High-throughput methods for screening liposome-macrophage cell interaction.

Carriers are often an essential element of drug delivery, bestowing attributes to their cargo such as biocompatibility, enhanced delivery, extended half-life and efficacy as well as mediating specific targeting at a tissue, cell or intracellular level. Liposomes and lipid-based carriers have been investigated for decades for this purpose, many achieving clinical approval including products such as Doxil® and Myocet™. Large-scale compound screens are routinely carried out in the field of drug discovery; however, less work has been done on harnessing high-throughput methods for carrier material screening. Screening the interaction of drug carriers and materials with cells is particularly critical for the development of emerging therapies, including biomedicines, in order to facilitate the development of safe and efficient drug products. Herein, a range of liposomes of neutral, anionic and cationic charge and others that are surface-modified with mannose residues were screened for cell interaction, toxicity and immune reactivity in THP-1-derived macrophages using a high-throughput format. Liposomes were seen to be efficacious in a concentration-dependent and, for mannosylated liposomes, mannosylated cholesterol linker length-dependent manner.

Therapeutic aerosol bioengineering of siRNA for the treatment of inflammatory lung disease by TNFα gene silencing in macrophages.

The development of small interfering RNA (siRNA) to silence specific genes offers a new means of understanding and treating a range of respiratory diseases, including inflammatory lung disease. The alveolar macrophage (AM) is a key component of the inflammatory process in the lungs, associated with high levels of gene expression in inflammatory lung disease and therefore an attractive target for therapeutic siRNA. Delivery of siRNA to macrophages presents a significant delivery challenge, as fully differentiated alveolar macrophages are difficult to access and transfect. In this study we engineered particles suitable for inhalation that would efficiently transfect macrophages postinhalation. The process for encapsulation of siRNA in poly(lactic-co-glycolic acid) microparticles (MPs) was optimized using a double emulsion technique, and the resulting particles were characterized for size, shape, aerosol characteristics, encapsulation efficiency, and integrity of encapsulated siRNA. The cell uptake of the siRNA-loaded microparticles was determined by flow cytometry, confocal laser scanning microscopy (CLSM), and high-content analysis (HCA) with MPs capable of transfecting up to 55% of cells. Anti-TNFα siRNA-MPs were then prepared to study the functional activity of encapsulated siRNA in LPS-stimulated macrophages as a model of inflammation. The anti-TNFα siRNA-MPs were able to decrease TNFα expression by 45% over 48 h in the differentiated human monocytic cell line THP-1 compared to negligible knockdown using commercial transfection reagents and offered significant, sustained siRNA knockdown of TNFα in primary monocytes for up to 72 h.

The application of high-content analysis in the study of targeted particulate delivery systems for intracellular drug delivery to alveolar macrophages.

With an ever increasing number of particulate drug delivery systems being developed for the intracellular delivery of therapeutics a robust high-throughput method for studying particle-cell interactions is urgently required. Current methods used for analyzing particle-cell interaction include spectrofluorimetry, flow cytometry, and fluorescence/confocal microscopy, but these methods are not high throughput and provide only limited data on the specific number of particles delivered intracellularly to the target cell. The work herein presents an automated high-throughput method to analyze microparticulate drug delivery system (DDS) uptake byalveolar macrophages. Poly(lactic-co-glycolic acid) (PLGA) microparticles were prepared in a range of sizes using a solvent evaporation method. A human monocyte cell line (THP-1) was differentiated into macrophage like cells using phorbol 12-myristate 13-acetate (PMA), and cells were treated with microparticles for 1 h and studied using confocal laser scanning microscopy (CLSM), spectrofluorimetry and a high-content analysis (HCA). PLGA microparticles within the size range of 0.8-2.1 µm were found to be optimal for macrophage targeting (p < 0.05). Uptake studies carried out at 37 °C and 4 °C indicated that microparticles were internalized in an energy dependent manner. To improve particle uptake, a range of opsonic coatings were assessed. Coating PLGA particles with gelatin and ovalbumin was found to significantly increase particle uptake from 2.75 ± 0.98 particles per cell for particles coated with gelatin. Opsonic coating also significantly increased particle internalization into primary human alveolar macrophages (p < 0.01) with a 1.7-fold increase in uptake from 4.19 ± 0.48 for uncoated to 7.53 ± 0.88 particles per cell for coated particles. In comparison to techniques such as spectrofluorimetry and CLSM, HCA provides both qualitative and quantitative data on the influence of carrier design on cell targeting that can be gathered in a high-throughput format and therefore has great potential in the screening of intracellularly targeted DDS.

Treatment of Mycobacterium tuberculosis-Infected Macrophages with Poly(Lactic-Co-Glycolic Acid) Microparticles Drives NFκB and Autophagy Dependent Bacillary Killing.

The emergence of multiple-drug-resistant tuberculosis (MDR-TB) has pushed our available repertoire of anti-TB therapies to the limit of effectiveness. This has increased the urgency to develop novel treatment modalities, and inhalable microparticle (MP) formulations are a promising option to target the site of infection. We have engineered poly(lactic-co-glycolic acid) (PLGA) MPs which can carry a payload of anti-TB agents, and are successfully taken up by human alveolar macrophages. Even without a drug cargo, MPs can be potent immunogens; yet little is known about how they influence macrophage function in the setting of Mycobacterium tuberculosis (Mtb) infection. To address this issue we infected THP-1 macrophages with Mtb H37Ra or H37Rv and treated with MPs. In controlled experiments we saw a reproducible reduction in bacillary viability when THP-1 macrophages were treated with drug-free MPs. NFκB activity was increased in MP-treated macrophages, although cytokine secretion was unaltered. Confocal microscopy of immortalized murine bone marrow-derived macrophages expressing GFP-tagged LC3 demonstrated induction of autophagy. Inhibition of caspases did not influence the MP-induced restriction of bacillary growth, however, blockade of NFκB or autophagy with pharmacological inhibitors reversed this MP effect on macrophage function. These data support harnessing inhaled PLGA MP-drug delivery systems as an immunotherapeutic in addition to serving as a vehicle for targeted drug delivery. Such "added value" could be exploited in the generation of inhaled vaccines as well as inhaled MDR-TB therapeutics when used as an adjunct to existing treatments.