Modification of Poly(propylene fumarate)-Bioglass Composites with Peptide Conjugates to Enhance Bioactivity.

Poly(propylene fumarate) (PPF) has been highlighted as one of the most promising materials for bone regeneration. Despite the promising advantages of using polymer scaffolds for biomedical applications, their inherent lack of bioactivity has limited their clinical application. In this study, PPF was successfully functionalized with Bioglass and a novel catechol-bearing peptide bioconjugate containing bioactive short peptide sequences of basic fibroblast growth factor, bone morphogenetic protein 2, and osteogenic growth peptide. The binding affinity was assessed to be around 110 nmol/cm2 with the Bioglass content at 10 wt %. Fluorescence imaging studies show that the catechol-bearing modular peptide binds preferentially to the Bioglass. A 4 week in vitro cell study using human mesenchymal stem cells showed that cell adhesion, spreading, proliferation, and osteogenic differentiation at both gene and protein levels were all improved by the introduction of peptides, demonstrating the potential approach of dually functionalized polymers for bone regeneration.

Effect of Chemical and Physical Properties on the In Vitro Degradation of 3D Printed High Resolution Poly(propylene fumarate) Scaffolds.

Two distinct molecular masses of poly(propylene fumarate) (PPF) are combined with an additive manufacturing process to fabricate highly complex scaffolds possessing controlled chemical properties and porous architecture. Scaffolds were manufactured with two polymer molecular masses and two architecture styles. Degradation was assessed in an accelerated in vitro environment. The purpose of the degradation study is not to model or mimic in vivo degradation, but to efficiently compare the effect of modulating scaffold properties. This is the first study addressing degradation of chain-growth synthesized PPF, a process that allows for considerably more control over molecular mass distribution. It demonstrates that, with greater process control, not only is scaffold fabrication reproducible, but the mechanical properties and degradation kinetics can be tailored by altering the physical properties of the scaffold. This is a clear step forward in using PPF to address unmet medical needs while meeting regulatory demands and ultimately obtaining clinical relevancy.

Synthesis and Biological Evaluation of Well-Defined Poly(propylene fumarate) Oligomers and Their Use in 3D Printed Scaffolds.

A ring opening polymerization method for synthesizing oligomeric poly(propylene fumarate) (PPF) provides a rapid, and scalable method of synthesizing PPF with well-defined molecular mass, molecular mass distribution (Dm), and viscosity properties suitable for 3D printing. These properties will also reduce the amount of solvent necessary to ensure sufficient flow of material during 3D printing. MALDI mass spectrometry precisely shows the end group fidelity, and size exclusion chromatography (SEC) demonstrates narrow mass distributions (<1.6) of a series of low molecular mass oligomers (700-3000 Da). The corresponding intrinsic viscosities range from 0.0288 ± 0.0009 dL/g to 0.0780 ± 0.0022 dL/g. The oligomers were printed into scaffolds via established photochemical methods and standardized ISO 10993-5 testing shows that the 3D printed materials are nontoxic to both L929 mouse fibroblasts and human mesenchymal stem cells.

Molecular Basis for Necitumumab Inhibition of EGFR Variants Associated with Acquired Cetuximab Resistance.

Acquired resistance to cetuximab, an antibody that targets the EGFR, impacts clinical benefit in head and neck, and colorectal cancers. One of the mechanisms of resistance to cetuximab is the acquisition of mutations that map to the cetuximab epitope on EGFR and prevent drug binding. We find that necitumumab, another FDA-approved EGFR antibody, can bind to EGFR that harbors the most common cetuximab-resistant substitution, S468R (or S492R, depending on the amino acid numbering system). We determined an X-ray crystal structure to 2.8 Å resolution of the necitumumab Fab bound to an S468R variant of EGFR domain III. The arginine is accommodated in a large, preexisting cavity in the necitumumab paratope. We predict that this paratope shape will be permissive to other epitope substitutions, and show that necitumumab binds to most cetuximab- and panitumumab-resistant EGFR variants. We find that a simple computational approach can predict with high success which EGFR epitope substitutions abrogate antibody binding. This computational method will be valuable to determine whether necitumumab will bind to EGFR as new epitope resistance variants are identified. This method could also be useful for rapid evaluation of the effect on binding of alterations in other antibody/antigen interfaces. Together, these data suggest that necitumumab may be active in patients who are resistant to cetuximab or panitumumab through EGFR epitope mutation. Furthermore, our analysis leads us to speculate that antibodies with large paratope cavities may be less susceptible to resistance due to mutations mapping to the antigen epitope. Mol Cancer Ther; 17(2); 521-31. ©2017 AACR.

Nondestructive evaluation of hydrogel mechanical properties using ultrasound.

The feasibility of using ultrasound technology as a noninvasive, nondestructive method for evaluating the mechanical properties of engineered weight-bearing tissues was evaluated. A fixture was designed to accurately and reproducibly position the ultrasound transducer normal to the test sample surface. Agarose hydrogels were used as phantoms for cartilage to explore the feasibility of establishing correlations between ultrasound measurements and commonly used mechanical tissue assessments. The hydrogels were fabricated in 1-10% concentrations with a 2-10 mm thickness. For each concentration and thickness, six samples were created, for a total of 216 gel samples. Speed of sound was determined from the time difference between peak reflections and the known height of each sample. Modulus was computed from the speed of sound using elastic and poroelastic models. All ultrasonic measurements were made using a 15 MHz ultrasound transducer. The elastic modulus was also determined for each sample from a mechanical unconfined compression test. Analytical comparison and statistical analysis of ultrasound and mechanical testing data was carried out. A correlation between estimates of compressive modulus from ultrasonic and mechanical measurements was found, but the correlation depended on the model used to estimate the modulus from ultrasonic measurements. A stronger correlation with mechanical measurements was found using the poroelastic rather than the elastic model. Results from this preliminary testing will be used to guide further studies of native and engineered cartilage.

A clinical trial demonstration of a web-based test for alcohol and drug effects.

OBJECTIVE: The purpose of this study was to determine the feasibility of a Web-installed test of skills essential to driving: target detection and divided attention. The Attention Assessment (TAA) was designed for use in global clinical trials to document the effects of alcohol and other drugs. METHOD: Scoring algorithms and data-storage tools were installed on servers in bicoastal U.S. locations. IBM PC-compatible test units with encrypted Web access and 19-inch monitors were installed at a Canadian site. A single-center, crossover design was used to compare the pharmacodynamic properties of a pharmaceutical compound under development with those of alcohol (blood alcohol concentration [BAC]=.10%) over time. For this study, 33 subjects completed four 36-hour testing periods. Blood samples and pharmacodynamic assessments were performed at 0, 1, 3, 5, 7, 9, 12, and 24 hours. Analysis of covariance was conducted on six composite TAA scores as change from baseline. RESULTS: Five of the six composite scores showed significant ethanol effects (p<.02) over a BAC range of. 1% to .05%. Within-session test-retest reliability was r=.86 and between periods was r=.51 (between Periods 1 and 2), .83 (between Periods 2 and 3), and .81 (between Periods 3 and 4). Individual impairment was evident at .05%. CONCLUSIONS: It was possible to conduct sensitive alcohol/other drug testing from a central database with secure scoring. Test installation, data monitoring, and norms assembly were performed at a remote location. TAA gives researchers the ability to immediately and normatively evaluate alcohol and drug effects in diverse global locations. Secondary applications include clinical or worksite testing. The data show improved precision over previous test versions to map the effect of drugs on visual/cognitive skills involved in driving.

Development of a policy-relevant child maltreatment research strategy.

Child maltreatment is associated with a huge burden of suffering, yet there are serious gaps in knowledge about its epidemiology and approaches to intervention. This article describes the development of a proposed national research framework in child maltreatment, as requested by the Department of Justice, Canada, based on (1) a review of the literature, (2) consultation with experts, and (3) application of evaluation criteria for considering research priorities. The article identifies gaps in knowledge about child maltreatment in Canada and proposes a research agenda to make evidence-based policy decisions more likely. Although this work was driven by gaps in Canada's knowledge about child maltreatment, the international scope of the review and consultation process could make the findings useful to broader research and policy audiences.

Variability in the human immunodeficiency virus type 1 gp120 Env protein linked to phenotype-associated changes in the V3 loop.

Isolates of human immunodeficiency virus type 1 (HIV-1) are classified according to the chemokine receptor (coreceptor) used in conjunction with CD4 to target and enter cells: viruses using CCR5 and CXCR4 are classified as R5 and X4, respectively. The major determinant of entry-related HIV-1 phenotypes is known to reside in the third variable region of gp120 (V3). It is clear, however, that positions outside of V3 play some role in influencing phenotype, although marked context dependence and extensive variability among HIV-1 isolates have made the identification of these positions difficult. We used the presence of previously described substitutions in V3 to classify a large set of HIV-1 subtype B gp120 sequences available in public databases as X4-like or R5-like. Using these classifications, we searched for positions outside of V3 where either amino acid composition or variability differed significantly among sequences of different inferred phenotypes. Our approach took the epidemiological relationships among sequences into account. A cluster of positions linked to changes in V3 was identified between amino acids 190 and 204 of gp120, immediately C-terminal of V2; changes at position 440 in C4 were also linked to inferred phenotype. Structural data place these positions at the coreceptor-binding face of gp120 in a surface-exposed location. We also noted a significant increase in net positive charge in a highly variable region of V2. This study both confirms previous observations and predicts specific positions that contribute to a functional relationship between V3, V2, and C4.