Recent Advances in 3D Printing for Parenteral Applications.

3D printing has emerged as an advanced manufacturing technology in the field of pharmaceutical sciences. Despite much focus on enteral applications, there has been a lack of research focused on potential benefits of 3D printing for parenteral applications such as wound dressings, biomedical devices, and regenerative medicines. 3D printing technologies, including fused deposition modeling, vat polymerization, and powder bed printing, allow for rapid prototyping of personalized medications, capable of producing dosage forms with flexible dimensions based on patient anatomy as well as dosage form properties such as porosity. Considerations such as printing properties and material selection play a key role in determining overall printability of the constructs. These parameters also impact drug release kinetics, and mechanical properties of final printed constructs, which play a role in modulating immune response upon insertion in the body. Despite challenges in sterilization of printed constructs, additional post-printing processing procedures, and lack of regulatory guidance, 3D printing will continue to evolve to meet the needs of developing effective, personalized medicines for parenteral applications.

Bladder muscle regeneration enhanced by sustainable delivery of heparin from bilayer scaffolds carrying stem cells in a rat bladder partial cystectomy model.

In bladder tissue engineering, regeneration of muscle is of equal importance to epithelial regeneration. However, as yet there is no effective strategy for promoting bladder muscle regeneration. In this study we aim to promote bladder muscle regeneration by sustainably delivering heparin from a bilayer scaffold carrying stem cells. The bilayer scaffold [heparin-polycaprolactone (PCL)/bladder decellularized matrix (BAM) Hep-PB/PCL] comprises an electrospun layer (Hep-PB electrospun membrane) and a three-dimensional (3D) printed layer (PCL scaffold), fabricated via coaxial-electrospinning and 3D printing, respectively. Heparin was encapsulated into the core of the Hep-PB fibers with a core-shell structure to sustain its release. The morphology of the bilayer scaffold and the microstructure of the electrospun fibers were characterized. The release behavior of heparin from various electrospun membranes was evaluated. The role of Hep-PB in promoting myogenic differentiation of the adipose-derived stem cells (ADSCs) through sustainable release of heparin was also evaluated. After 7 d culture, Hep-PB/PCL scaffolds carrying ADSCs (defined as ASHP) were used for bladder reconstruction in a rat partial cystotomy model. The result shows that the PCL printed scaffold has ordered macropores (∼370 µm), unlike the compact microstructure of electrospun films. The Hep-PB membrane exhibits a sustained release behavior for heparin. This membrane also shows better growth and proliferation of ADSCs than the other membranes. The polymerase chain reaction results show that the expression of smooth muscle cell markers in ADSCs is enhanced by the Hep-PB scaffold. The results of retrograde urethrography and histological staining indicate that the bladder volume in the ASHP group recovers better, and the regenerated bladder muscle bundles are arranged in a more orderly fashion compared with the direct suture and bladder decellularized matrix groups. Therefore, findings from this study show that bladder muscle regeneration could be enhanced by bilayer scaffolds delivering heparin and carrying stem cells, which may provide a new strategy for bladder tissue engineering.

Biomimetic Boundary-Based Scaffold Design for Tissue Engineering Applications.

The design of optimized scaffolds for tissue engineering and regenerative medicine is a key topic of current research, as the complex macro- and micro-architectures required for scaffold applications depend not only on the mechanical properties but also on the physical and molecular queues of the surrounding tissue within the defect site. Thus, the prediction of optimal features for tissue engineering scaffolds is very important, for both its physical and biological properties.The relationship between high scaffold porosity and high mechanical properties is contradictory, as it becomes even more complex due to the scaffold degradation process. Biomimetic design has been considered as a viable method to design optimum scaffolds for tissue engineering applications. In this research work, the scaffold designs are based on biomimetic boundary-based bone micro-CT data. Based on the biomimetic boundaries and with the aid of topological optimization schemes, the boundary data and given porosity is used to obtain the initial scaffold designs. In summary, the proposed scaffold design scheme uses the principles of both the boundaries and porosity of the micro-CT data with the aid of numerical optimization and simulation tools.

Surface Tension-Assisted Additive Manufacturing of Tubular, Multicomponent Biomaterials.

The fabrication of functional biomaterials for organ replacement and tissue repair remains a major goal of biomedical engineering. Advances in additive manufacturing (AM) technologies and computer-aided design (CAD) are advancing the tools available for the production of these devices. Ideally, these constructs should be matched to the geometry and mechanical properties of the tissue at the needed implant site. To generate geometrically defined and structurally supported multicomponent and cell-laden biomaterials, we have developed a method to integrate hydrogels with 3D-printed lattice scaffolds leveraging surface tension-assisted AM.

Natural-Based Hydrogels for Tissue Engineering Applications.

In the field of tissue engineering and regenerative medicine, hydrogels are used as biomaterials to support cell attachment and promote tissue regeneration due to their unique biomimetic characteristics. The use of natural-origin materials significantly influenced the origin and progress of the field due to their ability to mimic the native tissues' extracellular matrix and biocompatibility. However, the majority of these natural materials failed to provide satisfactory cues to guide cell differentiation toward the formation of new tissues. In addition, the integration of technological advances, such as 3D printing, microfluidics and nanotechnology, in tissue engineering has obsoleted the first generation of natural-origin hydrogels. During the last decade, a new generation of hydrogels has emerged to meet the specific tissue necessities, to be used with state-of-the-art techniques and to capitalize the intrinsic characteristics of natural-based materials. In this review, we briefly examine important hydrogel crosslinking mechanisms. Then, the latest developments in engineering natural-based hydrogels are investigated and major applications in the field of tissue engineering and regenerative medicine are highlighted. Finally, the current limitations, future challenges and opportunities in this field are discussed to encourage realistic developments for the clinical translation of tissue engineering strategies.

Microfabrication of a biomimetic arcade-like electrospun scaffold for cartilage tissue engineering applications.

In recent years, the engineering of biomimetic cellular microenvironments has emerged as a top priority for regenerative medicine, being the in vitro recreation of the arcade-like cartilaginous tissue one of the most critical challenges due to the notorious absence of cost- and time-efficient microfabrication techniques capable of building 3D fibrous scaffolds with precise anisotropic properties. Taking this into account, we suggest a feasible and accurate methodology that uses a sequential adaptation of an electrospinning-electrospraying set up to construct a hierarchical system comprising both polycaprolactone (PCL) fibres and polyethylene glycol sacrificial microparticles. After porogen leaching, the bi-layered PCL scaffold was capable of presenting not only a depth-dependent fibre orientation similar to natural cartilage, but also mechanical features and porosity proficient to encourage an enhanced cell response. In fact, cell viability studies confirmed the biocompatibility of the scaffold and its ability to guarantee suitable cell adhesion, proliferation and migration throughout the 3D anisotropic fibrous network during 21 days of culture. Additionally, likewise the hierarchical relationship between chondrocytes and their extracellular matrix, the reported PCL scaffold was able to induce depth-dependent cell-material interactions responsible for promoting a spatial modulation of the morphology, alignment and density of the cells in vitro.

Effects of novel non-thermal atmospheric plasma treatment of titanium on physical and biological improvements and in vivo osseointegration in rats.

Titanium (Ti) has achieved extensive applications due to its excellent biocompatibility and mechanical properties. Plasma can enhance surface hydrophilia of Ti with decreased carbon contamination. The traditional conditions using a single gas plasma was for longer treatment time and more prone to being contaminated. We designed and developed novel and universal apparatus and methods with a special clamping device of non-thermal atmospheric plasma (NTAP) treatment using mixed gas for Ti surface activation. We systematically and quantitatively investigated the effective effects of NTAP-Ti. The surface water contact angle decreased by 100%, the carbon content decreased by 80% and oxygen content increased by 50% in the novel NTAP-Ti surfaces. NTAP treatment accelerated the attachment, spread, proliferation, osteogenic differentiation and mineralization of MC3T3-E1 mouse preosteoblasts in vitro. The percentage of bone-to-implant contact increased by 25-40%, and the osteoclasts and bone resorption were suppressed by 50% in NTAP-Ti in vivo. In conclusion, NTAP-Ti substantially enhanced the physical and biological effects and integration with bone. The novel and universal apparatus and methods with a special clamping device using gas mixtures are promising for implant activation by swiftly and effectively changing the Ti surface to a hydrophilic one to enhance dental and orthopedic applications.

Recent developments in regenerative ophthalmology.

Regenerative medicine (RM) is one of the most promising disciplines for advancements in modern medicine, and regenerative ophthalmology (RO) is one of the most active fields of regenerative medicine. This review aims to provide an overview of regenerative ophthalmology, including the range of tools and materials being used, and to describe its application in ophthalmologic subspecialties, with the exception of surgical implantation of artificial tissues or organs (e.g., contact lens, artificial cornea, intraocular lens, artificial retina, and bionic eyes) due to space limitations. In addition, current challenges and limitations of regenerative ophthalmology are discussed and future directions are highlighted.

Mechanically strengthened hybrid peptide-polyester hydrogel and potential applications in spinal cord injury repair.

ADA16 peptide hydrogels have been broadly used in tissue engineering due to their good biocompatibility and nanofibrous structure mimicking the native extracellular matrix (ECM). However, the low mechanical strength often fails them as implantable scaffolds. To improve the mechanical stability of the RADA16 peptide hydrogel, a photocrosslinkable diacrylated poly(ϵ-caprolactone)-b-poly(ethylene glycol)-b-poly(ϵ-caprolactone) triblock copolymer (PCECDA) was physically combined with RADA16 peptide pre-modified with cell adhesive Arg-Gly-Asp sequence (RADA16-RGD). Consequently, an interpenetrating network, RADA16-RGD/PCECDA, was formed with highly enhanced mechanical property. The storage modulus (G') of RADA16-RGD/PCECDA (6% w/v, mass ratio mRADA16-RGD/mPCECDA = 1:5) hybrid hydrogel was elevated to ∼2000 Pa, compared to the RADA16-RGD (1% w/v) hydrogel alone (∼700 Pa). Furthermore, this hybrid hydrogel retained the nanofibrous structure from RADA16-RGD peptide, but underwent much slower degradation than RADA16-RGD alone. In vitro, the hybrid hydrogel exhibited excellent cytocompatibility and promoted the differentiation of the seeded neural stem cells. Finally, the RADA16-RGD/PCECDA hydrogel demonstrated capability in reducing cavitation, glial scar formation and inflammation at the lesion sites of hemi-sectioned spinal cord injury model in rats, which holds great potential for application in neural tissue engineering and regenerative medicine.

Incorporation of a silicon-based polymer to PEG-DA templated hydrogel scaffolds for bioactivity and osteoinductivity.

A scaffold that is inherently bioactive, osteoinductive and osteoconductive may guide mesenchymal stem cells (MSCs) to regenerate bone tissue in the absence of exogenous growth factors. Previously, we established that hydrogel scaffolds formed by crosslinking methacrylated star poly(dimethylsiloxane) (PDMSstar-MA) with diacrylated poly(ethylene glycol) (PEG-DA) promote bone bonding by induction of hydroxyapatite formation ("bioactive") and promote MSC lineage progression toward osteoblast-like fate ("osteoinductive"). Herein, we have combined solvent induced phase separation (SIPS) with a fused salt template to create PDMSstar-PEG hydrogel scaffolds with controlled PDMSstar-MA distribution as well as interconnected macropores of a tunable size to allow for subsequent cell seeding and neotissue infiltration ("osteoconductive"). Scaffolds were prepared with PDMSstar-MA of two number average molecular weights (Mns) (2k and 7k) with varying PDMSstar-MA:PEG-DA ratios and template salt sizes. The distribution of PDMSstar-MA within the hydrogels was examined as well as pore size, percent interconnectivity, dynamic and static moduli, hydration, degradation and in vitro bioactivity (i.e. mineralization when exposed to simulated body fluid, SBF). Finally, cell culture with seeded human bone marrow-derived MSCs (hBMSCs) was used to confirm non-cytotoxicity and characterize osteoinductivity. Tunable, interconnected macropores were achieved by utilization of a fused salt template of a specified salt size during fabrication. Distribution of PDMSstar-MA within the PEG-DA matrix improved for the lower Mn and contributed to differences in specific material properties (e.g. local modulus) and cellular response. However, all templated SIPS PDMSstar-PEG hydrogels were confirmed to be bioactive, non-cytotoxic and displayed PDMSstar-MA dose-dependent osteogenesis. STATEMENT OF SIGNIFICANCE: A tissue engineering scaffold that can inherently guide mesenchymal stem cells (MSCs) to regenerate bone tissue without growth factors would be a more cost-effective and safe strategy for bone repair. Typically, glass/ceramic fillers are utilized to achieve this through their ability to induce hydroxyapatite formation ("bioactive") and promote MSC differentiation to an osteoblast-like fate ("osteoinductive"). Herein, we have fabricated an interconnected, macroporous PEG-DA hydrogel scaffold that utilizes PDMSstar-MA as a bioactive and osteoinductive scaffold component. We were able to show that these PDMSstar-PEG hydrogels maintain several key material characteristics for bone repair. Further, bioactivity and osteoinductivity were simultaneously achieved in human bone marrow-derived MSC culture, representing a notable achievement for an exclusively material-based strategy.

Self-assembling in situ gel based on lyotropic liquid crystals containing VEGF for tissue regeneration.

Current tissue-regenerative biomaterials confront two critical issues: the uncontrollable delivery capacity of vascular endothelial growth factor (VEGF) for adequate vascularization and the poor mechanical properties of the system for tissue regeneration. To overcome these two issues, a self-assembling in situ gel based on lyotropic liquid crystals (LLC) was developed. VEGF-LLC was administrated as a precursor solution that would self-assemble into an in situ gel with well-defined internal inverse bicontinuous cubic phases when exposed to physiological fluid at a defect site. The inverse cubic phase with a 3D bicontinuous water channel enabled a 7-day sustained release of VEGF. The release profile of VEGF-LLC was controlled using octyl glucoside (OG) as a hydration-modulating agent, which could enlarge the water channel, yielding a 2-fold increase in water channel size and a 7-fold increase in VEGF release. For the mechanical properties, the elastic modulus was found to decrease from ∼100 kPa to ∼1.2 kPa, which might be more favorable for angiogenesis. Furthermore, the self-recovery ability of the VEGF-LLC gel was confirmed by quick recovery of the inner network in step-strain measurements. In vitro, VEGF-LLC considerably promoted the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) as compared to free VEGF (p < 0.05). Furthermore, angiogenesis was successfully induced in rats after subcutaneous injection of VEGF-LLC. The self-assembling LLC gel showed satisfactory degradability and mild inflammatory response with little impact on the surrounding tissue. The controllable release profile and unique mechanical properties of VEGF-LLC offer a new approach for tissue regeneration. STATEMENT OF SIGNIFICANCE: The potential clinical use of currently available biomaterials in tissue regeneration is limited by their uncontrollable drug delivery capacity and poor mechanical properties. Herein, a self-assembling in situ gel based on lyotropic liquid crystals (LLC) for induced angiogenesis was developed. The results showed that the addition of octyl glucoside (OG) could change the water channel size of LLC, which enabled the LLC system to release VEGF in a sustained manner and to possess a suitable modulus to favor angiogenesis simultaneously. Moreover, the self-recovery capability allowed the gel to match the deformation of surrounding tissues during body motion to maintain its properties and reduce discomfort. In vivo, angiogenesis was induced by VEGF-LLC 14 days after administering subcutaneous injection. These results highlight the potential of LLC as a promising sustained protein drug delivery system for vascular formation and tissue regeneration.

Preparation of Decellularized Triphasic Hierarchical Bone-Fibrocartilage-Tendon Composite Extracellular Matrix for Enthesis Regeneration.

Tendon to bone (enthesis) rupture, which may cause disability and persistent pain, shows high rate of re-rupture after surgical repair. Tendon or enthesis scaffolds have been widely studied, but few of these materials can recapitulate the tissue continuity. Thus, this study is conducted to prepare a triphasic decellularized bone-fibrocartilage-tendon (D-BFT) composite scaffold. The D-BFT scaffold is developed using a combination of physical, chemical, and enzymatic treatments using liquid nitrogen, Triton-X 100, sodium-dodecyl sulfate, and DNase I, which effectively removes the cell components while preserving the biological composite and microstructure. Moreover, the mechanical properties of D-BFT are highly preserved and similar to those of the human Achilles tendon. Additionally, in vitro, mesenchymal stem cells (MSCs) adhered, proliferated, and infiltrated into the D-BFT scaffold, and MSC differentiation is confirmed by up-regulation of osteogenic-related and tenogenic-related genes. The repair outcomes are explored by applying the D-BFT scaffold in the model of femur-tibia defects in vivo, which shows good repair results. Thus, the D-BFT scaffold developed in this study is a promising graft for enthesis regeneration.

Biomimetic modification of dual porosity poly(2-hydroxyethyl methacrylate) hydrogel scaffolds-porosity and stem cell growth evaluation.

The macroporous synthetic poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels as 3D cellular scaffolds with specific internal morphology, so called dual pore size, were designed and studied. The morphological microstructure of hydrogels was characterized in the gel swollen state and the susceptibility of gels for stem cells was evaluated. The effect of specific chemical groups covalently bound in the hydrogel network by copolymerization on cell adhesion and growth, followed by effect of laminin coating were investigated. The evaluated gels contained either carboxyl groups of the methacrylic acid or quaternary ammonium groups brought by polymerizable ammonium salt or their combinations. The morphology of swollen gel was visualized using the laser scanning confocal microscopy. All hydrogels had very similar porous structures - their matrices contained large pores (up to 102 µm) surrounded with gel walls with small pores (100 µm). The total pore volume in hydrogels swollen in buffer solution ranged between 69 and 86 vol%. Prior to the seeding of the mouse embryonal stem cells, the gels were coated with laminin. The hydrogel with quaternary ammonium groups (with or without laminin) stimulated the cell growth the most. The laminin coating lead to a significant and quaternary ammonium groups. The gel chemical modification influenced also the topology of cell coverage that ranged from individual cell clusters to well dispersed multi cellular structures. Findings in this study point out the laser scanning confocal microscopy as an irreplaceable method for a precise and quick assessment of the hydrogel morphology. In addition, these findings help to optimize the chemical composition of the hydrogel scaffold through the combination of chemical and biological factors leading to intensive cell attachment and proliferation.

In vitro evaluation of functionalized decellularized muscle scaffold for in situ skeletal muscle regeneration.

Current treatment options for repairing volumetric muscle loss injury involve the use of existing host tissue like muscular flaps or grafts. However, host muscle tissue may not be available and donor site morbidity, such as functional loss and volume deficiency, is often present. In this study, we developed a biofunctionalized muscle-derived decellularized extracellular matrix scaffolding system to utilize endogenous stem/progenitor cells for in situ muscle tissue regeneration. We optimized the decellularization process to enhance cellular infiltration and fabricated an insulin-like growth factor-binding protein 3 (IGFBP-3)-conjugated scaffold for controlled delivery of IGF-I. We then tested in vitro characterization including IGF-I release kinetics and cellular infiltration. In addition, we have analyzed the bioactivities of skeletal muscle cells (C2C12) to assess the indirect effect of released IGF-1 from the scaffold. The IGFBP-3 conjugated scaffolds demonstrated showed sustained release of IGF-1 and 1% SDS decellularized scaffold with IGF-1 showed higher cellular infiltration compared to control scaffolds (no conjugation). In indirect bioactivity assay, IGF-1 conjugated scaffold showed 2.1-fold increased cell activity compared to control (fresh media). Our results indicate that IGFBP-3/IGF-I conjugated scaffold has the potential to be used for in situ muscle tissue regeneration.

Nanofiber-based matrices for rotator cuff regenerative engineering.

The rotator cuff consists of a cuff of soft tissue responsible for rotating the shoulder. Rotator cuff tendon tears are responsible for a significant source of disability and pain in the adult population. Most rotator cuff tendon tears occur at the bone-tendon interface. Tear size, patient age, fatty infiltration of muscle, have a major influence on the rate of retear after surgical repair. The high incidence of retears (up to 94% in some studies) after surgery makes rotator cuff injuries a critical musculoskeletal problem to address. The limitations of current treatments motivate regenerative engineering approaches for rotator cuff regeneration. Various fiber-based matrices are currently being investigated due to their structural similarity with native tendons and their ability to promote regeneration. This review will discuss the current approaches for rotator cuff regeneration, recent advances in fabrication and enhancement of nanofiber-based matrices and the development and use of complex nano/microstructures for rotator cuff regeneration. STATEMENT OF SIGNIFICANCE: Regeneration paradigms for musculoskeletal tissues involving the rotator cuff of the shoulder have received great interest. Novel technologies based on nanomaterials have emerged as possible robust solutions for rotator cuff injury and treatment due to structure/property relationships. The aim of the review submitted is to comprehensively describe and evaluate the development and use of nano-based material technologies for applications to rotator cuff tendon healing and regeneration.

3D Bioprinting in Skeletal Muscle Tissue Engineering.

Skeletal muscle tissue engineering (SMTE) aims at repairing defective skeletal muscles. Until now, numerous developments are made in SMTE; however, it is still challenging to recapitulate the complexity of muscles with current methods of fabrication. Here, after a brief description of the anatomy of skeletal muscle and a short state-of-the-art on developments made in SMTE with "conventional methods," the use of 3D bioprinting as a new tool for SMTE is in focus. The current bioprinting methods are discussed, and an overview of the bioink formulations and properties used in 3D bioprinting is provided. Finally, different advances made in SMTE by 3D bioprinting are highlighted, and future needs and a short perspective are provided.

Mesenchymal Stem Cell Capping on ECM-Anchored Caspase Inhibitor-Loaded PLGA Microspheres for Intraperitoneal Injection in DSS-Induced Murine Colitis.

Mesenchymal stem cells (MSCs) are considered as a promising alternative for the treatment of various inflammatory disorders. However, poor viability and engraftment of MSCs after transplantation are major hurdles in mesenchymal stem cell therapy. Extracellular matrix (ECM)-coated scaffolds provide better cell attachment and mechanical support for MSCs after transplantation. A single-step method for ECM functionalization on poly(lactic-co-glycolic acid) (PLGA) microspheres using a novel compound, dopamine-conjugated poly(ethylene-alt-maleic acid), as a stabilizer during the preparation of microspheres is reported. The dopamine molecules on the surface of microspheres provide active sites for the conjugation of ECM in an aqueous solution. The results reveal that the viability of MSCs improves when they are coated over the ECM-functionalized PLGA microspheres (eMs). In addition, the incorporation of a broad-spectrum caspase inhibitor (IDN6556) into the eMs synergistically increases the viability of MSCs under in vitro conditions. Intraperitoneal injection of the MSC-microsphere hybrid alleviates experimental colitis in a murine model via inhibiting Th1 and Th17 differentiation of CD4+ T cells in colon-draining mesenteric lymph nodes. Therefore, drug-loaded ECM-coated surfaces may be considered as attractive tools for improving viability, proliferation, and functionality of MSCs following transplantation.

Recent advances in gelatin-based therapeutics.

INTRODUCTION: Biomaterials have provided a wide range of exciting opportunities in tissue engineering and regenerative medicine. Gelatin, a collagen-derived natural biopolymer, has been extensively used in regenerative medicine applications over the years, due to its cell-responsive properties and the capacity to deliver a wide range of biomolecules. AREAS COVERED: The most relevant properties of gelatin as biomaterial are presented together with its main therapeutic applications. The latter includes drug delivery systems, tissue engineering approaches, potential uses as ink for 3D/4D Bioprinting, and its relevance in organ-on-a-chip platforms. EXPERT OPINION: Advances in polymer chemistry, mechanobiology, imaging technologies, and 3D biofabrication techniques have expanded the application of gelatin in multiple biomedical research applications ranging from bone and cartilage tissue engineering, to wound healing and anti-cancer therapy. Here, we highlight the latest advances in gelatin-based approaches within the fields of biomaterial-based drug delivery and tissue engineering together with some of the most relevant challenges and limitations.

A Pyk2 inhibitor incorporated into a PEGDA-gelatin hydrogel promotes osteoblast activity and mineral deposition.

Pyk2 is a non-receptor tyrosine kinase that belongs to the family of focal adhesion kinases. Studies from our laboratory and others demonstrated that mice lacking the Pyk2 gene (Ptk2B) have high bone mass, which was due to increased osteoblast activity, as well as decreased osteoclast activity. It was previously reported that a chemical inhibitor that targets both Pyk2 and its homolog FAK, led to increased bone formation in ovariectomized rats. In the current study, we developed a hydrogel containing poly(ethylene glycol) diacrylate (PEGDA) and gelatin which was curable by visible-light and was suitable for the delivery of small molecules, including a Pyk2-targeted chemical inhibitor. We characterized several critical properties of the hydrogel, including viscosity, gelation time, swelling, degradation, and drug release behavior. We found that a hydrogel composed of PEGDA1000 plus 10% gelatin (P1000:G10) exhibited Bingham fluid behavior that can resist free flowing before in situ polymerization, making it suitable for use as an injectable carrier in open wound applications. The P1000:G10 hydrogel was cytocompatible and displayed a more delayed drug release behavior than other hydrogels we tested. Importantly, the Pyk2-inhibitor-hydrogel retained its inhibitory activity against the Pyk2 tyrosine kinase, and promoted osteoblast activity and mineral deposition in vitro. Overall, our findings suggest that a Pyk2-inhibitor based hydrogel may be suitable for the treatment of craniofacial and appendicular skeletal defects and targeted bone regeneration.

Development of a Three-Dimensional Bioengineered Platform for Articular Cartilage Regeneration.

Degenerative cartilage pathologies are nowadays a major problem for the world population. Factors such as age, genetics or obesity can predispose people to suffer from articular cartilage degeneration, which involves severe pain, loss of mobility and consequently, a loss of quality of life. Current strategies in medicine are focused on the partial or total replacement of affected joints, physiotherapy and analgesics that do not address the underlying pathology. In an attempt to find an alternative therapy to restore or repair articular cartilage functions, the use of bioengineered tissues is proposed. In this study we present a three-dimensional (3D) bioengineered platform combining a 3D printed polycaprolactone (PCL) macrostructure with RAD16-I, a soft nanofibrous self-assembling peptide, as a suitable microenvironment for human mesenchymal stem cells' (hMSC) proliferation and differentiation into chondrocytes. This 3D bioengineered platform allows for long-term hMSC culture resulting in chondrogenic differentiation and has mechanical properties resembling native articular cartilage. These promising results suggest that this approach could be potentially used in articular cartilage repair and regeneration.