Tetracycline-loaded calcium phosphate nanoparticle (Tet-CPNP): Rejuvenation of an obsolete antibiotic to further action

Background: Increasing resistance in bacteria towards antibiotics has made it imperative to research on their revitalization to combat infectious diseases. This study dealt with synthesis of a nano-form of the antibiotic tetracycline, its characterization and potency of killing different multi-drug resistant diarrhea-causing bacteria. Methods: Nano-formulation was done by loading tetracycline within biocompatible calcium phosphate nanoparticle. The synthesized tetracycline-loaded calcium phosphate nanoparticle (Tet-CPNP) was characterized by the techniques like TEM, DLS, EDS, FTIR, spectrofluorimetry and dialysis. Bactericidal activity of nano-particulate tetracycline was investigated by agar plating, spectrophotometry, phase contrast-fluorescence-atomic force microscopy and flow cytometry techniques. Results: The Tet-CPNPs were 8 +/- 5 nm in size and nearly spherical in shape, efficiency of tetracycline loading in CPNP was about 20% and the release of antibiotic from Tet-CPNPs was sustainable during 7 days. Minimum inhibitory concentration (MIC) of Tet-CPNP on multiple antibiotic (including tetracycline) resistant bacteria like Escherichia coli, Salmonella kentuckey and Shigella flexneri was in the range of 20-40 mu g/ml, whereas MIC of free tetracycline was in the range of 150-180 mu g/ml. NP-mediated cell filamentation and cell membrane disintegration caused cell killing. Moreover, death of Shigella-infected Zebra fish larvae was stalled by Tet-CPNP treatment. CPNP itself had no toxic effect on bacteria as well as on Zebra fish. Conclusion: Our nano-formulation of tetracycline might reclaim a nearly obsolete antibiotic to further potential function. General significance: Such a study on revival of an old, cheap, broad-spectrum antibiotic to further action is highly beneficial to developing countries with limited health care budgets. (C) 2016 Elsevier B.V. All rights reserved.