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•Heparin functionalized PCL/gelatin co-spun nanofibrous dressings were synthesized.•Fabricated dressings showed improved mechanical and degradation properties.•Fabricated dressings ...showed exogenous and endogenous GFs sequestration ability.•In-vivo, synergistic effect of exogenous and endogenous GFs promoted tissue regeneration.
Growth factors (GFs) are signaling molecules that are principle mediators in tissue regeneration. Biomaterial scaffolds employed as wound dressings are often hampered by their limitations to deliver GFs exogenously due to their instability and low half-life. The key to overcome this challenge lies in the better organization and use of endogenous pro-regenerative GFs released at regenerative site, with an aim to minimize the sole dependency on exogenous factors. Considering such challenges, this research utilizes the exogenous and endogenous GFs sequestering capability of heparin functionalized PCL/gelatin co-spun nanofabrics to mediate synergistically driven tissue regeneration by utilizing combined therapeutic effect of exogenous and endogenous GFs, and thereby minimizing the sole dependency on exogenous GFs for tissue regeneration. Basic fibroblast growth factor (bFGF) was chosen as GF for exogenous loading whereas vascular endothelial growth factor (VEGF) was chosen as a representative example to demonstrate the endogenous pro-regenerative GF sequestration capability of fabricated nanofabrics. From our results, the fabricated nanofabrics showed loading efficiency of 80% for exogenous bFGF and can sequester 15-fold more amount of endogenous VEGF compared to non-heparin functionalized nanofibrous dressings. When applied as wound dressings, heparin functionalized nanofibers showed better therapeutic capability compared to control groups that were treated using patches without heparin functionalization, indicating endogenously driven tissue regeneration. This was indicated by significant higher number of newly formed skin appendages, lesser scarring and lower inflammatory levels in newly formed granulation. Additionally, further improvements in therapeutic effect was observed when exogenous bFGF was employed indicating effectiveness of synergistically mediated tissue regeneration.
Endothelization of a tissue-engineered substrate is important for its application as an artificial vascular graft. Despite recent advancements in artificial graft fabrication, a graft of <5 mm is ...difficult to fabricate owing to insufficient endothelization that results in thrombosis after transplantation. We aimed to perform a co-culture of adipose-derived mesenchymal stem cells (MSCs) with human umbilical vein endothelial cells (HUVECs) on antithrombogenic polycaprolactone (PCL)/heparin-gelatin co-spun nanofibers to evaluate the role of co-culturing in promoting quick endothelization of vascular substrates without surface modification by growth factors or other ECM proteins that trigger the endothelization process. Using a co-axial electrospinning technique, we attempted to fabricate our scaffold balancing between mechanical properties and biocompatibility. Antithrombogenic characteristics were then imparted to the fabricated nanofiber substrate by grafting of heparin. Finally, we performed a co-culture of MSCs and HUVECs on the fabricated co-spun nanofiber substrate to obtain proper endothelization of our material under the in-vitro culture. Staining for CD-31 at seven days of culture revealed enhanced CD-31 expression under the co-culture condition; actin staining revealed healthy cobblestone HUVEC morphology, suggesting that MSCs can aid in proper endothelization. Hence, we conclude that co-culture is effective for quick endothelization of vascular substrates.
•PCL/Gelatin core-shell type nanofibers were successfully fabricated using co-axial electrospinning technique•Heparin was successfully immobilized on fabricated co-spun nanofibrous substrate•Nanofibers showed improved mechanical characteristics and enough antithrombogenic characteristics•MSCs and HUVECs co-cultured on fabricated nano-fabrics accelerated the process of endothelium development.
The effective delivery of anti-cancer drugs with minimal side effects and better therapeutic efficacy has remained an active area of research for many decades. Organogels have gained attention in ...recent years as potential drug delivery systems due to their high bioavailability, no first-pass metabolism and rapid action. Considering this, in the current study an organogel based nanoemulsion was developed aiming to effectively deliver hydrophobic drugs via encapsulation within in situ gellable organogel droplets, termed as gel-in-water (G/W) nanoemulsion. G/W nanoemulsion was prepared using a combination of lipiodol and organogelator 12-hydroxystearic acid (12-HSA) as inner gel phase; dispersed in water by ultrasonication and stabilized with polyoxyethylene hydrogenated castor oil (HCO-60) as a surfactant. The prepared nanoemulsion showed high drug loading efficiency (≈97%) with a mean diameter of 206 nm. Lower polydispersity index (PdI) value (≈0.1) suggests monodispersed nature of G/W nanoemulsion in the continuous phase. G/W nanoemulsion was found stable over six months in terms of particle size, zeta potential and pH at different storage temperatures. There was no cytotoxic effect of prepared G/W nanoemulsion on primary hepatocytes in vitro. In contrast, paclitaxel-loaded G/W showed a significant decrease in melanoma cell growth (*p < 0.05) both in vitro and in vivo. Our results support the hypothesis that organogel based nanoemulsions can be a promising drug delivery system.
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•Gel-in-water (G/W) nanoemulsion was developed for hydrophobic drug delivery.•12-HSA forms the inner gel phase of G/W and ensures high encapsulation efficiency.•G/W was found biocompatible to primary rat hepatocytes in vitro.•Paclitaxel loaded G/W showed cytotoxicity against cancer both in vitro and in vivo.
Three-dimensional (3D) printing techniques for scaffold fabrication have shown promising advancements in recent years owing to the ability of the latest high-performance printers to mimic the native ...tissue down to submicron scales. Nevertheless, host integration and performance of scaffolds in vivo have been severely limited owing to the lack of robust strategies to promote vascularization in 3D printed scaffolds. As a result, researchers over the past decade have been exploring strategies that can promote vascularization in 3D printed scaffolds toward enhancing scaffold functionality and ensuring host integration. Various emerging strategies to enhance vascularization in 3D printed scaffolds are discussed. These approaches include simple strategies such as the enhancement of vascular in-growth from the host upon implantation by scaffold modifications to complex approaches wherein scaffolds are fabricated with their own vasculature that can be directly anastomosed or microsurgically connected to the host vasculature, thereby ensuring optimal integration. The key differences among the techniques, their pros and cons, and the future opportunities for utilizing each technique are highlighted here. The Review concludes with the current limitations and future directions that can help 3D printing emerge as an effective biofabrication technique to realize tissues with physiologically relevant vasculatures to ultimately accelerate clinical translation.
Medical dressings play an important role in the field of tissue engineering owing to their ability to accelerate the process of wound healing. Great efforts have been made to fabricate wound ...dressings with distinctive features for promoting wound healing. However, most of the current synthesis methods either generate dressings of uniform size or involve complex fabrication techniques, thus limiting their commercialization for the personalized dressings. We report here a dressing, which presents a paradigm shift in the design of the dressing from uniform films to a micro-patterned film. The hypothesis driving the design is the ability of the 3D patterns to provide an efficient transient matrix filling the depth of the wound rather than just providing a barrier and slight re-epithelialization. We demonstrate the use of the digital light processing 3D printing technique to generate micro-pyramid-decorated wound healing dressings with individualized design and with bio-compatible gelatin methacryloyl to contact the wounded areas. In addition to providing better adhesion to the migratory cells, the micro-pyramids also enable covalent conjugation of heparin, providing capability to sequester endogenous growth factors (GFs). Based on these advantages, the developed dressing not only adheres strongly to the wound bed but also promotes the treatment of a rat wound model by utilizing the power of endogenous GFs for tissue regeneration. Thus, it is believed that the developed dressing can break through the limitation of traditional wound treatment and be an ideal candidate for wound healing.
The future of burn wound treatment lies in developing bioactive dressings for faster and more effective healing and regeneration. Silk fibroin (SF) hydrogels have proven regenerative abilities and ...are being explored as a burn wound dressing. However, unfavorable gelation conditions limit the processability and clinical application. Herein a white light-responsive photopolymerization technique was adapted for gelation via photooxidation of tyrosine. To render the gel suitable for application to irregular and non-planar burn surfaces, SF gel-incorporated dressing (SFD) was fabricated. The mild gelation conditions using white light afforded the loading of drugs for local delivery. The moisture balance ability of the dressing was confirmed by the favorable measures of swelling capacity (106 ± 1 %) and moisture retention (≈10 h). The in vitro cytocompatibility of the gel was confirmed using HaCaT cells. Finally, in vivo performance of the SFD was tested on a second-degree burn in a rodent model. The gross analysis and histological assessment revealed scarless healing in SFD-treated groups. Overall, the SFD developed in this work is shown to be a promising candidate for advanced burn wound care.
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There are only a few reports of implantable 4D printed biomaterials, most of which exhibit slow deformations rendering them unsuitable for in situ surgical deployment. In this study, a hydrogel ...system is engineered with defined swelling behaviors, which demonstrated excellent printability in extrusion-based 3D printing and programmed shape deformations post-printing. Shape deformations of the spatially patterned hydrogels with defined infill angles are computationally predicted for a variety of 3D printed structures, which are subsequently validated experimentally. The gels are coated with gelatin-rich nanofibers to augment cell growth. 3D-printed hydrogel sheets with pre-programmed infill patterns rapidly self-rolled into tubes in vivo to serve as nerve-guiding conduits for repairing sciatic nerve defects in a rat model. These 4D-printed hydrogels minimized the complexity of surgeries by tightly clamping the resected ends of the nerves to assist in the healing of peripheral nerve damage, as revealed by histological evaluation and functional assessments for up to 45 days. This work demonstrates that 3D-printed hydrogels can be designed for programmed shape changes by swelling in vivo to yield 4D-printed tissue constructs for the repair of peripheral nerve damage with the potential to be extended in other areas of regenerative medicine.
The latest advancements in the field of manufacturing for biomedicine, digital health, targeted therapy, and personalized medicine have fuelled the fabrication of smart medical devices. ...Four-dimensional (4D) fabrication strategies, which combine the manufacturing of three-dimensional (3D) parts with smart materials and/or design, have proved beneficial in creating customized and self-fitting structures that change their properties on demand with time. These frontier techniques that yield dynamic implants can indeed alleviate various drawbacks of current clinical practices, such as the use of sutures and complex microsurgeries and associated inflammation, among others. Among various clinical applications, 4D fabrication has lately made remarkable progress in the development of next-generation nerve-guiding conduits for treating peripheral nerve injuries (PNIs) by improving the end-to-end co-aptation of transected nerve endings. The current perspective highlights the relevance of 4D fabrication in developing state-of-the-art technologies for the treatment of PNIs. Various 4D fabrication/bio-fabrication techniques for PNI treatment are summarized while identifying the challenges and opportunities for the future. Such advancements hold immense promise for improving the quality of life of patients suffering from nerve damage and the potential for extending the treatment of many other disorders. Although the techniques are being described for PNIs, they will lend themselves suitably to certain cases of cranial nerve injuries as well.
The latest advancements in 4D fabrication of state-of-the-art nerve conduits are critically discussed. Such advancements can overcome various drawbacks of traditional approaches including the need for suturing and tedious fabrication processes, among others.
Four-dimensional (4D) printing of hydrogel enabled the fabrication of complex scaffold geometries out of static parts. Although current 4D fabrication strategies are promising for creating vascular ...parts such as tubes, developing branched networks or tubular junctions is still challenging. Here, for the first time, a 4D printing approach is employed to fabricate T-shaped perfusable bifurcation using an extrusion-based multi-material 3D printing process. An alginate/methylcellulose-based dual-component hydrogel system (with defined swelling behavior) is nanoengineered with carbonized alginate (~100 nm) to introduce anti-oxidative, anti-inflammatory, and anti-thrombotic properties and shape-shifting properties. A computational model to predict shape deformations in the printed hydrogels with defined infill angles was designed and further validated experimentally. Shape deformations of the 3D-printed flat sheets were achieved by ionic cross-linking. An undisrupted perfusion of a dye solution through a T-junction with minimal leakage mimicking blood flow through vessels is also demonstrated. Moreover, human umbilical vein endothelial and fibroblast cells seeded with printed constructs show intact morphology and excellent cell viability. Overall, developed strategy paves the way for manufacturing self-actuated vascular bifurcations with remarkable anti-thrombotic properties to potentially treat coronary artery diseases.
4D printing of shape memory polymers (SMPs) and composites has been realized for a multitude of applications spanning healthcare, soft robotics, environment, space,
etc.
However, demonstrating such ...materials for
in vivo
applications has not been possible to a large extent due to the unavailability of suitable materials with recovery temperatures at around physiological levels. Also, direct heating to trigger shape recovery in SMPs is not a practical and elegant approach in many cases. In this study, polylactide-
co
-trimethylene carbonate (PLMC), an SMP, has been endowed with magnetic iron oxide (Fe
3
O
4
) nanoparticles to realize remote heating under an alternating magnetic field and at temperatures around 40 °C. The PLMC-5% Fe
3
O
4
composite was 3D printed into a variety of shapes, including scaffolds, fixed into pre-programmed temporary shapes to be deployed minimally invasively, and then recovered into original shapes under magnetic actuation. The extent of shape fixity (>95%) and recovery (>99%) was excellent, and the recovery time was short (<30 s). Additionally, these magnetic composites could potentially be guided to the site of deployment through permanent magnets. Both PLMC and its composites were printed in distinct regions of a single structure, deformed, and then recovered by selective and sequential stimulation by a magnetic field and heat, respectively. The materials (both PLMC and its nanocomposites) exhibited excellent
in vitro
biocompatibility and
in vivo
biocompatibility. The composite was as efficient as PLMC in supporting osteogenic differentiation of the pre-osteoblasts, as confirmed by mineral deposition
in vitro
. Thus, the 4D printed shape memory magnetic nanocomposite presented here could be an excellent candidate biomaterial for engineering deployable scaffolds and medical devices, among other implantable applications.
Herein, an alternating magnetic field-triggered shape memory polymer composite has been 3D printed as a tissue scaffold that can be remotely deployed at physiological temperatures and can be extended to soft robotics.
