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There is a growing demand for off-the-shelf tissue engineered vascular grafts (TEVGs) for replacement or bypass of damaged arteries in various cardiovascular diseases. Scaffolds from the decellularized tissue skeletons to biopolymers and biodegradable synthetic polymers have been used for fabricating TEVGs. However, several issues have not yet been resolved, which include the inability to mimic the mechanical properties of native tissues, and the ability for long term patency and growth required for in vivo function. Electrospinning is a popular technique for the production of scaffolds that has the potential to address these issues. However, its application to human TEVGs has not yet been achieved. This review provides an overview of tubular scaffolds that have been prepared by electrospinning with potential for TEVG applications.

Abstract:The focus in the field of biomedical engineering has shifted in recent years to biodegradable polymers and, in particular, polyesters. Dozens of polyester-based medical devices are commercially available, and every year more are introduced to the market. The mechanical performance and wide range of biodegradation properties of this class of polymers allow for high degrees of selectivity for targeted clinical applications. Recent research endeavors to expand the application of polymers have been driven by a need to target the general hydrophobic nature of polyesters and their limited cell motif sites. This review provides a comprehensive investigation into advanced strategies to modify polyesters and their clinical potential for future biomedical applications.

The three most common methods of sterilization in use today are ethylene oxide exposure, ␥-irradiation, and steam sterilization. Each of these methods has serious limitations for the sterilization of some materials used in medicine, especially thermally and hydrolytically sensitive polymers by themselves and in combination with proteins. In this work, we demonstrate a potential new method of sterilization by using supercritical f luid carbon dioxide. Using this method we achieve complete inactivation of a wide variety of bacterial organisms at moderate temperatures and in the absence of organic solvents or irradiation. Sterilization is a function of both the proximity to the f luid's critical point and the chemical nature of the f luid itself. When biodegradable polymers poly(lactic-co-glycolic) acid and polylactic acid were included in the sterilization process, there was no effect on the inactivation efficiency, yet no physical or chemical damage to these thermally and hydrolytically labile materials was observed.

Abstract. The aim of this review paper is to compare the potential of various techniques developed for production of homogenous, stable liposomes. Traditional techniques, such as Bangham, detergent depletion, ether/ethanol injection, reverse-phase evaporation and emulsion methods, were compared with the recent advanced techniques developed for liposome formation. The major hurdles for scaling up the traditional methods are the consumption of large quantities of volatile organic solvent, the stability and homogeneity of the liposomal product, as well as the lengthy multiple steps involved. The new methods have been designed to alleviate the current issues for liposome formulation. Dense gas liposome techniques are still in their infancy, however they have remarkable advantages in reducing the use of organic solvents, providing fast, single-stage production and producing stable, uniform liposomes. Techniques such as the membrane contactor and heating methods are also promising as they eliminate the use of organic solvent, however high temperature is still required for processing.

The dissolution of a drug into the biological environment can be enhanced by reducing the particle size of the drug. In this study the rapid expansion of supercritical solutions (RESS) process was employed to micronize racemic ibuprofen, and the dissolution rate of the micronized product in a buffered solution was examined. The chiral nonsteroidal antiinflammatory, racemic ibuprofen, was used as a model drug because its dissolution rate is limited by its poor solubility in water. The phase behavior of the ibuprofen−CO2 binary system was investigated prior to the solubility measurements being undertaken. The solubility of racemic ibuprofen in supercritical CO2 was measured using a dynamic apparatus at pressures between 80 and 220 bar and temperatures of 35, 40, and 45 °C. The solubility data was modeled using the Peng−Robinson equation of state with van der Waals mixing rules. The ratio of R and S isomers in the extract was found to be the same as that in the original material. The solubility of pure optical isomers of ibuprofen, namely, (S)-ibuprofen and (R)-ibuprofen, were also determined at 35 °C within the pressure range of 80−200 bar. It was found that (S)-ibuprofen exhibited solubility in CO2 similar to (R)-ibuprofen, and the solubility of the pure isomers was at least 60% higher than that of the racemic ibuprofen at all pressures. The RESS experiments involved studying the effect of spraying distance, the pre-expansion pressure, and nozzle length on the particle size. The median particle size of ibuprofen precipitated by RESS was less than 2.5 μm. Although the particles obtained were aggregated, they were easily dispersed by ultrasonication in water. The pre-expansion pressure and nozzle length had no effect on the particle size and morphology within the range of operating conditions studied. An increase in spraying distance resulted in a slight decrease in particle size and degree of aggregation. The powder dissolution rate of racemic ibuprofen was enhanced as the particle size decreased. The degree of crystallinity of the processed ibuprofen was slightly decreased; as a result, the micronized product exhibited a higher disk intrinsic dissolution rate. The increase in dissolution rate of ibuprofen was hence due to both the reduction in particle size and the degree of crystallinity.

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