Electrospinning: a fascinating fiber fabrication technique.

Silk as a biomaterial

Fibroblasts can condense a hydrated collagen lattice to a tissue-like structure 1/28th the area of the starting gel in 24 hr. The rate of the process can be regulated by varying the protein content of the lattice, the cell number, or the con- centration of an inhibitor such as Colcemid. Fibroblasts of high population doubling level propagated in vitro, which have left the cell cycle, can carry out the contraction at least as efficiently as cycling cells. The potential uses of the system as an immu- nologically tolerated "tissue" for wound hea ing and as a model for studying fibroblast function are discussed.

Production of a tissue-like structure by contraction of collagen lattices by human fibroblasts of different proliferative

Poly(ethylene terephthalate) (PET) is used extensively worldwide in plastic products, and its accumulation in the environment has become a global concern. Because the ability to enzymatically degrade PET has been thought to be limited to a few fungal species, biodegradation is not yet a viable remediation or recycling strategy. By screening natural microbial communities exposed to PET in the environment, we isolated a novel bacterium, Ideonella sakaiensis 201-F6, that is able to use PET as its major energy and carbon source. When grown on PET, this strain produces two enzymes capable of hydrolyzing PET and the reaction intermediate, mono(2-hydroxyethyl) terephthalic acid. Both enzymes are required to enzymatically convert PET efficiently into its two environmentally benign monomers, terephthalic acid and ethylene glycol.

http://science.sciencemag.org/content/sci/351/6278/1196.full.pdf

A Bacterium That Degrades and Assimilates Poly(ethylene Terephthalate)

https://repositorium.sdum.uminho.pt/bitstream/1822/14053/1/file.pdf

Natural–origin polymers as carriers and scaffolds for biomolecules and cell delivery in tissue engineering applications

The in vitro biodegradation of Bombyx mori silk fibroin was studied by incubating fibers and films with proteolytic enzymes (collagenase type F, α-chymotrypsin type I-S, protease type XXI), for times ranging from 1 to 17 days The changes in sample weight and degree of polymerization of silk fibers exposed to proteolytic attack were negligible However, tensile properties were significantly affected, as shown by the drop of strength and elongation as a function of the degradation time Upon incubation with proteolytic enzymes, silk films exhibited a noticeable decrease of sample weight and degree of polymerization, the extent of which depended on the type of enzyme, on the enzyme-to-substrate ratio, and on the degradation time Protease was more aggressive than α-chymotrypsin or collagenase Film fragments resistant to enzymatic degradation were enriched in glycine and alanine FT-IR measurements showed that the degree of crystallinity of biodegraded films increased Soluble degradation products of silk films consisted of a range of peptides widely differing in size, deriving from the amorphous sequences of the silk fibroin chains Biodegraded fibers showed an increase of surface roughness, while films displayed surface cracks and cavities with internal voids separated by fiber-like elements

Biodegradation of Bombyx mori silk fibroin fibers and films

http://repositorium.sdum.uminho.pt/bitstream/1822/17292/1/2008%20Biodegradable%20Materials%20Based%20on%20Silk%20Fibroin%20and%20Keratin.pdf

Biodegradable Materials Based on Silk Fibroin and Keratin

In this study cutinases from Thermobifida cellulosilytica DSM44535 (Thc_Cut1 and Thc_Cut2) and Thermobifida fusca DSM44342 (Thf42_Cut1) hydrolyzing poly(ethylene terephthalate) (PET) were successfully cloned and expressed in E.coli BL21-Gold(DE3). Their ability to hydrolyze PET was compared with other enzymes hydrolyzing natural polyesters, including the PHA depolymerase (ePhaZmcl) from Pseudomonas fluorescens and two cutinases from T. fusca KW3. The three isolated Thermobifida cutinases are very similar (only a maximum of 18 amino acid differences) but yet had different kinetic parameters on soluble substrates. Their kcat and Km values on pNP–acetate were in the ranges 2.4–211.9 s–1 and 127–200 μM while on pNP–butyrate they showed kcat and Km values between 5.3 and 195.1 s–1 and between 1483 and 2133 μM. Thc_Cut1 released highest amounts of MHET and terephthalic acid from PET and bis(benzoyloxyethyl) terephthalate (3PET) with the highest concomitant increase in PET hydrophilicity as indicated by water co...

/pdf/enzymatic-surface-hydrolysis-of-pet-effect-of-structural-4wj448xowc.pdf

Enzymatic surface hydrolysis of PET : effect of structural diversity on kinetic properties of cutinases from thermobifida

Structural changes of native and regenerated silk fibroin membranes were induced by immersion in water-methanol solutions and examined as a function of immersion time and methanol concentration. X-ray diffractometry and infrared spectroscopy data showed that transition from random coil to β-sheet structure occurred favorably when both native and regenerated silk fibroin membranes were immersed in water-methanol solutions, regardless of the different immersion time. Only native silk membrane, treated for 2 min with pure methanol, maintained its original amorphous structure, as demonstrated by differential scanning calorimetric (DSC) curves. The degree of displacement, measured by thermomechanical analysis (TMA), was much greater for regenerated than for native silk fibroin membranes. SDS-PAGE pattern showed that native silk fibroin has a molecular weight of 350, while the regenerated sample is formed by a large number of polypeptides in the range of 200-50 KD. The amount of acidic and basic amino acids decreased slightly in regenerated silk fibroin. Physical properties of silk membranes treated with water-methanol solutions are discussed in terms of membrane structure, treatment conditions, and chemical structure of starting material. © 1994 John Wiley & Sons, Inc.

Giuliano Freddi

Papers

Biodegradation of Bombyx mori silk fibroin fibers and films

Biodegradable Materials Based on Silk Fibroin and Keratin

Enzymatic surface hydrolysis of PET : effect of structural diversity on kinetic properties of cutinases from thermobifida

Structural changes of silk fibroin membranes induced by immersion in methanol aqueous solutions

Degumming of silk fabric with several proteases