Synthesis, physicochemical, rheological and in-vitro characterization of double-crosslinked hyaluronic acid hydrogels containing dexamethasone and PLGA/dexamethasone nanoparticles as hybrid systems for specific medical applications.

Injectable hydrogels and biodegradable nanoparticles are using in tissue engineering applications and drug delivery systems. To improve physiochemical properties of biomaterials and to develop their applications, hybrid systems consist of hydrogels, and biodegradable nanoparticles were synthesized. In this study, hybrid systems based on double crosslinked hyaluronic acid and PLGA/Dexamethasone sodium phosphate (PLGADEX) nanoparticles are designed and synthesized in several steps. At the first step, poly(l-lactide-co-glycolide) (PLGA) in a ratio of LLA:GA = 85:15 mol% was synthesized via ring-opening polymerization. Then, PLGADEX nanoparticles were synthesized in different ratios using the partially modified emulsification-diffusion method and fully characterized, and desirable nanoparticle was selected (PLGADEX20). At the second step, a double cross-linked hyaluronic acid (XHA) was prepared by mixing various ratios of amino-hyaluronic acid and aldehyde-hyaluronic acid in the presence of genipin. Finally, by mixing of various ratios of PLGADEX20 and Dexamethasone sodium phosphate (DEX) with different ratios of XHA, hybrid systems were prepared. Based on the characterization of hybrid samples and the release studies, hydrogels containing nanoparticles showed a controlled drug release, while the best sample with 3% of optimized nanoparticle was chosen. According to physiochemical and biological properties, these hybrid systems can be good candidates for anti-adhesion barriers, wound dressings, and novel drug delivery systems.

Investigating composite systems based on poly L-lactide and poly L-lactide/triclosan nanoparticles for tissue engineering and medical applications.

In this study, the encapsulated triclosan with a low molecular weight PLLA (LATC30) is dispersed into a PLLA having higher molecular weight via melt blending to increase the overall properties and particularly antibacterial activity of the system. The proposed method results in a completely homogenous composite as 5% LATC30 improved mechanical properties. For instance, the elongation at break was increased ca. 3%. The mechanical properties of the fabricated composites were also affected by the plasticizing role of LATC30. The kinetics of hydrolytic degradation in an accelerated condition was obtained using a novel method by the Beer-Lambert equation. It was found that the incorporation of LATC30 into the composite increases the rate of hydrolytic degradation. The calorimetry showed a reduction in crystallinity upon addition of LATC30. Moreover, the degradation of the composites was studied and fully described the kinetic analysis by the Flynn-Wall-Ozawa (FWO) method. From which, it was found that the activation energy of the system was decreased. As the LATC30 content of the composite was increased, the hydrophilicity of the composite was increased. The fabricated scaffolds with 5% LATC30 demonstrated a good osteoblast cell attachment and mineralization on the composite scaffolds. This composite is a suitable antibacterial candidate for the bone tissue engineering and medical applications since the real dosage of triclosan stays at ca. 1.5%.

Synthesis and characterization of nanocomposite scaffolds based on triblock copolymer of L-lactide, ε-caprolactone and nano-hydroxyapatite for bone tissue engineering.

The employment of biodegradable polymer scaffolds is one of the main approaches for achieving a tissue engineered construct to reproduce bone tissues, which provide a three dimensional template to regenerate desirable tissues for different applications. The main goal of this study is to design a novel triblock scaffold reinforced with nano-hydroxyapatite (nHA) for hard tissue engineering using gas foaming/salt leaching method with minimum solvent usage. With this end in view, the biodegradable triblock copolymers of l-lactide and ε-caprolactone with different mol% were synthesized by ring-opening polymerization method in the presence of Sn(Oct)2 catalyst as initiator and ethylene glycol as co-initiator. The chemical compositions of biodegradable copolymers were characterized by means of FTIR and NMR. The thermal and crystallization behaviors of copolymers were characterized using TGA and DSC thermograms. Moreover, nano-hydroxyapatite was synthesized by the chemical precipitation process and was thoroughly characterized by FTIR, XRD and TEM. Additionally, the nanocomposites with different contents of nHA were prepared by mixing triblock copolymer with nHA. Mechanical properties of the prepared nanocomposites were evaluated by stress-strain measurements. It was found that the nanocomposite with 30% of nHA showed the optimum result. Therefore, nanocomposite scaffolds with 30% nHA were fabricated by gas foaming/salt leaching method and SEM images were used to observe the microstructure and morphology of nanocomposites and nanocomposite scaffolds before and after cell culture. The in-vitro and cell culture tests were also carried out to further evaluate the biological properties. The results revealed that the porous scaffolds were biocompatible to the osteoblast cells because the cells spread and grew well. The resultant nanocomposites could be considered as good candidates for use in bone tissue engineering.