Musculoskeletal heterogenous tissues are crucial for dissipating mechanical load during physical activity. Modern procedures to repair these tissues have proven inadequate to restore full functionality, thus there is a need for alternative reconstructive methods. Consequently, tissue engineered scaffolds can mimic the native structure of tissues and trigger a healing response. Heterogenous tissues like the tendon-bone junction consist of an interdigitated fiber alignment gradient from the tendon to the bone. It has been shown that electrospun fiber alignment gradients can be fabricated from the incorporation of magnetic fields. In this study, manipulating electrostatic and magnetic interactions from various electrospinning collector arrangements were investigated for creating an interdigitated fiber alignment gradient. The collector arrangement consisting of a magnet overlaid with razor cut aluminum foil proved to provide increased control over the interfacial shape. The rapid transition at the interfacial region was verified with brightfield microscopy revealing an interdigitated gradient from highly aligned fibers to unaligned fibers.

The tendon-bone junction is essential for allowing humans to transfer mechanical loads during activities. When injury does occur to this important area, current surgical techniques improperly bypass important physical and chemical gradients and do not restore proper function. It is essential to create tissue engineered scaffolds that create proper models for the region and induce healing responses for repair. To advance research into these scaffolds, electrospinning fibers and hydrogels made of norbornene functionalized hyaluronic acid (NorHA) were used to promote bone growth by adhering calcium to the material. To further improve calcium adherence, which is indicative of bone regions, a mineralization peptide was allowed to soak through the fibers. NorHA proved to be a suitable material for biomineralization experiments, showing slow calcium adherence within the first hour before accelerating in adherence over 24 hours in both fibers and hydrogels. When the mineralization peptide was implemented calcium adherence on fibers increased nearly eight times within the first 15 minutes of experimentation.

The tendon-bone junction, also known as the enthesis, is crucial for properly transferring mechanical loadings during physical activity. During injury, current restoration procedures are insufficient for properly restoring tissue function. Thus, it is paramount to design alternative tissue engineered scaffolds to act as a template to the injured region and a regenerative response for tendon-bone repair. Thus, we utilized an offset electrospinning technique to fabricate a scaffold that mimics the native biochemical gradients present within the tendon-bone junction. To improve chemical gradient resolution, we implemented both insulating and conductive shields during offset electrospinning. Polycaprolactone fibers with either rhodamine or fluorescein were used to measure the scaffold fluorescent strength with distance. Without shields, at an offset of 4 cm, the chemical gradient resolution for rhodamine and fluorescein were 2.5 cm and 6.0 cm, respectively. During implementation of insulating shields, the gradient resolution for rhodamine and fluorescein improved to 2 cm and 0.5 cm, respectively. Lastly, grounded conductive shields improved gradient resolution for rhodamine and fluorescein to 1.0 cm and 1.5 cm, respectively.