Biomechanical Properties and Biocompatibility of a Non-Absorbable Elastic Thread.

To date, extensive studies have been conducted to assess diverse types of sutures. But there is a paucity of data regarding biomechanical properties of commonly used suture materials. In the current experiment, we compared biomechanical properties and biocompatibility, such as tensile strength and elongation, the degree of bovine serum albumin (BSA) release, in vitro cytotoxicity and ex vivo frictional properties, between a non-absorbable elastic thread (NAT; HansBiomed Co. Ltd., Seoul, Korea) (NAT-R: NAT with a rough surface, NAT-S: NAT with a smooth surface) and the Elasticum® (Korpo SRL, Genova, Italy). The degree of tensile strength and elongation of Si threads was significantly higher in both the NAT-R and -S as compared with the Elasticum® (p < 0.05). Moreover, the degree of tensile strength and elongation of PET threads was significantly lower in both NAT-R and -S as compared with the Elasticum® (p < 0.05). Furthermore, the degree of tensile strength and elongation of braided Si/PET threads was significantly lower in NAT-S as compared with NAT-R and Elasticum® (p < 0.05). The degree of BSA release was significantly higher in the NAT-R as compared with Elasticum® and NAT-S throughout a 2-h period in the descending order (p < 0.05). The degree of cell viability was significantly higher in both NAT-R and -S as compared with Elasticum® (p < 0.05). The degree of coefficient of friction as well as the frictional force and strength was significantly higher in NAT-R as compared with NAT-S and Elasticum® (p < 0.05). NAT had a higher degree of biomechanical properties and biocompatibility as compared with Elasticum®. But further experimental and clinical studies are warranted to compare the efficacy, safety, and potential role as a carrier for drug delivery between NAT and Elasticum®.

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 Safety and Regeneration of Long-Term Transported Amniotic Fluid Stem Cells for Renal Regeneration.

BACKGROUND: Despite major progress in stem cell therapy, our knowledge of the characteristics and tissue regeneration potency of long-term transported cells is insufficient. In a previous in vitro study, we established the optimal cell transport conditions for amniotic fluid stem cells (AFSCs). In the present study, the target tissue regeneration of long-term transported cells was validated in vivo. METHODS: For renal regeneration, transported AFSCs were seeded on a poly(lactide-co-glycolide) scaffold and implanted in a partially resected kidney. The target tissue regeneration of the transported cells was compared with that of freshly harvested cells in terms of morphological reconstruction, histological microstructure reformation, immune cell infiltration, presence of induced cells, migration into remote organs, expression of inflammation/fibrosis/renal differentiation-related factors, and functional recovery. RESULTS: The kidney implanted with transported cells showed recovery of total kidney volume, regeneration of glomerular/renal tubules, low CD4/CD8 infiltration, and no occurrence of cancer during 40 weeks of observation. The AFSCs gradually disappeared and did not migrate into the liver, lung, or spleen. We observed low expression levels of pro-inflammatory cytokines and fibrotic factors; enhanced expression of the genes Wnt4, Pax2, Wt1, and Emx2; and significantly reduced blood urea nitrogen and creatinine values. There were no statistical differences between the performance of freshly harvested cells and that of the transported cells. CONCLUSION: This study demonstrates that long-term transported cells under optimized conditions can be used for cell therapy without adverse effects on stem cell characteristics, in vivo safety, and tissue regeneration potency.

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.

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.

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.

Fabrication and characteristics of dual functionalized vascular stent by spatio-temporal coating.

UNLABELLED: Stent implantation with balloon angioplasty is a widely used treatment for coronary artery diseases. Stents have been developed from bare metal stent (BMS) to advanced forms such as drug-eluting stent (DES). However, modern DES still causes thrombosis and/or in-stent restenosis as long-term outcomes. For effective prevention of these problems, we fabricated a dual functionalized stent using spatio-temporal coating, which has two different surfaces, as a novel type of DES. Hyaluronic acid conjugated with dopamine (HA-DA) was applied to a bare cobalt-chromium (CC) stent prior to abluminal coating of sirolimus (SRL)-in-polymer such as poly(d,l-lactide). The SRL-in-polymer (P+S) coated on the abluminal surface of the HA-DA modified stent showed highly stable coating layer and prevented the crack formation after ballooning. In the blood- and cyto-compatibility tests, HA-DA coating displayed suppressive effects on adhesion and activation of platelets and maintained the cell viability and proliferation of human coronary artery endothelial cells even under the existence of SRL. In in vivo study using porcine restenosis model, the neointimal area and inflammation score of the dual functionalized stent with HA-DA and P+S were significantly reduced than those of BMS. It is expected that this novel type of DES can be effectively applied to utilize diverse anti-proliferative drugs and bioactive polymers. STATEMENT OF SIGNIFICANCE: Stents have been developed from bare metal stent to advanced forms such as drug-eluting stents (DESs). However, even DESs can still cause in-stent restenosis as long-term outcomes. This paper demonstrated a novel DES using spatio-temporal coating by dopamine-mediated hyaluronic acid coating (HA-DA) before asymmetric coating of sirolimus-in-poly(d,l-lactide) (P+S). It showed stable coating surface and prevented crack formation after ballooning. HA-DA coating also had an inhibitive effect on adhesion of platelets and maintained cell viability of endothelial cells even under the existence of sirolimus. Additionally, in vivo neointima area and inflammation score of HA-DA/P+S stent significantly decreased than those of BMS. We expected that this novel type of DES can be effectively applied to introduce diverse anti-proliferative drugs and bioactive molecules.

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.

Synergistic effect of anti-platelet and anti-inflammation of drug-coated Co-Cr substrates for prevention of initial in-stent restenosis.

Antiplatelet and antithrombotic therapies are systematically considered to prevent restenosis following coronary stent implantation. Currently, patients receiving medicated stents are prescribed to orally take anticoagulants and antiplatelet drugs such as aspirin (ASP) and prasugrel (PRAS). Propolis (PROP) known as a natural organic compound was recently evaluated for its antiplatelet activity, antibiotics and immunomodulatory activities. In this study, antiplatelet drug-coated Co-Cr substrates were prepared with biodegradable poly(d,l-lactide) (PDLLA) containing ASP, PRA, or PROP using electrospray and the blood compatibility of the different substrates was investigated by measuring protein adsorption and platelet adhesion. In addition, the anti-inflammatory properties of the modified Co-Cr surfaces were assessed by measuring IL-8 and IL-6 expression levels in human endothelial cell cultures. Drug-coated surfaces were found to resist the adsorption of fibrinogen when compared to bare Co-Cr or PDLLA-coated Co-Cr. Interestingly, ASP- and PROP-containing substrates not only showed reduced adhesion of platelets and delayed coagulation time, but also drastically reduced the expression level of IL-8 and IL-6. Such results are supported that ASP- or PROP-coated Co-Cr can be potentially used as a stent material to mitigate early stage of restenosis. The developed coating materials might be an interesting alternative to systemic anticoagulant therapies prescribed after stent implantation.

Optimal conjugation of catechol group onto hyaluronic acid in coronary stent substrate coating for the prevention of restenosis.

Although endovascular stenting has been used as an interventional therapy to treat cardio- and cerebro-vascular diseases, it is associated with recurrent vascular diseases following stent thrombosis and in-stent restenosis. In this study, a metallic stent was coated with dopamine-conjugated hyaluronic acid with different ratios of catechol group to improve hemocompatibility and re-endothelialization. Especially, we were interested in how much amount of catechol group is appropriate for the above-mentioned purposes. Therefore, a series of dopamine-conjugated hyaluronic acid conjugates with different ratios of catechol group were synthesized via a carbodiimide coupling reaction. Dopamine-conjugated hyaluronic acid conjugates were characterized with 1H-nuclear magnetic resonance and Fourier transform infrared spectroscopy, and the amount of catechol group in dopamine-conjugated hyaluronic acid was measured by ultraviolet spectrometer. Co-Cr substrates were polished and coated with various dopamine-conjugated hyaluronic acid conjugates under pH 8.5. Dopamine-conjugated hyaluronic acid amounts on the substrate were quantified by micro-bicinchoninic acid assay. Surface characteristics of dopamine-conjugated hyaluronic-acid-coated Co-Cr were evaluated by water contact angle, scanning electron microscopy, and atomic force microscopy. The hemocompatibility of the surface-modified substrates was assessed by protein adsorption and platelet adhesion tests. Adhesion and activation of platelets were confirmed with scanning electron microscopy and lactate dehydrogenase assay. Human umbilical vein endothelial cells were cultured on the substrates, and the viability, adhesion, and proliferation were investigated through cell counting kit-8 assay and fluorescent images. Obtained results demonstrated that optimal amounts of catechol group (100 µmol) in the dopamine-conjugated hyaluronic acid existed in terms of various properties such as hemocompatibility and cellular responses.

In situ formation of enzyme-free hydrogels via ferromagnetic microbead-assisted enzymatic cross-linking.

In situ formation of horseradish peroxidase (HRP)-free gelatin hydrogels was achieved via ferromagnetic microbead-assisted enzymatic cross-linking. Gelation time and mechanical stiffness of the hydrogels can be tuned in situ, which makes HRP-free gelatin hydrogels suitable for injectable cell delivery.

Shape-memory effect by specific biodegradable polymer blending for biomedical applications.

Specific biodegradable polymers having shape-memory properties through "polymer-blend" method are investigated and their shape-switching in body temperature (37 °C) is characterized. Poly(L-lactide-co-caprolactone) (PLCL) and poly(L-lactide-co-glycolide) (PLGA) are dissolved in chloroform and the films of several blending ratios of PLCL/PLGA are prepared by solvent casting. The shape-memory properties of films are also examined using dynamic mechanical analysis (DMA). Among the blending ratios, the PLCL50/PLGA50 film shows good performance of shape-fixity and shape-recovery based on glass transition temperature. It displays that the degree of shape recovery is 100% at 37 °C and the shape recovery proceeds within only 15 s. In vitro biocompatibility studies are shown to have good blood compatibility and cytocompatibility for the PLCL50/PLGA50 films. It is expected that this blended biodegradable polymer can be potentially used as a material for blood-contacting medical devices such as a self-expended vascular polymer stents and vascular closure devices in biomedical applications.

Rapidly curable chitosan-PEG hydrogels as tissue adhesives for hemostasis and wound healing.

Chitosan-poly(ethylene glycol)-tyramine (CPT) hydrogels were rapidly formed in situ using horseradish peroxidase and hydrogen peroxide to explore their performance as efficient tissue adhesives. A poly(ethylene glycol) modified with tyramine was grafted onto a chitosan backbone to enhance the solubility of the chitosan and to crosslink into three-dimensional networks. The elastic modulus of the hydrogels could be controlled by changing the crosslinking conditions, and the mechanical strength influenced the tissue adhesiveness of the hydrogels. The hydrogels showed the adhesiveness ranging from 3- to 20-fold that of fibrin glue (Greenplast®). The hemostatic ability of the hydrogels was evaluated on the basis that bleeding from liver defects was significantly arrested by the combined effect of the adhesiveness of the hydrogels and the hemostatic property of the chitosan materials. The enzymatic crosslinking method enabled the water-soluble chitosan to rapidly form hydrogels within 5s of an incision into the skin of rats. Histological results demonstrated that the CPT hydrogels showed superior healing effects in the skin incision when compared to suture, fibrin glue and cyanoacrylate. By 2weeks post-implantation, the wound was completely recovered, with a newly formed dermis, due to the presence of the CPT hydrogels in the incision. These results suggest that the in situ curable chitosan hydrogels are very interesting and promising tissue adhesive devices for biomedical applications.

In situ forming and rutin-releasing chitosan hydrogels as injectable dressings for dermal wound healing.

An in situ gel-forming system composed of rutin- and tyramine-conjugated chitosan derivatives, horseradish peroxidase (HRP), and hydrogen peroxide (H(2)O(2)) was prepared and applied to dermal wound repair. Rutin was employed to enhance production and accumulation of extracellular matrix in the healing process. In vitro study demonstrates that released rutin significantly enhanced cell proliferation as compared with media without rutin. In vivo wound healing study was performed by injecting hydrogels on rat dorsal wounds with a diameter of 8 mm for 14 days. Histological results demonstrated that rutin-conjugated hydrogel exhibited enhancement of wound healing as compared with treatments with PBS, hydrogel without rutin, and a commercialized wound dressing (Duoderm). More specifically, rutin-conjugated hydrogels induced better defined formation of neo-epithelium and thicker granulation, which is closer to the original epithelial tissue. As a result, this study suggests that the in situ gel-forming system can be a promising injectable gel-type wound dressing.

Supramolecular hydrogels exhibiting fast in situ gel forming and adjustable degradation properties.

Fast in situ forming supramolecular hydrogels consisted of the tyramine-conjugated supramolecular structures and chitosan derivative were prepared via an enzymatic reaction with horseradish peroxidase (HRP) and hydrogen peroxide (H(2)O(2)). The gel formation was varied within a time period of 5 s to 10 min by controlling the concentrations of HRP, H(2)O(2), and polymers. Tyramine conjugation at different sites of the supramolecular structure resulted in significant changes in physical properties and the degradation time of the hydrogels that were confirmed by water uptake, compressive strength and degradation tests. In addition, the hydrogels showed a good cytocompatibility in vitro. These hydrogels could be promising injectable biomaterials with adjustable degradation times to control both the cellular behaviors as a regenerative cell matrix and the drug release behavior as a drug delivery vehicle.