioprinting strategy enables highly programmable and directionally controlled morphogenesis using a simple construct design with low cell amount requirements, providing a versatile platform for engineering dynamic tissue architectures.

Introduction: Advanced biomaterials for regenerative medicine are increasingly expected to combine multifunctionality and compatibility with tissue-specific cellular processes. In this context, hydroxyapatite-based platforms modified through ionic substitution represent promising candidates, as they may integrate structural similarity to bone mineral with additional biological functionality and luminescent properties, enabling diagnostic applications and real-time monitoring. In this study, we evaluated whether silicate-phosphate substituted calcium hydroxyapatite Ca10(PO4)6-x(SiO4)x(OH)2 (where x = 1.5) co-doped with lithium(I), europium(III), and gadolinium(III) ions (Si-HAp-LEG) affects the osteogenic, chondrogenic, and adipogenic differentiation potential of human bone marrow stromal/stem cells (BMSCs). Methods: Human BMSCs were cultured under lineage-specific differentiation conditions in the presence of undoped silicate-substituted phosphate hydroxyapatite (abbr. as Si-HAp), which served as a control, and two distinct Si-HAp-LEG formulations differing in gadolinium(III) (Gd3+) as well as lithium (Li+) and europium(III) (Eu3+) ion concentrations: Si-HAp-LEG-221 (1 mol% Gd3+ ion) and Si-HAp-LEG-222 (2 mol% Gd3+ ion). Differentiation-associated phenotypic outcomes, including extracellular matrix formation and lipid accumulation, were evaluated using Safranin O, Alizarin Red, and Oil Red O staining. In parallel, biomaterial-induced molecular responses were characterized at the transcriptomic and protein levels using RT-qPCR for selected coding and non-coding RNAs and Western blot analysis for representative lineage-associated proteins. Results: Histochemical evaluation confirmed that, across all tested biomaterial groups, BMSCs retained the ability to form mineralized calcium deposits, proteoglycan-rich extracellular matrix, and intracellular lipid accumulation under osteogenic, chondrogenic, and adipogenic conditions, respectively. Quantitative staining analysis revealed no significant Si-HAp-LEG-dependent enhancement of terminal differentiation outcomes compared with undoped Si-HAp. In turn, the molecular response differed between biomaterials modifications. Si-HAp-LEG-222 induced the most prominent changes in transcriptional and post-transcriptional regulators, particularly within BMP/SMAD-associated pathways under osteogenic and chondrogenic conditions, underlying a potential link between gadolinium concentration and osteogenic lineage commitment. However, these transcriptomic responses were not mirrored by consistent changes at the protein level. The results suggest that silicate-phosphate substituted hydroxyapatite co-doped with Li+, Eu3+, and Gd3+ ions primarily affects the early regulatory pathways associated with BMSCs differentiation rather than enhancing their terminal maturation. Discussion: In conclusion, the collective data indicate that Li+, Eu3+, and Gd3+ ions LEG co-doping broadens the multifunctional potential of Si-HAp by introducing imaging-related properties while preserving its underlying pro-regenerative character. Li+, Eu3+, and Gd3+ ions co-doped LEG-substituted Si-HAp may therefore be considered a compatible biomaterial platform that maintains BMSC cellular plasticity and supports balanced, differentiation-dependent modulation of lineage-associated molecular responses.

ABSTRACTThe repair of large bone defects remains a major clinical challenge, in part due to inadequate vascularization and poor integration of graft materials. Tissue engineering strategies that recapitulate the developmental process of endochondral ossification, whereby a cartilage template remodels into bone, have shown significant potential in pre-clinical models of large bone defect healing. However, successfully scaling these approaches to clinically relevant sizes will require the development of strategies to support the rapid vascularization of the graft following implantation in vivo. Here, mechanically reinforced templates were first fabricated by integrating hypertrophic cartilage microtissues derived from human mesenchymal stem/stromal cells (MSCs) within an osteoconductive 3D-printed polycaprolactone (PCL) framework coated with nano-hydroxyapatite (nanoHA). In vitro the cartilage microtissues fused and generated an extracellular matrix rich in sulphated glycosaminoglycans and collagen. To prevascularize these constructs, vascular microtissues derived from a co-culture of endothelial cells and MSCs were incorporated into a central channel within the construct, which generated a microvascular network within the graft in vitro. Following subcutaneous implantation, hypertrophic cartilage templates with ( vascular-channel group) and without ( empty-channel group) this central vascularized channel supported endochondral bone formation. Quantitative microCT and histological analyses revealed significantly greater remaining bone in the empty-channel group, whereas the vascular-channel group supported enhanced vascularization and remodeling of the graft in vivo. These findings support the continued development and testing of a modular biofabrication strategy that combine self-organizing hypertrophic cartilage and vascular microtissues with osteoconductive 3D-printed architectures to generate scalable, prevascularised hypertrophic cartilage templates for endochondral bone repair. Key-words: spheroids, microtissues, hypertrophic cartilage, vascularization, endochondral ossification, bone tissue engineering.