In vitrocomparative biodegradation analysis of salt-leached porous polymer scaffolds

Morphological and biochemical analysis of cells cultured on fibrous poly(ε-caprolactone) scaffolds with different degrees of fiber alignment produced by solution blow spinning

BACKGROUND

Bioresorbable materials are compounds that decompose in physiological mediums both in vitro and in vivo and are used as an alternative to temporary implants in injured tissues. The aim of this study was to analyze the morphology and cytochemistry of cells grown on fibrous poly(ε-caprolactone) (PCL) scaffolds and to measure cell metabolism parameters by biochemical analysis of the conditioned culture medium from cells grown on the scaffolds.

METHODS

Fibrous PCL scaffolds were used under the following conditions: unaligned fibers (NA), fibers aligned at 150 rpm (A150), and fibers aligned at 300 rpm (A300). Vero cells were cultured on these scaffolds for 24 h, 48 h, and 72 h. Samples were analyzed by SEM, MicroCT, cytochemistry, and culture medium biochemistry.

RESULTS

The results of the cytochemical analysis showed cells were confluent and well spread on the culture plate, while cells grown on the polymeric scaffold, exhibited an elongated morphology. In the biochemical analyses, no significant differences were observed in the expression of alkaline phosphatase or in the levels of cholesterol or total protein in the culture medium. The different materials do not seem to promote changes in the expression or metabolism of these molecules. Only glucose was markedly reduced in the culture medium of cells grown on either aligned or unaligned scaffolds for 48 h or 72 h. This finding indicates the intense energy requirements of cells grown on these scaffolds.

CONCLUSION

PCL fibers showed a great capacity to support cell growth. These data reinforce the interpretation that cells grow satisfactorily on PCL scaffolds.

In Vitro Hydrolytic Degradation of Polyester-Based Scaffolds under Static and Dynamic Conditions in a Customized Perfusion Bioreactor

Creating biofunctional artificial scaffolds could potentially meet the demand of patients suffering from bone defects without having to rely on donors or autologous transplantation. Three-dimensional (3D) printing has emerged as a promising tool to fabricate, by computer design, biodegradable polymeric scaffolds with high precision and accuracy, using patient-specific anatomical data. Achieving controlled degradation profiles of 3D printed polymeric scaffolds is an essential feature to consider to match them with the tissue regeneration rate. Thus, achieving a thorough characterization of the biomaterial degradation kinetics in physiological conditions is needed. Here, 50:50 blends made of poly(ε-caprolactone)-Poly(D,L-lactic-co-glycolic acid (PCL-PLGA) were used to fabricate cylindrical scaffolds by 3D printing (⌀ 7 × 2 mm). Their hydrolytic degradation under static and dynamic conditions was characterized and quantified. For this purpose, we designed and in-house fabricated a customized bioreactor. Several techniques were used to characterize the degradation of the parent polymers: X-ray Photoelectron Spectroscopy (XPS), Gel Permeation Chromatography (GPC), Scanning Electron Microscopy (SEM), evaluation of the mechanical properties, weigh loss measurements as well as the monitoring of the degradation media pH. Our results showed that flow perfusion is critical in the degradation process of PCL-PLGA based scaffolds implying an accelerated hydrolysis compared to the ones studied under static conditions, and up to 4 weeks are needed to observe significant degradation in polyester scaffolds of this size and chemical composition. Our degradation study and characterization methodology are relevant for an accurate design and to tailor the physicochemical properties of polyester-based scaffolds for bone tissue engineering.

Polyglycerol Hyperbranched Polyesters: Synthesis, Properties and Pharmaceutical and Biomedical Applications

In a century when environmental pollution is a major issue, polymers issued from bio-based monomers have gained important interest, as they are expected to be environment-friendly, and biocompatible, with non-toxic degradation products. In parallel, hyperbranched polymers have emerged as an easily accessible alternative to dendrimers with numerous potential applications. Glycerol (Gly) is a natural, low-cost, trifunctional monomer, with a production expected to grow significantly, and thus an excellent candidate for the synthesis of hyperbranched polyesters for pharmaceutical and biomedical applications. In the present article, we review the synthesis, properties, and applications of glycerol polyesters of aliphatic dicarboxylic acids (from succinic to sebacic acids) as well as the copolymers of glycerol or hyperbranched polyglycerol with poly(lactic acid) and poly(ε-caprolactone). Emphasis was given to summarize the synthetic procedures (monomer molar ratio, used catalysts, temperatures, etc.,) and their effect on the molecular weight, solubility, and thermal and mechanical properties of the prepared hyperbranched polymers. Their applications in pharmaceutical technology as drug carries and in biomedical applications focusing on regenerative medicine are highlighted.

Bioactive Glass Fiber-Reinforced PGS Matrix Composites for Cartilage Regeneration

Poly(glycerol sebacate) (PGS) is an elastomeric polymer which is attracting increasing interest for biomedical applications, including cartilage regeneration. However, its limited mechanical properties and possible negative effects of its degradation byproducts restrict PGS for in vivo application. In this study, a novel PGS–bioactive glass fiber (F18)-reinforced composite was developed and characterized. PGS-based reinforced scaffolds were fabricated via salt leaching and characterized regarding their mechanical properties, degradation, and bioactivity in contact with simulated body fluid. Results indicated that the incorporation of silicate-based bioactive glass fibers could double the composite tensile strength, tailor the polymer degradability, and improve the scaffold bioactivity.

Electrically conductive nanofibrous scaffolds based on poly(ethylene glycol)s-modified polyaniline and poly(ε-caprolactone) for tissue engineering applications

The objective of this study was to design and development of electrically conductive nanofibrous scaffolds composed of PEGs-b-(PANI)₄ and PCL for tissue engineering applications.

A biomimetic 3D microtubule-orientated poly(lactide-co-glycolide) scaffold with interconnected pores for tissue engineering

An ideal tissue engineering scaffold should imitate physical and biochemical cues of natural extracellular matrix and have interconnected porous structures with high porosity to provide adequate space for cell seeding, growth and proliferation, as well as nutrient delivery and metabolized product elimination. In this study, we examined the feasibility of fabricating microtubule-orientated poly(lactide-co-glycolide) (PLGA) scaffolds with interconnected pores (denoted as MOIP-PLGA) by an improved thermal-induced phase separation technique. We successfully constructed MOIP-PLGA using 1,4-dioxane as the first solvent and benzene or water with lower freezing point as the second solvent. Especially, when water was used, the MOIP-PLGA had higher porosity and it could guide rabbit aortic smooth muscle cells (SMCs) to better grow along the microtubule direction of the scaffold. Comparing with microtubule-orientated scaffold without interconnected pores (denoted as MONIP-PLGA), the proliferation and viability of SMCs cultured on MOIP-PLGA were higher. Moreover, basic fibroblast growth factor could be effectively bound on MOIP-PLGA by a plasma treatment technique and the growth factor could be slowly released in vitro, maintaining bioactivity.

Supercritical CO2 foaming of thermoplastic materials derived from maize: proof-of-concept use in mammalian cell culture applications

BACKGROUND

Foams are high porosity and low density materials. In nature, they are a common architecture. Some of their relevant technological applications include heat and sound insulation, lightweight materials, and tissue engineering scaffolds. Foams derived from natural polymers are particularly attractive for tissue culture due to their biodegradability and bio-compatibility. Here, the foaming potential of an extensive list of materials was assayed, including slabs elaborated from whole flour, the starch component only, or the protein fraction only of maize seeds.

METHODOLOGY/PRINCIPAL FINDINGS

We used supercritical CO2 to produce foams from thermoplasticized maize derived materials. Polyethylene-glycol, sorbitol/glycerol, or urea/formamide were used as plasticizers. We report expansion ratios, porosities, average pore sizes, pore morphologies, and pore size distributions for these materials. High porosity foams were obtained from zein thermoplasticized with polyethylene glycol, and from starch thermoplasticized with urea/formamide. Zein foams had a higher porosity than starch foams (88% and 85%, respectively) and a narrower and more evenly distributed pore size. Starch foams exhibited a wider span of pore sizes and a larger average pore size than zein (208.84 vs. 55.43 μm2, respectively). Proof-of-concept cell culture experiments confirmed that mouse fibroblasts (NIH 3T3) and two different prostate cancer cell lines (22RV1, DU145) attached to and proliferated on zein foams.

CONCLUSIONS/SIGNIFICANCE

We conducted screening and proof-of-concept experiments on the fabrication of foams from cereal-based bioplastics. We propose that a key indicator of foamability is the strain at break of the materials to be foamed (as calculated from stress vs. strain rate curves). Zein foams exhibit attractive properties (average pore size, pore size distribution, and porosity) for cell culture applications; we were able to establish and sustain mammalian cell cultures on zein foams for extended time periods.

Poly(glycerol sebacate)-modified polylactic acid scaffolds with improved hydrophilicity, mechanical strength and bioactivity for bone tissue regeneration

Polylactic acid (PLA) has been extensively researched in biomedical engineering applications due to its superior mechanical strength and biocompatibility in vivo.

In Vitro Examination of Poly(glycerol sebacate) Degradation Kinetics: Effects of Porosity and Cure Temperature

Poly(glycerol sebacate) (PGS) is a biodegradable and biocompatible elastomer that has been used in a wide range of biomedical applications. While a porous format is common for tissue engineering scaffolds, to allow cell ingrowth, PGS degradation has been primarily studied in a nonporous format. The purpose of this research was to investigate the degradation of porous PGS at three frequently used cure temperatures: 120°C, 140°C, and 165°C. The thermal, chemical, mechanical, and morphological changes were examined using thermogravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, compression testing, and scanning electron microscopy. Over the course of the 16-week degradation study, the samples’ pores collapsed. The specimens cured at 120°C demonstrated the most degradation and became gel-like after 16 weeks. Thermal changes were most evident in the 120°C and 140°C cure PGS specimens, as shifts in the melting and recrystallization temperatures occurred. Porous samples cured at all three temperatures displayed a decrease in compressive modulus after 16 weeks. This in vitro study helped to elucidate the effects of porosity and cure temperature on the biodegradation of PGS and will be valuable for the design of future PGS scaffolds.

Gelatin-modified polyurethanes for soft tissue scaffold

Recently, in the field of biomaterials for soft tissue scaffolds, the interest of their modification with natural polymersis growing. Synthetic polymers are often tough, and many of them do not possess fine biocompatibility. On the other hand, natural polymers are biocompatible but weak when used alone. The combination of natural and synthetic polymers gives the suitable properties for tissue engineering requirements. In our study, we modified gelatin synthetic polyurethanes prepared from polyester poly(ethylene-butylene adipate) (PEBA), aliphatic 1,6-hexamethylene diisocyanate (HDI), and two different chain extenders 1,4-butanediol (BDO) or 1-ethoxy-2-(2-hydroxyethoxy)ethanol (EHEE). From a chemical point of view, we replaced expensive components for building PU, such as 2,6-diisocyanato methyl caproate (LDI) and 1,4-diisocyanatobutane (BDI), with cost-effective HDI. The gelatin was added in situ (in the first step of synthesis) to polyurethane to increase biocompatibility and biodegradability of the obtained material. It appeared that the obtained gelatin-modified PU foams, in which chain extender was BDO, had enhanced interactions with media and their hydrolytic degradation profile was also improved for tissue engineering application. Furthermore, the gelatin introduction had positive impact on gelatin-modified PU foams by increasing their hemocompatibility.