The Potential of Polyethylene Terephthalate Glycol as Biomaterial for Bone Tissue Engineering

Design and evaluation of mechanical strength of multi-material polymeric implants for mandibular reconstruction

Reconstruction of mandible implants to address segmental abnormalities is still a challenging task, both in vitro and in vivo. The mechanical strength of the materials used is a critical factor that determines how well bone is regenerated. The reconstruction technique of mandibular abnormalities widely uses polymeric implants. It is critical to evaluate the mechanical resilience under different load cases, including axial, combined, and flexural loading conditions. This study developed implants for mandibular defects using a combination of four materials: polylactic acid (PLA), polyethylene terephthalate glycol (PETG), thermoplastic polyurethane (TPU), and polycaprolactone (PCL), with the aim of mimicking the inherent characteristics of cortical and cancellous bone structures and evaluating their mechanical properties to support bone Osseo integration. The eleven of these combinations of structures result below the micro strain threshold level of <3000 µε, and the five combinations of the structures result in micro strain above the threshold value. The intact bone study results show that the stress under axial, combined, and flexural loading conditions is 27.6, 38.9, and 64.9 MPa, respectively. This study's stress results are lower than those from the intact bone study. The study found that the combinations of PLA and TPU material were most preferred for the cortical and cancellous bone regions of polymeric implants. These materials are also compatible with 3D printing. The results of this study can be used to find multi-material combinations that are strong and flexible.

A coating machine for coating filaments with bioactive nanomaterials for extrusion 3D printing

Extrusion printing based on biocompatible filaments offers a wide variety of targeted medical and dental applications in the area of personalized medicine, if combined with bioactive nanomaterials. However, this requires filament to be coated with bioactive nanomaterial. This study introduces a concept of a machine to coat filament with bioactive nanomaterials and its application. A machine was constructed with modules manufactured using additive manufacturing. A filament spool of polylactide (PLA) or glycol-modified polyethylene terephthalate (PETG) was transported through a copper tube, with the outer surface of the filament heated to the appropriate glass transition temperature to incorporate added nanomaterials such as nano-hydroxyapatite (nHA) or nano-fluorapatite(nFA). Coatings with nHA led to an increase in diameter of around 3 μm, while coatings with nFA increased the diameter by 4 μm. Printing of cubes with a standard extrusion printer platform using PLA or PETG filaments with added nHA or nFA has been successfully carried out. Scanning electron microscope (SEM) images of coated filaments and printed cubes showed an irregular distribution of nHA or nFA, which could be verified by energy dispersive X-ray analysis (EDX). Adding and adjusting bioactive nanomaterials to filament with a coating machine for filament proved to generate printable filaments. With the wide range of possible applications by different nanomaterials it is anticipated that extrusion printing can cover needs for personalized medicine and dentistry.

Supercritical Impregnation of PETG with Olea europaea Leaf Extract: Influence of Operational Parameters on Expansion Degree, Antioxidant and Mechanical Properties

PETG (poly(ethylene glycol-co-cyclohexane-1,4-dimethanol terephthalate)) is an amorphous copolymer, biocompatible, recyclable, and versatile. Nowadays, it is being actively researched for biomedical applications. However, proposals of PETG as a platform for the loading of bioactive compounds from natural extract are scarce, as well as the effect of the supercritical impregnation on this polymer. In this work, the supercritical impregnation of PETG filaments with Olea europaea leaf extract was investigated, evaluating the effect of pressure (100-400 bar), temperature (35-55 °C), and depressurization rate (5-50 bar min-1) on the expansion degree, antioxidant activity, and mechanical properties of the resulting filaments. PETG expansion degree ranged from ~3 to 120%, with antioxidant loading ranging from 2.28 to 17.96 g per 100 g of polymer, corresponding to oxidation inhibition values of 7.65 and 66.55%, respectively. The temperature and the binary interaction between pressure and depressurization rate most affected these properties. The mechanical properties of PETG filaments depended greatly on process variables. Tensile strength values were similar or lower than the untreated filaments. Young's modulus and elongation at break values decreased below ~1000 MPa and ~10%, respectively, after the scCO2 treatment and impregnation. The extent of this decrease depended on the supercritical operational parameters. Therefore, filaments with higher antioxidant activity and different expansion degrees and mechanical properties were obtained by adjusting the supercritical processing conditions.

The effect of graphene and graphene oxide induced reactive oxygen species on polycaprolactone scaffolds for bone cancer applications

Bone cancer remains a critical healthcare problem. Among current clinical treatments, tumour resection is the most common strategy. It is usually effective but may present several limitations such as multiple operations, long hospital time, and the potential recurrence caused by the incomplete removal of cancer cells. To address these limitations, three-dimensional (3D) scaffolds fabricated through additive manufacturing have been researched for both bone cancer treatment and post-treatment rehabilitation. Polycaprolactone (PCL)-based scaffolds play an important role in bone regeneration, serving as a physical substrate to fill the defect site, recruiting cells, and promoting cell proliferation and differentiation, ultimately leading to the regeneration of the bone tissue without multiple surgical applications. Multiple advanced materials have been incorporated during the fabrication process to improve certain functions and/or modulate biological performances. Graphene-based nanomaterials, particularly graphene (G) and graphene oxide (GO), have been investigated both in vitro and in vivo, significantly improving the scaffold's physical, chemical, and biological properties, which strongly depend on the material type and concentration. A unique targeted inhibition effect on cancer cells was also discovered. However, limited research has been conducted on utilising graphene-based nanomaterials for both bone regeneration and bone cancer treatment, and there is no systematic study into the material- and dose-dependent effects, as well as the working mechanism on 3D scaffolds to realise these functions. This paper addresses these limitations by designing and fabricating PCL-based scaffolds containing different concentrations of G and GO and assessing their biological behaviour correlating it to the reactive oxygen species (ROS) release level. Results suggest that the ROS release from the scaffolds is a dominant mechanism that affects the biological behaviour of the scaffolds. ROS release also contributes to the inhibition effect on bone cancer due to healthy cells and cancer cells responding differently to ROS, and the osteogenesis results also present a certain correlation with ROS. These observations revealed a new route for realising bone cancer treatment and subsequent new bone regeneration, using a single dual-functional 3D scaffold.

Microstructured Polymeric Fabrics Modulating the Paracrine Activity of Adipose-Derived Stem Cells

The deposition of stem cells at sites of injury is a clinically relevant approach to facilitate tissue repair and angiogenesis. However, insufficient cell engraftment and survival require the engineering of novel scaffolds. Here, a regular network of microscopic poly(lactic-co-glycolic acid) (PLGA) filaments was investigated as a promising biodegradable scaffold for human Adipose-Derived Stem Cell (hADSC) tissue integration. Via soft lithography, three different microstructured fabrics were realized where 5 × 5 and 5 × 3 μm PLGA 'warp' and 'weft' filaments crossed perpendicularly with pitch distances of 5, 10 and 20 μm. After hADSC seeding, cell viability, actin cytoskeleton, spatial organization and the secretome were characterized and compared to conventional substrates, including collagen layers. On the PLGA fabric, hADSC re-assembled to form spheroidal-like structures, preserving cell viability and favoring a nonlinear actin organization. Moreover, the secretion of specific factors involved in angiogenesis, the remodeling of the extracellular matrix and stem cell homing was favored on the PLGA fabric as compared to that which occurred on conventional substrates. The paracrine activity of hADSC was microstructure-dependent, with 5 μm PLGA fabric enhancing the expression of factors involved in all three processes. Although more studies are needed, the proposed PLGA fabric would represent a promising alternative to conventional collagen substrates for stem cell implantation and angiogenesis induction.

Resistance of PETG Materials on Thermocycling and Brushing

The aim was to assess the impact of thermocycling and brushing on the surface roughness and mass of PETG material-the most commonly used for orthodontic retainers. A total of 96 specimens were exposed to thermocycling and brushing with three different kinds of toothbrushes depending on the number and thickness of the bristles. Surface roughness and mass were evaluated three times: initially, after thermocycling, and after brushing. In all four brands, both thermocycling and brushing increased surface roughness significantly (p < 0.001), with Biolon having the lowest and Track A having the highest. In terms of brushing, only Biolon samples showed statistically significant increased roughness after brushing with all three types of brushes, in comparison to Erkodur A1, where differences were not statistically significant. Thermocycling increased the mass of all samples, but a statistically significant difference was found only in Biolon (p = 0.0203), while after brushing, decreased mass was found in all specimens, statistically significant only in Essix C+ (CS 1560: p = 0.016). PETG material showed instability when exposed to external influences- thermocycling produced an increase in roughness and mass, and brushing mostly caused an increase in roughness and decrease in mass. Erkodur A1 demonstrated the greatest stability, whereas Biolon demonstrated the lowest.

Topographical and Optical Characteristics of Thermoplastic Dental Appliances Materials Related to Water Sorption

Clear thermoplastic materials have increased in popularity in the dental field due to their various applications, combination of excellent aesthetics, and good biomechanical behavior, but they may be influenced by different environmental conditions. The purpose of the present study was to assess the topographical and optical characteristics of thermoplastic dental appliances materials relative to water sorption. PET-G polyester thermoplastic materials were evaluated in this study. Related to water uptake and desiccation stages, surface roughness was analyzed, and three-dimensional AFM profiles were generated for nano-roughness measurements. Optical CIE L*a*b* coordinates were recorded and parameters like translucency (TP), contrast ratio for the opacity (CR), and opalescence (OP) were derived. Levels of color changes were achieved. Statistical analyses were performed. Water uptake significantly increases the specific weight of the materials, and after desiccation, the mass decreases. Roughness increased after water immersion as well. Regression coefficients indicated a positive correlation between TP and a* and between OP and b*. Studied PET-G materials have a different behavior to water exposure, but for all their specific weight, they increased significantly within the first 12 h. It is accompanied by an increase in the roughness values, even if they continue to be kept below the critical mean surface roughness. On nano-level, 3D images show an increase in inhomogeneity in the network structure of particles. Slight color changes were registered.

Advances in orthodontic clear aligner materials

Rapid technological improvements in biomaterials, computer-aided design (CAD) and manufacturing (CAM) have endorsed clear aligner therapy (CAT) as a mainstay of orthodontic treatment, and the materials employed for aligner fabrication play an all-important role in determining the clinical performance of clear aligners. This narrative review has attempted to comprehensively encompass the entire gamut of materials currently used for the fabrication of clear aligners and elucidate their characteristics that are crucial in determining their performance in an oral environment. Historical developments and current protocols in aligner fabrication, features of contemporary bioactive materials, and emerging trends related to CAT are discussed. Advances in aligner material chemistry and engineering possess the potential to bring about radical transformations in the therapeutic applications of CAT; in the absence of which, clear aligners would continue to underperform clinically, due to their inherent biomechanical constraints. Finally, while innovations in aligner materials such as shape memory polymers, direct three-dimensional (3D) printed clear aligners and bioactive materials combined with clear aligner materials are essential to further advance the applications of CAT; increased awareness of environmental responsibilities among aligner manufacturers, aligner prescribing clinicians and aligner users is essential for better alignment of our climate change goals towards a sustainable planet.

Novel Approaches and Biomaterials for Bone Tissue Engineering: A Focus on Silk Fibroin

Bone tissue engineering (BTE) represents a multidisciplinary research field involving many aspects of biology, engineering, material science, clinical medicine and genetics to create biological substitutes to promote bone regeneration. The definition of the most appropriate biomaterials and structures for BTE is still a challenge for researchers, aiming at simultaneously combining different features such as tissue generation properties, biocompatibility, porosity and mechanical strength. In this scenario, among the biomaterials for BTE, silk fibroin represents a valuable option for the development of functional devices because of its unique biological properties and the multiple chances of processing. This review article aims at providing the reader with a general overview of the most recent progresses in bone tissue engineering in terms of approaches and materials with a special focus on silk fibroin and the related mechanisms involved in bone regeneration, and presenting interesting results obtained by different research groups, which assessed the great potential of this protein for bone tissue engineering.

Multi-Layer Biosensor for Pre-Symptomatic Detection of Puccinia strifformis, the Causal Agent of Yellow Rust

The yellow rust of wheat (caused by Puccinia striiformis f. sp. tritici) is a devastating fungal infection that is responsible for significant wheat yield losses. The main challenge with the detection of this disease is that it can only be visually detected on the leaf surface between 7 and 10 days after infection, and by this point, counter measures such as the use of fungicides are generally less effective. The hypothesis of this study is to develop and use a compact electrochemical-based biosensor for the early detection of P. striiformis, thus enabling fast countermeasures to be taken. The biosensor that was developed consists of three layers. The first layer mimics the wheat leaf surface morphology. The second layer consists of a sucrose/agar mixture that acts as a substrate and contains a wheat-derived terpene volatile organic compound that stimulates the germination and growth of the spores of the yellow rust pathogen P. s. f. sp. tritici. The third layer consists of a nonenzymatic glucose sensor that produces a signal once invertase is produced by P. striiformis, which comes into contact with the second layer, thereby converting sucrose to glucose. The results show the proof that this innovative biosensor can enable the detection of yellow rust spores in 72 h.

Geometry-Based Computational Fluid Dynamic Model for Predicting the Biological Behavior of Bone Tissue Engineering Scaffolds

The use of biocompatible and biodegradable porous scaffolds produced via additive manufacturing is one of the most common approaches in tissue engineering. The geometric design of tissue engineering scaffolds (e.g., pore size, pore shape, and pore distribution) has a significant impact on their biological behavior. Fluid flow dynamics are important for understanding blood flow through a porous structure, as they determine the transport of nutrients and oxygen to cells and the flushing of toxic waste. The aim of this study is to investigate the impact of the scaffold architecture, pore size and distribution on its biological performance using Computational Fluid Dynamics (CFD). Different blood flow velocities (BFV) induce wall shear stresses (WSS) on cells. WSS values above 30 mPa are detrimental to their growth. In this study, two scaffold designs were considered: rectangular scaffolds with uniform square pores (300, 350, and 450 µm), and anatomically designed circular scaffolds with a bone-like structure and pore size gradient (476–979 µm). The anatomically designed scaffolds provided the best fluid flow conditions, suggesting a 24.21% improvement in the biological performance compared to the rectangular scaffolds. The numerical observations are aligned with those of previously reported biological studies.

Low-Cost Cranioplasty—A Systematic Review of 3D Printing in Medicine

The high cost of biofabricated titanium mesh plates can make them out of reach for hospitals in low-income countries. To increase the availability of cranioplasty, the authors of this work investigated the production of polymer-based endoprostheses. Recently, cheap, popular desktop 3D printers have generated sufficient opportunities to provide patients with on-demand and on-site help. This study also examines the technologies of 3D printing, including SLM, SLS, FFF, DLP, and SLA. The authors focused their interest on the materials in fabrication, which include PLA, ABS, PET-G, PEEK, and PMMA. Three-dimensional printed prostheses are modeled using widely available CAD software with the help of patient-specific DICOM files. Even though the topic is insufficiently researched, it can be perceived as a relatively safe procedure with a minimal complication rate. There have also been some initial studies on the costs and legal regulations. Early case studies provide information on dozens of patients living with self-made prostheses and who are experiencing significant improvements in their quality of life. Budget 3D-printed endoprostheses are reliable and are reported to be significantly cheaper than the popular counterparts manufactured from polypropylene polyester.

A full-field DIC analysis of the mechanical-deformation behavior of polyethylene terephthalate glycol (PET-G) aligners

OBJECTIVES

The aim was to investigate the full-field mechanical-deformation behavior of clear aligners made by polyethylene terephthalate glycol (PET-G) subjected to cyclic compression tests.

METHODS

Digital Image Correlation (DIC) (Chu et al., 1985; Schreier et al., 2009), a contactless full-field measurement technique, and Optical Microscope (OM) analysis were applied to study two PET-G aligners thermoformed from discs of a thickness of 0.75 mm and 0.88 mm. The clear aligners were placed on dental shape resin casts and were subjected to cyclic compression up to 13000 load cycles from 0 to 50 N at room temperature. The chosen number of load cycles simulates the average load history to which an aligner is subjected for one week. Local displacements and strains were measured for each test at 2, 6, 10, 20, 1000, 5000 and 13000 loading cycles.

RESULTS

Both aligners showed greater displacements in the early stages of loading, more pronounced for the 0.88 mm one. Local displacement and strain maps are derived both along the load direction and to the transverse one (never done from other researchers). Load-displacement cyclic curves allowed to evaluate the evolution of the stored energy and the stiffness during the test. The OM analyses showed significant morphological variations on the aligners' surface, such as wear and tear, high depressions and cracks, especially for the 0.75 mm specimen.

SIGNIFICANCE

Full-field analysis allowed to understand the mechanical behavior of device with complex geometry and complex load distribution, like invisible aligners. The knowledge of the stiffness and the direction of the total displacement helps the orthodontist to implement the best strategy to improve the patient's comfort and the treatment time.

Chondrogenic Differentiation of Human Mesenchymal Stem Cells and Macrophage Polarization on 3D-Printed Poly(ε-caprolactone)/Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) Blended Scaffolds with Different Secondary Porous Structures

This study was aimed to evaluate the chondrogenic differentiation of human mesenchymal stem cells (hMSCs) and polarization of THP-1-derived macrophages cultured on poly(ε-caprolactone) (PC)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PH) blended scaffolds with dual primary (PP) and secondary (SP) pores, which were fabricated via a 3D printing technique, i.e., fused deposition modeling, followed by a salt-leaching process at 50 °C for varied times, i.e., 15, 30, and 60 min. Sodium chloride (SC), a porogen, was initially incorporated in the blend at varied weight percentages, i.e., 0, 25, and 50%, whereas 1 M NaOH solution and deionized water were used as salt-leaching agents. To elucidate the surface properties of the developed scaffolds, directly governed by the amount of the salt originally mixed and the salt-leaching efficiency, several characterization techniques, e.g., scanning electron microscopy, X-ray microcomputed tomography, mercury intrusion porosimetry, atomic force microscopy, and contact angle measurement, were used. Meanwhile, the salt-leaching efficiency was determined by means of weight loss measurement and thermogravimetric analysis. It was found that the alkaline solution could satisfactorily leach out the salt particles in 60 min with a mild etching of the polymer framework. The most immensely and homogeneously pitted filament surface was observed in the NaOH-treated scaffold initially integrated with 50% salt, i.e., 60B_PC/PH/50SC; the SP structure was mostly open and interconnected. The size of most of micropores was about 0.14 μm. With its suitable microsurface roughness and hydrophilicity, 60B_PC/PH/50SC could properly support the initial attachment and lamellipodia formation of hMSCs, which was favorable for chondrogenesis. Consequently, a significantly increased ratio of glycosaminoglycans/deoxyribonucleic acid and a superior expression of the COL2A1 gene were detected when cells were grown on this material. Although 60B_PC/PH/50SC induced the macrophages to secrete a slightly high level of IL-1β during the first few days of culture, the polarized M1 cells could return to a nearly normal stage at Day7, suggesting no unfavorable chronic inflammation caused by the material.

An experimental study on the role of manufacturing parameters on the dry sliding wear performance of additively manufactured PETG

Additive manufacturing (AM) is a versatile and promising method for rapid prototyping and advanced design applications. Owing to its unique potential for fast production rates, and capacity of creating complex shapes, the number of researches on AM techniques have increased day by day in the technical literature. In this work, contrary to common literature efforts focused on mechanical properties, friction and wear behaviors of additively manufactured PETG samples were analyzed experimentally. As a methodology, fused filament fabrication (FFF) was selected. In order to explore the influence of manufacturing factors on wear properties, layer thickness (0.1, 0.2, and 0.3 mm), infill rate (40, 60, 80, and 100%), and building direction (vertical and horizontal) were changed. Before the friction tests, dimensional accuracy, hardness, and surface roughness measurements were conducted to interpret better the wear results. In addition, macroscopic and microscopic inspections were performed to determine the correct reason behind the deformation. From the data collected during the tests, there was a positive interaction between volume loss and layer thickness. Besides, there was no direct interaction between infill rate/building direction and coefficient of friction. In comparison with vertically built samples, horizontally built samples were subjected to more plastic deformation, and their worn surfaces were severely damaged.

Bone Bricks: The Effect of Architecture and Material Composition on the Mechanical and Biological Performance of Bone Scaffolds

Large bone loss injuries require high-performance scaffolds with an architecture and material composition resembling native bone. However, most bone scaffold studies focus on three-dimensional (3D) structures with simple rectangular or circular geometries and uniform pores, not able to recapitulate the geometric characteristics of the native tissue. This paper addresses this limitation by proposing novel anatomically designed scaffolds (bone bricks) with nonuniform pore dimensions (pore size gradients) designed based on new lay-dawn pattern strategies. The gradient design allows one to tailor the properties of the bricks and together with the incorporation of ceramic materials allows one to obtain structures with high mechanical properties (higher than reported in the literature for the same material composition) and improved biological characteristics.

Novel 3D Bioglass Scaffolds for Bone Tissue Regeneration

The design of scaffolds with optimal biomechanical properties for load-bearing applications is an important topic of research. Most studies have addressed this problem by focusing on the material composition and not on the coupled effect between the material composition and the scaffold architecture. Polymer-bioglass scaffolds have been investigated due to the excellent bioactivity properties of bioglass, which release ions that activate osteogenesis. However, material preparation methods usually require the use of organic solvents that induce surface modifications on the bioglass particles, compromising the adhesion with the polymeric material thus compromising mechanical properties. In this paper, we used a simple melt blending approach to produce polycaprolactone/bioglass pellets to construct scaffolds with pore size gradient. The results show that the addition of bioglass particles improved the mechanical properties of the scaffolds and, due to the selected architecture, all scaffolds presented mechanical properties in the cortical bone region. Moreover, the addition of bioglass indicated a positive long-term effect on the biological performance of the scaffolds. The pore size gradient also induced a cell spreading gradient.

Preparation of Transparent Fast-Growing Poplar Veneers with a Superior Optical Performance, Excellent Mechanical Properties, and Thermal Insulation by Acetylation Modification Using a Green Catalyst

There has been growing interest in transparent conductive substrates due to the prevailing flexible electron devices and the need for sustainable resources. In this study, we demonstrated a transparent fast-growing poplar veneers prepared by acetylated modification, followed by the infiltration of epoxy resin. The work mainly focused on the effect of acetylation treatment using a green catalyst of 4-Dimethylpyridine on the interface of the bulk fast-growing poplar veneer, and the result indicated that the interface hydrophobicity was greatly enhanced due to the higher substitute of acetyl groups; therefore, the interface compatibility between the cell wall and epoxy resin was improved. The obtained transparent fast-growing poplar veneers, hereafter referred to as TADPV, displayed a superior optical performance and flexibility, in which the light transmittance and haze were 90% and 70% at a wavelength of 550 nm, respectively, and the bending radius and bending angle parallel to grain of TADPV were 2 mm and 130°, respectively. Moreover, the tensile strength and tensile modulus of the TADPV were around 102 MPa and 198 MPa, respectively, which is significantly better than those of the plastic substrates used in flexible electron devices. At the same time, the thermal conductivity tests indicated that TADPV has a low coefficient of thermal conductivity of 0.34 Wm⁻¹ K⁻¹, which can completely meet the needs of transparent conductive substrates. Therefore, the obtained TADPV can be used as a candidate for a flexible transparent substrate of electron devices.

The Development of Biomimetic Aligned Skeletal Muscles in a Fully 3D Printed Microfluidic Device

Human skeletal muscles are characterized by a unique aligned microstructure of myotubes which is important for their function as well as for their homeostasis. Thus, the recapitulation of the aligned microstructure of skeletal muscles is crucial for the construction of an advanced biomimetic model aimed at drug development applications. Here, we have developed a 3D printed micropatterned microfluid device (3D-PMMD) through the employment of a fused deposition modeling (FDM)-based 3D printer and clear filaments made of biocompatible polyethylene terephthalate glycol (PETG). We could fabricate micropatterns through the adjustment of the printing deposition heights of PETG filaments, leading to the generation of aligned half-cylinder-shaped micropatterns in a dimension range from 100 µm to 400 µm in width and from 60 µm to 150 µm in height, respectively. Moreover, we could grow and expand C2C12 mouse myoblast cells on 3D-PMMD where cells could differentiate into aligned bundles of myotubes with respect to the dimension of each micropattern. Furthermore, our platform was applicable with the electrical pulses stimulus (EPS) modality where we noticed an improvement in myotubes maturation under the EPS conditions, indicating the potential use of the 3D-PMMD for biological experiments as well as for myogenic drug development applications in the future.

A concise review on the role of selenium for bone cancer applications

Cancer is one of the most challenging health problems in the world. Several clinical treatments have been developed, but all presenting several limitations. Among different types of cancer, bone cancer is less common, and limited new clinical treatment strategies have been proposed. Recently, a range of advanced materials has been investigated and applied for bone cancer treatment applications. However, due to the unique physiological properties of the bone tissue (a load-bearing tissue), the selection of the right type of material or the combination of suitable functional materials and base materials are critical. Selenium has been reported to present specific targeting inhibition effects on bone cancer without affecting the surrounding healthy tissue, revealing a huge potential for the development of new bone cancer treatment strategies. This paper presents a concise review on the use of selenium for bone cancer applications, discussing main synthesis methods, biocompatibility, and cytotoxicity aspects and the combination of selenium with a wide range of ceramics, metals, and polymers. Future perspectives and the novel concept of a dual-functional scaffold for both cancer treatment and new bone regeneration are also discussed.

Enhancing Mechanical Properties of Polymer 3D Printed Parts

Parts made from thermoplastic polymers fabricated through 3D printing have reduced mechanical properties compared to those fabricated through injection molding. This paper analyzes a post-processing heat treatment aimed at enhancing mechanical properties of 3D printed parts, in order to reduce the difference mentioned above and thus increase their applicability in functional applications. Polyethylene Terephthalate Glycol (PETG) polymer is used to 3D print test parts with 100% infill. After printing, samples are packed in sodium chloride powder and then heat treated at a temperature of 220 °C for 5 to 15 min. During heat treatment, the powder acts as support, preventing deformation of the parts. Results of destructive testing experiments show a significant increase in tensile and compressive strength following heat treatment. Treated parts 3D printed in vertical orientation, usually the weakest, display 143% higher tensile strength compared to a control group, surpassing the tensile strength of untreated parts printed in horizontal orientation—usually the strongest. Furthermore, compressive strength increases by 50% following heat treatment compared to control group. SEM analysis reveals improved internal structure after heat treatment. These results show that the investigated heat treatment increases mechanical characteristics of 3D printed PETG parts, without the downside of severe part deformation, thus reducing the performance gap between 3D printing and injection molding when using common polymers.