Biomaterial-based microfluidics for cell culture and analysis

Organs-on-chips technologies – A guide from disease models to opportunities for drug development

Current in-vitro 2D cultures and animal models present severe limitations in recapitulating human physiopathology with striking discrepancies in estimating drug efficacy and side effects when compared to human trials. For these reasons, microphysiological systems, organ-on-chip and multiorgans microdevices attracted considerable attention as novel tools for high-throughput and high-content research to achieve an improved understanding of diseases and to accelerate the drug development process towards more precise and eventually personalized standards. This review takes the form of a guide on this fast-growing field, providing useful introduction to major themes and indications for further readings. We start analyzing Organs-on-chips (OOC) technologies for testing the major drug administration routes: (1) oral/rectal route by intestine-on-a-chip, (2) inhalation by lung-on-a-chip, (3) transdermal by skin-on-a-chip and (4) intravenous through vascularization models, considering how drugs penetrate in the bloodstream and are conveyed to their targets. Then, we focus on OOC models for (other) specific organs and diseases: (1) neurodegenerative diseases with brain models and blood brain barriers, (2) tumor models including their vascularization, organoids/spheroids, engineering and screening of antitumor drugs, (3) liver/kidney on chips and multiorgan models for gastrointestinal diseases and metabolic assessment of drugs and (4) biomechanical systems recapitulating heart, muscles and bones structures and related diseases. Successively, we discuss technologies and materials for organ on chips, analyzing (1) microfluidic tools for organs-on-chips, (2) sensor integration for real-time monitoring, (3) materials and (4) cell lines for organs on chips. (Nano)delivery approaches for therapeutics and their on chip assessment are also described. Finally, we conclude with a critical discussion on current significance/relevance, trends, limitations, challenges and future prospects in terms of revolutionary impact on biomedical research, preclinical models and drug development.

Transparent Microcrystalline Cellulose/Polyvinyl Alcohol Paper as a New Platform for Three-Dimensional Cell Culture

Multilayered and stacked cellulose paper has emerged as a promising platform for construction of three-dimensional (3D) cell culture because of its low cost, good biocompatibility, and high porosity. However, its poor light transmission makes it challenging to directly and clearly monitor cell behaviors (e.g., growth and proliferation) on the paper-based platform using an optical microscope. In this work, we developed a transparent microcrystalline cellulose/polyvinyl alcohol (MCC/PVA) paper with irregular pores through dissolution and regeneration of microcrystalline nanocellulose, addition of a porogen reagent (NaCl), and subsequently dipping in PVA solutions. The transparent MCC paper displays high porosity (up to 90%), adjustable pore size (between 23 and 46 μm), large thickness (from 315 to 436 μm), and high light transmission under water (>95%). Through further modification of the transparent MCC paper with PVA, the obtained transparent MCC/PVA paper shows enhanced mechanical properties (dry and wet strengths), good hydrophilicity (with a contact angle of 70.8°), and improved biocompatibility (cell viability up to 90%). By stacking and destacking multiple layers of the transparent MCC/PVA paper, it has been used for both two-dimensional and three-dimensional cell culture platforms. The transparent MCC/PVA paper under water enables both direct observation of cell morphology by an optical microscope via naked eyes and fluorescence microscope after staining. We envision that the developed transparent MCC/PVA paper holds great potential for future applications in various bioanalytical and biomedical fields, such as drug screening, tissue engineering, and organ-on-chips.

Dynamics of temperature-actuated droplets within microfluidics

Characterizing the thermal behavior of dispersed droplets within microfluidic channels is crucial for different applications in lab-on-a-chip. In this paper, the physics of droplets volume during their transport over a heater is studied experimentally and numerically. The response of droplets to external heating is examined at temperature ranges of 25–90 °C and at different flow rates of the dispersed phase respect to the continuous flow. The results present a reliable prediction of the droplet volume and stability when heating is applied to the droplets at the downstream channel in a quite far distance from the droplets’ ejection orifice. Increasing the ratio of flow rate resulted in larger droplets; for instance, the flow ratio of 0.25 produced drops with 40% larger diameter than the flow rate of 0.1. For every 10 °C increase in temperature of the droplets, the droplet diameter increased by about 5.7% and 4.2% for pure oil and oil with a surfactant, respectively. Also, the droplets showed a degree of instability during their transport over the heater at higher temperatures. Adding SPAN 20 surfactant improved the stability of the droplets at temperatures higher than 60 °C. The experimentally validated numerical model helped for systemic analysis of the influence of key temperature-dependence parameters (e.g. surface tension, density and viscosity of both phases) on controlling the volume and stability of droplets. Our findings supported to develop highly functional systems with a predetermined droplets performance under high temperatures up to 90 °C. This report provides a preliminary basis for enhancing the performance of droplet microfluidic systems for digital droplet polymerase chain reaction (ddPCR), continuous flow digital loop-mediated isothermal PCR (LAMP), and droplet-based antibiotic susceptibility testing.

Evaluation of drug combination for glioblastoma based on an intestine-liver metabolic model on microchip

An intestine-liver-glioblastoma biomimetic system was developed to evaluate the drug combination therapy for glioblastoma. A hollow fiber (HF) was embedded into the upper layer of the microfluidic chip for culturing Caco-2 cells to mimic drug delivery as an artificial intestine. HepG2 cells cultured in the bottom chamber of the chip acted as an artificial liver for metabolizing the drugs. The dual-drug combination to glioblastoma U251 cells was evaluated based on the intestine-liver metabolic model. The drugs, irinotecan (CPT-11), temozolomide (TMZ) and cyclophosphamide (CP), were used to dynamically stimulate the cells by continuous infusion into the intestine unit. After intestine absorption and liver metabolism, the prodrugs were transformed to active metabolites, which induced glioblastoma cells apoptosis. The anticancer activity of the CPT-11 and TMZ combination is significantly enhanced compared to that of the single drug treatments. Combination index (CI) values of the combination groups, CPT-11 and TMZ, CPT-11 and CP, and TMZ and CP, at half maximal inhibitory concentration were 0.137, 0.288, and 0.482, respectively. The results indicated that the CPT-11 and TMZ combination was superior to the CPT-11 and CP group as well as the TMZ and CP group towards the U251 cells. The metabolism mechanism of CPT-11 and TMZ was further studied by coupling with mass spectrometric analysis. The biomimetic model enables the performance of long-term cell co-culture, drug delivery, metabolism and real-time analysis of drug effects, promising systematic in vitro mimicking of physiological and pharmacological processes.

Predictive modelling of the water contact angle of surfaces using attenuated total reflection – Fourier transform infrared (ATR-FTIR) chemical imaging and partial least squares regression (PLSR)

A simple method to model and predict the surface wettability using a combination of ATR-FTIR imaging and PLSR modelling.