Microencapsulation of Liquid Cyanoacrylate via In situ Polymerization for Self-healing Bone Cement Application
- PDF / 1,379,573 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 43 Downloads / 187 Views
Microencapsulation of Liquid Cyanoacrylate via In situ Polymerization for Self-healing Bone Cement Application
Vineela D. Gandham1, Alice B.W. Brochu1,2, William M. Reichert 1, 2 1 Department of Biomedical Engineering, Duke University, Durham, NC 27708-0281, U.S.A 2 Center for Biomolecular and Tissue Engineering, Duke University, Durham, NC 27708-0271, U.S.A
ABSTRACT Structural polymers are susceptible to accumulated damage in the form of internal microcracks that propagate through the material, resulting in mechanical failure. Self- healing approaches offer a solution to repair these damages automatically. The first generation selfhealing material system includes a microencapsulated healing agent within a catalyst-embedded matrix. Propagating microcracks rupture the microcapsules, releasing the liquid healing agent into the damaged region. Catalyst-triggered polymerization of the released healing agent repairs the damage. Our research focuses on a similar approach for addressing “damage accumulation failure” of poly(methyl methacrylate) (PMMA) bone cement caused by microcrack initiation and propagation. In this study, polyurethane (PU) microcapsules containing a tissue adhesive, 2octylcyanoacrylate (OCA) were synthesized using in situ interfacial polymerization of toluene2,4-diisocynate (TDI) and polyethylene glycol 200 (PEG 200) through an oil-in-oil-in-water microemulsion (o/o/w). The process was optimized by studying different combinations of organic solvents, surfactants, temperatures, agitation rates, pH, and reaction times and their effects on microencapsulation were observed. Microcapsule surface morphology, size, shell thickness, encapsulated OCA viability, thermal degradation, and chemical structure of the microcapsule shell were evaluated using a stereoscope, scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and fourier transform infrared spectroscopy (FT-IR).
INTRODUCTION Through the pioneering efforts of Charnley, PMMA bone cement emerged as one of the promising biomaterials in orthopedics [1]. PMMA acts as a space-filler, holding the stem of an artificial joint replacement against the native boney tissue. However, these replacements tend to fail due to aseptic loosening of the construct or through immunological rejections. Jasty et al. have shown that orthopedic implants mostly fail due to the “damage accumulation failure” of the bone cement during which numerous microcracks initiate and propagate, leading to loosening and subsequent failure of the prosthesis [2]. Evidence of damage accumulation and microcrack initiation under dynamic loading in cement mantle was observed by Culleton et al. [3] and Topoleski et al. [4]. Cracks ranging from 40 µm to 2 mm were observed in bone cement mantles retrieved post-mortem. However, only microcracks greater than 300 µm in length were found to have the potential to grow to critical length and cause implant failure [2, 5]. Bone cement is a brittle material with weak tensile and shear strengths, but high compressive strength. The average values
Data Loading...
