Designer Hydrogels: Hydrogels, which consist of highly water swollen cross-linked polymer networks, can now be made with a range of chemistries and a combination of physical and chemical cross-links. They can also be designed to degrade gradually when exposed to chemical or biological signals and are thus finding use in a wide range of applications, including tissue engineering and drug delivery. Seliktar (p. 1124 ) reviews recent advances in tailoring hydrogels with specific properties and their applications to biology and medicine.

▪ Abstract The development of a tissue-engineered blood vessel substitute has motivated much of the research in the area of cardiovascular tissue engineering over the past 20 years. Several methodologies have emerged for constructing blood vessel replacements with biological functionality. These include cell-seeded collagen gels, cell-seeded biodegradable synthetic polymer scaffolds, cell self-assembly, and acellular techniques. This review details the most recent developments, with a focus on core technologies and construct development. Specific examples are discussed to illustrate both the benefits and shortcomings of each methodology, as well as to underline common themes. Finally, a brief perspective on challenges for the future is presented.