Mask-free fabrication of a versatile microwell chip for multidimensional cellular analysis and drug screening

Cryopreserving 3D cell culture models of Alzheimer's disease in hydrogel microbeads

Long-term preservation of fully differentiated human neurons poses a longstanding challenge in neuroscience research. Numerous cellular disease models have been established using cultured human neuronal cells, including our three-dimensional (3D) human neural cell culture model of Alzheimer's disease (AD). However, the absence of a reliable method for preserving fully differentiated human neural cell cultures for a long time has hindered the sharing and standardization of these models. To address this critical limitation, we focused on cryopreservation, which is the gold standard for long-term preservation, and combined this with three key technological advancements. First, we employed parallelized microfluidic devices for the efficient generation of 3D cell cultures within uniform hydrogel microbeads (~ 220 μm), which facilitate the rapid exchange of media ingredients and cryoprotectants. Second, we implemented a cytophobic microwell system to safeguard neuron-encapsulated microbeads from fusion and aggregation. Third, we developed a novel inducible AD cell model optimized for cryopreservation and AD drug testing. We have successfully maintained encapsulated control and AD neural progenitor cells in microwells during differentiation for 12 days. Notably, fully differentiated human neural cells can be cryopreserved within Matrigel microbeads while retaining intact and mature neuronal processes, exhibiting no signs of damage to neurites following freeze/thaw cycles. Furthermore, we have demonstrated the successful cryopreservation, thawing, and induction of pathogenic Amyloid-β 42 (Aβ42) generation in fully differentiated AD neural progenitor cells. Our study offers a solution for one of the major challenges in neuroscience research, utilizing porous hydrogel microbead structures to facilitate rapid delivery of cryoprotectants and protect complex neuronal structures without undergoing damaging cell dissociation steps. The inducible "3D human microbead model of AD" enhances the speed, efficacy, and reproducibility of AD drug screening.

Rapid Whole-Plate Cell and Tissue Micropatterning Using a Budget 3D Resin Printer

The ability to precisely pattern cells and proteins is crucial in various scientific disciplines, including cell biology, bioengineering, and materials chemistry. Current techniques, such as microcontact stamping, 3D bioprinting, and direct photopatterning, have limitations in terms of cost, versatility, and throughput. In this Article, we present an accessible approach that combines the throughput of photomask systems with the versatility of programmable light patterning using a low-cost consumer LCD resin printer. The method involves utilizing a bioinert hydrogel, poly(ethylene glycol) diacrylate (PEGDA), and a 405 nm sensitive photoinitiator (LAP) that are selectively cross-linked to form a hydrogel upon light exposure, creating specific regions that are protein and cell-repellent. Our result highlights that a low-cost LCD resin printer can project virtual photomasks onto the hydrogel, allowing for reasonable resolution and large-area printing at a fraction of the cost of traditional systems. The study demonstrates the calibration of exposure times for optimal resolution and accuracy and shape corrections to overcome the inherent challenges of wide-field resin printing. The potential of this approach is validated through widely studied 2D and 3D stem cell applications, showcasing its biocompatibility and ability to replicate complex tissue engineering patterns. We also validate the method with a cell-adhesive polymer (gelatin methacrylate; GelMA). The combination of low cost, high throughput, and accessibility makes this method broadly applicable across fields for enabling rapid and precise fabrication of cells and tissues in standard laboratory culture vessels.

Straightforward Cell Patterning with Ultra-Low Background Using Polydimethylsiloxane Through-Hole Membranes

Micropatterning is becoming an increasingly popular tool to realize microscale cell positioning and decipher cell activities and functions under specific microenvironments. However, a facile methodology for building a highly precise cell pattern still remains challenging. In this study, A simple and straightforward method for stable and efficient cell patterning with ultra-low background using polydimethylsiloxane through-hole membranes is developed. The patterning process is conveniently on the basis of membrane peeling and routine pipetting. Cell patterning in high quality involving over 97% patterning coincidence and zero residue on the background is achieved. The high repeatability and stability of the established method for multiple types of cell arrangements with different spatial profiles is demonstrated. The customizable cell patterning with ultra-low background and high diversity is confirmed to be quite feasible and reliable. Furthermore, the applicability of the patterning method for investigating the fundamental cell activities is also verified experimentally. The authors believe this microengineering advancement has valuable applications in many microscale cell manipulation-associated research fields including cell biology, cell engineering, cell imaging, and cell sensing.

Microstructured soft devices for the growth and analysis of populations of homogenous multicellular tumor spheroids

Multicellular tumor spheroids are rapidly emerging as an improved in vitro model with respect to more traditional 2D culturing. Microwell culturing is a simple and accessible method for generating a large number of uniformly sized spheroids, but commercially available systems often do not enable researchers to perform complete culturing and analysis pipelines and the mechanical properties of their culture environment are not commonly matching those of the target tissue. We herein report a simple method to obtain custom-designed self-built microwell arrays made of polydimethylsiloxane or agarose for uniform 3D cell structure generation. Such materials can provide an environment of tunable mechanical flexibility. We developed protocols to culture a variety of cancer and non-cancer cell lines in such devices and to perform molecular and imaging characterizations of the spheroid growth, viability, and response to pharmacological treatments. Hundreds of tumor spheroids grow (in scaffolded or scaffold-free conditions) at homogeneous rates and can be harvested at will. Microscopy imaging can be performed in situ during or at the end of the culture. Fluorescence (confocal) microscopy can be performed after in situ staining while retaining the geographic arrangement of spheroids in the plate wells. This platform can enable statistically robust investigations on cancer biology and screening of drug treatments.

Miniaturized and multiplexed high-content screening of drug and immune sensitivity in a multichambered microwell chip

Here, we present a methodology based on multiplexed fluorescence screening of two- or three-dimensional cell cultures in a newly designed multichambered microwell chip, allowing direct assessment of drug or immune cell cytotoxic efficacy. We establish a framework for cell culture, formation of tumor spheroids, fluorescence labeling, and imaging of fixed or live cells at various magnifications directly in the chip together with data analysis and interpretation. The methodology is demonstrated by drug cytotoxicity screening using ovarian and non-small cell lung cancer cells and by cellular cytotoxicity screening targeting tumor spheroids of renal carcinoma and ovarian carcinoma with natural killer cells from healthy donors. The miniaturized format allowing long-term cell culture, efficient screening, and high-quality imaging of small sample volumes makes this methodology promising for individualized cytotoxicity tests for precision medicine.

Live single cell imaging assays in glass microwells produced by laser-induced deep etching

Miniaturization of cell culture substrates enables controlled analysis of living cells in confined micro-scale environments. This is particularly suitable for imaging individual cells over time, as they can be monitored without escaping the imaging field-of-view (FoV). Glass materials are ideal for most microscopy applications. However, with current methods used in life sciences, glass microfabrication is limited in terms of either freedom of design, quality, or throughput. In this work, we introduce laser-induced deep etching (LIDE) as a method for producing glass microwell arrays for live single cell imaging assays. We demonstrate novel microwell arrays with deep, high-aspect ratio wells that have rounded, dimpled or flat bottom profiles in either single-layer or double-layer glass chips. The microwells are evaluated for microscopy-based analysis of long-term cell culture, clonal expansion, laterally organized cell seeding, subcellular mechanics during migration and immune cell cytotoxicity assays of both adherent and suspension cells. It is shown that all types of microwells can support viable cell cultures and imaging with single cell resolution, and we highlight specific benefits of each microwell design for different applications. We believe that high-quality glass microwell arrays enabled by LIDE provide a great option for high-content and high-resolution imaging-based live cell assays with a broad range of potential applications within life sciences.

Rapid Formation of Stem Cell Spheroids Using Two-Dimensional MXene Particles

Cell spheroids have been studied as a biomimic medicine for tissue healing using cell sources. Rapid cell spheroid production increases cell survival and activity as well as the efficiency of mass production by reducing processing time. In this study, two-dimensional MXene (Ti3C2) particles were used to form mesenchymal stem cell spheroids, and the optimal MXene concentration, spheroid-production times, and bioactivity levels of spheroid cells during this process were assessed. A MXene concentration range of 1 to 10 μg/mL induced spheroid formation within 6 h. The MXene-induced spheroids exhibited osteogenic-differentiation behavior, with the highest activity levels at a concentration of 5 μg/mL. We report a novel and effective method for the rapid formation of stem cell spheroids using MXene.

Advances in Micro/Nanoporous Membranes for Biomedical Engineering

Porous membrane materials at the micro/nanoscale have exhibited practical and potential value for extensive biological and medical applications associated with filtration and isolation, cell separation and sorting, micro-arrangement, in-vitro tissue reconstruction, high-throughput manipulation and analysis, and real-time sensing. Herein, an overview of technological development of micro/nanoporous membranes (M/N-PMs) is provided. Various membrane types and the progress documented in membrane fabrication techniques, including the electrochemical-etching, laser-based technology, microcontact printing, electron beam lithography, imprinting, capillary force lithography, spin coating, and microfluidic molding are described. Their key features, achievements, and limitations associated with micro/nanoporous membrane (M/N-PM) preparation are discussed. The recently popularized applications of M/N-PMs in biomedical engineering involving the separation of cells and biomolecules, bioparticle operations, biomimicking, micropatterning, bioassay, and biosensing are explored too. Finally, the challenges that need to be overcome for M/N-PM fabrication and future applications are highlighted.

Robotized algal cells and their multiple functions

From an engineering perspective, algal cells with the abilities of perception and driving can be considered as microrobots. Site-specific, quantitative assembly of algal robots and the manipulated objects and collaborative task performance by algal robots would benefit biomedicine, environmental monitoring, and micro-nano manufacturing. Herein, site-specific, quantitative assembly and drive of algal cells are investigated. The mechanism of cell movement is analyzed, and cell motility is evaluated with or without light control. To robotize algal cells, an algae-guiding system is built, through which a swarm of algal cells is controlled to follow trajectories. By the cell adhesion method, adhesion and release between algal cells and microstructures are achieved. Algal cells successfully transport microspheres and release them at a destination. The cells are continuously operated for 60 min while carrying microspheres and they travel up to 270 mm. An optical guiding method is then developed for controlled assembly of algal robots onto fabricated micro-objects. The rotational movement of the microstructures is realized through cooperative driving by algal cells. This research provides a new biological driving method based on algal cells, which swim and behave as microrobots and are expected to benefit microassembly, microcargo traverse/delivery, and biological collaboration.

A 3D Printed Hanging Drop Dripper for Tumor Spheroids Analysis Without Recovery

Compared with traditional monolayer cell culture, the three-dimensional tumor spheroid has emerged as an essential in vitro model for cancer research due to the recapitulation of the architecture and physiology of solid human tumors. Herein, by implementing the rapid prototyping of a benchtop 3D printer, we developed a new strategy to generate and analyze tumor spheroids on a commonly used multi-well plate. In this method, the printed artifact can be directly mounted on a 96/384-well plate, enables hanging drop-based spheroid formation, avoiding the tedious fabrication process from micromechanical systems. Besides long-term spheroid culture (20 days), this method supports subsequent analysis of tumor spheroid by seamlessly dripping from the printed array, thereby eliminating the need for spheroids retrieval for downstream characterization. We demonstrated several tumor spheroid-based assays, including tumoroid drug testing, metastasis on or inside extracellular matrix gel, and tumor transendothelial (TEM) assay. Based on quantitative phenotypical and molecular analysis without any precarious retrieval and transfer, we found that the malignant breast cancer (MDA-MB-231) cell aggregate presents a more metastatic morphological phenotype than the non-malignant breast cancer (MCF-7) and colonial cancer (HCT-116) cell spheroid, and shows an up-regulation of epithelial-mesenchymal transition (EMT) relevant genes (fold change > 2). Finally, we validated this tumor malignancy by the TEM assay, which could be easily performed using our approach. This methodology could provide a useful workflow for expediting tumoroid modeled in vitro assay, allowing the “Lab-on-a-Cloud” scenario for routine study.

Durable superamphiphobic silica aerogel surfaces for the culture of 3D cellular spheroids

The 3D multicellular spheroids with intact cell-cell junctions have major roles in biological research by virtue of their unique advantage of mimicking the cellular physiological environments. In this work, a durable superamphiphobic silica aerogel surface (SSAS) has been fabricated for the upward culture of 3D multicellular spheroids. Poly(3,4-ethylenedioxythiophene) (PEDOT) was first electrodeposited on a conductive steel mesh as a first template for porous silica coating. Soot particles were then applied as a second template to construct a cauliflower-like silica aerogel nanostructure. After fluorination, a hierarchical structure with re-entrant curvature was finally fabricated as a durable superamphiphobic surface. This superamphiphobic surface also presented excellent antifouling towards biomacromolecules and cells, which has been demonstrated by the successful upward culture of cell spheroids. The upward culture makes the observation of cellular behavior in situ possible, holding great potential for 3D cellular evaluation in vitro.

2D to 3D Manipulation and Assembly of Microstructures Using Optothermally Generated Surface Bubble Microrobots

Hydrogel microstructures that encapsulate cells can be assembled into tissues and have broad applications in biology and medicine. However, 3D posture control for a single arbitrary microstructure remains a challenge. A novel 3D manipulation and assembly technique based on optothermally generated bubble robots is proposed. The generation, rate of growth, and motion of a microbubble robot can be controlled by modulating the power of a laser focused on the interface between the substrate and a fluid. In addition to 2D operations, bubble robots are able to perform 3D manipulations. The 3D properties of hydrogel microstructures are adjusted arbitrarily, and convex and concave structures with different heights are designed. Furthermore, annular micromodules are assembled into 3D constructs, including tubular and concentric constructs. A variety of hydrogel microstructures of different sizes and shapes are operated and assembled in both 2D and 3D conformations by bubble robots. The manipulation and assembly methods are simple, rapid, versatile, and can be used for fabricating tissue constructs.

Development of Multi-Dimensional Cell Co-Culture via a Novel Microfluidic Chip Fabricated by DMD-Based Optical Projection Lithography

Establishing a physiological microenvironment in vitro that is suitable for cell and tissue growth is essential for medical research. Microfluidic chips are widely used in the construction of a microenvironment and the analysis of cell behavior in vitro; however, the design and manufacture of microfluidic chips for the long-term culture of a tumor model tends to be highly complex and time-consuming. In this paper, we propose a method for the rapid fabrication of a microfluidic chip for multi-dimensional cell co-culture. A major advantage of this method is that the microfluidic chip can be divided into several sections by micro-pillar arrays to form different functional regions to grow two- and three-dimensional cell culture on the same matrix. At the micro-scale, the surface tension between the gelatin methacryloyl-encapsulated cells and micro-pillars prevents the leakage of the hydrogel, and the hydrogel provides a three-dimensional microenvironment for cell growth. Our results of long-term cell culture and preclinical drug screening showed that cells cultured in a two-dimensional monolayer differ from three-dimensional cultured cells in terms of morphology, area, survival rate, proliferation, and drug resistance. This method shows potential for use in the study of cell behavior, drug screening, and tissue engineering.

Engineered tissue micro-rings fabricated from aggregated fibroblasts and microfibres for a bottom-up tissue engineering approach

Tissue rings with incorporated microscaffolds have been engineered as promising building blocks for constructing biological tubes from the bottom up. However, the microscaffolds available for incorporation are very limited at present. In this paper we provide an efficient strategy to first incorporate microfluidic spun Ca-alginate microfibres encapsulating magnetic nanoparticles into self-assembled fibroblast micro-rings. Based on the surface modification, microfibres with a size of ∼40 μm allowed fibroblasts to spread and proliferate along the long axis. The optimal cell seeding density was obtained by evaluating the degree of coverage of fibroblasts on microfibres after 3 days of culture. Then we designed a magnetically guided culture apparatus with multiple annular micro-wells to facilitate cell-driven assembly of microfibres. A manipulation strategy dependent on surface tension was used to pattern microfibres along the micro-wells prior to cell seeding, and magnetic attraction further kept the patterned microfibres from being deposited in the micro-wells during cultivation. Within 3 days of culture, microfibre-incorporated tissue micro-rings were formed in the micro-wells. Quantitative analysis of the formation process revealed liquid-like aggregating behaviours, and incorporated microfibres showed the potential to promote the directed organization of cells in tissue micro-rings. Furthermore, magnetically driven manipulation was used robotically to assemble the micro-rings on a micropillar inserted into the centre of the culture apparatus. After 5 days of culture to allow cell fusion, a biological tubular microstructure was achieved. Microfluidic spinning can generate fibres with a variety of shapes, geometries, and compositions; therefore, our proposed method greatly enriches the variety of microscaffolds available for incorporation into tissue rings to engineer complex artificial organs for tissue engineering and regenerative medicine.

Recent advances in single cell manipulation and biochemical analysis on microfluidics

Single cell analysis has become of great interest with unprecedented capabilities for the systematic investigation of cell-to-cell variation in large populations. Rapid and multi-parametric analysis of intercellular biomolecules at the single-cell level is imperative for the improvement of early disease diagnosis and personalized medicine. However, the small size of cells and the low concentration levels of target biomolecules are critical challenges for single cell analysis. In recent years, microfluidic platforms capable of handling small-volume fluid have been demonstrated to be powerful tools for single cell analysis. In addition, microfluidic techniques allow for precise control of the localized microenvironment, which yield more accurate outcomes. Many different microfluidic techniques have been greatly improved for highly efficient single-cell manipulation and highly sensitive detection over the past few decades. To date, microfluidics-based single cell analysis has become the hot research topic in this field. In this review, we particularly highlight the advances in this field during the past three years in the following three aspects: (1) microfluidic single cell manipulation based on microwells, micropatterns, droplets, traps and flow cytometric methods; (2) detection methods based on fluorescence, mass spectrometry, electrochemical, and polymerase chain reaction-based analysis; (3) applications in the fields of small molecule detection, protein analysis, multidrug resistance analysis, and single cell sequencing with droplet microfluidics. We also discuss future research opportunities by focusing on key performances of throughput, multiparametric target detection and data processing.

High-density micro-well array with aptamer-silver conjugates for cell sorting and imaging at single cells

Characterizing cell behavior is important to modern medical diagnoses as the changes of cell behavior are often indicators of huge diseases. In order to gain enough information about cells, developing novel methods of cell sorting and imaging is an important task. With development of micro-fabrication technologies, more advanced miniaturized devices are applied to cell research. Here, a portable and easy-to-use chip with high-density periodic micro-well array is designed and fabricated to capture target cells specifically. Combining with aptamer-silver conjugates and FAM functioned report probes, the sandwich assay was successfully applied for imaging cells. Any well of the chip is carefully designed to provide abundant information on single cells. Since there are 19,200 microwells in a single chip, more information is available. Compared to other cells, such as HEK-293, MCF-7, U₂OS and Ramos cells, the sandwich assay shows high specificity towards target cell CCRF-CEM. What's more, the applications of the chip can be further expanded to other cells imaging if suitable aptamers were selected. This high-density micro-well array of aptamer-silver conjugates is hopeful to play an important role in medical diagnosis in the future.

Stem cell-based retina models

From the early days of cell biological research, the eye-especially the retina-has evoked broad interest among scientists. The retina has since been thoroughly investigated and numerous models have been exploited to shed light on its development, morphology, and function. Apart from various animal models and human clinical and anatomical research, stem cell-based models of animal and human cells of origin have entered the field, especially during the last decade. Despite the observation that the retina of different species comprises endogenous stem cells, most stem cell-related research in the human retina is now based on pluripotent stem cell models. Herein, systems of two-dimensional (2D) cultures and co-cultures of distinctly differentiated retinal subtypes revealed a variety of cellular aspects but have in many aspects been replaced by three-dimensional (3D) structures-the so-called retinal organoids. These organoids not only contain all major retinal cell subtypes compared to the physiological situation, but also show a distinct layering in close proximity to the in vivo morphology. Nevertheless, all these models have inherent advantages and disadvantages, which are expounded and summarized in this review. Finally, we discuss current application aspects of stem cell-based retina models and the specific promises they hold for the future.

3D microfluidic in vitro model and bioinformatics integration to study the effects of Spatholobi Caulis tannin in cervical cancer

Cervical cancer is considered the fourth most common malignant disease in women. Recently, tannin from Spatholobi Caulis (TTS) has been shown to have potent anticancer and antiproliferative characteristics in a few preliminary studies. This experiment used 3D microfluidic, flow cytometry, and gene chip technology to study the efficacy and mechanism of action of TTS, as well as molecular docking technology to study the effect of drugs on related proteins. The cell survival rates of the five groups measured by the 3D microfluidic chip were 94%, 85%, 64%, 55%, and 42%, respectively. With the increase in drug concentration, the cell survival rate gradually decreased. Apoptosis rates detected in the five groups were 2.12%, 15.87%, 33.40%, 41.13%, and 55.10%, respectively. These data suggest that TTS can promote cell apoptosis. The percentages of cells in the G0/G1 phase were 43.39%, 55.07%, 59.57%, 64.56%, and 67.39% in the five groups, respectively. TTS was demonstrated to inhibit the conversion of cells from G0/G1 to S phase and G2/M phase and inhibit gene and protein synthesis to block cell proliferation. TTS can effectively modulate pathogenic proteins. The results confirmed the efficacy of TTS against HeLa cells and that TTS can be used as an adjunct in cervical cancer prevention and treatment.