Analysis of 3D bone ingrowth into polymer scaffolds via micro-computed tomography imaging

Comparison of Biocompatibility of 3D-Printed Ceramic and Titanium in Micropig Ankle Hemiarthroplasty

BACKGROUND

Ankle arthritis is a common degenerative disease that progresses as cartilage damage in the lower tibia and upper talus progresses, resulting in loss of joint function. In addition to typical arthritis, there is also structural bone loss in the talus due to diseases such as talar avascular necrosis. Total talus replacement surgery is the procedure of choice in end-stage ankle arthritis and consists of a tibial, talar component and an insert. However, in cases of severe cartilage and bone damage to the talar bone with less damage to the tibial cartilage, a talar component hemiarthroplasty may be considered. Although the application of total talus replacement surgery using ceramics has been studied, reports on the application of metal 3D printing technology are limited. We aimed to investigate the feasibility of partial talar components using ceramic and titanium 3D printing technology in terms of biocompatibility and stability through animal experiments.

METHODS

Preoperative 3D CT was acquired and converted to STL files to fabricate a partial talus component for ankle hemiarthroplasty using ceramic and titanium. Six minipigs with an average age of 17 months were implanted with three ceramic (C-group) and three titanium talar components (T-group) in the hind limb ankle joint. The surgery was performed under anesthesia in a sterile operating room and was performed by two experienced foot and ankle specialist orthopedic surgeons. Blood analysis and CT were performed before surgery and every month for 3 months after surgery to assess the extent of inflammatory response and physical stability, sacrifices were performed 3 months after surgery, and H&E staining and micro-CT analysis were performed to compare histological biocompatibility. A grading score was calculated to semi-quantitative assess and compare the two groups.

RESULTS

In the postsurgical evaluation, blood analysis revealed that both groups had increased white blood cell counts on the postoperative day after surgery. The white blood cell count increased more in the titanium group (1.85-fold) than in the ceramic group (1.45-fold). After 3 months, all values normalized. During the study, CT analysis confirmed that all artificial samples were displaced from their initial positions. In micro-CT analysis, the adhesive tissue score of the ceramic artificial sample was better than that of the titanium sample (average threshold = 3027.18 ± 405.92). In histologic and grading scores for the inflammatory reactions, the average inflammation indices of the ceramic and titanium groups were 2.0 and 1.21, respectively. Also, the average grade score confirmed based on the results of fibrous tissue proliferation and new blood vessels was 18.4 in the ceramic application group and 12.3 in the titanium application group.

CONCLUSIONS

In conclusion, both titanium and ceramics have excellent biocompatibility for artificial joints, and ceramic materials can be used as novel artificial joints. Further research on the strength and availability of these ceramics is required.

Characterization of Biocompatibility of Functional Bioinks for 3D Bioprinting

Three-dimensional (3D) bioprinting with suitable bioinks has become a critical tool for fabricating 3D biomimetic complex structures mimicking physiological functions. While enormous efforts have been devoted to developing functional bioinks for 3D bioprinting, widely accepted bioinks have not yet been developed because they have to fulfill stringent requirements such as biocompatibility and printability simultaneously. To further advance our knowledge of the biocompatibility of bioinks, this review presents the evolving concept of the biocompatibility of bioinks and standardization efforts for biocompatibility characterization. This work also briefly reviews recent methodological advances in image analyses to characterize the biocompatibility of bioinks with regard to cell viability and cell-material interactions within 3D constructs. Finally, this review highlights a number of updated contemporary characterization technologies and future perspectives to further advance our understanding of the biocompatibility of functional bioinks for successful 3D bioprinting.

Morphological and Tissue Characterization with 3D Reconstruction of a 350-Year-Old Austrian Ardea purpurea Glacier Mummy

Glaciers are dwindling archives, releasing animal mummies preserved in the ice for centuries due to climate changes. As preservation varies, residual soft tissues may differently expand the biological information content of such mummies. DNA studies have proven the possibility of extracting and analyzing DNA preserved in skeletal residuals and sediments for hundreds or thousands of years. Paleoradiology is the method of choice as a non-destructive tool for analyzing mummies, including micro-computed tomography (micro-CT) and magnetic resonance imaging (MRI). Together with radiocarbon dating, histo-anatomical analyses, and DNA sequencing, these techniques were employed to identify a 350-year-old Austrian Ardea purpurea glacier mummy from the Ötztal Alps. Combining these techniques proved to be a robust methodological concept for collecting inaccessible information regarding the structural organization of the mummy. The variety of methodological approaches resulted in a distinct picture of the morphological patterns of the glacier animal mummy. The BLAST search in GenBank resulted in a 100% and 98.7% match in the cytb gene sequence with two entries of the species Purple heron (Ardea purpurea; Accession number KJ941160.1 and KJ190948.1) and a 98% match with the same species for the 16 s sequence (KJ190948.1), which was confirmed by the anatomic characteristics deduced from micro-CT and MRI.

Semantic Segmentation of Micro-CT Images to Analyze Bone Ingrowth into Biodegradable Scaffolds

The healing of bone fractures is a complex and well-orchestrated physiological process, but normal healing is compromised when the fracture is large. These large non-union fractures often require a template with surgical intervention for healing. The standard treatment, autografting, has drawbacks such as donor site pain and limited availability. Biodegradable scaffolds developed using biomaterials such as bioactive glass are a potential solution. Investigation of bone ingrowth into biodegradable scaffolds is an important aspect of their development. Micro-CT (μ-CT) imaging is widely used to evaluate and quantify tissue ingrowth into scaffolds in 3D. Existing segmentation techniques have low accuracy in differentiating bone and scaffold, and need improvements to accurately quantify the bone in-growth into the scaffold using μ-CT scans. This study proposes a novel 3-stage pipeline for better outcome. The first stage of the pipeline is based on a convolutional neural network for the segmentation of the scaffold, bone, and pores from μ-CT images to investigate bone ingrowth. A 3D rigid image registration procedure was employed in the next stage to extract the volume of interest (VOI) for the analysis. In the final stage, algorithms were developed to quantitatively analyze bone ingrowth and scaffold degradation. The best model for segmentation produced a dice similarity coefficient score of 90.1, intersection over union score of 83.9, and pixel accuracy of 93.1 for unseen test data.

Quality control methods in musculoskeletal tissue engineering: from imaging to biosensors

Tissue engineering is rapidly progressing toward clinical application. In the musculoskeletal field, there has been an increasing necessity for bone and cartilage replacement. Despite the promising translational potential of tissue engineering approaches, careful attention should be given to the quality of developed constructs to increase the real applicability to patients. After a general introduction to musculoskeletal tissue engineering, this narrative review aims to offer an overview of methods, starting from classical techniques, such as gene expression analysis and histology, to less common methods, such as Raman spectroscopy, microcomputed tomography, and biosensors, that can be employed to assess the quality of constructs in terms of viability, morphology, or matrix deposition. A particular emphasis is given to standards and good practices (GXP), which can be applicable in different sectors. Moreover, a classification of the methods into destructive, noninvasive, or conservative based on the possible further development of a preimplant quality monitoring system is proposed. Biosensors in musculoskeletal tissue engineering have not yet been used but have been proposed as a novel technology that can be exploited with numerous advantages, including minimal invasiveness, making them suitable for the development of preimplant quality control systems.

Calcium-Enriched Nanofibrillated Cellulose/Poloxamer in-situ Forming Hydrogel Scaffolds as a Controlled Delivery System of Raloxifene HCl for Bone Engineering

PURPOSE

TEMPO-oxidized nanofibrillated cellulose (TONFC) originating from an agricultural waste (sugar cane) was utilized to prepare injectable in-situ forming hydrogel scaffolds (IHS) for regenerative medicine.

METHODS

TONFC was prepared and characterized for its morphology and chemical structure using TEM and FT-IR, respectively. The cold method was applied to prepare hydrogels. Various concentrations of poloxamer 407 were added to the prepared TONFC (0.5%w/w). Different sources of calcium, Fujicalin® (DCP) or hydroxyapatite (TCP), were used to formulate the aimed calcium-enriched raloxifene hydrochloride-loaded IHS. Gelation temperature, drug content, injectability and in-vitro drug release were evaluated along with the morphological characters. Cytocompatibility studies and tissue regeneration properties were assessed on Saos-2 cells.

RESULTS

TEM photograph of TONFC showed fibrous nanostructure. The selected formulation "Ca-IHS4" composed of TONFC+15% P407+10% TCP showed the most prolonged release pattern for 12 days with the least burst effect (about 25% within 24 h). SEM micro-photographs of the in-situ formed scaffolds showed a highly porous 3D structure. Cytocompatibility studies of formulation "Ca-IHS4" revealed the biocompatibility as well as improved cell adhesion, alkaline phosphatase enzyme activity and calcium ion deposition.

CONCLUSION

The outcomes suggest that Ca-IHS4 presents a simple, safe-line and non-invasive strategy for bone regeneration.

Two-Photon Fluorescence Microscopy and Applications in Angiogenesis and Related Molecular Events

The role of angiogenesis in health and disease have gained considerable momentum in recent years. Visualizing angiogenic patterns and associated events of surrounding vascular beds in response to therapeutic and laboratory-grade biomolecules have become a commonplace in regenerative medicine and the biosciences. To aid imaging investigations in angiogenesis, the two-photon excitation fluorescence microscopy (2PEF), or multiphoton fluorescence microscopy is increasingly utilized in scientific investigations. The 2PEF microscope confers several distinct imaging advantages over other fluorescence excitation microscopy techniques - for the observation of in-depth, three-dimensional vascularity in a variety of tissue formats, including fixed tissue specimens and in vivo vasculature in live specimens. Understanding morphological and subcellular changes that occur in cells and tissues during angiogenesis will provide insights to behavioral responses in diseased states, advance the engineering of physiologically-relevant tissue models and provide biochemical clues for the design of therapeutic strategies. We review the applicability and limitations of the 2PEF microscope on the biophysical and molecular-level signatures of angiogenesis in various tissue models. Imaging techniques and strategies for best practices in 2PEF microscopy will be reviewed.

Additive Manufacturing of Material Scaffolds for Bone Regeneration: Toward Application in the Clinics

Additive manufacturing (AM) allows the fabrication of customized bone scaffolds in terms of shape, pore size, material type and mechanical properties. Combined with the possibility to obtain a precise 3D image of the bone defects using computed tomography or magnetic resonance imaging, it is now possible to manufacture implants for patient-specific bone regeneration. This paper reviews the state-of-the-art of the different materials and AM techniques used for the fabrication of 3D-printed scaffolds in the field of bone tissue engineering. Their advantages and drawbacks are highlighted. For materials, specific criteria, were extracted from a literature study: biomimetism to native bone, mechanical properties, biodegradability, ability to be imaged (implantation and follow-up period), histological performances and sterilization process. AM techniques can be classified in three major categories: extrusion-based, powder-based and liquid-base. Their price, ease of use and space requirement are analyzed. Different combinations of materials/AM techniques appear to be the most relevant depending on the targeted clinical applications (implantation site, presence of mechanical constraints, temporary or permanent implant). Finally, some barriers impeding the translation to human clinics are identified, notably the sterilization process.

In Vitro and In Vivo Evaluation of Nanostructured Biphasic Calcium Phosphate in Granules and Putty Configurations

Synthetic biphasic calcium phosphate (BCP) granules and powder are biocompatible biomaterials with a well-known capacity for osteoconduction, presenting very satisfactory clinical and histological results. It remains unanswered if the putty configuration impacts the biological response to the material. In this study, we aimed to compare the cytocompatibility and biocompatibility of nanostructured BCP in the putty configuration (moldable nanostructured calcium phosphate, MnCaP) on the healing of critical-sized bone defects (8 mm) in rat calvaria. Cytocompatibility was determined through the viability of fibroblast cells (V-79) to the extracts of different concentrations of MnCaP. Forty-five Wistar rats were randomly divided into three groups (n = 15)-clot, MnCaP, and commercial biphasic calcium phosphate in granules configurations (Nanosynt®)-and subdivided into three experimental periods (1, 3, and 6 months). Histological, histomorphometric, and microtomographic analyses allowed the evaluation of newly formed bone, residual biomaterial, and connective tissue. The in vitro evaluation showed that MnCaP was cytocompatible. The histomorphometric results showed that the Nanosynt® group granted the highest new-formed bone values at six months (p < 0.05), although the biomaterial volume did not differ between groups. The putty configuration was easier to handle, and both configurations were biocompatible and osteoconductive, presented similar biosorption rates, and preserved the calvaria architecture.

Physicochemical properties and cytocompatibility assessment of non-degradable scaffolds for bone tissue engineering applications

Bone is a dynamic tissue with an amazing but yet limited capacity of self-healing. Bone is the second most transplanted tissue in the world and there is a huge need for bone grafts and substitutes which lead to a decrease in bone banks donors. In this study, we developed three-dimensional scaffolds based on Ti₆Al₄V, ZrO₂ and PEEK targeting bone tissue engineering applications. Experimental mechanical compressive tests and finite element analyses were carried out to study the mechanical performance of the scaffolds. Overall, the scaffolds presented different hydrophilicity properties and a reduced elastic modulus when compared with the corresponding solid materials which can in some extension minimize the phenomenon of stress shielding. The ability as a scaffold material for bone tissue regeneration applications was evaluated in vitro by seeding human osteosarcoma (SaOS-2) cells onto the scaffolds. Then, the successful culture of SaOS-2 cells on developed scaffolds was monitored by assessment of cell's viability, proliferation and alkaline phosphatase (ALP) activity up to 14 days of culturing. The in vitro results revealed that Ti₆Al₄V, ZrO₂ and PEEK scaffolds were cytocompatible allowing the successful culture of an osteoblastic cell line, suggesting their potential application in bone tissue engineering. Statement of Significance. The work presented is timely and relevant since it gathers both the mechanical and cellular study of non-degradable cellular structures with the potential to be used as bone scaffolds. This work allow to investigate three possible bone scaffolds solutions which exhibit a significantly reduced elastic modulus when compared with conventional solid materials. While it is generally accepted that the Ti₆Al₄V, ZrO₂ and PEEK are candidates for such applications a further study of their features and their comparison is extremely important for a better understanding of their potential.

Processed Bamboo as a Novel Formaldehyde-Free High-Performance Furniture Biocomposite

We used an innovative approach involving hot pressing, low energy consumption, and no adhesive to transform bamboo biomass into a natural sustainable fiber-based biocomposite for structural and furniture applications. Analyses showed strong internal bonding through mechanical "nail-like" nano substances, hydrogen, and ester and ether bonds. The biocomposite encompasses a 10-fold increase in internal bonding strength with improved water resistance, fire safety, and environmentally friendly properties as compared to existing furniture materials using hazardous formaldehyde-based adhesives. As compared to natural bamboo material, this new biocomposite has improved fire and water resistance, while there is no need for toxic adhesives (mostly made from formaldehyde-based resin), which eases the concern of harmful formaldehyde-based VOC emission and ensures better indoor air quality. This surpasses existing structural and furniture materials made by synthetic adhesives. Interestingly, our approach can 100% convert discarded bamboo biomass into this biocomposite, which represents a potentially cost reduction alternative with high revenue. The underlying fragment riveting and cell collapse binding are obviously a new technology approach that offers an economically and sustainable high-performance biocomposite that provides solutions to structural and furniture materials bound with synthetic adhesives.

Scaffolds and coatings for bone regeneration

Bone tissue has an astonishing self-healing capacity yet only for non-critical size defects (<6 mm) and clinical intervention is needed for critical-size defects and beyond that along with non-union bone fractures and bone defects larger than critical size represent a major healthcare problem. Autografts are, still, being used as preferred to treat large bone defects. Mostly, due to the presence of living differentiated and progenitor cells, its osteogenic, osteoinductive and osteoconductive properties that allow osteogenesis, vascularization, and provide structural support. Bone tissue engineering strategies have been proposed to overcome the limited supply of grafts. Complete and successful bone regeneration can be influenced by several factors namely: the age of the patient, health, gender and is expected that the ideal scaffold for bone regeneration combines factors such as bioactivity and osteoinductivity. The commercially available products have as their main function the replacement of bone. Moreover, scaffolds still present limitations including poor osteointegration and limited vascularization. The introduction of pores in scaffolds are being used to promote the osteointegration as it allows cell and vessel infiltration. Moreover, combinations with growth factors or coatings have been explored as they can improve the osteoconductive and osteoinductive properties of the scaffold. This review focuses on the bone defects treatments and on the research of scaffolds for bone regeneration. Moreover, it summarizes the latest progress in the development of coatings used in bone tissue engineering. Despite the interesting advances which include the development of hybrid scaffolds, there are still important challenges that need to be addressed in order to fasten translation of scaffolds into the clinical scenario. Finally, we must reflect on the main challenges for bone tissue regeneration. There is a need to achieve a proper mechanical properties to bear the load of movements; have a scaffolds with a structure that fit the bone anatomy.

3D printing for tissue engineering in otolaryngology

Airway and other head and neck disorders affect hundreds of thousands of patients each year and most require surgical intervention. Among these, congenital deformity that affects newborns is particularly serious and can be life-threatening. In these cases, reconstructive surgery is resolutive but bears significant limitations, including the donor site morbidity and limited available tissue. In this context, tissue engineering represents a promising alternative approach for the surgical treatment of otolaryngologic disorders. In particular, 3D printing coupled with advanced imaging technologies offers the unique opportunity to reproduce the complex anatomy of native ear, nose, and throat, with its import in terms of functionality as well as aesthetics and the associated patient well-being. In this review, we provide a general overview of the main ear, nose and throat disorders and focus on the most recent scientific literature on 3D printing and bioprinting for their treatment.

Comparison of structure and composition of a fossil Champsosaurus vertebra with modern Crocodylidae vertebrae: A multi-instrumental approach

Information on the adaptation of bone structures during evolution is rare since histological data are limited. Micro- and nano-computed tomography of a fossilized vertebra from Champsosaurus sp., which has an estimated age of 70-73 million years, revealed lower porosity and higher bone density compared to modern Crocodylidae vertebrae. Mid-infrared reflectance and energy dispersive X-ray mapping excluded a petrification process, and demonstrated a typical carbonate apatite distribution, confirming histology in light- and electron microscopy of the preserved vertebra. As a consequence of this evolutionary process, the two vertebrae of modern Crocodylidae show reduced overall stiffness in the finite element analysis simulation compared to the fossilized Champsosaurus sp. vertebra, with predominant stiffness along the longitudinal z-axes.

Nasal tip plasty using three-dimensional printed polycaprolactone (Smart Ball®)

BACKGROUND

Rhinoplasty is one of the most commonly performed cosmetic surgery procedures. Most Asians desire elevation of their relatively flat nasal dorsum and tip to make them appear more prominent. This study introduces a simple method of nasal tip plasty using three-dimensional (3D)-printed polycaprolactone (PCL) (Smart Ball®), which provides the required length and volume for this purpose and enables the creation of a nasal tip of the desired shape in a safe and simple manner.

METHODS

Between September 2014 and May 2017, 22 patients participated in a survey to assess postoperative satisfaction levels. Additionally, three plastic surgeons compared patients' pre- and 1-year postoperative photographs to evaluate the results. All patients underwent 2- to 4-year postoperative follow-up.

RESULTS

Levels of subjective satisfaction among patients were 3.59, 3.50, 3.82, 3.73, 3.55, and 3.82 for each of the 6 categories evaluated, with a mean of 3.67/4 points, indicating high satisfaction levels. The mean plastic surgeon-reported score for the 22 patients was 4.47/5 points, which also indicates highly successful outcomes. Postoperative nasal tip rotation and tip projection were ideal in most patients.

CONCLUSION

Our novel method using 3D-printed PCL (Smart Ball®) provides the optimal length and volume required for nasal tip plasty and enables the creation of a nasal tip of the desired shape, in a safe and simple manner. An advantage of our method is that it retains the original nasal structure in contrast to structural changes observed with the use of conventional methods.

Synchrotron radiation techniques boost the research in bone tissue engineering

X-ray Synchrotron radiation-based techniques, in particular Micro-tomography and Micro-diffraction, were exploited to investigate the structure of bone deposited in vivo within a porous ceramic scaffold. Bone formation was studied by implanting Mesenchymal Stem Cell (MSC) seeded ceramic scaffolds in a mouse model. Osteoblasts derived from the seeded MSC and from differentiation of cells migrated within the scaffold together with the blood vessels, deposited within the scaffold pores an organic collagenous matrix on which a precursor mineral amorphous liquid-phase, containing Ca++ and PO₄^-- crystallized filling the gaps between the collagen molecules. Histology offered a valid instrument to investigate the engineered tissue structure, but, unfortunately, limited itself to a macroscopic analysis. The evolution of the X-ray Synchrotron radiation-based techniques and the combination of micro X-ray diffraction with X-ray phase-contrast imaging enabled to study the dynamic of the structural and morphological changes occurring during the new bone deposition, biomineralization and vascularization. In fact, the unique features of Synchrotron radiation, is providing the high spatial resolution probe which is necessary for the study of complex materials presenting heterogeneity from micron-scale to meso- and nano-scale. Indeed, this is the occurrence in the heterogeneous and hierarchical bone tissue where an organic matter, such as the collagenous matrix, interacts with mineral nano-crystals to generate a hybrid multiscale biomaterial with unique physical properties. In this framework, the use of advanced synchrotron radiation techniques allowed to understand and to clarify fundamental aspects of the bone formation process within the bioceramic, i.e. biomineralization and vascularization, including to obtain deeper knowledge on bone deposition, mineralization and reabsorption in different health, aging and pathological conditions. In this review we present an overview of the X-ray Synchrotron radiation techniques and we provide a general outlook of their applications on bone Tissue Engineering, with a focus on our group work. STATEMENT OF SIGNIFICANCE: Synchrotron Radiation techniques for Tissue Engineering In this review we report recent applications of X-ray Synchrotron radiation-based techniques, in particular Microtomography and Microdiffraction, to investigations on the structure of ceramic scaffolds and bone tissue regeneration. Tissue engineering has made significant advances in bone regeneration by proposing the use of mesenchymal stem cells in combination with various types of scaffolds. The efficacy of the biomaterials used to date is not considered optimal in terms of resorbability and bone formation, resulting in a poor vascularization at the implant site. The review largely based on our publications in the last ten years could help the study of the regenerative model proposed. We also believe that the new imaging technologies we describe could be a starting point for the development of additional new techniques with the final aim of transferring them to the clinical practice.

Section Plane Effects on Morphometric Values of Microcomputed Tomography

Objectives

Histomorphometry is the established gold standard for inspection of trabecular microstructures in biomaterial research. However, microcomputed tomography can provide images from the perspective of various section planes. The aim of the present study was to evaluate the effects of different section planes, which may cause bias in two-dimensional morphometry, on the morphometric values of microcomputed tomography.

Methods

A socket preservation technique was performed on the extracted premolar area of 4 beagle dogs. After an 8-week healing period, a total of 16 specimens were obtained and analyzed with conventional histomorphometry and microtomographic morphometry. Using the original images of the histologic specimens for comparison, the most similar tomographic image was selected by trial and error. Then, the section plane was then moved with ±79 μm parallel offsets and rotated ±10° around the center from the occlusal view. The images were compared in terms of bone, graft, and noncalcified area, and the concordance correlation coefficient (CCC) was calculated.

Results

There was a high CCC in the comparison between histomorphometric images and the most similar microtomographic images. However, the CCC value was low in the comparisons with both parallel movement and rotation. Our results demonstrate that the sectioning plane has a significant effect on measurements.

Conclusion

Two-dimensional morphometric values for biomaterial research should be interpreted with caution, and the simultaneous use of complementary 3-dimensional tools is recommended.

Healing of osteoporotic bone defects by micro-/nano-structured calcium phosphate bioceramics

The micro-/nano-structured calcium phosphate bioceramic exhibited a higher new bone substitution rate in an osteoporotic bone defect rat model.

A Comparison of 1- and 3.2-MHz Low-Intensity Pulsed Ultrasound on Osteogenesis on Porous Titanium Alloy Scaffolds: An In Vitro and In Vivo Study

OBJECTIVES

Low-intensity pulsed ultrasound (LIPUS) combined with porous scaffolds can be used as a new therapy to treat bone defect repair. The aim of this study was to evaluate the effects of 1 and 3.2 MHz LIPUS on osteogenesis on porous Ti64 alloy scaffolds for both in vitro and in vivo studies.

METHODS

Scaffolds were randomly divided into the high-frequency ultrasound group, low-frequency ultrasound group, and control group. Mouse pre-osteoblast cells were cultured with porous Ti-6Al-4V scaffolds in vitro to evaluate cell proliferation and differentiation. In addition, scaffolds were implanted into rabbit mandibular defects in vivo. The effects of LIPUS on bone regeneration were evaluated by observing the micro-computed tomography (micro-CT), toluidine blue staining, and von Kossa staining.

RESULTS

The results revealed no significant difference in the cell counting kit-8 values between the ultrasound groups and control groups (P > .05). Compared with the control group, ultrasound promoted alkaline phosphatase activity and osteocalcin levels of the cells on the scaffolds (P < .05), but there was no significant difference between the two frequencies. In addition, histomorphologic analyses revealed that the volume and amount of new bone formation increased and that bone maturity improved in the ultrasound groups compared with the control group, but no significant difference was noted between the two frequencies.

CONCLUSIONS

Under the present experimental conditions, LIPUS promoted osteoblast differentiation and promoted bone maturity on porous Ti64 scaffolds. No significant differences were noted between the two frequencies.

Stabilization of Microrobot Motion Characteristics in Liquid Media

Magnetically actuated microrobot in a liquid media is faced with the problem of head-tilting reaction caused by its hydrodynamic structure and its speed while moving horizontally. When the instance microrobot starts a lateral motion, the drag force acting on it increases. Thus, the microrobot is unable to move parallel to the surface due to the existence of drag force that cannot be neglected, particularly at high speeds such as >5 mm/s. The effect of it scales exponentially at different speeds and the head-tilting angle of the microrobot changes relative to the reference surface. To the best of our knowledge, there is no prior study on this problem, and no solution has been proposed so far. In this study, we developed and experimented with 3 control models to stabilize microrobot motion characteristics in liquid media to achieve accurate lateral locomotion. The microrobot moves in an untethered manner, and its localization is carried out by a neodymium magnet (grade N48) placed inside its polymer body. This permanent magnet is called a carrier-magnet. The fabricated microrobot is levitated diamagnetically using a pyrolytic graphite placed under it and an external permanent magnet, called a lifter-magnet (grade N48), aligned above it. The lifter-magnet is attached to a servo motor mechanism which can control carrier-magnet orientation along with roll and pitch axes. Controlling the angle of this servo motor, together with the lifter-magnet, allowed us to cope with the head-tilting reaction instantly. Based on the finite element method (FEM), analyses that were designed according to this experimental setup, the equations giving the relation of microrobot speed with servo motor angle along with the microrobot head-tilting angle with servo motor angle, were derived. The control inputs were obtained by COMSOL® (version 5.3, COMSOL Inc., Stockholm, Sweden). Using these derived equations, the rule-based model, laser model, and hybrid model techniques were proposed in this study to decrease the head-tilting angle. Motion control algorithms were applied in di-ionized water medium. According to the results for these 3 control strategies, at higher speeds (>5 mm/s) and 5 mm horizontal motion trajectory, the average head-tilting angle was reduced to 2.7° with the ruled-based model, 1.1° with the laser model, and 0.7° with the hybrid model.

RhBMP-2 and concomitant rapid material degradation synergistically promote bone repair and regeneration with collagen-hydroxyapatite nanocomposites

The effective treatment of bone defects is still a great challenge in clinical practice. Synthetic bone-grafting substitutes of composition and structure analogous to bone as well as incorporated with growth factors are considered to be a promising solution. In this study, a collagen-hydroxyapatite (CHA) nanocomposite scaffold was developed by collagen self-assembly with simultaneous HA synthesis. The physicochemical properties such as morphology, inorganic phase, thermal decomposition, specific surface area and pore size distribution were characterized. The osteogenicity of CHA in the absence or presence of recombinant human bone morphogenetic protein-2 (rhBMP-2) was assessed both by cell culturing and animal implantation experiments. The gene expression results showed that the osteogenic differentiation capacity of rat bone mesenchymal stem cells (rBMSCs) has been enhanced both by CHA and rhBMP-2. The efficient bone regeneration of femoral defects in rabbits was achieved with CHA and CHA pre-absorbed rhBMP-2 (CHA/B), confirmed by micro-computed tomography measurements, histological observation and immunohistochemical analyses. The CHA nanocomposite was completely degraded within 8 weeks and replaced by new bone. It was found that rhBMP-2 not only accelerated and enhanced bone formation, but also expedited the degradation of CHA. It is believed that the rhBMP-2 and concomitant rapid material degradation synergistically promote bone repair and regeneration with CHA. The biodegradation behavior of CHA in the presence of rhBMP-2 can be further investigated to gain an in-depth understanding of the complex interplays among biomaterials, growth factors and their target cells. The relevant knowledge will facilitate the search for a reasonable, safe and efficient methodology for the introduction of growth factors to biomaterials so as to achieve satisfactory tissue regeneration.

Results of Cemented vs Cementless Primary Total Knee Arthroplasty Using the Same Implant Design

BACKGROUND

Although cemented total knee arthroplasty (TKA) continues to be the gold standard, there are patient populations with higher failure rates with cemented TKAs such as the obese, morbidly obese, and younger active males. Cementless TKA usage continues to increase because of the potential benefits of long-term biologic fixation similar to the rise in cementless total hip arthroplasty. The purpose of this study was to evaluate the clinical and radiographic results of cementless TKA using a novel highly porous cementless tibial baseplate.

METHODS

This was a retrospective matched case-control study of 400 primary TKAs comparing cementless vs cemented TKAs using the same implant design (Stryker Triathlon; Stryker Inc, Mahwah, NJ). Two-hundred patients with a mean age of 64 years (range 42-88 years) and body mass index (BMI) of 33.9 kg/m² (range 19.7-57.1 kg/m²) were matched to 200 primary cemented TKA patients with a mean age of 64 years (range 43-87 years) and BMI of 33.1 kg/m² (range 22.2-53.2 kg/m²). The mean follow-up in the cementless group was 2.4 years (range 2-3.5 years) and in the cemented group was 5.3 years (range 2-10.9 years). Clinical and radiographic analyses were evaluated. Statistical analysis was performed using the Microsoft Excel, version 15.21.1.

RESULTS

There was no statistical difference in age, BMI, and preoperative Knee Society Scores between the 2 groups (P = .22, P = .82, and P = .43, respectively). Patients in both groups had a similar incidence of postoperative complications (P = .90). Cementless group had 7 revisions with one aseptic loosening of the tibial component (0.5%). Cementless tibial baseplates demonstrated areas of increased bone density at the pegs of the tibial baseplate. The cemented group had 8 total revisions with 5 cases of aseptic loosening (2.5%).

CONCLUSION

Early results of cementless TKA using a highly porous tibial baseplate designed with a keel and 4 pegs appear promising with one case of aseptic loosening at minimum 2-year follow-up. As the demographics of patients undergoing TKA change to include younger, obese, and more active patients, along with increased life expectancy, the use of a highly porous cementless tibial baseplate may be beneficial in providing long-term durable biologic fixation similar to the success of cementless total hip arthroplasty.

An Independent Active Contours Segmentation framework for bone micro-CT images

Micro-CT is an imaging technique for small tissues and objects that is gaining increased popularity especially as a pre-clinical application. Nevertheless, there is no well-established micro-CT segmentation method, while typical procedures lack sophistication and frequently require a degree of manual intervention, leading to errors and subjective results. To address these issues, a novel segmentation framework, called Independent Active Contours Segmentation (IACS), is proposed in this paper. The proposed IACS is based on two autonomous modules, namely automatic ROI extraction and IAC Evolution, which segments the ROI image using multiple Active Contours that evolve simultaneously and independently of one another. The proposed method is applied on a Phantom dataset and on real datasets. It is tested against several established segmentation methods that include Adaptive Thresholding, Otsu Thresholding, Region Growing, Chan-Vese (CV) AC, Geodesic AC and Automatic Local Ratio-CV AC, both qualitatively and quantitatively. The results prove its superior performance in terms of object identification capability, accuracy and robustness, under normal circumstances and under four types of artificially introduced noise. These enhancements can lead to more reliable analysis, better diagnostic procedures and treatment evaluation of several bone-related pathologies, and to the facilitation and further advancement of bone research.

Effect of low-intensity pulsed ultrasound on the biological behavior of osteoblasts on porous titanium alloy scaffolds: An in vitro and in vivo study

Low-intensity pulsed ultrasound (LIPUS) has been used in patients with fresh fractures, delayed union and non-union to enhance bone healing and improve functional outcome. However, there were few studies concerning the effects of LIPUS on the biological behavior of osteoblasts on porous scaffolds. This study aimed to evaluate the effects of LIPUS on the biological behavior of osteoblasts on porous titanium-6aluminum-4vanadium (Ti6Al4V) alloy scaffolds in vitro and in vivo. Scaffolds were randomly divided into an ultrasound group and a control group. Mouse pre-osteoblast cells were cultured with porous Ti6Al4V scaffolds in vitro. The effects of LIPUS on the biological behavior of osteoblasts were evaluated by observing the adhesion, proliferation, differentiation and ingrowth depth on porous Ti6Al4V scaffolds. In addition, scaffolds were implanted into rabbit mandibular defects in vivo. The effects of LIPUS on bone regeneration were evaluated via micro-CT, fluorescent staining and toluidine blue staining. The results revealed that osteoblast adhered well to the scaffolds, and there was no significant difference in the methyl thiazolyl tetrazolium value between the ultrasound group and the control group (p>0.05). Compared with the control group, ultrasound promoted the alkaline phosphatase activity, osteocalcin levels and ingrowth depth of the cells on the scaffolds (p<0.05). In addition, micro-CT and histomorphological analysis showed that the volume and amount of new bone formation were increased and that bone maturity was improved in the ultrasound group compared to the control group. These results indicate that LIPUS promotes osteoblast differentiation as well as enhances bone ingrowth in porous Ti6Al4V scaffolds, and promotes bone formation and maturity in porous Ti6Al4V scaffolds.

Current State-of-the-Art 3D Tissue Models and Their Compatibility with Live Cell Imaging

Mammalian cells grow within a complex three-dimensional (3D) microenvironment where multiple cells are organized and surrounded by extracellular matrix (ECM). The quantity and types of ECM components, alongside cell-to-cell and cell-to-matrix interactions dictate cellular differentiation, proliferation and function in vivo. To mimic natural cellular activities, various 3D tissue culture models have been established to replace conventional two dimensional (2D) culture environments. Allowing for both characterization and visualization of cellular activities within possibly bulky 3D tissue models presents considerable challenges due to the increased thickness and subsequent light scattering features of such 3D models. In this chapter, state-of-the-art methodologies used to establish 3D tissue models are discussed, first with a focus on both scaffold-free and scaffold-based 3D tissue model formation. Following on, multiple 3D live cell imaging systems, mainly optical imaging modalities, are introduced. Their advantages and disadvantages are discussed, with the aim of stimulating more research in this highly demanding research area.

Three-dimensional imaging technologies: a priority for the advancement of tissue engineering and a challenge for the imaging community

Tissue engineering/regenerative medicine (TERM) is an interdisciplinary field that applies the principle of engineering and life sciences to restore/replace damaged tissues/organs with in vitro artificially-created ones. Research on TERM quickly moves forward. Today newest technologies and discoveries, such as 3D-/bio-printing, allow in vitro fabrication of ex-novo made tissues/organs, opening the door to wide and probably never-ending application possibilities, from organ transplant to drug discovery, high content screening and replacement of laboratory animals. Imaging techniques are fundamental tools for the characterization of tissue engineering (TE) products at any stage, from biomaterial/scaffold to construct/organ analysis. Indeed, tissue engineers need versatile imaging methods capable of monitoring not only morphological but also functional and molecular features, allowing three-dimensional (3D) and time-lapse in vivo analysis, in a non-destructive, quantitative, multidimensional analysis of TE constructs, to analyze their pre-implantation quality assessment and their fate after implantation. This review focuses on the newest developments in imaging technologies and applications in the context of requirements of the different steps of the TERM field, describing strengths and weaknesses of the current imaging approaches.

Bio-scaffolds produced from irradiated squid pen and crab chitosan with hydroxyapatite/β-tricalcium phosphate for bone-tissue engineering

In this study, bio-scaffolds have been developed using irradiated chitosan from different sources - squid pen (RS) and crab shell (RC) - with hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) at a chitosan/HA/β-TCP ratio of 50/30/20. The bio-scaffolds were prepared at two different freezing temperature (-20°C and -80°C) followed by lyophilisation. To enhance the mechanical properties, the bio-scaffolds were cross-linked using sodium tripolyphosphate (TPP) followed by lyophilisation. The composition and morphology of the bio-scaffolds were characterized using XRD, SEM, TEM and μ-CT. The pore size of the porous scaffolds ranged from 90 to 220μm and the scaffolds had 70-80% porosity. The scaffolds had a water uptake ratio of more than 10, and a controlled biodegradation in the range of 30-40%. These results suggest that the physical and biological properties of chitosan-based bio-scaffolds can be a promising biomaterial for bone-tissue regeneration.

Combining microCT-based characterization with empirical modelling as a robust screening approach for the design of optimized CaP-containing scaffolds for progenitor cell-mediated bone formation

Biomaterials are a key ingredient to the success of bone tissue engineering (TE), which focuses on the healing of bone defects by combining scaffolds with cells and/or growth factors. Due to the widely variable material characteristics and patient-specificities, however, current bone TE strategies still suffer from low repeatability and lack of robustness, which hamper clinical translation. Hence, optimal TE construct (i.e. cells and scaffold) characteristics are still under debate. This study aimed to reduce the material-specific variability for cell-based construct design, avoiding trial-and-error, by combining microCT characterization and empirical modelling as an innovative and robust screening approach. Via microCT characterization we have built a quantitative construct library of morphological and compositional properties of six CE approved CaP-based scaffolds (CopiOs®, BioOss™, Integra Mozaik™, chronOS Vivify, MBCP™ and ReproBone™), and of their bone forming capacity and in vivo scaffold degradation when combined with human periosteal derived cells (hPDCs). The empirical model, based on the construct library, allowed identification of the construct characteristics driving optimized bone formation, i.e. (a) the percentage of β-TCP and dibasic calcium phosphate, (b) the concavity of the CaP structure, (c) the average CaP structure thickness and (d) the seeded cell amount (taking into account the seeding efficiency). Additionally, the model allowed to quantitatively predict the bone forming response of different hPDC-CaP scaffold combinations, thus providing input for a more robust design of optimized constructs and avoiding trial-and error. This could improve and facilitate clinical translation.

STATEMENT OF SIGNIFICANCE

Biomaterials that support regenerative processes are a key ingredient for successful bone tissue engineering (TE). However, the optimal scaffold structure is still under debate. In this study, we have provided a useful innovative approach for robust screening of potential biomaterials or constructs (i.e. scaffolds seeded with cells and/or growth factors) by combining microCT characterization with empirical modelling. This novel approach leads to a better insight in the scaffold parameters influencing progenitor cell-mediated bone formation. Additionally, it serves as input for more controlled and robust design of optimized CaP-containing bone TE scaffolds. Hence, this novel approach could improve and facilitate clinical translation.

Scanning Small- and Wide-Angle X-ray Scattering Microscopy Selectively Probes HA Content in Gelatin/Hydroxyapatite Scaffolds for Osteochondral Defect Repair

This study is aimed at investigating the structure of a scaffold made of bovine gelatin and hydroxyapatite for bone tissue engineering purposes. In particular, the detailed characterization of such a material has a great relevance because of its application in the healing process of the osteochondral defect that consists of a damage of cartilage and injury of the adjacent subchondral bone, significantly compromising millions of patient's quality of life. Two different techniques exploiting X-ray radiation, with table-top setups, are used: microtomography (micro-CT) and microdiffraction. Micro-CT characterizes the microstructure in the three dimensions at the micrometer scale spatial resolution, whereas microdiffraction provides combined structural/morphological information at the atomic and nanoscale, in two dimensional microscopy images with a hundred micrometer spatial resolution. The combination of these two techniques allowed an appropriate structural characterization for the purpose of validating the engineering approach used for the realization of the hydroxyapatite gradient across the scaffold, with properties close to the natural model.

A Review of Synthesis Methods, Properties and Use of Hydroxyapatite as a Substitute of Bone

In recent years, a significant achievement has been made in developing biomaterials, in particular the design of bioceramics, from natural sources for various biomedical applications. In this review, we discuss the fundamentals of structure, function and characteristics of human bone, its calcium and phosphate composition, role and importance of bioceramics for bone repairing or regeneration. This review also outlines various isolation techniques and the application of novel marine-derived hydroxyapatite (HA) and tri-calcium phosphate (TCP) for biocomposites engineering, and their potentials for bone substitute and bone regeneration.

Development and characterization of hydroxyapatite/β-TCP/chitosan composites for tissue engineering applications

Calcium phosphate ceramics that mimic bone composition provide interesting possibilities for the advancement in bone tissue engineering. The present study reports on a chitosan composite reinforced by hydroxyapatite (HA) and β-tricalcium phosphate (β-TCP) obtained from waste mussel shells and cross-linked using tripolyphosphate (TPP). The ratios of the ceramic components in composites were 20/10/70, 30/20/50 and 40/30/30 (HA/β-TCP/CH, w/w %). Biodegradation rate, structural properties and in-vitro degradation of the bone-like composite scaffolds were investigated. The optimum amount of TPP required for composite was 2.5% and glycerol was used as plasticizer at an optimized concentration of 1%. Tripolyphosphate cross-linked chitosan composites were developed by freezing and lyophilisation. The Young's modulus of the scaffolds was increased from 4kPa to 17kPa and the porosity of composites dropped from 85 to 68% by increasing the HA/β-TCP ratio. After 28days in physiological solution, bone-like composite scaffolds with a higher ratio of HA/β-TCP (e.g. 40/30/30) showed about 2% lower biodegradation in comparison to scaffolds with a lower ratio of HA/β-TCP (i.e. 20/10/70). The obtained data suggest that the chitosan based bone-like composites could be potential candidates for biomedical applications.

Hierarchical polymeric scaffolds support the growth of MC3T3-E1 cells

Tissue engineering makes use of the principles of biology and engineering to sustain 3D cell growth and promote tissue repair and/or regeneration. In this study, macro/microporous scaffold architectures have been developed using a hybrid solid freeform fabrication/thermally induced phase separation (TIPS) technique. Poly(lactic-co-glycolic acid) (PLGA) dissolved in 1,4-dioxane was used to generate a microporous matrix by the TIPS method. The 3D-bioplotting technique was used to fabricate 3D macroporous constructs made of polyethylene glycol (PEG). Embedding the PEG constructs inside the PLGA solution prior to the TIPS process and subsequent extraction of PEG following solvent removal (1,4-dioaxane) resulted in a macro/microporous structure. These hierarchical scaffolds with a bimodal pore size distribution (<50 and >300 μm) contained orthogonally interconnected macro-channels generated by the extracted PEG. The diameter of the macro-channels was varied by tuning the dispensing parameters of the 3D bioplotter. The in vitro cell culture using murine MC3T3-E1 cell line for 21 days demonstrated that these scaffolds could provide a favorable environment to support cell adhesion and growth.

Imaging strategies for tissue engineering applications

Tissue engineering has evolved with multifaceted research being conducted using advanced technologies, and it is progressing toward clinical applications. As tissue engineering technology significantly advances, it proceeds toward increasing sophistication, including nanoscale strategies for material construction and synergetic methods for combining with cells, growth factors, or other macromolecules. Therefore, to assess advanced tissue-engineered constructs, tissue engineers need versatile imaging methods capable of monitoring not only morphological but also functional and molecular information. However, there is no single imaging modality that is suitable for all tissue-engineered constructs. Each imaging method has its own range of applications and provides information based on the specific properties of the imaging technique. Therefore, according to the requirements of the tissue engineering studies, the most appropriate tool should be selected among a variety of imaging modalities. The goal of this review article is to describe available biomedical imaging methods to assess tissue engineering applications and to provide tissue engineers with criteria and insights for determining the best imaging strategies. Commonly used biomedical imaging modalities, including X-ray and computed tomography, positron emission tomography and single photon emission computed tomography, magnetic resonance imaging, ultrasound imaging, optical imaging, and emerging techniques and multimodal imaging, will be discussed, focusing on the latest trends of their applications in recent tissue engineering studies.

Pre-clinical characterization of tissue engineering constructs for bone and cartilage regeneration

Pre-clinical animal models play a crucial role in the translation of biomedical technologies from the bench top to the bedside. However, there is a need for improved techniques to evaluate implanted biomaterials within the host, including consideration of the care and ethics associated with animal studies, as well as the evaluation of host tissue repair in a clinically relevant manner. This review discusses non-invasive, quantitative, and real-time techniques for evaluating host-materials interactions, quality and rate of neotissue formation, and functional outcomes of implanted biomaterials for bone and cartilage tissue engineering. Specifically, a comparison will be presented for pre-clinical animal models, histological scoring systems, and non-invasive imaging modalities. Additionally, novel technologies to track delivered cells and growth factors will be discussed, including methods to directly correlate their release with tissue growth.

Spatiotemporally controlled microchannels of periodontal mimic scaffolds

Physiologic bioengineering of the oral, dental, and craniofacial complex requires optimized geometric organizations of fibrous connective tissues. A computer-designed, fiber-guiding scaffold has been developed to promote tooth-supporting periodontal tissue regeneration and functional restoration despite limited printing resolution for the manufacture of submicron-scaled features. Here, we demonstrate the use of directional freeze-casting techniques to control pore directional angulations and create mimicked topographies to alveolar crest, horizontal, oblique, and apical fibers of natural periodontal ligaments. For the differing anatomic positions, the gelatin displayed varying patterns of ice growth, determined via internal pore architectures. Regardless of the freezing coordinates, the longitudinal pore arrangements resulted in submicron-scaled diameters (~50 µm), along with corresponding high biomaterial porosity (~90%). Furthermore, the horizontal + coronal ([Formula: see text]) freezing orientation facilitated the creation of similar structures to major fibers in the periodontal ligament interface. This periodontal tissue-mimicking microenvironment is a potential tissue platform for the generation of naturally oriented ligamentous tissues consistent with periodontal ligament neogenesis.