Ternary nanoparticle complex of ciprofloxacin exhibiting sustained release at gastric pH prepared by co-complexation with polyanions and an ionic amphiphile

Abstract Poor bioavailability of the broad spectrum antibiotic ciprofloxacin (CIP) is caused by its narrow absorption window in the stomach. With the aim of prolonging the gastric residence time of CIP, we prepared a ternary nanoparticle complex (nanoplex) of CIP by co-complexation with polyanions (sodium dextran sulfate (DXT)) and an anionic amphiphile (sodium dodecyl sulfate (SDS)). We investigated the effect of the charge ratio of DXT to SDS on the size, zeta potential, CIP payload, and CIP utilization rate of the CIP-DXT-SDS nanoplex and its dissolution characteristics in simulated gastrointestinal fluids. Fourier transform infrared spectroscopy, powder X-ray diffraction, and differential scanning calorimetry analyses showed that the ternary nanoplex was made up of amorphous CIP-DXT and crystalline CIP-SDS complexes. The size of the CIP-DXT-SDS nanoplex prepared at a > 90% CIP utilization rate was 110–290 nm and it had a zeta potential of −16–39 mV, and CIP payload of 47–62%, depending on the charge ratio. At gastric pH, the CIP-DXT-SDS nanoplex prepared with a DXT:SDS charge ratio lower than 80:20 exhibited prolonged CIP release (60% dissolution after 8 h) compared with native CIP (100% dissolution after 1 h) and a binary CIP-DXT nanoplex (80% dissolution after 5 h), which was attributed to its lower solubility. The sustained release characteristics of the CIP-DXT-SDS nanoplex were comparable to those of existing CIP gastroretentive formulations.