Development of biocompatible and fully bioabsorbable PLA/Mg films for tissue regeneration applications

Structure-function integrated biodegradable Mg/polymer composites: Design, manufacturing, properties, and biomedical applications

Mg is a typical biodegradable metal widely used for biomedical applications due to its considerable mechanical properties and bioactivity. Biodegradable polymers have attracted great interest owing to their favorable processability and inclusiveness. However, it is challenging for the degradation rates of Mg or polymers to precisely match tissue repair processes, and the significant changes in local pH during degradation hinder tissue repair. The concept of combining Mg with polymers is proposed to overcome the shortcomings of materials, aiming to meet repair needs from various aspects such as mechanics and biology. Therefore, it is essential to systematically understand the behavior of biodegradable Mg/polymer composite (BMPC) from the design, manufacturing, mechanical properties, degradation, and biological effects. In this review, we elaborate on the design concepts and manufacturing strategies of high-strength BMPC, the "structure-function" relationship between the microstructures and mechanical properties of composites, the variation in the degradation rate due to endogenous and exogenous factors, and the establishment of advanced degradation research platform. Additionally, the interplay among composite components during degradation and the biological function of composites under non-responsive/stimuli-responsive platforms are also discussed. Finally, we hope that this review will benefit future clinical applications of "structure-function" integrated biomaterials.

Active packaging film of poly(lactic acid) incorporated with plant-based essential oils of Trachyspermum ammi as an antimicrobial agent and vanilla as an aroma corrector for waffles

This study developed active packaging films of Polylactic acid incorporated with the plant-based essential oils of Trachyspermum ammi, T. ammi and Vanilla to package waffles, where the antimicrobial property was provided by T. ammi and its odor was masked by vanilla essential oil. Compared to conventional solvent-cast films of smaller sizes requiring a huge amount of solvents, bigger-size PLA-oil films with lower solvent demand were prepared by tape casting technique with 10, 30, and 50 wt% essential oil blends. Films were studied for their morphological, chemical, mechanical, barrier, and antimicrobial properties. The presence and time-bound release of volatile oils from the films was confirmed by infrared spectroscopy, with a continuous decrease of oils from the films till day 30. The plasticizing effect of oils in films was evidenced by decreased tensile strength and crystallinity. In contrast, an increase in elongation at break and water vapor permeability of oil films were also measured. Finally, when packed in PLA films containing 50 wt% blend of both oils, waffles shelf-life extended up to 30 days compared to 2 days for the neat PLA film, where Vanilla was found effective in masking the unpleasant odor of T.ammi as confirmed by sensory analysis.

Cytocompatibility, cell-material interaction, and osteogenic differentiation of MC3T3-E1 pre-osteoblasts in contact with engineered Mg/PLA composites

Bioabsorbable Mg wire-reinforced poly-lactic acid (PLA) matrix composites are potential candidate for load-bearing orthopedic implants offering tailorable mechanical and degradation properties by stacking sequence, volume fraction and surface modification of Mg wires. In this study, we investigated the cytocompatibility, cell-material interaction, and bone differentiation behavior of MC3T3-E1 pre-osteoblast cells for medical-grade PLA, Mg/PLA, and PEO-Mg/PLA (having PEO surface modification on Mg wires) composites. MTT and live/dead assay showed excellent biocompatibility of both composites while cell-material interaction analysis revealed that cells were able to adhere and proliferate on the surface of composites. Cells on the longitudinal surface of composites showed a high and uniform cell density while those on transversal surfaces initially avoided Mg regions but later migrated back after the formation of the passivation layer. Bone differentiation tests showed that cells in extracts of PLA and composites were able to initiate the differentiation process as osteogenesis-related gene expressions, alkaline phosphatase protein quantity, and calcium mineralization increased after 7 and 14 days of culture. Interestingly, the bone differentiation response of PEO-Mg/PLA composite was found to be similar to medical-grade PLA, proving its superiority over Mg/PLA composite.

Magnesium-Catalyzed Dye-Embedded Polylactide Nanoparticles for the Effective Killing of Highly Metastatic B16F10 Melanoma Cells

In the current research, dye-embedded polylactic acid (PLA) conjugate materials were synthesized using one-pot ring-opening polymerization (ROP), i.e., (dtHPLA) (2-[(2,4,6-trimethylphenyl) imino]-1(2H)-acenaphthylenone-reduced-PLA) and (dmHPLA) (monoiminoacenaphtheneone-reduced-PLA), and then, nanoparticles (NPs) were engineered in the size range of 150 ± 30 nm. P(dtHPLA) NPs were employed in the treatment of melanoma, an aggressive type of skin cancer, which mandates the development of novel techniques to enhance healing outcomes and eliminate adverse effects related to existing treatments. In addition to exhibiting strong intracellular absorption in the spheroid model, the P(dtHPLA) NPs exhibited a strong cytotoxic effect on B16F10 cells, which resulted in oxidative stress from the generation of reactive oxygen species (ROS) and cell death. Additionally, a live/dead experiment using P(dtHPLA) NPs revealed a notable reduction in cell viability.

Magnesium Hydroxide as a Versatile Nanofiller for 3D-Printed PLA Bone Scaffolds

Polylactic acid (PLA) has attracted much attention in bone tissue engineering due to its good biocompatibility and processability, but it still faces problems such as a slow degradation rate, acidic degradation product, weak biomineralization ability, and poor cell response, which limits its wider application in developing bone scaffolds. In this study, Mg(OH)2 nanoparticles were employed as a versatile nanofiller for developing PLA/Mg(OH)2 composite bone scaffolds using fused deposition modeling (FDM) 3D printing technology, and its mechanical, degradation, and biological properties were evaluated. The mechanical tests revealed that a 5 wt% addition of Mg(OH)2 improved the tensile and compressive strengths of the PLA scaffold by 20.50% and 63.97%, respectively. The soaking experiment in phosphate buffered solution (PBS) revealed that the alkaline degradation products of Mg(OH)2 neutralized the acidic degradation products of PLA, thus accelerating the degradation of PLA. The weight loss rate of the PLA/20Mg(OH)2 scaffold (15.40%) was significantly higher than that of PLA (0.15%) on day 28. Meanwhile, the composite scaffolds showed long-term Mg2+ release for more than 28 days. The simulated body fluid (SBF) immersion experiment indicated that Mg(OH)2 promoted the deposition of apatite and improved the biomineralization of PLA scaffolds. The cell culture of bone marrow mesenchymal stem cells (BMSCs) indicated that adding 5 wt% Mg(OH)2 effectively improved cell responses, including adhesion, proliferation, and osteogenic differentiation, due to the release of Mg2+. This study suggests that Mg(OH)2 can simultaneously address various issues related to polymer scaffolds, including degradation, mechanical properties, and cell interaction, having promising applications in tissue engineering.

The development of magnesium-based biomaterials in bone tissue engineering: A review

Bone regeneration is a vital clinical challenge in massive or complicated bone defects. Recently, bone tissue engineering has come to the fore to meet the demand for bone repair with various innovative materials. However, the reported materials usually cannot satisfy the requirements, such as ideal mechanical and osteogenic properties, as well as biocompatibility at the same time. Mg-based biomaterials have considerable potential in bone tissue engineering owing to their excellent mechanical strength and biosafety. Moreover, the biocompatibility and osteogenic activity of Mg-based biomaterials have been the research focuses in recent years. The main limitation faced in the applications of Mg-based biomaterials is rapid degradation, which can produce excessive Mg2+ and hydrogen, affecting the healing of the bone defect. In order to overcome the limitations, researchers have explored several ways to improve the properties of Mg-based biomaterials, including alloying, surface modification with coatings, and synthesizing other composite materials to control the degradation rate upon implantation. This article reviewed the osteogenic mechanism and requirement for appropriate degradation rate and focused on current progress in the biomedical use of Mg-based biomaterials to inspire more clinical applications of Mg in bone regeneration in the future.

Metastable FeMg particles for controlling degradation rate, mechanical properties, and biocompatibility of Poly(l-lactic) acid (PLLA) for orthopedic applications

Poly(l-lactic) acid (PLLA) is commonly used in bioabsorbable medical implants, but it suffers from slow degradation rate and rapid decline in mechanical properties for orthopedic applications. To address this drawback, recent research has explored the use of Mg as a filler for PLLA, resulting in composites with improved degradation rate and cytocompatibility compared to neat PLLA. In this study, FeMg powder particles were proposed as fillers for PLLA to investigate the potential of PLLA/FeMg composites for bioabsorbable implants. Cylinder specimens of PLLA, PLLA/Fe, PLLA/Mg and PLLA/FeMg were prepared using solvent casting followed by thermo-molding. The microstructure, thermal behavior, in vitro degradation behavior in simulated body fluid, mechanical properties and cytocompatibility of these composites were examined. The results indicate that the presence of FeMg particles prevents the deterioration of the composite mechanical properties, at least up to 14 days. Once a certain amount of degradation of the composite is reached, the degradation is faster than that of PLLA. Direct cytotoxicity assays revealed that pre-osteoblast MC3T3-E1 cells successfully adhered to and proliferated on the PLLA/FeMg surface. The inclusion of a low percentage of Mg into the Fe lattice not only accelerated the degradation rate of Fe but also improved its cytocompatibility. The enhanced degradation rate, mechanical properties, and osteoconductive properties of this composite make it a promising option for temporary orthopedic biomedical devices.

Enhancing the tribological performance of PLA-based biocomposites reinforced with graphene oxide

Poly(lactic acid) (PLA) reinforced with graphene has gained substantial interest as a biomaterial, where the tribological and mechanical behavior of PLA/graphene composites are major concerns. This study aims to develop PLA-based biocomposites reinforced with graphene oxide (GO) that have enhanced tribological capabilities. First, homogenous dispersions of GO and GO treated with the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT) were retained. Then, poly(L-lactic acid) (PLLA) biopolymer and PLLA/GO, PLLA/GO(AOT), PLA/GO(AOT), and PLLA/polyethylene glycol (PEG)/GO biocomposite samples were produced via hot pressing, and their tribological behavior was examined in detail. The worn surface characteristics were examined using scanning electron microscopy (SEM), 3D confocal microscopy, and atomic force microscopy (AFM). Results showed that GO reinforcement considerably affected the sliding wear behavior of PLA. Contrary to anticipated, surface treatment of GO does not improve the PLLA/GO wear resistance; rather, it increases the wear rate. PEG positively affects the sliding wear performance of PLLA/GO. PLLA/GO and PLLA/PEG/GO biocomposites exhibited the lowest wear rate at normal loads of 5 and 8 N, respectively, which was decreased by about 50% compared to unreinforced PLLA samples. With the addition of GO, the wear mechanisms of the PLA-based biocomposites changed from adhesive wear to abrasive wear. These findings might increase the applicability of PLA-based biocomposites where tribological performance is the main concern, such as biodegradable implants for load-bearing bone fractures or scaffolds, opening up new opportunities for their use.

Development, Physiochemical characterization, Mechanical and Finite element analysis of 3D printed Polylactide-β-TCP/α-Al2O3 composite

Herein, material extrusion (MEX) technique is utilized to develop 3D printed models based on reinforcing β-Ca3(PO4)2/α-Al2O3 composite in polylactide (PLA) matrix. β-Ca3(PO4)2/α-Al2O3 composite has been synthesized through co-precipitation method and the phase content of β-Ca3(PO4)2 and α-Al2O3 components are respectively determined as 64 and 36 wt%. The resultant β-Ca3(PO4)2/α-Al2O3 composite mixed with PLA at various weight ratios were extruded as filaments and subsequently 3D printed into definite shapes for the physiochemical, morphological and mechanical evaluation. 3D printed bodies that comprise 5 wt % β-Ca3(PO4)2/α-Al2O3 composite yielded an increasing tensile, compressive and flexural strength in the corresponding order of ∼15, ∼15 and 22% than 3D printed pure PLA. Further, the Representative volume element (RVE) unit cells developed based on the various investigated compositions of PLA-β-Ca3(PO4)2/α-Al2O3 were subjected to mechanical evaluation through Finite element analysis (FEA) under both static and dynamic loading conditions on ASTM standard specimens. The results from experimental and FEA analysis demonstrated good uniformity that confirmed the reinforcement of 5 wt % β-Ca3(PO4)2/α-Al2O3 in PLA matrix as an optimum combination to yield better mechanical strength.

Magnesium/gallic acid bioMOFs laden carbonized mushroom aerogel effectively heals biofilm-infected skin wounds

Biofilm-infected acute skin wounds are still one of the significant challenges that need to be solved urgently in wound healing. Herein, we reported a magnesium/gallic acid bio-MOFs laden carbonized mushroom aerogel (QMOFs-PCMA) combined with photothermal therapy for eradicating biofilms in skin wounds. The design of bioMOFs is mainly responsible for regulating immunity. In vitro, it exhibited ROS clearance and antioxidant ability. In vivo, it could regulate local immune responses from pro-inflammatory status to pro-regenerative status, resulting in decreased inflammatory cytokines expression and increased anti-inflammatory cytokines expression. The carbonized mushroom aerogel is mainly responsible for photothermal therapy (PTT), and the polydopamine and bioMOFs could enhance the photothermal conversion efficiency and stability of carbonized aerogels. The carbonized aerogel in combination with PTT could eradicate S. aureus biofilm in both in vitro and in vivo studies and clear E. coli biofilms in vitro studies. The biofilm clearance and improved inflammatory responses laid a good foundation for wound healing, resulting in the granulation tissue formation, re-epithelialization, and angiogenesis significantly enhanced in the QMOFs-PCMA + NIR group. Our results indicate that the QMOFs-PCMA combined with photothermal therapy may provide a promising treatment for biofilm-infected skin wounds.

Accumulative Rolling Mg/PLLA Composite Membrane with Lamellar Heterostructure for Enhanced Bacteria Inhibition and Rapid Bone Regeneration

Developing composite materials with optimized mechanics, degradation, and bioactivity for bone regeneration has long been a crucial mission. Herein, a multifunctional Mg/Poly-l-lactic acid (Mg/PLLA) composite membrane based on the "materials plain" concept through the accumulative rolling (AR) method is proposed. Results show that at a rolling ratio of 75%, the comprehensive mechanical properties of the membrane in the rolling direction are self-reinforced significantly (elongation at break ≈53.2%, tensile strength ≈104.0 MPa, Young's modulus ≈2.13 GPa). This enhancement is attributed to the directional arrangement and increased crystallization of PLLA molecular chains, as demonstrated by SAXS and DSC results. Furthermore, the AR composite membrane presents a lamellar heterostructure, which not only avoids the accumulation of Mg microparticles (MgMPs) but also regulates the degradation rate. Through the contribution of bioactive MgMPs and their photothermal effect synergistically, the membrane effectively eliminates bacterial infection and accelerates vascularized bone regeneration both in vitro and in vivo. Notably, the membrane exhibits outstanding rat skull bone regeneration performance in only 4 weeks, surpassing most literature reports. In short, this work develops a composite membrane with a "one stone, four birds" effect, opening an efficient avenue toward high-performance orthopedic materials.

Mg-Doped PLA Composite as a Potential Material for Tissue Engineering-Synthesis, Characterization, and Additive Manufacturing

Magnesium (Mg)/Polylactic acid (PLA) composites are promising materials for bone regeneration and tissue engineering applications. PLA is a biodegradable and biocompatible polymer that can be easily processed into various shapes and structures, such as scaffolds, films, and fibers, but has low biodegradability. Mg is a biocompatible metal that has been proven to have good biodegradability and osteoconductivity, which makes it suitable for bone tissue engineering. In this study, we prepared and characterized a Mg/PLA composite as a potential material for direct ink writing (DIW) in 3D printing. The results showed that the addition of Mg has a significant impact on PLA's thermal and structural properties and has also significantly increased the degradation of PLA. XRD was used to determine the degree of crystallinity in the PLA/Mg composite, which provides insight into its thermal stability and degradation behavior. The crystallization temperature of PLA increased from 168 to 172 °C for a 15 wt% Mg incorporation, and the melting temperature reduced from 333 °C to 285 °C. The surface morphology and composition of these films were analyzed with SEM. The films with 5 wt% of Mg particles displayed the best-ordered honeycomb structure in their film form. Such structures are considered to affect the mechanical, biological and heat/mass transfer properties of the Mg/PLA composites and products. Finally, the composite ink was used as a feed for direct ink writing in 3D printing, and the preliminary 3D printing experiments were successful in resulting in dimensionally and structurally integral scaffold samples. The shape fidelity was not very good, and some research is needed to improve the rheological properties of the ink for DIW 3D printing.

Fabrication of PLA-Based Electrospun Nanofibers Reinforced with ZnO Nanoparticles and In Vitro Degradation Study

In this work, electrospun nanofibers based on polylactic acid, PLA, reinforced with ZnO nanoparticles have been studied, considering the growing importance of electrospun mats based on biopolymers for their applications in different fields. Specifically, electrospun nanofibers based on PLA have been prepared by adding ZnO nanoparticles at different concentrations, such as 0.5, 1, 3, 5, 10 and 20 wt%, with respect to the polymer matrix. The materials have been characterized in terms of their morphological, mechanical, and thermal properties, finding 3 wt% as the best concentration to produce PLA nanofibers reinforced with ZnO nanoparticles. In addition, hydrolytic degradation in phosphate buffer solution (PBS) was carried out to study the effect of ZnO nanoparticles on the degradation behavior of PLA-based electrospun nanofiber mats, obtaining an acceleration in the degradation of the PLA electrospun mat.

3D-Printable PLA/Mg Composite Filaments for Potential Bone Tissue Engineering Applications

Magnesium (Mg) is a promising material for bone tissue engineering applications due to it having similar mechanical properties to bones, biocompatibility, and biodegradability. The primary goal of this study is to investigate the potential of using solvent-casted polylactic acid (PLA) loaded Mg (WE43) composites as filament feedstock for fused deposition modeling (FDM) 3D Printing. Four PLA/Magnesium (WE43) compositions (5, 10, 15, 20 wt%) are synthesized and produced into filaments, then used to print test samples on an FDM 3D printer. Assessments are made on how Mg incorporation affected PLA's thermal, physicochemical, and printability characteristics. The SEM study of the films shows that the Mg particles are uniformly distributed in all the compositions. The FTIR results indicate that the Mg particles blend well with the polymer matrix and there is no chemical reaction between the PLA and the Mg particles during the blending process. The thermal studies show that the addition of Mg leads to a small increase in the melting peak reaching a maximum of 172.8 °C for 20% Mg samples. However, there are no dramatic variations in the degree of crystallinity among the Mg-loaded samples. The filament cross-section images show that the distribution of Mg particles is uniform up to a concentration of 15% Mg. Beyond that, non-uniform distribution and an increase in pores in the vicinity of the Mg particles is shown to affect their printability. Overall, 5% and 10% Mg composite filaments were printable and have the potential to be used as composite biomaterials for 3D-printed bone implants.

Essential characteristics improvement of metallic nanoparticles loaded carbohydrate polymeric films - A review

Petroleum-based films have contributed immensely to various environmental issues. Developing green-based films from carbohydrate polymers is crucial for addressing the harms encountered. However, some limitations exist on their property, processibility, and applicability that prohibit their processing for further developments. This review discusses the potential carbohydrate polymers and their sources, film preparation methods, such as solvent-casting, tape-casting, extrusion, and thermo-mechanical compressions for green-based films using various biological polymers with their merits and demerits. Research outcomes revealed that the essential characteristics improvement achieved by incorporating different metallic nanoparticles has significantly reformed the properties of biofilms, including crystallization, mechanical stability, thermal stability, barrier function, and antimicrobial activity. The property-enhanced bio-based films made with nanoparticles are potentially interested in replacing fossil-based films in various areas, including food-packaging applications. The review paves a new way for the commercial use of numerous carbohydrate polymers to help maintain a sustainable green environment.

Thermal Properties and In Vitro Biodegradation of PLA-Mg Filaments for Fused Deposition Modeling

Additive manufacturing, in particular the fused deposition method, is a quite new interesting technique used to obtain specific 3D objects by depositing layer after layer of material. Generally, commercial filaments can be used in 3D printing. However, the obtention of functional filaments is not so easy to reach. In this work, we obtain filaments based on poly(lactic acid), PLA, reinforced with different amounts of magnesium, Mg, microparticles, using a two-step extrusion process, in order to study how processing can affect the thermal degradation of the filaments; we additionally study their in vitro degradation, with a complete release of Mg microparticles after 84 days in phosphate buffer saline media. Therefore, considering that we want to obtain a functional filament for further 3D printing, the simpler the processing, the better the result in terms of a scalable approach. In our case, we obtain micro-composites via the double-extrusion process without degrading the materials, with good dispersion of the microparticles into the PLA matrix without any chemical or physical modification of the microparticles.

Adipose stem cells-derived exosomes modified gelatin sponge promotes bone regeneration

Background: Large bone defects resulting from trauma and diseases still a great challenge for the surgeons. Exosomes modified tissue engineering scaffolds are one of the promising cell-free approach for repairing the defects. Despite extensive knowledge of the variety kinds of exosomes promote tissue regeneration, little is known of the effect and mechanism for the adipose stem cells-derived exosomes (ADSCs-Exos) on bone defect repair. This study aimed to explore whether ADSCs-Exos and ADSCs-Exos modified tissue engineering scaffold promotes bone defects repair. Material/Methods: ADSCs-Exos were isolated and identified by transmission electron microscopy nanoparticle tracking analysis, and western blot. Rat bone marrow mesenchymal stem cells (BMSCs) were exposed to ADSCs-Exos. The CCK-8 assay, scratch wound assay, alkaline phosphatase activity assay, and alizarin red staining were used to evaluate the proliferation, migration, and osteogenic differentiation of BMSCs. Subsequently, a bio-scaffold, ADSCs-Exos modified gelatin sponge/polydopamine scaffold (GS-PDA-Exos), were prepared. After characterized by scanning electron microscopy and exosomes release assay, the repair effect of the GS-PDA-Exos scaffold on BMSCs and bone defects was evaluated in vitro and in vivo. Results: The diameter of ADSCs-exos is around 122.1 nm and high expressed exosome-specific markers CD9 and CD63. ADSCs-Exos promote the proliferation migration and osteogenic differentiation of BMSCs. ADSCs-Exos was combined with gelatin sponge by polydopamine (PDA)coating and released slowly. After exposed to the GS-PDA-Exos scaffold, BMSCs have more calcium nodules with osteoinductive medium and higher expression the mRNA of osteogenic related genes compared with other groups. The quantitative analysis of all micro-CT parameters showed that GS-PDA-Exos scaffold promote new bone formed in the femur defect model in vivo and confirmed by histological analysis. Conclusion: This study demonstrates the repair efficacy of ADSCs-Exos in bone defects, ADSCs-Exos modified scaffold showing a huge potential in the treatment of large bone defects.

Fabrication of PLCL Block Polymer with Tunable Structure and Properties for Biomedical Application

Biodegradable materials are pivotal in the biomedical field, where how to precisely control their structure and performance is critical for their translational application. In this study, poly(L-lactide-b-ε-caprolactone) block copolymers (bPLCL) with well-defined segment structure are obtained by a first synthesis of poly(ε-caprolactone) soft block, followed by ring opening polymerization of lactide to form poly(L-lactide acid)  hard block. The pre-polymerization allows for fabrication of bPLCL with the definite compositions of soft/hard segment while preserving the individual segment of their special soft or hard segment. These priorities make the bPLCL afford biodegradable polymer with better mechanical and biodegradable controllability than the random poly(L-lactide-co-ε-caprolactone) (rPLCL) synthesized via traditional one-pot polymerization. 10 mol% ε-caprolactone introduction can result in a formation of an elastic polymer with elongation at break of 286.15% ± 55.23%. Also, bPLCL preserves the unique crystalline structure of the soft and hard segments to present a more sustainable biodegradability than the rPLCL. The combinative merits make the pre-polymerization technique a promising strategy for a scalable production of PLCL materials for potential biomedical application.

Thermal treatment of magnesium particles in polylactic acid polymer films elicits the expression of osteogenic differentiation markers and lipidome profile remodeling in human adipose stem cells

The efficacy of polylactic acid (PLA)/Magnesium (Mg)-based materials for driving stem cells toward bone tissue engineering applications requires specific Mg surface properties to modulate the interface of stem cells with the film. Here, we have developed novel PLA/Mg-based composites and explored their osteogenic differentiation potential on human adipose stem cells (hASCs). Mg-particles/polymer interface was improved by two treatments: heating in oxidative atmosphere (TT) and surface modification with a compatibilizer (PEI). Different contents of Mg particles were dispersed in PLA and composite surface and bulk properties, protein adsorption, stem cell-PLA/Mg interactions, osteogenic markers expressions, and lipids composition profile were evaluated. Mg particles were uniformly distributed on the surface and in the bulk PLA polymer. Improved and modulated particle-polymer adhesion was observed in Mg particle-treated composites. After 21 days in canonical growth culture conditions, hASCs on PLA/MgTT displayed the highest expression of the general osteogenic markers, RUNX2, SSP1, and BGLAP genes, Alkaline Phosphatase, type I Collagen, Osteopontin, and Calcium deposits. Moreover, by LC/MS QTOF mass-spectrophotometry lipidomic analysis, we found in PLA/MgTT-cells, for the first time, a remodeling of the lipid classes composition associated with the osteogenic differentiation. We ascribed these results to MgTT characteristics, which improve Mg availability and composite osteoinductive performance.

The Mechanical, Thermal, and Chemical Properties of PLA-Mg Filaments Produced via a Colloidal Route for Fused-Filament Fabrication

The effect of Mg particles on the thermal, chemical, physical, and primarily mechanical properties of 3D-printed PLA/Mg composites is studied in this paper. Recently, new colloidal processing has been proposed to introduce Mg particles into the PLA matrix, which ensures good dispersion of the particles and better thermal properties, allowing for thermal processing routes such as extrusion or 3D printing via fused-filament fabrication. The thermal and physical properties are here studied in 1D single-filament-printed PLA/Mg composites with 0 to 10 wt.% of Mg particles by Differential Scanning Calorimetry (DSC); we analyse the PLA chain modifications produced, the crystallinity fraction, and the different crystalline forms of the PLA after thermal processing. Fourier Transform Infrared Spectroscopy (FTIR) is used to confirm the influence of the PLA/Mg colloidal processing after printing. The mechanical properties are measured with a universal tensile test machine on the 1D single-printed filaments via fused-filament fabrication (FFF); the filaments were naturally aged to stable conditions. Filaments with and without a notch are studied to obtain the materials' tensile strength, elastic modulus, and fracture toughness. Different analytical models to explain the results of the PLA-Mg were studied, in which the minimum values for the interface strength of the PLA-Mg composites were calculated.

Periosteum-Inspired Membranes Integrated with Bioactive Magnesium Oxychloride Ceramic Nanoneedles for Guided Bone Regeneration

Guided bone regeneration (GBR) technique using a barrier membrane holds great potential to allow the single-stage reconstruction of critical-sized bone defects. Here, bioactive nanoneedle-like magnesium oxychloride ceramics (MOCs) are synthesized and recruited as an osteoinductive factor within a polycaprolactone-gelatin A (PCL-GelA) membranous matrix to generate a periosteum-mimicking biphasic GBR membrane (PCL-GelA/MOC) to accelerate calvarial defect repair. The PCL-GelA/MOC membrane acts as a shield for defect areas and a reservoir of osteoinductive molecules, which provides a favorable microenvironment for supporting cell proliferation, infiltration, and differentiation. This membrane leads to accelerated osteogenesis and angiogenesis, effectual defect bridging, and significantly enhanced bone regeneration when applied to a 5 mm sized rat calvarial defect. This makes this innovative and multifunctional GBR membrane a suitable candidate for clinical applications with promising curative efficacy.

Effect of the Addition of MgO Nanoparticles on the Thermally-Activated Shape Memory Behavior of Plasticized PLA Electrospun Fibers

In this work, the thermally-activated shape memory behavior of poly(lactic acid)-based electrospun fibers (PLA-based efibers) reinforced with different amounts of magnesium oxide (MgO) nanoparticles (NPs) was studied at different temperatures. In particular, MgO NPs were added at different concentrations, such as 0.1, 0.5, 1 and 3 wt%, with respect to the PLA matrix. The glass-transition temperature of PLA-based efibers was modulated by adding a 20 wt% of oligomer lactic acid as plasticizer. Once the plasticized PLA-based efibers were obtained and basically characterized in term of morphology as well as thermal and mechanical properties, thermo-mechanical cycles were carried out at 60 °C and 45 °C in order to study their thermally-activated shape memory response, demonstrating that their crystalline nature strongly affects their shape memory behavior. Importantly, we found that the plastificant effect in the mechanical response of the reinforced plasticized PLA efibers is balanced with the reinforcing effect of the MgO NPs, obtaining the same mechanical response of neat PLA fibers. Finally, both the strain recovery and strain fixity ratios of each of the plasticized PLA-based efibers were calculated, obtaining excellent thermally-activated shape memory response at 45 °C, demonstrating that 1 wt% MgO nanoparticles was the best concentration for the plasticized system.

The Effect of Ca2+ and Mg2+ Ions Loaded at Degradable PLA Membranes on the Proliferation and Osteoinduction of MSCs

Biodegradable membranes, including Polylactic acid (PLA)-based membranes, are commonly used in bone-tissue-related clinical procedures as biointerface to promote bone tissue regeneration. Calcium (Ca²⁺) and Magnesium (Mg²⁺) ions have been related to the promotion of osteogenesis, where the PLA membranes could be used as carrier and delivery substrate for them to provide osteogenic properties to this material. For this aim, a new ion delivery system based on biodegradable PLA membranes loaded with Mg and hydroxyapatite (HA) particles has been processed by the combination of tape casting and colloidal route. Materials characterization shows that the incorporation of Mg and HA particles changes the surface and hydrophobicity of the PLA membrane, and the in vitro degradation test shows Mg²⁺ and Ca²⁺ ion release and occasionally the precipitation of different ion species onto the membrane surface. Mouse and human Mesenchymal Stem Cells (MSC) were used to define the biocompatibility and bioactivity of these PLA membrane composites, and data indicated Mg²⁺ promotes cell proliferation and potentiates osteoinductive signals, while Ca²⁺ induces the expression of ALP osteogenic marker in human MSCs. Biodegradable PLA membranes loaded with Mg and HA particles is a promising new ion delivery system of Mg²⁺ and Ca²⁺ ions that provides osteogenic signals and works as functional biointerface interfaces with bone tissues.

Highlights on Advancing Frontiers in Tissue Engineering

The field of tissue engineering continues to advance, sometimes in exponential leaps forward, but also sometimes at a rate that does not fulfill the promise that the field imagined a few decades ago. This review is in part a catalog of success in an effort to inform the process of innovation. Tissue engineering has recruited new technologies and developed new methods for engineering tissue constructs that can be used to mitigate or model disease states for study. Key to this antecedent statement is that the scientific effort must be anchored in the needs of a disease state and be working toward a functional product in regenerative medicine. It is this focus on the wildly important ideas coupled with partnered research efforts within both academia and industry that have shown most translational potential. The field continues to thrive and among the most important recent developments are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies that warrant special attention. Developments in the aforementioned areas as well as future directions are highlighted in this article. Although several early efforts have not come to fruition, there are good examples of commercial profitability that merit continued investment in tissue engineering. Impact statement Tissue engineering led to the development of new methods for regenerative medicine and disease models. Among the most important recent developments in tissue engineering are the use of three-dimensional bioprinting, organ-on-a-chip, and induced pluripotent stem cell technologies. These technologies and an understanding of them will have impact on the success of tissue engineering and its translation to regenerative medicine. Continued investment in tissue engineering will yield products and therapeutics, with both commercial importance and simultaneous disease mitigation.

Processing and mechanical properties of novel biodegradable poly-lactic acid/Zn 3D printed scaffolds for application in tissue regeneration

The feasibility to manufacture scaffolds of poly-lactic acid reinforced with Zn particles by fused filament fabrication is demonstrated for the first time. Filaments of 2.85 mm in diameter of PLA reinforced with different weight fractions of μm-sized Zn - 1 wt.% Mg alloy particles (in the range 3.5 to 17.5 wt.%) were manufactured by a double extrusion method in which standard extrusion is followed by precision extrusion in a filament-maker machine. Filaments with constant diameter, negligible porosity and a homogeneous reinforcement distribution were obtained for Zn weight fractions of up to 10.5%. It was found that the presence of Zn particles led to limited changes in the physico-chemical properties of the PLA that did not affect the window temperature for 3D printing nor the melt flow index. Thus, porous scaffolds could be manufactured by fused filament fabrication at 190 °C with poly-lactic acid/Zn composites containing 3.5 and 7 wt.% of Zn and at 170 °C when the Zn content was 10.5 wt.% with excellent dimensional accuracy and mechanical properties.

Compositional Influence on the Morphology and Thermal Properties of Woven Non-Woven Mats of PLA/OLA/MgO Electrospun Fibers

In the present work, a statistical study of the morphology and thermal behavior of poly(lactic acid) (PLA)/oligomer(lactic acid) (OLA)/magnesium oxide nanoparticles (MgO), electrospun fibers (efibers) has been carried out. The addition of both, OLA and MgO, is expected to modify the final properties of the electrospun PLA-based nanocomposites for their potential use in biomedical applications. Looking for the compositional optimization of these materials, a Box−Wilson design of experiment was used, taking as dependent variables the average fiber diameter as the representative of the fiber morphologies, as well as the glass transition temperature (Tg) and the degree of crystallinity (Xc) as their thermal response. The results show <r2> values of 73.76% (diameter), 88.59% (Tg) and 75.61% (Xc) for each polynomial fit, indicating a good correlation between both OLA and MgO, along with the morphological as well as the thermal behavior of the PLA-based efibers in the experimental space scanned.

Special Features of Polyester-Based Materials for Medical Applications

This article presents current possibilities of using polyester-based materials in hard and soft tissue engineering, wound dressings, surgical implants, vascular reconstructive surgery, ophthalmology, and other medical applications. The review summarizes the recent literature on the key features of processing methods and potential suitable combinations of polyester-based materials with improved physicochemical and biological properties that meet the specific requirements for selected medical fields. The polyester materials used in multiresistant infection prevention, including during the COVID-19 pandemic, as well as aspects covering environmental concerns, current risks and limitations, and potential future directions are also addressed. Depending on the different features of polyester types, as well as their specific medical applications, it can be generally estimated that 25-50% polyesters are used in the medical field, while an increase of at least 20% has been achieved since the COVID-19 pandemic started. The remaining percentage is provided by other types of natural or synthetic polymers; i.e., 25% polyolefins in personal protection equipment (PPE).

Synthesis of Sucrose-HDI Cooligomers: New Polyols for Novel Polyurethane Networks

Sucrose-1,6-hexamethylene diisocyanate (HDI) cooligomers were synthesized and used as new polyols for poly(ε-caprolactone) (PCL)-based polyurethanes. The polyaddition reaction of sucrose and HDI was monitored by MALDI-TOF MS. It was found that by selecting appropriate reaction conditions, mostly linear oligomer chains containing 16 sucrose units could be obtained. For the synthesis of polyurethane networks, prepolymers were prepared by the reaction of poly(ε-caprolactone) (PCL, 10 kg/mol) with HDI or 4,4′-methylene diphenyl diisocyanate (MDI) and were reacted with sucrose-HDI cooligomers. The so-obtained sucrose-containing polyurethanes were characterized by means of attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FT IR), swelling, mechanical (uniaxial tensile tests) and differential scanning calorimetry (DSC).

In vitro corrosion study of PLA/Mg composites for cardiovascular stent applications

The present investigation explores the impact of Mg volume fraction (V_Mg) as a controlling parameter of degradation rate in designing patient-specific cardiovascular stents made of PLA/Mg composites. For the purpose of this research, PLA/Mg composite plates containing 1, 3, 5, and 10% V_Mg are produced by melt blending and hot press molding. Characterization techniques such as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD) are employed to study the microstructure of PLA/Mg composites. For in vitro corrosion tests, stent prototypes and composite samples are immersed in baths of simulated body fluid (SBF). According to in vitro corrosion tests, increasing V_Mg increases the corrosion rate of the composites by accelerating the corrosion of the particles and the crystalline zones surrounding them. In addition, a 2% raise in the Mg content (from 1% to 3%), increases the overall Mg weight loss by more than 4 times. Composite samples and prototype stents containing more than 5% V_Mg exhibit cracking and brittleness after 7 days of immersion in SBF. In light of the compression tests results and also the failures and cracks observed during immersions, the upper limit of Mg content for PLA/Mg stent fabrication purposes is found to be below 3%.

Cytocompatibility of a mussel-inspired poly(lactic acid)-based adhesive

Incorporating catechols into polymers can provide strong adhesion even in moist environments, and these polymers show promise for use in several biomedical applications. Surgical adhesives must have strong bonds, be biocompatible, and function in a moist environment. Poly(lactic acid) (PLA) has a long history as a biocompatible material for hard tissue device fixation. By combining these concepts, catechol-containing poly(lactic acid) (cPLA) polymers are created that are strongly adhesive and degrade in physiological environments. Here, we evaluated the cytocompatibility of cPLA with iron(III) or periodate (IO₄ ^- ) cross-linkers. Fibroblasts cultured in cPLA leachate or on cPLA films generally had slower growth and lower metabolism compared with PLA controls but no differences in viability. These results demonstrated that cPLA was not cytotoxic but that including catechols reduced cell health. When cPLA was cross-linked with periodate, cells generally had reduced metabolism, slower cell growth, and poor actin fiber formation compared with PLA. These results are attributed to the cytotoxicity of periodate since cells cultured with periodate leachate had extremely low viability. Cells grown on the films of iron-cross-linked cPLA generally had high viability and metabolism but slower proliferation than PLA controls. These results indicate that the cPLA and iron-cross-linked cPLA systems are promising materials for biomedical adhesive applications.

Method, Material, and Machine: A Review for the Surgeon Using Three-Dimensional Printing for Accelerated Device Production

BACKGROUND

Physicians are at the forefront of identifying innovative targets to address current medical needs. 3D printing technology has emerged as a state-of-the-art method of prototyping medical devices or producing patient-specific models that is more cost-efficient, with faster turnaround time, in comparison to traditional prototype manufacturing. However, initiating 3D printing projects can be daunting due to the engineering learning curve, including the number of methodologies, variables, and techniques for printing from which to choose. To help address these challenges, we sought to create a guide for physicians interested in venturing into 3D printing.

STUDY DESIGN

All commercially available, plug-and-play, material and stereolithography printers costing less than $15,000 were identified via web search. Companies were contacted to obtain quotes and information sheets for all printer models. The qualifying printers' manufacturer specification sheets were reviewed, and pertinent variables were extracted.

RESULTS

We reviewed 309 commercially available printers and materials and identified 118 printers appropriate for clinicians desiring plug-and-play models for accelerated device production. We synthesized this information into a decision-making tool to choose the appropriate parameters based on project goals.

CONCLUSIONS

There is a growing clinical need for medical devices to reduce costs of care and increase access to personalized treatments; however, the learning curve may be daunting for surgeons. In this review paper, we introduce the "3Ms of 3D printing" for medical professionals and provide tools and data sheets for selection of commercially available, affordable, plug-and-play 3D printers appropriate for surgeons interested in innovation.

Controlled SrR Delivery by the Incorporation of Mg Particles on Biodegradable PLA-Based Composites

Among several ions playing a vital role in the body, Sr²⁺ and Mg²⁺ are involved in the mechanism of bone formation, making them especially useful for bone tissue engineering applications. Recently, polylactic acid (PLA)/Mg composites have emerged as a promising family of biomaterials due to their inherent biocompatibility and biodegradability properties. In these composites, polymer and bio-metal have a synergetic effect—while the PLA inhibits the Mg fast reactivity, Mg provides bioactivity to the inert polymer buffering the medium pH during degradation. Meanwhile, the typical form of administrating Sr²⁺ to patients is through the medication strontium ranelate (SrR), which increases the bone mineral density. Following this interesting research line, a new group of composites, which integrates Mg particles and SrR charged onto halloysite nanotubes (HNT) in a polymeric matrix, was proposed. PLA/Mg/SrR–HNT composites have been processed following a colloidal route, obtaining homogenous composites granulated and film-shaped. The drug delivery profile was evaluated in terms of in vitro lixiviation/dissolution paying special attention to the synergism of both ions release. The combination of two of the most reported ions involved in bone regeneration in the composite biomaterial may generate extra interest in bone healing applications.

High Flexible and Broad Antibacterial Nanodressing Induces Complete Skin Repair with Angiogenic and Follicle Regeneration

Complete skin reconstruction is a hierarchically physiological assembly involving epidermis, dermis, vasculature, innervation, hair follicles, and sweat glands. Despite various wound dressings having been developed for skin regeneration, few works refer to the complete skin regeneration, particularly lacking for vasculatures and hair follicles. Herein, an instructive wound dressing that integrates the antibacterial property of quaternized chitin and the mechanical strength and biological multifunction of silk fibroin through layer-by-layer electrostatic self-assembly is designed and reported. The resultant dressings exhibit a nanofibrous structure ranging from 471.5 ± 212.1 to 756.9 ± 241.8 nm, suitable flexibility with tensile strength up to 4.47 ± 0.29 MPa, and broad-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus. More interestingly, the current dressing system remarkably accelerates in vivo vascular reconstruction within 15 days, and the number of regenerated hair follicles reaches up to 22 ± 4 mm-2, which is comparable to the normal tissue (27 ± 2 mm-2). Those crucial functions might originate from the combination between quaternized chitin and silk fibroin and the hierarchical structure of electrospun nanofiber. This work establishes an easy but effective pathway to design a multifunctional wound dressing for the complete skin regeneration.

Recent trends on wound management: New therapeutic choices based on polymeric carriers

Wound healing is an unmet therapeutic challenge among medical society since wound assessment and management is a complex procedure including several factors playing major role in healing process. Wounds can mainly be categorized as acute or chronic. It is well referred that the acute wound displays normal wound physiology while healing, in most cases, is seemed to progress through the normal phases of wound healing. On the other hand, a chronic wound is physiologically impaired. The main problem in wound management is that the majority of wounds are colonized with microbes, whereas this does not mean that all wounds will be infected. In this review, we address the problems that clinicians face to manage while treat acute and chronic wounds. Moreover, we demonstrate the pathophysiology, etiology, prognosis and microbiology of wounds. We further introduce the state of art in pharmaceutical technology field as part of wound management aiming to assist health professionals to overcome the current implications on wound assessment. In addition, authors review researches which included the use of gels and dermal films as wound healing agents. It can be said that natural and synthetic drugs or carriers provide promising solutions in order to meet the wound management standards. However, are the current strategies as desirable as medical society wish?

Osteoconductive and osteoinductive biodegradable microspheres serving as injectable micro-scaffolds for bone regeneration

There are intensive needs for scaffolds with new designs to meet the diverse requirements of bone repairing. Biodegradable microspheres are highlighted as injectable micro-scaffolds thanks to their advantages in filling irregular defects via a minimally invasive surgery. In this study, microspheres with surface micropores were made via the W1/O/W2 double emulsion method using amphiphilic triblock copolymers (PLLA-PEG-PLLA) composed of poly(L-lactide) (PLLA) and poly(ethylene glycol) (PEG) segments. When the PEG fraction was controlled as 10 wt.%, the microspheres demonstrated higher cell affinity than the smooth-surfaced PLLA microspheres. After being further functionalized with polydopamine coating and apatite deposition, the PLLA-PEG-PLLA microspheres could up-regulate the osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs) significantly. Before subcutaneous implantation, bone morphogenetic protein-2 (BMP-2) was adsorbed onto the biomineralized microspheres by taking advantages of the strong affinity of apatite to BMP-2. The resulted microspheres induced ectopic osteogenesis efficiently without causing biocompatibility problems. In summary, this study provided a simple strategy to prepare functionalized microspheres with osteoconductivity and osteoinductivity, which showed great potential in promoting bone regeneration as injectable micro-scaffolds.

Bioresorbable magnesium-reinforced PLA membrane for guided bone/tissue regeneration

Considering the inferior mechanical properties of the current bioresorbable polymers, a novel bioresorbable magnesium-reinforced polylactide (PLA) membrane was designed for the application in critical defect sites in guided bone/tissue regeneration. The PLA-FAZ91 membrane was fabricated by combining two PLA membranes with a fluoride-coated AZ91 (9 wt% Al, 1 wt% Zn) (FAZ91) magnesium alloy core by hot pressing. A combined double-layered PLA membrane was used as the control group. A three-point bending test was performed to compare their maximum load and stiffness. Samples were immersed in the HBSS for 20 weeks, and their weight loss percentages were recorded, and a three-point bending test was performed after immersion. An ion release test was performed by immersing samples in the HBSS for 4 weeks and determining the pH and ion concentrations of the HBSS. Cell viability was tested by culturing pre-osteoblast cells with sample extracts in the culture medium obtained from degraded samples. As a result, PLA-FAZ91 showed a significantly higher maximum load and stiffness than those of the non-reinforced PLA membrane. The weight loss of PLA-FAZ91 was much faster, as FAZ91 showed major degradation and was completely degraded after 16-20 weeks of immersion. The degradation of the PLA wrap was accelerated by FAZ91. The mechanical superiority of PLA-FAZ91 over PLA endured for at least 3 weeks during immersion. The pH, magnesium- and fluoride-ion concentration in the PLA-FAZ91 group increased at an appropriate rate. The cell viability was not adversely affected by the addition of FAZ91 to PLA. Therefore, the bioresorbable magnesium-reinforced PLA membrane has the potential to be used as a good alternative to pure PLA membrane in guided bone/tissue regeneration.

Potential Applications of Magnesium-Based Polymeric Nanocomposites Obtained by Electrospinning Technique

In the last few decades, the development of new electrospun materials with different morphologies and advanced multifunctional properties are strongly consolidated. There are several reviews that describe the processing, use and characterization of electrospun nanocomposites, however, based on our knowledge, no review on electrospun nanocomposites reinforced with nanoparticles (NPs) based on magnesium, Mg-based NPs, are reported. Therefore, in the present review, we focus attention on the fabrication of these promising electrospun materials and their potential applications. Firstly, the electrospinning technique and its main processing window-parameters are described, as well as some post-processing methods used to obtain Mg-based materials. Then, the applications of Mg-based electrospun nanocomposites in different fields are pointed out, thus taking into account the current trend in developing inorganic-organic nanocomposites to gradually satisfy the challenges that the industry generates. Mg-based electrospun nanocomposites are becoming an attractive field of research for environmental remediation (waste-water cleaning and air filtration) as well as for novel technical textiles. However, the mayor application of Mg-based electrospun materials is in the biomedical field, as pointed out. Therefore, this review aims to clarify the tendency in using electrospinning technique and Mg-based nanoparticles to huge development at industrial level in the near future.

Photoluminescent biodegradable polyorganophosphazene: A promising scaffold material for in vivo application to promote bone regeneration

Tissue engineering scaffolds made of conventional aliphatic polyesters are inherently non-fluorescent, which results in their in vivo degradation hard to be visualized. Photoluminescent biodegradable polyorganophosphazenes (PPOPs) are synthesized by introducing fluorophores onto the polyphosphazene backbone via nucleophilic substitution reaction. In this study, a fluorophore (termed as TPCA), derived from citric acid and 2-aminoethanethiol, was co-substituted with alanine ethyl ester onto the polyphosphazene backbone to obtain a photoluminescent biodegradable POPP (termed as PTA). The scaffolds made of PTA demonstrated non-cytotoxicity and cell affinity, particularly, capacity in promoting osteogenic differentiation of bone marrow mesenchymal stromal cells (BMSCs). In vivo evaluations using the rat calvarial defect model confirmed its strong potential in enhancing osteogenesis, more importantly, the in vivo degradation of the PTA scaffold could be monitored via its fluorescence intensity alongside implantation time.

Aging of Solvent-Casting PLA-Mg Hydrophobic Films: Impact on Bacterial Adhesion and Viability

Biomaterials used for the manufacture of biomedical devices must have suitable surface properties avoiding bacterial colonization and/or proliferation. Most biomaterial-related infections start during the surgery. Bacteria can begin colonization of the surface of a device right after implantation or in the next few hours. This time may also be sufficient to begin the deterioration of a biodegradable implant. This work explores the surface changes that hydrophobic films of poly(lactic) acid reinforced with Mg particles, prepared by solving-casting, undergone after in vitro degradation at different times. Hydrophobicity, surface tension, zeta potential, topography, and elemental composition were obtained from new and aged films. The initial degradation for 4 h was combined with unspecific bacterial adhesion and viability tests to check if degraded films are more or less susceptible to be contaminated. The degradation of the films decreases their hydrophobicity and causes the appearance of a biocompatible layer, composed mainly of magnesium phosphate. The release of Mg2+ is very acute at the beginning of the degradation process, and such positive charges may favor the electrostatic approach and attachment of Staphylococci. However, all bacteria attached on the films containing Mg particles appeared damaged, ensuring the bacteriostatic effect of these films, even after the first hours of their degradation.