One of the Holy Grails of tissue engineering is development of a safe bioasorbable material that can be engineered to meet specific implant demands.
Several polymers are bioabsorbable, but lack the ability to be compressed for device delivery and then resiliently expand at the intended biological site. Or they lack sufficient porosity to promote adequate cellular ingrowth and proliferation.
These polymers include aliphatic polyesters and homopolymers and copolymers (random, block, segmented and graft) of monomers such as glycolic acid, glycolide, lactic acid, and, trimethylene carbonate. Polylactic acid is one of the most commonly used bioabsorbable plastics for human implant applications, such as bone anchors.
In an interview at MD&M West with Plastics Today, Deb Langer disclosed that Lubrizol's newly formed LifeScience Polymers Group, which she heads, is investigating urethane-based approaches.
Another company, Biomerix (Fremont, CA) has developed a degradable materials technology based on a crosslinked, reticulated urethane matrix. The formulation has varying degradable copolymer soft segments that can be customized to offer different degradation profiles, ranging from three months up to two years. The urethane material consists of an open-cell, three-dimensional, interconnected network of cells and pores said to encourage tissue growth.
Tailored for specific purposes
"The structure, morphology, and properties of the elastomeric matrices of this invention can be engineered or tailored over a wide range of performance by varying the starting materials and/or the processing conditions for different functional or therapeutic uses," the company states in its patent.
The implantable devices made from the material are deliverable by a catheter, endoscope, arthoscope, laproscope, cystoscope, or syringe, according to Biomerix.
The polymer contains a polycarbonate polyol component, an isocyanate component, a blowing agent, and possibly other materials including: a crosslinking agent, a chain extender, catalysts, cell openers, surfactants, or a viscosity modifier.
In an effort to promote research with the new polymers, Biomerix and KIYATEC (Pendleton, SC) launched 3DKUBE - Biomerix 3D Scaffold Preloads late last year. They are 3D scaffolds and cell culture plasticware preassembled in a single-use disposable format.
The new product will allow 3D cell-culture researchers to "just add cells" via perfusion seeding into the devices.
Actual seeding of 3D scaffolds with stem cells to create human organs is still many years off, however.