Fabrication and characteristics of anti-inflammatory magnesium hydroxide incorporated PLGA scaffolds formed with various porogen materials

Porous PLGA microparticles prepared with nanosized/micronized sugar particles as porogens

The objective of this study was to explore the use of nanosized/micronized sugar particles as porogens for preparing porous poly(lactide-co-glycolide) (PLGA) microparticles by a solid-in-oil-in-water (S/O/W) solvent evaporation method. Porous PLGA microparticles containing dexamethasone were prepared with different nanosized/micronized sugars (sucrose, trehalose and lactose), types of PLGA, and osmogens (NaCl or sucrose) in the external water phase. The microparticles were characterized for morphology, thermal properties, particle size, surface area, encapsulation efficiency and drug release/swelling during release. The addition of nanosized/micronized sugar particles resulted in porous PLGA microparticles with high encapsulation efficiencies. The porosity of the microparticles was caused both by the influx of water into the polymer droplets and the encapsulation and subsequent dissolution of sugar particles during the manufacturing process. The porosity (pore size) of the microparticles and, as a result, the drug release pattern could be well controlled by the particle size and weight fraction of the sugar particles. Because of a larger inner surface area, nanosized sugar particles were more efficient porogen than micronized sugar particles to obtain porous PLGA microparticles with flexible release patterns.

Modern trends in the formulation of microparticles for lung delivery using porogens: methods, principles and examples

Inhalation drug administration is increasingly used for local pharmacotherapy of lung disorders and as an alternative route for systemic drug delivery. Modern inhalation powder systems aim to target drug deposition in the required site of action. Large porous particles (LPP), characterized by an aerodynamic diameter over 5 μm, density below 0.4 g/cm3, and the ability to avoid protective lung mechanisms, come to the forefront of the research. They are mostly prepared by spray techniques such as spray drying or lyophilization using pore-forming substances (porogens). These substances could be gaseous, solid, or liquid, and their selection depends on their polarity, solubility, and mutual compatibility with the carrier material and the drug. According to the pores-forming mechanism, porogens can be divided into groups, such as osmogens, extractable porogens, and porogens developing gases during decomposition. This review characterizes modern trends in the formulation of solid microparticles for lung delivery; describes the mechanisms of action of the most often used porogens, discusses their applicability in various formulation methods, emphasizes spray techniques; and documents discussed topics by examples from experimental studies.

3D-Printed Piezoelectric Porous Bioactive Scaffolds and Clinical Ultrasonic Stimulation Can Help in Enhanced Bone Regeneration

This paper presents a comprehensive effort to develop and analyze first-of-its-kind design-specific and bioactive piezoelectric scaffolds for treating orthopedic defects. The study has three major highlights. First, this is one of the first studies that utilize extrusion-based 3D printing to develop design-specific macroporous piezoelectric scaffolds for treating bone defects. The scaffolds with controlled pore size and architecture were synthesized based on unique composite formulations containing polycaprolactone (PCL) and micron-sized barium titanate (BaTiO3) particles. Second, the bioactive PCL-BaTiO3 piezoelectric composite formulations were explicitly developed in the form of uniform diameter filaments, which served as feedstock material for the fused filament fabrication (FFF)-based 3D printing. A combined method comprising solvent casting and extrusion (melt-blending) was designed and deemed suitable to develop the high-quality PCL-BaTiO3 bioactive composite filaments for 3D printing. Third, clinical ultrasonic stimulation (US) was used to stimulate the piezoelectric effect, i.e., create stress on the PCL-BaTiO3 scaffolds to generate electrical fields. Subsequently, we analyzed the impact of scaffold-generated piezoelectric stimulation on MC3T3 pre-osteoblast behavior. Our results confirmed that FFF could form high-resolution, macroporous piezoelectric scaffolds, and the poled PCL-BaTiO3 composites resulted in the d33 coefficient in the range of 1.2-2.6 pC/N, which is proven suitable for osteogenesis. In vitro results revealed that the scaffolds with a mean pore size of 320 µm resulted in the highest pre-osteoblast growth kinetics. While 1 Hz US resulted in enhanced pre-osteoblast adhesion, proliferation, and spreading, 3 Hz US benefited osteoblast differentiation by upregulating important osteogenic markers. This study proves that 3D-printed bioactive piezoelectric scaffolds coupled with US are promising to expedite bone regeneration in orthopedic defects.

Bioactive PCL microspheres with enhanced biocompatibility and collagen production for functional hyaluronic acid dermal fillers

Polymeric microspheres containing magnesium hydroxide (MH) and a bioactive agent (BA), such as apocynin (APO) and astaxanthin (ATX), have been prepared as functional dermal fillers with enhanced physicochemical and biological performance.

A double-layer dura mater based on poly(caprolactone-co-lactide) film and polyurethane sponge: preparation, characterization, and biodegradation study

Synthetic, biodegradable polymers hold great potential in dura mater substitution. In this study, a dura mater-mimetic double-layer film@sponge composite was developed. The composite contains a poly(caprolactone-co-lactide) (PCLA) film and polyurethane (PU) sponge, which simulates the hard and soft layers of dura mater, respectively. PCLA films were prepared by a solution-casting method and showed excellent mechanical properties and tolerance to water. PU sponge was hydrophilic and had a high water-absorption rate (about 500%). The double-layer composite (film@sponge) integrated the good mechanical properties of the films and the good water absorption of the sponge. The excellent biocompatibility and biodegradability of the PCLA film@PU sponge composites were verified by in vitro degradation and cytotoxicity study and the in vivo implantation in the back of rats. Importantly, the film@sponge composite had a suitable degradation rate and good biocompatibility, holding potential in the field of dural repair.

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.

Augmented re-endothelialization and anti-inflammation of coronary drug-eluting stent by abluminal coating with magnesium hydroxide

Drug-eluting stents (DESs) have been widely used as a treatment approach for coronary artery diseases. Generally, conventional DESs were fully covered with drugs and biodegradable polymers on both abluminal and luminal layers (i.e., conformal coating). However, uncontrolled drug release from the luminal drug-coating layer of the stent is known to inhibit re-endothelialization. Furthermore, the acidification of the surrounding tissue by the decomposed coating polymer causes inflammation, resulting in restenosis and late thrombosis. To overcome these limitations, here we demonstrated a functional DES coated with poly(lactic-co-glycolic acid) (PLGA), sirolimus (SRL), and magnesium hydroxide (Mg(OH)2, MH) precisely only on the abluminal layer. The acidic neutralization effect of MH was elucidated by measuring the pH change of the fabricated film in PBS solution. In an in vitro cell study, the stent coated with MH exhibited higher compatibility with human coronary artery endothelial cells (ECs) and a lower inflammation score as compared to the control stent. Finally, in an in vivo large porcine model, the abluminal coated DES with SRL and MH showed excellent re-endothelialization and anti-inflammatory and anti-thrombotic effects. In conclusion, it is believed that this approach has great potential for the development of functional DES for the treatment of cardiovascular diseases.

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.

In Vivo Validation Model of a Novel Anti-Inflammatory Scaffold in Interleukin-10 Knockout Mouse

BACKGROUND

We fabricated anti-inflammatory scaffold using Mg(OH)₂-incorporated polylactic acid-polyglycolic acid copolymer (MH-PLGA). To demonstrate the anti-inflammatory effects of the MH-PLGA scaffold, an animal model should be sensitive to inflammatory responses. The interleukin-10 knockout (IL-10 KO) mouse is a widely used bowel disease model for evaluating inflammatory responses, however, few studies have evaluated this mouse for the anti-inflammatory scaffold.

METHODS

To compare the sensitivity of the inflammatory reaction, the PLGA scaffold was implanted into IL-10 KO and C57BL/6 mouse kidneys. Morphology, histology, immunohistochemistry, and gene expression analyses were carried out at weeks 1, 4, 8, and 12. The anti-inflammatory effect and renal regeneration potency of the MH-PLGA scaffold was also compared to those of PLGA in IL-10 KO mice.

RESULTS

The PLGA scaffold-implanted IL-10 KO mice showed kidneys relatively shrunken by fibrosis, significantly increased inflammatory cell infiltration, high levels of acidic debris residue, more frequent CD8-, C-reactive protein-, and ectodysplasin A-positive cells, and higher expression of pro-inflammatory and fibrotic factors compared to the control group. The MH-PLGA scaffold group showed lower expression of pro-inflammatory and fibrotic factors, low immune cell infiltration, and significantly higher expression of anti-inflammatory factors and renal differentiation related genes compared to the PLGA scaffold group.

CONCLUSION

These results indicate that the MH-PLGA scaffold had anti-inflammatory effects and high renal regeneration potency. Therefore, IL-10 KO mice are a suitable animal model for in vivo validation of novel anti-inflammatory scaffolds.

Magnetically Coated Bioabsorbable Stents for Renormalization of Arterial Vessel Walls after Stent Implantation

The insertion of a stent in diseased arteries is a common endovascular procedure that can be compromised by the development of short- and long-term inflammatory responses leading to restenosis and thrombosis, respectively. While treatment with drugs, either systemic or localized, has decreased the incidence of restenosis and thrombosis these complications persist and are associated with a high mortality in those that present with stent thrombosis. We reasoned that if stents could be made to undergo accelerated endothelialization in the deployed region, then such an approach would further decrease the occurrence of stent thrombosis and restenosis thereby improving clinical outcomes. Toward that objective, the first step necessitated efficient capture of progenitor stem cells, which eventually would become the new endothelium. To achieve this objective, we engineered intrinsic ferromagnetism within nonmagnetizable, biodegradable magnesium (Mg) bare metal stents. Mg stents were coated with biodegradable polylactide (PLA) polymer embedding magnetizable iron-platinum (FePt) alloy nanoparticles, nanomagnetic particles, ⁿMags, which increased the surface area and hence magnetization of the stent. ⁿMags uniformly distributed on stents enabled capture, under flow, up to 50 mL/min, of systemically injected iron-oxide-labeled (IO-labeled) progenitor stem cells. Critical parameters enhancing capture efficiency were optimized, and we demonstrated the generality of the approach by showing that ⁿMag-coated stents can capture different cell types. Our work is a potential paradigm shift in engineering stents because implants are rendered as tissue in the body, and this "natural stealthiness" reduces or eliminates issues associated with pro-inflammatory immune responses postimplantation.

Preparation and Evaluations of Mangiferin-Loaded PLGA Scaffolds for Alveolar Bone Repair Treatment Under the Diabetic Condition

The aim of the present study was to prepare and evaluate a sustained-release mangiferin scaffold for improving alveolar bone defect repair in diabetes. Mangiferin-loaded poly(D,L-lactide-co-glycolide) (PLGA) scaffolds were prepared using a freeze-drying technique with ice particles as the porogen material. The produced scaffolds were examined using a scanning electron microscope (SEM). Drug content and drug release were detected using a spectrophotometer. Degradation behaviors were monitored as a measure of weight loss and examined using SEM. Then, the scaffolds were incubated with rat bone marrow stromal cells under the diabetic condition in vitro, and cell viability was assessed using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Afterward, the scaffolds were implanted into alveolar bone defects of diabetic rats, and bone repair was examined using hematoxylin and eosin staining. The fabricated scaffolds showed porous structures, with average pore size range from 111.35 to 169.45 μm. A higher PLGA concentration led to decreased average pore size. A lower PLGA concentration or a higher mangiferin concentration resulted in increased drug content. The prepared scaffolds released mangiferin in a sustained manner with relatively low initial burst during 10 weeks. Their degradation ratios gradually increased as degradation proceeded. The mangiferin-loaded scaffolds attenuated cell viability decrease under the diabetic condition in vitro. Moreover, they increased histological scorings of bone regeneration and improved delayed alveolar bone defect healing in diabetic rats. These results suggest that the produced mangiferin-loaded scaffolds may provide a potential approach in the treatment of impaired alveolar bone healing in diabetes.

Biomimetic Porous PLGA Scaffolds Incorporating Decellularized Extracellular Matrix for Kidney Tissue Regeneration

Chronic kidney disease is now recognized as a major health problem, but current therapies including dialysis and renal replacement have many limitations. Consequently, biodegradable scaffolds to help repairing injured tissue are emerging as a promising approach in the field of kidney tissue engineering. Poly(lactic-co-glycolic acid) (PLGA) is a useful biomedical material, but its insufficient biocompatibility caused a reduction in cell behavior and function. In this work, we developed the kidney-derived extracellular matrix (ECM) incorporated PLGA scaffolds as a cell supporting material for kidney tissue regeneration. Biomimetic PLGA scaffolds (PLGA/ECM) with different ECM concentrations were prepared by an ice particle leaching method, and their physicochemical and mechanical properties were characterized through various analyses. The proliferation of renal cortical epithelial cells on the PLGA/ECM scaffolds increased with an increase in ECM concentrations (0.2, 1, 5, and 10%) in scaffolds. The PLGA scaffold containing 10% of ECM has been shown to be an effective matrix for the repair and reconstitution of glomerulus and blood vessels in partially nephrectomized mice in vivo, compared with only PLGA control. These results suggest that not only can the tissue-engineering techniques be an effective alternative method for treatment of kidney diseases, but also the ECM incorporated PLGA scaffolds could be promising materials for biomedical applications including tissue engineered scaffolds and biodegradable implants.

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.