Ma Lab - research
current research
MOLECULAR TAILORING OF HIGH PERFORMANCE ELECTRO ACTIVE APOLYMERS
Smart materials and their applications in robots and unmanned vehicles are critically important to NASA's mission of exploration of space and the utilization of the space environment and technologies for the benefits of mankind. For applications in space missions, low mass and high performances are particularly important. Therefore electro active polymers, such as electromechanical actuation and sensing polymers, are attractive for aerospace applications.

Various crystalline fluorine-containing polymers (fluorohydocarbons) are excellent materials because of their characteristic properties such as exceptional chemical resistance, high temperature resistance, and weathering and ozone resistance particular interest to this proposed research project are their sensing and electro- mechanical properties. To achieve desired elasticity and electroactive properties, we propose to design and tailor molecular structure of fluorinecontaining graft copolymers: an elastomeric backbone polymer to provide the high elasticity and crystallizable graft chains to fornl crystallites as physical crosslinks and reinforcing second phase.

Fluorine-containing graft copolymers will be prepared in two steps. In the first step, an elastomeric base polymer is prepared by random copolymerization of two different fluorinecontaining monomers and unsaturated peroxide at low temperature. The branched unsaturated peroxide in the copolymer acts as an initiator in the second graft polymerization. In the second step, a crystallizable polymer chain is grafted onto the base copolymer at a relatively high temperature. We will tailor the molecular structure of the graft copolymers and characterize their structural composition, thermal and mechanical properties. The processing and evaluations of electromechanical performance will be conducted at the NASA Langley Research Center by the sponsor, Through this collaborative research, we aim to develop ideal electromechanical performance of the graft copolymer system for actuation and sensing applications.

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BIOMIMETIC NANOSCAFFOLDS
Repair of tooth-supporting structures destroyed by the chronic inflammatory disease-peridontitis is a major goal of oral reconstructive therapy. We propose to develop a novel scaffolding system that can also deliver regenerative agents to periodontal defects. This system consists of a nano-fibrous polymer scaffold modified with bone mineral- mimicking apatite that contains microspheres for delivery of bioactive molecules such as bone morphogenetic protein- 7 (BMP- 7), to periodontal defects. It is expected that this scaffolding/factor delivery system will promote periodontal regeneration at the defect site by providing an environment for enhancing adhesion and migration of putative cells such as osteoblasts, cementoblasts, and periodontal ligament (PDL) fibroblasts as well as promoting differentiation of their progenitor cells. Moreover, this scaffolding delivery system will allow for permeation of nutrients, metabolites, and signaling molecules required for cell proliferation, differentiation and three dimensional I(3D) tissue formation. This exploratory research project will focus on development of the scaffolding/factor delivery system and on testing the feasibility of this novel system for use in treatment of periodontal defects. The following specific aims are designed to generate preliminary data to determine the strength of this approach for periodontal tissue engineering.

  • Specific Aim 1. Design nano fibrous scaffolds with interconnected spherical macropores and modified with bone mineral-like apatite.
  • Specific Aim 2. Integrate microspheres containing BMP- 7 into nano fibrous scaffolds and evaluate the bioactivity and release kinetics of BMP- 7 in vitro.

Accomplishing these specific aims will generate critical preliminary data and provide vital information as to the appropriate scaffolding/factor delivery system for-use in designing optimal periodontal regenerative therapies. This knowledge will enable us to develop a predictable biomimetic scaffold for in vivo application and will be the basis for our planned RO 1 investigation.

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PERIODONTAL ENGINEERING USING BIOMIMETIC NANO SCAFFOLDS
Periodontal diseases result in loss of supporting tissues including bone, cementum, and periodontal ligament (PDL), ultimately leading to tooth loss if left untreated. Unfortunately, dental tissue loss has the second largest patient population next to blood transfusion. The restorative results of the current therapies are often disappointing and unpredictable. We propose a novel biomimetic/tissue engineering approach. In this approach an unique nano-fibrous polymer scaffolding (mimicking collagen architecture), modified with apatite (mimicking bone mineral), and containing microspheres for delivery of bioactive factors (mimicking development and reparative signaling cascades) will be used in periodontal osseous defects to: promote activities of cells at the healing site, e.g., osteoblasts, cementoblasts, and PDL fibroblasts (and their progenitor cells),. allow for nutrients, metabolites, and signal molecules to permeate,. and guide cell proliferation, differentiation and tissue neogenesis in 3D.

The Specific Aims of the Project are:

  • 1. To test whether polymer scaffolds with nano-fibrous pore walls are superior to scaffolds with "solid" pore walls, and whether bone mineral-mimic apatite promotes calcified tissue formation, in vitro.
  • 2. To develop a combined nano-fibrous scaffold/biodegradable microsphere delivery system that allows for controlled release and improve bioavailability of putative periodontal regenerative factors and to evaluate their regenerative function, in vitro.
  • 3. To confirm that the microsphere/scaffold systems selected based on the results from studies under aims 1 and 2, provide a superior environment for regeneration of periodontal tissues, in vivo.

By accomplishing these specific aims, our understanding of design principles to use for developing an "ideal" modality for restoring tissues destroyed by periodontal diseases will be significantly advanced, resulting in new and improved periodontal regenerative therapies. Furthermore, our ability to manipulate the scaffolding structure and control the rate and types of factors delivered, this system can be utilized to answer many fundamental questions in regenerative biology, including other tissue engineering applications.

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