Loading and Releasing Ciprofloxacin in Photoactivatable Liposomes
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We demonstrate that ciprofloxacin can be actively loaded into liposomes that contain small amounts of porphyrin-phospholipid (PoP). PoP renders the liposomes photoactivatable, so that the antibiotic is released from the carrier under red light irradiation. The liposome formulation was optimized for ciprofloxacin loading, storage stability, and rapid light-triggered drug release. Use of 2 molar % PoP liposomes allowed maximum active loading of Ciprofloxacin. Inclusion of 2 molar % of an unsaturated phospholipid further accelerated light-triggered drug release (more than 90% in less than 30 seconds). With or without laser treatment, ciprofloxacin PoP liposomes inhibited the growth of Bacillus subtilis in liquid media, apparently due to uptake of the liposomes by the bacteria. However, when liposomes were first separated from smaller molecules with centrifugal filtration, only the filtrate from laser-treated liposomes was bactericidal, demonstrating effective release of intact antibiotic. These results establish the feasibility of actively loading antibiotics into photoactivatable liposomes, which could create new possibilities for enhanced localized antibiotic therapy.