The effect of an alginate carrier on bone formation in a hydroxyapatite scaffold.

This study investigated the osteoconductive properties of a porous hydroxyapatite (HA) scaffold manufactured using a novel technique similar to the bread-making process, alone and in combination with an alginate polysaccharide fiber gel (HA/APFG putty) and autologous bone marrow aspirate (BMA). The hypothesis was that the HA/APFG putty would be as osteoconductive as granular HA and that the presence of BMA would further enhance bone formation in an ovine femoral condyle critical defect model. Thirty-six defects were created and either (1) porous HA granules, (2) HA/APFG putty, or (3) HA/APFG putty + BMA were implanted. After retrieval at 6 and 12 weeks, image analysis techniques were used to quantify bone apposition rates, new bone area, bone-HA scaffold contact, and implant resorption. At 6 weeks postsurgery, significantly lower bone apposition rates were observed in the HA/APFG putty group when compared to the HA (p = 0.014) and HA/APFG putty + BMA (p = 0.014) groups. At 12 weeks, significantly increased amounts of new bone formation were measured within the HA scaffold (33.56 ± 3.53%) when compared to both the HA/APFG putty (16.69 ± 2.7%; p = 0.043) and the defects containing HA/APFG putty + BMA (19.31 ± 3.8%; p = 0.043). The use of an APFG gel as a carrier for injectable CaP bone substitute materials delayed bone formation in this model compared to HA granules alone which enhanced bone formation especially within the interconnected smaller pores. Our results also showed that the addition of autologous BMA did not further enhance its osteoconductive properties. Further study is required to optimize the degradation rate of this APFG binding agent before using as a directly injectable material for repair of bone defect. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1328-1335, 2016.

Twisting-based spectroscopic measure of solvent polarity: the P(T) scale.

The P(T) scale, which is correlated well with the E(T)(30), Y, and Z scales, is the first twisting-based spectroscopic measure of solvent polarity. It is based on two combined mechanisms: (1) the solvent-dependent intramolecular charge-transfer absorption that displays a regular hypsochromic band shift in polar solvents and (2) overcoming the intramolecular hydrogen-bond of o-1 by its differentiated solvation in polar solvents, causing a C-C bond to twist that leads to a regular hypsochromic shift of its lowest energy electronic absorption band.

Synthesis, photophysical properties, and application of o- and p-amino green fluorescence protein synthetic chromophores.

The o- and p-amino green-fluorescence-protein synthetic chromophores (GFPSCs) were synthesized from the corresponding o- and p-nitro protecting group. Among the four protecting groups of the o-amino group, the o-nitro protecting group is the only choice to synthesize the o-amino GFPSCs. The first singlet excited states of o- and p-amino GFPSCs carry significant charge-transfer character through the mechanism of photoinduced charge transfer (PCT). The o-amino GFPSCs can serve as wavelength-ratiometric fluorescence sensors that selectively recognize Cr(3+) in aqueous medium through a PCT mechanism.

The effect of different surface morphology and roughness on osteoblast-like cells.

Increased magnitude of biomaterial surface roughness and micromachined-grooved surfaces has both been shown to stimulate osteoblast activity, but have not been compared in the same study quantitatively. A series of titanium alloy (Ti6Al4V) samples were prepared using simple machining techniques to undertake such a comparison. Samples were either grit blasted (Gb) or shot peened (Sp) to give random discontinuities, or silicon carbide ground (SiC) to produce ordered grooves. These were compared with micropolished samples (Mp). The samples were coated with a 1 mum continuous coating of hydroxyapatite to remove differences in surface chemistry. Human osteoblast-like cells were seeded onto the materials and metabolic activity, proliferation, alkaline phosphatase activity, and osteocalcin production assessed. Cell responses were highly dependent on the substrate that they were cultured on. Cells cultured on the smooth and ordered (Mp and SiC, respectively) samples had higher metabolic activity and a more elongated morphology than those cultured on the randomly structured Gb or Sp samples. Over 21 days, cell metabolic activity peaked relative to the control between 7 and 14 days on the Mp sample, and between 14 and 21 days on the Gb, Sp, and SiC samples. In common with other researchers, we note that micron scale topography may have potential for influencing osseointegration. More importantly, as the magnitude of the discontinuities on SiC, Gb, and Sp were similar, the differences in cell responses does not appear to lie with the size of the features, but whether the features showed an ordered or disordered structure.

Enzymatic and nonenzymatic synthesis of glutathione conjugates: application to the understanding of a parasite's defense system and alternative to the discovery of potent glutathione S-transferase inhibitors.

A primary pathway for metabolism of electrophilic compounds in Schistosoma japonicum involves glutathione S-transferase (SjGST)-catalyzed formation of glutathione (GSH) conjugates. As part of a program aimed at gaining a better understanding of the defense system of parasites, a series of aromatic halides (1-8), aliphatic halides (9, 10), epoxides (11-20), alpha,beta-unsaturated esters (21, 22), and alpha,beta-unsaturated amides (23, 24) were prepared, and their participation in glutathione conjugate formation was evaluated. Products from enzymatic and nonenzymatic reactions of these substances with glutathione were characterized and quantified by using reverse-phase high-performance liquid chromatography (HPLC), NMR, and fast atom bombardment mass spectrometry (FAB-MS) analysis. Mechanisms for formation of specific mono(glutathionyl) or bis(glutathionyl) conjugates are proposed. Although the results of this effort indicate that SjGST does not catalyze addition or substitution reactions of 1, 3, 4, 7-9, 11-13, 15-17, 19-21, and 24, they demonstrate that 2, 5, 6, 14, 18, and 23 undergo efficient enzyme-catalyzed conjugation reactions. The kcat values for SjGST with 23 and 18 are about 886-fold and 14-fold, respectively, larger than that for 5. This observation suggests that 23 is a good substrate in comparison to other electrophiles. Furthermore, the initially formed conjugation product, 23a, is also a substrate for SjGST in a process that forms the bis(glutathionyl) conjugate 23b. Products arising by enzymatic and nonenzymatic pathways are generated under the conditions of SjGST-activated GSH conjugation. Interestingly, production of nonenzymatic GSH conjugates with electrophilic substrates often overwhelms the activity of the enzyme. The nonenzymatic GSH conjugates, 9a-11a, 16a, 21a, and 22a, are inhibitors of SjGST with respective IC50 values of 1.95, 75.5, 0.96, 19.0, 152, and 0.36 microM, and they display moderate inhibitory activities against human GSTA2. Direct evidence has been gained for substrate inhibition by 10 toward SjGST and GSTA2 that is more potent than that of its GSH conjugate 10a. The significance of this work is found in the development of a convenient NMR-based technique that can be used to characterize glutathione conjugates derived from small molecule libraries as part of efforts aimed at uncovering specific potent SjGST and GSTA2 inhibitors. This method has potential in applications to the identification of novel inhibitors of other GST targets that are of chemotherapeutic interest.