Antimicrobial loaded polymeric nanoparticles for the treatment of acute respiratory infections

Acute respiratory infections (ARIs) are responsible for 4.25 million deaths annually worldwide (Mayor, 2010). Infections such as bronchitis and pneumonia are commonly treated with antibiotics, making ARI a primary driver for antimicrobial resistance (AMR), and given the rise in antimicrobial-resistant pathogens (O'Neill, 2016), the treatment of ARIs necessitates a pressing need for alternatives to antibiotics. Nitric oxide (NO) is an effective broad-spectrum antimicrobial produced by the immune system in response to invading pathogens. However, its clinical application is hindered by its reactivity and short half-life, making its delivery to the site of infection often challenging. To address this issue, NO donors, such as N-diazeniumdiolates have been developed to improve its stability and shelf life. This NO donor is formed by the reaction of amines with NO gas under high pressure [3], and owing to its ease of fabrication, it is commonly used in biomaterial research. Gelatin nanoparticles (GNP) are used in many drug delivery systems owing to their biocompatibility, biodegradability and FDA approval. Furthermore, as gelatin is a polyamine, it provides multiple binding sites for the tethering of N-diazeniumdiolates. Therefore, we fabricated NO-loaded gelatin nanoparticles (GNP/NO) for the controlled release of NO for the treatment of ARI, and assessed their antimicrobial efficacy, biocompatibility, and NO release kinetics.
A two-step desolvation method was used to synthesise GNP and produced homogenous spherical particles of ~225nm, confirmed by dynamic light scattering (DLS) and scanning electron microscopy (SEM) analysis. The physicochemical properties of the GNP loaded with N-diazeniumdiolates (GNP/NO) were assessed via Fourier-transform infrared spectroscopy (FT-IR), which confirmed the successful functionalisation of the nanoparticles. Chemiluminescence was used to determine the NO payload and release kinetics, demonstrating that GNP/NO released an initial NO burst, followed by a sustained release over 24 h. The antimicrobial efficacy of GNP/NO was tested against a panel of microorganisms, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus and Candida albicans over a 24 h period and revealed a significant reduction (up to 3 log) in viable growth after 4 h and 24 h against all tested microorganisms. Following this, the ISO-10993 indirect (leachate) protocol was used to assess the cytotoxicity of GNP/NO against both the L929 and Detroit 562 cell lines, which showed that GNP/NO maintained over 70% cell viability.
We have demonstrated the successful development of GNP/NO, which exhibits excellent antimicrobial properties within a cytocompatible range, illustrating the potential of GNP/NO as a treatment for ARI. Further investigation is warranted to assess the in vivo effects of GNP/NO before ensuring its feasibility for use as an effective treatment for ARIs.
References
1. Mayor, S., Acute respiratory infections are world's third leading cause of death. BMJ, 2010. 341: p. c6360.
2. O'Neill, J., Tackling drug-resistant infections globally: final report and recommendations. 2016.
3. Coneski, P.N., 'Competitive formation of N-diazeniumdiolates and N-nitrosamines via anerobic reactions with nitric oxide.' Org. Let., 2009. 11(23).