BACKGROUND: In vitro construction of tissue engineered cardiac muscle becomes a hot spot in recent years, and the selection and design of scaffold is the key link. However, there is lack of ideal cardiac tissue engineering scaffold material. OBJECTIVE: To evaluate the novel biodegradable polyurethane in vitro, and to discuss the feasibility of polyurethane as cardiac tissue engineeru scaffold. METHODS: A new type polyurethane (PV-Lys) was synthesized using diphenylmethane-4,4'-diisocyanate as hard segment and lysine as expand chain. The tensile and suture strength were tested in vitro respectively, hydrolytic degradation was carded out in phosphate buffer saline of pH 7.4 at 37 ℃, and cytotoxicity was evaluated by MTT measurement and morphological observation. RESULTS AND CONCLUSION: The tensile strength of the polyurethane was up to (8.1±0.1) MPa, and the suture strength was (12.2+0.8) N. The average value of the mass loss of PV-Lys was (13.1+0.3)% at 8 weeks of in vitro hydrolytic degradation. MTT assay results showed that the cytotoxic grade of the novel PV-Lys was 0-1. Cell morphology observation showed that the L929 cells were spindle-shaped or tdangular with good stretch. This PV-Lys scaffold is with favorable mechanical property, cytocompatibility, biodegradable property, which meets the requirements of tissue engineering application.

BACKGROUND:Degradable polymer materials initiate the degradation process immediately after implantation. How to regulate the degradation of these materials is rarely reported at present. OBJECTIVE:To study the effect of ultrasonic wave on control ing the degradation of polymer materials. METHODS:The sample is made ofε-caprolactone/L-lactide copolymer, and its core was coated with low density polyethylene on the surface with the fol owing four different methods. (1) The core surface was firstly covered with CaCl 2 powder, and then coated with polyethylene. (2) The core was firstly coated with polyethylene and coarsened for 3 hours. (3) The core surface was firstly covered with CaCl 2 powder, and then coated with polyethylene, and coarsened for 3 hours. (4) The core was directly coated with polyethylene. The four kinds of specimens obtained were embedded in pork for ultrasonic bombardment experiment in vitro. RESULTS AND CONCLUSION:In the specimens prepared with methods 1 and 4, the lyophobic layer could protect core materials before ultrasonic treatment, and no absorption peak was found at 631 nm. After ultrasonic treatment, the lyophobic layer was destroyed, toluidine blue dye was released, leading to change the color of immersion solution and increase the absorption peak at 631 nm. In the specimens prepared with methods 2 and 3,the lyophobic layer cannot exhibit the protection effects, the absorption peak was found at 631 nm. Under electron microscope, the appearance of the specimens in four groups was changed obviously. It is feasible to control the starting of the degradation by coating the degradable copolymer with LDPE and using ultrasonic as a trigger.

A novel diisocyanate, i. e. lysine ethyl ester diisocyanate (LDI), was prepared by the present authors. Poly (epsilon-caprolactone) (PCL) (M(n) = 2000) was used for reacting with LDI to form prepolymer, and then the chain was extended with butanediol (BDO) to form polyurethane (PU). PU was characterized by gel permeation chromatography, FTIR and 1H-NMR. Mechanical properties test revealed that PU possesses excellent tensile strength. Hydrolytic degradation and enzymatic degradation of PU films showed that PU is biodegradable. Finally, vascular scaffold of PU was fabricated by electrospinning. Morphological and biomechanical properties of scaffold were examined. The tensile strength was 8MPa, suture retention strength 12N, porosity 75% and burst pressure strength 150-170 kPa. Cytotoxicity and cell adhesion showed that PU scaffolds are biocompatible. These results demonstrate that PU vascular scaffolds possess excellent physical strength and biocompatibility and can be developed as substitutes for native blood vessels.
Biocompatible Materials ; chemical synthesis ; chemistry ; Blood Vessel Prosthesis ; Isocyanates ; chemistry ; Lysine ; analogs & derivatives ; chemistry ; Polyesters ; chemistry ; Polyurethanes ; chemical synthesis ; chemistry ; Tissue Engineering ; methods ; Tissue Scaffolds