Unique combinations of hard and soft components found in biological tissues have inspired researchers to design and develop synthetic nanocomposite gels and hydrogels with elastomeric properties. These elastic materials can potentially be used as synthetic mimics for diverse tissue engineering applications. Here we present a set of elastomeric nanocomposite hydrogels made from poly(ethylene glycol) (PEG) and hydroxyapatite nanoparticles (nHAp). The aqueous nanocomposite PEG-nHAp precursor solutions can be injected and then covalently cross-linked via photopolymerization. The resulting PEG-nHAp hydrogels have interconnected pore sizes ranging from 100 to 300 nm. They have higher extensibilities, fracture stresses, compressive strengths, and toughness when compared with conventional PEO hydrogels. The enhanced mechanical properties are a result of polymer nanoparticle interactions that interfere with the permanent cross-linking of PEG during photopolymerization. The effect of nHAp concentration and temperature on hydrogel swelling kinetics was evaluated under physiological conditions. An increase in nHAp concentration decreased the hydrogel saturated swelling degree. The combination of PEG and nHAp nanoparticles significantly improved the physical and chemical hydrogel properties as well as some biological characteristics such as osteoblast cell adhesion. Further development of these elastomeric materials can potentially lead to use as a matrix for drug delivery and tissue repair especially for orthopedic applications.

No abstract

No abstract

No abstract

Knowledge management (KM) and organizational performance are believed to be essential of the success in business. The different results in literatures which declare KM affects organizational performance positively. But there are still some confusing relations between KM and organizational learning (OL). Accordingly, we propose some hypotheses to verify relationships among KM, organizational performance, and organizational learning (OL). Base on a sample of Taiwan knowledge-intensive firms engaged in manufacturing, and financial sectors, data are collected using a mail survey, and hypotheses are tested using structural equation modeling. This paper presents OL as a coordinating mechanism, and the results support it in these samples. Empirical evidence also supports the perspective that KM affects organizational performance through OL. This paper is one of the empirical supports for the role of OL as a mediator between KM and organizational performance. Therefore, the positioning of OL as a mediator is also an important contribution to our thinking on this topic.

No abstract

Mechanical properties of polymer hydrogels are critical to their performance as tissue engineering scaffolds especially in load bearing tissues and wound sealants. In this study, we aim to synthesize mechanically tough nanocomposite hydrogels by photo-cross-linking PEOÀPPOÀPEO triblock copolymer diacrylates (Pluronic F127 diacrylate) in the presence of silicate nanoparticles, Laponite. The resulting hydrogels have high elongations and improved toughness when compared to their polymer hydrogel counterparts. Oscillatory shear and creep experiments suggest that the silicate nanoparticles physically interact with the covalently cross-linked polymer networks and impart viscoelasticity to the hydrogels. Imaging the structures of deformed nanocomposite hydrogels with cryo-scanning electron microscopy (cryo-SEM) leads us to believe that stretched hydrogels have finer network structures with smaller pore sizes when compared to the unstretched ones. The structural transitions observed in cryo-SEM and the viscoelastic properties measured suggest that noncovalent, physical interactions between Pluronic F127 and Laponite may contribute to rearrangements of network structures at high deformations. Overall, we expect the relationships between mechanical properties and network structures to provide valuable knowledge for the future design of high-performance hydrogels with use in a variety of biotechnological, biomedical, and pharmaceutical applications.

Biomedical polymer-silicate nanocomposites have potential to become critically important to the development of biomedical applications, ranging from diagnostic and therapeutic devices, tissue regeneration and drug delivery matrixes to various bio-technologies that are inspired by biology but have only indirect biomedical relation. The fundamental understanding of polymer-nanoparticle interactions is absolutely necessary to control structure-property relationships of materials that need to work within the chemical, physical and biological constraints required by an application. This review summarizes the most recent published strategies to design and develop polymer-silicate nanocomposites (including clay based silicate nanoparticles and bioactive glass nanoparticles) for a variety of biomedical applications. Emerging trends in bio-technological and biomedical nanocomposites are highlighted and potential new fields of applications are examined.