We have developed a novel spray gelation-based method to synthesize a new series of magnetically responsive hydrogel nanoparticles for biomedical and drug delivery applications. The method is based on the production of hydrogel nanoparticles from sprayed polymeric microdroplets obtained by an air-jet nebulization process that is immediately followed by gelation in a crosslinking fluid. Oligoguluronate (G-blocks) was prepared through the partial acid hydrolysis of sodium alginate. PEG-grafted chitosan was also synthesized and characterized (FTIR, EA, and DSC). Then, magnetically responsive hydrogel nanoparticles based on alginate and alginate/G-blocks were synthesized via aerosolization followed by either ionotropic gelation or both ionotropic and polyelectrolyte complexation using CaCl₂or PEG-g-chitosan/CaCl₂as crosslinking agents, respectively. Particle size and dynamic swelling were determined using dynamic light scattering (DLS) and microscopy. Surface morphology of the nanoparticles was examined using SEM. The distribution of magnetic cores within the hydrogels nanoparticles was also examined using TEM. In addition, the iron and calcium contents of the particles were estimated using EDS. Spherical magnetic hydrogel nanoparticles with average particle size of 811 ± 162 to 941 ± 2 nm were obtained. This study showed that the developed method is promising for the manufacture of hydrogel nanoparticles, and it represents a relatively simple and potential low-cost system.

Background: Novel methods are necessary to reduce morbidity and mortality of patients suffering from infections withPseudomonas aeruginosa. Being the most common infectious species of thePseudomonasgenus,P. aeruginosais the primary Gram-negative etiology responsible for nosocomial infections. Due to the ubiquity and high adaptability of this species, an effective universal treatment method forP. aeruginosainfection still eludes investigators, despite the extensive research in this area.Results: We report bacterial inhibition by iron-oxide (nominally magnetite) nanoparticles (NPs) alone, having a mean hydrodynamic diameter of ~ 16 nm, as well as alginate-capped iron-oxide NPs. Alginate capping increased the average hydrodynamic diameter to ~ 230 nm. We also investigated alginate-capped iron-oxide NP-drug conjugates, with a practically unchanged hydrodynamic diameter of ~ 232 nm. Susceptibility and minimum inhibitory concentration (MIC) of the NPs, NP-tobramycin conjugates, and tobramycin alone were determined in the PAO1 bacterial colonies. Investigations into susceptibility using the disk diffusion method were done after 3 days of biofilm growth and after 60 days of growth. MIC of all compounds of interest was determined after 60-days of growth, to ensure thorough establishment of biofilm colonies.Conclusions: Positive inhibition is reported for uncapped and alginate-capped iron-oxide NPs, and the corresponding MICs are presented. We report zero susceptibility to iron-oxide NPs capped with polyethylene glycol, suggesting that the capping agent plays a major role in enabling bactericidal ability in of the nanocomposite. Our findings suggest that the alginate-coated nanocomposites investigated in this study have the potential to overcome the bacterial biofilm barrier. Magnetic field application increases the action, likely via enhanced diffusion of the iron-oxide NPs and NP-drug conjugates through mucin and alginate barriers, which are characteristic of cystic-fibrosis respiratory infections. We demonstrate that iron-oxide NPs coated with alginate, as well as alginate-coated magnetite–tobramycin conjugates inhibitP. aeruginosagrowth and biofilm formation in established colonies. We have also determined that susceptibility to tobramycin decreases for longer culture times. However, susceptibility to the iron-oxide NP compounds did not demonstrate any comparable decrease with increasing culture time. These findings imply that iron-oxide NPs are promising lower-cost alternatives to silver NPs in antibacterial coatings, solutions, and drugs, as well as other applications in which microbial abolition or infestation prevention is sought.

Messenger RNA is a class of promising nucleic acid therapeutics to treat a variety of diseases, including genetic diseases. The development of a stable and efficacious mRNA pulmonary delivery system would enable high therapeutic concentrations locally in the lungs to improve efficacy and limit potential toxicities. In this study, we employed a Design of Experiments (DOE) strategy to screen a library of lipid nanoparticle compositions to identify formulations possessing high potency both before and after aerosolization. Lipid nanoparticles (LNPs) showed stable physicochemical properties for at least 14 days of storage at 4 °C, and most formulations exhibited high encapsulation efficiencies greater than 80%. Generally, upon nebulization, LNP formulations showed increased particle size and decreased encapsulation efficiencies. An increasing molar ratio of poly-(ethylene) glycol (PEG)-lipid significantly decreased size but also intracellular protein expression of mRNA. We identified four formulations possessing higher intracellular protein expression ability in vitro even after aerosolization which were then assessed in in vivo studies. It was found that luciferase protein was predominately expressed in the mouse lung for the four lead formulations before and after nebulization. This study demonstrated that LNPs hold promise to be applied for aerosolization-mediated pulmonary mRNA delivery.