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Contemporary treatment of critical bone defect remains a significant challenge in the field of orthopedic surgery. Engineered biomaterials combined with growth factors have emerged as a new treatment alternative in bone repair and regeneration. Our approach is to encapsulate bone morphogenetic protein-2 (BMP-2) into a polymeric matrix in different ways and characterize their individual performance in a nude mouse model. The main objective of this study is to examine whether the PLGA/HAp composite fibrous scaffolds loaded with BMP-2 through electrospinning can improve bone regeneration. The hypothesis is that different loading methods of BMP-2 and different HAp contents in scaffolds can alternate the release profiles of BMP-2 in vivo, therefore modify the performance of scaffolds in bone regeneration. Firstly, mechanical strength of scaffolds and HAp nanoparticles distribution in scaffolds were investigated. Secondly, nude mice experiments extended to 6 weeks were carried out to test the in vivo performance of these scaffolds, in which measurements, like serum BMP-2 concentration, ALP activity, X-ray qualification, and H&E/IHC tissue staining were utilized to monitor the growth of new bone and the changes of the corresponding biochemical parameters. The results showed that the PLGA/HAp composite scaffolds developed in this study exhibited good morphology/mechanical strength and HAp nanoparticles were homogeneously dispersed inside PLGA matrix. Results from the animal experiments indicate that the bioactivity of BMP-2 released from the fibrous PLGA/HAp composite scaffolds is well maintained, which further improves the formation of new bone and the healing of segmental defects in vivo. It is concluded that BMP-2 loaded PLGA/HAp composite scaffolds are promising for bone healing.

In the summer of 2008, serious illnesses and deaths of babies in China were linked to melamine-tainted powdered infant formula. Melamine contains several metabolites, such as ammeline, ammelide, and cyanuric acid, and has been used for the adulteration of foods or milk to increase their apparent protein content. It is assumed that melamine and its metabolites are absorbed in the gastrointestinal tract, and precipitate in the kidney to form crystals. A new tolerable daily intake of 0.2 mg kg(-1) body weight was adapted by the World Health Organization in 2008. This paper reviews the variety of analytical methods that have been used for the analysis of melamine in food. The limit of detection of these various methods is 0.05-100 ppm. The maximum acceptable concentration in food has been set at 50 ppb by the US FDA. A fast and ultrasensitive procedure for screening, detection, and characterization of melamine and its derivative compounds needs to be established. Currently, mass-spectrometry technologies provide an alternative to derivatization for regulatory analysis of food.

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Cell-matrix adhesion is one of the important interactions that regulates stem cell survival, self-renewal, and differentiation. Our previous report (Wu SC, Chang JK, Wang CK, Wang GJ, Ho ML. Biomaterials 31: 631-640, 2010) indicated that a microenvironment enriched with hyaluronan (HA) initiated and enhanced chondrogenesis in human adipose-derived stem cells (hADSCs). We further hypothesize that HA-induced chondrogenesis in hADSCs is mainly due to the interaction of HA and CD44 (HA-CD44), a cell surface receptor of HA. The HA-CD44 interaction was tested by examining the mRNA expression of hyaluronidase-1 (Hyal-1) and chondrogenic marker genes (SOX-9, collagen type II, and aggrecan) in hADSCs cultured on HA-coated wells. Cartilaginous matrix formation, sulfated glycosaminoglycan, and collagen productions by hADSCs affected by HA-CD44 interaction were tested in a three-dimensional fibrin hydrogel. About 99.9% of hADSCs possess CD44. The mRNA expressions of Hyal-1 and chondrogenic marker genes were upregulated by HA in hADSCs on HA-coated wells. Blocking HA-CD44 interaction by anti-CD44 antibody completely inhibited Hyal-1 expression and reduced chondrogenic marker gene expression, which indicates that HA-induced chondrogenesis in hADSCs mainly acts through HA-CD44 interaction. A 2-h preincubation and coculture of cells with HA in hydrogel (HA/fibrin hydrogel) not only assisted in hADSC survival, but also enhanced expression of Hyal-1 and chondrogenic marker genes. Higher levels of sulfated glycosaminoglycan and total collagen were also found in HA/fibrin hydrogel group. Immunocytochemistry showed more collagen type II, but less collagen type X, in HA/fibrin than in fibrin hydrogels. Our results indicate that signaling triggered by HA-CD44 interaction significantly contributes to HA-induced chondrogenesis and may be applied to adipose-derived stem cell-based cartilage regeneration.

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