Source: {"pile_set_name": "USPTO Backgrounds"}

Tissue replacements suffer from a lack of appropriate donors, tissue typing, availability, homogeneity and variety leading to the failure in many cases of transplants. In the case of autotransplants for example, mammary artery or femoral vein substitutes for coronary artery bypass, the tissue from which these tissues are taken can lead to stress or injury. Current 3D printing for tissues is a highly complex process and requires a specialized laboratory and printing facility using complex and highly expensive materials. There is a need for a wider variety of tissue types which can be used to take the place of diseased or damaged tissues. Further, currently, polyvinyl alcohol (PVA) is used in 3D printing as a water soluble support matrix which can rapidly dissolve to permit complex structure printing. PVA in its unmodified state though, is challenging to use for biological devices. For the foregoing reasons, there is a pressing, but seemingly irresolvable need for a flexible, biologically compatible scaffolding, able to covalently bind growth factors and act as a support matrix for integrating living cells.