Research efforts into the production and application of iron oxide nanoparticles (IONPs) in recent decades have shown IONPs to be promising for a range of biomedical applications. Many synthesis techniques have been developed to produce high-quality IONPs that are safe for in vivo environments while also being able to perform useful biological functions. Among them, coprecipitation is the most commonly used method but has several limitations such as polydisperse IONPs, long synthesis times, and batch-to-batch variations. Recent efforts at addressing these limitations have led to the development of microfluidic devices that can make IONPs of much-improved quality. Here, we review recent advances in the development of microfluidic devices for the synthesis of IONPs by coprecipitation. We discuss the main architectures used in microfluidic device design and highlight the most prominent manufacturing methods and materials used to construct these microfluidic devices. Finally, we discuss the benefits that microfluidics can offer to the coprecipitation synthesis process including the ability to better control various synthesis parameters and produce IONPs with high production rates.

Natural polymer-based porous scaffolds have been investigated to serve as three-dimensional (3D) tumor models for drug screening owing to their structural properties with better resemblance to human tumor microenvironments than two-dimensional (2D) cell cultures. In this study, a 3D chitosan–hyaluronic acid (CHA) composite porous scaffold with tunable pore size (60, 120 and 180 µm) was produced by freeze-drying and fabricated into a 96-array platform for high-throughput screening (HTS) of cancer therapeutics. We adopted a self-designed rapid dispensing system to handle the highly viscous CHA polymer mixture and achieved a fast and cost-effective large-batch production of the 3D HTS platform. In addition, the adjustable pore size of the scaffold can accommodate cancer cells from different sources to better mimic the in vivo malignancy. Three human glioblastoma multiforme (GBM) cell lines were tested on the scaffolds to reveal the influence of pore size on cell growth kinetics, tumor spheroid morphology, gene expression and dose-dependent drug response. Our results showed that the three GBM cell lines showed different trends of drug resistance on CHA scaffolds of varying pore size, which reflects the intertumoral heterogeneity across patients in clinical practice. Our results also demonstrated the necessity to have a tunable 3D porous scaffold for adapting the heterogeneous tumor to generate the optimal HTS outcomes. It was also found that CHA scaffolds can produce a uniform cellular response (CV < 0.15) and a wide drug screening window (Z′ > 0.5) on par with commercialized tissue culture plates, and therefore, can serve as a qualified HTS platform. This CHA scaffold-based HTS platform may provide an improved alternative to traditional 2D-cell-based HTS for future cancer study and novel drug discovery.

Human neural stem cells (hNSCs) possess remarkable potential for regenerative medicine in the treatment of presently incurable diseases. However, a key challenge lies in producing sufficient quantities of hNSCs, which is necessary for effective treatment. Dynamic culture systems are recognized as a powerful approach to producing large quantities of hNSCs required, where microcarriers play a critical role in supporting cell expansion. Nevertheless, the currently available microcarriers have limitations, including a lack of appropriate surface chemistry to promote cell adhesion, inadequate mechanical properties to protect cells from dynamic forces, and poor suitability for mass production. Here, we present the development of three-dimensional (3D) chitosan scaffolds as microcarriers for hNSC expansion under defined conditions in bioreactors. We demonstrate that chitosan scaffolds with a concentration of 4 wt% (4CS scaffolds) exhibit desirable microstructural characteristics and mechanical properties suited for hNSC expansion. Furthermore, they could also withstand degradation in dynamic conditions. The 4CS scaffold condition yields optimal metabolic activity, cell adhesion, and protein expression, enabling sustained hNSC expansion for up to three weeks in a dynamic culture. Our study introduces an effective microcarrier approach for prolonged expansion of hNSCs, which has the potential for mass production in a three-dimensional setting.

Cells cultured in three-dimensional scaffolds express a phenotype closer to in vivo cells than cells cultured in two-dimensional containers. Natural polymers are suitable materials to make three-dimensional scaffolds to develop disease models for high-throughput drug screening owing to their excellent biocompatibility. However, natural polymer solutions have a range of viscosities, and none of the currently available liquid dispensers are capable of dispensing highly viscous polymer solutions. Here, we report the development of an automated scaffold dispensing system for rapid, reliable, and homogeneous creation of scaffolds in well-plate formats. We employ computer-controlled solenoid valves to regulate air pressure impinging upon a syringe barrel filled with scaffold solution to be dispensed. Automated dispensing of scaffold solution is achieved via a programmable software interface that coordinates solution extrusion and the movement of a dispensing head. We show that our pneumatically actuated dispensing system can evenly distribute high-viscosity, chitosan-based polymer solutions into 96- and 384-well plates to yield highly uniform three-dimensional scaffolds after lyophilization. We provide a proof-of-concept demonstration of high-throughput drug screening by culturing glioblastoma cells in scaffolds and exposing them to temozolomide. This work introduces a device that can hasten the creation of three-dimensional cell scaffolds and their application to high-throughput testing.

Human neural stem cells (hNSCs) are vital for advancing therapies for neurocognitive disorders. However, standard hNSC culture conditions often lack chemically defined and xeno-free substrates, limiting their clinical applicability. Chitosan, known for its biocompatibility, presents a promising alternative for hNSC culture. Hyaluronic acid (HA) and alginate, with their negative charges, enable effective interaction with positively charged chitosan to form films with enhanced mechanical properties. Incorporating chitosan into substrates creates chitosan–alginate (CA) and chitosan–hyaluronic acid (CHA) composites that meet chemically defined, mechanically tunable, and xeno-free standards. Despite their potential, the effects of these composites’ composition and mechanical properties on hNSC behavior, particularly in film form, remain unexplored. To bridge this gap, we fabricated films with varying chitosan-to-alginate and chitosan-to-hyaluronic acid ratios to assess their influence on hNSC pluripotency under xeno-free conditions. Our results reveal that films with higher chitosan content promote hNSC attachment and proliferation. Conversely, increasing alginate generally decreased cell attachment, proliferation, and multipotency, while increasing HA had no impact on attachment or proliferation but decreased multipotency. This investigation provides insights into the impact of substrate composition and mechanical properties on hNSC behavior, guiding the design of analogous materials for three-dimensional cultures and optimizing stem cell-based therapies for clinical applications.