Novel bioactive glass (BG) nanoparticles/poly(L-lactide) (PLLA) composites were prepared as promising bone-repairing materials. The BG nanoparticles (Si:P:Ca=29:13:58 weight ratio) of about 40nm diameter were prepared via the sol-gel method. In order to improve the phase compatibility between the polymer and the inorganic phase, PLLA (M(n)=9700Da) was linked to the surface of the BG particles by diisocyanate. The grafting ratio of PLLA was in the vicinity of 20 wt.%. The grafting modification could improve the tensile strength, tensile modulus and impact energy of the composites by increasing the phase compatibility. When the filler loading reached around 4 wt.%, the tensile strength of the composite increased from 56.7 to 69.2MPa for the pure PLLA, and the impact strength energy increased from 15.8 to 18.0 kJ m(-2). The morphology of the tensile fracture surface of the composite showed surface-grafted bioactive glass particles (g-BG) to be dispersed homogeneously in the PLLA matrix. An in vitro bioactivity test showed that, compared to pure PLLA scaffold, the BG/PLLA nanocomposite demonstrated a greater capability to induce the formation of an apatite layer on the scaffold surface. The results of marrow stromal cell culture revealed that the composites containing either BG or g-BG particles have much better biocompatibility compared to pure PLLA material.
"This may result in an ultimate depreciation of the mechanical properties  . To avoid this and also a possible phase segregation , polymer/inorganic nanofiller compatibility is often improved by modifying the surface with organic molecules or surfactants  . Despite this, the synergy between the two phases is still often inappropriate for the targeted application because of the heterogeneous degradation of the phases, the rapid loss of the composite mechanical properties, or the inappropriate release rate of ions/monomers from the material  . "
[Show abstract][Hide abstract] ABSTRACT: The introduction of hybrid materials in regenerative medicine has solved some problems related to the mechanical and bioactive properties of biomaterials. Calcium phosphates and their derivatives have provided the basis for inorganic components, thanks to their good bioactivity, especially in bone regeneration. When mixed with biodegradable polymers, the result is a synergic association that mimics the composition of many tissues of the human body and, additionally, exhibits suitable mechanical properties. Together with the development of nanotechnology and new synthesis methods, hybrids offer a promising option for the development of a third or fourth generation of smart biomaterials and scaffolds to guide the regeneration of natural tissues, with an optimum efficiency/cost ratio. Their potential bioactivity, as well as other valuable features of hybrids, open promising new pathways for their use in bone regeneration and other tissue repair therapies. This review provides a comprehensive overview of the different hybrid organic-inorganic scaffolding biomaterials developed so far for regenerative therapies, especially in bone. It also looks at the potential for research into hybrid materials for other, softer tissues, which is still at an initial stage, but with very promising results.
Current Organic Chemistry 10/2014; 18(18):2299-2314. DOI:10.2174/1385272819666140806200355 · 2.16 Impact Factor
"The attachment of organic molecules to the surface of bioglass particles has been previously proposed to improve the interphase adhesion between inorganic particles and polymer matrix  but has never been applied to avoid the degradation reaction between the SieO À groups present in the surface of bioglass particles and the C]O groups present in the polymer's backbone. Several methods have been reported in the current literature for the surface modification of inorganic bioactive particles   . However, all these surface modification methods require multiple steps of long duration and high quantities of organic solvents that can be harmful for health, limiting the application of these products in the biomedical field. "
[Show abstract][Hide abstract] ABSTRACT: Poly(L-lactide) (PLLA), poly(epsilon-caprolactone) (PCL) and poly(L-lactide/epsilon-caprolactone) (PLCL) are medical (co)polyesters that are conventionally manufactured by thermoplastic processing techniques, such as injection molding or extrusion. However, the addition of bioglass particles causes a degradation reaction of the matrix at high temperatures and could limit the fabrication of composite systems by the above mentioned processes. In this work, a surface modification of bioactive glass particles by plasma polymerization of acrlylic acid is proposed as a strategy for the improvement of thermal stability of bioglass filled composite systems. The developed poly(acrylic acid) layer on the surface of bioglass particles, hinders the degradation reaction between the Si-O- groups present in the surface of the particles and the C=O groups of the polymer's backbone. As an illustration, the onset degradation temperature (T-onset) of PLLA, PCL and PLCL increased respectively from 185.0, 240.1 and 192.2 for bioglass (BG) filled composites to 240.4, 299.5 and 245.7 degrees C for their modified bioglass (mBG) filled counterparts. Finally, neat PLLA and composites having 15 vol.% of BG and mBG were melt-compounded and subsequently hot pressed to obtain tensile test samples. Non-modified bioglass filled PLLA film was too brittle and difficult to handle due to the sharp reduction of molecular weight during thermoplastic processing. On the contrary, modified bioglass filled PLLA presented a slight increase in Young's modulus with respect to unfilled PLLA but a decrease in both tensile strength and elongation at break.
"Hexamethylene diisocyanate (HDI) has been reported as being acutely cytotoxic and an irritant to the skin and eyes. However, despite these reported toxicology issues there is also evidence for the effective use of HDI as a cross-linker in artiﬁcial extracellular matrix protein production genetically engineered from elastin and ﬁbronectin derived repeat units , a modifier in drug delivery systems a surface-modifier/coupler in biocomposites  and as a surface modifier of calcium phosphate ceramics [30,31,32,33] investigated for use as medical implants. "
[Show abstract][Hide abstract] ABSTRACT: In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent's within medical implant devices.
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