Engineering 3D-printed core-shell hydrogel scaffolds reinforced with hybrid hydroxyapatite/polycaprolactone nanoparticles for in vivo bone regeneration

Biomedical Composites of Polycaprolactone/Hydroxyapatite for Bioplotting: Comprehensive Interpretation of the Reinforcement Course

Robust materials in medical applications are sought after and researched, especially for 3D printing in bone tissue engineering. Poly[ε-caprolactone] (PCL) is a commonly used polymer for scaffolding and other medical uses. Its strength is a drawback compared to other polymers. Herein, PCL was mixed with hydroxyapatite (HAp). Composites were developed at various concentrations (0.0-8.0 wt. %, 2.0 step), aiming to enhance the strength of PCL with a biocompatible additive in bioplotting. Initially, pellets were derived from the shredding of filaments extruded after mixing PCL and HAp at predetermined quantities for each composite. Specimens were then manufactured by bioplotting 3D printing. The samples were tested for their thermal and rheological properties and were also mechanically, morphologically, and chemically examined. The mechanical properties included tensile and flexural investigations, while morphological and chemical examinations were carried out employing scanning electron microscopy and energy dispersive spectroscopy, respectively. The structure of the manufactured specimens was analyzed using micro-computed tomography with regard to both their dimensional deviations and voids. PCL/HAp 6.0 wt. % was the composite that showed the most enhanced mechanical (14.6% strength improvement) and structural properties, proving the efficiency of HAp as a reinforcement filler in medical applications.

Biomimetic Hydrogels as the Inductive Endochondral Ossification Template for Promoting Bone Regeneration

Repairing critical size bone defects (CSBD) is a major clinical challenge and requires effective intervention by biomaterial scaffolds. Inspired by the fact that the cartilaginous template-based endochondral ossification (ECO) process is crucial to bone healing and development, developing biomimetic biomaterials to promote ECO is recognized as a promising approach for repairing CSBD. With the unique highly hydrated 3D polymeric network, hydrogels can be designed to closely emulate the physiochemical properties of cartilage matrix to facilitate ECO. In this review, the various preparation methods of hydrogels possessing the specific physiochemical properties required for promoting ECO are introduced. The materiobiological impacts of the physicochemical properties of hydrogels, such as mechanical properties, topographical structures and chemical compositions on ECO, and the associated molecular mechanisms related to the BMP, Wnt, TGF-β, HIF-1α, FGF, and RhoA signaling pathways are further summarized. This review provides a detailed coverage on the materiobiological insights required for the design and preparation of hydrogel-based biomaterials to facilitate bone regeneration.

The Blue Treasure: Comprehensive Biorefinery of Blue Crab (Callinectes sapidus)

The blue crab, Callinectes sapidus (Rathbun, 1896), has become an invading species in the Mediterranean region, almost completely replacing native species within a few years and causing significant loss to local production. In some areas, there is an urgent need to propose new supply chains based on blue crab exploitation, where the potential valorisation routes for unsaleable blue crab and waste play an important role. The final purpose is to transform a threat into a treasure, towards a more sustainable world. In addition to applications in food industries, the considerable quantity of bioactive compounds in by-products, such as polysaccharides, proteins, amino acids, carotenoids, and chitin, needs to be capitalised by means of efficacious strategies and appropriate management. Crab exoskeleton can also be exploited as a carbonaceous material with applications in several fields, including medicine. Blue crab bioactive molecules have been widely recognised for having antioxidant, anticancer, antidiabetic, anti-inflammatory, and antimicrobial properties. Due to these functional and distinctive activities, such high-value components could be employed in various industries such as food-feed-pharma and cosmetics. Recycling and reusing these underutilised but economically valuable waste or by-products could help to reduce the environmental impacts of the whole supply chain from the perspective of the circular economy.

In situ polymer gelation in confined flow controls intermittent dynamics

Polymer flows through pores, nozzles and other small channels govern engineered and naturally occurring dynamics in many processes, from 3D printing to oil recovery in the earth's subsurface to a wide variety of biological flows. The crosslinking of polymers can change their material properties dramatically, and it is advantageous to know a priori whether or not crosslinking polymers will lead to clogged channels or cessation of flow. In this study, we investigate the flow of a common biopolymer, alginate, while it undergoes crosslinking by the addition of a crosslinker, calcium, driven through a microfluidic channel at constant flow rate. We map the boundaries defining complete clogging and flow as a function of flow rate, polymer concentration, and crosslinker concentration. Interestingly, the boundaries of the dynamic behavior qualitatively match the thermodynamic jamming phase diagram of attractive colloidal particles. That is, polymer clogging occurs in a region analogous to colloids in a jammed state, while the polymer flows in regions corresponding to colloids in a liquid phase. However, between the dynamic regimes of complete clogging and unrestricted flow, we observe a remarkable phenomenon in which the crosslinked polymer intermittently clogs the channel. This pattern of deposition and removal of a crosslinked gel is simultaneously highly reproducible, long-lasting, and controllable by system parameters. Higher concentrations of polymer and cross-linker result in more frequent ablation, while gels formed at lower component concentrations ablate less frequently. Upon ablation, the eluted gel maintains its shape, resulting in micro-rods several hundred microns long. Our results suggest both rich dynamics of intermittent flows in crosslinking polymers and the ability to control them.

Tailoring the properties of composite scaffolds with a 3D-Printed lattice core and a bioactive hydrogel shell for tissue engineering

The optimal performance of scaffolds for tissue engineering relies on a proper combination of their constituent biomaterials and on the design of their structure. In this work, composite scaffolds with a core-shell architecture are realized by grafting a gelatin-chitosan hydrogel onto a 3D-printed polylactic acid (PLA) core, aiming in particular at bone regeneration. This hydrogel was recently found to sustain osteogenic differentiation of mesenchymal stromal cells, leading to new bone tissue formation. Here, the integration with rigid PLA lattice structures provides improved mechanical support and finer control of strength and stiffness. The core is prepared by fused deposition modeling with the specific aim to study several lattice structures and thereby better tune the scaffold mechanical properties. In fact, the core architecture dictates the scaffold strength and stiffness, which are seen to match those of different types of bone tissue. For all lattice types, the hydrogel is found to penetrate throughout the entire core and to present highly interconnected pores for cell colonization. By varying the void volume fraction in the core it is possible to significantly change the bioactive shell content, as well as the mechanical properties, over a wide range of values. Looking for design guidelines, relationships between stiffness/strength and density are here outlined for scaffolds featuring different lattice parameters. Moreover, by acting on the core strut arrangement, scaffolds are reinforced along specific directions, as evaluated under compressive and bending loading conditions.

3D printed scaffolds based on hyaluronic acid bioinks for tissue engineering: a review

Hyaluronic acid (HA) is widely distributed in human connective tissue, and its unique biological and physicochemical properties and ability to facilitate biological structure repair make it a promising candidate for three-dimensional (3D) bioprinting in the field of tissue regeneration and biomedical engineering. Moreover, HA is an ideal raw material for bioinks in tissue engineering because of its histocompatibility, non-immunogenicity, biodegradability, anti-inflammatory properties, anti-angiogenic properties, and modifiability. Tissue engineering is a multidisciplinary field focusing on in vitro reconstructions of mammalian tissues, such as cartilage tissue engineering, neural tissue engineering, skin tissue engineering, and other areas that require further clinical applications. In this review, we first describe the modification methods, cross-linking methods, and bioprinting strategies for HA and its derivatives as bioinks and then critically discuss the strengths, shortcomings, and feasibility of each method. Subsequently, we reviewed the practical clinical applications and outcomes of HA bioink in 3D bioprinting. Finally, we describe the challenges and opportunities in the development of HA bioink to provide further research references and insights.

Current Biomedical Applications of 3D-Printed Hydrogels

Three-dimensional (3D) printing, also known as additive manufacturing, has revolutionized the production of physical 3D objects by transforming computer-aided design models into layered structures, eliminating the need for traditional molding or machining techniques. In recent years, hydrogels have emerged as an ideal 3D printing feedstock material for the fabrication of hydrated constructs that replicate the extracellular matrix found in endogenous tissues. Hydrogels have seen significant advancements since their first use as contact lenses in the biomedical field. These advancements have led to the development of complex 3D-printed structures that include a wide variety of organic and inorganic materials, cells, and bioactive substances. The most commonly used 3D printing techniques to fabricate hydrogel scaffolds are material extrusion, material jetting, and vat photopolymerization, but novel methods that can enhance the resolution and structural complexity of printed constructs have also emerged. The biomedical applications of hydrogels can be broadly classified into four categories-tissue engineering and regenerative medicine, 3D cell culture and disease modeling, drug screening and toxicity testing, and novel devices and drug delivery systems. Despite the recent advancements in their biomedical applications, a number of challenges still need to be addressed to maximize the use of hydrogels for 3D printing. These challenges include improving resolution and structural complexity, optimizing cell viability and function, improving cost efficiency and accessibility, and addressing ethical and regulatory concerns for clinical translation.

New Poly(lactic acid)-Hydrogel Core-Shell Scaffolds Highly Support MSCs' Viability, Proliferation and Osteogenic Differentiation

Scaffolds for tissue engineering are expected to respond to a challenging combination of physical and mechanical requirements, guiding the research towards the development of novel hybrid materials. This study introduces innovative three-dimensional bioresorbable scaffolds, in which a stiff poly(lactic acid) lattice structure is meant to ensure temporary mechanical support, while a bioactive gelatin-chitosan hydrogel is incorporated to provide a better environment for cell adhesion and proliferation. The scaffolds present a core-shell structure, in which the lattice core is realized by additive manufacturing, while the shell is nested throughout the core by grafting and crosslinking a hydrogel forming solution. After subsequent freeze-drying, the hydrogel network forms a highly interconnected porous structure that completely envelops the poly(lactic acid) core. Thanks to this strategy, it is easy to tailor the scaffold properties for a specific target application by properly designing the lattice geometry and the core/shell ratio, which are found to significantly affect the scaffold mechanical performance and its bioresorption. Scaffolds with a higher core/shell ratio exhibit higher mechanical properties, whereas reducing the core/shell ratio results in higher values of bioactive hydrogel content. Hydrogel contents up to 25 wt% could be achieved while maintaining high compression stiffness (>200 MPa) and strength (>5 MPa), overall, within the range of values displayed by human bone tissue. In addition, mechanical properties remain stable after prolonged immersion in water at body temperature for several weeks. On the other hand, the hydrogel undergoes gradual and homogeneous degradation over time, but the core-shell integrity and structural stability are nevertheless maintained during at least 7-week hydrolytic degradation tests. In vitro experiments with human mesenchymal stromal cells reveal that the core-shell scaffolds are biocompatible, and their physical-mechanical properties and architecture are suitable to support cell growth and osteogenic differentiation, as demonstrated by hydroxyapatite formation. These results suggest that the bioresorbable core-shell scaffolds can be considered and further studied, in view of clinically relevant endpoints in bone regenerative medicine.

Towards Polycaprolactone-Based Scaffolds for Alveolar Bone Tissue Engineering: A Biomimetic Approach in a 3D Printing Technique

The alveolar bone is a unique type of bone, and the goal of bone tissue engineering (BTE) is to develop methods to facilitate its regeneration. Currently, an emerging trend involves the fabrication of polycaprolactone (PCL)-based scaffolds using a three-dimensional (3D) printing technique to enhance an osteoconductive architecture. These scaffolds are further modified with hydroxyapatite (HA), type I collagen (CGI), or chitosan (CS) to impart high osteoinductive potential. In conjunction with cell therapy, these scaffolds may serve as an appealing alternative to bone autografts. This review discusses research gaps in the designing of 3D-printed PCL-based scaffolds from a biomimetic perspective. The article begins with a systematic analysis of biological mineralisation (biomineralisation) and ossification to optimise the scaffold's structural, mechanical, degradation, and surface properties. This scaffold-designing strategy lays the groundwork for developing a research pathway that spans fundamental principles such as molecular dynamics (MD) simulations and fabrication techniques. Ultimately, this paves the way for systematic in vitro and in vivo studies, leading to potential clinical applications.

Atorvastatin liposomes in a 3D-printed polymer film: a repurposing approach for local treatment of oral candidiasis

Oral candidiasis (OC) is an opportunistic fungal infection, common amongst the elderly and the immunocompromised. Unfortunately, the therapeutic efficacy of common antifungals is imperiled by the rise of antifungal drug resistance. An alternative promising therapeutic option possibly contributing to antifungal therapy is drug repurposing. Herein, we aimed to employ novel pharmaceutical drug delivery for enhancing the emerging antifungal potential of the hypocholesterolemic drug atorvastatin (ATV). ATV-propylene-glycol-liposomes (ATV/PG-Lip) were prepared then integrated in 3D-printed (3DP) mucoadhesive films comprising chitosan, polyvinyl-alcohol and hydroxypropyl methylcellulose, as an innovative blend, for the management of OC. ATV/PG-Lip demonstrated good colloidal properties of particle size (223.3 ± 2.1 nm), PDI (0.12 ± 0.001) and zeta potential (-18.2 ± 0.3 mV) with high entrapment efficiency (81.15 ± 1.88%) and sustained drug release. Also, ATV/PG-Lip showed acceptable three-month colloidal stability and in vitro cytocompatibility on human gingival fibroblasts. The developed 3DP-films exhibited controlled ATV release (79.4 ± 1.4% over 24 h), reasonable swelling and mucoadhesion (2388.4 ± 18.4 dyne/cm2). In vitro antifungal activity of ATV/PG-Lip was confirmed against fluconazole-resistant Candida albicans via minimum inhibitory concentration determination, time-dependent antifungal activity, agar diffusion and scanning electron microscopy. Further, ATV/PG-Lip@3DP-film exceeded ATV@3DP-film in amelioration of infection and associated inflammation in an in vivo oral candidiasis rabbit model. Accordingly, the results confirm the superiority of the fabricated ATV/PG-Lip@3DP-film for the management of oral candidiasis and tackling antifungal resistance.

Bioinspired 3D-printed scaffold embedding DDAB-nano ZnO/nanofibrous microspheres for regenerative diabetic wound healing

There is a constant demand for novel materials/biomedical devices to accelerate the healing of hard-to-heal wounds. Herein, an innovative 3D-printed bioinspired construct was developed as an antibacterial/regenerative scaffold for diabetic wound healing. Hyaluronic/chitosan (HA/CS) ink was used to fabricate a bilayer scaffold comprising a dense plain hydrogel layer topping an antibacterial/regenerative nanofibrous layer obtained by incorporating the hydrogel with polylactic acid nanofibrous microspheres (MS). These were embedded with nano ZnO (ZNP) or didecyldimethylammonium bromide (DDAB)-treated ZNP (D-ZNP) to generate the antibacterial/healing nano/micro hybrid biomaterials, Z-MS@scaffold and DZ-MS@scaffold. Plain and composite scaffolds incorporating blank MS (blank MS@scaffold) or MS-free ZNP@scaffold and D-ZNP@scaffold were used for comparison. 3D printed bilayer constructs with customizable porosity were obtained as verified by SEM. The DZ-MS@scaffold exhibited the largest total pore area as well as the highest water-uptake capacity andin vitroantibacterial activity. Treatment ofStaphylococcus aureus-infected full thickness diabetic wounds in rats indicated superiority of DZ-MS@scaffold as evidenced by multiple assessments. The scaffold afforded 95% wound-closure, infection suppression, effective regulation of healing-associated biomarkers as well as regeneration of skin structure in 14 d. On the other hand, healing of non-diabetic acute wounds was effectively accelerated by the simpler less porous Z-MS@scaffold. Information is provided for the first-time on the 3D printing of nanofibrous scaffolds using non-electrospun injectable bioactive nano/micro particulate constructs, an innovative ZNP-functionalized 3D-printed formulation and the distinct bioactivity of D-ZNP as a powerful antibacterial/wound healing promotor. In addition, findings underscored the crucial role of nanofibrous-MS carrier in enhancing the physicochemical, antibacterial, and wound regenerative properties of DDAB-nano ZnO. In conclusion, innovative 3D-printed DZ-MS@scaffold merging the MS-boosted multiple functionalities of ZNP and DDAB, the structural characteristics of nanofibrous MS in addition to those of the 3D-printed bilayer scaffold, provide a versatile bioactive material platform for diabetic wound healing and other biomedical applications.

Recent advances on 3D-printed PCL-based composite scaffolds for bone tissue engineering

Population ageing and various diseases have increased the demand for bone grafts in recent decades. Bone tissue engineering (BTE) using a three-dimensional (3D) scaffold helps to create a suitable microenvironment for cell proliferation and regeneration of damaged tissues or organs. The 3D printing technique is a beneficial tool in BTE scaffold fabrication with appropriate features such as spatial control of microarchitecture and scaffold composition, high efficiency, and high precision. Various biomaterials could be used in BTE applications. PCL, as a thermoplastic and linear aliphatic polyester, is one of the most widely used polymers in bone scaffold fabrication. High biocompatibility, low cost, easy processing, non-carcinogenicity, low immunogenicity, and a slow degradation rate make this semi-crystalline polymer suitable for use in load-bearing bones. Combining PCL with other biomaterials, drugs, growth factors, and cells has improved its properties and helped heal bone lesions. The integration of PCL composites with the new 3D printing method has made it a promising approach for the effective treatment of bone injuries. The purpose of this review is give a comprehensive overview of the role of printed PCL composite scaffolds in bone repair and the path ahead to enter the clinic. This study will investigate the types of 3D printing methods for making PCL composites and the optimal compounds for making PCL composites to accelerate bone healing.

Inorganic/organic combination: Inorganic particles/polymer composites for tissue engineering applications

Biomaterials have ushered the field of tissue engineering and regeneration into a new era with the development of advanced composites. Among these, the composites of inorganic materials with organic polymers present unique structural and biochemical properties equivalent to naturally occurring hybrid systems such as bones, and thus are highly desired. The last decade has witnessed a steady increase in research on such systems with the focus being on mimicking the peculiar properties of inorganic/organic combination composites in nature. In this review, we discuss the recent progress on the use of inorganic particle/polymer composites for tissue engineering and regenerative medicine. We have elaborated the advantages of inorganic particle/polymer composites over their organic particle-based composite counterparts. As the inorganic particles play a crucial role in defining the features and regenerative capacity of such composites, the review puts a special emphasis on the various types of inorganic particles used in inorganic particle/polymer composites. The inorganic particles that are covered in this review are categorised into two broad types (1) solid (e.g., calcium phosphate, hydroxyapatite, etc.) and (2) porous particles (e.g., mesoporous silica, porous silicon etc.), which are elaborated in detail with recent examples. The review also covers other new types of inorganic material (e.g., 2D inorganic materials, clays, etc.) based polymer composites for tissue engineering applications. Lastly, we provide our expert analysis and opinion of the field focusing on the limitations of the currently used inorganic/organic combination composites and the immense potential of new generation of composites that are in development.

3D printed tissue models: From hydrogels to biomedical applications

The development of new advanced constructs resembling structural and functional properties of human organs and tissues requires a deep knowledge of the morphological and biochemical properties of the extracellular matrices (ECM), and the capacity to reproduce them. Manufacturing technologies like 3D printing and bioprinting represent valuable tools for this purpose. This review will describe how morphological and biochemical properties of ECM change in different tissues, organs, healthy and pathological states, and how ECM mimics with the required properties can be generated by 3D printing and bioprinting. The review describes and classifies the polymeric materials of natural and synthetic origin exploited to generate the hydrogels acting as "inks" in the 3D printing process, with particular emphasis on their functionalization allowing crosslinking and conjugation with signaling molecules to develop bio-responsive and bio-instructive ECM mimics.

Three-Dimensional Impression of Biomaterials for Alveolar Graft: Scoping Review

Craniofacial bone defects are one of the biggest clinical challenges in regenerative medicine, with secondary autologous bone grafting being the gold-standard technique. The development of new three-dimensional matrices intends to overcome the disadvantages of the gold-standard method. The aim of this paper is to put forth an in-depth review regarding the clinical efficiency of available 3D printed biomaterials for the correction of alveolar bone defects. A survey was carried out using the following databases: PubMed via Medline, Cochrane Library, Scopus, Web of Science, EMBASE, and gray literature. The inclusion criteria applied were the following: in vitro, in vivo, ex vivo, and clinical studies; and studies that assessed bone regeneration resorting to 3D printed biomaterials. The risk of bias of the in vitro and in vivo studies was performed using the guidelines for the reporting of pre-clinical studies on dental materials by Faggion Jr and the SYRCLE risk of bias tool, respectively. In total, 92 publications were included in the final sample. The most reported three-dimensional biomaterials were the PCL matrix, β-TCP matrix, and hydroxyapatite matrix. These biomaterials can be combined with different polymers and bioactive molecules such as rBMP-2. Most of the included studies had a high risk of bias. Despite the advances in the research on new three-dimensionally printed biomaterials in bone regeneration, the existing results are not sufficient to justify the application of these biomaterials in routine clinical practice.

Janus-Inspired Core-Shell Structure Hydrogel Programmatically Releases Melatonin for Reconstruction of Postoperative Bone Tumor

At present, surgery is one of the main treatments for bone tumor. However, the risk of recurrence and the large area of bone defects after surgery pose a great challenge. Therefore, a Janus-inspired core-shell structure bone scaffold was designed to achieve the self-programmed release of melatonin at different concentrations, clearing the residual tumor cells at early stage after resection and promoting bone repair later. The layered differential load designs inspired by Janus laid the foundation for the differential release of melatonin, where sufficient melatonin inhibited tumor growth as low dose promoted osteogenesis. Then, the automatically programmed delivery of melatonin is achieved by the gradient degradation of the core-shell structure. In the material characterization, scanning electron microscopy revealed the core-shell structure. The drug release experiment and in vivo degradation experiment reflected the programmed differential release of melatonin. In the biological experiment part, in vivo and in vitro experiments not only confirmed the significant inhibitory effect of the core-shell hydrogel scaffold on tumor but also confirmed its positive effect on osteogenesis. Our Janus-inspired core-shell hydrogel scaffold provides a safe and efficient means to inhibit tumor recurrence and bone repair after bone tumor, and it also develops a new and efficient tool for differential and programmed release of other drugs.

PEEK and Hyaluronan-Based 3D Printed Structures: Promising Combination to Improve Bone Regeneration

Hybrid bone substitute made up of a 3D printed polyetheretherketone (PEEK) scaffold coated with methacrylated hyaluronic acid (MeHA)-hydroxyapatite (HAp) hydrogel is the objective of the present work. Development and characterization of the scaffold and of the MeHA-HAp after its infiltration and UV photocrosslinking have been followed by analyses of its biological properties using human mesenchymal stem cells (MSCs). Interconnected porous PEEK matrices were produced by fused deposition modeling (FDM) characterized by a reticular pattern with 0°/90° raster orientation and square pores. In parallel, a MeHA-HAp slurry has been synthesized and infiltrated in the PEEK scaffolds. The mechanical properties of the coated and pure PEEK scaffold have been evaluated, showing that the inclusion of MeHA-HAp into the lattice geometry did not significantly change the strength of the PEEK structure with Young's modulus of 1034.9 ± 126.1 MPa and 1020.0 ± 63.7 MPa for PEEK and PEEK-MeHA-HAp scaffolds, respectively. Human MSCs were seeded on bare and coated scaffolds and cultured for up to 28 days to determine the adhesion, proliferation, migration and osteogenic differentiation. In vitro results showed that the MeHA-HAp coating promotes MSCs adhesion and proliferation and contributes to osteogenic differentiation and extracellular matrix mineralization. This study provides an efficient solution for the development of a scaffold combining the great mechanical performances of PEEK with the bioactive properties of MeHA and HAp, having high potential for translational clinical applications.

Assessment of 3D-Printed Polycaprolactone, Hydroxyapatite Nanoparticles and Diacrylate Poly(ethylene glycol) Scaffolds for Bone Regeneration

Notwithstanding the advances achieved in the last decades in the field of synthetic bone substitutes, the development of biodegradable 3D-printed scaffolds with ideal mechanical and biological properties remains an unattained challenge. In the present work, a new approach to produce synthetic bone grafts that mimic complex bone structure is explored. For the first time, three scaffolds of various composition, namely polycaprolactone (PCL), PCL/hydroxyapatite nanoparticles (HANp) and PCL/HANp/diacrylate poly(ethylene glycol) (PEGDA), were manufactured by extrusion. Following the production and characterisation of the scaffolds, an in vitro evaluation was carried out using human dental pulp stem/stromal cells (hDPSCs). Through the findings, it was possible to conclude that, in all groups, the scaffolds were successfully produced presenting networks of interconnected channels, adequate porosity for migration and proliferation of osteoblasts (approximately 50%). Furthermore, according to the in vitro analysis, all groups were considered non-cytotoxic in contact with the cells. Nevertheless, the group with PEGDA revealed hydrophilic properties (15.15° ± 4.06) and adequate mechanical performance (10.41 MPa ± 0.934) and demonstrated significantly higher cell viability than the other groups analysed. The scaffolds with PEGDA suggested an increase in cell adhesion and proliferation, thus are more appropriate for bone regeneration. To conclude, findings in this study demonstrated that PCL, HANp and PEGDA scaffolds may have promising effects on bone regeneration and might open new insights for 3D tissue substitutes.

De novo dual functional 3D scaffold using computational simulation with controlled drug release

A novel and facile synthesis is made of cotton-like three-dimensional (3D) fibrous scaffold containing spatiotemporally defined patterns of simvastatin (SIM) optimized for angiogenesis-coupled osteogenesis. Herein, we demonstrate the 3D fiber deposition mechanism in detail during the electrospinning process via computer simulation. The 3D fibrous scaffolds were functionalized with hydroxyapatite nanoparticles (HA - NPs) to induce the biomineralization process mimicking the natural apatite layer. The morphology, physiochemical properties, biomimetic mineralization, and drug release of the as-fabricated 3D fibrous scaffolds of simvastatin-loaded poly (ɛ-caprolactone) poly (glycerol-sebacate) hydroxyapatite nanoparticles (3D - PGHS) were investigated. The effects of simvastatin on the osteogenic differentiation of human mesenchymal stem cells (hMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs) were assessed. The results showed that the 3D - PGHS both enhanced the expression of osteogenic markers including ALP, RUNX2, and COLA1 in hMSCs, and promoted the migration and tube formation of HUVECs. This finding demonstrates the potential of 3D scaffold-loaded SIM as a putative point-of-care therapy for tightly controlled tissue regeneration.

Vascularized bone regeneration accelerated by 3D-printed nanosilicate-functionalized polycaprolactone scaffold

Critical oral-maxillofacial bone defects, damaged by trauma and tumors, not only affect the physiological functions and mental health of patients but are also highly challenging to reconstruct. Personalized biomaterials customized by 3D printing technology have the potential to match oral-maxillofacial bone repair and regeneration requirements. Laponite (LAP) nanosilicates have been added to biomaterials to achieve biofunctional modification owing to their excellent biocompatibility and bioactivity. Herein, porous nanosilicate-functionalized polycaprolactone (PCL/LAP) was fabricated by 3D printing technology, and its bioactivities in bone regeneration were investigated in vitro and in vivo. In vitro experiments demonstrated that PCL/LAP exhibited good cytocompatibility and enhanced the viability of bone marrow mesenchymal stem cells (BMSCs). PCL/LAP functioned to stimulate osteogenic differentiation of BMSCs at the mRNA and protein levels and elevated angiogenic gene expression and cytokine secretion. Moreover, BMSCs cultured on PCL/LAP promoted the angiogenesis potential of endothelial cells by angiogenic cytokine secretion. Then, PCL/LAP scaffolds were implanted into the calvarial defect model. Toxicological safety of PCL/LAP was confirmed, and significant enhancement of vascularized bone formation was observed. Taken together, 3D-printed PCL/LAP scaffolds with brilliant osteogenesis to enhance bone regeneration could be envisaged as an outstanding bone substitute for a promising change in oral-maxillofacial bone defect reconstruction.

Recent advances in the local antibiotics delivery systems for management of osteomyelitis

Chronic osteomyelitis is a challenging disease due to its serious rates of mortality and morbidity while the currently available treatment strategies are suboptimal. In contrast to the adopted systemic treatment approaches after surgical debridement in chronic osteomyelitis, local drug delivery systems are receiving great attention in the recent decades. Local drug delivery systems using special carriers have the pros of enhancing the feasibility of penetration of antimicrobial agents to bone tissues, providing sustained release and localized concentrations of the antimicrobial agents in the infected area while avoiding the systemic side effects and toxicity. Most important, the incorporation of osteoinductive and osteoconductive materials in these systems assists bones proliferation and differentiation, hence the generation of new bone materials is enhanced. Some of these systems can also provide mechanical support for the long bones during the healing process. Most important, if the local systems are designed to be injectable to the affected site and biodegradable, they will reduce the level of invasion required for implantation and can win the patients’ compliance and reduce the healing period. They will also allow multiple injections during the course of therapy to guard against the side effect of the long-term systemic therapy. The current review presents different available approaches for delivering antimicrobial agents for the treatment of osteomyelitis focusing on the recent advances in researches for local delivery of antibiotics.

HIGHLIGHTS

Chronic osteomyelitis is a challenging disease due to its serious mortality and morbidity rates and limited effective treatment options.

Local drug delivery systems are receiving great attention in the recent decades.

Osteoinductive and osteoconductive materials in the local systems assists bones proliferation and differentiation

Local systems can be designed to provide mechanical support for the long bones during the healing process.

Designing the local system to be injectable to the affected site and biodegradable will reduces the level of invasion and win the patients’ compliance.

Glibenclamide Nanocrystal-Loaded Bioactive Polymeric Scaffolds for Skin Regeneration: In Vitro Characterization and Preclinical Evaluation

Skin restoration following full-thickness injury poses significant clinical challenges including inflammation and scarring. Medicated scaffolds formulated from natural bioactive polymers present an attractive platform for promoting wound healing. Glibenclamide was formulated in collagen/chitosan composite scaffolds to fulfill this aim. Glibenclamide was forged into nanocrystals with optimized colloidal properties (particle size of 352.2 nm, and polydispersity index of 0.29) using Kolliphor as a stabilizer to allow loading into the hydrophilic polymeric matrix. Scaffolds were prepared by the freeze drying method using different total polymer contents (3-6%) and collagen/chitosan ratios (0.25-2). A total polymer content of 3% at a collagen/chitosan ratio of 2:1 (SCGL3-2) was selected based on the results of in vitro characterization including the swelling index (1095.21), porosity (94.08%), mechanical strength, rate of degradation and in vitro drug release. SCGL3-2 was shown to be hemocompatible based on the results of protein binding, blood clotting and percentage hemolysis assays. In vitro cell culture studies on HSF cells demonstrated the biocompatibility of nanocrystals and SCGL3-2. In vivo studies on a rat model of a full-thickness wound presented rapid closure with enhanced histological and immunohistochemical parameters, revealing the success of the scaffold in reducing inflammation and promoting wound healing without scar formation. Hence, SCGL3-2 could be considered a potential dermal substitute for skin regeneration.

3D printed bioinspired scaffolds integrating doxycycline nanoparticles: Customizable implants for in vivo osteoregeneration

3D printing has revolutionized pharmaceutical research, with applications encompassing tissue regeneration and drug delivery. Adopting 3D printing for pharmaceutical drug delivery personalization via nanoparticle-reinforced hydrogel scaffolds promises great regenerative potential. Herein, we engineered novel core/shell, bio-inspired, drug-loaded polymeric hydrogel scaffolds for pharmaceutically personalized drug delivery and superior osteoregeneration. Scaffolds were developed using biopolymeric blends of gelatin, polyvinyl alcohol and hyaluronic acid and integrated with composite doxycycline/hydroxyapatite/polycaprolactone nanoparticles (DX/HAp/PCL) innovatively via 3D printing. The developed scaffolds were optimized for swelling pattern and in-vitro drug release through tailoring the biphasic microstructure and wet/dry state to attain various pharmaceutical personalization platforms. Freeze-dried scaffolds with nanoparticles reinforcing the core phase (DX/HAp/PCL-LCS-FD) demonstrated favorably controlled swelling, preserved structural integrity and controlled drug release over 28 days. DX/HAp/PCL-LCS-FD featured double-ranged pore size (90.4 ± 3.9 and 196.6 ± 38.8 µm for shell and core phases, respectively), interconnected porosity and superior mechanical stiffness (74.5 ± 6.8 kPa) for osteogenic functionality. Cell spreading analysis, computed tomography and histomorphometry in a rabbit tibial model confirmed osteoconduction, bioresorption, immune tolerance and bone regenerative potential of the original scaffolds, affording complete defect healing with bone tissue. Our findings suggest that the developed platforms promise prominent local drug delivery and bone regeneration.