Biodegradable poly(l-lactide) composites by oligolactide-grafted magnesium hydroxide for mechanical reinforcement and reduced inflammation

Polydioxanone Enhances Bone Regeneration After Resection and Reconstruction of Rat Femur with rhBMP2

The aim of this study was to assess the bone regeneration potential of a polydioxanone (PDO) scaffold together with recombinant human bone morphogenetic protein-2 (rhBMP-2) for the reconstruction of large bone defect. In total, 24 male rats (6 months old) were subjected to bilateral femoral stabilization using titanium plates to create a 2 mm gap, and reconstruction using rhBMP-2 (Infuse®; 3.25 μg). The bone defects were covered with PDO (PDO group), or with titanium mesh (Ti group). Animals were euthanized on days 14 and 60. Simultaneously, 16 rats received PDO and Ti in their dorsum for the purpose of biocompatibility analysis at 3, 5, 7, and 10 days postoperatively. X-ray densitometry showed a higher density in the PDO group on day 14. On day 60, coverage of the bone defect with PDO showed a larger quantity of newly formed bone than that found for the Ti group, a lower inflammatory infiltrate value, and a more significant number of blood vessels on day 14. By immunohistochemical assessment, runt-related transcription factor 2 (RUNX2) and osteocalcin (OCN) showed higher labeling on day 14 in the PDO group. On day 60, bone morphogenetic protein-2 (BMP-2) showed higher labeling in the PDO group, whereas Ti showed higher labeling for osteoprotegerin, nuclear factor kappa B ligand-activating receptor, RUNX2, and OCN. Furthermore, biocompatibility analysis showed a higher inflammatory response in the Ti group. The PDO scaffold enhanced bone regeneration when associated with rhBMP-2 in rat femur reconstruction. Impact statement Regeneration of segmental bone defects is a difficult task, and several techniques and materials have been used. Recent advances in the production of synthetic polymers, such as polydioxanone (PDO), produced by three-dimensional printing, have shown distinct characteristics that could improve tissue regeneration even in an important bone defect. The present preclinical study showed that PDO membranes used as scaffolds to carry recombinant human bone morphogenetic protein-2 (rhBMP-2) improved bone tissue regeneration by more than 8-fold when compared with titanium mesh, suggesting that PDO membranes could be a feasible and useful material for use in guided bone regeneration. (In English, viable is only used for living creatures capable of sustaining life.

Three Birds, One Stone: An Osteo-Microenvironment Stage-Regulative Scaffold for Bone Defect Repair through Modulating Early Osteo-Immunomodulation, Middle Neovascularization, and Later Osteogenesis

In order to repair critical-sized bone defects, various polylactic acid-glycolic acid (PLGA)-based hybrid scaffolds are successfully developed as bone substitutes. However, the byproducts of these PLGA-based scaffolds are known to acidify the implanted site, inducing tiresome acidic inflammation. Moreover, these degradation productions cannot offer an osteo-friendly microenvironment at the implanted site, matching natural bone healing. Herein, inspired by bone microenvironment atlas of natural bone-healing process, an osteo-microenvironment stage-regulative scaffold (P80/D10/M10) is fabricated by incorporating self-developed decellularized bone matrix microparticles (DBM-MPs) and multifunctional magnesium hydroxide nanoparticles (MH-NPs) into PLGA with an optimized proportion using low-temperature rapid prototyping (LT-RP) 3D-printing technology. The cell experiments show that this P80/D10/M10 exhibits excellent properties in mechanics, biocompatibility, and biodegradability, meanwhile superior stimulations in osteo-immunomodulation, angiogenesis, and osteogenesis. Additionally, the animal experiments determined that this P80/D10/M10 can offer an osteo-friendly microenvironment in a stage-matched pattern for enhanced bone regeneration, namely, optimization of early inflammation, middle neovascularization, and later bone formation. Furthermore, transcriptomic analysis suggested that the in vivo performance of P80/D10/M10 on bone defect repair is mostly attributed to regulating artery development, bone development, and bone remodeling. Overall, this study reveals that the osteo-microenvironment stage-regulative scaffold provides a promising treatment for bone defect repair.

Angiogenesis coupled with osteogenesis in a bone tissue engineering scaffold enhances bone repair in osteoporotic bone defects

Increased life expectancy has resulted in an increase in osteoporosis incidence worldwide. The coupling of angiogenesis and osteogenesis is indispensable for bone repair. Although traditional Chinese medicine (TCM) exerts therapeutic effects on osteoporosis, TCM-related scaffolds, which focus on the coupling of angiogenesis and osteogenesis, have not yet been used for the treatment of osteoporotic bone defects.Panax notoginsengsaponin (PNS), the active ingredient ofPanax notoginseng, was added to a poly (_L-lactic acid) (PLLA) matrix. Osteopractic total flavone (OTF), the active ingredient ofRhizoma Drynariae, was encapsulated in nano-hydroxyapatite/collagen (nHAC) and added to the PLLA matrix. Magnesium (Mg) particles were added to the PLLA matrix to overcome the bioinert character of PLLA and neutralize the acidic byproducts generated by PLLA. In this OTF-PNS/nHAC/Mg/PLLA scaffold, PNS was released faster than OTF. The control group had an empty bone tunnel; scaffolds containing OTF:PNS = 100:0, 50:50, and 0:100 were used as the treatment groups. Scaffold groups promoted new vessel and bone formation, increased the osteoid tissue, and suppressed the osteoclast activity around osteoporotic bone defects. Scaffold groups upregulated the expression levels of angiogenic and osteogenic proteins. Among these scaffolds, the OTF-PNS (50:50) scaffold exhibited a better capacity for osteogenesis than the OTF-PNS (100:0 and 0:100) scaffolds. Activation of the bone morphogenic protein (BMP)-2/BMP receptor (BMPR)-1A/runt-related transcription factor (RUNX)-2signaling pathway may be a possible mechanism for the promotion of osteogenesis. Our study demonstrated that the OTF-PNS/nHAC/Mg/PLLA scaffold could promote osteogenesis via the coupling of angiogenesis and osteogenesis in osteoporotic rats with bone defects, and activating theBMP-2/BMPR1A/RUNX2signaling pathway may be an osteogenesis-related mechanism. However, further experiments are necessary to facilitate its practical application in the treatment of osteoporotic bone defects.

Directed Regeneration of Osteochondral Tissue by Hierarchical Assembly of Spatially Organized Composite Spheroids

The use of engineered scaffolds or stem cells is investigated widely in the repair of injured musculoskeletal tissue. However, the combined regeneration of hierarchical osteochondral tissue remains a challenge due to delamination between cartilage and subchondral bone or difficulty in spatial control over differentiation of transplanted stem cells. Here, two types of composite spheroids are prepared using adipose-derived stem cells (hADSCs) and nanofibers coated with either transforming growth factor-β3 or bone morphogenetic growth factor-2 for chondrogenesis or osteogenesis, respectively. Each type of spheroid is then cultured within a 3D-printed microchamber in a spatially arranged manner to recapitulate the bilayer structure of osteochondral tissue. The presence of inductive factors regionally modulates in vitro chondrogenic or osteogenic differentiation of hADSCs within the biphasic construct without dedifferentiation. Furthermore, hADSCs from each spheroid proliferate and sprout and successfully connect the two layers mimicking the osteochondral interface without apertures. In vivo transplantation of the biphasic construct onto a femoral trochlear groove defect in rabbit knee joint results in 21.2 ± 2.8% subchondral bone volume/total volume and a cartilage score of 25.0 ± 3.7. The present approach can be an effective therapeutic platform to engineer complex tissue.

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%.

Impact of Lipid/Magnesium Hydroxide Hybrid Nanoparticles on the Stability of Vascular Endothelial Growth Factor-Loaded PLGA Microspheres

The purpose of the present study is to characterize poly(d,l-lactide-co-glycolide) (PLGA) composite microcarriers for vascular endothelial growth factor (VEGF) delivery. To reduce the initial burst release and protect the bioactivity, VEGF is encapsulated in soybean l-α-phosphatidylethanolamine (PE) and l-α-phosphatidylcholine (PC) anhydrous reverse micelle (VEGF-RM) nanoparticles. Also, mesoporous nano-hexagonal Mg(OH)₂ nanostructure (MNS)-loaded PE/PC anhydrous reverse micelle (MNS-RM) nanoparticles are synthesized to suppress the induced inflammation of PLGA acidic byproducts and regulate the release profile. The flow-focusing microfluidic geometry platforms are used to fabricate different combinations of PLGA composite microspheres (PLGA-CMPs) with MNSs, MNS-RM, VEGF-RM, and native VEGF. The essential parameters of each formulation, such as release profiles, encapsulation efficacy, bioactivity, inflammatory response, and cytotoxicity, are investigated by in vitro and in vivo studies. The results indicate that generated acidic byproducts during the hydrolytic degradation process of PLGA can be buffered, and pH values inside and outside microspheres can remain steady during degradation by MNSs. Furthermore, the significant improvement in the stability of the encapsulated VEGF is confirmed by the bioactivity assay. In vitro release study shows that the VEGF initial burst release is well minimized in the present microcarriers. The present monodisperse PLGA-CMPs can be widely used in various tissue engineering and therapeutic applications.

PLGA Microspheres Containing Hydrophobically Modified Magnesium Hydroxide Particles for Acid Neutralization-Mediated Anti-Inflammation

BACKGROUND

Poly(lactic-co-glycolic acid) (PLGA) microspheres have been actively used in various pharmaceutical formulations because they can sustain active pharmaceutical ingredient release and are easy to administer into the body using a syringe. However, the acidic byproducts produced by the decomposition of PLGA cause inflammatory reactions in surrounding tissues, limiting biocompatibility. Magnesium hydroxide (MH), an alkaline ceramic, has attracted attention as a potential additive because it has an acid-neutralizing effect.

METHODS

To improve the encapsulation efficiency of hydrophilic MH, the MH particles were capped with hydrophobic ricinoleic acid (RA-MH). PLGA microspheres encapsulated with RA-MH particles were manufactured by the O/W method. To assess the in vitro cytotoxicity of the degradation products of PLGA, MH/PLGA, and RA-MH/PLGA microspheres, CCK-8 and Live/Dead assays were performed with NIH-3T3 cells treated with different concentrations of their degradation products. In vitro anti-inflammatory effect of RA-MH/PLGA microspheres was evaluated with quantitative measurement of pro-inflammatory cytokines.

RESULTS

The synthesized RA-MH was encapsulated in PLGA microspheres and displayed more than four times higher loading content than pristine MH. The PLGA microspheres encapsulated with RA-MH had an acid-neutralizing effect better than that of the control group. In an in vitro cell experiment, the degradation products obtained from RA-MH/PLGA microspheres exhibited higher biocompatibility than the degradation products obtained from PLGA microspheres. Additionally, the RA-MH/PLGA microsphere group showed an excellent anti-inflammatory effect.

CONCLUSION

Our results proved that RA-MH-encapsulated PLGA microspheres showed excellent biocompatibility with an anti-inflammatory effect. This technology can be applied to drug delivery and tissue engineering to treat various incurable diseases in the future.

Biocompatible and functional inorganic magnesium ceramic particles for biomedical applications

Magnesium ceramics hold promise for numerous biological applications. This review covers the synthesis of magnesium ceramic particles with specific morphologies and potential modification techniques. Magnesium ceramic particles possess multiple characteristics directly applicable to human biology; they are anti-inflammatory, antibacterial, antiviral, and offer anti-cancer effects. Based on these advantages, magnesium hydroxide nanoparticles have been extensively utilized across biomedical fields. In a vascular stent, the incorporation of magnesium ceramic nanoparticles enhances re-endothelialization. Additionally, tissue regeneration for bone, cartilage, and kidney can be promoted by magnesium ceramics. This review enables researchers to identify the optimum synthetic conditions to prepare magnesium ceramics with specific morphologies and sizes and select the appropriate modification protocols. It is also intended to elucidate the desirable physicochemical properties and biological benefits of magnesium ceramics.

Recent Advances in Bioplastics: Application and Biodegradation

The success of oil-based plastics and the continued growth of production and utilisation can be attributed to their cost, durability, strength to weight ratio, and eight contributions to the ease of everyday life. However, their mainly single use, durability and recalcitrant nature have led to a substantial increase of plastics as a fraction of municipal solid waste. The need to substitute single use products that are not easy to collect has inspired a lot of research towards finding sustainable replacements for oil-based plastics. In addition, specific physicochemical, biological, and degradation properties of biodegradable polymers have made them attractive materials for biomedical applications. This review summarises the advances in drug delivery systems, specifically design of nanoparticles based on the biodegradable polymers. We also discuss the research performed in the area of biophotonics and challenges and opportunities brought by the design and application of biodegradable polymers in tissue engineering. We then discuss state-of-the-art research in the design and application of biodegradable polymers in packaging and emphasise the advances in smart packaging development. Finally, we provide an overview of the biodegradation of these polymers and composites in managed and unmanaged environments.

Magnesium hydroxide-incorporated PLGA composite attenuates inflammation and promotes BMP2-induced bone formation in spinal fusion

Spinal fusion has become a common surgical technique to join two or more vertebrae to stabilize a damaged spine; however, the rate of pseudarthrosis (failure of fusion) is still high. To minimize pseudarthrosis, bone morphogenetic protein-2 (BMP2) has been approved for use in humans. In this study, we developed a poly(lactide-co-glycolide) (PLGA) composite incorporated with magnesium hydroxide (MH) nanoparticles for the delivery of BMP2. This study aimed to evaluate the effects of released BMP2 from BMP2-immobilized PLGA/MH composite scaffold in an in vitro test and an in vivo mice spinal fusion model. The PLGA/MH composite films were fabricated via solvent casting technique. The surface of the PLGA/MH composite scaffold was modified with polydopamine (PDA) to effectively immobilize BMP2 on the PLGA/MH composite scaffold. Analyzes of the scaffold revealed that using PLGA/MH-PDA improved hydrophilicity, degradation performance, neutralization effects, and increased BMP2 loading efficiency. In addition, releasing BMP2 from the PLGA/MH scaffold significantly promoted the proliferation and osteogenic differentiation of MC3T3-E1 cells. Furthermore, the pH neutralization effect significantly increased in MC3T3-E1 cells cultured on the BMP2-immobilized PLGA/MH scaffold. In our animal study, the PLGA/MH scaffold as a BMP2 carrier attenuates inflammatory responses and promotes BMP2-induced bone formation in posterolateral spinal fusion model. These results collectively demonstrate that the BMP2-immobilized PLGA/MH scaffold offers great potential in effectively inducing bone formation in spinal fusion surgery.

Modification of Oligo- and Polylactides With Macrocyclic Fragments: Synthesis and Properties

Products of lactic acid polycondensation (poly- and oligolactic acids) are widely used as packaging materials, drug delivery agents, implants etc. Variety of their applications is caused by a number of practically important properties, e.g., biocompatibility and biodegradability, non-toxicity, and mechanical durability. Modification of these polymers with different additives allows improving their properties and extending future applications. In this manner, stability toward degradation, recognition of some substrates, extended thermal stability etc. can be improved. Macrocyclic compounds are promising candidates as modifiers. They are able to provide polymer materials with additional binding sites, impart certain orientation to spatial arrangement of polymer chains, change hydrophilic-lipophilic balance, and redox properties. The latter one can be used for assembling various electrochemical sensors and biosensors that combine steric discrimination of the analytes caused by oligolactides and highly sensitive response to their quantities caused by redox labels introduced. Different composite materials based on oligolactides as matrices for such redox labels were described in the assemblies of biosensors for drugs, pesticides, and antioxidants detection. In this mini-review, methods for the synthesis of the lactic acid oligomers and those modified with the macrocyclic fragments (porphyrin, cyclodextrin, and cyclophane) have been described. The effects of modifiers on complexation, thermal, and aggregation properties of materials are described. Analytical performance of oligolactide based sensors and biosensors has been considered with particular emphasis to the mechanism of signal generation.

Biodegradable Magnesium-Incorporated Poly(l-lactic acid) Microspheres for Manipulation of Drug Release and Alleviation of Inflammatory Response

Poly(l-lactic acid) (PLLA) and magnesium (Mg) are widely concerned biodegradable materials, but during in vivo implantation, the former produces acidic degradation byproducts and can easily induce inflammation in surrounding tissues, whereas the latter is fast corroded and generates alkaline products. The purpose of this study is to develop Mg/PLLA composite microspheres as a novel delivery system, in which Mg particles are used to regulate the drug release profile and suppress PLLA-induced inflammatory response. Morphological observation shows that multiple Mg particles are dispersed both on the surface and in the interior of composite microspheres. In vitro release study indicates that by varying the Mg contents or its particle sizes, the internal connectivity of composite microspheres is changed during hydrolytic degradation, and drug delivery can be facilely manipulated with tunable release patterns. In vivo release study further confirms the feasibility of Mg/PLLA microspheres for tailoring drug release in a physiological environment. The animal experiment reveals that Mg particles can alleviate macrophage infiltration and inflammatory cytokine expression. These results demonstrate the availability of using biodegradable Mg particles to manipulate drug release as well as alleviate PLLA-induced inflammation. The present Mg/PLLA composite microspheres have potential applications in controlled delivery of various therapeutic agents, especially some growth factors, for bone regeneration.

Fabrication, Crystalline Behavior, Mechanical Property and In-Vivo Degradation of Poly(l-lactide) (PLLA)-Magnesium Oxide Whiskers (MgO) Nano Composites Prepared by In-Situ Polymerization

The present work focuses on the preparation of poly(l-lactide)-magnesium oxide whiskers (PLLA-MgO) composites by the in-situ polymerization method for bone repair and implant. PLLA-MgO composites were evaluated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and solid-state 13C and 1H nuclear magnetic resonance spectroscopy (NMR). It was found that the whiskers were uniformly dispersed in the PLLA matrix through the interfacial interaction bonding between PLLA and MgO; thereby, the MgO whisker was found to be well-distributed in the PLLA matrix, and biocomposites with excellent interface bonding were produced. Notably, the MgO whisker has an effect on the crystallization behavior and mechanical properties; moreover, the in vivo degradation of PLLA-MgO composites could also be adjusted by MgO. These results show that the whisker content of 0.5 wt % and 1.0 wt % exhibited a prominent nucleation effect for the PLLA matrix, and specifically 1.0 wt % MgO was found to benefit the enhanced mechanical properties greatly. In addition, the improvement of the degrading process of the composite illustrated that the MgO whisker can effectively regulate the degradation of the PLLA matrix as well as raise its bioactivity. Hence, these results demonstrated the promising application of PLLA-MgO composite to serve as a biomedical material for bone-related repair.

One step bulk modification of poly(L-lactic acid) composites with functional additives to improve mechanical and biological properties for cardiovascular implant applications

Poly(L-lactic acid) (PLLA) has been widely used as a promising biomaterial in biomedical applications due to its biodegradability and high mechanical strength. However, because of the inherent brittleness, low impact resistance, and weak thermal stability of PLLA, the modification process is usually required to utilize it for biomedical devices. Furthermore, acidic byproducts resulting from the hydrolysis of PLLA after implantation reduce the pH of the surrounding environment and cause inflammatory responses in the implanted area, leading to the failure of their clinical applications. To this end, here, we demonstrate a novel modification process for the PLLA composite with various functional additives, such as cis-aconitic anhydride (AA), triacetin (TA), isosorbide derivative (ISB), and/or Pluronic® F127 (F). The modified PLLA composite with TA and F (PLLA/TF) showed significantly improved elongation at break and Young's modulus and retained tensile strength. Moreover, incorporating magnesium hydroxide (MH) nanoparticles (PLLA/TFMH) significantly reduced acid-induced inflammation responses caused by the acidic degradation products of PLLA. Reduced plasma protein adsorption was observed in the PLLA/TFMH. These results suggest that the one step bulk modification of biodegradable PLLA using TA, F, and MH will have great potential in cardiovascular implant applications.

A Bioinspired Scaffold with Anti-Inflammatory Magnesium Hydroxide and Decellularized Extracellular Matrix for Renal Tissue Regeneration

Kidney diseases are a worldwide public health issue. Renal tissue regeneration using functional scaffolds with biomaterials has attracted a great deal of attention due to limited donor organ availability. Here, we developed a bioinspired scaffold that can efficiently induce renal tissue regeneration. The bioinspired scaffold was designed with poly(lactide-co-glycolide) (PLGA), magnesium hydroxide (Mg(OH)2), and decellularized renal extracellular matrix (ECM). The Mg(OH)2 inhibited materials-induced inflammatory reactions by neutralizing the acidic microenvironment formed by degradation products of PLGA, and the acellular ECM helped restore the biological function of kidney tissues. When the PLGA/ECM/Mg(OH)2 scaffold was implanted in a partially nephrectomized mouse model, it led to the regeneration of renal glomerular tissue with a low inflammatory response. Finally, the PLGA/ECM/Mg(OH)2 scaffold was able to restore renal function more effectively than the control groups. These results suggest that the bioinspired scaffold can be used as an advanced scaffold platform for renal disease treatment.

The Degradation Properties of MgO Whiskers/PLLA Composite In Vitro

In this study, composite films of stearic acid⁻modified magnesium oxide whiskers (Sa⁻w-MgO)/poly-l-lactic acid (PLLA) were prepared through solution casting, and the in vitro degradation properties and cytocompatibility of the composites with different whisker contents were investigated. The results showed that the degradation behavior of the composite samples depended significantly on the whisker content, and the degradation rate increased with the addition of MgO content. Furthermore, the degradation of the composites with higher contents of whiskers was influenced more severely by the hydrophilicity and pH value, leading to more final weight loss, but the decomposition rate decreased gradually. Furthermore, the pH value of the phosphate buffer solution (PBS) was obviously regulated by the dissolution of MgO whiskers through neutralization of the acidic product of PLLA degradation. The cytocompatibility of the composites also increased remarkably, as determined from the cell viability results, and was higher than that of PLLA at the chosen whisker content. This was beneficial for the cell affinity of the material, as it notably led to an enhanced biocompatibility of the PLLA, in favor of promoting cell proliferation, which significantly improved its bioactivity, as well.

Synergistically enhanced osteoconductivity and anti-inflammation of PLGA/β-TCP/Mg(OH)2 composite for orthopedic applications

Synthetic biodegradable polymers including poly(lactide-co-glycolide) (PLGA) have been widely used as alternatives to metallic implantable materials in the orthopedic field due to their superior biocompatibility and biodegradability. However, weak mechanical properties of the biodegradable polymers and inflammatory reaction caused by the acidic degradation products have limited their biomedical applications. In this study, we have developed a PLGA composite containing beta-tricalcium phosphate (β-TCP) and magnesium hydroxide (Mg(OH)₂) as additives to improve mechanical, osteoconductivity, and anti-inflammation property of the biopolymer composite simultaneously. The β-TCP has an osteoconductive effect and the Mg(OH)₂ has a pH neutralizing effect. The PLGA/inorganic composites were uniformly blended via a twin extrusion process. The mechanical property of the PLGA/β-TCP/Mg(OH)₂ composite was improved compared to the pure PLGA. In particular, the addition of Mg(OH)₂ suppressed the inflammatory reaction of normal human osteoblast (NHOst) cells and also inhibited the differentiation of pre-osteoclastic cells into osteoclasts. Moreover, synergistically upregulated late osteogenic differentiation of NHOst cells was observed on the PLGA/β-TCP/Mg(OH)₂ composite. Taken all together, we believe that the use of β-TCP and Mg(OH)₂ as additives with synthetic biodegradable polymers has great potential by the synergistic effect in orthopedic applications.

Modified Magnesium Hydroxide Nanoparticles Inhibit the Inflammatory Response to Biodegradable Poly(lactide- co-glycolide) Implants

Biodegradable polymers have been extensively used in biomedical applications, ranging from regenerative medicine to medical devices. However, the acidic byproducts resulting from degradation can generate vigorous inflammatory reactions, often leading to clinical failure. We present an approach to prevent acid-induced inflammatory responses associated with biodegradable polymers, here poly(lactide- co-glycolide), by using oligo(lactide)-grafted magnesium hydroxide (Mg(OH)₂) nanoparticles, which neutralize the acidic environment. In particular, we demonstrated that incorporating the modified Mg(OH)₂ nanoparticles within degradable coatings on drug-eluting arterial stents efficiently attenuates the inflammatory response and in-stent intimal thickening by more than 97 and 60%, respectively, in the porcine coronary artery, compared with that of drug-eluting stent control. We also observed that decreased inflammation allows better reconstruction of mouse renal glomeruli in a kidney tissue regeneration model. Such modified Mg(OH)₂ nanoparticles may be useful to extend the applicability and improve clinical success of biodegradable devices used in various biomedical fields.

Versatile effects of magnesium hydroxide nanoparticles in PLGA scaffold-mediated chondrogenesis

Artificial scaffolds made up of various synthetic biodegradable polymers have been reported to have many advantages including cheap manufacturing, easy scale up, high mechanical strength, convenient manipulation, and molding into an unlimited variety of shapes. However, the synthetic biodegradable polymers still have the insufficiency for cartilage regeneration owing to their acidic degradation products. To reduce acidification by degradation of synthetic polymers, we incorporated magnesium hydroxide (MH) nanoparticles into porous polymer scaffold not only to effectively neutralize the acidic hydrolysate but also to minimize the structural disturbance of scaffolds. The neutralization effect of poly(D,L-lactic-co-glycolic acid; PLGA)/MH scaffold was confirmed with the maintenance of neutral pH, contrary to a PLGA scaffold with low pH. Further, the scaffolds were applied to evaluate the chondrogenic differentiation of the human bone marrow mesenchymal stem cells. In in vitro study, the PLGA/MH scaffold enhanced the chondrogenesis markers and reduced the calcification, compared to the PLGA scaffold. Additionally, the PLGA/MH scaffold reduced the release of inflammatory cytokines, compared to the PLGA scaffold, as the cell death decreased. Moreover, the addition of MH reduced necrotic cell death at the early stage of chondrogenic differentiation. Further, the necrotic cell death by the PLGA scaffold was mediated by cleavage of caspase-1, the so-called interleukin 1-converting enzyme, and MH alleviated it as well as nuclear factor kappa B expression. Furthermore, the PLGA/MH scaffold highly supported chondrogenic healing of rat osteochondral defect sites in in vivo study. Therefore, it was suggested that a synthetic polymer scaffold containing MH could be a novel healing tool to support cartilage regeneration and further treatment of orthopedic patients.

STATEMENT OF SIGNIFICANCE

Synthetic polymer scaffolds have been widely utilized for tissue regeneration. However, they have a disadvantage of releasing acidic products through degradation. This paper demonstrated a novel type of synthetic polymer scaffold with pH-neutralizing ceramic nanoparticles composed of magnesium hydroxide for cartilage regeneration. This polymer showed pH-neutralization property during polymer degradation and significant enhancement of chondrogenic differentiation of mesenchymal stem cells. It reduced not only chondrogenic calcification but also release of proinflammatory cytokines. Moreover, it has an inhibitory effect on necrotic cell death, particularly caspase-1-mediated necrotic cell death (pyroptosis). In in vivo study, it showed higher healing rate of the damaged cartilage in a rat osteochondral defect model. We expected that this novel type of scaffold can be effectively applied to support cartilage regeneration and further treatment of orthopedic patients.

Recent progress in the synthesis of nanostructured magnesium hydroxide

This highlight discusses magnesium hydroxide design at the nanoscale, common aspects of crystallite growth and how nanostructuring impacts properties.

Via precise interface engineering towards bioinspired composites with improved 3D printing processability and mechanical properties

Precise interface engineering in inorganic–organic hybrid materials enhances both the elastic moduli and toughness of a biodegradable composite, which is of relevance for load-bearing applications in bone tissue engineering.

Effects of poly(L-lactide-ε-caprolactone) and magnesium hydroxide additives on physico-mechanical properties and degradation of poly(L-lactic acid)

BACKGROUND

Biodegradable poly(L-lactic acid) (PLLA) is one of the most widely used polymer in biomedical devices, but it still has limitations such as inherent brittleness and acidic degradation products. In this work, PLLA blends with poly(L-lactide-ε-caprolactone) (PLCL) and Mg(OH)2 were prepared by the thermal processing to improve their physico-mechanical and thermal properties. In addition, the neutralizing effect of Mg(OH)2 was evaluated by degradation study.

RESULTS

The elongation of PLLA remarkably increased from 3 to 164.4 % and the glass transition temperature (Tg) of PLLA was slightly reduced from 61 to 52 °C by adding PLCL additive. Mg(OH)2 in polymeric matrix not only improved the molecular weight reduction and mechanical strength of PLLA, but also neutralized the acidic byproducts generated during polyester degradation.

CONCLUSIONS

Therefore, the results demonstrated that the presence of PLCL and Mg(OH)2 additives in PLLA matrix could prevent the thermal decomposition and control degradation behavior of polyester.

The crystallization behaviors and mechanical properties of poly(l-lactic acid)/magnesium oxide nanoparticle composites

Nanocomposites of biodegradable PLLA and magnesium oxide composite (PLLA/MgO-NPs) and surface modified magnesium oxide composite (PLLA/m-MgO-NPs) were prepared using a solution casting method.

The potential of 3-dimensional construct engineered from poly(lactic-co-glycolic acid)/fibrin hybrid scaffold seeded with bone marrow mesenchymal stem cells for in vitro cartilage tissue engineering

Articular cartilage is well known for its simple uniqueness of avascular and aneural structure that has limited capacity to heal itself when injured. The use of three dimensional construct in tissue engineering holds great potential in regenerating cartilage defects. This study evaluated the in vitro cartilaginous tissue formation using rabbit's bone marrow mesenchymal stem cells (BMSCs)-seeded onto poly(lactic-co-glycolic acid) PLGA/fibrin and PLGA scaffolds. The in vitro cartilaginous engineered constructs were evaluated by gross inspection, histology, cell proliferation, gene expression and sulphated glycosaminoglycan (sGAG) production at week 1, 2 and 3. After 3 weeks of culture, the PLGA/fibrin construct demonstrated gross features similar to the native tissue with smooth, firm and glistening appearance, superior histoarchitectural and better cartilaginous extracellular matrix compound in concert with the positive glycosaminoglycan accumulation on Alcian blue. Significantly higher cell proliferation in PLGA/fibrin construct was noted at day-7, day-14 and day-21 (p<0.05 respectively). Both constructs expressed the accumulation of collagen type II, collagen type IX, aggrecan and sox9, showed down-regulation of collagen type I as well as produced relative sGAG content with PLGA/fibrin construct exhibited better gene expression in all profiles and showed significantly higher relative sGAG content at each time point (p<0.05). This study suggested that with optimum in vitro manipulation, PLGA/fibrin when seeded with pluripotent non-committed BMSCs has the capability to differentiate into chondrogenic lineage and may serve as a prospective construct to be developed as functional tissue engineered cartilage.

A novel pseudo-protein-based biodegradable coating for magnesium substrates: in vitro corrosion phenomena and cytocompatibility

The goal of this study is to examine whether a member of the newly developed biodegradable pseudo-protein biomaterial family could provide a far better protection and performance than the popular hydrolytically degradable poly(glycolide-co-lactide) (PLGA) biomaterial on an experimental magnesium substrate as a model.

Facile fabrication of poly(L-lactic acid)-grafted hydroxyapatite/poly(lactic-co-glycolic acid) scaffolds by Pickering high internal phase emulsion templates

Porous scaffolds consisting of bioactive inorganic nanoparticles and biodegradable polymers have gained much interest in bone tissue engineering. We report here a facile approach to fabricating poly(l-lactic acid)-grafted hydroxyapatite (g-HAp)/poly(lactide-co-glycolide) (PLGA) nanocomposite (NC) porous scaffolds by solvent evaporation of Pickering high internal phase emulsion (HIPE) templates, where g-HAp nanoparticles act as particulate stabilizers. The resultant porous scaffolds exhibit an open and rough pore structure. The pore structure and mechanical properties of the scaffolds can be tuned readily by varying the g-HAp nanoparticle concentration and internal phase volume fraction of the emulsion templates. With increasing the g-HAp concentration or decreasing the internal phase volume fraction, the pore size and the porosity decrease, while the Young's modulus and the compressive stress enhance. Moreover, the in vitro mineralization tests show that the bioactivity of the scaffolds increases with increasing the g-HAp concentration. Furthermore, the anti-inflammatory drug ibuprofen (IBU) is loaded into the scaffolds, and the drug release studies indicate that the loaded-IBU exhibits a sustained release profile. Finally, in vitro cell culture assays prove that the scaffolds are biocompatible because of supporting adhesion, spreading, and proliferation of mouse bone mesenchymal stem cells. All the results indicate that the solvent evaporation based on Pickering HIPE templates is a promising alternative method to fabricate NC porous scaffolds for potential bone tissue engineering applications.

A poly(lactide) stereocomplex structure with modified magnesium oxide and its effects in enhancing the mechanical properties and suppressing inflammation

Biodegradable polymers such as poly(L-lactide) (PLLA) have been widely utilized as materials for biomedical applications. However, the relatively poor mechanical properties of PLLA and its acid-induced cell inflammation brought about by the acidic byproducts during biodegradation pose severe problems. In this study, these drawbacks of PLLA are addressed using a stereocomplex structure, where oligo-D-lactide-grafted magnesium hydroxide (MgO-ODLA) is synthesized by grafting d-lactide onto the surface of magnesium hydroxide, which is then blended with a PLLA film. The structure, morphology, pH change, thermal and mechanical properties, in-vitro cytotoxicity, and inflammation effect of the MgO-ODLAs and their PLLA composites are evaluated through various analyses. The PLLA/MgO70-ODLA30 (0-20 wt%) composite with a stereocomplex structure shows a 20% increase in its tensile strength and an improvement in the modulus compared to its oligo-L-lactide (PLLA/MgO70-OLLA30) counterpart. The interfacial interaction parameter of PLLA/MgO70-ODLA30 (5.459) has superior properties to those of PLLA/MgO70-OLLA30 (4.013) and PLLA/Mg(OH)2 (1.774). The cell cytotoxicity and acid-induced inflammatory response are suppressed by the neutralizing effect of the MgO-ODLAs. In addition, the inflammatory problem caused by the rapid acidification of the stereocomplex structure is also addressed. As a result, the stereocomplex structure of the MgO-ODLA/PLLA composite can be used to overcome the problems associated with the biomedical applications of PLLA films.