Microfluidics fabrication of nanohydrogels for drug-delivery – A short review

The authors describe the use of microfluidics for the formation of nanohydrogels made for drug-delivery application. This study is described in the article: “Hyaluronic acid based nanohydrogels fabricated by microfluidics for the potential targeted release of Imatinib: Characterization and preliminary evaluation of the antiangiogenic effect” by Flavia Bongiovì, Calogero Fiorica, Fabio Salvatore Palumbo, Giovanna Pitarresi and Gaetano Giammona, and published in the International Journal of Pharmaceutics.

Abstract – Microfluidics Fabrication of Nanohydrogels for drug-delivery

Nanoparticle drug delivery systems have the potential to considerably improve the efficacy of disease treatment by increasing site-specific drug concentrations and addressing the low solubility, low specificity, and rapid clearance of small molecule drugs. Tightly controlled and predictable nanoparticle size, dispersity and drug loading profiles are crucial for pharmacokinetic/ pharmacodynamic efficacy. However, fabricating complex nanoparticles with the necessary, high-level reproducibly is not trivial. This study describes a microfluidics approach to produce nanohydrogels loaded with a drug in a controlled, reproducible and effective way based on the high-precision regulation of flow rates and flow ratios. The authors demonstrate cellular uptake of drug-loaded nanohydrogels, the release of drug over time, and assess the potential therapeutic effect on cells.
You can also learn how to synthesize PLGA nanoparticles for drug delivery using a microfluidic platform in this application note.

Introduction – Microfluidics fabrication of nanohydrogels for drug-delivery

A major therapeutic challenge for treating chronic diseases is to ensure the on-target delivery and sustained release of drugs in order to evade the natural rapid clearance of small molecules from the body and development of multidrug resistance.¹ Nanoparticle drug-loaded delivery systems are a promising strategy to increase drug retention time in tissues and to control the rate of drug release, increasing the efficacy of treatments and minimising the dosing frequency required.² These carriers act as “trojan horse” shields for encapsulated drugs and can also be functionalised on their surface to target nanoparticles to specific tissues.

Nanoparticle therapies are typically classified as 100 nm or less in diameter due to their intended delivery route via microcapillary circulation, but can refer to larger particles. Particles of diameter 200-500 nm can diffuse freely through the vitreous gel of the eye,³ and remain a feasible size for drug delivery formulations in this case. Tight control over nanoparticle size distribution and drug loading during formulation is necessary for consistent drug release profiles and clinical reliability.⁴ Traditional batch preparation methods, relying on vigorous agitation and nanoprecipitation, do not sufficiently control the size or dispersity of particles formed.⁵

Microfluidic technologies are uniquely suited to nanoformulation due to their ability to finely control the flow rate and flow ratio of microliter volumes through channels of micrometer dimensions. Microfluidic chips suitable for nanoparticle formation are available in different geometries, including T-junctions, capillary tubes, hydrodynamic flow focussing, herringbone and other micromixer chips.^5,6 The result is high control over spatial separation, reaction time, nanoparticle mixing and precipitation, including more uniform size distribution and improved control of drug loading.

Aim & Objectives

• To produce drug-loaded nanohydrogels with microfluidics.
• To test the uptake of drug-loaded nanohydrogels into cells & assess drug release.
• To investigate drug efficacy (potential anti-angiogenic effect on cells).

In this video, the focused HAxs-EDA-C18-alexafluor 480 flux (in green) is split fluxing into the herringbone channels, then recombined into the large channels. Courtesy of Fabio Salvatore Palumbo.

Key findings

Hyaluronic acid (HA) was used as the carrier due to its abundance in vitreous gel and its many reactive groups suitable for functionalization (e.g. in this study, with RGD motifs for targeting cell-surface integrins). The authors synthesized a new HA derivative sensitive to ionic strength and exploited its propensity to coacervate upon the addition of salt during microfluidic mixing to produce nanoparticles.

This study employed a split-and-recombine micromixer chip connected to Elveflow’s OB1 pressure-driven flow controller and flow sensor to precisely control the flow rates and flow ratios of the different solutions in the chip. Nanohydrogel particles of 150-450 nm diameter with low polydispersity were formed depending on the flow ratio of polymer to salt solution used (ratios between 0.05-0.5 were tested during optimization).⁷

In comparison, fabrication using a traditional batch method showed higher particle size and distribution.⁷ Using a flow ratio of polymer to salt of 0.1 the polydispersity of nanohydrogels produced was low and tightly regulated (Fig 2.).

Precise microfluidic mixing of a solution of functionalised carrier plus Imantinib with a solution of salt (using a flow ratio of 0.1) resulted in the formation of nanohydrogels with a reproducible drug loading of 9 % (w/w). A delayed release profile from nanohydrogels over 48 h was observed for the drug compared to free drug in solution, indicating suitability of the delivery system prepared by microfluidics for drug delivery applications.

Drug-loaded nanohydrogels were tested for their effect on cells in culture. Mitochondrial activity assays demonstrated that nanohydrogels with or without drug were not cytotoxic to HUVEC or HRPEpiC cells, and tracking of a fluorescent tag showed substantial uptake of the carrier into cells. The anti-angiogenic potential of released Imantinib was further suggested by observations of inhibited cell tube organisation and stability, indicative of disrupted endothelial cell orientation, migration and sprouting.

In summary, the authors used accurate pressure-driven flow controlled microfluidics to deploy a platform to reproducibly formulate nanohydrogels with requisite size and low polydispersity, as well as consistent drug loading for predictable release, as required for drug delivery systems.

You can also check our lipid nanoparticle synthesis Beta Pack that uses a herringbone micromixer.

References