Seyed Nasrollah Tabatabaei

Microfluidic technologies have revolutionized the synthesis of nanocarriers for drug and gene delivery, providing unparalleled precision and efficiency in the production of therapeutic nanoparticles.

Introduction: Recently, membrane microfluidic chips (MFCs) have become available to study biological basement membranes. The nanofiber (NF) membranes are suitable substrates for cell attachment and trapping, as demonstrated by their surface properties. In this study, a novel microfluidic device based on the electrospun collagen-modified polyethylene terephthalate (PET)/polydimethylsiloxane (PDMS) was designed and fabricated to mimic biological basement membranes. Methods: Hybrid NF containing PDMS/PET and collagen were successfully fabricated by two-nozzle electrospinning, and then PDMS chips were fabricated by soft lithography. The integrity of the membrane and NFs structure before (BC) and after cross-linking (AC) was evaluated by SEM, AFM, contact angle, FT-IR, BET, and tensile analysis. For further studies, numerical simulations were performed to evaluate the microfluidic flow in the PDMS-based device and demonstrate the fluid flow on top of a membrane. In the simulation, we used COMSOL Multiphysics to study the influence of flow rate and different surface topographies on the velocity and shear rate characteristics. Results: Cross-linking of NFs increased the diameter of NF (from 391 ± 169 nm to 660 ± 199 nm), hydrophilicity, elongation, and surface roughness (from 66.9 nm to 296.7 nm), but decreased the pore size volume of NFs (0.06 cm³ g⁻¹ to 0.01 cm³ g⁻¹). Bonding of NFs was possible through the use of oxygen plasma activated materials based on PDMS and PET. After bonding the NFs in the channels with oxygenated plasma, human umbilical vein endothelial cells (HUVEC) and glial cell line (C6) were successfully cultured and stained in MFC with dynamic conditions for 24 h at a flow rate of 10 μl/min. Discussion: The rougher microchannels exhibited a non-uniform shear rate distribution, and the flow rate was a parameter with a significant influence on the shear rate and velocity (roughness=0.3 µm). These results provided reliable evidence that the combination of electrospun NFs and cell culture can closely resemble a cell matrix.

Microrobotics has opened new horizons for various applications, especially in medicine. However, it also witnessed challenges in achieving maximum optimal performance. One key challenge is the intelligent, autonomous, and precise navigation control of microrobots in fluid environments. The intelligence and autonomy in microrobot control, without the need for prior knowledge of the entire system, can offer significant opportunities in scenarios where their models are unavailable. In this study, two control systems based on model-free deep reinforcement learning were implemented to control the movement of a disk-shaped magnetic microrobot in a real-world environment. The training and results of an off-policy SAC algorithm and an on-policy TRPO algorithm revealed that the microrobot successfully learned the optimal path to reach random target positions. During training, the TRPO exhibited a higher sample efficiency and greater stability. The TRPO and SAC showed 100% and 97.5% success rates in reaching the targets in the evaluation phase, respectively. These findings offer basic insights into achieving intelligent and autonomous navigation control for microrobots to advance their capabilities for various applications.

Electrospun nanofibers can be used as membranes for cell culture applications. In addition to their high performance and cost-effectiveness, nanofibers can be made from a variety of polymers and utilized in microfluidic devices as separators, filters, and for biological assessments. In this paper, we have employed a two-pump technique to prepare a hybrid nanofiber-based membrane with a biocompatible polyethylene terephthalate (PET), polydimethylsiloxane (PDMS), and collagen. The introduction of collagen creates a suitable substrate for cell attachment and decreased hydrophobicity. To sustain collagen on the fibers, the membranes were treated with glutaraldehyde vapor and then detoxified. The membrane integrity and structure were evaluated using SEM, AFM, contact angle analyzer, FT-IR, and tensile apparatus. In addition, cell attachment capabilities and cytocompatibility were examined using SEM and AlamarBlue, respectively. The membrane was cased in a PDMS-based microfluidic device consisting of upper and lower channels. Our findings suggest that the incorporation of PET and PDMS provides a superior bonding capability and prevents unwanted leakage. Then, Human Umbilical Vein Endothelial Cells (HUVECs) were cultured on both sides of the proposed membrane inside the device. To simulate the dynamic environment and induce cellular shear stress, the culture medium was flown through the channel and the conditions were kept overnight inside an incubator. Cellular staining (Acridine Orange and Propidium Iodide, as well as DAPI) and further evaluation of cellular adhesion suggest that cells were well attached and viable inside the microfluidic device. The proposed membrane can be employed in fabrication of various biological barriers on-a-chip for the purpose of screening drugs, examining the effects of nanomaterials, and creation of in-vitro disease models.

Recent global outbreak of COVID-19 has raised serious awareness about our abilities to protect ourselves from hazardous pathogens and volatile organic compounds. Evidence suggests that personal protection equipment such as respiratory masks can radically decrease rates of transmission and infections due to contagious pathogens. To increase filtration efficiency without compromising breathability, application of nanofibers in production of respiratory masks have been proposed. The emergence of nanofibers in the industry has since introduced a next generation of respiratory masks that promises improved filtration efficiency and breathability via nanometric pores and thin fiber thickness. In addition, the surface of nanofibers can be functionalized and enhanced to capture specific particles. In addition to conventional techniques such as melt-blown, respiratory masks by nanofibers have provided an opportunity to prevent pathogen transmission. As the surge in global demand for respiratory masks increases, herein, we reviewed recent advancement of nanofibers as an alternative technique to be used in respiratory mask production.