Natural organisms provide inspirations for various functional structures and surfaces with significant applications in multidisciplinary fields. These biological systems are generally composed of multiscale surface structures with high geometric complexity and a variety of materials, making it challenging to replicate their characteristics in engineering. This study presents a novel multiscale multimaterial 3D printing method, magnetic field-assisted stereolithography (M-SL), for fabricating hierarchical particle–polymer structures with surface features ranging from a few nanometers to millimeters or even centimeters. Taking inspiration from nature, this study describes the design and fabrication of a bioinspired multiscale hierarchical surface structure, which is characterized of microscale cones, nanoscale pores, and surface wrinkles at a few nanometers. To understand the fundamental physics underlying the hierarchical surface structure fabrication in the proposed M-SL process, the complexities among the M-SL process parameters, material parameters, and printed geometries are discussed. The accuracy of the developed printing method is investigated by comparing the printed geometries and digital designs. Effects of the printed hierarchical surface structure on hydrophobicity and cell viability were characterized and discussed. It was found that the highly hierarchical surface structure changed the polymer composite surface from hydrophilic (contact angle: ∼38°) to hydrophobic (∼146°). In addition, the hierarchical surface structure also created a better environment for cell attachment and growth, with 900% more living cells at 72 h after cell seeding, compared with cells on the nonstructured smooth surface. Local and selective cell seeding can also be enabled by the surface structure design. Experimental results validated the effectiveness of the M-SL 3D printing method on fabricating multimaterial functional objects with hierarchically structured surfaces for a wide spectrum of applications.
Oxygen concentration varies tremendously within the body and has proven to be a critical variable in cell differentiation, proliferation, and drug metabolism among many other physiological processes. Currently, researchers study the gas's role in biology using low-throughput gas control incubators or hypoxia chambers in which all cells in a vessel are exposed to a single oxygen concentration. Here, we introduce a device that can simultaneously deliver 12 unique oxygen concentrations to cells in a 96-well plate and seamlessly integrate into biomedical research workflows. The device inserts into 96-well plates and delivers gas to the headspace, thus avoiding undesirable contact with media. This simple approach isolates each well using gas-tight pressure-resistant gaskets effectively creating 96 "mini-incubators". Each of the 12 columns of the plate is supplied by a distinct oxygen concentration from a gas-mixing gradient generator supplied by two feed gases. The wells within each column are then supplied by an equal flow-splitting distribution network. Using equal feed flow rates, concentrations ranging from 0.6 to 20.5% were generated within a single plate. A549 lung carcinoma cells were then used to show that O 2 levels below 9% caused a stepwise increase in cell death for cells treated with the hypoxia-activated anticancer drug tirapirizamine (TPZ). Additionally, the 96-well plate was further leveraged to simultaneously test multiple TPZ concentrations over an oxygen gradient and generate a three-dimensional (3D) dose−response landscape. The results presented here show how microfluidic technologies can be integrated into, rather than replace, ubiquitous biomedical labware allowing for increased throughput oxygen studies.
We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions.
Oxygen concentration varies tremendously within the body and has proven to be a critical variable in cell differentiation, proliferation, and drug metabolism among many other physiological processes. Currently, researchers study the gas’s role in biology using low-throughput gas-control incubators or hypoxia chambers in which all cells in a vessel are exposed to a single oxygen concentration. Here, we introduce a device which can simultaneously deliver 12 unique oxygen concentrations to cells in a 96-well plate and seamlessly integrate into biomedical research workflows. The device inserts into 96-well plates and delivers gas to the headspace thus avoiding undesirable contact with media. This simple approach isolates each well using gas-tight pressure resistant gaskets effectively creating 96 “mini-incubators”. Each of the twelve columns of the plate is supplied by a distinct oxygen concentration from a gas-mixing gradient generator supplied by two feed gases. The wells within each column are then supplied by an equal flow-splitting distribution network. Using equal feed flow rates, concentrations ranging from 0.6% to 20.5% were generated within a single plate. A549 lung carcinoma cells were then used to show that O2 levels below 9% caused a stepwise increase in cell death for cells treated with the hypoxia-activated anti-cancer drug Tirapirizamine (TPZ). Additionally, the 96-well plate was further leveraged to simultaneously test multiple TPZ concentrations over an oxygen gradient and generate a 3D dose response landscape. The results presented here show how microfluidic technologies can be integrated into, rather than replace, ubiquitous biomedical labware allowing for increased throughput oxygen studies.
Hydrodynamic focusing capable of readily producing and controlling laminar flow facilitates drug treatment of cells in existing microfluidic culture devices. However, to expand applications of such devices to multiparameter drug testing, critical limitations in current hydrodynamic focusing microfluidics must be addressed. Here we describe hydrodynamic focusing and shifting as an advanced microfluidics tool for spatially selective drug delivery and integrative cell-based drug testing. We designed and fabricated a co-flow focusing, three-channel microfluidic device with a wide cell culture chamber. By controlling inlet flow rates of sample and two side solutions, we could generate hydrodynamic focusing and shifting that mediated precise regulation of the path and width of reagent and drug stream in the microfluidic device. We successfully validated a hydrodynamic focusing and shifting approach for spatially selective delivery of DiI, a lipophilic fluorophore, and doxorubicin, a chemotherapeutic agent, to tumor cells in our device. Moreover, subsequent flowing of a trypsin EDTA solution over the cells that were exposed to doxorubicin flow allowed us to selectively collect the treated cells. Our approach enabled downstream high-resolution microscopy of the cell suspension to confirm the nuclear delivery of doxorubicin into the tumor cells. In the device, we could also evaluate in situ the cytotoxic effect of doxorubicin to the tumor cells that were selectively treated by hydrodynamic flow focusing and shifting. These results show that hydrodynamic focusing and shifting enable a fast and robust approach to spatially treat and then collect cells in an optimized microfluidic device, offering an integrative assay tool for efficient drug screening and discovery.
High blood pressure is the primary risk factor for heart disease, the leading cause of death globally. Despite this, current methods to replicate physiological pressures in-vitro remain limited in sophistication...
High blood pressure is the primary risk factor for heart disease, the leading cause of death globally. Despite this, current methods to replicate physiological pressures in-vitro remain limited in sophistication and throughput. Single-chamber exposure systems allow for only one pressure condition to be studied at a time and the application of dynamic pressure waveforms is currently limited to simple sine, triangular, or square waves. Here, we introduce a high-throughput hydrostatic pressure exposure system for 96-well plates. The platform can deliver a fully-customizable pressure waveform to each column of the plate, for a total of 12 simultaneous conditions. Using clinical waveform data, we are able to replicate real patients ′ blood pressures as well as other medically-relevant pressures within the body and have assembled a small patient-derived waveform library of some key physiological locations. As a proof of concept, human umbilical vein endothelial cells (HUVECs) survived and proliferated under pressure for 3 days under a wide range of static and dynamic blood pressures ranging from 10 mm Hg to 400 mm Hg. Interestingly, pathologic and supraphysiologic pressure exposures did not inhibit cell proliferation. By integrating with, rather than replacing, ubiquitous lab cultureware it is our hope that this device will facilitate the incorporation of hydrostatic pressure into standard cell culture practice.
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