(171a) In Vitro Evaluation of Calcium Peroxide Release from Composite Poly(lactic-co-glycolic acid) Microsphere Scaffolds

Ornella Tempo

University of Connecticut, Storrs, CT

Academic Background: Date of Entry: 08/2012

Degrees Expected: B.S

Expected Year of Graduation/ Program Completion:  2016

Major or Field of Study: Chemical Engineering

Academic Level: Undergraduate Student

Institution where the research was conducted

University of Connecticut Health, Institute for Regenerative Medicine

Co-authors:

Keshia Ashe, Ph.D. candidate^3,5; Yusuf Khan, Ph.D. ^2,4,5,6; Cato Laurencin, M.D./Ph.D.^1,2,3,4,5

Co-authors affiliations:

¹Connecticut Institute for Clinical and Translational Science (CICATS)

²Department of Orthopedic Surgery, School of Medicine, University of Connecticut

³Department of Chemical and Biomolecular Engineering, University of Connecticut-Storrs

⁴Department of Materials Science and Engineering, University of Connecticut-Storrs

⁵Institute for Regenerative Engineering, University of Connecticut Health

⁶New England Musculoskeletal Institute

Title: In Vitro Evaluation of Calcium Peroxide Release from Composite Poly(lactic-co-glycolic acid) Microsphere Scaffolds

Category: Materials Science, Polymer Science, Chemical Engineering

Research Sponsor(s): This work was supported by the John and Valerie Rowe Health Professions Scholars Program at the University of Connecticut, Storrs, CT.

Bone tissue engineering is the study of how the intersection of cells, biomaterials, and bioactive factors can restore normal bone function after surgical, degenerative, or traumatic bone loss. The objective of this project was to investigate the potential of a materials-only approach for guided bone regeneration.

Many bone tissue engineering therapies involve the use full-length proteins as bioactive agents. However, calcium-releasing materials have been shown as effective at inducing osteogenesis. In this study, the capabilities of composite poly(lactic-co-glycolic acid) (PLGA) and calcium peroxide (CaO₂) sintered microsphere scaffolds were investigated as an alternative to current bone repair strategies. We hypothesize that the hydrolytic degradation of composite PLGA/CaO₂ 3-dimensional (3D) scaffolds would result in a measurable in vitro release of CaO₂ over 28 days.  

Scaffold Fabrication: 0%, 0.5%, and 1% 85:15 PLGA/CaO₂ microspheres were fabricated via the single emulsion technique. 3D scaffolds were created by sintering loaded microspheres in a 10 x 5 mm cylindrical stainless steel mold.

Calcium Release: The release of Ca²⁺ ions was determined by submerging scaffolds in 1 ml of calcium-free phosphate buffered solution with 500 μL samples taken and replaced at 1, 2, 4, 8 and 12 hours, and 1, 2, 3, 4, 5, 6, 7, 9, 11, 13, 15, 17, 19, 21 and 28 days. Quantities of Ca²⁺ were measured using the Calcium (CPC) Liquicolor kit. Scaffold Imaging: Composite microspheres were analyzed qualitatively for surface integrity using a scanning electron microscope (SEM).     

We report that the calcium release for 0.5% and 1% PLGA/CaO₂ increased in a time-dependent manner. However, 1% PLGA/CaO₂ scaffolds released a significantly greater amount of calcium ions over time. As expected, there was no calcium release for 0% scaffolds. The in vitro release kinetics reveal the structure-function relationship between the materials, which can serve as a correlation to in vivo release. Furthermore, SEM images suggest that in comparison to pristine scaffolds, CaO₂ loading did not cause morphological changes on the microsphere surfaces. For future studies, we predicted that the observed calcium release could influence the osteogenic differentiation of stem cells without other supplemental factors, as noted in recent studies.