>> Research Projects >> New Biocompatible & Bioactive Poymer Synthesis

1. Synthesizing highly elastic, biodegradable, bioactive polymer for tissue engineering and regenerative medicine.

Although most of currently investigated degradable polymers are well tolerated by cells in cultures and in tissues, the mechanical properties of these polymers are not compatible with natural tissues. For example, most natural tissues, such as heart, blood vessels, skeletal muscle, tendon, ligament, and so on, are very elastic and strong. Most degradable polymers are either too stiff/brittle with low elongation, or very soft with relative low strength. With the increasing interests in engineering various tissues for the treatment of many types of injuries and diseases, a wide variety of degradable polymers with desirable mechanical, degradation, and cytophilic properties are needed. To this end, several series of biocompatible degradable elastic polymers with different properties were developed in Dr. Wen’s lab (Several papers in preparation). To further control the cell-biomaterial interaction, several types of bioactive elastic polymers were developed and more varieties of polymers are in progress. For example, one objective is to develop bulk polymers with the property of preventing platelet adhesion, inhibiting smooth muscle proliferation, but promoting endothelial cell adhesion. Many researchers using surface immobilization strategy to attach bioactive peptides on the surface of materials for this purpose, however, even peptide was covalently bound to the surface,  when polymer degraded and peptides may be washed away very quickly. To prevent the loss of surface immobilized peptides, we chemically conjugated peptides into the bulk material of the biodegradable elastic polyurethane and showing to promote endothelial cell adhesion and proliferation. (See figure below).

Figure: Endothelial cell adhesion on elastic biodegradable polyurethane without peptide (A) and with peptide conjugated into bulk materials (B) (Prepare for patent). 

2. Synthesizing light-curable elastic hydrogel

Many types of tissue in the body are in the form of hydrogel. Hydrogels are also extensively studied for tissue repair. However, most hydrogels developed are very weak and not strong enough to bear loads. An ideal hydrogel for many tissue repair, such as cartilage, should be elastic, strong, and bioactive. To this end, Dr. Wen’s group has developed several types of biodegradable elastic hydrogels as shown below. In addition, interpenetrating polymer network (IPN) can be formed with bioactive molecules through the light initiated polymerization (Paper in preparation).

Figure: Light-curable elastic biodegradable hydrogels developed in Dr. Wen’s group. Top left: light-initiated polymerization; Top right: porous cylinder scaffolds formed after light-initiated polymerization; Bottom: compression testing data shown high elasticity of hydrated hydrogel scaffold. The elastic region is over 65%.

3. Modifying natural biomaterials for improved properties

Natural biomaterials are very attractive for many types of tissue repair. However, the mechanical properties of those natural polymers, such as collage, hyaluronic acid (hyaluronan), and chitosan, are very weak and lack of elasticity. Therefore, one goal is to chemically modify those natural polymers to improve their mechanical properties. The other goal is to chemically modify the material with certain roles in controlling tissue regeneration. For example, one approach is to chemically modify chitosan for improved blood biocompatibility as shown below.
 
Figure: Platelet adhesion assay. Raw chitosan (A &C) and chemically modified chitosan (B&D). (Paper in preparation)