Environmentally Degradable Parameter (Ed
K) is of importance in the describing of biodegradability of environmentally biodegradable polymers (BDPs). In this study, a concept Ed
K was introduced. A test procedure of using the ISO 14852 method and detecting the evolved carbon dioxide as an analytical parameter was developed, and the calculated Ed
K was used as an indicator for the ultimate biodegradability of materials. Starch and polyethylene used as reference materials were defined as the Ed
K values of 100 and 0, respectively. Natural soil samples were inoculated into bioreactors, followed by determining the rates of biodegradation of the reference materials and 15 commercial BDPs over a 2-week test period. Finally, a formula was deduced to calculate the value of Ed
K for each material. The Ed
K values of the tested materials have a positive correlation to their biodegradation rates in the simulated soil environment, and they indicated the relative biodegradation rate of each material among all the tested materials. Therefore, the Ed
K was shown to be a reliable indicator for quantitatively evaluating the potential biodegradability of BDPs in the natural environment.
In this study, two biodegradable polyesters [i.e., polylactic acid (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx)] with complementarity in terms of mechanical performance have been combined, and a series of blends with a broad range of compositions has been prepared by thermal compounding. The evolution of phase morphologies with the variation of compositions has been characterized by using Fourier transform infrared spectroscopic imaging together with scanning electron microscope analyses. Thermal, mechanical, and biodegradation properties of the PLA/PHBHHx blends were systematically investigated. Mechanical properties were further analyzed by using theoretical models and correlated with the results of the morphology/structure and compatibility of the blends. Results indicate that PLA/PHBHHx blends are immiscible but can be compatible to some extent at certain compositions (e.g., PLA/PHBHHx (w/w) = 80/20 and 20/80). The physical properties of the blend could be fine tuned by adjusting the blend composition.
When Pseudomonas mendocina NK-01 was cultivated in a 200-L fermentor using glucose as carbon source, 0.316 g L(-1) medium-chain-length polyhydroxyalkanoate (PHA(MCL)) and 0.57 g L(-1) alginate oligosaccharides (AO) were obtained at the end of the process. GC/MS was used to characterize the PHA(MCL), which was found to be a polymer mainly consisting of 3HO (3-hydroxyoctanoate) and 3HD (3-hydroxydecanoate). T (m) and T (g) values for the PHA(MCL) were 51.03 °C and -41.21 °C, respectively, by DSC. Its decomposition temperature was about 300 °C. The elongation at break was 700% under 12 MPa stress. MS and GPC were also carried out to characterize the AO which had weight-average molecular weights of 1,546 and 1,029 Da, respectively, for the two main components at the end of the fermentation process. MS analysis revealed that the AO were consisted of β-D-mannuronic acid and/or α-L-guluronic acid, and the β-D-mannuronic acid and/or α-L-guluronic acid residues were partially acetylated at position C2 or C3.
The human eye has ethnic difference, the existing typical eye models are based on western eyes. A generic eye model based on Chinese population is presented for the first time. The statistical analyzed ocular parameters based on measured data are used for the initial generic eye model, and the wavefront aberration data obtained at two different pupil diameters are used for reproduction by optimizing the initial generic eye model. The differences and similarities between Chinese generic eye model and western eye models are given. The Chinese generic eye model provides a suitable model for the related further researches and applications on Chinese eye.
Poly(3-hydroxybutyrate-co-4-hydroxybutyrate), poly(ε-caprolactone), and poly(1actide-co-glycolide) films were prepared by solution casting and electrospinning. The degradability of cast films was evaluated in vitro and in vivo by recording the weight remaining, observing the morphology, and measuring change in molecular weight and Mw/Mn polydispersity. In addition, cell proliferation on electrospun films was tested by MTT assay, and cell infiltration into electrospun films was assessed through subcutaneous implantation in rats. By analyzing data obtained from these tests, we discovered that the degradation rates of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers were between those of poly(ε-caprolactone) and poly(1actide-co-glycolide) and could be controlled by adjusting 4-hydroxybutyrate content. Moreover, tissue responses to materials made from poly(3-hydroxybutyrate-co-4-hydroxybutyrate) were milder compared with those elicited by poly(ε-caprolactone) and poly(1actide-co-glycolide), and poly(3-hydroxybutyrate-co-4-hydroxybutyrate) films exhibited a good and moderate cell infiltration. Therefore, our data demonstrate that poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers are promising candidates for the construction of scaffolds designed for various types of tissue regeneration with special biodegradability requirements.
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