title: Effect of calcium phosphate particle shape and size on their antibacterial and osteogenic activity in the delivery of antibiotics in vitro.
abstract: Powders composed of four morphologically different calcium phosphate particles were prepared by precipitation from aqueous solutions: flaky, brick-like, elongated orthogonal, and spherical. The particles were then loaded with either clindamycin phosphate as the antibiotic of choice or fluorescein, a model molecule used to assess the drug release properties. A comparison was carried out of the effect of such antibiotic-releasing materials on: sustained drug release profiles; Staphylococcus aureus growth inhibition; and osteogenic propensities in vitro. Raman spectroscopic analysis indicated the presence of various calcium phosphate phases, including monetite (flaky and elongated orthogonal particles), octacalcium phosphate (brick-shaped particles), and hydroxyapatite (spherical particles). Testing the antibiotic-loaded calcium phosphate powders for bacterial growth inhibition demonstrated satisfying antibacterial properties both in broths and on agar plates. All four calcium-phosphate-fluorescein powders exhibited sustained drug release over 21 days. The calcium phosphate sample with the highest specific surface area and the smallest, spherical particle size was the most effective in both drug loading and release, consequently having the highest antibacterial efficiency. Moreover, the highest cell viability, the largest gene expression upregulation of three different osteogenic markers--osteocalcin, osteopontin, and Runx2--as well as the least disrupted cell cytoskeleton and cell morphologies were also noticed for the calcium phosphate powder composed of the smallest, spherical nanosized particles. Still, all four powders exerted a viable effect on osteoblastic MC3T3-E1 cells in vitro, as evidenced by both morphological assessments on fluorescently stained cells and measurements of their mitochondrial activity. The obtained results suggest that the nanoscale particle size and the corresponding coarseness of the surface of particle conglomerates as the cell attachment points may present a favorable starting point for the development of calcium-phosphate-based osteogenic drug delivery devices.
authors.affiliation: Therapeutic Micro and Nanotechnology Laboratory, Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, California 94158-2330, United States. vuk21@yahoo.com
authors.forename: Vuk
authors.initials: V
authors.lastname: Uskoković
authors.forename: Samir Shariff
authors.initials: SS
authors.lastname: Batarni
authors.forename: Julien
authors.initials: J
authors.lastname: Schweicher
authors.forename: Andrew
authors.initials: A
authors.lastname: King
authors.forename: Tejal A
authors.initials: TA
authors.lastname: Desai
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D002130:Calcium Phosphates / Q000737:chemistry*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D002981:Clindamycin / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D050659:Core Binding Factor Alpha 1 Subunit / Q000378:metabolism; D003599:Cytoskeleton / Q000187:drug effects; D003692:Delayed-Action Preparations / Q000138:chemical synthesis / Q000737:chemistry*; D017886:Durapatite / Q000737:chemistry; D051379:Mice; D008826:Microbial Sensitivity Tests; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D015675:Osteocalcin / Q000378:metabolism; D010012:Osteogenesis / Q000187:drug effects; D053495:Osteopontin / Q000378:metabolism; D010316:Particle Size; D013211:Staphylococcus aureus / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D002130:Calcium Phosphates; D050659:Core Binding Factor Alpha 1 Subunit; D003692:Delayed-Action Preparations; D015675:Osteocalcin; D053495:Osteopontin; C022045:octacalcium phosphate; D002981:Clindamycin; D017886:Durapatite; C020243:calcium phosphate; C007084:clindamycin phosphate