A Comparison of Three-Layer and Single-Layer Small Vascular Grafts Manufactured via the Roto-Evaporation Method.

This study used the roto-evaporation technique to engineer a 6 mm three-layer polyurethane vascular graft (TVG) that mimics the architecture of human coronary artery native vessels. Two segmented polyurethanes were synthesized using lysine (SPUUK) and ascorbic acid (SPUAA), and the resulting materials were used to create the intima and adventitia layers, respectively. In contrast, the media layer of the TVG was composed of a commercially available polyurethane, Pearlbond 703 EXP. For comparison purposes, single-layer vascular grafts (SVGs) from individual polyurethanes and a polyurethane blend (MVG) were made and tested similarly and evaluated according to the ISO 7198 standard. The TVG exhibited the highest circumferential tensile strength and longitudinal forces compared to single-layer vascular grafts of lower thicknesses made from the same polyurethanes. The TVG also showed higher suture and burst strength values than native vessels. The TVG withstood up to 2087 ± 139 mmHg and exhibited a compliance of 0.15 ± 0.1%/100 mmHg, while SPUUK SVGs showed a compliance of 5.21 ± 1.29%/100 mmHg, akin to coronary arteries but superior to the saphenous vein. An indirect cytocompatibility test using the MDA-MB-231 cell line showed 90 to 100% viability for all polyurethanes, surpassing the minimum 70% threshold needed for biomaterials deemed cytocompatibility. Despite the non-cytotoxic nature of the polyurethane extracts when grown directly on the surface, they displayed poor fibroblast adhesion, except for SPUUK. All vascular grafts showed hemolysis values under the permissible limit of 5% and longer coagulation times.

A Novel In Situ Sol-Gel Synthesis Method for PDMS Composites Reinforced with Silica Nanoparticles.

The addition of nanostructures to polymeric materials allows for a direct interaction between polymeric chains and nanometric structures, resulting in a synergistic process through the physical (electrostatic forces) and chemical properties (bond formation) of constituents for the modification of their properties and potential cutting-edge materials. This study explores a novel in situ synthesis method for PDMS-%SiO2 nanoparticle composites with varying crosslinking degrees (PDMS:TEOS of 15:1, 10:1, and 5:1); particle concentrations (5%, 10%, and 15%); and sol-gel catalysts (acidic and alkaline). This investigation delves into the distinct physical and chemical properties of silicon nanoparticles synthesized under acidic (SiO2-a) and alkaline (SiO2-b) conditions. A characterization through Raman, FT-IR, and XPS analyses confirms particle size and agglomeration differences between both the SiO2-a and SiO2-b particles. Similar chemical environments, with TEOS and ethanol by-products, were detected for both systems. The results on polymer composites elucidate the successful incorporation of SiO2 nanoparticles into the PDMS matrix without altering the PDMS's chemical structure. However, the presence of nanoparticles did affect the relative intensities of specific vibrational modes over composites from -35% to 24% (Raman) and from -14% to 59% (FT-IR). The XPS results validate the presence of Si, O, and C in all composites, with significant variations in atomic proportions (C/Si and O/Si) and Si and C component analyses through deconvolution techniques. This study demonstrates the successful in situ synthesis of PDMS-SiO2 composites with tunable properties by controlling the sol-gel and crosslinking synthesis parameters. The findings provide valuable insights into the in situ synthesis methods of polymeric composite materials and their potential integration with polymer nanocomposite processing techniques.

Macrophages morphology and cytokine reeducation by ex situ copper thiol complexes.

OBJECTIVE: To study the reeducation effect of copper thiol complexes on macrophage morphology and cytokine expression. METHODS: The effect of copper thiol complexes was assessed on murine macrophages by the cell morphology observed through optical microscopy, while the expression of cytokines by protein abundance after stimulation. A viability experiment was performed on PMBC to confirm that copper complexes do not affect other cells. RESULTS: The M1 shape was reported after treatment with copper thiol complexes at 1-200 µM, while M2 behavior was documented between 50 and 800 µM. Surprisingly, a thin elongate morphology was observed between 400-800 µM like the M2 shape. The expression of M1 cytokines was noted ranging from 1 to 100 µM, with the highest yield at 1 µM (2243 pg/µL) for the copper-penicillamine complex. M2 production behavior was observed at 1-800 µM, with the highest abundance close to 1150 pg/µL (200-400 µM) was quantified from the copper-cysteine complex. Finally, LCCu complexes did not induce a cytotoxic response on PBMC while exhibiting a high IL-4 and IL-10 production, similar to their gold analogs. CONCLUSIONS: The capacity of copper thiol complexes to reeducate M1 to M2 morphoexpression can be promising for cell protection by using copper thiol penicillamine or immuno-regeneration of tissues when using copper thiol cysteine.

Mechanical Properties of Poly(Alkenoate) Cement Modified with Propolis as an Antiseptic.

BACKGROUND: We assessed the effect of propolis on the antibacterial, mechanical, and adhesive properties of a commercial poly(alkenoate) cement. METHODS: The cement was modified with various concentrations of propolis, and antibacterial assays were performed against S. mutans by both MTT assays and agar diffusion tests. The compressive, flexural, and adhesive properties were also evaluated. RESULTS: the modified cement showed activity against S. mutans in both assays, although reductions in compressive (from 211.21 to 59.3 MPa) and flexural strength (from 11.1 to 6.2 MPa) were noted with the addition of propolis, while adhesive strength (shear bond strength and a novel pull-out method) showed a statistical difference (p < 0.05). CONCLUSION: the antiseptic potential of modified material against S. mutans will allow this material to be used in cases in which low mechanical resistance is required (in addition to its anti-inflammatory properties) when using atraumatic restorative techniques, especially in deep cavities.

Novel copper complexes-polyurethane composites that mimics anti-inflammatory response.

Copper is a trace element of biological significance that can form complexes with several thiol containing compounds which can be used as filler in biomedical polyurethanes. In this work, segmented polyurethanes (SPUs) were synthesized with thiol containing compounds as chain extenders including d-penicillamine (DP), l-penicillamine (LP), l-cysteine (LC) and reduced glutathione (GR). Then, the synthesized polyurethane was filled with copper chelates based on the same chain extenders. Evidence of free thiol containing chain extender in polyurethane was not observed by FTIR and Raman but EDX provided evidence of sulfur in the unfilled polyurethane and copper and sulfur in their composite. DSC and DRX showed the semi-crystalline nature of the polyurethanes which provided good mechanical properties, especially to those prepared with DP. The Tg of the PCL determined by DMA shifted toward higher temperatures by the addition of copper complexes while TGA studies showed that the thermal degradation was slightly improved when LCCu and GRCu complex were added. Macrophage viability was observed in all composition studied after longer times of extraction (72 h) and dilutions (1:2 to 1:32) but remarkably high in those prepared with LCCu and GRCu. The anti-inflammatory response was proved in LC and GR copper complex filled polyurethanes as IL-4 and IL-10 increased with time while IL-1ß and TNF-α were reduced.

Effects of Neutralization on the Physicochemical, Mechanical, and Biological Properties of Ammonium-Hydroxide-Crosslinked Chitosan Scaffolds.

It has been reported that chitosan scaffolds, due to their physicochemical properties, stimulate cell proliferation in different tissues of the human body. This study aimed to determine the physicochemical, mechanical, and biological properties of chitosan scaffolds crosslinked with ammonium hydroxide, with different pH values, to better understand cell behavior depending on the pH of the biomaterial. Scaffolds were either neutralized with sodium hydroxide solution, washed with distilled water until reaching a neutral pH, or kept at alkaline pH. Physicochemical characterization included scanning electron microscopy (SEM), elemental composition (EDX), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), and mechanical testing. In vitro cytotoxicity was assessed via dental-pulp stem cells' (DPSCs') biocompatibility. The results revealed that the neutralized scaffolds exhibited better cell proliferation and morphology. It was concluded that the chitosan scaffolds' high pH (due to residual ammonium hydroxide) decreases DPSCs' cell viability.

Zinc Oxide and Copper Chitosan Composite Films with Antimicrobial Activity.

The role of the oral microbiome and its effect on dental diseases is gaining interest. Therefore, it has been sought to decrease the bacterial load to fight oral cavity diseases. In this study, composite materials based on chitosan, chitosan crosslinked with glutaraldehyde, chitosan with zinc oxide particles, and chitosan with copper nanoparticles were prepared in the form of thin films, to evaluate a new alternative with a more significant impact on the oral cavity bacteria. The chemical structures and physical properties of the films were characterized using by Fourier transform infrared spectroscopy (FTIR,) Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis (EDX), thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurements. Subsequently, the antimicrobial activity of each material was evaluated by agar diffusion tests. No differences were found in the hydrophilicity of the films with the incorporation of ZnO or copper particles. Antimicrobial activity was found against S. aureus in the chitosan film crosslinked with glutaraldehyde, but not in the other compositions. In contrast antimicrobial activity against S. typhimurium was found in all films. Based on the data of present investigation, chitosan composite films could be an option for the control of microorganisms with potential applications in various fields, such as medical and food industry.

Antibacterial activity of a glass ionomer cement doped with copper nanoparticles.

Copper nanoparticles (NCu) were synthetized and added to commercial glass ionomer cement, to evaluate in vitro its antibacterial activity against oral cavity strains. The NCu were synthesized by copper acetate reduction with L-ascorbic acid and characterized by FTIR, Raman, XPS, XRD and TEM. Then, commercial glass ionomer cement (GIC) was modified (MGIC) with various concentrations of NCu and physicochemically characterized. Cell viability was tested against human dental pulp fibroblasts (HDPFs) by Alamar-Blue assay and antibacterial test was performed against S. mutans and S. sanguinis by colony forming unit (CFU) growth method. Synthesized NCu rendered a mixture of both metallic copper and cuprous oxide (Cu2O). HDPF viability reduces with exposure time to the extracts (68-72% viability) and MGIC with 2-4 wt% NCu showed antimicrobial activity against the two tested strains.

The Effect of PEGDE Concentration and Temperature on Physicochemical and Biological Properties of Chitosan.

Chitosan (CHT) is a polysaccharide with multiple claimed properties and outstanding biocompatibility, generally attributed to the presence of protonable amino groups rendering a cationic natural polymer. However, the effect of changes in CHT structure due to hydration is not considered in its performance. This study compares the effects on biocompatibility after drying at 25 °C and 150 °C scaffolds of chitosan, polyethylene glycol diglycidyl ether (PEGDE) crosslinked CHT (low, medium and high concentration) and glutaraldehyde (GA) crosslinked CHT. PEGDE crosslinked CHT showed a reduction in free amino groups and the amide I/II ratio, which exhaustive drying reduced further. In X-ray diffraction (DRX) analysis, PEGDE crosslinked CHT showed multiple peaks, whereas the crystallinity percentage was reduced with an increase in PEGDE concentration and thermal treatments at 150 °C. In a direct contact cell assay, high osteoblast viability was achieved at low and medium PEDGE concentrations, which was improved when the crosslinked scaffolds were thermally treated at 150 °C. This was attributed to its partial hydrophilicity, low crystallinity and low surface roughness; this in spite of the small reduction in the amount of free amino groups on the surface induced during drying at 150 °C. Furthermore, PEGDE crosslinked CHT scaffolds showed strong vinculin and integrin 1ß expression, which render them suitable for bone contact applications.

Titanium - castor oil based polyurethane composite foams for bone tissue engineering.

Polyurethanes (PU) foams with titanium particles (Ti) were prepared with castor oil (CO) and isophorone diisocyanate (IPDI) as polymeric matrix, and 1, 3 and 5 wt.% of Ti. Composites were physicochemically and mechanically characterized and their biocompatibility assessed using human dental pulp stem cells (HDPSC). PU synthesis was confirmed by FTIR, but the presence of Ti was detected by RAMAN, X-ray diffraction (peak at 2θ = 40.2°) and by EDX-mapping. Materials showed three decomposition temperatures between 300 °C and 500 °C and their decomposition were not catalyzed by Ti particles. Compressive modulus (164-846 kPa), compressive strength (12.9-116.7 kPa) and density (128-240 kg/m3) tend to increase with Ti concentration but porosity was reduced (87% to 80%). Composites' foams were fully degraded in acid and oxidative media while remained stable in distilled water. HDPSC viability on all composites was higher than 80% up to 14 days while proliferation dropped up to 60% at 21 days. Overall, these results suggest that these foams can be used as scaffolds for bone tissue regeneration.

Effect of the rigid segment content on the properties of segmented polyurethanes conjugated with atorvastatin as chain extender.

Segmented polyurethanes were prepared with polycaprolactone diol as soft segment and various amounts of 4,4´-Methylenebis(cyclohexyl isocyanate) and atorvastatin, a statin used for lowering cholesterol, in order to obtain SPU with different content of rigid segments. Polyurethanes with 35% or 50% of rigid segment content were physicochemically characterized and their biocompatibility assessed with L929 fibroblasts. High concentrations of atorvastatin were incorporated by increasing the content of rigid segments as shown by FTIR, Raman, NMR, XPS and EDX. Thermal and mechanical characterization showed that polyurethanes containing atorvastatin and 35% of rigid segments were low modulus (13 MPa) semicrystalline polymers as they exhibited a glass transition temperature (Tg) at -38 °C, melting temperature (Tm) at 46 °C and crystallinity close to 35.9% as determined by DSC. In agreement with this, X-ray diffraction showed reflections at 21.3° and 23.6° for PCL without reflections for atorvastatin suggesting its presence in amorphous form with higher potential bioavailability. Low content of rigid segments led to highly degradable polymer in acidic, alkaline and oxidative media with an acceptable fibroblast cytotoxicity up to 7 days possibly due to low atorvastatin content.

Preparation and characterization of titanium-segmented polyurethane composites for bone tissue engineering.

Segmented polyurethanes were prepared with polycaprolactone diol as soft segment and 4,4-methylene-bis cyclohexyl diisocyanate and l-glutamine as the rigid segment. These polyurethanes were filled with 1 wt.% to 5 wt.% titanium particles (Ti), physicochemically characterized and their biocompatibility assessed using human dental pulp stem cells and mice osteoblasts. Physicochemical characterization showed that composites retained the properties of the semicrystalline polyurethane as they exhibited a glass transition temperature (Tg) between -35°C and -45°C, melting temperature (Tm) at 52°C and crystallinity close to 40% as determined by differential scanning calorimetry. In agreement with this, X-ray diffraction showed reflections at 21.3° and 23.6° for polycaprolactone diol and reflections at 35.1°, 38.4°, and 40.2° for Ti particles suggesting that these particles are not acting as nucleating sites. The addition of up to 5 wt.% of Ti reduced both, tensile strength and maximum strain from 1.9 MPa to 1.2 MPa, and from 670% to 172% for pristine and filled polyurethane, respectively. Although there were differences between composites at low strain rates, no significant differences in mechanical behavior were observed at higher strain rate where a tensile stress of 8.5 MPa and strain of 223% were observed for 5 wt.% composites. The addition to titanium particles had a beneficial effect on both human dental pulp stem cells and osteoblasts viability, as it increased with the amount of titanium in composites up to 10 days of incubation.

Preparation and bioactive properties of nano bioactive glass and segmented polyurethane composites.

Composites of glutamine-based segmented polyurethanes with 5 to 25 wt.% bioactive glass nanoparticles were prepared, characterized, and their mineralization potential was evaluated in simulated body fluid. Biocompatibility with dental pulp stem cells was assessed by MTS to an extended range of compositions (1 to 25 wt.% of bioactive glass nanoparticles). Physicochemical characterization showed that composites retained many of the matrix properties, i.e. those corresponding to semicrystalline elastomeric polymers as they exhibited a glass transition temperature (Tg) between -41 and -36℃ and a melting temperature (Tm) between 46 and 49℃ in agreement with X-ray reflections at 23.6° and 21.3°. However, with bioactive glass nanoparticles addition, tensile strength and strain were reduced from 22.2 to 12.2 MPa and 667.2 to 457.8%, respectively with 25 wt.% of bioactive glass nanoparticles. Although Fourier transform infrared spectroscopy did not show evidence of mineralization after conditioning of these composites in simulated body fluid, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray microanalysis showed the formation of an apatite layer on the surface which increased with higher bioactive glass concentrations and longer conditioning time. Dental pulp stem cells proliferation at day 5 was improved in bioactive glass nanoparticles composites containing lower amounts of the filler (1-2.5 wt.%) but it was compromised at day 9 in composites containing high contents of nBG (5, 15, 25 wt.%). However, Runx2 gene expression was particularly upregulated for the dental pulp stem cells cultured with composites loaded with 15 and 25 wt.% of bioactive glass nanoparticles. In conclusion, low content bioactive glass nanoparticles and segmented polyurethanes composites deserve further investigation for applications such as guided bone regeneration membranes, where osteoconductivity is desirable but not a demanding mechanical performance.

Human mesenchymal stem cell behavior on segmented polyurethanes prepared with biologically active chain extenders.

The development of elastomeric, bioresorbable and biocompatible segmented polyurethanes (SPUs) for use in tissue-engineering applications has attracted considerable interest because of the existing need of mechanically tunable scaffolds for regeneration of different tissues, but the incorporation of osteoinductive molecules into SPUs has been limited. In this study, SPUs were synthesized from poly (ε-caprolactone)diol, 4,4'-methylene bis(cyclohexyl isocyanate) using biologically active compounds such as ascorbic acid, L-glutamine, ß-glycerol phosphate, and dexamethasone as chain extenders. Fourier transform infrared spectroscopy (FTIR) revealed the formation of both urethanes and urea linkages while differential scanning calorimetry, dynamic mechanical analysis, X-ray diffraction and mechanical testing showed that these polyurethanes were semi-crystalline polymers exhibiting high deformations. Cytocompatibility studies showed that only SPUs containing ß-glycerol phosphate supported human mesenchymal stem cell adhesion, growth, and osteogenic differentiation, rendering them potentially suitable for bone tissue regeneration, whereas other SPUs failed to support either cell growth or osteogenic differentiation, or both. This study demonstrates that modification of SPUs with osteogenic compounds can lead to new cytocompatible polymers for regenerative medicine applications.

Physicochemical, mechanical, and biological properties of bone cements prepared with functionalized methacrylates.

Bone cements prepared with methyl methacrylate (MMA) as a base monomer and either methacrylic acid (MAA) or diethyl amino ethyl methacrylate (DEAEMA) as comonomers were characterized in terms of curing behavior, mechanical properties, and their in vitro biocompatibility. The curing time and setting temperature were found to be composition dependent while the residual monomer was not greatly affected by the presence of either acidic or alkaline comonomers in the bone cements. For samples with MAA comonomer, a faster curing time and higher setting temperature were observed when compared to the cement with DEAEMA comonomer. In terms of mechanical properties, the highest compressive strength was exhibited by formulations containing MAA, while the highest impact strength was shown by the formulations prepared with DEAEMA. There were no differences observed between the two formulations for tensile, shear, and bending strength values. Similarly, fatigue crack propagation studies did not reveal differences with the addition of either DEAEMA or MAA.No differences were observed in the initial number of attached primary rat femur osteoblasts on the different bone cements and positive controls. However, after 48 h there was a reduced proliferation in the cells grown on bone cements containing MAA.