Functionally graded beta-TCP/PCL nanocomposite scaffolds: in vitro evaluation with human fetal osteoblast cells for bone tissue engineering

Electrospinning technology: a promising approach for tendon-bone interface tissue engineering

The regeneration of tendon-bone interface tissue has become a topic of great interest in recent years. However, the complex nature of this interface has posed challenges in finding suitable solutions. Tissue engineering, with its potential to improve clinical outcomes and play a crucial role in musculoskeletal function, has been increasingly explored for tendon-bone interface regeneration. This review focuses on the research advancements of electrospinning technology in interface tissue engineering. By utilizing electrospinning, researchers have been able to fabricate scaffolds with tailored properties to promote the regeneration and integration of tendon and bone tissues. The review discusses the unique structure and function of the tendon-bone interface, the mechanisms involved in its healing, and the limitations currently faced in achieving successful regeneration. Additionally, it highlights the potential of electrospinning technology in scaffold fabrication and its role in facilitating the development of functional and integrated tendon-bone interface tissues. Overall, this review provides valuable insights into the application of electrospinning technology for tendon-bone interface tissue engineering, emphasizing its significance in addressing the challenges associated with regeneration in this complex interface.

Modular formation of in vitro tumor models for oncological research/therapeutic drug screening

In recognition of the lethal nature of cancer, extensive efforts have been made to understand the mechanistic causation while identifying the effective therapy modality in hope to eradicate cancerous cells with minimal damage to healthy cells. In search of such effective therapeutics, establishing pathophysiologically relevant in vitro models would be of importance in empowering our capabilities of truly identifying those potent ones with significantly reduction of the preclinical periods for rapid translation. In this regard, wealthy progresses have been achieved over past decades in establishing various in vitro and in vivo tumor models. Ideally, the tumor models should maximally recapture the key pathophysiological attributes of their native counterparts. Many of the current models have demonstrated their utilities but also showed some noticeable limitations. This book chapter will briefly review some of the mainstream platforms for in vitro tumor models followed by detailed elaboration on the modular strategies to form in vitro tumor models with complex structures and spatial organization of cellular components. Clearly, with the ability to modulate the building modules it becomes a new trend to form in vitro tumor models following a bottom-up approach, which offers a high flexibility to satisfy the needs for pathophysiological study, anticancer drug screening or design of personalized treatment.

Human Mesenchymal Stem Cells and Innovative Scaffolds for Bone Tissue Engineering Applications

Stem cell-based therapy is a significant topic in regenerative medicine, with a predominant role being played by human mesenchymal stem cells (hMSCs). The hMSCs have been shown to be suitable in regenerative medicine for the treatment of bone tissue. In the last few years, the average lifespan of our population has gradually increased. The need of biocompatible materials, which exhibit high performances, such as efficiency in bone regeneration, has been highlighted by aging. Current studies emphasize the benefit of using biomimetic biomaterials, also known as scaffolds, for bone grafts to speed up bone repair at the fracture site. For the healing of injured bone and bone regeneration, regenerative medicine techniques utilizing a combination of these biomaterials, together with cells and bioactive substances, have drawn a great interest. Cell therapy, based on the use of hMSCs, alongside materials for the healing of damaged bone, has obtained promising results. In this work, several aspects of cell biology, tissue engineering, and biomaterials applied to bone healing/regrowth will be considered. In addition, the role of hMSCs in these fields and recent progress in clinical applications are discussed. Impact Statement The restoration of large bone defects is both a challenging clinical issue and a socioeconomic problem on a global scale. Different therapeutic approaches have been proposed for human mesenchymal stem cells (hMSCs), considering their paracrine effect and potential differentiation into osteoblasts. However, different limitations are still to be overcome in using hMSCs as a therapeutic opportunity in bone fracture repair, including hMSC administration methods. To identify a suitable hMSC delivery system, new strategies have been proposed using innovative biomaterials. This review provides an update of the literature on hMSC/scaffold clinical applications for the management of bone fractures.

Soft Functionally Gradient Materials and Structures - Natural and Manmade: A Review

Functionally gradient materials (FGM) have gradual variations in their properties along one or more dimensions due to local compositional or structural distinctions by design. Traditionally, hard materials (e.g., metals, ceramics) are used to design and fabricate FGMs; however, there is increasing interest in polymer-based soft and compliant FGMs mainly because of their potential application in the human environment. Soft FGMs are ideally suitable to manage interfacial problems in dissimilar materials used in many emerging devices and systems for human interaction, such as soft robotics and electronic textiles and beyond. Soft systems are ubiquitous in everyday lives; they are resilient and can easily deform, absorb energy, and adapt to changing environments. Here, the basic design and functional principles of biological FGMs and their manmade counterparts are discussed using representative examples. The remarkable multifunctional properties of natural FGMs resulting from their sophisticated hierarchical structures, built from a relatively limited choice of materials, offer a rich source of new design paradigms and manufacturing strategies for manmade materials and systems for emerging technological needs. Finally, the challenges and potential pathways are highlighted to leverage soft materials' facile processability and unique properties toward functional FGMs.

Fabrication, Characterization and In Vitro Assessment of Laevistrombus canarium-Derived Hydroxyapatite Particulate-Filled Polymer Composite for Implant Applications

This paper presents the formulation, characterization, and in vitro studies of polymer composite material impregnated with naturally derived hydroxyapatite (HA) particulates for biomedical implant applications. Laevistrombus canarium (LC) seashells (SS) were collected, washed and cleaned, sun-dried for 24 h, and ground into powder particulates. The SS particulates of different weight percentages (0, 10, 20, 30, 40, 50 wt%)-loaded high-density polyethylene (HDPE) composites were fabricated by compression molding for comparative in vitro assessment. A temperature-controlled compression molding technique was used with the operating pressure of 2 to 3 bars for particulate retention in the HDPE matrix during molding. The HDPE/LC composite was fabricated and characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), energy-dispersive X-ray (EDX), differential scanning calorimetry (DSC), and TGA. Mechanical properties such as tensile, compression, flexural, hardness, and also surface roughness were tested as per ASTM standards. Mass degradation and thermal stability of the HDPE/LC composite were evaluated at different temperatures ranging from 10 to 700 °C using thermogravimetric analysis (TGA). The maximum tensile strength was found to be 27 ± 0.5 MPa for 30 wt% HDPE/LC composite. The thermal energy absorbed during endothermic processes was recorded as 71.24 J/g and the peak melting temperature (Tm) was found to be 128.4 °C for the same 30 wt% of HDPE/LC composite specimen. Excellent cell viability was observed during the in vitro biocompatibility study for EtO-sterilized 30 wt% of HDPE/LC composite specimen, except for a report of mild cytotoxicity in the case of higher concentration (50 µL) of the MG-63 cell line. The results demonstrate the potential of the fabricated composite as a suitable biomaterial for medical implant applications.

Load-bearing biodegradable polycaprolactone-poly (lactic-co-glycolic acid)- beta tri-calcium phosphate scaffolds for bone tissue regeneration

A biodegradable scaffold with tissue ingrowth and load-bearing capabilities is required to accelerate the healing of bone defects. However, it is difficult to maintain the mechanical properties as well as biodegradability and porosity (necessary for bone ingrowth) at the same time. Therefore, in the present study, polycaprolactone (PCL) and poly(lactic-co-glycolic acid) (PLGA5050) were mixed in varying ratio and incorporated with 20 wt.% βTCP. The mixture was shaped under pressure into originally non-porous cylindrical constructs. It is envisioned that the fabricated constructs will develop porosity with the time-dependent biodegradation of the polymer blend. The mechanical properties will be sustained since the decrease in mechanical properties associated with the dissolution of the PLGA and the formation of the porous structure will be compensated with the new bone formation and ingrowth. To prove the hypothesis, we have systematically studied the effects of samples composition on the time-dependent dissolution behavior, pore formation, and mechanical properties of the engineered samples, in vitro. The highest initial (of as-prepared samples) values of the yield strength (0.021±0.002 GPa) and the Young's modulus (0.829±0.096 GPa) were exhibited by the samples containing 75 wt.% of PLGA. Increase of the PLGA concentration from 25 wt.% to 75 wt.% increased the rate of biodegradation by a factor of 3 upon 2 weeks in phosphate buffered saline (1× PBS). The overall porosity and the pore sizes increased with the dissolution time indicating that the formation of in-situ pores can indeed enable the migration of cells followed by vascularization and bone growth.

Multimaterial Segmented Fiber Printing for Gradient Tissue Engineering

IMPACT STATEMENT

This study introduces a segmented three-dimensional printing methodology to create multimaterial porous scaffolds with discrete gradients and controlled distribution of compositions. This methodology can be adapted for the preparation of complex, multimaterial scaffolds with hierarchical structures and mechanical integrity useful in tissue engineering.

Controlling Growth and Osteogenic Differentiation of Osteoblasts on Microgrooved Polystyrene Surfaces

Surface topography is increasingly being recognized as an important factor to control the response of cells and tissues to biomaterials. In the current study, the aim was to obtain deeper understanding of the effect of microgrooves on shape and orientation of osteoblast-like cells and to relate this effect to their proliferation and osteogenic differentiation. To this end, two microgrooved polystyrene (PS) substrates, differing in the width of the grooves (about 2 μm and 4 μm) and distance between individual grooves (about 6 μm and 11 μm, respectively) were fabricated using a combination of photolithography and hot embossing. MG-63 human osteosarcoma cells were cultured on these microgrooved surfaces, with unpatterned hot-embossed PS substrate as a control. Scanning electron- and fluorescence microscopy analyses showed that on patterned surfaces, the cells aligned along the microgrooves. The cells cultured on 4 μm-grooves / 11 μm-ridges surface showed a more pronounced alignment and a somewhat smaller cell area and cell perimeter as compared to cells cultured on surface with 2 μm-grooves / 6 μm-ridges or unpatterned PS. PrestoBlue analysis and quantification of DNA amounts suggested that microgrooves used in this experiment did not have a strong effect on cell metabolic activity or proliferation. However, cell differentiation towards the osteogenic lineage was significantly enhanced when MG-63 cells were cultured on the 2/6 substrate, as compared to the 4/11 substrate or unpatterned PS. This effect on osteogenic differentiation may be related to differences in cell spreading between the substrates.

Repair of articular osteochondral defects of the knee joint using a composite lamellar scaffold

Objectives

The major problem with repair of an articular cartilage injury is the extensive difference in the structure and function of regenerated, compared with normal cartilage. Our work investigates the feasibility of repairing articular osteochondral defects in the canine knee joint using a composite lamellar scaffold of nano-ß-tricalcium phosphate (ß-TCP)/collagen (col) I and II with bone marrow stromal stem cells (BMSCs) and assesses its biological compatibility.

Methods

The bone–cartilage scaffold was prepared as a laminated composite, using hydroxyapatite nanoparticles (nano-HAP)/collagen I/copolymer of polylactic acid–hydroxyacetic acid as the bony scaffold, and sodium hyaluronate/poly(lactic-co-glycolic acid) as the cartilaginous scaffold. Ten-to 12-month-old hybrid canines were randomly divided into an experimental group and a control group. BMSCs were obtained from the iliac crest of each animal, and only those of the third generation were used in experiments. An articular osteochondral defect was created in the right knee of dogs in both groups. Those in the experimental group were treated by implanting the composites consisting of the lamellar scaffold of ß-TCP/col I/col II/BMSCs. Those in the control group were left untreated.

Results

After 12 weeks of implantation, defects in the experimental group were filled with white semi-translucent tissue, protruding slightly over the peripheral cartilage surface. After 24 weeks, the defect space in the experimental group was filled with new cartilage tissues, finely integrated into surrounding normal cartilage. The lamellar scaffold of ß-TCP/col I/col II was gradually degraded and absorbed, while new cartilage tissue formed. In the control group, the defects were not repaired.

Conclusion

This method can be used as a suitable scaffold material for the tissue-engineered repair of articular cartilage defects.

Cite this article: Bone Joint Res 2015;4:56–64

Laminin Functionalized Biomimetic Nanofibers For Nerve Tissue Engineering

Large-gap peripheral nerve injuries present a significant challenge for nerve regeneration due to lack of suitable grafts, insufficient cell penetration, and repair. Biomimetic nanofibrous scaffolds, functionalized on the surface with extracellular matrix proteins, can lead to novel therapies for repair and regeneration of damaged peripheral nerves. Here, nanofibrous scaffolds electrospun from blends of poly(caprolactone) (PCL) and chitosan were fabricated. Taking advantage of the amine groups on the chitosan, the surface of the scaffolds were functionalized with laminin by carbodiimide based crosslinking. Crosslinking allowed laminin to be attached to the surfaces of the PCL-chitosan nanofibers at relatively high concentrations that were not possible using conventional adsorption methods. The nanofibrous meshes were tested for wettability, mechanical properties and cell attachment and proliferation. Blending of chitosan with PCL provided more favorable surfaces for attachment of Schwann cells due to the reduction of the contact angle in comparison to neat PCL. Proliferation rates of Schwann cells grown on PCL-chitosan scaffolds with crosslinked laminin were significantly higher than the rates for PCL-chitosan nanofibrous matrices with adsorbed laminin. PCL-chitosan scaffolds with modified surfaces via crosslinking of laminin could potentially serves as versatile substrates with excellent mechanical and surface properties for in vivo cell delivery for nerve tissue engineering applications.

Radially and axially graded multizonal bone graft substitutes targeting critical-sized bone defects from polycaprolactone/hydroxyapatite/tricalcium phosphate

Repair and regeneration of critical sized defects via the utilization of polymeric bone graft substitutes are challenges. Here, we introduce radially and axially graded multizonal bone graft substitutes fabricated from polycaprolactone (PCL), and PCL biocomposites with osteoconductive particles, that is, hydroxyapatite (HA), and β-tricalcium phosphate (TCP). The novel bone graft substitutes should provide a greater degree of freedom to the orthopedic surgeon especially for repair of critically sized bone defects. The modulus of the graft substitute could be tailored in the axial direction upon the systematic variation of the HA/TCP concentration, while in the radial direction the bone graft substitute consisted of an outer layer with high stiffness, encapsulating a softer core with greater porosity. The biocompatibility of the bone graft substitutes was investigated using in vitro culturing of human bone marrow-derived stromal cells followed by the analysis of cell proliferation and differentiation rates. The characterization of the tissue constructs included the enzymatic alkaline phosphates (ALP) activity, microcomputed tomography imaging, and polymerase chain reaction analysis involving the expressions of bone markers, that is, Runx2, ALP, collagen type I, osteopontin, and osteocalcin, overall demonstrating the differentiation of bone marrow derived stem cells (BMSCs) via osteogenic lineage and formation of mineralized bone tissue.

Vascularized bone tissue engineering: approaches for potential improvement

Significant advances have been made in bone tissue engineering (TE) in the past decade. However, classical bone TE strategies have been hampered mainly due to the lack of vascularization within the engineered bone constructs, resulting in poor implant survival and integration. In an effort toward clinical success of engineered constructs, new TE concepts have arisen to develop bone substitutes that potentially mimic native bone tissue structure and function. Large tissue replacements have failed in the past due to the slow penetration of the host vasculature, leading to necrosis at the central region of the engineered tissues. For this reason, multiple microscale strategies have been developed to induce and incorporate vascular networks within engineered bone constructs before implantation in order to achieve successful integration with the host tissue. Previous attempts to engineer vascularized bone tissue only focused on the effect of a single component among the three main components of TE (scaffold, cells, or signaling cues) and have only achieved limited success. However, with efforts to improve the engineered bone tissue substitutes, bone TE approaches have become more complex by combining multiple strategies simultaneously. The driving force behind combining various TE strategies is to produce bone replacements that more closely recapitulate human physiology. Here, we review and discuss the limitations of current bone TE approaches and possible strategies to improve vascularization in bone tissue substitutes.