No abstract

Tendon is a highly aligned connective tissue which transmits force from muscle to bone. Each year, people in the US sustain more than 32 million tendon injuries. To mitigate poor functional outcomes due to scar formation, current surgical techniques rely heavily on autografts. Biomaterial platforms and tissue engineering methods offer an alternative approach to address these injuries. Scaffolds incorporating aligned structural features can promote expansion of adult tenocytes and mesenchymal stem cells capable of tenogenic differentiation. However, appropriate balance between scaffold bioactivity and mechanical strength of these constructs remains challenging. The high porosity required to facilitate cell infiltration, nutrient and oxygen biotransport within three-dimensional constructs typically results in insufficient biomechanical strength. Here we describe the use of three-dimensional printing techniques to create customizable arrays of acrylonitrile butadiene styrene (ABS) fibers that can be incorporated into a collagen scaffold under development for tendon repair. Notably, mechanical performance of scaffold-fiber composites (elastic modulus, peak stress, strain at peak stress, and toughness) can be selectively manipulated by varying fiber-reinforcement geometry without affecting the native bioactivity of the collagen scaffold. Further, we report an approach to functionalize ABS fibers with activity-inducing growth factors via sequential oxygen plasma and carbodiimide crosslinking treatments. Together, we report an adaptable approach to control both mechanical strength and presence of biomolecular cues in a manner orthogonal to the architecture of the collagen scaffold itself.

A series of experiments to define feasibility, accuracy, and precision of wide‐line nuclear magnetic resonance spectroscopy as a nondestructive analytical tool for the oil content of living seeds is described. Corn samples, ranging from single seeds to 25 g, were scanned by NMR and gravimetrically analyzed. A high positive correlation (r = 0.99+) was invariably encountered. Single, 30‐sec NMR scans on 25‐g corn samples gave estimates within ŷ33 ing of the “true” oil content 95% of the time. Error associated with single, 30‐sec scans of individual corn kernels amounted to ŷ1.3 mg of oil at the same confidence level. Samples containing more than 4.5% moisture contribute to the NMR signal, and therefore oil content is overestimated. A new dimension is added to the breeding and genetics of oil crops by the application of the NMR technique in that the process is non‐destructive and feasible even for single seeds. The usefulness of the technique in studies involving the nature of water and its surrounding medium is suggested.

The effect of selection intensity and population size on the response to selection for percent oil in the grain of maize (Zea mays L.) was evaluated in a replicated experiment over ten cycles of selection. An open-pollinated variety, Armel's Reid Yellow Dent, was divided into subpopulations of 6,10 and 50 plants. Selection proportions of 17% and 5% were imposed upon each subpopulation. Selection was based on the percentage of oil in individual kernels as determined by wide-line nuclear magnetic resonance spectroscopy. As expected, total response to selection increased with larger population sizes and selection intensities. The concave shape of the response curves suggested that an appreciable part of the genetic variance can be attributed to additive genes at high initial frequencies, dominance genes at low initial frequencies, or to the generation of negative linkage disequilibrium due to selection. The consistently greater loss of vigor experienced by the more intensely selected populations reflects the enhancement of inbreeding due to artificial selection, an effect that increases with the intensity of selection. The results indicate that combined selection, based on kernels and using within- and amongfamily information, will be more efficient than other conventional selection procedures, including the normal combined scheme where selection is based on plants.

Samples of soybeans, ranging from single seed to 25 g, were scanned by NMR and then gravimetrically analyzed for oil content. High positive correlations of NMR and oil for single seed (r = 0.998) and for 25-g samples (r= 0.999) were found. Single 30-see NMR scans gave accurate estimates of the oil content of soybean seeds which had been dried to less than 4% moisture content. Fifteen samples of known percentage composition, created by mixing calculated weights of soybean oil with oven dry soybean meal (made lipid-free by petroleum ether and by carbon tetrachloride extraction), were scanned by NMR. These 15 samples, starting at 2% oil and increasing by increments of 2% oil up to 30%, had a linear relationship of NMR readouts with these known percentages of oil. These results indicate that wide-line nuclear magnetic resonance spectroscopy is an accurate, rapid and nondestructive tool for determining the oil content of soybean seeds. Since NMR scanning of seed does not alter its composition or destroy its viability, this method of oil analysis could accelerate the development of new soybean strains.