Tissue Engineering Techniques to Control Biomineralization

Nacre is the shiny lustrous inner layer of seashells. Also known as mother of pearl, it is a biomineral with a highly ordered structure that is controlled by proteins within its organic matrix. Nacre is comprised of mineral plates and an organic matrix that are arranged in a “brick and mortar” motif. The mineral is 3,000 times stronger than its geologic counterpart because of this arrangement. The proteins responsible for this organization are also capable of initiating bone formation, and our current efforts concentrate on isolating these proteins for incorporation within biosynthetic materials to direct osteogenesis.

Cell therapy is the practice of using cells as tiny factories to deliver a therapeutic agent of choice to a wound or tissue. Such therapies have been used to effect bone formation, wound healing, and to control glucose levels in diabetics. The largest hurdle to overcome is rejection of donor cells. By microencapsulating cells within polyethylene glycol (PEG) hydrogels, we have been able to immunoisolate these cells. In the image above, we encapsulated insulin secreting cells and used them to effect rapid wound healing. The cells are entrapped within PEG hydrogel microspheres between 100 - 300 micrometers in size (about the width of 1-3 human hairs). The image shows fluorescent staining of viable cells (live glows green, dead glows red).

Functionalized scaffolds have moieties incorporated into them to direct cell behavior. Electroactive scaffolds respond to electrical stimulation with a mechanical response and piezoelectric scaffolds respond to mechanical stimulation with an electrical response. We are exploring ways to combine these properties to develop better scaffolds for excitable tissues such as muscle and nerve.