Biocompatible Customized 3D Bone Scaffolds Treated with CRFP, an Osteogenic Peptide

Background: Currently used synthetic bone graft substitutes (BGS) are either too weak to bear the principal load or if metallic, they can support loading, but can lead to stress shielding and are unable to integrate fully. In this study, we developed biocompatible, 3D printed scaffolds derived from µCT images of the bone that can overcome these issues and support the growth of osteoblasts. Methods: Cylindrical scaffolds were fabricated with acrylonitrile butadiene styrene (ABS) and Stratasys® MED 610 (MED610) materials. The 3D-printed scaffolds were seeded with Mus musculus calvaria cells (MC3T3). After the cells attained confluence, osteogenesis was induced with and without the addition of calcitonin receptor fragment peptide (CRFP) and the bone matrix production was analyzed. Mechanical compression testing was carried out to measure compressive strength, stiffness, and elastic modulus. Results: For the ABS scaffolds, there was a 9.8% increase in compressive strength (p < 0.05) in the scaffolds with no pre-coating and the treatment with CRFP, compared to non-treated scaffolds. Similarly, MED610 scaffolds treated with CRFP showed an 11.9% (polylysine pre-coating) and a 20% (no pre-coating) increase (p < 0.01) in compressive strength compared to non-treated scaffolds. Conclusions: MED610 scaffolds are excellent BGS as they support osteoblast growth and show enhanced bone growth with enhanced compressive strength when augmented with CRFP.

Spectral Characteristics and Sensor Ability of a New 1,8-Naphthalimide and Its Copolymer with Styrene

In this study, a novel 6-(allylamino)-2-(2-(dimethylamino)ethyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NI3) was synthesized and characterized. Its copolymer with styrene was also obtained. The photophysical characteristics of NI3 were investigated in organic solvents and the results were compared with those of its structural analogue, 2-allyl-6-((2-(dimethylamino)ethyl)amino)-1H-benzo[de]isoquinoline-1,3(2H)-dione (NI4). The influences of the pH in the medium and different metal ions on the fluorescent intensity of monomers and polymers were also investigated. Computational tools (DFT and TDDFT calculations) were employed when studying the structure and properties of the 1,8-naphthalimide-based chromophores. Although the position of the N,N-dimethylaminoethylamine receptor fragment did not significantly impact proton detection, it was still important for detecting metal ion sensor ability, especially for monomeric 1,8-naphthalimide structures and their copolymers with styrene.

Genome-wide screen of gamma-secretase–mediated intramembrane cleavage of receptor tyrosine kinases

Receptor tyrosine kinases (RTKs) have been demonstrated to signal via regulated intramembrane proteolysis, in which ectodomain shedding and subsequent intramembrane cleavage by gamma-secretase leads to release of a soluble intracellular receptor fragment with functional activity. For most RTKs, however, it is unknown whether they can exploit this new signaling mechanism. Here we used a system-wide screen to address the frequency of susceptibility to gamma-secretase cleavage among human RTKs. The screen covering 45 of the 55 human RTKs identified 12 new as well as all nine previously published gamma-secretase substrates. We biochemically validated the screen by demonstrating that the release of a soluble intracellular fragment from endogenous AXL was dependent on the sheddase disintegrin and metalloprotease 10 (ADAM10) and the gamma-secretase component presenilin-1. Functional analysis of the cleavable RTKs indicated that proliferation promoted by overexpression of the TAM family members AXL or TYRO3 depends on gamma-secretase cleavage. Taken together, these data indicate that gamma-secretase–mediated cleavage provides an additional signaling mechanism for numerous human RTKs.

Cadherin binding is not a limiting step for Bacillus thuringiensis subsp. israelensis Cry4Ba toxicity to Aedes aegypti larvae

Bacillus thuringiensis subsp. israelensis produces three Cry toxins (Cry4Aa, Cry4Ba and Cry11Aa) that are active against Aedes aegypti larvae. The identification of the rate-limiting binding steps of Cry toxins that are used for insect control in the field, such as those of B. thuringiensis subsp. israelensis, should provide targets for improving insecticides against important insect pests. Previous studies showed that Cry11Aa binds to cadherin receptor fragment CR7–11 (cadherin repeats 7–11) with high affinity. Binding to cadherin has been proposed to facilitate Cry toxin oligomer formation. In the present study, we show that Cry4Ba binds to CR7–11 with 9-fold lower binding affinity compared with Cry11Aa. Oligomerization assays showed that Cry4Ba is capable of forming oligomers when proteolytically activated in vitro in the absence of the CR7–11 fragment in contrast with Cry11Aa that formed oligomers only in the presence of CR7–11. Pore-formation assays in planar lipid bilayers showed that Cry4Ba oligomers were proficient in opening ion channels. Finally, silencing the cadherin gene by dsRNA (double-stranded RNA) showed that silenced larvae were more tolerant to Cry11Aa in contrast with Cry4Ba, which showed similar toxic levels to those of control larvae. These findings show that cadherin binding is not a limiting step for Cry4Ba toxicity to A. aegypti larvae.