Seeing is believing but quantifying is deciding

Progressive use of multispectral imaging flow cytometry in various research areas

Multi-spectral imaging flow cytometry (MIFC) has become one of the most powerful technologies for investigating general analytics, molecular and cell biology, biotechnology, medicine, and related fields. It combines the capabilities of the morphometric and photometric analysis of single cells and micrometer-sized particles in flux with regard to thousands of events. It has become the tool of choice for a wide range of research and clinical applications. By combining the features of flow cytometry and fluorescence microscopy, it offers researchers the ability to couple the spatial resolution of multicolour images of cells and organelles with the simultaneous analysis of a large number of events in a single system. This provides the opportunity to visually confirm findings and collect novel data that would otherwise be more difficult to obtain. This has led many researchers to design innovative assays to gain new insight into important research questions. To date, it has been successfully used to study cell morphology, surface and nuclear protein co-localization, protein-protein interactions, cell signaling, cell cycle, cell death, and cytotoxicity, intracellular calcium, drug uptake, pathogen internalization, and other applications. Herein we describe some of the recent advances in the field of multiparametric imaging flow cytometry methods in various research areas.

Microfluidic-based platform to mimic the in vivo peripheral administration of neurotropic nanoparticles

Aim: Propose a nanoparticle for neuron-targeted retrograde gene delivery and describe a microfluidic-based culture system to provide insight into vector performance and safety. Methods: Using compartmentalized neuron cultures we dissected nanoparticle bioactivity upon delivery taking advantage of (quantitative) bioimaging tools. Results: Targeted and nontargeted nanoparticles were internalized at axon terminals and retrogradely transported to cell bodies at similar average velocities but the former have shown an axonal flux 2.7-times superior to nontargeted nanoparticles, suggesting an improved cargo-transportation efficiency. The peripheral administration of nanoparticles to axon terminals is nontoxic as compared with their direct administration to the cell body or whole neuron. Conclusion: A neuron-targeted nanoparticle system was put forward. Microfluidic-based neuron cultures are proposed as a powerful tool to investigate nanoparticle bio-performance.

A high-throughput bioimaging study to assess the impact of chitosan-based nanoparticle degradation on DNA delivery performance

By using imaging flow cytometry as a powerful statistical high-throughput technique we investigated the impact of degradation on the biological performance of trimethyl chitosan (TMC)-based nanoparticles (NPs). In order to achieve high transfection efficiencies, a precise balance between NP stability and degradation must occur. We altered the biodegradation rate of the TMC NPs by varying the degree of acetylation (DA) of the polymer (DA ranged from 4 to 21%), giving rise to NPs with different enzymatic degradation profiles. While this parameter did not affect NP size, charge or ability to protect plasmid DNA, NPs based on TMC with an intermediate DA (16%) showed the highest transfection efficiency. Subsequently, by means of a single quantitative technique, we were able to follow, for each tested formulation, major steps of the NP-mediated gene delivery process - NP cell membrane association, internalization and intracellular trafficking, including plasmid DNA transport towards the nucleus. NP cytotoxicity was also possible to determine by quantification of cell apoptosis. Overall, the obtained data revealed that the biodegradation rate of these NPs affects their intracellular trafficking and, consequently, their efficiency to transfect cells. Thus, one can use the polymer DA to modulate the NPs towards attaining different degradation rates and tune their bioactivity according to the desired application. Furthermore, this novel technical approach revealed to be a valuable tool for the initial steps of nucleic acid vector design.

STATEMENT OF SIGNIFICANCE

By changing the biodegradation rate of trimethyl chitosan-based nanoparticles (NPs) one was able to alter the NP ability to protect or efficiently release DNA and consequently, to modulate their intracellular dynamics. To address the influence of NP degradation rate in their transfection efficiency we took advantage of imaging flow cytometry, a high-throughput bioimaging technique, to unravel some critical aspects about NP formulation such as the distinction between internalized versus cell-associated/adsorbed NP, and even explore NP intracellular localization. Overall, our work provides novel information about the importance of vector degradation rate for gene delivery into cells, as a way to tune gene expression as a function of the desired application, and advances novel approaches to optimize nanoparticle formulation.