Automated micro method for enzymatic L(+) and D(-) lactic acid determinations in biological fluids containing cellular extracts.

Automated micro methods for the rapid assay of l(+) and d(?) lactic acid in rumen fluid and other biological extracts were developed using an Auto-samplerpump system and UV-Vis Spectrophotometer. Both involved the use of l(+) and d(?) LDH enzymes, with the reduction of NAD⁺ to NADH₂ measured at 340 nm. These enzymatic methods are highly specific for either isomer, run at a rate of 60 samples/hr, use minimal quantities of reagents, and require only 40 to 80 μl of sample.     

Rheological properties of cross-linked hyaluronan-gelatin hydrogels for tissue engineering

Hydrogels that mimic the natural extracellular matrix (ECM) are used in three-dimensional cell culture, cell therapy, and tissue engineering. A semi-synthetic ECM based on cross-linked hyaluronana offers experimental control of both composition and gel stiffness. The mechanical properties of the ECM in part determine the ultimate cell phenotype. We now describe a rheological study of synthetic ECM hydrogels with storage shear moduli that span three orders of magnitude, from 11 to 3 500 Pa, a range important for engineering of soft tissues. The concentration of the chemically modified HA and the cross-linking density were the main determinants of gel stiffness. Increase in the ratio of thiol-modified gelatin reduced gel stiffness by diluting the effective concentration of the HA component.