Hierarchical Scaffolds Research Articles

Superomniphobic and Photoactive Surface Presents Antimicrobial Properties by Repelling and Killing Pathogens.

Healthcare-acquired infections place a significant burden on the cost and quality of patient care in hospitals. Reducing contamination on surfaces within healthcare environments is critical for halting the spread of these infections. Herein, we report a bifunctional─repel and kill─surface developed using photoactive TiO2 nanoparticles integrated into a hierarchical scaffold (OmniKill). To quantify the repellency of OmniKill, we developed a touch-based assay, capable of simulating the transfer of individual pathogens, multiple pathogens, or pathogen-latent fecal matter from hands to surfaces. OmniKill repels bacterial pathogens by at least 2.77-log (99.8%). The photoactive material within OmniKill further reduces the viability of transferred pathogens on the surface by an additional 2.43-log (99.6%) after 1 h of light exposure. The antipathogenic effects─repel and kill─remain robust under complex biological contaminates such as feces. These findings show the potential use of OmniKill in reducing the physical transmission of bacterial pathogens in healthcare settings.

Bioinspired scaffolds based on aligned polyurethane nanofibers mimic tendon and ligament fascicles.

Topographical factors of scaffolds play an important role in regulating cell functions. Although the effects of alignment topography and three-dimensional (3D) configuration of nanofibers as well as surface stiffness on cell behavior have been investigated, there are relatively few reports that attempt to understand the relationship between synergistic effects of these parameters and cell responses. Herein, the influence of biophysical and biomechanical cues of electrospun polyurethane (PU) scaffolds on mesenchymal stem cells (MSCs) activities was evaluated. To this aim, multiscale bundles were developed by rolling up the aligned electrospun mats mimicking the fascicles of tendons/ligaments and other similar tissues. Compared to mats, the 3D bundles not only maintained the desirable topographical features (i.e., fiber diameter, fiber orientation, and pore size), but also boosted tensile strength (∼40MPa), tensile strain (∼260%), and surface stiffness (∼1.75MPa). Alignment topography of nanofibers noticeably dictated cell elongation and a uniaxial orientation, resulting in tenogenic commitment of MSCs. MSCs seeded on the bundles expressed higher levels of tenogenic markers compared to mats. Moreover, the biomimetic bundle scaffolds improved synthesis of extracellular matrix components compared to mats. These results suggest that biophysical and biomechanical cues modulate cell-scaffold interactions, providing new insights into hierarchical scaffold design for further studies.

Hierarchical N-doped porous carbon scaffold Cu/Co-oxide with enhanced electrochemical sensing properties for the detection of glucose in beverages and ascorbic acid in vitamin C tablets

This research focuses on the development of a highly efficient electrocatalyst, CuxO/NPC@Co3O4/NPC-10–7, for detecting glucose and ascorbic acid. In a 0.1 M NaOH solution, the modified electrode exhibits a sensitivity of 3314.29 μA mM−1 cm−2 for glucose detection. The linear range for ascorbic acid sensing is 0.5 μM − 23.332 mM, with a detection limit as low as 0.24 μM. In a 0.1 M PBS solution, the linear range for ascorbic acid detection extends to 43.328 mM, which represents the best performance reported to date by chronoamperometry. Moreover, the electrode demonstrates high accuracy, with a recovery rate of 96.80 % − 103.60 % for glucose detection and a recovery rate of 95.25 % − 104.83 % for ascorbic acid detection. These results suggest that the CuxO/NPC@Co3O4/NPC-10–7 modified electrode shows significant potential for practical applications in food detection.

3D Printing of Bioactive Gel-like Double Emulsion into a Biocompatible Hierarchical Macroporous Self-Lubricating Scaffold for 3D Cell Culture.

The interconnected hierarchically porous structures are of key importance for potential applications as substrates for drug delivery, cell culture, and bioscaffolds, ensuring cell adhesion and sufficient diffusion of metabolites and nutrients. Here, encapsulation of a vitamin C-loaded gel-like double emulsion using a hydrophobic emulsifier and soy particles was performed to develop a bioactive bioink for 3D printing of highly porous scaffolds with enhanced cell biocompatibility. The produced double emulsions suggested a mechanical strength with the range of elastic moduli of soft tissues possessing a thixotropic feature and recoverable matrix. The outstanding flow behavior and viscoelasticity broaden the potential of gel-like double emulsion to engineer 3D scaffolds, in which 3D constructs showed a high level of porosity and excellent shape fidelity with antiwearing and self-lubricating properties. Investigation of cell viability and proliferation using fibroblasts (NIH-3T3) within vitamin C-loaded gel-like bioinks revealed that printed 3D scaffolds offered brilliant biocompatibility and cell adhesion. Compared to scaffolds without encapsulated vitamin C, 3D scaffolds containing vitamin C showed higher cell viability after 1 week of cell proliferation. This work represented a systematic investigation of hierarchical self-assembly in double emulsions and offered insights into mechanisms that control microstructure within supramolecular structures, which could be instructive for the design of advanced functional tissues.

Polysaccharide-Based Composite Hydrogel with Hierarchical Microstructure for Enhanced Vascularization and Skull Regeneration.

Critical-size skull defects caused by trauma, infection, and tumor resection raise great demands for efficient bone substitutes. Herein, a hybrid cross-linked hierarchical microporous hydrogel scaffold (PHCLS) was successfully assembled by a multistep procedure, which involved (i) the preparation of poly(lactic-co-glycolic)/nanohydroxyapatite (PLGA-HAP) porous microspheres, (ii) embedding the spheres in a solution of dopamine-modified hyaluronic acid and collagen I (Col I) and cross-linking via dopamine polyphenols binding to (i) Col I amino groups (via Michael addition) and (ii) PLGA-HAP (via calcium ion chelation). The introduction of PLGA-HAP not only improved the diversity of pore size and pore communication inside the matrix but also greatly enhanced the compressive strength (5.24-fold, 77.5 kPa) and degradation properties to construct a more stable mechanical structure. In particular, the PHCLS (200 mg, nHAP) promoted the proliferation, infiltration, and angiogenic differentiation of bone marrow mesenchymal stem cells in vitro, as well as significant ectopic angiogenesis and mineralization with a storage modulus enhancement of 2.5-fold after 30 days. Meanwhile, the appropriate matrix microenvironment initiated angiogenesis and early osteogenesis by accelerating endogenous stem cell recruitment in situ. Together, the PHCLS allowed substantial skull reconstruction in the rabbit cranial defect model, achieving 85.2% breaking load strength and 84.5% bone volume fractions in comparison to the natural cranium, 12 weeks after implantation. Overall, this study reveals that the hierarchical microporous hydrogel scaffold provides a promising strategy for skull defect treatment.

Biocompatible and bioactive PEG-Based resin development for additive manufacturing of hierarchical porous bone scaffolds

Bone diseases can often result in patient bone fragility. Different bone problems include low bone density, osteoporosis, and other bone diseases. Such bone diseases, ailments, and malfunctions often require complex and expensive treatments. In this study, we synthesized a new type of DLP resin for 3D printing purposes based on poly(ethylene glycol diacrylate) (PEGDA) and acrylic acid (AAc). In addition, using a porogen within the photopolymerizable resin allowed us to fabricate hierarchical interconnected porous structures. These structures combine the pores resulting from the CAD design with those obtained by the lixiviation of the porogen. Finally, bioactive particles were added to the mixture to increase the material's biocompatibility, thus proving the strategy's potential to include active compounds for particular purposes. Our results demonstrate that including the photoabsorber, Orange G, considerably increases the printing precision and resolution of the synthesized resin, making it possible to obtain printed parts with intricate and complex geometries with high accuracy and definition. Nano-hydroxyapatite (nHA) inclusion significantly increases the material's biocompatibility and mechanical stiffness (∼47 % increase, from 5.47 MPa to 8.02 MPa).

Coaxial 3D printing of hierarchical structured hydrogel scaffolds for on-demand repair of spinal cord injury.

After spinal cord injury (SCI), endogenous neural stem cells (NSCs) near the damaged site are activated, but few NSCs migrate to the injury epicenter and differentiate into neurons because of the harsh microenvironment. It has demonstrated that implantation of hydrogel scaffold loaded with multiple cues can enhance the function of endogenous NSCs. However, programming different cues on request remains a great challenge. Herein, a time-programmed linear hierarchical structure scaffold is developed for spinal cord injury recovery. The scaffold is obtained through coaxial 3D printing by encapsulating a dual-network hydrogel (composed of hyaluronic acid derivatives and N-cadherin modified sodium alginate, inner layer) into a temperature responsive gelatin/cellulose nanofiber hydrogel (Gel/CNF, outer layer). The reactive species scavenger, metalloporphyrin, loaded in the outer layer is released rapidly by the degradation of Gel/CNF, inhibiting the initial oxidative stress at lesion site to protect endogenous NSCs; while the inner hydrogel with appropriate mechanical support, linear topology structure and bioactive cues facilitates the migration and neuronal differentiation of NSCs at the later stage of SCI treatment, thereby promoting motor functional restorations in SCI rats. This study offers an innovative strategy for fabrication of multifunctional nerve regeneration scaffold, which has potential for clinical treatment of SCI. STATEMENT OF SIGNIFICANCE: Two major challenges facing the recovery from spinal cord injury (SCI) are the low viability of endogenous neural stem cells (NSCs) within the damaged microenvironment, as well as the difficulty of neuronal regeneration at the injured site. To address these issues, a spinal cord-like coaxial scaffold was fabricated with free radical scavenging agent metalloporphyrin Mn (III) tetrakis (4-benzoic acid) porphyrin and chemokine N-cadherin. The scaffold was constructed by 3D bioprinting for time-programmed protection and modulation of NSCs to effectively repair SCI. This 3D coaxially bioprinted biomimetic construct enables multi-factor on-demand repair and may be a promising therapeutic strategy for SCI.

Beta-TCP scaffolds with rationally designed macro-micro hierarchical structure improved angio/osteo-genesis capability for bone regeneration

The design of hierarchical porous structure in scaffolds is crucial for bone defect regenerative repair. However, bioceramic materials present a challenge in precisely constructing designed micropores owing to the limitation of forming process. To investigate micropore shape influences bone regeneration in bioceramic scaffolds with macropores, hierarchical porous scaffolds with interconnective macropores (~400 μm) and two types of micropores (spherical and fibrous) were prepared using a combination of direct ink writing (DIW) and template sacrifice methods. Compared to the scaffold with spherical micropores, the scaffold with highly interconnected fibrous micropores significantly improved cell adhesion and upregulated osteogenic and angiogenetic-related gene expression in mBMSCs and HUVECs, respectively. Furthermore, in vivo implantation experiments showed that hierarchical scaffolds with fibrous micropores accelerated the bone repair process significantly. This result can be attributed to the high interconnectivity of fibrous micropores, which promotes the transportation of nutrients and waste during bone regeneration. Our work demonstrates that hierarchical porous scaffold design, especially one with a fibrous micropore structure, is a promising strategy for improving the bone regeneration performance of bioceramic scaffolds.Graphical

Enhancement of Tendon-to-Bone Healing: Choose a Monophasic or Hierarchical Scaffold?

Background: To enhance the healing of tendon to bone, various biomimetically hierarchical scaffolds have been proposed. However, the fabrication of such scaffolds is complicated. Furthermore, the most significant result after a routine repair is loss of the transition zone between the tendon and bone, whose main components are similar to fibrocartilage. Purpose: To compare tendon-to-bone healing results in a rabbit model using a monophasic graft (decellularized fibrocartilage graft; DFCG) and hierarchical graft (decellularized tendon-to-bone complex; DTBC) that contain the native hierarchical enthesis. Study Design: Controlled laboratory study. Methods: DFCG and DTBC were harvested from allogenic rabbits. A rabbit model of a chronic rotator cuff tear was established, and 3 groups were assessed: direct repair or repair with DFCG or DTBC fixed between the tendon and bone. Hierarchical evaluations of the repaired tendon-to-bone interface were performed with regard to the tendon zone, transition zone, and bone zone using histological staining and micro–computed tomography scanning. Biomechanical analysis was performed to evaluate the general healing strength. Results: The healing results in the tendon zone exhibited no significant difference among the 3 groups at any time point. In the transition zone, the grade in the direct repair group was significantly lower than that in the DFCG and DTBC groups at 4 weeks, and the grade in the DFCG group was significantly lower than that in the DTBC group at this time point. However, any significant difference between the DFCG group and DTBC group could no longer be detected at 8 and 16 weeks, which was inconsistent with the results of the biomechanical analysis. Micro–computed tomography analysis showed no significant difference among the 3 groups with regard to bone mineral density at 16 weeks. Conclusion: A monophasic DFCG was able to achieve enhanced tendon-to-bone healing similar to that with hierarchical DTBC over the long term, with regard to both histological and biomechanical properties. Clinical Relevance: Fabrication of a monophasic scaffold instead of a hierarchical scaffold to promote regeneration and remodeling of a transition zone, which was mainly composed of fibrocartilaginous matrix between the tendon and bone, may be sufficient to enhance tendon-to-bone healing.

Fabrication of Polysaccharide-Based Coaxial Fibers Using Wet Spinning Processes and Their Protein Loading Properties

Fibers composed of polysaccharides are a promising candidate to be applied for biomaterials such as absorbable surgical sutures, textile fabrics, and hierarchical three-dimensional scaffolds. In this work, in order to fabricate biocompatible fibers with controlled-release abilities, the fabrication of coaxial fibers of calcium alginate (ALG-Ca) and polyion complexes (PICs) consisting of chitosan (CHI) and chondroitin sulfate C (CS), denoted as ALG-PIC fibers, by using a wet spinning process, and the evaluation of their molecular loading and release behavior were performed. The diameter and mechanical strength of the obtained ALG-PIC fibers increased with increasing concentrations of the CHI solution for PIC coatings. This indicated that higher concentrations of the CHI solution afforded a thicker PIC coating layer. Further, fluorescein isothiocyanate labeled-bovine serum albumin (FITC-BSA)-loaded ALG-PIC fibers were successfully prepared. The release behavior of FITC-BSA in the fibers exhibited a slower rate at the initial state than that in ALG-Ca, indicating that PIC coatings suppressed an initial burst release of the loading molecules. Accordingly, the fabricated coaxial fibers can be utilized as sustained-release drug carriers.

Ultrasound-driven electrical stimulation based on 3D hierarchical porous piezoelectric nanofiber-aerogel scaffold promotes bone defect repair

Electroactive scaffolds with three-dimension (3D) hierarchical porous structure have demonstrated immense potential in tissue repair and regeneration by providing an electrical microenvironment at bone defect sites. Herein, we designed a biodegradable nanofiber-aerogel scaffold with hierarchical porous structure and rehabilitated electrical microenvironment for accelerated bone regeneration. Incorporating piezoelectrical ZnO/polyhydroxybutyrate nanofibers and chitosan into three-dimensional porous structure, the nanofiber-aerogel scaffold with extracellular matrix (ECM)-like structure effectively facilitated adhesion, migration and recruitment of stem cells, which also rehabilitated electric microenvironment for accelerating osteogenic differentiation under controllable ultrasonic (US) stimulation. A series of biological experiments in vitro and in vivo had been performed to verify osteogenic performance of nanofiber-aerogel scaffolds. This work highlights the potential application of nanofiber-aerogel scaffold processing ECM-like structure and rehabilitating electrical microenvironment in the therapy of bone defects.

Bioinspired Hierarchical Carbon Structures as Potential Scaffolds for Wound Healing and Tissue Regeneration Applications.

Engineered bio-scaffolds for wound healing provide an attractive treatment option for tissue engineering and traumatic skin injuries since they can reduce dependence on donors and promote faster repair through strategic surface engineering. Current scaffolds present limitations in handling, preparation, shelf life, and sterilization options. In this study, bio-inspired hierarchical all-carbon structures comprising carbon nanotube (CNT) carpets covalently bonded to flexible carbon fabric have been investigated as a platform for cell growth and future tissue regeneration applications. CNTs are known to provide guidance for cell growth, but loose CNTs are susceptible to intracellular uptake and are suspected to cause in vitro and in vivo cytotoxicity. This risk is suppressed in these materials due to the covalent attachment of CNTs on a larger fabric, and the synergistic benefits of nanoscale and micro-macro scale architectures, as seen in natural biological materials, can be obtained. The structural durability, biocompatibility, tunable surface architecture, and ultra-high specific surface area of these materials make them attractive candidates for wound healing. In this study, investigations of cytotoxicity, skin cell proliferation, and cell migration were performed, and results indicate promise in both biocompatibility and directed cell growth. Moreover, these scaffolds provided cytoprotection against environmental stressors such as Ultraviolet B (UVB) rays. It was seen that cell growth could also be tailored through the control of CNT carpet height and surface wettability. These results support future promise in the design of hierarchical carbon scaffolds for strategic wound healing and tissue regeneration applications.

Polysulfone-based mixed matrix membranes loaded with a multifunctional hierarchical porous Ag-Cu dendrites@SiO2 core-shell nanostructure for wastewater treatment

Eliminating pollutants from wastewater is a crucial approach to securing the global water supply. It is well known that membrane purification technologies are remarkably attractive due to their high efficacy and low energy consumption. The neat polysulfone (PSF) polymer membranes, though, are prone to be fouled by organic pollutants, causing pore blockage and waned separation performance. We herein report and describe the rational design of a hierarchical porous Ag-Cu dendrites@SiO2 core-shell nanostructure/PSF mixed matrix membranes (MMMs) by coupling heterogeneous dendritic Ag-Cu@SiO2 core-shell nanostructure with PSF polymer matrix using facile phase inversion method for efficient separation of the protein (Bovine Serum Albumin; BSA) and Rose Bengal (RB) dye removal. Besides, for the first time, a theoretical mapping of molecular electrostatic potential (MESP) maps for chemical structure has been used for studying the interaction between the compounds (membrane moieties and pollutants). Practically, the SiO2 nanoparticles provide excellent hydrophilicity causing a sequential efficient, antifouling protein and dye separation with an outstanding rejection rate of over 96 % for both BSA and RB. In addition, the porous hierarchical scaffold formed from the hydrophilic Ag-Cu nanosheets embedded with SiO2 nanoparticles greatly assists the rapid permeation of water with a high flux rate of up to 50 L m−2 h−1 bar−1 for pure water. Furthermore, the hydrophilic nature of Ag and Cu nanoparticles also renders this membrane with a high removal capability for dye blocking enabling it to remove soluble pollutants in molecular dimensions as well. This design strategy not only provides an outstanding membrane for water purification but also sheds light on the design of multi-purpose functional membranes for a variety of energy and environment-related applications.

Pomegranate-Bionic Encapsulating Horseradish Peroxidase Using Dopamine Flexible Scaffold-Coated Multishell Porous ZIF-8 To Enhance Immunochromatographic Diagnosis.

Nanoparticle-natural enzyme complexes are receiving increasing attention as the promising signal reporters for colorimetric lateral flow immunoassay (LFIA). Nonetheless, it remains a challenge to develop the nanocomplexes with high loading efficiency, catalytic efficiency, and colorimetric signal brightness. Herein, inspired by pomegranate structure, we reported the synthesis of a colorimetric catalytic nanocomplex ((HRP@ZIF-8)3@PDA@HRP), using dopamine flexible scaffold-coated multishell porous zeolitic imidazolate framework-8 (ZIF-8) as a hierarchical scaffold to encapsulate horseradish peroxidase (HRP), and described its potential to promote an ultrasensitive colorimetric LFIA of cardiac troponin I (cTnI). (HRP@ZIF-8)3@PDA@HRP exhibited ultrahigh HRP loading efficiency and catalytic activity due to the epitaxial shell-by-shell overgrowth of porous ZIF-8 scaffold, which provided more cavities for enzyme immobilization and a diffusion path for the catalytic substrate. Furthermore, the polydopamine (PDA) layer on the (HRP@ZIF-8)3 surface both enhanced the colorimetric signal brightness and acted as a flexible scaffold to immobilize HRP, further increasing the amount of enzyme. Following integration with LFIA, the developed platform achieved an ultrasensitive colorimetric test strip assay for cTnI with pre- and postcatalytic naked-eye detection sensitivities of 0.5 ng mL-1 and 0.01 ng mL-1, respectively, which were 4/2- and 200/100-fold higher than gold nanoparticles (AuNPs)/PDA-based LFIA and comparable to chemiluminescence immunoassay. Further, the quantitative testing results of the developed colorimetric LFIA on 57 clinical serum samples agreed well with the clinical data. This work provides ideas for the design of natural enzymes-based colorimetric catalytic nanocomplex to encourage applications for the development of ultrasensitive LFIA for early diseases diagnosis.

Ni3V2O8 Nanosheets Grafted on 3D Helical‐shaped Carbon Nanocoils as A Binder‐free Hierarchical Composite for Efficient Non‐enzymatic Glucose Sensing

AbstractHigh fabrication cost, chemical instability, and complex immobilization of enzyme molecules are critical issues of enzyme‐based glucose sensors. Designing state‐of‐the‐art, binder‐free, and non‐enzymatic glucose sensing probes plays an imperative role to cope with the aforementioned issues. 3D carbonaceous nanomaterials coated with transition metal vanadates (TMVs) are a favorable biomimetic platform for glucose quantification. Peculiar hierarchical structure, enhanced conductivity, synergistic interaction, multiple oxidation states, and high catalytic activity would make such composite a potential contender for non‐enzymatic glucose sensing. Herein, 3D helical‐shaped carbon nanocoils (CNCs) are grown on nickel foam (NF) via chemical vapor deposition method to prepare a robust CNCs/NF scaffold. Then, a hydrothermal route is followed to grow interconnected free‐standing Ni3V2O8 nanosheets (NSs) on CNCs/NF scaffold. This novel and binder‐free Ni3V2O8 NSs/CNCs/NF hierarchical composite possesses superior electrochemical active area (ECSA) and exceptional electrochemical efficacy. Amperometric analysis exhibits extremely prompt detection time (0.1 s), elevated sensitivity (5214 µA mM−1 cm−2), and low detection limit (0.04 µM). Developed sensor demonstrates appreciable recoveries (93.3 to 103.3%) regarding glucose concentration in human serum. The appealing analytical results show that deployment of a 3D helical‐shaped hierarchical smart scaffold can be an effective strategy for developing efficient and advanced non‐enzymatic glucose sensors.

Hierarchical fibrous collagen/poly(ε-caprolactone) structure fabricated with a 3D-printing process for tissue engineering applications

Hierarchical scaffolds have been extensively used in various tissue engineering applications as they can provide unique biofunctional properties, including biophysical cues, to successfully accomplish preferred cell attachment, growth, and differentiation depending on the target tissues. In this study, we propose a new strategy for fabricating hierarchical structures consisting of microfibrous collagen/poly(ε-caprolactone) (PCL) bundles obtained using a 3D printing process supplemented with a unique bioink, plasma treatment, and collagen coating process. To obtain the hierarchical fibrous PCL structure, we used an alginate matrix hydrogel to form a microfibrous bundle of dispersed PCL components using elongational and shear stresses within a printing nozzle. By controlling various mixture ratios of alginate and PCL, processing temperature, pneumatic pressure, and nozzle moving speeds, a stable hierarchical structure consisting of PCL microfibers was obtained. To demonstrate the feasibility of hierarchical PCL-based structures coated with type I collagen, we investigated whether the construct affects the alignment and differentiation of myoblasts. The hierarchical fibrous biocomposite constructs presented a higher degree of myogenic activity than the control, which was fabricated using normal printing/collagen coating processes. Furthermore, the hierarchical PCL structures were further elaborated using 10 × simulated body fluid (SBF) resulting in a scaffold consisting of a hydroxyapatite (HA) layer. The hierarchical collagen/PCL/HA structures were evaluated with the aim of obtaining a functional scaffold that could efficiently induce osteogenesis to the human adipose stem cells (hASCs). These in vitro results suggest that the fibrous composite structure can provide enhanced osteogenic activity compared to the normally printed control (collagen/PCL/HA).

Collagen Nanoyarns: Hierarchical Three-Dimensional Biomaterial Constructs.

Hierarchical fibrous scaffolds (HFS) consist of nanoscale fibers arranged in larger macroscale structures, much in the same pattern as in native tissue such as tendon and bone. Creation of continuous macroscale nanofiber yarns has been made possible using modified electrospinning set-ups that combine electrospinning with techniques such as twisting, drawing, and winding. In this paper, a modified electrospinning setup was used to create continuous yarns of twisted type I collagen nanofibers, also known as collagen nanoyarns (CNY), from collagen solution prepared in acetic acid. Fabricated CNYs were cross-linked and characterized using SEM imaging and mechanical testing, while denaturation of collagen and dissolution of the scaffolds were assessed using circular dichroism (CD) and UV-vis spectroscopy, respectively. HeLa cells were then cultured on the nanoyarns for 24 h to assess cell adhesion on the scaffolds. Scanning electron micrographs revealed a twisted nanofiber morphology with an average nanofiber diameter of 213 ± 60 nm and a yarn diameter of 372 ± 23 μm that shrank by 35% after covalent cross-linking. Structural denaturation assessment of native collagen using circular dichroism (CD) spectroscopy showed that 60% of the triple-helical collagen content in CNYs was retained. Cross-linking of CNYs significantly improved their mechanical properties as well as stability in buffered saline with no sign of degradation for 14 days. In addition, CNY strength and stiffness increased significantly with cross-linking although in the wet state, significant loss in these properties, with a corresponding increase in elasticity, was observed. HeLa cells cultured on cross-linked CNYs for 24 h adhered to the yarn surface and oriented along the nanofiber alignment axis, displaying the characteristic spindle-like morphology of cells grown on surfaces with aligned topography. Collectively, the results demonstrate the promising potential of collagen nanoyarns as a new class of shapable biomaterial scaffold and building block for generating macroscale fiber-based tissues.

Hierarchical porous ECM scaffolds incorporating GDF-5 fabricated by cryogenic 3D printing to promote articular cartilage regeneration

BackgroundIn recent years, there has been significant research progress on in situ articular cartilage (AC) tissue engineering with endogenous stem cells, which uses biological materials or bioactive factors to improve the regeneration microenvironment and recruit more endogenous stem cells from the joint cavity to the defect area to promote cartilage regeneration.MethodIn this study, we used ECM alone as a bioink in low-temperature deposition manufacturing (LDM) 3D printing and then successfully fabricated a hierarchical porous ECM scaffold incorporating GDF-5.ResultsComparative in vitro experiments showed that the 7% ECM scaffolds had the best biocompatibility. After the addition of GDF-5 protein, the ECM scaffolds significantly improved bone marrow mesenchymal stem cell (BMSC) migration and chondrogenic differentiation. Most importantly, the in vivo results showed that the ECM/GDF-5 scaffold significantly enhanced in situ cartilage repair.ConclusionIn conclusion, this study reports the construction of a new scaffold based on the concept of in situ regeneration, and we believe that our findings will provide a new treatment strategy for AC defect repair.

Biomimetic hydroxyapatite coating on the 3D-printed bioactive porous composite ceramic scaffolds promoted osteogenic differentiation via PI3K/AKT/mTOR signaling pathways and facilitated bone regeneration in vivo

• Bionic hierarchical scaffold fabricated by 3D-printing and surface mineralization. • The obtained biomimetic multi-structured scaffolds facilitate bone regeneration. • Regulation of cell fate in activated PI3K/AKT/mTOR signaling were confirmed. • Hydroxyapatite coating accelerates osseointegration and enhance bone-augmentation. • A two-step method enriches and guides the design of modified bone graft materials. The architecture and surface modifications have been regarded as effective methods to enhance the biological response of biomaterials in bone tissue engineering. The porous architecture of the implantation was essential conditions for bone regeneration. Meanwhile, the design of biomimetic hydroxyapatite (HAp) coating on porous scaffolds was demonstrated to strengthen the bioactivity and stimulate osteogenesis. However, bioactive bio-ceramics such as β-tricalcium phosphate (β-TCP) and calcium silicate (CS) with superior apatite-forming ability were reported to present better osteogenic activity than that of HAp. Hence in this study, 3D-printed interconnected porous bioactive ceramics β-TCP/CS scaffold was fabricated and the biomimetic HAp apatite coating were constructed in situ via hydrothermal reaction, and the effects of HAp apatite layer on the fate of mouse bone mesenchymal stem cells (mBMSCs) and the potential mechanisms were explored. The results indicated that HAp apatite coating enhanced cell proliferation, alkaline phosphatase (ALP) activity, and osteogenic gene expression. Furthermore, PI3K/AKT/mTOR signaling pathway is proved to have an important impact on cellular functions. The present results demonstrated that the key molecules of phosphatidylinositol 3-kinase (PI3K), protein kinase B (AKT) and mammalian target of rapamycin (mTOR) were activated after the biomimetic hydroxyapatite coating were constructed on the 3D-printed ceramic scaffolds. Besides, the activated influence on the protein expression of Runx2 and BMP2 could be suppressed after the treatment of inhibitor HY-10358. In vivo studies showed that the constructed HAp coating promoted bone formation and strengthen the bone quality. These results suggest that biomimetic HAp coating constructed on the 3D-printed bioactive composite scaffolds could strengthen the bioactivity and the obtained biomimetic multi-structured scaffolds might be a potential alternative bone graft for bone regeneration.

3D Printed Hierarchical Porous Poly(ε-caprolactone) Scaffolds from Pickering High Internal Phase Emulsion Templating.

In the realm of biomaterials, particularly bone tissue engineering, there has been a great increase in interest in scaffolds with hierarchical porosity and customizable multifunctionality. Recently, the three-dimensional (3D) printing of biopolymer-based inks (solutions or emulsions) has gained high popularity for fabricating tissue engineering scaffolds, which optimally satisfies the desired properties and performances. Herein, therefore, we explore the fabrication of 3D printed hierarchical porous scaffolds of poly(ε-caprolactone) (PCL) using the water-in-oil (w/o) Pickering PCL high internal phase emulsions (HIPEs) as the ink in 3D printer. The Pickering PCL HIPEs stabilized using hydrophobically modified nanoclay comprised of aqueous poly(vinyl alcohol) (PVA) as the dispersed phase. Rheological measurements suggested the shear thinning behavior of Pickering HIPEs having a dispersed droplet diameter of 3-25 μm. The pore morphology resembling the natural extracellular matrix and the mechanical properties of scaffolds were customized by tuning the emulsion composition and 3D printing parameters. In vitro biomineralization and drug release studies proved the scaffolds' potential in developing the apatite-rich bioactive interphase and controlled drug delivery, respectively. During in vitro osteoblast (MG63) growth experiments for up to 7 days, good adhesion and proliferation on PCL scaffolds confirmed their cytocompatibility, assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) analysis. This study suggests that the assembly of HIPE templates and 3D printing is a promising approach to creating hierarchical porous scaffolds potentially suitable for bone tissue engineering and can be stretched to other biopolymers as well.