Self-assembled particles, based on non-covalent interactions, are attractive drug carriers with a relatively simple structure and easy preparation. Tannic acid (TA) is an anionic polyphenolic compound with a wide range of molecular interactions and diverse applications in drug delivery research. Here, we propose the use of TA complexes with cationic antibiotics as a new pH-responsive drug carrier of high drug loading and optimal stability. TA complexes were prepared with three water-soluble antibiotics; colistin sulfate (COL), gentamicin sulfate (GEN) and gatifloxacin (GAT). Complexes’ size ranged from several-hundred nanometers to few microns. For selected particles, drug loading ranged from 30 to 36%. Importantly, we demonstrate the impact of drug-carrier interactions, studied via infrared spectroscopy and molecular modeling, on final complex stability and performance; the complexes resisted dissociation in presence of serum at physiological pH to variable degrees and showed different drug release profiles. However, all complexes dissociated upon medium acidification, releasing their drug payload and demonstrating expected antibacterial effect. These results demonstrate that TA/antibiotic self-assembled complexes represent an excellent carrier for pH-sensitive delivery of water-soluble drugs. In addition to system’s simplicity and low cost, complexes were easily prepared with high drug loading and desirable pH-dependent association/dissociation profile.

We developed a digital microfluidics platform for preparation of poly(lactic-co-glycolic) acid (PLGA) Nanoparticles (NPs). Droplets of PLGA in dimethylformamide were merged with droplets of deionized water by electrical actuation on a digital microfluidics device to form PLGA nanoparticles through nanoprecipitation. The platform we developed is automated and allows for preparation of polymeric NPs with small size and high uniformity. Using our platform, we were able to prepare monodisperse PLGA NPs as small as 115 nm with a polydispersity index (PDI) of 0.14 which can be challenging with conventional preparation techniques on the macroscale. Size of the prepared NPs can be tuned through proper choice of the volume ratio between the two merged droplets which controls the induced internal convection flow after merging. Concentration of PLGA in the dimethylformamide droplet also had an effect on the size and polydispersity of the formed nanoparticles. We believe our results prove the potential use of digital microfluidics for testing combinatorial synthesis of different polymeric NPs for various applications. This approach allows robust and automated screening of NP preparations using only few microliters of the reagents used, thus conserving precious and costly NP components and loaded therapeutic agents.

H521-H526

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