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Extracellular matrix (ECM)-like coating was developed on biodegradable biomaterials based on the electrostatic self-assembly (ESA) technique to promote osteoblast growth. Poly(ethylenimine) (PEI) was first employed to obtain a stable positively charged surface on poly(DL-lactide) (PDL-LA) substrate. Gelatin was selected as ECM-like biomacromolecule to deposit on the activated PDL-LA substrate using the ESA technique. ζ-Potential results showed alternating charge of polyelectrolytes (PEI/gelatin) layering on PDL-LA microspheres. Quartz crystal microbalance (QCM) measurement further verified the gradual deposition of PEI/gelatin on PDL-LA thin film. Osteoblast cells (MC3T3) were chosen to test the cell behavior on modified PDL-LA substrates. The osteoblast test about cell activity, intracellular total DNA content, total protein content and cell morphology by SEM investigation on ECM-like multilayer-modified PDL-LA substrate showed to promote osteoblast growth. Comparing conventional coating methods, polyelectrolyte multilayers are easy and stable to prepare. It may be a good choice for the surface modification of complex biomedical devices. These very flexible systems allow broad medical applications for drug delivery and tissue engineering. [ABSTRACT FROM AUTHOR]

To develop biodegradable polymers with favorable physicochemical and biological properties, we have synthesized a series of poly(terephthalate-co-phosphate)s using a two-step polycondensation. The diol 1,4-bis(2-hydroxyethyl) terephthalate was first reacted with ethylphosphorodichloridate (EOP), and then chain-extended with terephthaloyl chloride (TC). Incorporation of phosphate into the poly(ethylene terephthalate) backbone rendered the co-polymers soluble in chloroform and biodegradable, lowered the Tg, decreased the crystallinity and increased the hydrophilicity. With an EOP/TC molar feed ratio of 80 : 20, the polymer exhibited good film-forming property, yielding at 86.6 ± 1.6% elongation with an elastic modulus of 13.76 ± 2.66 MPa. This polymer showed a favorable toxicity profile in vitro and good tissue biocompatibility in the muscular tissue of mice. In vitro the polymer lost 21% of mass in 21 days, but only 20% for up to 4 months in vivo. It showed no deterioration of properties after sterilization by γ-irradiation at 2.5 Mrad on solid CO2. Release of FITC-BSA from the microspheres was diffusion-controlled and exceeded 80% completion in two days. Release of the hydrophobic cyclosporine-A from microspheres was however much more sustained and near zero-ordered, discharging 60% in 70 days. A limited structure–property relationship has been established for this co-polymer series. The co-polymers became more hydrolytically labile as the phosphate component (EOP) was increased and the side chains were switched from the ethoxy to the methoxy structure. Converting the methoxy group to a sodium salt further increased the degradation rate significantly. The chain rigidity as reflected in the Tg values of the co-polymers decreased according to the following diol structure in the backbone: ethylene glycol > 2-methylpropylene diol > 2,2-dimethylpropylene diol. The wide range of physicochemical properties obtainable from this copolymer series should help the design of degradable biomaterials for specific biomedical applications. [ABSTRACT FROM AUTHOR]

This work evaluates the structural changes of an interpenetrated starch thermoplastic blend withstanding different enzymatic α-amylase degradation periods (up to 200 days), and establishes the relationships between the kinetics degradation rate and the structure of the material. It characterises the different stages of the enzymatic degradation process on starch/ethylenevinyl-alcohol blends, based on the attack of the connected starch domains that can be accessed by the enzymatic solution. The completely encapsulated starch particles remain practically unchanged. Furthermore, it was also found that the enzymatic degradation process was limited after 100 days of immersion. In order to understand such phenomenon several techniques were used, namely differential scanning calorimetry, contact-angle measurements, high-performance liquid chromatography, Fourier transform infrared spectrometry, scanning electron microscopy and atomic force microscopy. The materials were evaluated with respect to the enzymatic degradation rate, surface morphology and degradation behaviour. The results show that the ethylene-vinylalcohol phase wraps the starch domains, preventing the respective degradation. Consequently, the degraded material in the solution comes only from the starch particles that could be reached by the enzyme. [ABSTRACT FROM AUTHOR]

We previously demonstrated that cylindrical, biodegradable reservoirs fabricated with polylactide-polyethylene glycol (PLLA : PEG) films maintain constant permeability and enable zeroorder drug delivery for up to 6 weeks in vitro. This research proposes that PEG not only enhances permeability but also extends of life of the device by allowing the escape of soluble degraded monomers thereby minimizing autocatalysis of PLLA. To test this hypothesis, cylindrical PLLA films with varying PEG concentrations (0–30%, w/w) and film-thickness (0.05–0.18 mm) were fabricated, and their degradation rate and thermal properties monitored for 23 weeks in vitro. The decrease in PLLA molecular weight for all films followed bi-exponential kinetics that fit the equation:yt = M(e–K1t + e– K2t), as was determined by a Pearson's coefficient > 0.95 for all films. The constant M was empirically determined to be equal to have the initial molecular weight of the degrading polymer. The value of K1 was 5–60 orders of magnitude greater than K2 and was attributed to the autocatalytic degradation based on its dependence on PEG concentration, film thickness, and correlation with the enthalpy change associated with the glass transition (ΔCp). K2 was attributed to simple hydrolytic cleavage of PLLA. The decrease in the value of K1 with PEG concentration and thickness, and the correlation of K1 with ΔCp, confirmed that the PLLA degradation can be controlled by incorporating PEG, as well as by modifying thickness. [ABSTRACT FROM AUTHOR]

—Poly( D , L-lactide-co-glycolide) (PLGA), a biodegradable synthetic polymer, is widely used in a variety of tissue-engineered applications, including drug-delivery systems. However, the PLGA scaffolds, macroporous and three-dimensional structure, are difficult to cell attachment and in-growth due to surface hydrophobicity. In order to introduce in new bioactive functionality from porcine small intestine submucosa (SIS) as natural source for PLGA, we fabricated SIS-powder-impregnated PLGA (SIS/PLGA) hybrid scaffolds. Fabrication parameters, including ratios of SIS, PLGA and salt, were optimized to produce the desired macroporous foam. The scaffolds had a relatively homogeneous pore structure, good interconnected pores from the surface to core region and showed an average pore size in the range 69.23–105.82 μm and over 90% porosity. The SIS/PLGA scaffolds degraded with a rate depending on the contents of the SIS. After the fabrication of the SIS/PLGA hybrid scaffolds the wettability of the scaffold was greatly enhanced, resulting in uniform cell seeding and distribution. So, it was observed that BMSC attachment to the SIS/PLGA scaffolds increased gradually with increasing SIS contents. Scaffolds of PLGA alone and SIS/PLGA were implanted subcutaneously under dorsal skin of athymic nude mouse to observe the osteoconductivity. It was found from the result that the effects of the SIS/PLGA scaffolds on bone formation are stronger than control PLGA scaffolds. In summary, the SIS/PLGA scaffolds have osteoconductive effects to allow remodeling and replacement by osseous tissue. [ABSTRACT FROM AUTHOR]

In tissue engineering, excellent biodegradable materials are desired as temporary scaffolds to support cell growth and disappear with the progress of tissue regeneration. We previously synthesized biodegradable poly(depsipeptide-co-lactide), poly[(Glc-Asp)-co-LA] and poly[(Glc-Lys)-coLA], having reactive side-chain groups. Then, the effects of reactive and ionic side-chain groups on cell attachment and growth were investigated using co-polymer films with various amounts of carboxyl or amino groups. In this study, to evaluate the utility of these co-polymers as functional scaffolds for tissue regeneration, 3-dimensional porous sponges were prepared by freeze-drying method and the effects of reactive and ionic side-chain groups on cell growth and degradation behavior were investigated using co-polymer sponges with various amounts of carboxyl or amino groups. Good cell growth was observed on the co-polymer sponges. During cell culture, the co-polymer sponges exhibited various degradation rates related to the depsipeptide unit content. Three-dimensional biodegradable polymer matrices with reactive surface, controllable degradation behavior and good cell growth were successfully prepared using these co-polymers. Such kinds of co-polymer matrices are good candidate for scaffold for tissue engineering. [ABSTRACT FROM AUTHOR]

Degradable terpolymers were synthesized by bulk copolymerization of 2,2-dimethyl trimethyle necarbonate (DTC), ε-caprolactone (CL) and poly(ethylene glycol) (PEG) using stannous octoate as catalyst at 140°C for 36 h. The molar ratio in feed of DTC to CL was fixed at 20 : 80. The molecular weight and the mol% of PEG were varied in order to obtain copolymers with different properties. The copolymers were characterized by [sup 1]H-NMR, [sup 13]C-NMR, FT-IR, GPC and DSC. It was found that the hydrophilicity of these materials increased with increasing PEG content in the copolymers, according to the measurements of static contact angles of distilled water on the surface of polymer films. Mechanical tests and hydrolytic degradation assays showed that copolymers of different degradability and mechanical properties could be tailored by adjusting the compositions. For the copolymer T-4 (11.9 mol% of PEG with M[sub n] 2000), the tensile strength and the elastic modulus could reach 6.2 MPa and 25 MPa, respectively. It took only 4 weeks for the copolymer T-4 to degrade to 83% (M[sub n,t]/M[sub n,0]) and 10 weeks to 63% in 0.1 M PBS at pH 7.4 and 37°C. There was no obvious acceleration of degradation rate in vivo in comparison with that in vitro. These materials might be useful for nerve regeneration guides and other biomedical applications. [ABSTRACT FROM AUTHOR]

Di-block co-polymers of poly([sub L]-alanine) with poly(ethylene glycol) monomethyl ether (MPEG) were synthesized as amphiphilic biodegradable co-polymers. The ring-opening polymerization of N-carboxy-L-alanine anhydride (NCA) in dichloromethane was initiated by amino-terminated poly(ethylene glycol) monomethyl ether (MPEG-NH[sub 2], M[sub n] = 2000) to afford poly(L-alanine)-block-MPEG. The weight ratio of two blocks in the co-polymers could be altered by adjusting the feeding ratio of NCA to MPEG-NH[sub 2]. Their chemical structures were characterized on the basis of infrared spectrometry and nuclear magnetic resonance. According to circular dichroism measurement, the poly(L-alanine) chain on the co-polymers in an aqueous medium had a α-helix conformation. Two melting points from MPEG block and poly(L-alanine), respectively, could be observed in differential scanning calorimetry curves of the co-polymers, suggesting that a micro-domain phase separation appeared in their bulky states. The co-polymers could take up some water and the capacity was dependent on the ratio of poly(L-alanine) block to MPEG. Such co-polymers might be useful in drug-delivery systems and other biomedical applications. [ABSTRACT FROM AUTHOR]

Poly(D,L-lactide) (PDLLA) was synthesized by ring-opening polymerization of D,Llactide. Non-woven PDLLA matrices were prepared by an extrusion/winding process. The process conditions were optimized and the surfaces of these matrices were modified by glow-discharge treatment and/or glutaraldehyde incorporation for immobilization of elastin-derived proteins (ESP) to the matrix to increase the biocompatibility and also to improve the bioactivity of the matrix. Glow-discharge conditions were optimized. Ethylene diamine (EDA) and Ar were used as the active monomers in the plasma phase. When EDA was used, the glow-discharge treated PDLLA matrices were first allowed to be reacted with glutaraldehyde, although, when Ar used, the treated matrices were used directly for ESP immobilization. The higher degree of immobilization was obtained for EDA and glutaraldehyde. The ESP-incorporated PDLLA matrices were further treated with elastin by cross-reaction of the ESP molecules on the matrix surfaces with elastin. Scanning electron microscopy (SEM) studies showed that ESP were homogeneously deposited the surface of the matrix. [ABSTRACT FROM AUTHOR]

Deals with a study which examined the effect of acetylation of biodegradable polyrotaxanes on its supramolecular dissociation via terminal ester hydrolysis. Background to the study; Materials and methods; Results and discussion.