Microfluidics in nanoparticle drug delivery; From synthesis to pre-clinical screening

Evaluating Nanoparticles in Preclinical Research Using Microfluidic Systems

Nanoparticles (NPs) have found a wide range of applications in clinical therapeutic and diagnostic fields. However, currently most NPs are still in the preclinical evaluation phase with few approved for clinical use. Microfluidic systems can simulate dynamic fluid flows, chemical gradients, partitioning of multi-organs as well as local microenvironment controls, offering an efficient and cost-effective opportunity to fast screen NPs in physiologically relevant conditions. Here, in this review, we are focusing on summarizing key microfluidic platforms promising to mimic in vivo situations and test the performance of fabricated nanoparticles. Firstly, we summarize the key evaluation parameters of NPs which can affect their delivery efficacy, followed by highlighting the importance of microfluidic-based NP evaluation. Next, we will summarize main microfluidic systems effective in evaluating NP haemocompatibility, transport, uptake and toxicity, targeted accumulation and general efficacy respectively, and discuss the future directions for NP evaluation in microfluidic systems. The combination of nanoparticles and microfluidic technologies could greatly facilitate the development of drug delivery strategies and provide novel treatments and diagnostic techniques for clinically challenging diseases.

A hydrodynamic flow focusing microfluidic device for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride

Cubosomes and hexosomes are emerging platforms for drug and nutraceutical delivery applications. In addition to common high- and low-energy batch emulsification methods for the preparation of these nano-self-assemblies, it is important to introduce suitable microfluidic devices with a precision control of the flow parameters for their continuous production. Microfluidics has several advantages including cost effectiveness, short-production time, and control of the nanoparticle size and size distribution. In the present study, a hydrodynamic flow focusing polyimide microfluidic device was employed for the continuous production of hexosomes based on docosahexaenoic acid monoglyceride (MAG-DHA), in the presence of the stabilizer Pluronic F127. The size, structural, morphological and size characterizations of the continuously produced MAG-DHA nanodispersions were investigated through an integrated approach involving synchrotron small angle X-ray scattering, dynamic light scattering, and cryogenic transmission electron microscopy. We report on a simple process for the microfluidic synthesis of hexosomes with sizes ranging from 108 to 138 nm and relatively narrow size distributions as the polydispersity indices were in the range of 0.14-0.22. At the applied total volumetric flow rates (TFRs) ranging of 50-150 μL min^-1 and flow rate ratios (FRRs) of 10-30, it was evident from SAXS findings that ethanol has only a slight effect on the lattice parameter of the internal inverse hexagonal (H₂) phase of the produced hexosomes. In addition to hexosomes, cryo-TEM observations indicated the coexistence of vesicular structures and smaller nano-objects. The formation of these nano-objects that are most likely normal micelles was also confirmed by SAXS, particularly on increasing FRR from 10 to 20 or 30 at TFR of 150 μL min^-1. Taking into account the reported positive health effects of MAG-DHA, which is a long-chain omega-3 (ω-3) polyunsaturated fatty acid (PUFA) monoglyceride, in various disorders including cancer, the produced hexosomes are attractive for the delivery of ω-3 PUFAs, drugs, nutraceuticals, and their combinations.

3D Microfluidic Bone Tumor Microenvironment Comprised of Hydroxyapatite/Fibrin Composite

Bone is one of the most common sites of cancer metastasis, as its fertile microenvironment attracts tumor cells. The unique mechanical properties of bone extracellular matrix (ECM), mainly composed of hydroxyapatite (HA) affect a number of cellular responses in the tumor microenvironment (TME) such as proliferation, migration, viability, and morphology, as well as angiogenic activity, which is related to bone metastasis. In this study, we engineered a bone-mimetic microenvironment to investigate the interactions between the TME and HA using a microfluidic platform designed for culturing tumor cells in 3D bone-mimetic composite of HA and fibrin. We developed a bone metastasis TME model from colorectal cancer (SW620) and gastric cancer (MKN74) cells, which has very poor prognosis but rarely been investigated. The microfluidic platform enabled straightforward formation of 3D TME composed the hydrogel and multiple cell types. This facilitated monitoring of the effect of HA concentration and culture time on the TME. In 3D bone mimicking culture, we found that HA rich microenvironment affects cell viability, proliferation and cancer cell cytoplasmic volume in a manner dependent on the different metastatic cancer cell types and culture duration indicating the spatial heterogeneity (different origin of metastatic cancer) and temporal heterogeneity (growth time of cancer) of TME. We also found that both SW620 and MKN72 cells exhibited significantly reduced migration at higher HA concentration in our platform indicating inhibitory effect of HA in both cancer cells migration. Next, we quantitatively analyzed angiogenic sprouts induced by paracrine factors that secreted by TME and showed paracrine signals from tumor and stromal cell with a high HA concentration resulted in the formation of fewer sprouts. Finally we reconstituted vascularized TME allowing direct interaction between angiogenic sprouts and tumor-stroma microspheroids in a bone-mimicking microenvironment composing a tunable HA/fibrin composite. Our multifarious approach could be applied to drug screening and mechanistic studies of the metastasis, growth, and progression of bone tumors.